[Federal Register Volume 89, Number 76 (Thursday, April 18, 2024)]
[Rules and Regulations]
[Pages 28218-28485]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-06920]



[[Page 28217]]

Vol. 89

Thursday,

No. 76

April 18, 2024

Part III





Department of Labor





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Mine Safety and Health Administration





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30 CFR Parts 56, 57, 60, et al.





Lowering Miners' Exposure to Respirable Crystalline Silica and 
Improving Respiratory Protection; Final Rule

  Federal Register / Vol. 89 , No. 76 / Thursday, April 18, 2024 / 
Rules and Regulations  

[[Page 28218]]


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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Parts 56, 57, 60, 70, 71, 72, 75, and 90

[Docket No. MSHA-2023-0001]
RIN 1219-AB36


Lowering Miners' Exposure to Respirable Crystalline Silica and 
Improving Respiratory Protection

AGENCY: Mine Safety and Health Administration (MSHA), Department of 
Labor.

ACTION: Final rule.

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SUMMARY: The Mine Safety and Health Administration (MSHA) is amending 
its existing standards to better protect miners against occupational 
exposure to respirable crystalline silica, a significant health hazard, 
and to improve respiratory protection for miners from exposure to 
airborne contaminants. MSHA's final rule also includes other 
requirements to protect miner health, such as exposure sampling, 
corrective actions to be taken when a miner's exposure exceeds the 
permissible exposure limit, and medical surveillance for metal and 
nonmetal mines.

DATES: 
    Effective date: The final rule is effective June 17, 2024, except 
for amendments 21, 22, 25, 26, 27, 30, 31, 34, 35, 36, 38, 39, 42, 43, 
46, 47, 50, 51, 54, 55, 59, 60, 63, 64, 68, 69, 73, 74, 77, 78, 81, 82, 
83, 86, 87, 90, 91, 94, 95, 98, 99, 102, 103, 106, 107, 110, and 111, 
which are effective April 14, 2025, and amendments 4, 5, 8, 9, 13, 14, 
17, and 18, which are effective April 8, 2026.
    Incorporation by reference date: The incorporation by reference of 
certain materials listed in the rule is approved by the Director of the 
Federal Register beginning June 17, 2024, except for the material in 
amendment 60, which is approved beginning April 14, 2025, and the 
material in amendments 9 and 18, which is approved beginning April 8, 
2026. The incorporation by reference of certain other material listed 
in the rule was approved by the Director of the Federal Register as of 
July 10, 1995.
    Compliance dates: Compliance with this final rule is required April 
14, 2025 for coal mine operators and April 8, 2026 for metal and 
nonmetal mine operators.

FOR FURTHER INFORMATION CONTACT: S. Aromie Noe, Director, Office of 
Standards, Regulations, and Variances, MSHA, at: 
[email protected] (email); 202-693-9440 (voice); or 202-693-9441 
(facsimile). These are not toll-free numbers.

SUPPLEMENTARY INFORMATION: 
    The preamble to the final standard follows this outline:

I. Executive Summary
II. Pertinent Legal Authority
III. Regulatory History
IV. Background
V. Health Effects Summary
VI. Final Risk Analysis Summary
VII. Feasibility
VIII. Summary and Explanation of the Final Rule
IX. Summary of Final Regulatory Impact Analysis and Regulatory 
Alternatives
X. Final Regulatory Flexibility Analysis
XI. Paperwork Reduction Act
XII. Other Regulatory Considerations
XIII. References
XIV. Appendix

Acronyms and Abbreviations

COPD chronic obstructive pulmonary disease
ESRD end-stage renal disease
FEV forced expiratory volume
FRA final risk analysis
FRIA final regulatory impact analysis
FVC forced vital capacity
L/min liters per minute
mg milligram
mg/m\3\ milligrams per cubic meter
mL milliliter
[micro]g/m\3\ micrograms per cubic meter
MNM metal and nonmetal
MRE Mining Research Establishment
NMRD nonmalignant respiratory disease
PEL permissible exposure limit
PMF progressive massive fibrosis
PRA preliminary risk analysis
RCMD respirable coal mine dust
REL recommended exposure limit
SiO2 silica
TB tuberculosis
TLV[supreg] Threshold Limit Value
TWA time-weighted average

I. Executive Summary

A. Purpose of the Regulatory Action

    The purpose of this final rule is to reduce occupational disease in 
miners and to improve respiratory protection against airborne 
contaminants. The rule sets the permissible exposure limit (PEL) of 
respirable crystalline silica at 50 micrograms per cubic meter of air 
([micro]g/m\3\) for a full-shift exposure, calculated as an 8-hour time 
weighted average (TWA) for all mines. This rule also establishes an 
action level for respirable crystalline silica of 25 [micro]g/m\3\ for 
a full-shift exposure, calculated as an 8-hour TWA for all mines. In 
addition to the PEL and action level, the rule includes provisions for 
methods of compliance, exposure monitoring, corrective actions, 
respiratory protection, medical surveillance for metal and nonmetal 
(MNM) mines, and recordkeeping.
    The statutory authority for this rule is provided by the Mine Act 
under sections 101(a), 103(h), and 508. 30 U.S.C. 811(a), 813(h), and 
957. A full discussion of Mine Act legal requirements can be found in 
Section II. Pertinent Legal Authority. MSHA implements and administers 
the provisions of the Mine Act to prevent death, illness, and injury 
from mining and promote safe and healthful workplaces for miners.
    Respirable crystalline silica is classified by the International 
Agency for Research on Cancer (IARC) as a human carcinogen. 
Occupational exposure to respirable crystalline silica results in 
adverse health effects and increases risk of death. The adverse health 
effects include silicosis (i.e., acute silicosis, accelerated 
silicosis, chronic silicosis, and progressive massive fibrosis), 
nonmalignant respiratory diseases (e.g., emphysema and chronic 
bronchitis), lung cancer, and kidney disease. Each of these effects is 
chronic, irreversible, and potentially disabling or fatal. Occupational 
exposure to respirable crystalline silica at mines occurs most commonly 
from respirable dust generated during mining activities, such as 
cutting, sanding, drilling, crushing, grinding, sawing, scraping, 
jackhammering, excavating, and hauling of materials that contain 
silica.
    Existing standards pertaining to respirable crystalline silica for 
both MNM and coal mines have been in place since the early 1970s. For 
MNM mines, the existing standards, established by the Department of 
Interior, Bureau of Mines, in 1974, helped protect miners from the most 
dangerous levels of exposure to respirable crystalline silica. The 
existing MNM PELs for the three polymorphs of respirable crystalline 
silica are: 0.1 mg/m\3\ or 100 micrograms per cubic meter of air 
([micro]g/m\3\) for quartz; 0.05 mg/m\3\ or 50 [micro]g/m\3\ for 
cristobalite; and 0.05 mg/m\3\ or 50 [micro]g/m\3\ for tridymite. 
Existing standards for coal mines, first established by the Federal 
Coal Mine Health and Safety Act of 1969 as interim standards in 1970, 
control miners' exposures to respirable crystalline silica indirectly 
by reducing the respirable coal mine dust standard when quartz is 
present. The exposure limit for respirable crystalline silica during a 
coal miner's shift is 100 [micro]g/m\3\, reported as an equivalent 
concentration as measured by the Mining Research Establishment (MRE) 
instrument.
    However, since the promulgation of these existing standards, the 
National Institute for Occupational Safety and Health (NIOSH) has 
recommended a

[[Page 28219]]

lower respirable crystalline silica exposure level of 50 [micro]g/m\3\ 
for all workers, including miners. In 2016, the Occupational Safety and 
Health Administration (OSHA) established a PEL of 50 and an action 
level of 25 [micro]g/m\3\ as an 8-hour TWA in the general and 
construction industries and maritime sector that it regulates. In the 
mining industry, however, the higher PELs have remained in place for 
miners in both the MNM sector and the coal sector.
    To better protect miners' health, therefore, with this final rule 
MSHA is lowering its existing exposure limits for quartz or respirable 
crystalline silica to 50 [micro]g/m\3\ and setting an action level of 
25 [mu]g/m\3\ for all miners. As discussed in Section V. Health Effects 
Summary and Section VI. Final Risk Analysis Summary, lowering the PEL 
will substantially reduce health risks to miners. This final rule also 
provides a uniform, streamlined regulatory framework to ensure 
consistent protection across mining sectors and make compliance more 
straightforward. As discussed in Section VII. Feasibility and Section 
IX. Summary of Final Regulatory Impact Analysis and Regulatory 
Alternatives, compliance with the final rule is technologically and 
economically feasible, and the final rule has quantified benefits in 
terms of avoided deaths and illnesses that greatly outweigh the costs, 
as well as other important unquantified benefits.

B. Summary of Major Provisions

    MSHA amends its existing standards on respirable crystalline silica 
or quartz, after considering all the testimonies and written comments 
the Agency received from a variety of stakeholders, including miners, 
mine operators, labor unions, industry trade associations, government 
officials, and public health professionals, in response to its notice 
of proposed rulemaking. Below is a summary of major provisions in the 
final rule. Section VIII. Summary and Explanation of the Final Rule 
discusses each provision in the final rule.
    This final rule:
    1. Establishes a uniform permissible exposure limit (PEL) and 
action level for all mines. The rule sets a PEL for respirable 
crystalline silica at 50 micrograms per cubic meter of air ([micro]g/
m\3\) over a full shift, calculated as an 8-hour TWA and an action 
level at 25 [micro]g/m\3\ over a full shift, calculated as an 8-hour 
TWA for all mines.
    2. Requires exposure monitoring for respirable crystalline silica. 
Mine operators are required to conduct sampling to assess miners' 
exposures to respirable crystalline silica. Mine operators are also 
required to evaluate the impact of mining production, processes, 
equipment, engineering controls, and geological condition changes on 
respirable crystalline silica exposures.
    3. Updates the standard for respirable crystalline silica sampling. 
ISO 7708:1995(E), Air quality--Particle size fraction definitions for 
health-related sampling, First Edition, 1995-04-01 (ISO 7708:1995), is 
incorporated by reference. The final rule requires mine operators to 
conduct sampling for respirable crystalline silica using respirable 
particle size-selective samplers that conform to ISO 7708:1995, which 
is the international consensus standard that defines sampling 
conventions for particle size fractions used in assessing possible 
health effects of airborne particles in the workplace and ambient 
environment.
    4. Requires immediate reporting and corrective action to remedy 
overexposures. Whenever an overexposure is identified, mine operators 
must immediately report to MSHA and take corrective action to lower the 
concentration of respirable crystalline silica to at or below the PEL, 
resample to determine the efficacy of the corrective action taken, and 
make a record of all sampling and corrective actions that were taken.
    5. Specifies methods of controlling respirable crystalline silica. 
All mines are required to install, use, and maintain feasible 
engineering controls as the primary means of controlling respirable 
crystalline silica; administrative controls may be used, when 
necessary, as a supplementary control.
    6. Requires temporary use of respirators at metal and nonmetal 
mines when miners must work in concentrations above the PEL. When MNM 
miners must work in concentrations of respirable crystalline silica 
above the PEL while engineering controls are being developed and 
implemented or it is necessary by nature of the work involved, the mine 
operator shall use respiratory protection as a temporary measure.
    7. Updates the respiratory protection standard. ASTM F3387-19, 
Standard Practice for Respiratory Protection, approved August 1, 2019 
(ASTM F3387-19), is incorporated by reference. When approved 
respirators are used, the mine operator must have a written respiratory 
protection program to protect miners from airborne contaminants, 
including respirable crystalline silica, in accordance with ASTM 
requirements.
    8. Requires medical surveillance at MNM mines. Metal and nonmetal 
mine operators are required to provide to all miners, including those 
who are new to the mining industry, periodic medical examinations 
performed by a physician or other licensed health care professional 
(PLHCP) or specialist, at no cost to the miner. Like coal miners, MNM 
miners will be able to monitor their health and detect early signs of 
respiratory illness.
    The requirements in the new part 60 will take effect on June 17, 
2024. For coal mine operators, compliance with part 60 is required by 
12 months after the publication date; for MNM operators, compliance is 
required by 24 months after the publication date. The delayed 
compliance is to strike a balance between meeting the urgent need to 
protect miners from this health hazard and giving mining operators 
adequate preparation time to allow them to comply effectively with the 
new requirements.
    In addition, conforming amendments to parts 56, 57, 70, 71, 72, 75, 
and 90 will take effect on June 17, 2024. Compliance with conforming 
amendments to parts 56 and 57 is required by 24 months after the 
publication date; and compliance with conforming amendments to parts 
70, 71, 72, 75, and 90 is required by 12 months after the publication 
date.

C. Summary of Final Regulatory Impact Analysis

    MSHA's economic analysis estimates that the final rule would cost 
approximately an average of $89 million per year in 2022 dollars at an 
undiscounted rate, $90 million at a 3 percent discount rate, and $92 
million at a 7 percent discount rate. Based on the results of the Final 
Regulatory Impact Analysis (FRIA), MSHA estimates that this final 
rule's monetized benefits would exceed its costs, with or without 
discount rates. Monetized benefits are estimated from avoidance of 531 
deaths related to NMRD, silicosis, ESRD, and lung cancer and 1,836 
cases of silicosis associated with silica exposure over the first 60-
year period after the promulgation of the final rule. The estimated 
annualized net benefit is approximately $294 million at an undiscounted 
rate, $157 million at a 3 percent discount rate, and $40 million at a 7 
percent discount rate.
    A rule is significant under Executive Order 12866 Section 3(f)(1), 
as amended by E.O. 14094, if it is likely to result in ``an annual 
effect on the economy of $200 million or more.'' The Office of 
Management and Budget has determined that the final rule is significant 
under E.O. 12866 Section 3(f)(1).

[[Page 28220]]

    In summary, this final rule will strengthen MSHA's existing 
regulatory framework and improve health protections for the nation's 
miners. It establishes a uniform PEL that aligns respirable crystalline 
silica exposure limits for MNM and coal miners with workers in other 
industries. Moreover, the final rule updates the existing respiratory 
protection standard to require mine operators to provide miners with 
NIOSH-approved respiratory equipment that has been fitted, selected, 
maintained, and used in accordance with recent consensus standards. It 
also requires all MNM operators to provide medical surveillance in the 
form of a medical examination regime similar to the one that already 
covers coal miners. Cumulatively, the final rule will lower miners' 
risks of developing chronic, irreversible, disabling, and potentially 
fatal health conditions, consistent with MSHA's mission and statutory 
mandate to prevent occupational diseases and protect U.S. miners from 
suffering material health impairments.

II. Pertinent Legal Authority

    The statutory authority for this final rule is provided by the Mine 
Act under sections 101(a), 103(h), and 508. 30 U.S.C. 811(a), 813(h), 
and 957. MSHA implements the provisions of the Mine Act to prevent 
death, illness, and injury from mining and promote safe and healthful 
workplaces for miners. The Mine Act requires the Secretary of Labor 
(Secretary) to develop and promulgate improved mandatory health or 
safety standards to prevent hazardous and unhealthy conditions and 
protect the health and safety of the nation's miners. 30 U.S.C. 811(a).
    Congress passed the Mine Act to address these dangers, finding ``an 
urgent need to provide more effective means and measures for improving 
the working conditions and practices in the Nation's coal or other 
mines in order to prevent death and serious physical harm, and in order 
to prevent occupational diseases originating in such mines.'' 30 U.S.C. 
801(c). Congress concluded that ``the existence of unsafe and 
unhealthful conditions and practices in the Nation's coal or other 
mines is a serious impediment to the future growth of the coal or other 
mining industry and cannot be tolerated.'' 30 U.S.C. 801(d). 
Accordingly, ``the Mine Act evinces a clear bias in favor of miner 
health and safety.'' Nat'l Mining Ass'n v. Sec'y, U.S. Dep't of Lab., 
812 F.3d 843, 866 (11th Cir. 2016).
    Section 101(a) of the Mine Act gives the Secretary the authority to 
develop, promulgate, and revise mandatory health standards to address 
toxic materials or harmful physical agents. Under Section 101(a), a 
standard must protect lives and prevent injuries in mines and be 
``improved'' over any standard that it replaces or revises.
    The Secretary must set standards to assure, based on the best 
available evidence, that no miner will suffer material impairment of 
health or functional capacity from exposure to toxic materials or 
harmful physical agents over their working lives. 30 U.S.C. 
811(a)(6)(A). In developing standards that attain the ``highest degree 
of health and safety protection for the miner,'' the Mine Act requires 
that the Secretary consider the latest available scientific data in the 
field, the feasibility of the standards, and experience gained under 
the Mine Act and other health and safety laws. Id. As a result, courts 
have found it ``appropriate to `give an extreme degree of deference' '' 
to MSHA `` `when it is evaluating scientific data within its technical 
expertise.' '' Nat'l Mining Ass'n, 812 F.3d at 866 (quoting Kennecott 
Greens Creek Mining Co. v. MSHA, 476 F.3d 946, 954 (D.C. Cir. 2007)). 
Consequently, MSHA's ``duty to use the best evidence and to consider 
feasibility . . . cannot be wielded as counterweight to MSHA's 
overarching role to protect the life and health of workers in the 
mining industry.'' Nat'l Mining Ass'n, 812 F.3d at 866. Thus, ``when 
MSHA itself weighs the evidence before it, it does so in light of its 
congressional mandate'' in favor of protecting miners' health. Id. 
Moreover, ``the Mine Act does not contain the `significant risk' 
threshold requirement'' from the OSH Act. Nat'l Mining Ass'n v. United 
Steel Workers, 985 F.3d 1309, 1319 (11th Cir. 2021); see also Nat'l 
Min. Ass'n v. Mine Safety & Health Admin., 116 F.3d 520, 527-28 (D.C. 
Cir. 1997) (contrasting the Mine Act at 30 U.S.C. 811(a) with the OSH 
Act at 29 U.S.C. 652 and noting that ``[a]rguably, this language does 
not mandate the same risk-finding requirement as OSHA'' and holding 
that ``[a]t most, . . . [MSHA] was required to identify a significant 
risk associated with having no oxygen standard at all'').
    Section 103(h) of the Mine Act gives the Secretary the authority to 
promulgate standards involving recordkeeping and reporting. 30 U.S.C. 
813(h). Additionally, section 103(h) requires that every mine operator 
establish and maintain records, make reports, and provide this 
information as required by the Secretary. Id. Section 508 of the Mine 
Act gives the Secretary the authority to issue regulations to carry out 
any provision of the Mine Act. 30 U.S.C. 957.
    MSHA's final rule to lower the exposure limits for respirable 
crystalline silica adopts an integrated monitoring approach across all 
mining sectors and updates the existing respiratory protection 
requirements. The final rule fulfills Congress' direction to protect 
miners from material impairments of health or functional capacity 
caused by exposure to respirable crystalline silica and other airborne 
contaminants.

III. Regulatory History

    On August 29, 2019, MSHA published a Request for Information (RFI) 
in the Federal Register to solicit information and data on a variety of 
topics concerning silica (quartz) in respirable dust (84 FR 45452). In 
the RFI, MSHA requested data and information on technologically and 
economically feasible best practices to protect MNM and coal miners' 
health from exposure to quartz, including a lowered permissible 
exposure limit (PEL), new or developing protective technologies, and/or 
effective technical and educational assistance (84 FR 45456).
    Specifically, MSHA requested input from industry, labor, and other 
interested parties on the following four topics: (1) new or developing 
technologies and best practices that can be used to protect miners from 
exposure to quartz dust; (2) how engineering controls, administrative 
controls, and personal protective equipment can be used, either alone 
or concurrently, to protect miners from exposure to quartz dust; (3) 
additional feasible dust-control methods that could be used by mining 
operations to reduce miners' exposures to respirable quartz during 
high-silica cutting situations, such as on development sections, shaft 
and slope work, and cutting overcasts; and (4) any other experience, 
data, or information that may be useful to MSHA in evaluating miners' 
exposures to quartz (84 FR 45456).
    The Agency received 57 comments from citizens, labor, industry, and 
public health stakeholders in response to the RFI. Stakeholders 
expressed various and differing opinions on how and to what extent MSHA 
should address the protection of miners' health from exposure to 
silica. Many of these stakeholders also commented on MSHA's proposed 
rulemaking, summarized below.
    On June 30, 2023, MSHA made an informal copy of the proposed rule 
available on the Agency's website, prior to publication in the Federal 
Register, so the public and stakeholders could

[[Page 28221]]

review it in advance of the comment period.
    On July 13, 2023, MSHA published the proposed rule, Lowering 
Miners' Exposure to Respirable Crystalline Silica and Improving 
Respiratory Protection, in the Federal Register (88 FR 44852). The 
standalone documents ``Health Effects of Respirable Crystalline 
Silica,'' ``Preliminary Risk Analysis,'' and ``Preliminary Regulatory 
Impact Analysis'' were also made publicly available at that time. MSHA 
proposed to set the PEL of respirable crystalline silica at 50 
micrograms \1\ per cubic meter of air ([micro]g/m\3\) for a full-shift 
exposure, calculated as an 8-hour time-weighted average. MSHA's 
proposal included other requirements for sampling, qualitative 
evaluations, corrective actions, and medical surveillance for MNM 
mines. Finally, the proposal included requirements for respiratory 
protection, including the incorporation by reference of ASTM F3387-19 
Standard Practice for Respiratory Protection.
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    \1\ One microgram is equal to one-thousandth of a milligram (1 
milligram = 1000 micrograms).
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    On July 26, 2023, MSHA published a notice in the Federal Register 
scheduling three public hearings on the proposed rule (88 FR 48146). 
Hearings were held on: (1) August 3, 2023, in Arlington, Virginia; (2) 
August 10, 2023, in Beckley, West Virginia; and (3) August 21, 2023, in 
Denver, Colorado. Speakers and attendees could participate in-person or 
online. There were 14 speakers and over 150 attendees at the Arlington 
hearing; 24 speakers and over 200 attendees at the Beckley hearing; and 
10 speakers and over 175 attendees at the Denver hearing. Speakers 
included active and retired miners and representatives from the mining 
industry, unions, the health care profession, advocacy groups, industry 
groups, trade associations, and law firms. Transcripts from the public 
hearings are available at www.regulations.gov and on the MSHA website.
    On August 14, 2023, in response to requests from the public, MSHA 
published a notice in the Federal Register extending the comment period 
by changing the closing date from August 28, 2023, to September 11, 
2023 (88 FR 54961).
    During the comment period, MSHA received 157 written comments on 
the proposed rule from miners, mine operators, individuals, government 
officials, labor organizations, advocacy groups, industry groups, trade 
associations, and health organizations. Some commenters supported 
various aspects of the proposal. Other commenters opposed aspects of 
the proposal and offered recommendations for suggested changes to the 
proposed rule. All public comments and supporting documentation are 
available at www.regulations.gov and on the MSHA website. MSHA 
carefully reviewed and considered the written comments on the proposed 
rule and the speakers' testimonies from the hearings and addresses them 
in the relevant sections below.

IV. Background

A. Respirable Crystalline Silica Hazard and Mining

    Silica is a common component of rock composed of silicon and oxygen 
(chemical formula SiO2), existing in amorphous and 
crystalline states. Silica in the crystalline state is the focus of 
this rulemaking. Respirable crystalline silica consists of small 
particles of crystalline silica that can be inhaled and reach the 
alveolar region of the lungs, where they can accumulate and cause 
disease. In crystalline silica, the silicon and oxygen atoms are 
arranged in a three-dimensional repeating pattern. The crystallization 
pattern varies depending on the circumstances of crystallization, 
resulting in a polymorphic state, meaning several different structures 
with the same chemical composition. The most common form of crystalline 
silica found in nature is quartz, but cristobalite and tridymite also 
occur in limited circumstances. Quartz accounts for the overwhelming 
majority of naturally occurring crystalline silica. In fact, quartz 
accounts for almost 12 percent of the earth's crust by volume. All 
soils contain at least trace amounts of quartz, and it is present in 
varying amounts in almost every type of mineral. Quartz is also 
abundant in most rock types, including granites, sandstones, and shale. 
Moreover, quartz bands and veins are commonly found in limestone 
formations, although limestone itself does not contain quartz. Because 
of its abundance, crystalline silica in the form of quartz is present 
in nearly all mining operations.
    Cristobalite and tridymite are formed at very high temperatures and 
are associated with volcanic activity. Naturally occurring cristobalite 
and tridymite are rare, but they can be found in volcanic ash and in a 
relatively small number of rock types limited to specific geographic 
regions. Although rare, exposure to cristobalite can occur when 
volcanic deposits are mined. In addition, when other materials are 
mined, miners can potentially be exposed to cristobalite during certain 
processing steps (e.g., heating silica-containing materials) and 
contact with refractory materials (e.g., replacing fire bricks in mine 
processing facility furnaces). Tridymite is rarely found in nature and 
miner exposure to tridymite is much more infrequent.
    Most mining activities generate silica dust because silica is often 
contained in the ore being mined or in the overburden (i.e., the soil 
and surface material surrounding the commodity being mined). Such 
activities include, but are not limited to, cutting, sanding, drilling, 
crushing, grinding, sawing, scraping, jackhammering, excavating, and 
hauling materials that contain silica. These activities can generate 
respirable crystalline silica and therefore may lead to miner exposure.
    Inhaled small particles of silica dust can be deposited throughout 
the lungs. Because of their small size, many of these particles can 
reach and remain in the deep lung (i.e., alveolar region), although 
some can be cleared from the lungs. Because respirable crystalline 
silica particles are not water-soluble and do not undergo metabolism 
into less toxic compounds, those particles remaining in the lungs 
result in a variety of cellular responses that may lead to pulmonary 
diseases, such as silicosis and lung cancer. The respirable crystalline 
silica particles that are cleared from the lungs can be distributed to 
lymph nodes, blood, liver, spleen, and kidneys, potentially 
accumulating in those other organ systems and causing renal disease and 
other adverse health effects.
    In the U.S. in 2021, a total of 12,162 mines produced a variety of 
commodities. As shown in Table IV-1, of those 12,162 total mines, 
11,231 mines were MNM mines and 931 mines were coal mines. MNM mines 
can be broadly divided into five commodity groups: metal, nonmetal, 
stone, crushed limestone, and sand and gravel. These broad categories 
encompass approximately 98 different commodities.\2\ Table IV-1 shows 
that a majority of MNM mines produce sand and gravel, while the largest 
number of MNM miners work at metal mines, not including MNM contract 
workers (i.e.,

[[Page 28222]]

independent contractors and employees of independent contractors who 
are engaged in mining operations).
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    \2\ Commodities such as sand, gravel, silica, and/or stone are 
used in road building, concrete construction, the manufacture of 
glass and ceramics, molds for metal castings in foundries, abrasive 
blasting operations, plastics, rubber, paint, soaps, scouring 
cleansers, filters, hydraulic fracturing, and various architectural 
applications. Some commodities naturally contain high levels of 
crystalline silica, such as high-quartz industrial and construction 
sands and granite dimension stone and gravel (both produced for the 
construction industry).
[GRAPHIC] [TIFF OMITTED] TR18AP24.131

    The 931 coal mines--underground and surface--produce bituminous, 
subbituminous, anthracite, and lignite coal. Coal mining activities 
generate mixed coal mine dust that contains respirable silicates such 
as kaolinite, oxides such as quartz, and other components (IARC, 1997). 
These activities include the general mining activities previously 
mentioned (e.g., cutting, sanding, drilling, crushing, hauling, etc.), 
as well as roof bolter operations, continuous mining machine 
operations, longwall mining, and other activities. Table IV-1 shows 
that there are more surface coal mines than underground coal mines, but 
more miners are working in underground coal mines than surface coal 
mines (not including coal contract workers).

B. Existing Standards

    Since the early 1970s, MSHA has maintained health standards to 
protect MNM and coal miners from excessive exposure to airborne 
contaminants, including respirable crystalline silica. These standards 
require mine operators to use engineering controls as the primary means 
of suppressing, diluting, or diverting dust generated by mining 
activities. They also require mine operators to provide miners with 
respiratory protection in limited situations for a short period. The 
existing standards for MNM and coal mines differ in some respects, 
including exposure limits and monitoring requirements. This section 
describes MSHA's existing standards for respirable crystalline silica 
and presents respirable crystalline silica sampling data to show how 
MNM and coal mine operators have complied with the standards in recent 
years.
1. Existing Standards--Metal and Nonmetal Mines
    MSHA's existing standards for exposure to airborne contaminants in 
MNM mines, including respirable crystalline silica, are found in 30 CFR 
56 subpart D (Air Quality and Physical Agents) and 30 CFR 57 subpart D 
(Air Quality, Radiation, Physical Agents, and Diesel Particulate 
Matter). These standards include PELs for airborne contaminants 
(Sec. Sec.  56.5001 and 57.5001), exposure monitoring (Sec. Sec.  
56.5002 and 57.5002), and control of exposure to airborne contaminants 
(Sec. Sec.  56.5005 and 57.5005).
    Permissible Exposure Limits. The existing PELs for the three 
polymorphs of respirable crystalline silica are based on the 
TLVs[supreg] Threshold Limit Values for Chemical Substances in Workroom 
Air Adopted by the American Conference of Governmental Industrial 
Hygienists (ACGIH) for 1973, incorporated by reference in 30 CFR 
56.5001 and 57.5001 (ACGIH, 1974). The 1973 TLV[supreg] establishes 
limits for respirable dust containing 1 percent quartz or greater and 
is calculated in milligrams per cubic meter of air (mg/m\3\) for each 
respirable dust sample. The resulting TLVs[supreg] for respirable dust 
containing 1 percent respirable crystalline silica or greater are 
designed to limit exposures to less than 0.1 mg/m\3\ or 100 micrograms 
per cubic meter of air ([micro]g/m\3\) for quartz, to less than 0.05 
mg/m\3\ or 50 [micro]g/m\3\ for cristobalite, and to less than 0.05 mg/
m\3\ or 50 [micro]g/m\3\ for tridymite. Throughout the remainder of 
this preamble, the concentrations of respirable dust and respirable 
crystalline silica are expressed in [micro]g/m\3\.
    Exposure Monitoring. Under 30 CFR 56.5002 and 57.5002, MNM mine 
operators must conduct respirable dust ``surveys . . . as frequently as 
necessary to determine the adequacy of control measures.'' Mine 
operators can satisfy the survey requirement through various 
activities, such as respirable dust sampling and analysis, walk-through 
inspections, wipe sampling, examination of dust control system and 
ventilation system maintenance, and

[[Page 28223]]

review of information obtained from injury, illness, and accident 
reports.
    MSHA encourages MNM mine operators to conduct sampling for airborne 
contaminants to ensure a healthy and safe work environment for miners, 
because sampling provides more accurate information about miners' 
exposures and the effectiveness of existing controls in reducing 
exposures. When a mine operator's respirable dust survey indicates that 
miners have been overexposed to any airborne contaminant, including 
respirable crystalline silica, the operator is expected to adjust its 
control measures (e.g., exhaust ventilation) to reduce or eliminate the 
identified hazard. After doing so, the mine operator is expected to 
conduct additional surveys to determine whether its adjustments to 
control measures were successful. Re-surveying should be done as 
frequently as necessary to ensure that the sampling results comply with 
the PEL and the implemented control measures remain adequate.
    Exposure Controls. MSHA's existing standards for controlling a 
miner's exposure to harmful airborne contaminants in Sec. Sec.  56.5005 
and 57.5005 require, if feasible, prevention of contamination, removal 
by exhaust ventilation, or dilution with uncontaminated air. These 
requirements to use feasible engineering controls, supplemented by 
administrative controls, are consistent with widely accepted industrial 
hygiene principles and NIOSH's recommendations (NIOSH, 1974). 
Engineering controls designed to remove or reduce the hazard at the 
source are the most effective. Although administrative controls are 
considered a supplementary or secondary measure to engineering 
controls, mine operators may use administrative controls to further 
reduce miners' exposures to respirable crystalline silica and other 
airborne contaminants.
    The use of respiratory protective equipment is also allowed under 
specified circumstances, such as where engineering controls are not yet 
developed or when it is necessary due to the nature of the work--for 
example, while establishing controls or during occasional entry into 
hazardous atmospheres to perform maintenance or investigation. 
Respirators approved by NIOSH and suitable for their intended purpose 
must be provided by mine operators at no cost to the miner and must be 
used by miners to protect themselves against the health and safety 
hazards of respirable crystalline silica and other airborne 
contaminants. When respiratory protective equipment is used, MNM mine 
operators must implement a respiratory protection program consistent 
with the requirements of American National Standards Practices for 
Respiratory Protection ANSI Z88.2-1969 (ANSI Z88.2-1969).
2. Existing Standards--Coal Mines
    Under the existing coal mine standards, there is no separate 
standard for respirable crystalline silica. MSHA's existing standards 
for exposure to respirable quartz in coal mines, found in 30 CFR 70.101 
and 71.101, establish a respirable dust standard when quartz is present 
for underground and surface coal mines, respectively. Under 30 CFR part 
90 (Mandatory Health Standards--Coal Miners Who Have Evidence of the 
Development of Pneumoconiosis), Sec.  90.101 also sets the respirable 
dust standard when quartz is present for Part 90 miners.\3\ Coal 
miners' exposures to respirable quartz are indirectly regulated through 
reductions in the overall respirable dust standards.
---------------------------------------------------------------------------

    \3\ A ``Part 90 miner'' is defined in 30 CFR 90.3 as a miner 
employed at a coal mine who shows evidence of having contracted 
pneumoconiosis based on a chest X-ray or based on other medical 
examinations, and who is afforded the option to work in an area of a 
mine where the average concentration of respirable dust in the mine 
atmosphere during each shift to which that miner is exposed is 
continuously maintained at or below the applicable standard.
---------------------------------------------------------------------------

    Under its existing respirable coal mine dust standards, MSHA 
defines quartz as crystalline silicon dioxide (SiO2), which 
includes not only quartz but also two other polymorphs, cristobalite 
and tridymite.\4\ Therefore, the terms quartz and respirable 
crystalline silica are used interchangeably in the discussions of 
MSHA's existing standards for controlling exposures to respirable 
crystalline silica in coal mines.
---------------------------------------------------------------------------

    \4\ Quartz is defined in 30 CFR 70.2, 71.2, and 90.2 as 
crystalline silicon dioxide (SiO2) not chemically 
combined with other substances and having a distinctive physical 
structure. Crystalline silicon dioxide is most commonly found in 
nature as quartz but sometimes occurs as cristobalite or, rarely, as 
tridymite. Quartz accounts for the overwhelming majority of 
naturally occurring crystalline silica and is present in varying 
amounts in almost every type of mineral.
---------------------------------------------------------------------------

    Exposure Limits. The exposure limit for respirable crystalline 
silica during a coal miner's shift is 100 [micro]g/m\3\, reported as an 
equivalent concentration as measured by the Mining Research 
Establishment (MRE) instrument.\5\ The equivalent concentration of 
respirable crystalline silica must not be exceeded during the miner's 
entire shift, regardless of duration. When the equivalent concentration 
of respirable quartz exceeds 100 [micro]g/m\3\, under Sec. Sec.  
70.101, 71.101, and 90.101, MSHA imposes a reduced respirable dust 
standard designed to ensure that respirable quartz will not exceed 100 
[micro]g/m\3\. Various sections within a mine may have different 
reduced respirable coal mine dust (RCMD) exposure limits. Therefore, 
when a respirable dust sample collected by MSHA indicates that the 
average concentration of respirable quartz dust exceeds the exposure 
limit, the mine operator is required to comply with the applicable dust 
standard. Because respirable crystalline silica is a percentage of 
RCMD, by reducing the amount of respirable dust to which miners are 
exposed during their shifts, the miners' exposures to respirable 
crystalline silica are reduced to a level at or below the exposure 
limit of 100 [micro]g/m\3\.
---------------------------------------------------------------------------

    \5\ As defined in 30 CFR 70.2, an MRE instrument is a 
gravimetric dust sampler with a four channel horizontal elutriator 
developed by the Mining Research Establishment of the National Coal 
Board, London, England. MSHA inspectors use Dorr-Oliver 10-mm nylon 
cyclones operated at a 2.0 L/min flow rate (reported as MRE-
equivalent concentrations) for coal mine sampling.
---------------------------------------------------------------------------

    Exposure Monitoring. Under Sec. Sec.  70.208, 70.209, 71.206, and 
90.207, coal mine operators are required to sample for respirable dust 
on a quarterly basis for specified occupations and work areas. The 
occupations and work areas specified in the existing coal dust 
standards are the occupations and work areas at a coal mine that are 
expected to have the highest concentrations of respirable dust--
typically in locations where respirable dust is generated. Respirable 
dust sampling must be representative of respirable dust exposures 
during a normal production shift and must occur while miners are 
performing routine, day-to-day activities. Part 90 miners must be 
sampled for the air they breathe while performing their normal work 
duties, in their normal work locations, from the start of their work 
day to the end of their work day.
    Exposure Controls. Under Sec. Sec.  70.208, 70.209, 71.206, and 
90.207, coal mine operators are required to use engineering or 
environmental controls as the primary means of complying with the 
respirable dust standards. For many underground coal mines, providing 
adequate ventilation is the primary engineering control for respirable 
dust, ensuring that dust concentrations are continuously diluted with 
fresh air and exhausted away from miners.
    When a respirable dust sample exceeds the exposure limit of 100 
[micro]g/m\3\ for respirable quartz, the operator must reduce the 
average concentration of RCMD to a level designed to maintain the 
quartz level at or below 100 [micro]g/m\3\. If operators exceed the 
RCMD standard, they are required to take corrective

[[Page 28224]]

action to reduce exposure and comply with the reduced standard. 
Corrective actions that lower respirable coal mine dust, thus lowering 
respirable quartz exposures, are selected after evaluating the cause or 
causes of the overexposure.
    When taking corrective actions to reduce the exposure to respirable 
dust, coal mine operators must make approved respiratory equipment 
available to miners under Sec. Sec.  70.208, 70.209, and 71.206. 
Whenever respiratory protection is used, Sec.  72.700 requires coal 
mine operators to comply with requirements specified in ANSI Z88.2-
1969.

C. MSHA Inspection and Respirable Dust Sampling

    Under the existing standards, MSHA collects respirable dust samples 
at mines and analyzes them for respirable crystalline silica to 
determine whether the respirable crystalline silica exposure limits are 
exceeded and whether exposure controls are adequate. MSHA's inspection 
and respirable dust sampling were discussed in detail in the proposal 
(88 FR 44862). This section, for ease of reference, briefly summarizes 
the process for MSHA's inspection and respirable dust sampling.
1. Respirable Dust Sample Collection
    Under the existing standards, MSHA inspectors arrive at mines, 
determine which miners and which areas of the mine to select for 
respirable dust sampling, and place gravimetric samplers on the 
selected miners and at the selected locations. The gravimetric samplers 
capture air from the breathing zone of each selected miner and from 
each selected work area for the entire duration of the work shift. 
Full-shift sampling is used to minimize errors associated with 
fluctuations in airborne contaminant concentrations during the miners' 
work shifts and to avoid any speculation about the miners' exposures 
during unsampled periods of the work shift. Once sampling is completed, 
MSHA inspectors send cassettes containing the full-shift respirable 
dust samples to the MSHA Laboratory for analysis.
2. Respirable Dust Sample Analysis
    The MSHA Laboratory analyzes respirable dust samples following the 
standard operating procedures summarized below.\6\ Any samples that are 
broken, torn, or visibly wet are voided and removed before analysis. 
Samples are weighed and then examined for validity based on mass gain. 
All valid samples that meet the minimum mass gain criteria per the 
associated MSHA analytical method are then analyzed for respirable 
crystalline silica and for the compliance determination.\7\
---------------------------------------------------------------------------

    \6\ The MSHA Laboratory has fulfilled the requirements of the 
AIHA Laboratory Accreditation Programs (AIHA-LAP), LLC accreditation 
to the ISO/IEC 17025:2017 international standard for industrial 
hygiene.
    \7\ The minimum mass gain criteria used by the MSHA Laboratory 
for the different samples are:
     MNM mine respirable dust samples: greater than or equal 
to 0.100 mg;
     Underground coal mine respirable dust samples: greater 
than or equal to 0.100 mg; and
     Surface coal mine respirable dust samples: greater than 
or equal to 0.200 mg.
    Exception: For six surface occupations that have been deemed 
``high risk,'' the laboratory uses a minimum mass gain criterion of 
greater than or equal to 0.100 mg.
    If cristobalite analysis is requested for MNM mine respirable 
dust samples, filters having a mass gain of 0.05 mg or more are 
analyzed. In the rare instance when tridymite analysis is requested, 
a qualitative analysis for the presence of the polymorph is 
conducted concurrently with the cristobalite analysis.
---------------------------------------------------------------------------

    The MSHA Laboratory uses two analytical methods to determine the 
concentration of quartz (and cristobalite and tridymite, if requested) 
in respirable dust samples: X-ray diffraction (XRD) for samples from 
MNM mines and Fourier transform infrared spectroscopy (FTIR) for 
samples from coal mines.\8\ The percentage of silica in the MNM mine 
dust sample is calculated using the mass of quartz or cristobalite 
determined from the XRD analysis and the measured mass of respirable 
dust. Similarly, in the respirable coal mine dust sample, the 
percentage of quartz is calculated using the quartz mass determined 
from the FTIR analysis and the sample's mass of dust. Current FTIR 
methods, however, cannot quantify quartz and cristobalite, and/or 
tridymite, in the same sample.
---------------------------------------------------------------------------

    \8\ Details on MSHA's analytical procedures for respirable 
crystalline silica analysis can be found in ``MSHA P-2: X-Ray 
Diffraction Determination of Quartz and Cristobalite in Respirable 
Metal/Nonmetal Mine Dust'' and ``MSHA P-7: Determination of Quartz 
in Respirable Coal Mine Dust by Fourier Transform Infrared 
Spectroscopy.''
    Department of Labor, Mine Safety and Health Administration, 
Pittsburgh Safety and Health Technology Center, X-Ray Diffraction 
Determination of Quartz and Cristobalite in Respirable Metal/
Nonmetal Mine Dust. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P2.pdf (last accessed Jan. 10, 2024). Department of Labor, 
Mine Safety and Health Administration, Pittsburgh Safety and Health 
Technology Center, MSHA P-7: Determination of Quartz in Respirable 
Coal Mine Dust By Fourier Transform Infrared Spectroscopy. https://arlweb.msha.gov/Techsupp/pshtcweb/MSHA%20P7.pdf (last accessed Jan. 
10, 2024).
---------------------------------------------------------------------------

    MSHA calculates full-shift exposures to respirable crystalline 
silica (and other airborne contaminants) in the same way for MNM and 
coal miners when the miner works an 8-hour shift, but the calculated 
exposures differ for longer shifts. For work shifts that last longer 
than 8 hours, a coal miner's full-shift exposure is calculated using 
the entire duration of the coal miner's shift. For the MNM miner, by 
contrast, MSHA calculates extended full-shift exposure for respirable 
dust samples using 480 minutes (8 hours) as the sampling time, meaning 
that contaminants collected over extended shifts (e.g., 600-720 
minutes) are calculated as if they had been collected over 480 minutes.

D. Respirable Crystalline Silica Sampling Results--Metal and Nonmetal 
Mines

    MSHA's respirable crystalline silica sampling results for MNM mines 
were discussed in detail in the proposal (88 FR 44863). This section, 
for ease of reference, summarizes the results of respirable dust 
samples that were collected by MSHA inspectors at MNM mines from 2005 
to 2019. From January 1, 2005, to December 31, 2019, a total of 104,354 
valid samples were collected. Of this total, 57,769 samples met the 
minimum mass gain criteria and were analyzed for respirable crystalline 
silica. The vast majority of the 46,585 valid samples that were 
excluded from the analysis did not meet the mass gain criteria. Further 
information on the valid respirable dust samples that were excluded 
from the analysis can be found in Appendix A of the preamble.
1. Annual Results of MNM Respirable Crystalline Silica Samples
    Table IV-2 below shows the variation between 2005 and 2019 in: (1) 
the number of MNM respirable dust samples analyzed for respirable 
crystalline silica; and (2) the number and percentage of samples that 
had concentrations of respirable crystalline silica greater than 100 
[micro]g/m\3\. Of the 57,769 MNM respirable dust samples analyzed for 
respirable crystalline silica over the 15-year period, about 6 percent 
(3,539 samples) had respirable crystalline silica concentrations 
exceeding the existing PEL of 100 [micro]g/m\3\. The average annual 
rates of overexposure ranged from a maximum of approximately 10 percent 
in 2006 (the second year) to a minimum of approximately 4 percent in 
2019 (the last year of the time series). Compared with the rates in 
2005-2008, overexposure rates were substantially lower in 2009-2017, 
with a further drop in 2018-19.
BILLING CODE 4520-43-P

[[Page 28225]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.132

BILLING CODE 4520-43-C
2. Analysis of MNM Respirable Crystalline Silica Samples by Commodity
    Because the MNM mining industry produces commodities that contain 
varying degrees of respirable crystalline silica, it is important to 
examine each commodity separately. MNM mines can be grouped by five 
commodities: metal, sand and gravel, stone, crushed limestone, and 
nonmetal (where nonmetal includes all other materials that are not 
metals, besides sand, gravel, stone, and limestone). This grouping is 
based on the mine operator-reported mining products and the North 
American Industry Classification System (NAICS) codes. (Appendix B of 
the preamble provides a list of the NAICS codes relevant for MNM mining 
and how each code is assigned to one of the five commodities.)
    Table IV-3 shows the distribution of the respirable dust samples 
analyzed for respirable crystalline silica by mine commodity. The 
percentage of samples with respirable crystalline silica concentrations 
greater than the existing exposure limit of 100 [micro]g/m\3\ varies 
across the different commodities. It is highest for the metal, sand and 
gravel, and stone commodities (at approximately 11, 7, and 7 percent, 
respectively), and lowest for the nonmetal and crushed limestone 
commodities (at approximately 4 and 3 percent, respectively).

[[Page 28226]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.133

3. Analysis of MNM Respirable Crystalline Silica Samples by Occupation
    To examine how miners who perform different tasks differ in 
occupational exposure to respirable crystalline silica, MSHA grouped 
MNM mining jobs into 11 occupational categories. These categories 
include jobs that are similar in terms of tasks performed, equipment 
used, and engineering or administrative controls used to control 
miners' exposure. For example, backhoe operators, bulldozer operators, 
and tractor operators were grouped into ``operators of large powered 
haulage equipment,'' whereas belt crew, belt cleaners, and belt 
vulcanizers were grouped into ``conveyer operators.'' The 121 MNM job 
codes used by MSHA inspectors were grouped into the following 
occupational categories: \9\
---------------------------------------------------------------------------

    \9\ For a full crosswalk of job codes included in each of these 
11 Occupational Categories, please see Appendix C of the preamble. 
Also, note that the order of the presentation of the 11 Occupational 
Categories here follows the general sequence of mining activities: 
first development and production, then ore/mineral processing, then 
loading, hauling, and dumping, and finally all others.
---------------------------------------------------------------------------

    (1) Drillers (e.g., Diamond Drill Operator, Wagon Drill Operator, 
and Drill Helper),
    (2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting 
Machine Operator, and Cutting Machine Helper),
    (3) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill Operator, 
Leaching Operator, and Pelletizer Operator),
    (4) Crushing Equipment and Plant Operators (e.g., Crusher Operator/
Worker, Scalper Screen Operator, and Dry Screen Plant Operator),
    (5) Packaging Equipment Operators (e.g., Bagging Operator and 
Packaging Operations Worker),
    (6) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt 
Vulcanizer),
    (7) Truck Loading Station Tenders (e.g., Dump Operator and Truck 
Loader),
    (8) Operators of Large Powered Haulage Equipment (e.g., Tractor 
Operators, Bulldozer Operator, and Backhoe Operators),
    (9) Operators of Small Powered Haulage Equipment (e.g., Bobcat 
Operator, Scoop-Tram Operator, and Forklift Operator),
    (10) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and 
Supervisors), and
    (11) Miners in Other Occupations (e.g., Welder, Dragline Operator, 
Ventilation Crew and Dredge/Barge Operator).
    Table IV-4 shows sample numbers and overexposure rates by MNM 
occupation. Operators of large powered haulage equipment accounted for 
the largest number of samples analyzed for silica (17,016 samples), 
whereas conveyor operators accounted for the fewest (215 samples). 
Table IV-4 also shows the number and percentage of the samples 
exceeding the existing respirable crystalline silica PEL of 100 
[micro]g/m\3\. In every occupational category, some MNM miners were 
exposed to respirable crystalline silica levels above the existing PEL. 
In 9 out of the 11 occupational categories, the percentage of samples 
exceeding the existing PEL is less than 10 percent, although two have 
higher rates, ranging up to more than 19 percent (in the case of stone 
cutting operators).
BILLING CODE 4520-43-P

[[Page 28227]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.134

BILLING CODE 4520-43-C
4. Conclusion
    This analysis of MSHA inspector sampling data shows that MNM 
operators have generally met the existing standard. Of the 57,769 
respirable dust samples from MNM mines, approximately 6 percent 
exceeded the existing respirable crystalline silica PEL of 100 
[micro]g/m\3\, although there are several outliers with much higher 
overexposures. For 9 of the 11 occupational categories, less than 10 
percent of the respirable dust samples had concentrations over the 
existing PEL of 100 [micro]g/m\3\ for respirable crystalline silica. 
While stone-cutting operators have historically had high exposures to 
respirable dust and respirable crystalline silica \10\ and continue to 
experience the highest overexposures of any MNM occupation, about 80 
percent of samples taken from stone cutting operators did not exceed 
the existing PEL. For the categories of drillers, miners in other 
occupations, and operators of large powered haulage equipment, 
approximately 5 percent or less of the respirable dust samples showed 
concentrations over the existing exposure limit.
---------------------------------------------------------------------------

    \10\ Analysis of MSHA respirable dust samples from 2005 to 2010 
showed that stone and rock saw operators had approximately 20 
percent of the sampled exposures exceeding the PEL. Watts et al. 
(2012).
---------------------------------------------------------------------------

    In summary, the analysis of MSHA inspector sampling data indicates 
that the controls that MNM mine operators are using, together with 
MSHA's enforcement, have generally been effective in keeping miners' 
exposures at or below the existing limit of 100 [micro]g/m\3\.

E. Respirable Crystalline Silica Sampling Results--Coal Mines

    MSHA's respirable crystalline silica sampling results for coal 
mines were discussed in detail in the proposal (88 FR 44866). This 
section, for ease of reference, summarizes the results of RCMD samples 
collected by MSHA inspectors from 2016 to 2021. (The data analyses for 
this rulemaking do not include any respirable dust samples collected by 
coal mine operators.) The analysis below is based on the samples 
collected by MSHA inspectors starting on August 1, 2016, when Phase III 
of MSHA's 2014 Lowering Miners' Exposure to Respirable Coal Mine Dust, 
Including Continuous Personal Dust Monitors (referred to throughout the 
preamble as the 2014 RCMD Standard) (79 FR 24813) went into effect. At 
that time, the exposure limits for RCMD were lowered from 2.0 mg/m\3\ 
to 1.5 mg/m\3\ (MRE equivalent) at underground and surface coal mines, 
and from 1.0 mg/m\3\ to 0.5 mg/m\3\ (MRE equivalent) for intake air at 
underground coal mines and for Part 90 miners. From August 1, 2016, to 
July 31, 2021, MSHA inspectors collected a total of 113,607 valid RCMD 
samples. Of the valid samples, only those collected from the breathing 
zones of miners were used in the analysis for this rulemaking; no 
environmental dust

[[Page 28228]]

samples were included.\11\ Of the valid breathing zone samples, there 
were 63,127 samples that met the minimum mass gain criteria and were 
analyzed for respirable quartz. The majority of the non-environmental 
valid samples excluded from this rulemaking analysis were excluded due 
to insufficient mass. Further information on the valid respirable dust 
samples that are not included in the rulemaking analysis can be found 
in Appendix A of the preamble.
---------------------------------------------------------------------------

    \11\ Environmental samples were not included in the analysis to 
be consistent with the proposed sampling requirements to determine 
individual miner exposure.
---------------------------------------------------------------------------

    Of the 63,127 valid samples analyzed for respirable crystalline 
silica and used for this analysis, about 1 percent (777 samples) were 
over the existing quartz exposure limit of 100 [micro]g/m\3\ (MRE 
equivalent) for a full shift, calculated as a TWA.\12\ Overexposure 
rates decreased by nearly a quarter between the first half and the 
second half of the 2016-2021 period. As in MNM mines, different miner 
occupations had different overexposure rates. Using broader groupings, 
surface mines experienced higher rates of overexposure than underground 
mines (2.4 percent versus 1.0 percent, respectively).
---------------------------------------------------------------------------

    \12\ The conversion between ISO values and MRE values uses the 
NIOSH conversion factor of 0.857. In the 1995b Criteria Document, 
NIOSH presented an empirically derived conversion factor of 0.857 
for comparing current (MRE) and recommended (ISO) respirable dust 
sampling criteria using the 10 mm Dorr-Oliver nylon cyclone operated 
at 2.0 and 1.7 L/min, respectively (i.e., 1.5 mg/m\3\ BMRC-MRE = 
1.29 mg/m\3\ ISO).
---------------------------------------------------------------------------

1. Annual Results of Coal Respirable Crystalline Silica Samples
    In examining trends from one year to the next, the discussion below 
focuses on the samples collected in the 6 calendar years from 2016 to 
2021. The number of samples per year was stable from 2017 to 2019 
before decreasing in 2020.\13\ The overexposure rate decreased across 
the entire 2016 to 2021 period, from 1.41 percent in 2016 to 0.95 
percent in 2021. As shown in Table IV-5, a review of the 6 calendar 
years reveals that the overexposure rate decreased by nearly a quarter 
from 2016-2018 (1.38 percent) to 2019-2021 (1.07 percent).
---------------------------------------------------------------------------

    \13\ The coal samples for 2016 begin in August of that year and 
the coal samples for 2021 end in July of that year.
[GRAPHIC] [TIFF OMITTED] TR18AP24.135

2. Analysis of Coal Respirable Crystalline Silica Samples by Location
    Coal mining activities differ depending on the characteristics and 
locations of coal seams. When coal seams are several hundred feet below 
the surface, miners tunnel into the earth and use underground mining 
equipment to extract coal, whereas miners at surface coal mines remove 
topsoil and layers of rock to expose coal seams. Due to these 
differences, it is important to examine the respirable crystalline 
silica data by location to determine how underground and surface coal 
miners differ in occupational exposure to respirable crystalline 
silica.
    Table IV-6, which presents the overexposure rate by type of mine 
where respirable coal mine dust samples were collected, shows that 
samples from surface coal mines reflected higher rates of overexposure 
than samples from underground mines. Out of the 53,095 respirable coal 
mine dust samples from underground mines, 1 percent (537 samples) were 
over the existing exposure limit. By contrast, there were 10,032 
samples from surface coal mines, and approximately 2.4 percent (240 
samples) of those samples were over the existing exposure limit.

[[Page 28229]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.136

3. Analysis of Coal Respirable Crystalline Silica Samples by Occupation
    To assess the exposure to respirable crystalline silica of miners 
in different occupations, MSHA has consolidated the 220 job codes for 
coal mines into 9 occupational categories (using a similar process to 
the one it used for the MNM mines, but with different job codes and 
categories). For the coal mine occupational categories,\14\ a 
distinction is made between occupations based on whether the job tasks 
are being performed at the surface of a mine or underground. For 
example, bulldozer operators are assigned to the job category of 
operators of large powered haulage equipment grouping and then sorted 
into separate occupational categories based on whether they are working 
at the surface of a mine or underground.
---------------------------------------------------------------------------

    \14\ For a full crosswalk of which job codes were included in 
each of these nine Occupational Categories, please see Appendix C of 
the preamble.
---------------------------------------------------------------------------

    Of the nine occupational categories used for coal miners, the five 
underground categories are:
    (1) Continuous Mining Machine Operators (e.g., Coal Drill Helper 
and Coal Drill Operator),
    (2) Longwall Workers (e.g., Headgate Operator and Jack Setter 
(Longwall)),
    (3) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper),
    (4) Operators of Large Powered Haulage Equipment (e.g., Shuttle Car 
Operator, Tractor Operator/Motorman, Scoop Car Operator), and
    (5) All Other Underground Miners (e.g., Electrician, Mechanic, Belt 
Cleaner and Laborer, etc.).
    The four surface occupational categories are:
    (1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and 
Auger Operator),
    (2) Crusher Operators (e.g., Crusher Attendant, Washer Operator, 
and Scalper-Screen Operator),
    (3) Operators of Large Powered Haulage Equipment (e.g., Backhoe 
Operator, Forklift Operator, and Bulldozer Operator), and
    (4) Mobile Workers (e.g., Electrician, Mechanic, Blaster, Laborer, 
etc.).
    The most sampled occupational category was operators of large 
powered haulage equipment (underground), representing approximately 34 
percent of the samples taken. The least sampled occupational category 
was crusher operators (surface), consisting of 1 percent of the samples 
taken. Table IV-7 displays the number and percent of respirable coal 
mine dust samples with quartz greater than the existing exposure limit 
for each occupational category.

[[Page 28230]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.137

    Looking at trends, every occupational category shows a decrease in 
overexposure rates over time. See Figure IV-1. Most of the nine 
categories had lower rates of overexposure in the 2019-2021 period than 
in the 2016-2018 period.

Figure IV-1: Percent of RCMD Samples With Respirable Crystalline Silica 
Concentration Greater Than 100 MRE [micro]g/m\3\ (MRE) by Occupational 
Category *

[[Page 28231]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.076

    * For Crusher Operators (Surface), only one sample with a quartz 
concentration greater than 100 [micro]g/m\3\ MRE occurred (in 2018); 
and for Mobile Workers (Surface), only nine samples with a quartz 
concentration greater than 100 [micro]g/m\3\ MRE occurred (three in 
2017, five in 2018 and one in 2021). Source: MSHA MSIS respirable 
crystalline silica data for the Coal Industry, August 1, 2016, 
through July 31, 2021 (version 20220617).

    In all occupational categories, coal miners were sometimes exposed 
to respirable crystalline silica levels above the existing exposure 
limit. But the sampling data showed that coal mine operators can 
generally comply with the existing exposure limit. For example, 
although mining tasks performed by the occupational category of roof 
bolters (underground) historically resulted in high levels of 
overexposure to quartz, the low levels of overexposure for that 
occupation in 2016-2021 (i.e., 1 percent) suggest that roof bolters now 
benefit from the improved respirable dust standard, improved 
technology, and better training.\15\ Over the 2016-2021 period, coal 
miners in the occupational category drillers (surface) were the most 
frequently overexposed, with approximately 6 percent of samples over 
the existing quartz limit; they were followed by longwall workers 
(underground) (about 4 percent), operators of large powered haulage 
equipment (surface) (about 3 percent), and continuous mining machine 
operators (underground) (about 2 percent). For all other occupational 
categories, the overexposure rate was less than 1 percent.
---------------------------------------------------------------------------

    \15\ The drilling operation in the roof bolting process, 
especially in hard rock, generates excessive respirable coal and 
quartz dusts, which could expose the roof bolting operator to 
continued health risks (Jiang and Luo, 2021).
---------------------------------------------------------------------------

4. Conclusion
    This analysis of MSHA inspector sampling data shows that coal mine 
operators generally comply with the existing standards related to 
quartz. Of the 63,127 valid respirable dust samples from coal mines 
over the most recent 5-year period, 1.2 percent had respirable quartz 
over the existing exposure limit of 100 [micro]g/m\3\ (MRE equivalent) 
for a full-shift exposure, calculated as a TWA. Seven of the nine 
occupational categories had overexposure rates of 2.5 percent or less. 
Roof bolters (underground), which historically have had high exposures 
to respirable dust and respirable crystalline silica, had overexposure 
rates of 1 percent over this recent period. The data demonstrates that 
the controls that coal mine operators are using, together with MSHA's 
enforcement, have generally been effective in keeping miners' exposure 
to respirable crystalline silica at or below the existing exposure 
limit.

V. Health Effects Summary

    This section summarizes the health effects from occupational 
exposure to respirable crystalline silica. MSHA's full analysis of the 
health effects literature is contained in the standalone document, 
entitled ``Effects of Occupational Exposure to Respirable Crystalline 
Silica on the Health of Miners'' (referred to as the standalone Health 
Effects document throughout the preamble), which is placed in the 
rulemaking docket for the MSHA silica rulemaking (RIN 1219-AB36, Docket 
No. MSHA-2023-0001). MSHA reviewed a wide range of health effects 
literature that included more than 600 studies exploring the 
relationship between respirable crystalline silica exposure and 
resultant health effects in miners and other workers across various 
industries. The purpose of this summary is to briefly present MSHA's 
findings on the nature of the hazards of exposure to respirable 
crystalline silica. Based on its review of the health effects 
literature and the weight-of-evidence approach, MSHA makes the 
following conclusions:
    1. Miners in MNM and coal mines exposed to respirable crystalline 
silica at MSHA's existing exposure limits are subject to material 
impairment of health or functional capacity. The illnesses associated 
with exposure to respirable crystalline silica develop independent of 
other exposures.
    2. Occupational exposure to respirable crystalline silica (as 
quartz and/or cristobalite) causes silicosis,

[[Page 28232]]

nonmalignant respiratory disease (NMRD) (e.g., emphysema and chronic 
bronchitis), lung cancer, and renal disease. Each of these health 
effects outcomes is exposure-dependent, potentially chronic, 
irreversible, potentially disabling, and can be fatal.
    3. Exposure to respirable crystalline silica contributes to the 
development of autoimmune disorders through inflammatory pathways.
    4. The development of silicosis, NMRD, lung cancer, renal disease, 
and autoimmune disorders is largely dependent upon cumulative 
respirable crystalline silica exposure.
    These conclusions are the basis of MSHA's Final Risk Analysis (FRA) 
on miners' exposure to respirable crystalline silica. In the FRA, MSHA 
quantifies risks associated with the five specific health outcomes 
mentioned above. The FRA summary is presented in Section VI. Final Risk 
Analysis Summary and a standalone document, entitled ``Final Risk 
Analysis'' (referred to as the standalone FRA document throughout the 
preamble), has been placed in the rulemaking docket for the MSHA silica 
rulemaking (RIN 1219-AB36, Docket No. MSHA-2023-0001).
    From its health effects literature review and FRA, MSHA determines 
that miners exposed to respirable crystalline silica continue to face a 
risk of material impairment of health or functional capacity under 
MSHA's existing exposure limits. Thus, MSHA also makes the following 
conclusions:
    (1) The rate of silicosis and other diseases caused by respirable 
crystalline silica exposure would decrease with reduction in 
occupational exposures, which is the most effective way to prevent 
these types of diseases.
    (2) Regulatory action is necessary to reduce these occupational 
exposures and protect miners' health. Section 101(a)(6)(A) of the 
Federal Mine Safety and Health Act of 1977, as amended (Mine Act), 
requires MSHA to ``set standards which most adequately assure on the 
basis of the best available evidence that no miner will suffer material 
impairment of health or functional capacity even if such miner has 
regular exposure to the hazards dealt with by such standard for the 
period of his working life.'' 30 U.S.C. 811(a)(6)(A).
    Regulatory action to protect miners' health is required by section 
101(a)(6)(A) of the Mine Act, and MSHA's statutory authority and 
mission has been recognized and upheld by reviewing courts. ``[T]he 
Mine Act evinces a clear bias in favor of miner health and safety.'' 
Nat'l Min. Ass'n v. Sec'y, U.S. Dep't of Lab., 812 F.3d 843, 866 (11th 
Cir. 2016). Courts interpret MSHA's obligation to promulgate standards 
to protect the health of the nation's miners to include `` 
`prevent[ing],' not merely reduc[ing] the incidence of, `occupational 
diseases originating in . . . mines.' '' Id. at 883 (quoting 30 U.S.C. 
801(c)). Where occupational disease ``incidence has not been reduced to 
zero . . . MSHA has not completely fulfilled its mission to `protect 
the health . . . of the Nation's coal or other miners.' '' Id. (quoting 
30 U.S.C. 801(g)). Case law instructs that MSHA must demonstrate risk 
before regulating: ``[B]efore promulgating a health or safety standard 
under the Mine Act, MSHA must show that the substance being regulated 
presents a risk of `material impairment of health or functional 
capacity' for miners who are regularly exposed to the substance.'' 
Kennecott Greens Creek Min. Co. v. Mine Safety & Health Admin., 476 
F.3d 946, 952 (D.C. Cir. 2007) (quoting 30 U.S.C. 811(a)(6)(A)). 
Although the Mine Act requires MSHA to consider the best available 
evidence, the ``duty to use the best available evidence . . . cannot be 
wielded as a counterweight to MSHA's overarching role to protect the 
life and health of workers in the mining industry.'' Nat'l Min. Ass'n, 
812 F.3d at 866. With this regulatory action, MSHA is addressing this 
urgent need. See 30 U.S.C. 801(c).
    On July 13, 2023, MSHA published a notice of proposed rulemaking, 
entitled ``Lowering Miners' Exposure to Respirable Crystalline Silica 
and Improving Respiratory Protection'', along with supplemental 
documents. The Agency specifically sought comments on its preliminary 
determination from the literature review that miners' exposure to 
respirable crystalline silica presents a risk of material health 
impairment or functional capacity. MSHA also requested input on any 
additional adverse health effects that should be included or more 
recent literature that offers a different perspective. MSHA received 
numerous comments in response to this request and considered them in 
preparing the final standalone Health Effects document and the final 
rule.
    This section will describe how MSHA conducted its review of the 
health effects literature on respirable crystalline silica and what the 
Agency has found about the toxicity of respirable crystalline silica. 
This section will also present the findings on the following health 
effects: (1) Silicosis; (2) Non-malignant respiratory disease (NMRD), 
excluding silicosis; (3) Lung cancer and cancer at other sites; (4) 
Renal disease; and (5) Autoimmune diseases. Public comments received 
are reflected throughout this section.

A. General Approach to Health Effects Literature Review

    MSHA reviewed a wide range of health effects literature totaling 
over 600 studies that explore the relationship between respirable 
crystalline silica exposure and resultant adverse health effects in 
miners and other workers across various industries. The health effects 
literature reviewed by MSHA included both studies reviewed by OSHA for 
its 2016 respirable crystalline silica standard and many other newer 
studies and studies that focused specifically on the mining industry.
    OSHA's ``Health Effects Analysis and Preliminary Quantitative Risk 
Assessment'' (2013b) included studies that were identified from 
previously published scientific reviews, such as the IARC (1997) and 
NIOSH (2002), and from newer evaluations of scientific literature, 
literature searches, and contact with experts and stakeholders. That 
document underwent extensive peer review by a panel of nationally 
recognized experts in occupational epidemiology, biostatistics and risk 
assessment, animal and cellular toxicology, and occupational medicine 
who had no conflict of interest (COI) or apparent bias in performing 
the review. These experts were asked to consider the strengths, 
weaknesses, interpretations, and inclusion of studies used to support 
the findings, and OSHA revised the document based on their feedback.
    To ensure that its literature review was thorough and up to date, 
MSHA reviewed a large body of additional evidence beyond the studies 
considered by OSHA. It added many studies focused on miners' exposures 
to respirable crystalline silica, as well as newer studies published 
over the past decade. MSHA drew upon numerous studies conducted by 
NIOSH, the International Agency for Research on Cancer (IARC), the 
National Toxicology Program (NTP), and other researchers. These studies 
provided epidemiological data, analyses of morbidity (having a disease 
or a symptom of disease) and mortality (disease resulting in death), 
progression and pathology evaluations, death certificate and autopsy 
reviews, medical surveillance data, health hazard assessments, in vivo 
(animal) and in vitro (cell-based) toxicity data, and other 
toxicological reviews. These studies are cited throughout this summary 
and are listed in the References section of MSHA's standalone Health 
Effects

[[Page 28233]]

document. Additionally, these studies appear in the rulemaking docket.
    MSHA received some comments from industry stakeholders who 
disagreed with MSHA's selection of studies for its literature review 
and therefore with its findings. The Nevada Mining Association (NVMA) 
and the Sorptive Minerals Institute (SMI) stated that not all relevant 
studies were discussed in the Health Effects literature review 
(Document ID 1441; 1446). NVMA also stated that the studies referenced 
are outdated. The National Stone, Sand, & Gravel Association (NSSGA) 
stated that MSHA's review is overly reliant on OSHA's review (2013b) 
(Document ID 1448, Attachment 3). The state mining association stated 
that the studies MSHA considered do not recognize that the likelihood 
of prolonged exposure to respirable crystalline silica has been 
dramatically reduced over the years, noting improvements to 
respirators, equipment, and engineering controls (Document ID 1441).
    However, commenters from health and labor organizations stated that 
MSHA's review was thorough, was consistent with the scientific 
consensus, and addressed the primary health effects of concern. These 
commenters agreed with MSHA's findings and conclusions related to 
health risks from exposure to respirable crystalline silica (Document 
ID 1398; 1405; 1410; 1416). The American Public Health Association 
(APHA) also noted the inclusion of several recent peer-reviewed 
publications included in MSHA's review (Document ID 1416). The American 
College of Occupational and Environmental Medicine (ACOEM) commented 
that there has been an explosion of new information about the molecular 
basis for silica's adverse effects since OSHA's comprehensive summary 
of the medical literature in its preamble to the 2016 revisions to the 
silica standard (Document ID 1405). This commenter stressed that this 
new information only adds to the urgency of establishing and enforcing 
MSHA's proposed standard and applauded the Agency's review of the 
medical and epidemiologic literature on the health effects of silica 
exposure.
    MSHA has taken several steps to ensure that its review of health 
effects literature represents the current understanding of health risks 
related to exposures to respirable crystalline silica. In its initial 
standalone Health Effects document, which was published alongside the 
proposed rule, MSHA included several recent publications (published as 
late as 2022), and since then, it has added more recent publications 
(through 2023) in its final standalone Health Effects document. 
Examples of recent literature included in the standalone Health Effects 
document are: Carrington and Hershberger (2022), Cohen et al. (2022), 
Descatha et al. (2022), Hall et al. (2022), and Keles et al. (2022). 
Furthermore, many of the more recent studies included miners regulated 
under the existing MSHA PEL of 100 [micro]g/m\3\ (e.g., Almberg et al., 
2017, 2018a; Graber et al., 2017; Blackley et al., 2018a; Cohen et al., 
2022). In response to the comment that the initial standalone Health 
Effects document did not take into account improved mining conditions 
or contemporary engineering controls, the Agency notes that it 
considered several studies featuring miners in a larger range of 
exposure groups, including some that had lower exposure levels (e.g., 
Mannetje et al., 2002b; Park et al., 2002; Buchanan et al., 2003; 
Attfield and Costello, 2004; Chen et al., 2012).
    Two commenters (an industry trade association and a training 
consulting company) stated that MSHA presented a significant amount of 
data showing the consequences of the various chronic health effects 
that silica can and does have on the human body but no viable data on 
mortality and morbidity among MNM miners (Document ID 1442; 1392).
    As discussed elsewhere, MSHA is not required to prove a risk of 
death due to silica exposure to justify regulating to reduce a silica 
health risk. But the evidence shows that respirable silica exposure 
causes death as well as chronic disease. MSHA reviewed and discussed 
multiple studies that reported an increase in mortality rates 
throughout the standalone Health Effects document (e.g., Bang et al., 
2005; Mazurek and Wood, 2008a; Liu et al., 2017a; Wang et al., 2020a). 
Examples of MNM morbidity studies included are Mamuya et al. (2007), 
Tse et al. (2007a), Rego et al. (2008), Reynolds et al. (2016), and 
Wang et al. (2020b); while MNM specific mortality studies include 
Attfield and Costello (2004), Chen et al. (2005, 2012), Schubauer-
Berigan et al. (2009), and Vacek et al. (2011), among others. MSHA 
considered the best available evidence for MNM and concludes that MNM 
miners have an increased mortality and morbidity due to exposure to 
respirable crystalline silica.
    Commenters from health and labor organizations suggested additional 
studies for MSHA to include in the final standalone Health Effects 
document (Document ID 1405; 1373; 1449). These studies included topics 
such as new information regarding the molecular basis for silica's 
adverse health effects or related to engineered stone workers. One 
commenter stated that MSHA should include studies from outside of the 
mining industry (Document ID 1448, Attachment 3).
    MSHA thoroughly reviewed these studies and did not find sufficient 
evidence to alter MSHA's overall conclusions of health risk, as 
discussed in detail in the sections that follow. However, MSHA did add 
many of the recommended studies to its final standalone Health Effects 
document (e.g., Chilosi et al., 2003; Chen et al., 2018; Cao et al., 
2020). MSHA also reviewed other suggested literature, including 
promising animal studies exploring novel drug treatments for diseases 
caused by exposure to respirable crystalline silica; however, it 
determined that these studies are not sufficiently developed for 
inclusion at this time (e.g., Guo et al., 2019; Huang et al., 2019; Jia 
et al., 2022). MSHA has already included several studies related to 
non-mining occupations throughout its standalone Health Effects 
document. Examples of other occupational studies include studies of 
health effects on granite workers (e.g., Davis et al., 1983; Attfield 
and Costello, 2004), brick workers (e.g., Merlo et al., 1991), agate 
stone grinders (Rastogi et al., 1991), pottery workers (e.g., McDonald 
et al., 1995; Cherry et al., 1998), industrial sand workers (e.g., 
McDonald et al., 2001; Rando et al., 2001), concrete workers (e.g., 
Meijers et al., 2001), ceramic workers (e.g., Forastiere et al., 2002), 
and foundry workers (e.g., Hertzberg et al., 2002; Vihlborg et al., 
2017), among others. Occupations such as granite, industrial sand, or 
concrete workers, represent similar job tasks and exposures which may 
overlap with mining occupations. Others such as brick, pottery, and 
ceramic workers involve processing of mined materials into a commercial 
product.
    To analyze the extensive literature that it considered, MSHA used 
the widely accepted weight-of-evidence (WoE) approach. Under this 
approach, studies with varied methodologies and conclusions are 
evaluated for their overall quality. Causal inferences are drawn based 
on a determination of whether there is substantial evidence that 
exposure increases the risk of a particular adverse health effect. This 
approach is a well-accepted method of conducting health hazard 
assessments (NRC, 2009; NIOSH, 2019a). Additionally, it was used by 
OSHA in its review of health effects literature (2013b) for its 2016 
respirable crystalline silica standard. Factors that MSHA considered in 
its WoE analysis include: (1) size of the cohort studied and power of 
the study to detect a

[[Page 28234]]

sufficiently low level of disease risk; (2) duration of follow-up of 
the study population; (3) potential for study bias, such as selection 
bias or healthy worker effects, and (4) adequacy of underlying exposure 
information for examining exposure-response relationships. Of the 
studies examined in the standalone Health Effects document, studies 
were deemed suitable for inclusion in the FRA if they provided adequate 
quantitative information on exposure and disease risks and were judged 
to be of sufficiently high quality according to the above criteria. 
MSHA's literature review expanded upon OSHA's (2013b) review of the 
health effects literature to support its final respirable crystalline 
silica rule (81 FR 16286), reviewing pertinent new research. MSHA's 
assessment of the literature is consistent with OSHA's conclusion from 
its silica literature review.
    MSHA received one comment from the NSSGA challenging the validity 
of MSHA's literature review methodology (Document ID 1448, Attachment 
3). This commenter submitted a report analyzing MSHA's health effects 
literature review, arguing that MSHA's review cannot be replicated or 
fully evaluated for its scientific validity and claiming that it is 
unclear whether MSHA's interpretations are sufficiently reliable as a 
basis for decision-making. The commenter asserted the need for 
literature reviews to be done pursuant to Lynch et al.'s (2022) 
framework of a ``systematic review,'' a review method that seeks to 
eliminate bias by adhering to a transparent, a priori protocol. The 
commenter also expressed concerns that MSHA's methodology is 
inadequately explained and possibly dated. The commenter suggested 
further studies to be included in MSHA's review and provided specific 
responses to some of MSHA's statements in its literature review.
    On the other hand, the APHA provided a different perspective on the 
methodology (Document ID 1416). This commenter stated that MSHA 
thoroughly describes the health risks, which include developing chronic 
silicosis, accelerated silicosis, progressive massive fibrosis, chronic 
obstructive pulmonary disease, lung cancer and kidney disease. Further, 
the commenter noted that MSHA's review of the health effects literature 
included more than three dozen peer-reviewed papers published in just 
the last few years. This commenter concurred with MSHA's determination 
that miners' exposure to respirable crystalline silica presents a risk 
of material impairment of health or functional capacity.
    MSHA disagrees with the comment challenging MSHA's methodology. 
Although the ``systematic review'' framework outlined in Lynch et al. 
(2022) is increasingly used in review publications, it is not the only 
valid method of conducting a literature review of the current science. 
As explained in the standalone Health Effects document, MSHA's review 
of the scientific literature on respirable crystalline silica used a 
widely accepted WoE approach.
    The term, ``weight-of-evidence'' was coined as early as 40 years 
ago by the NRC (1983) in their seminal publication ``Risk Assessment in 
the Federal Government: Managing the Process''. It has become a 
fundamental element of the risk assessment process (NRC, 2009; EPA, 
1986; Martin et al., 2018; Lee et al., 2023). MSHA selected this 
approach for use in its respirable crystalline silica risk analysis for 
a variety of reasons. First, it has withstood the scrutiny of 
scientists throughout the world (Suter et al., 2020). Second, it has 
been used successfully throughout the world for conducting a wide 
variety of risk assessments and analyses involving a wide range of 
exposures in both occupational and environmental settings (e.g., drugs, 
pesticides, industrial chemicals) (EPA, 1986, 2016; National Research 
Council (NRC), 2009; Suter et al., 2020; Government of Canada, 2022). 
Third, it continues to be a solid and accepted approach that is still 
used today (EPA, 1986, 2016; National Research Council (NRC), 2009; 
Martin et al., 2018; Suter et al., 2020; Government of Canada, 2022; 
Lee et al., 2023). Current searches of the scientific literature (e.g., 
using search engines such as PubMed or Google Scholar) continue to 
identify studies in which the WoE approach has been employed. Finally, 
numerous courts have approved of federal agencies relying on this 
methodology in rulemaking for over 40 years. See Mississippi v. E.P.A., 
744 F.3d 1334, 1344-45 (D.C. Cir. 2013) (upholding the ``weight of 
evidence approach'' because ``one type of study might be useful for 
interpreting ambivalent results from another type . . . and though a 
new study does little besides confirm or quantify a previous finding, 
such incremental (and arguably duplicative) studies are valuable 
precisely because they confirm or quantify previous findings or 
otherwise decrease uncertainty'') (citing Ethyl Corp. v. EPA, 541 F.2d 
1, 26 (D.C. Cir. 1976) (en banc)); N. Am.'s Bldg. Trades Unions v. 
OSHA, 878 F.3d 271, 284 (D.C. Cir. 2017) (rejecting challenges to 
OSHA's ``weight of evidence'' approach supporting its silica 
rulemaking). Thus, MSHA finds that the WoE approach is appropriate for 
use in its respirable crystalline silica rulemaking.
    In summary, MSHA's weight-of-evidence analysis is based on OSHA's 
extensive literature review and peer review process; includes a 
substantial number of studies and data published after the OSHA 
rulemaking; and has received support from NIOSH experts.\16\
---------------------------------------------------------------------------

    \16\ MSHA's review benefitted from feedback and review from 
experts at NIOSH, both informally and through the interagency review 
process organized by OMB, during the literature review process and 
preparation of the standalone Health Effects document.
---------------------------------------------------------------------------

    As described in greater detail in MSHA's standalone Health Effects 
document, the scientific understanding of how respirable crystalline 
silica causes adverse health effects has evolved greatly in the more 
than 45 years since the Mine Act was passed in 1977. MSHA's review of 
the literature indicates that under the existing standards found in 30 
CFR parts 56, 57, 70, 71, and 90, miners are still developing 
preventable diseases that are material impairments of health or 
functional capacity. Regulatory action to reduce occupational exposures 
that cause these diseases is necessary to ensure no miner suffers 
material impairment of health or functional capacity, as required by 
section 101(a)(6)(A) of the Mine Act.
    Based on an extensive review of health effects literature, MSHA 
determines that occupational exposure to respirable crystalline silica 
causes silicosis (acute silicosis, accelerated silicosis, chronic 
silicosis, and progressive massive fibrosis (PMF)), NMRD (including 
COPD), lung cancer, and end-stage renal disease (ESRD). Each of these 
effects is exposure-dependent, potentially chronic, irreversible, 
potentially disabling, and can be fatal. In addition, MSHA's review of 
the health effects literature has shown that respirable crystalline 
silica exposure is causally related to the development of some 
autoimmune disorders through inflammatory pathways. Current health 
information cited in the final standalone Health Effects document 
indicates that miners are suffering material impairment of health or 
functional capacity due to their occupational exposures to respirable 
crystalline silica. MSHA's review of respirable crystalline silica 
health effects concludes that the final rule, which lowers the exposure 
limits in MNM and coal mining to 50 [micro]g/m\3\ and establishes an 
action level of 25 [micro]g/m\3\ for a full-shift exposure, calculated 
as an 8-hour TWA, will reduce the risk

[[Page 28235]]

of miners developing silicosis, NMRD, lung cancer, and renal disease.

B. Toxicity of Respirable Crystalline Silica

    Respirable crystalline silica is released into the environment 
during mining or milling processes, thus creating an airborne hazard. 
The particles may be freshly generated or re-suspended from surfaces on 
which they are deposited in mines or mills. Respirable crystalline 
silica particles may be irregularly shaped and variable in size. These 
particles may be inhaled by miners and can be deposited throughout the 
lungs. Some pulmonary clearance of particles deposited in the alveolar 
region (deep lung) may occur, but many particles can be retained and 
initiate or advance the disease process. The toxicity of these retained 
particles is amplified because the particles are not water-soluble and 
are not metabolized into less toxic compounds. This is important 
because insoluble dusts may remain in the lungs for prolonged periods, 
resulting in a variety of cellular responses that can lead to pulmonary 
disease (ATSDR, 2019). Respirable crystalline silica particles that are 
cleared from the lungs by the lymphatic system are distributed to the 
lymph nodes, blood, liver, spleen, and kidneys, potentially 
accumulating in these other organ systems and causing renal disease and 
other adverse health effects (ATSDR, 2019).
    Physical characteristics relevant to the toxicity of respirable 
crystalline silica primarily relate to its size and surface 
characteristics, both of which play important roles in how respirable 
crystalline silica causes tissue damage. Any factor that influences or 
modifies these physical characteristics may alter the toxicity of 
respirable crystalline silica by affecting the mechanistic processes 
(ATSDR, 2019).
    Inflammatory pathways affect disease development in various systems 
and tissues in the human body. For instance, it has been proposed that 
lung fibrosis caused by exposure to respirable crystalline silica 
results from a cycle of cell damage, oxidant generation, inflammation, 
scarring, and ultimately fibrosis. This has been reported by: Nolan et 
al. (1981), Shi et al. (1989, 1998), Lapp and Castranova (1993), Brown 
and Donaldson (1996), Parker and Banks (1998), Castranova and 
Vallyathan (2000), Castranova (2004), Fubini et al. (2004), Hu et al. 
(2017), Benmerzoug et al. (2018), and Yu et al. (2020).
    Respirable crystalline silica entering the lungs could cause damage 
by a variety of mechanisms, including direct damage to lung cells. In 
addition, activation or stimulation by respirable crystalline silica of 
alveolar macrophages (after phagocytosis) and/or alveolar epithelial 
cells may lead to: (1) release of cytotoxic enzymes, reactive oxygen 
species (ROS), reactive nitrogen species (RNS), inflammatory cytokines 
and chemokines; (2) eventual cell death with the release of respirable 
crystalline silica; and (3) recruitment and activation of 
polymorphonuclear leukocytes (PMNs) and additional alveolar macrophages 
(Castranova and Vallyathan, 2000; Castranova, 2004; Hamilton et al., 
2008). The elevated production of ROS/RNS could result in oxidative 
stress and lung injury that stimulate alveolar macrophages, ultimately 
resulting in fibroblast activation and pulmonary fibrosis (Li et al., 
2018; Feng et al., 2020). The prolonged recruitment of macrophages and 
PMN causes persistent inflammation, regarded as a primary step in the 
development of silicosis.
    The strong immune response in the lung following exposure to 
respirable crystalline silica may also be linked to a variety of extra-
pulmonary adverse effects such as hypergammaglobulinemia 
(overproduction of more than one class of immunoglobulins by plasma 
cells), production of rheumatoid factor, anti-nuclear antibodies, and 
release of other immune complexes (Haustein and Anderegg, 1998; Green 
and Vallyathan, 1996; Parks et al., 1999). Respirable crystalline 
silica exposure has also been associated with ESRD through the 
initiation of immunological injury to the glomerulus of the kidney 
(Calvert et al., 1997).
    Proposed mechanisms involved in respirable crystalline silica-
induced carcinogenesis have included: direct DNA damage, inhibition of 
the p53 tumor suppressor gene, loss of cell cycle regulation; 
stimulation of growth factors, and production on oncogenes (Nolan et 
al., 1981; Shi et al., 1989, 1998; Brown and Donaldson, 1996; 
Castranova, 2004; Fubini et al., 2004).
    Three commenters expressed concerns about the findings of the 
health effects literature review and their relevance to the sorptive 
minerals industry (Document ID 1446, Attachment 1; 1442; 1419). The SMI 
and Essential Minerals Association (EMA) stated that MSHA has an 
incomplete understanding of the latest available scientific research 
(Document ID 1446, Attachment 1; 1442). Asserting that occluded quartz 
in sorptive clays is not fractured (either in the clay formation in 
which it exists or during the mining and processing of the material to 
form sorptive mineral-based products), the SMI concluded that occluded 
quartz in sorptive clays does not pose the health risk posed by 
fractured quartz (Document ID 1446, Attachment 1). Discussing at length 
studies it recommended MSHA include in its health effects literature 
review, SMI and EMA said that much of this research was previously 
considered by OSHA (2013b) and that it had led to OSHA's decision to 
exempt sorptive clays from coverage under OSHA's silica standard. SMI 
also noted that additional research since OSHA's revised silica 
standard was promulgated has advanced the question of how quartz causes 
disease and the difference in risk potential between fractured and 
unfractured and occluded quartz. Asserting that, without consideration 
of the additional research provided, the proposed standard would not be 
based on the best available evidence and would not reflect the latest 
available scientific data in the field, this commenter discussed Mine 
Act statutory provisions and case law that it asserted demonstrate the 
high level of scientific evidence and scrutiny required of MSHA when 
setting health and safety standards.
    A more detailed response to SMI's overall comment can be found in 
Section VIII.A. General Issues of this preamble. In response to the 
suggestion to consider additional studies, MSHA reviewed the suggested 
references and added some to the final standalone Health Effects 
document (Creutzenberg et al., 2008; Borm et al., 2018; Pavan et al., 
2019). MSHA also notes that some of these studies were already cited in 
the version of the standalone Health Effects document published 
alongside the proposed rule (e.g., Donaldson and Borm, 1998; Fubini, 
1998; Bruch et al., 2004; Fubini et al., 2004). Overall, many of the 
studies suggested by the commenter have argued that occluded or aged 
quartz is less toxic but have not suggested that occluded or aged 
quartz is not toxic or carries no risk of disease. MSHA agrees that 
there is some evidence to suggest that occluded silica is less toxic 
than unoccluded silica (Wallace et al., 1996), but there is no evidence 
that occlusion and the initial reduced toxicity persist following 
deposition and retention of the crystalline silica particles in the 
lungs. Similarly, animal studies involving respirable crystalline 
silica suggest that the aged form has lower toxicity than the freshly 
fractured form; however, the aged form still retains toxicity 
(Shoemaker et al., 1995; Vallyathan et al., 1995; Porter et al., 
2002c). From these studies, MSHA concludes that

[[Page 28236]]

exposure to the crystalline silica present in sorptive minerals poses a 
risk of material impairment of health or functional capacity to miners.
    Others appeared to be irrelevant to the scope of the rule, such as 
those focused on amorphous silica, microscopy techniques, or workshop 
discussions (e.g., Mercer et al., 2018; Weber et al., 2018; Driscoll 
and Borm, 2020). MSHA notes that none of the suggested animal studies 
included acute or chronic inhalation exposures to aged or occluded 
respirable crystalline silica. One suggested review, Poland et al. 
(2023) described a 2020 animal inhalation study (nose-only) which did 
not include exposures to aged or occluded respirable crystalline 
silica; the 2020 study was conducted using amorphous silica and the 
data were compared to a 1988 animal study that included whole-body (as 
opposed to nose-only) exposures to respirable crystalline silica.\17\ 
Since this 2020 surface area comparison study described by Poland et 
al. (2023) focused on amorphous silica, which is not a part of this 
rulemaking, it was deemed unsuitable for inclusion in MSHA's final 
standalone Health Effects document. Other animal studies discussing 
aged or occluded respirable crystalline silica suggested used either 
intratracheal instillation or oropharyngeal aspiration, which do not 
reflect the behavior of particles that enter the lungs via inhalation, 
including lung clearance (Foster et al., 2001; Wong, 2007; Driscoll and 
Borm, 2020). Section VIII.A. General Issues of this preamble responds 
more fully to these comments. In its response, MSHA notes that several 
studies of occluded or fractured quartz discussed their methods, 
including careful handling of occluded samples, but did not include 
analysis of occluded quartz that was analyzed with less than careful 
handling. This is not applicable to real-world conditions; MSHA's 
experience with mining and processing of sorptive minerals includes the 
use of grinding and milling processes.
---------------------------------------------------------------------------

    \17\ These two studies (1988 and 2020) described by Poland et 
al. (2023) had limited comparability for a variety of reasons; they 
differ in: (1) rat strains (types of rats), (2) exposure durations, 
(3) recovery periods, as well as (4) types of inhalation exposure, 
among others.
---------------------------------------------------------------------------

    After reviewing the available literature, MSHA concludes that 
miners working in the sorptive minerals industry are exposed to 
respirable crystalline silica. OSHA (2013b) concluded that while there 
was considerable evidence that several environmental influences can 
modify surface activity to either enhance or diminish the toxicity of 
silica, the available information was insufficient to determine in any 
quantitative way how these influences may affect disease risk to 
workers in any particular workplace setting (81 FR at 16311). MSHA 
agrees with OSHA (2013b) that there is evidence to support that surface 
activity of respirable crystalline silica may play a role in producing 
disease. However, mining is significantly different from other 
industries regulated by OSHA, for instance, in that it involves 
milling, grinding and removal of overburden. While the available 
information is insufficient to determine how these influences may 
affect disease risk to miners in any quantitative way and in any mining 
sector. MSHA is permitted `` `to err on the side of overprotection by 
setting a fully adequate margin of safety.' '' Kennecott Greens Creek 
Min. Co. v. Mine Safety & Health Admin., 476 F.3d 946, 952 (D.C. Cir. 
2007) (quoting Nat'l Min. Ass'n v. Mine Safety & Health Admin., 116 
F.3d 520, 528 (D.C. Cir. 1997)).

C. Diseases

1. Silicosis
    Silicosis is a material impairment of health or functional 
capacity, as defined by the Mine Act, and refers to a group of lung 
diseases caused by the inhalation of respirable crystalline silica. See 
30 U.S.C. 811(a)(6)(A). Silicosis is a progressive, occupational 
disease, in which accumulation of respirable crystalline silica 
particles causes an inflammatory reaction in the lung. This reaction 
leads to lung damage and scarring and, in some cases, progresses to 
disability and death. Respirable crystalline silica has long been 
identified as a cause of lung diseases in miners, and adverse health 
effects were noted and described as early as 1550 by Georgius Agricola 
(Agricola, as translated by Banner in 1950). Based on the review of the 
literature, MSHA has determined that exposure to respirable crystalline 
silica causes silicosis in MNM and coal miners and that it is a 
significant cause of premature morbidity and mortality (Mazurek and 
Attfield, 2008; Mazurek and Wood, 2008a,b; Mazurek et al., 2015, 2018).
    When respirable crystalline silica accumulates in the lungs, it 
causes an inflammatory reaction, leading to lung damage and scarring. 
Silicosis can continue to develop even after silica exposure has ceased 
(Hughes et al., 1982; Ng et al., 1987a; Hessel et al., 1988; Kreiss and 
Zhen, 1996; Miller et al., 1998; Yang et al., 2006). It is not 
reversible, and there is only symptomatic treatment, including 
bronchodilators to maintain open airways, oxygen therapy, and lung 
transplants in the most severe cases (Cochrane et al., 1956; Ng et al., 
1987a; Lee et al., 2001; Mohebbi and Zubeyri, 2007; Kimura et al., 
2010; Laney et al., 2017; Almberg et al., 2020; Hall et al., 2022). 
Respirable crystalline silica exposure in miners can lead to all three 
forms of silicosis (acute, accelerated, and chronic). These forms 
differ in the rate of exposure, pathology (structural and functional 
changes produced by the disease), and latency period from exposure to 
disease onset.
    Acute silicosis is an aggressive inflammatory process following 
intense exposure to respirable crystalline silica for ``periods 
measured in months rather than years'' (Cowie and Becklake, 2016). It 
causes alveolar proteinosis, an accumulation of lipoproteins in the 
alveoli of the lungs. This restructuring of the lungs leads to symptoms 
such as coughing and difficult or labored breathing, and often 
progresses to profound disability and death due to respiratory failure 
or infectious complications. In addition, symptoms often advance even 
after exposure has stopped, primarily due to the massive amount of 
protein debris and fluid that collects in the alveoli, which leads to 
the impairment of gas exchange (oxygen) in the lungs and respiratory 
distress of the patient. The X-ray appearance and results of 
microscopic examination of acute silicosis are like those of idiopathic 
(having an unknown cause) pulmonary alveolar proteinosis.
    Accelerated silicosis includes both inflammation and fibrosis and 
is associated with intense respirable crystalline silica exposure. 
Accelerated silicosis usually manifests over a period of three to ten 
years (Cowie and Becklake, 2016), but it can develop in as little as 
two to five years if exposure is sufficiently intense (Davis, 1996). 
Accelerated silicosis may have features of both chronic and acute 
silicosis, with alveolar proteinosis in addition to X-ray evidence of 
fibrosis, seen as small opacities or the large opacities of PMF. 
Although the symptoms are like those of chronic silicosis, the clinical 
and radiographic progression of accelerated silicosis evolves more 
rapidly, and often leads to PMF, severe respiratory impairment, and 
respiratory failure. Accelerated silicosis can progress with associated 
morbidity and mortality, even if exposure ceases. Accelerated silicosis 
is frequently fatal.
    Chronic silicosis is the most frequently observed form of silicosis 
in the United States today (Banks, 2005; OSHA, 2013b; Cowie and 
Becklake,

[[Page 28237]]

2016). It is also the most common form of silicosis diagnosed in 
miners. Chronic silicosis is a fibrotic process that typically follows 
less intense respirable crystalline silica exposure of ten or more 
years (Becklake, 1994; Balaan and Banks, 1998; NIOSH, 2002b; 
Kambouchner and Bernaudin, 2015; Cowie and Becklake, 2016; Rosental, 
2017; ATSDR, 2019; Barnes et al., 2019; Hoy and Chambers, 2020). It is 
identified histopathologically by the presence of the silicotic islet 
or nodule that is an agent-specific fibrotic lesion and is recognized 
by its pathology (Balaan and Banks, 1998). Chronic silicosis develops 
slowly and creates rounded whorls of scar tissue that progressively 
destroy the normal structure and function of the lungs. In addition, 
the scar tissue opacities become visible by chest X-ray or computerized 
tomography (CT) only after the disease is well-established and the 
lesions become large enough to view. As a result, surveys based on 
identification of small and large opacity disease on chest X-ray films 
usually underestimate the true prevalence of silicosis (Craighead and 
Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and 
Velho, 2002). The lesions eventually advance and result in lung 
restriction, reduced lung volumes, decreased pulmonary compliance, and 
reduction in the gas exchange capabilities of the lungs (Balaan and 
Banks, 1998). As the disease progresses, affected miners may have 
chronic cough, sputum production, shortness of breath, and reduced 
pulmonary function.
    Among coal miners, silicosis is usually found in conjunction with 
simple coal workers' pneumoconiosis (CWP) because of the miners' 
exposures to RCMD that also contains respirable crystalline silica 
(Castranova and Vallyathan, 2000). Coal miners also face an added risk 
of developing mixed-dust pneumoconiosis (MDP) (includes the presence of 
coal dust macules), mixed-dust fibrosis (MDF), and/or silicotic nodules 
(Honma et al., 2004; Green, 2019). The autopsy studies on coal miners 
that MSHA reviewed support a pathological relationship between mixed-
RCMD or respirable crystalline silica exposures and PMF, silicosis, and 
CWP (Davis et al., 1979; Ruckley et al., 1981, 1984; Douglas et al., 
1986; Fernie and Ruckley, 1987; Green et al., 1989, 1998b; Attfield et 
al., 1994; Vallyathan et al., 2011; Cohen et al., 2016, 2019, 2022). 
Autopsy studies in British coal miners indicated that the more advanced 
the disease, the more mixed-RCMD components were retained in the lung 
tissue (Ruckley et al., 1984; Douglas et al., 1986). Green et al. 
(1998b) determined that of 4,115 coal miners with pneumoconiosis 
autopsied as part of the National Coal Workers' Autopsy Study (NCWAS), 
39 percent had mixed dust nodules and 23 percent had silicotic nodules.
    PMF or ``complicated silicosis'' has been diagnosed in both coal 
and MNM miners exposed to dusts containing respirable crystalline 
silica. Recent literature on the pathophysiology of PMF supports the 
importance of crystalline silica as a cause of PMF in silica-exposed 
workers such as coal miners (Cohen et al., 2016, 2022), sandblasters 
(Hughes et al., 1982; Abraham and Wiesenfeld, 1997), industrial sand 
workers (Vacek et al., 2019), hard rock miners (Verma et al., 1982, 
2008), and gold miners (Carneiro et al., 2006a; Tse et al., 2007b).
a. Classifying Radiographic Findings of Silicosis
    The studies reviewed by MSHA used one of two established methods 
for identifying findings of pneumoconiosis: the International Labour 
Office (ILO) Classification System or the Chinese categorization 
system, each of which is described below. In addition, the NIOSH case 
definition of silicosis used in surveillance systems relies on the ILO 
system.
    The ILO developed a standardized system to classify the 
radiographic appearances of pneumoconiosis identified in chest X-rays 
films or digital chest radiographic images (ILO, 1980, 2002, 2011, 
2022). One aspect of the ILO system involves grading the size, shape, 
and profusion (density) of opacities in the lungs. The density of 
opacities is classified on a four-point major category scale (category 
0, 1, 2, or 3), with each major category divided into three 
subcategories, giving a 12-point scale between 0/- and 3/+. Differences 
between ILO categories are subtle. For each subcategory, the top number 
indicates the major category that the profusion most closely resembles, 
and the bottom number indicates the major category that was given 
secondary consideration. For example, film readers may assign 
classifications such as 1/0, which means the reader classified it as 
category 1, but category 0 (normal) was also considered (ILO, 2022). 
Major category 0 indicates the absence of visible opacities consistent 
with pneumoconiosis and categories 1 to 3 reflect increasing profusion 
of opacities and a concomitant increase in severity of disease.
    However, some studies in MSHA's literature review used the Chinese 
system of X-ray classification based on the ``Radiological Diagnostic 
Criteria of Pneumoconiosis and Principles for Management of 
Pneumoconiosis'' (GB5906-86). This includes four categories of 
pneumoconiosis findings: a suspected case (0+), stage I, stage II, or 
stage III. Under this scheme, a panel of three radiologists determines 
the presence and severity of radiographic changes consistent with 
pneumoconiosis. The four categories correspond to ILO profusion 
category 0/1, category 1, category 2, and category 3, respectively. A 
suspected case of silicosis (0+) in a dust-exposed worker refers to a 
dust response in the lung and its corresponding lymph nodes, or a scale 
and severity of small opacities that fall short of the level observed 
in a stage I case of silicosis (Chen et al., 2001; Yang et al., 2006).
    MSHA's analysis of silicosis studies uses NIOSH's surveillance case 
definition to determine the presence of silicosis. As described further 
in the final standalone Health Effects document, NIOSH defines the 
presence of silicosis in terms of the ILO system and considers a small 
opacity profusion score of 1/0 or greater to indicate pneumoconiosis 
(NIOSH, 2014b). This definition originated from testimony before 
Congress regarding the 1969 Coal Act in which the Public Health Service 
recommended that miners be removed from dusty environments as soon as 
they showed ``minimal effects'' of dust exposure on a chest X-ray 
(i.e., pinpoint, dispersed micro-nodular lesions). MSHA interprets 
``minimal effects'' to mean an X-ray ILO profusion score of category 1/
0 or greater. This is also consistent with Hnizdo et al. (1993), which 
recommended that, due to the low sensitivity of chest x-rays for 
detecting silicosis, radiographs consistent with an ILO category of 0/1 
or greater be considered indictive of silicosis among workers exposed 
to a high concentration of silica-containing dust.
b. Progression and Associated Impairment
    MSHA reviewed studies referenced by OSHA (2013b) that examined the 
relationship between exposure and progression, as well as between X-ray 
findings and pulmonary function. Additionally, MSHA considered 
literature not previously reviewed by OSHA (2013b) (Mohebbi and 
Zubeyri, 2007; Wade et al., 2011; Dumavibhat et al., 2013).
    Progression of silicosis is recognized when there are changes or 
worsening of the opacities in the lungs, and sequential chest 
radiographs are

[[Page 28238]]

classified higher by one or more subcategories (e.g., from 1/0 to 1/1) 
because of changes in the location, thickness, or extent of lung 
abnormalities and/or the presence of calcifications. The higher the 
category number, the more severe the disease. Due to the variability in 
film technique and classification of films, some investigators count 
progression as advancing two or more subcategories, such as 1/0 to 1/2.
    Overall, the studies indicate that progression is more likely with 
continued exposure, especially high average levels of exposure. 
Progression is also more likely for miners with higher ILO profusion 
classifications. As discussed previously, progression of disease may 
continue after miners are no longer exposed to respirable crystalline 
silica (Cochrane et al., 1956; Maclaren and Soutar, 1985; Hurley et 
al., 1987; Kimura et al., 2010; Almberg et al., 2020; Hall et al., 
2020b). In addition, although lung function impairment is highly 
correlated with chest X-ray films indicating silicosis, researchers 
caution that respirable crystalline silica exposure could impair lung 
function before it is detected by X-ray.
    Of the studies in which silicosis progression was documented in 
populations of workers, four included quantitative exposure data that 
were based on either existing exposure levels or historical 
measurements of respirable crystalline silica (Ng et al., 1987a study 
of granite miners; Hessel et al., 1988 study of gold miners; Miller et 
al., 1998 study of coal miners; Miller and MacCalman, 2010 study of 
coal miners). In some studies, episodic exposures to high average 
concentrations were documented and considered in the analysis. These 
exposures were strong predictors of more rapid progression beyond that 
predicted by cumulative exposure alone. Otherwise, the variable most 
strongly associated in these studies with progression of silicosis was 
cumulative respirable crystalline silica exposure (the product of the 
concentration times duration of exposure, which is summed over time) 
(Ng et al., 1987a; Hessel et al., 1988; Miller et al., 1998; Miller and 
MacCalman, 2010). In the absence of concentration measurements, 
duration of employment in specific occupations known to involve 
exposure to high levels of respirable dust has been used as a surrogate 
for cumulative exposure to respirable crystalline silica. Duration of 
employment has also been found to be associated with the progression of 
silicosis (Ogawa et al., 2003a).
    Miller et al. (1998) examined the impact of high quartz exposures 
on silicosis disease progression in 547 British coal miners from 1990 
to 1991 and evaluated chest X-ray changes after the mines closed in 
1981. The study reviewed chest X-rays taken during health surveys 
conducted between 1954 and 1978 and data from extensive exposure 
monitoring conducted between 1964 and 1978. For some occupations, 
exposure was high because miners had to dig through a sandstone stratum 
to reach the coal. For example, quarterly mean respirable crystalline 
silica (quartz) concentrations ranged from 1,000 to 3,000 [micro]g/m\3\ 
and for a brief period, concentrations exceeded 10,000 [micro]g/m\3\ 
for one job. Some of these high exposures were associated with 
accelerated disease progression in these miners.
    Buchanan et al. (2003) reviewed the exposure history and chest X-
ray progression of 371 retired miners and found that short-term 
exposures (i.e., ``a few months'') to high concentrations of respirable 
crystalline silica (e.g., >2,000 [micro]g/m\3\) increased the silicosis 
risk by three-fold (compared to the risk of cumulative exposure alone) 
(see the standalone FRA document).
    The risks of increased rate of progression predicted by Buchanan et 
al. (2003) have been seen in coal miners (Miller et al., 1998; Laney et 
al., 2010, 2017; Cohen et al., 2016), metal (Hessel et al., 1988; 
Hnizdo and Sluis-Cremer, 1993; Nelson, 2013), and nonmetal miners such 
as silica plant and ground silica mill workers, whetstone cutters, and 
silica flour packers (NIOSH, 2000a,b; Ogawa et al., 2003a; Mohebbi and 
Zubeyri, 2007). Accordingly, it is important to limit higher exposures 
to respirable crystalline silica to minimize the risk of rapid 
progressive pneumoconiosis (RPP) in miners. RPP is the development of 
progressive massive fibrosis (PMF) and/or an increase in small opacity 
profusion greater than one subcategory over five years or less 
(Ant[atilde]o et al., 2005).
    The results of many surveillance studies conducted by NIOSH as part 
of the Coal Workers' Health Surveillance Program indicate that the 
pathology of pneumoconiosis in coal miners has changed over time, in 
part due to increased exposure to respirable crystalline silica. The 
studies of Cohen et al. (2016, 2022) indicate that RPP develops due to 
increased exposure to respirable crystalline silica among contemporary 
coal miners as compared to historical coal miners. Through the 
examination of pathologic materials from 23 contemporary (born in or 
after 1930) and 62 historical coal miners (born between 1910 and 1930) 
with severe pneumoconiosis, who were autopsied as part of NCWAS, Cohen 
et al. (2022) found a significantly higher proportion of silica-type 
PMF among contemporary miners (57 percent vs. 18 percent, p <0.001). 
They also found that mineral dust alveolar proteinosis (MDAP) was more 
common in the current generation of miners and that the lung tissues of 
contemporary coal miners contained a significantly greater percentage 
and concentration of silica particles than those of past generations of 
miners.
    Many studies found an association between pulmonary function 
decrements and ILO profusion category 2 or 3. Additionally, the review 
of the literature indicated a decreased lung function among workers who 
were exposed to respirable crystalline silica. MSHA therefore concludes 
that respirable crystalline silica exposure may impair lung function in 
some instances before silicosis can be detected by chest X-rays.
c. Occupation-Based Epidemiological Studies
    MSHA reviewed the occupation-based epidemiological literature, 
which examines health outcomes among workers and their potential 
association with conditions in the workplace. In addition, MSHA 
reviewed additional occupation-based literature specific to respirable 
crystalline silica exposure in MNM and coal miners and concludes that 
respirable crystalline silica exposure increases the risk of silicosis 
morbidity and early mortality.
    One study examined the acute and accelerated silicosis outbreak 
that occurred during and after construction of Hawk's Nest Tunnel in 
West Virginia from 1930 to 1931. There, an estimated 2,500 men worked 
in a tunnel drilling rock consisting of 90 percent silica or more. The 
study later estimated that at least 764 of the 2,500 workers (30.6 
percent) died from acute or accelerated silicosis (Cherniack, 1986). 
There was also high turnover among the tunnel workers, with an average 
length of employment underground of only about two months.
    MSHA's review included the occupation-based literature cited by 
OSHA (2013b) in developing its respirable crystalline silica standard 
(OSHA, 2016a). Overall, MSHA found substantial evidence suggesting that 
occupational exposure to respirable crystalline silica increases the 
risk of silicosis. This conclusion is consistent with OSHA's 
conclusion.
    In a population of granite quarry workers (mean length of 
employment:

[[Page 28239]]

23.4 years) exposed to an average respirable crystalline silica 
concentration of 480 [micro]g/m\3\, 45 percent of those diagnosed with 
simple silicosis showed radiological progression of disease two to ten 
years after diagnosis (Ng et al., 1987a). Among a population of gold 
miners, 92 percent showed progression after 14 years (Hessel et al., 
1988). Chinese factory workers and miners who were categorized under 
the Chinese system of X-ray classification as ``suspected'' silicosis 
cases (analogous to ILO 0/1) had a progression rate to stage I 
(analogous to ILO major category 1) of 48.7 percent, with an average 
interval of about 5.1 years (Yang et al., 2006).
    The risk of silicosis, and particularly its progression, carries 
with it an increased risk of reduced lung function. Strong evidence has 
shown that lung function deteriorates more rapidly in miners exposed to 
respirable crystalline silica, especially in those with silicosis 
(Hughes et al., 1982; Ng and Chan, 1992; Malmberg et al., 1993; Cowie, 
1998). The rates of decline in lung function are greater where disease 
shows evidence of radiologic progression (B[eacute]gin et al., 1987; Ng 
et al., 1987a; Ng and Chan, 1992; Cowie, 1998). Additionally, the 
average deterioration of lung function exceeds that in smokers (Hughes 
et al., 1982).
    Blackley et al. (2015) found progressive lung function impairment 
across the range of radiographic profusion of simple CWP in a cohort of 
8,230 coal miners that participated in the Enhanced Coal Workers' 
Health Surveillance Program from 2005 to 2013. There, 269 coal miners 
had category 1 or 2 chronic CWP. This study also found that each 
increase in profusion score was associated with decreases in various 
lung function parameters: 1.5 percent (95 percent CI, 1.0 percent-1.9 
percent) in forced expiratory volume in one second (FEV1) 
percent predicted, 1.0 percent (95 percent CI, 0.6 percent-1.3 percent) 
forced vital capacity (FVC) percent predicted, and 0.6 percent (95 
percent CI, 0.4 percent-0.8 FEV1/FVC).
    Accordingly, MSHA concludes that respirable crystalline silica 
exposure increases the risk of silicosis morbidity and mortality among 
miners. This conclusion is consistent with OSHA's conclusion that there 
is substantial evidence that occupational exposure to respirable 
crystalline silica increases the risk of silicosis.
d. Surveillance Data
    In addition to occupation-based epidemiological studies, MSHA 
reviewed surveillance studies, including those submitted by commenters, 
which provide and interpret data to facilitate the prevention and 
control of disease, and ultimately MSHA finds that the prevalence of 
silicosis generally increases with duration of exposure (work tenure). 
This is evident from the statistically significant proportional 
mortality ratios (PMRs) reported in the National Occupational Mortality 
System (NORMS) data previously reviewed by OSHA and reported by MSHA in 
its standalone Health Effects document. Several small and ad hoc 
surveillance reports reported in the standalone Health Effects document 
also found a prevalence of silicosis of up to 50 percent among working 
and retired miners (Hnizdo and Sluis-Cremer, 1993; Ng and Chan, 1994; 
Kreiss and Zhen, 1996; Finkelstein, 2000).
    However, the available statistics may underestimate silicosis-
related morbidity and mortality in miners. It has been widely reported 
that statistics underestimate silicosis cases due to: (1) 
misclassification of causes of death (as TB, chronic bronchitis, 
emphysema, or cor pulmonale); (2) errors in recording occupation on 
death certificates; and (3) misdiagnosis of disease (Windau et al., 
1991; Goodwin et al., 2003; Rosenman et al., 2003; Blackley et al., 
2017). Furthermore, reliance on chest X-ray findings may lead to missed 
silicosis cases when fibrotic changes in the lung are not yet visible 
on chest X-rays. In other words, silicosis may be present but not yet 
detectable by chest X-ray, or it may be more severe than indicated by 
the assigned profusion score (Craighead and Vallyathan, 1980; Hnizdo et 
al., 1993; Rosenman et al., 1997).
e. Pulmonary Tuberculosis
    In addition to the relationship between silica exposure and 
silicosis, studies indicate a relationship between silica exposure, 
silicosis, and pulmonary TB. MSHA reviewed these studies and concluded 
that silica exposure and silicosis increase the risk of pulmonary TB 
(Cowie, 1994; Hnizdo and Murray, 1998; teWaterNaude et al., 2006), 
concurring with the conclusion reached by OSHA in its review.
    Although early descriptions of dust diseases of the lung did not 
distinguish between TB and silicosis and most fatal cases described in 
the first half of the 20th century were likely a combination of 
silicosis and TB (Castranova et al., 1996), more recent findings have 
demonstrated that respirable crystalline silica exposure, even without 
silicosis, increases the risk of infectious (active) pulmonary TB 
(Sherson and Lander, 1990; Cowie, 1994; Hnizdo and Murray, 1998; 
teWaterNaude et al., 2006). These co-morbid conditions hasten the 
development of respiratory impairment and increased mortality risk even 
beyond the risk in unexposed persons with active TB (Banks, 2005).
    Ng and Chan (1991) hypothesized that silicosis and TB ``act 
synergistically'' (are more than additive) to increase fibrotic scar 
tissue (leading to massive fibrosis) or to enhance susceptibility to 
active mycobacterial infection. The authors found that lung fibrosis is 
common to both diseases, and that both diseases decrease the ability of 
alveolar macrophages to aid in the clearance of dust or infectious 
particles.
    These findings are also supported by studies published since OSHA's 
(2013b) review (Oni and Ehrlich, 2015; Ndlovu et al., 2019). Oni and 
Ehrlich (2015) reviewed a case of silico-TB in a former gold miner with 
ILO category 2/2 silicosis. Ndlovu et al. (2019) found that in a study 
sample of South African gold miners who had died from causes other than 
silicosis between 2005 and 2015, 33 percent of men (n=254) and 43 
percent of women (n=29) at autopsy were found to have TB, whereas seven 
percent of men (n=54) and three percent of women (n=4) were found to 
have pulmonary silicosis.
    Overall, MSHA finds, consistent with OSHA's conclusion, that silica 
exposure increases the risk of pulmonary TB, and that pulmonary TB can 
be a complication of chronic silicosis.
2. Nonmalignant Respiratory Disease (Excluding Silicosis)
    In addition to causing silicosis, exposure to respirable 
crystalline silica causes other NMRD. NMRD is an umbrella term that 
includes chronic obstructive pulmonary disease (COPD). Emphysema and 
chronic bronchitis are two lung diseases included within COPD. In 
patients with COPD, either chronic bronchitis or emphysema may be 
present or both conditions may be present together (ATS, 2010a).
    Based on its review of the literature, MSHA concludes that exposure 
to respirable crystalline silica increases the risk for mortality from 
NMRD. The following summarizes MSHA's review of the literature.
a. Emphysema
    Emphysema results in the destruction of lung architecture in the 
alveolar region, causing airway obstruction and impaired gas exchange. 
Based on its health effects literature review, MSHA concludes that 
exposure to respirable crystalline silica can increase the risk of 
emphysema, regardless of whether silicosis is present. In addition, 
MSHA concludes that this is the case for

[[Page 28240]]

smokers and that smoking amplifies the effects of respirable 
crystalline silica exposure, increasing the risk of emphysema. MSHA's 
conclusions are consistent with those drawn by OSHA (2013b). The 
reviewed studies are summarized below.
    Becklake et al. (1987) determined that a miner who had worked in a 
high dust environment for 20 years had a greater chance of developing 
emphysema than a miner who had never worked in a high dust environment. 
In a retrospective cohort study, Hnizdo et al. (1991a) used autopsy 
lung specimens from 1,553 gold miners to investigate the types of 
emphysema caused by respirable crystalline silica and found that the 
occurrence of emphysema was related to both smoking and dust exposure. 
This study also found a significant association between emphysema, both 
panacinar and centriacinar emphysema types, and length of employment 
for miners working in high dust occupations. A separate study by Hnizdo 
et al. (1994) on lifelong non-smoking South African gold miners found 
that the degree of emphysema was significantly associated with the 
degree of hilar gland nodules, which the authors suggested might serve 
as a surrogate for respirable crystalline silica exposure. While Hnizdo 
et al. (2000) conversely found that emphysema prevalence was decreased 
in relation to dust exposure, the authors suggested that selection bias 
was responsible for this finding.
    The findings of several cross-sectional and case-control studies 
were more mixed. For example, de Beer et al. (1992) found an increased 
risk for emphysema; however, the reported odds ratio (OR) was smaller 
than that previously reported by Becklake et al. (1987). A study by 
Cowie et al. (1993) found that the presence and grade of emphysema were 
statistically significant in Black underground gold miners. 
B[eacute]gin et al. (1995) found that respirable crystalline silica-
exposed smokers without silicosis had a higher prevalence of emphysema 
than a group of asbestos-exposed workers with a similar smoking 
history.
    Several of the studies found that emphysema might occur in 
respirable crystalline silica-exposed workers who did not have 
silicosis and suggested a causal relationship between respirable 
crystalline silica exposure and emphysema (Becklake et al., 1987; 
Hnizdo et al., 1994; B[eacute]gin et al., 1995). Experimental (animal) 
studies found that emphysema occurred at lower respirable crystalline 
silica exposure concentrations than fibrosis in the airways or the 
appearance of early silicotic nodules (Wright et al., 1988). These 
findings tend to support human studies that respirable crystalline 
silica-induced emphysema can occur absent signs of silicosis.
    OSHA (2013b) and others have concluded that there is a relationship 
between respirable crystalline silica exposure and emphysema. Green and 
Vallyathan (1996) reviewed several studies of emphysema in workers 
exposed to silica and found an association between cumulative dust 
exposure and death from emphysema. The IARC (1997) also reviewed 
several studies and concluded that exposure to respirable crystalline 
silica increases the risk of emphysema. Additionally, NIOSH (2002b) 
concluded in its Hazard Review that occupational exposure to respirable 
crystalline silica is associated with emphysema; however, it noted some 
epidemiological studies that suggested that this effect might be less 
frequent or absent in non-smokers.
    Overall, MSHA concludes that exposure to respirable crystalline 
silica causes emphysema even in the absence of silicosis. Thus, MSHA 
concurs with the conclusions previously reached by OSHA (2013b).
b. Chronic Bronchitis
    MSHA considered many studies that examined the association between 
respirable crystalline silica exposure and chronic bronchitis and 
concluded the following: (1) exposure to respirable crystalline silica 
causes chronic bronchitis regardless of whether silicosis is present; 
(2) an exposure-response relationship may exist; and (3) smokers may be 
at an increased risk of chronic bronchitis compared to non-smokers. 
Chronic bronchitis is long-term inflammation of the bronchi, increasing 
the risk of lung infections. This condition develops slowly by small 
increments and ``exists'' when it reaches a certain stage, specifically 
the presence of a productive cough with sputum production for at least 
three months of the year for at least two consecutive years (ATS, 
2010b). MSHA's conclusions are supported by OSHA's review of the 
literature.
    Miller et al. (1997) reported a 20 percent increased risk of 
chronic bronchitis in a British mining cohort compared to the disease 
occurrence in the general population. Using British pneumoconiosis 
field research data, Hurley et al. (2002) calculated estimates of 
mixed-RCMD-related disease in British coal miners at exposure levels 
that were common in the late 1980s and related their lung function and 
development of chronic bronchitis with their cumulative dust exposure. 
The authors estimated that by the age of 58, 5.8 percent of these men 
would report breathlessness for every 100 gram-hour/m\3\ dust exposure. 
The authors also estimated the prevalence of chronic bronchitis at age 
58 would be four percent per 100 gram-hour/m\3\ of dust exposure. These 
miners averaged over 35 years of tenure in mining and a cumulative 
respirable dust exposure of 132 gram-hour/m\3\ (Hurley et al., 2002).
    Cowie and Mabena (1991) found that chronic bronchitis was present 
in 742 of 1,197 (62 percent) South African gold miners, and Ng et al. 
(1992b) found a higher prevalence of respiratory symptoms, independent 
of smoking and age, in Singaporean granite quarry workers exposed to 
high levels of dust (rock drilling and crushing) compared to those 
exposed to low levels of dust (maintenance and transport workers). 
However, Irwig and Rocks (1978) compared symptoms of chronic bronchitis 
in silicotic and non-silicotic South African gold miners. They did not 
find as clear a relationship as did the above studies and concluded 
that the symptoms were not statistically more prevalent in the 
silicotic miners, although prevalence was slightly higher.
    Sluis-Cremer et al. (1967) found that dust-exposed male smokers had 
a higher prevalence of chronic bronchitis than non-dust exposed smokers 
in a gold mining town in South Africa. Similarly, Wiles and Faure 
(1975) found that the prevalence of chronic bronchitis rose 
significantly with increasing dust concentration and cumulative dust 
exposure in South African gold miners who were smokers, nonsmokers, and 
ex-smokers. Rastogi et al. (1991) found that female grinders of agate 
stones in India had a significantly higher prevalence of acute 
bronchitis, but they had no increase in the prevalence of chronic 
bronchitis compared to controls matched by socioeconomic status, age, 
and smoking. However, the study noted that the grinders' respirable 
crystalline silica exposure durations were very short, and control 
workers may also have been exposed to respirable crystalline silica 
(Rastogi et al., 1991).
    Studies examining the effect of years of mining on chronic 
bronchitis risk were mixed. Samet et al. (1984) found that prevalence 
of symptoms of chronic bronchitis was not associated with years of 
mining in a population of underground uranium miners, even after 
adjusting for smoking. However, Holman et al. (1987) studied gold 
miners in West Australia and found that the prevalence of chronic 
bronchitis, as indicated by ORs (controlled for age and smoking), was 
significantly increased in those who had worked in the mines for

[[Page 28241]]

over one year, compared to lifetime non-miners. In addition, while 
other studies found no effect of years of mining on chronic bronchitis 
risk, those studies often qualified this result with possible 
confounding factors. For example, Kreiss et al. (1989) studied 281 
hard-rock (molybdenum) miners and 108 non-miner residents of Leadville, 
Colorado. They did not find an association between the prevalence of 
chronic bronchitis and work in the mining industry (Kreiss et al., 
1989); however, it is important to note that the mine had been 
temporarily closed for five months when the study began, so miners were 
not exposed at the time of the study.
    Some reviews concluded that respirable crystalline silica exposure 
causes the development of bronchitis. The American Thoracic Society 
(ATS) (1997) published a review that found chronic bronchitis to be 
common among worker groups exposed to dusty environments contaminated 
with respirable crystalline silica. NIOSH (2002b) also published a 
review demonstrating that occupational exposure to respirable 
crystalline silica has been associated with bronchitis; however, some 
epidemiological studies suggested this effect might be less frequent or 
absent in non-smokers.
    Additionally, Hnizdo et al. (1990) re-analyzed data from an earlier 
investigation (Wiles and Faure, 1975) and found an independent 
exposure-response relationship between respirable crystalline silica 
exposure and impaired lung function. For miners with less severe 
impairment, the effects of smoking and dust together were additive. The 
authors also found that for miners with the most severe impairment, the 
effects of smoking and dust were synergistic (more than additive) 
(Hnizdo et al., 1990).
    Overall, MSHA concludes that exposure to respirable crystalline 
silica causes chronic bronchitis, regardless of whether silicosis is 
present, and that an exposure-response relationship may exist. This 
conclusion is consistent with the findings of OSHA's Health Effects 
document (2013b).
c. Pulmonary Function Impairment
    Pulmonary function impairment is a common feature of NMRD and may 
be assessed via spirometry (lung volumes, flows) and gas diffusion 
tests. MSHA has reviewed the studies cited by OSHA and agrees with 
their conclusions. Based on its review of the evidence in numerous 
longitudinal and cross-sectional studies and reviews, OSHA concluded 
that there is an exposure-response relationship between respirable 
crystalline silica and the development of impaired lung function. OSHA 
also concluded that the effect of tobacco smoking on this relationship 
may be additive or synergistic, and workers who were exposed to 
respirable crystalline silica, but did not show signs of silicosis, may 
also have pulmonary function impairment.
    OSHA reviewed several longitudinal studies regarding the 
relationship between respirable crystalline silica exposure and 
pulmonary function impairment. To evaluate whether exposure to silica 
affects pulmonary function in the absence of silicosis, the studies 
focused on workers who did not exhibit progressive silicosis.
    Among both active and retired Vermont granite workers exposed to an 
average quartz dust exposure level of 60 [micro]g/m\3\, researchers 
found no exposure-related decreases in pulmonary function (Graham et 
al., 1981, 1994). However, Eisen et al. (1995) found significant 
pulmonary decrements among a subset of granite workers who left work 
(termed ``dropouts'') and consequently did not voluntarily participate 
in the last of a series of annual pulmonary function tests. This group 
experienced steeper declines in lung function compared to the subset of 
workers who remained at work (termed ``survivors'') and participated in 
all tests, and these declines were significantly related to dust 
exposure. Exposure-related changes in lung function were also reported 
in a 12-year study of granite workers (Malmberg et al., 1993), in two 
five-year studies of South African miners (Hnizdo, 1992; Cowie, 1998), 
and in a study of foundry workers whose lung function was assessed 
between 1978 and 1992 (Hertzberg et al., 2002). Similar reductions in 
FEV1 (indicating an airway obstruction) were linked to 
respirable crystalline silica exposure.
    Each of these studies reported its findings in terms of rates of 
decline in any of several pulmonary function measures (e.g., 
FEV1, FVC, FEV1/FVC). To put these declines in 
perspective, Eisen et al. (1995) reported that the rate of decline in 
FEV1 seen among the ``dropout'' subgroup of Vermont granite 
workers was 4 ml per 1,000 [micro]g/m\3\-year (4 ml per mg/m\3\-year) 
of exposure to respirable granite dust. By comparison, FEV1 
declines at a rate of 10 ml/year from smoking one pack of cigarettes 
daily. From their study of foundry workers, Hertzberg et al. (2002) 
reported a 1.1 ml/year decline in FEV1 and a 1.6 ml/year 
decline in FVC for each 1,000 [micro]g/m\3\-year of respirable 
crystalline silica exposure after controlling for ethnicity and 
smoking. From these rates of decline, they estimated that exposure to 
100 [micro]g/m\3\ of respirable crystalline silica for 40 years would 
result in a total loss of FEV1 and FVC that was less than, 
but still comparable to, smoking a pack of cigarettes daily for 40 
years. Hertzberg et al. (2002) also estimated that exposure to the 
existing MSHA standards (100 [micro]g/m\3\) for 40 years would increase 
the risk of developing abnormal FEV1 or FVC by factors of 
1.68 and 1.42, respectively.
    OSHA reviewed cross-sectional studies that described relationships 
between lung function loss and respirable crystalline silica exposure 
(or exposure measurement surrogates such as tenure). The results of 
these studies were like those of the longitudinal studies previously 
discussed. In several studies, respirable crystalline silica exposure 
was found to reduce lung function of:
    (1) White South African gold miners (Hnizdo et al., 1990),
    (2) Black South African gold miners (Irwig and Rocks, 1978; Cowie 
and Mabena, 1991),
    (3) Respirable crystalline silica-exposed workers in Quebec 
(B[eacute]gin et al., 1995),
    (4) Rock drilling and crushing workers in Singapore (Ng et al., 
1992b),
    (5) Granite shed workers in Vermont (Theriault et al., 1974a,b),
    (6) Aggregate quarry workers and coal miners in Spain (Montes et 
al., 2004a,b),
    (7) Concrete workers in the Netherlands (Meijers et al., 2001),
    (8) Chinese refractory brick manufacturing workers in an iron-steel 
plant (Wang et al., 1997),
    (9) Chinese gemstone workers (Ng et al., 1987b),
    (10) Hard-rock miners in Manitoba, Canada (Manfreda et al., 1982) 
and in Colorado (Kreiss et al., 1989),
    (11) Pottery workers in France (Neukirch et al., 1994),
    (12) Potato sorters in the Netherlands (Jorna et al., 1994),
    (13) Slate workers in Norway (Suhr et al., 2003), and
    (14) Men in a Norwegian community with years of occupational 
exposure to respirable crystalline silica (quartz) (Humerfelt et al., 
1998).
    OSHA (2013b) recognized that many of these studies found that 
pulmonary function impairment: (1) can occur in respirable crystalline 
silica-exposed workers without silicosis, (2) was still observable when 
controlling for silicosis in the analysis, and (3) was related to the 
magnitude and duration of respirable crystalline silica exposure, 
rather than to the presence or severity of silicosis. Many other 
studies described by OSHA (2013b) have also

[[Page 28242]]

found a relationship between respirable crystalline silica exposure and 
lung function impairment, including IARC (1997), the ATS (1997), and 
Hnizdo and Vallyathan (2003).
    MSHA reviewed the studies and concludes that there is an exposure-
response relationship between respirable crystalline silica and the 
impairment of lung function. MSHA also concludes that that the effect 
of tobacco smoking on this relationship may be additive or synergistic, 
and that workers who were exposed to respirable crystalline silica, but 
did not show signs of silicosis, may also have pulmonary function 
impairment. MSHA's conclusions are consistent with OSHA's findings from 
its literature review.
3. Lung Cancer
    Commenters from United Steelworkers (USW), American Industrial 
Hygiene Association (AIHA), and Vanderbilt Minerals, agreed with MSHA's 
conclusion that miners exposed to respirable crystalline silica have an 
increased risk of lung cancer (Document ID 1447; 1351; 1419). The AIHA 
also cited research by the International Agency for Research on Cancer 
(IARC) as documenting the health risks from inhalation of respirable 
crystalline silica, specifically cancers of the lung, stomach, and 
esophagus (Document ID 1351). MSHA agrees with this comment for the 
reasons discussed below.
a. Lung Cancer
    Lung cancer, an irreversible and usually fatal disease, is a type 
of cancer that forms in lung tissue. MSHA has found that the scientific 
literature supports that respirable crystalline silica exposure 
significantly increases the risk of lung cancer mortality among miners. 
This determination is consistent with the conclusions of other 
government and public health organizations, including the ATS (1997), 
the IARC (1997, 2012), the NTP (2000, 2016), NIOSH (2002b), and the 
ACGIH (2010), which have classified respirable crystalline silica as a 
``known human carcinogen.'' The Agency's determination also is 
supported by epidemiological literature, encompassing more than 85 
studies of occupational cohorts from more than a dozen industrial 
sectors including: granite/stone quarrying and processing 
(Gu[eacute]nel et al., 1989a,b; Costello et al., 1995; Carta et al., 
2001; Attfield and Costello, 2004), industrial sand (Sanderson et al., 
2000; Hughes et al., 2001; McDonald et al., 2001, 2005; Rando et al., 
2001; Steenland and Sanderson, 2001), MNM mining (Hessel et al., 1986, 
1990; Hnizdo and Sluis-Cremer, 1991; Meijers et al., 1991; Chen et al., 
1992, 2006, 2012; McLaughlin et al., 1992; Hua et al., 1994; Roscoe et 
al., 1995; Steenland and Brown, 1995a; Reid and Sluis-Cremer, 1996; 
Hnizdo et al., 1997; deKlerk and Musk, 1998; Finkelstein, 1998; Chen 
and Chen, 2002; Schubauer-Berigan et al., 2009; Liu et al., 2017a; Wang 
et al., 2020a,b, 2021), coal mining (Meijers et al., 1988; Miyazaki and 
Une, 2001; Miller et al., 2007; Miller and MacCalman, 2010; Tomaskova 
et al., 2012, 2017, 2020, 2022; Graber et al., 2014a,b; Kurth et al., 
2020), pottery (Winter et al., 1990; McLaughlin et al., 1992; McDonald 
et al., 1995), ceramic industries (Starzynski et al., 1996), 
diatomaceous earth (Checkoway et al., 1993, 1996, 1997, 1999; Seixas et 
al., 1997; Rice et al., 2001), and refractory brick industries 
(cristobalite exposures) (Dong et al., 1995).
    One commenter stated that the work of Steenland and Sanderson 
should not be ``discounted'' and that Miller and MacCalman ``did not 
report on occupational exposure monitoring concentrations'' reported by 
Steenland and Sanderson (Document ID 1351).
    MSHA chose Miller and MacCalman (2010) rather than the Steenland et 
al. (2001a) pooled cohort study for its lung cancer mortality risk 
model but has not discounted the study of Steenland and Sanderson. MSHA 
has cited the Steenland and Sanderson (2001) study at multiple points 
in the final standalone Health Effects document and has also cited 
other investigations from both researchers. The Miller and MacCalman 
(2010) study contained detailed time-exposure measurements of both 
respirable crystalline silica (quartz) and total mine dust, detailed 
individual work histories, and individual smoking histories. Further 
discussion regarding the selection of the risk model of Miller and 
MacCalman (2001) is located in the standalone FRA document.
    The strongest evidence comes from the worldwide cohort and case-
control studies reporting excess lung cancer mortality among workers 
exposed to respirable crystalline silica in various industrial sectors. 
This evidence is confirmed by the ten-cohort pooled case-control 
analysis by Steenland et al. (2001a); the more recent pooled case-
control analysis of seven European countries by Cassidy et al. (2007); 
and two national death certificate registry studies, Calvert et al. 
(2003) in the United States and Pukkala et al. (2005) in Finland.
    Recent studies examined lung cancer mortality among coal and non-
coal miners (Meijers et al., 1988, 1991; Starzynski et al., 1996; 
Miyazaki and Une, 2001; Attfield and Kuempel, 2008; Tomaskova et al., 
2012, 2017, 2020, 2022; Graber et al., 2014a,b; NIOSH, 2019a; Kurth et 
al., 2020). These studies also discuss the associations between RCMD 
and respirable crystalline silica exposures with lung cancer in coal 
mining populations. Furthermore, the findings of these newer studies 
are consistent with the conclusion of OSHA's final Quantitative Risk 
Assessment (QRA) (2016a) that respirable crystalline silica is a human 
carcinogen. MSHA concludes that miners, both MNM and coal miners, are 
at risk of developing lung cancer due to their occupational exposure to 
respirable crystalline silica.
    In addition, based on its review of the health effects literature, 
MSHA has determined that radiographic silicosis is a marker for lung 
cancer risk. Reducing exposure to levels that lower the silicosis risk 
would reduce the lung cancer risk to exposed miners (Finkelstein, 1995, 
2000; Brown, 2009). MSHA has also found that, based on the available 
epidemiological and animal data, respirable crystalline silica causes 
lung cancer (IARC, 2012; RTECS, 2016; ATSDR, 2019). Miners who inhale 
respirable crystalline silica over time are at increased risk of 
developing silicosis and lung cancer (Greaves, 2000; Erren et al., 
2009; Tomaskova et al., 2017, 2020, 2022).
    Other toxicity studies (non-animal) provide additional evidence of 
the carcinogenic potential of respirable crystalline silica. Studies 
using DNA exposed directly to freshly fractured respirable crystalline 
silica demonstrate that respirable crystalline silica directly 
increases DNA breakage. Cell culture research has investigated the 
processes by which respirable crystalline silica disrupts normal gene 
expression and replication. Studies have demonstrated that chronic 
inflammatory and fibrotic processes resulting in oxidative and cellular 
damage may lead to neoplastic changes in the lung (Goldsmith, 1997). In 
addition, the biologically damaging physical characteristics of 
respirable crystalline silica and its direct and indirect genotoxicity 
support MSHA's determination that respirable crystalline silica is an 
occupational carcinogen (Borm and Driscoll, 1996; Schins et al., 2002).
b. Cancers of Other Sites
    In addition to examining studies on lung cancer, MSHA has reviewed 
studies examining the relationship between respirable crystalline 
silica exposure and cancers at other sites. MSHA has reviewed the 
studies

[[Page 28243]]

examined by OSHA, together with additional studies focusing on miners' 
exposure, and has concluded (as OSHA did) that there is insufficient 
evidence to demonstrate a causal relationship between respirable 
crystalline silica exposure and other (non-lung) cancer mortality. MSHA 
notes that OSHA reviewed mortality studies, on cancer of the larynx and 
the digestive system, including the stomach and esophagus, and found 
that studies suggesting a dose-response relationship were too limited 
in terms of size, study design, or potential for confounding variables, 
to be conclusive. In addition, NIOSH (2002b) in their respirable 
crystalline silica review concluded that no association has been 
established between respirable crystalline silica exposure and excess 
mortality from cancer at other sites. The following summarizes the 
studies reviewed with inconclusive findings.
(1) Laryngeal Cancer
    MSHA reviewed three lung cancer studies also discussed by OSHA 
(2013b) which suggested an association between respirable crystalline 
silica exposure and increased mortality from laryngeal cancer (Davis et 
al., 1983; Checkoway et al., 1997; McDonald et al., 2001). However, a 
small number of cases were reported in those studies, and the 
researchers were unable to determine a statistically significant 
effect. Therefore, MSHA found that there was little evidence of an 
association based on these studies. OSHA also reached this conclusion.
(2) Gastric (Stomach) Cancer
    MSHA reviewed the literature discussed by OSHA (2013b) to assess a 
potential relationship between respirable crystalline silica exposures 
and stomach cancers. OSHA concurred with observations made previously 
by Cocco et al. (1996) and in the NIOSH (2002b) respirable crystalline 
silica hazard review, which found that most epidemiological studies of 
respirable crystalline silica and stomach cancer did not sufficiently 
adjust for the effects of confounding factors. In addition, some of 
these studies were not properly designed to assess a dose-response 
relationship (Selikoff, 1978; Stern et al., 2001; Moshammer and 
Neuberger, 2004; Finkelstein and Verma, 2005) or did not demonstrate a 
statistically significant dose-response relationship (Tsuda et al., 
2001; Calvert et al., 2003). For these reasons, MSHA determined these 
studies were inconclusive in the context of this rulemaking.
(3) Esophageal Cancer
    MSHA has reviewed studies that focused on miners and concludes that 
the literature does not support attributing increased esophageal cancer 
mortality with exposure to respirable crystalline silica. The studies 
by Meijers et al. (1991) and Swaen et al. (1995) assessed mortality 
from esophageal cancer in Dutch underground coal miners. Meijers et al. 
(1991) reported an elevated standardized mortality ratio (SMR) of 396, 
which was not statistically significant. The SMR was based on two cases 
out of 334 confirmed pneumoconiosis cases followed through the end of 
1983 (case selection based on health screening between 1956-1960). 
Swaen et al. (1995) reported a SMR of 62 (95 percent CI: 25-127) based 
on seven cases out of 3,790 underground coal miners who were diagnosed 
with pneumoconiosis between 1956 and 1960. This result was not 
statistically significant.
    MSHA reviewed the studies presented by OSHA (2013b) and agrees with 
OSHA's conclusion that the literature does not support attributing 
increased esophageal cancer mortality to exposure to respirable 
crystalline silica. OSHA considered several studies that examined the 
relationship between respirable crystalline silica exposures and 
esophageal cancer and found that the studies were limited in terms of 
size, study design, or potential for confounding variables. Three 
nested case-control studies of Chinese workers demonstrated a dose-
response association between increased risk of esophageal cancer 
mortality and respirable crystalline silica exposure (Pan et al., 1999; 
Yu et al., 2005; Wernli et al., 2006). Other studies also indicated 
elevated rates of esophageal cancer mortality with respirable 
crystalline silica exposure (Xu et al., 1996a; Tsuda et al., 2001). 
However, OSHA (2013b) identified that in all studies, confounding due 
to other occupational exposures was possible. Additionally, two large 
national mortality studies in Finland and the United States did not 
show a positive association between respirable crystalline silica 
exposure and esophageal cancer mortality (Calvert et al., 2003; 
Weiderpass et al., 2003).
(4) Other Sites
    MSHA's review of additional studies specific to miners further 
establishes that respirable crystalline silica exposure increases the 
risk of lung cancer, although there is insufficient evidence to 
demonstrate a causal relationship between respirable crystalline silica 
exposure and other (non-lung) cancer mortalities. Specifically, MSHA 
concludes that the epidemiological literature is not sufficient to 
conclude that there is an association between respirable crystalline 
silica exposures and increased cancer of the larynx, gastric cancer 
mortality, or esophageal cancer mortality.
    MSHA's conclusion is consistent with OSHA's conclusion. Overall, 
OSHA concluded that there was insufficient evidence of an association 
between silica exposure and cancer at sites other than the lungs. OSHA 
included a health literature review by NIOSH (2002b) that examined 
effects potentially associated with respirable crystalline silica 
exposure; that review identified only infrequent reports of 
statistically significant excesses of deaths for other cancers. Cancer 
studies have been reported on the following organs/systems: salivary 
gland, liver, bone, pancreas, skin, lymphopoietic or hematopoietic, 
brain, and bladder (see NIOSH, 2002b for full bibliographic 
references). However, the findings were not observed consistently among 
epidemiological studies, and NIOSH (2002b) concluded that no 
association has been established between these cancers and respirable 
crystalline silica exposure. OSHA concurred with NIOSH that these 
isolated reports of excess cancer mortality were insufficient to 
determine the role of respirable crystalline silica exposure.
    MSHA has reviewed the studies cited by OSHA and agrees with OSHA's 
conclusion. MSHA's review of additional studies specific to miners 
further establishes that respirable crystalline silica exposure 
increases the risk of lung cancer, though there is insufficient 
evidence to demonstrate a causal relationship between respirable 
crystalline silica exposure and other (non-lung) cancer mortalities.
4. Renal Disease
    MSHA received two comments related to MSHA's conclusions related to 
renal disease. The AIHA agreed that silica probably causes renal 
disease, quoting a paper by Steenland (2005b) (Document ID 1351). In 
contrast, the NSSGA stated that it was unclear whether renal disease is 
causally related to occupational crystalline silica exposure, citing a 
2017 German Federal Institute for Occupational Safety and Health 
systematic review that conducted a meta-analysis on respirable 
crystalline silica and non-malignant renal disease (M[ouml]hner et al., 
2017) (Document ID 1448).

[[Page 28244]]

    MSHA acknowledges that some studies have not found associations 
between respirable crystalline silica exposures and renal disease; 
however, those studies are generally statistically underpowered, 
meaning that their sample sizes are too small to detect even some 
substantial health effects. In contrast, as discussed below, studies 
with large cohort sizes and well-documented, validated job-exposure 
matrices found statistically significant effects on renal disease. MSHA 
reviewed the study by M[ouml]hner et al. (2017) and found that it was 
not suitable for inclusion in the literature review. The selection 
terms used by M[ouml]hner et al. (2017) appear to be overly limiting 
and did not appear to capture many of the studies that were included in 
MSHA's previous standalone Health Effects document published with its 
proposed silica rule (e.g., Gregorini et al., 1993; Hotz et al., 1995; 
Fenwick and Main, 2000; Rosenman et al., 2000; Kurth et al., 2020). 
MSHA also notes that several studies included in the review by 
M[ouml]hner et al. (2017) were already cited in MSHA's previous 
standalone Health Effects document published with its proposed silica 
rule (e.g., Koskela et al., 1987; Brown et al., 1997; Checkoway et al., 
1997; Calvert et al., 2003; Brown and Rushton, 2005b).
    Renal disease is characterized by the loss of kidney function and, 
in the case of ESRD, a permanent loss of kidney function leading to the 
need for a regular course of long-term dialysis or a kidney transplant 
to maintain life. MSHA reviewed a wide variety of longitudinal and 
mortality epidemiological studies, including case series, case-control, 
and cohort studies, as well as case reports, and concludes that there 
is substantial evidence in the literature suggesting that occupational 
exposures to respirable crystalline silica exposure increases the risk 
of morbidity and mortality related to ESRD. However, MSHA notes that 
the available literature on respirable crystalline silica exposures and 
renal disease in coal miners is less conclusive than the literature 
related to MNM miners.
    Epidemiological studies have found statistically significant 
associations between occupational exposure to respirable crystalline 
silica and chronic renal disease (e.g., Calvert et al., 1997), sub-
clinical renal changes, including proteinuria and elevated serum 
creatinine (e.g., Ng et al., 1992a; Hotz et al., 1995; Rosenman et al., 
2000), ESRD morbidity (e.g., Steenland et al., 1990), ESRD mortality 
(Steenland et al., 2001b, 2002a), and Wegener's granulomatosis (now 
known as granulomatosis with polyangiitis, GPA), which is severe injury 
to the glomeruli that, if untreated, rapidly leads to renal failure 
(Nuyts et al., 1995). The pooled analysis conducted by Steenland et al. 
(2002a) is particularly convincing because it involved a large number 
of workers from three combined cohorts and had well-documented, 
validated job exposure matrices. Steenland et al. (2002a) found a 
positive and monotonic exposure-response trend for both multiple-cause 
mortality and underlying cause data. MSHA has determined that the 
underlying data from Steenland et al. (2002a) are sufficient to provide 
useful estimates of risk.
    Possible mechanisms suggested for respirable crystalline silica-
induced renal disease include: (1) a direct toxic effect on the kidney, 
(2) a deposition in the kidney of immune complexes (e.g., 
Immunoglobulin A (IgA), an antibody blood protein) in the kidney 
following respirable crystalline silica-related pulmonary inflammation, 
and (3) an autoimmune mechanism (Gregorini et al., 1993; Calvert et 
al., 1997). Steenland et al. (2002a) demonstrated a positive exposure-
response relationship between respirable crystalline silica exposure 
and ESRD mortality.
    Overall, MSHA determines that respirable crystalline silica 
exposure in mining increases the risk of renal disease.
5. Autoimmune Disease
    Two commenters--AIHA and National Coalition of Black Lung and 
Respiratory Disease Clinics (hereafter referred to as ``Black Lung 
Clinics'')--agreed with MSHA's finding that there is evidence of a 
relationship between respirable crystalline silica exposure and 
autoimmune diseases (Document ID 1351; 1410). The Black Lung Clinics 
also qualified that there is insufficient data to model the risk of 
disease (Document ID 1410). This is consistent with MSHA's conclusion 
that there is a casual association between occupational exposure to 
respirable crystalline silica and the development of systematic 
autoimmune diseases in miners; however, there are no studies available 
to date that can be used to model respirable crystalline silica-
exposure risk of autoimmune diseases in the Agency's risk analysis.
    Autoimmune diseases occur when the immune system mistakenly attacks 
healthy tissues within the body, causing inflammation, swelling, pain, 
and tissue damage. Examples of autoimmune diseases include autoimmune 
rheumatic diseases, sarcoidosis and seropositive rheumatoid arthritis 
(RA), Crohn's disease (CD), ulcerative colitis (UC), systemic lupus 
erythematosus (SLE), scleroderma, and systemic sclerosis (SSc). Some 
studies reviewed by MSHA suggest a casual association between 
occupational exposure to respirable crystalline silica and the 
development of systematic autoimmune diseases, particularly RA.
    Wallden et al. (2020) found that respirable crystalline silica 
exposure is correlated with an increased risk of developing UC, and 
that the risk increases with duration of exposure (work tenure) and the 
level of exposure. This effect was especially significant in men. 
Schmajuk et al. (2019) found that RA was significantly associated with 
coal mining and other non-coal occupations exposed to respirable 
crystalline silica. Vihlborg et al. (2017) found a significant 
increased risk of seropositive RA with high exposure (>48 [micro]g/
m\3\) to respirable crystalline silica when compared to rates for 
individuals with lower or no exposure. They examined detailed exposure-
response relationships across four different groups, each of which was 
exposed to a different concentration of respirable crystalline silica 
(quartiles): <23 [micro]g/m\3\, 24 to 35 [micro]g/m\3\, 36 to 47 
[micro]g/m\3\, and >48 [micro]g/m\3\. However, these researchers did 
not report the risk of sarcoidosis (a condition in which groups of 
cells in the immune system form granulomas in various organ systems) 
and seropositive RA in relation to respirable crystalline silica 
exposure using models that could be used in MSHA's risk analysis. In 
addition, the meta-analysis of 19 published case-control and cohort 
studies on scleroderma by Rubio-Rivas et al. (2017) found statistically 
significant risks among individuals exposed to respirable crystalline 
silica, solvents, silicone, breast implants, epoxy resins, pesticides, 
and welding fumes, but did not provide detailed quantitative exposure 
information that could be used in the risk analysis.
    Based on its literature review, MSHA concludes that there is a 
causal association between occupational exposure to respirable 
crystalline silica and the development of systemic autoimmune diseases 
in miners, but that no studies are available to date that can be used 
to model respirable crystalline silica-exposure risk in a risk 
analysis.

D. Conclusion

    MSHA concludes that exposure to respirable crystalline silica 
causes silicosis (acute, accelerated, chronic, and PMF), NMRD 
(including COPD), lung cancer, and renal disease. Each of these effects 
is exposure-dependent, potentially chronic, irreversible, potentially 
disabling, and can be fatal.

[[Page 28245]]

Respirable crystalline silica exposure is also linked to the 
development of some autoimmune disorders through inflammatory pathways.
    The health effects literature, including peer-reviewed medical, 
toxicological, public health, and other related disciplinary 
publications, is robust and compelling. It shows that miners exposed to 
the existing respirable crystalline silica exposure limits of 100 
[micro]g/m\3\ still have an unacceptable amount of excess risk, for 
developing and dying from diseases related to their occupational 
respirable crystalline silica exposures.
    MSHA is entrusted with ensuring that ``no miner will suffer 
material impairment of health or functional capacity even if such miner 
has regular exposure to the hazards dealt with by such standard for the 
period of his working life'' (30 U.S.C. 811(a)(6)(A)). The Agency 
believes that when the final rule is implemented and enforced 
effectively, it will reduce the rate of silicosis and other diseases 
caused by respirable crystalline silica exposure and will substantially 
improve miners' lives.

VI. Final Risk Analysis Summary

    MSHA's FRA quantifies risks associated with five specific health 
outcomes identified in the standalone Health Effects document: 
silicosis morbidity and mortality, and mortality from NMRD, lung 
cancer, and ESRD. This section serves as a summary of the standalone 
FRA document, which is placed into the rulemaking docket for the MSHA 
respirable crystalline silica rulemaking (RIN 1219-AB36, Docket No. 
MSHA-2023-0001) and is available at Regulations.gov.
    MSHA developed an FRA to support its risk determinations and to 
quantify the health risk to miners exposed to respirable crystalline 
silica under the existing exposure limits for MNM and coal miners, at 
the new PEL of 50 [micro]g/m\3\, and at the action level of 25 
[micro]g/m\3\.
    This analysis addresses three questions related to the final rule:
    (1) whether potential health effects associated with existing 
exposure conditions constitute material impairment to any miner's 
health or functional capacity;
    (2) whether existing exposure conditions place miners at risk of 
incurring any material impairment if regularly exposed for the period 
of their working life; and
    (3) whether the final rule will reduce those risks.
    To answer these questions, MSHA relied on the large body of 
research on the health effects of respirable crystalline silica and 
published, peer-reviewed, quantitative risk assessments that describe 
the risk of exposed workers to silicosis mortality and morbidity, NMRD 
mortality, lung cancer mortality, and ESRD mortality. These 
quantitative risk assessments are based on several studies of 
occupational cohorts in a variety of industrial sectors. The underlying 
studies are described in the standalone Health Effects document and are 
summarized in Section V. Health Effects Summary.
    Based on its analysis, MSHA found that, once the current mining 
workforce is replaced with new entrants to the mining industry so that 
all working miners and retired miners have been exposed only under the 
new PEL, the final rule will decrease lifetime excess deaths by at 
least 1,067 and will decrease lifetime excess cases of non-fatal 
silicosis by at least 3,746 among the working and future retired miner 
population. In the FRA, MSHA also increases its estimate of the number 
of miners who will benefit from this rule to include future retired 
miners. While the Preliminary Risk Analysis (PRA) did consider 
reductions in excess risk during years of retirement, the PRA did not 
account for the fact that future retired miners are among the 
population that will benefit from the rule. Once the entire mining 
workforce, including future retired miners, has worked only under the 
new PEL (i.e., 60 years after the start of implementation of the rule), 
both the retired and working miners will experience fewer deaths and 
illnesses. The FRA updates benefit estimates to account for all 
lifetime excess cases that will be avoided among all working miners and 
future retired miners. It is important to note that the FRA (as well as 
the FRIA, discussed below in Section IX) only monetizes benefits to 
future retired miners. The FRA methodology does not attribute any 
health benefits to individuals who retired before the start of 
implementation of the final rule.
    This summary highlights the main findings from the FRA, briefly 
describes how they were derived, and directs readers interested in more 
detailed information to corresponding sections of the standalone FRA 
document.

A. Summary of MSHA's Final Risk Analysis Process and Methods

    MSHA evaluated the literature and selected an exposure-response 
model for each of the five health endpoints--silicosis morbidity, 
silicosis mortality, NMRD mortality, lung cancer mortality, and ESRD 
mortality. The selected exposure-response models were used to estimate 
lifetime excess risks and lifetime excess cases among the current 
population of working and the future population of retired MNM and coal 
miners based on real exposure conditions, as indicated by the samples 
in the compliance sampling datasets.
    MSHA's FRA is largely based on the methodology and findings from 
OSHA's 2013 preliminary quantitative risk assessment (PQRA), OSHA's 
2016 final quantitative risk assessment (QRA), and the associated 
analysis of health effects in connection with OSHA's promulgation of a 
rule setting PELs for workplace exposure to respirable crystalline 
silica. OSHA's PQRA presented quantitative relationships between 
respirable crystalline silica exposure and multiple health endpoints. 
Following multiple legal challenges, the U.S. Court of Appeals for the 
D.C. Circuit rejected challenges to OSHA's risk assessment methodology 
and its findings on different health risks. N. Am.'s Bldg. Trades 
Unions v. OSHA, 878 F.3d 271, 283-89 (D.C. Cir. 2017).
    MSHA's FRA presents detailed quantitative analyses of health risks 
over a range of exposure concentrations that have been observed in MNM 
and coal mines. MSHA applied exposure-response models to estimate the 
respirable crystalline silica-related risk of material impairment of 
health or functional capacity of miners exposed to respirable 
crystalline silica at three levels--(1) the existing standards, (2) the 
new PEL, and (3) the action level. As in past MSHA rulemakings, MSHA 
estimated and compared lifetime excess risks associated with exposures 
at the existing and new PEL (and at the action level) over a miner's 
full working life of 45 years and 15 years of retirement.
    MSHA's FRA is also based on a compilation of miner exposure data to 
respirable crystalline silica. For the MNM sector, MSHA evaluated 
57,769 valid respirable dust samples collected between January 2005 and 
December 2019; and for the coal sector, MSHA evaluated 63,127 valid 
respirable dust samples collected between August 2016 and July 2021. 
The compiled data set characterizes miners' exposures to respirable 
crystalline silica in various locations (i.e., underground, surface), 
occupations (e.g., drillers, underground miners, equipment operators), 
and commodities (e.g., metal, nonmetal, stone, crushed limestone, sand 
and gravel, and coal). MSHA enforcement sampling indicates a wide range 
of exposure concentrations. These include exposures from below the 
action level (25 [micro]g/m\3\) to above the existing standards (100 
[micro]g/m\3\ in MNM standards and 100 [micro]g/m\3\ MRE in coal 
standards,

[[Page 28246]]

which is approximately 85.7 [micro]g/m\3\ ISO).18 19

    \18\ As discussed in the FRA, the existing PEL for coal is 100 
[mu]g/m\3\ MRE, measured as a full-shift time-weighted average 
(TWA). To calculate risks consistently for both coal and MNM miners, 
the FRA converts the MRE full-shift TWA concentrations experienced 
by coal miners to ISO 8-hour TWA concentrations. (See Section 4 of 
the standalone FRA document for a full explanation.) The equation 
used to convert MRE full-shift TWA concentrations into ISO 8-hour 
TWA concentrations is:
[GRAPHIC] [TIFF OMITTED] TR18AP24.077

    Exposures at TWA 100 [micro]g/m\3\ MRE and SWA 85.7 [micro]g/
m\3\ ISO are only equivalent when the sampling duration is 480 
minutes (eight hours). However, for the sake of simplicity and for 
comparison purposes, the risk analysis approximates exposures at the 
existing coal exposure limit of 100 MRE [micro]g/m\3\ as 85.7 
[micro]g/m\3\ ISO. Thus, ISO concentration values (measured as an 8-
hour TWA) were used as the exposure metric when (a) calculating risk 
under the assumption of full compliance with the existing standards 
and (b) calculating risk under the assumption that no exposure 
exceeds the new PEL of 50 [mu]g/m\3\. To simulate compliance among 
coal miners at the existing exposure limit, exposures were capped at 
85.7 [mu]g/m\3\ measured as an ISO 8-hour TWA.
    \19\ A sample-specific exposure limit is calculated for each 
sample based on the polymorphs present. For samples with >1% quartz 
by mass, the formula is:
[GRAPHIC] [TIFF OMITTED] TR18AP24.078

    When quartz is the only respirable crystalline silica polymorph 
in the sample, the existing MNM standard limits respirable 
crystalline silica exposures to 100 [micro]g/m\3\ or less in MNM 
operations. Cristobalite exposures are currently limited to 50 
[micro]g/m\3\ or less when cristobalite is the only polymorph 
present, and the same is true for tridymite \19\. When more than one 
polymorph is present in the same sample, then a Threshold Limit 
Value for mixtures is used.

    One commenter (a safety compliance consultant) stated that the \20\ 
2005-2019 MNM respirable dust samples analyzed for respirable 
crystalline silica show a downward trend in average annual rates of 
overexposure and requested access to data for 2020-2022 (Document ID 
1383). In response, MSHA notes that the 2020-2022 data may be skewed by 
the reduction in mining during the COVID-19 pandemic and would 
therefore bias the analysis. Further, 2019 is recent enough to 
adequately capture the current exposure profile of working miners.
---------------------------------------------------------------------------

    \20\
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    In addition, commenters from the United Mine Workers of America 
(UMWA), the Black Lung Clinics, and the Appalachian Citizens' Law 
Center (ACLC) expressed concern that MSHA used coal mine dust data from 
2016-2021, a historically low period for quartz levels in coal mining, 
according to the commenters (Document ID 1398; 1410; 1445). The ACLC 
asserted that, as a result, the estimate of avoided illnesses and 
deaths in MSHA's PRA is low and urged the Agency to include a longer 
history of coal dust sampling data when estimating miners' future 
exposures (Document ID 1445). As discussed below, MSHA chose this time 
period to account for the 2014 RCMD Standard, which came into full 
effect in 2016. The ACLC also stated that, because the 2014 RCMD 
Standard does not directly regulate respirable crystalline silica, 
there is no justification for excluding prior sampling data (Document 
ID 1445).
    MSHA believes the 2014 RCMD Standard impacted respirable 
crystalline silica exposures, in part because (a) the coal dust 
exposure limit is based on a formula that reduces the limit when the 
respirable crystalline silica content exceeds 100 [micro]g/m\3\, and 
(b) measures that coal mine operators may have taken to reduce 
exposures to coal dust under that rule would have also reduced 
exposures to other respirable hazards including crystalline silica. 
Using more recent coal exposure data from 2016-2021 thus avoids 
possibly attributing benefits from the 2014 RCMD Standard to this rule. 
However, MSHA agrees that if respirable crystalline silica 
concentrations were to rise in the future--while remaining within the 
limits of the 2014 RCMD Standard and complying with all existing 
regulations--there would be additional unquantified benefits from the 
final rule.\21\ For example, some researchers have attributed the 
increase in pneumoconiosis prevalence among miners since the 1990s to 
respirable crystalline silica (Cohen et al., 2022; Hall et al., 2020b). 
Cohen et al. (2022) states that respirable crystalline silica has 
become more concentrated due to improvements in mining equipment and 
processing technology, which allow ``recovery of thin coal seams, which 
involves the extraction of large quantities of surrounding rock strata 
that can contain crystalline silica.'' The possibility that respirable 
crystalline silica exposure could increase in the future in the absence 
of this rule underscores the rule's importance.
---------------------------------------------------------------------------

    \21\ In the analyzed coal compliance data from 2016 through 
2021, only 6 percent of samples are above the new PEL of 50 [mu]g/
m\3\. Currently regulation provides protections to keep samples 
below 85.7 [mu]g/m\3\, but it is insufficient to prevent increases 
in the proportion of concentrations in the range of 50 to 85.7 
[mu]g/m\3\. The possibility of such an increase further necessitates 
this rule.
---------------------------------------------------------------------------

    The primary results of the FRA are the calculated number of deaths 
and illnesses avoided assuming full compliance after implementation of 
MSHA's final rule. These calculations were performed for non-fatal 
silicosis illnesses (morbidity) and for deaths (mortality) due to 
silicosis, lung cancer, NMRD, and ESRD. For each health outcome, the 
reduced number of illnesses or deaths is calculated as the difference 
between (a) the number of excess illnesses and deaths currently 
occurring in the industry, assuming mines fully comply with the 
previous standards (100 [micro]g/m\3\ for MNM and 85.7 [micro]g/m\3\ 
ISO for coal) and (b) the number of excess deaths and illnesses 
expected to occur following implementation of the final rule, which 
includes a new PEL of 50 [micro]g/m\3\ for a full-shift exposure, 
calculated as an 8-hour TWA.
    Excess risks and cases were estimated under two scenarios: (a) a 
Baseline scenario where all exposures were capped at 100 [mu]g/m\3\ for 
MNM miners and at 85.7 [mu]g/m\3\ for coal miners, and (b) a new PEL 50 
[mu]g/m\3\ scenario where all risks were capped at the new PEL of 50 
[mu]g/m\3\ for both MNM and coal miners. The difference between the two 
scenarios yields the estimated reduction in lifetime excess risks and 
in lifetime excess cases due to the new PEL.

[[Page 28247]]

    To calculate excess risks, MSHA grouped MNM miners into the 
following exposure intervals: <=25, >25 to <=50, >50 to <=100, >100 to 
<=250, >250 to <=500, and >500 [mu]g/m\3\. MSHA grouped coal miners 
into the following exposure intervals: <=25, >25 to <=50, >50 to 
<=85.7, >85.7 to <=100, >100 to <=250, >250 to <=500, and >500 [mu]g/
m\3\. MSHA calculated the median of all exposure samples in each 
exposure interval and assumed the population of miners is distributed 
across the exposure intervals in proportion to the number of exposure 
samples from the compliance dataset in each interval. Then, miners were 
assumed to encounter constant exposure at the median value of their 
assigned exposure interval. MSHA adjusted the annual cumulative 
exposure by a full-time equivalency (FTE) factor to account for the 
fact that miners may experience more or less than 2,000 hours of 
exposure per year. MSHA calculated the FTE adjustment factor as the 
weighted average of the miner (excluding contract miner) FTE ratio 
(0.99 for MNM and 1.14 for coal) and the contract miner FTE ratio (0.59 
for MNM and 0.64 for coal), where the weights are the number of miners 
[150,928 for MNM miners (excluding contract miners), 60,275 for MNM 
contract miners, 51,573 for coal miners (excluding contract miners), 
and 22,003 for coal contract miners]. For example, the weighted average 
FTE ratio for MNM is (0.987 x 150,928 + 0.591 x 60,275)/(150,928 + 
60,275) = 0.87 and is (1.139 x 51,573 + 0.636 x 22,003)/(51, 573 + 
22,003) = 0.99 for coal.
    MSHA uses weighted average FTE ratios to account for the fact that 
contract miners may experience lower exposures per year from mining. 
However, this underestimates the cumulative exposures that miners 
(excluding contract miners) experience. The average coal miner 
(excluding contract miners), for example, works approximately 2,280 
hours per year, which equates to an average shift of over 9.1 hours 
when assuming 250 working days per year.\22\ Additionally, the studies 
the FRA relied on to model excess risks define a full working year as 
1,740 hours, in instances where such a definition is given (Buchanan et 
al., 2003; Miller and MacCalman, 2010). Based on these studies' 
definition of a year, MNM miners (excluding contract miners) have an 
FTE ratio of 1.13 and coal miners (excluding contract miners) have an 
FTE ratio of 1.31. Additionally, the contract miner FTE ratios likely 
have some negative bias since any individual who works for multiple 
contracting companies is counted multiple times in the data, inflating 
the denominator in the FTE ratio calculation. MSHA also notes that the 
contract miner FTE ratios may underrepresent the true overall 
cumulative exposures since contract miners may have other jobs 
involving exposure to respirable crystalline silica (e.g., in 
construction or the oil and gas industry).
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    \22\ The fact that miners work over 8-hour shifts is also 
supported by MSHA's compliance data, which show an average shift 
duration of approximately 9.2 hours for MNM (MSHA, 2022a) and 9.6 
hours for coal (MSHA, 2022b). These values differ from the average 
hours per day implied by the FTE ratios because the compliance data 
is only a sample of full shifts, whereas the FTE data is based on 
comprehensive reporting of all full-time and part-time shifts.
---------------------------------------------------------------------------

    MSHA calculated excess risk, which refers to the additional risk of 
disease and death attributable to exposure to respirable crystalline 
silica. For silicosis morbidity, MSHA used an exposure-response model 
that directly yields the accumulated or lifetime excess risk of 
silicosis morbidity, assuming there is no background rate \23\ of 
silicosis in an unexposed (i.e., non-miner) group. For the four 
mortality endpoints (silicosis mortality, lung cancer mortality, NMRD 
mortality, and ESRD mortality), MSHA used cohort life tables to 
calculate excess risks, assuming all miners enter the workforce at the 
start of age 21, retire at the end of age 65, and do not live past the 
end of age 80. From the life tables, MSHA acquired the lifetime excess 
risk of mortality by summing the miner cohort's excess mortality risks 
in each year from age 21 through age 80. Life tables were also 
constructed for unexposed (i.e., non-miner) groups assumed to die from 
a given disease at typical rates for the U.S. male population. MSHA 
used 2018 data for all males in the U.S. (published by the National 
Center for Health Statistics, 2020b) to estimate (a) the disease-
specific mortality rates among unexposed males and (b) the all-cause 
mortality rates among both groups (exposed miners and unexposed non-
miners).
---------------------------------------------------------------------------

    \23\ Here, the ``background'' risk (or rate) refers to the risk 
of disease that the exposed person would have experienced in the 
absence of exposure to respirable crystalline silica. These 
background morbidity and mortality rates are measured using the 
disease-specific rates among the general population, which is not 
exposed to respirable crystalline silica.
---------------------------------------------------------------------------

    For a given scenario (either Baseline or New PEL 50 [mu]g/m\3\), 
MSHA constructed life tables in the manner described above, both for a 
miner cohort exposed to respirable crystalline silica and for an 
unexposed non-miner cohort. MSHA calculated excess risk of disease as 
the difference between the two cohorts' disease-specific mortality risk 
(due to silicosis, lung cancer, NMRD, or ESRD). MSHA determined the 
lifetime excess cases by multiplying the lifetime excess risk by the 
number of exposed miner FTEs (including contract miner FTEs). Risks and 
cases were calculated separately for each exposure interval listed 
above. Then, the lifetime excess cases were aggregated across all 
exposure intervals. MSHA calculated the final lifetime excess risks per 
1,000 miners in the full population of working and future retired 
miners by dividing the total number of lifetime excess cases by the 
total number of miners in the population (exposed at any interval). 
Finally, to estimate the risk reductions and avoided cases of illness 
due to the new PEL, MSHA compared the lifetime excess risks and 
lifetime excess cases across the two scenarios (Baseline and New PEL 50 
[mu]g/m\3\).
    In the PRA, MSHA underestimated the number of miners who will 
benefit from the proposed rule. Based on the 2019 Quarterly Employment 
Production Industry Profile (MSHA, 2019a) and the 2019 Quarterly 
Contractor Employment Production Report (MSHA, 2019b), the current 
number of working miner FTEs is estimated to be 184,615 for MNM and 
72,768 for coal. In the PRA, MSHA assumed excess cases of disease would 
be reduced only among these working miners. However, once the current 
mining workforce is replaced with new entrants to the mining industry 
so that the entire workforce has worked only under the new PEL for 
their 45 years of working life, the future mining workforce will 
experience fewer excess deaths and illnesses from exposure to 
respirable crystalline silica. The PRA's methodology did not include 
the number of future retired miners who will experience lower exposure 
for their working lives under the final rule and will continue to 
benefit during retirement, and therefore, the PRA underestimated the 
number of avoided lifetime excess cases attributable to the rule. In 
the FRA, the estimates are updated to account for all excess cases that 
will be avoided among not only working miners but also future retired 
miners. As discussed in greater detail in the FRA, the number of future 
retired miners who are expected to benefit from the rule can be 
calculated from the survival rates (which are computed in the life 
tables) and from the assumption that the mining workforces in MNM and 
coal will remain the same size as they are today.
    On the related question raised by the ACLC about whether new 
clinical data suggests that the PRA underestimated benefits of the 
lower PEL, MSHA

[[Page 28248]]

determines that the approach in the PRA is the appropriate one 
(Document ID 1445). The risk models that MSHA uses are exposure-
response models, originally selected through OSHA's peer review process 
and silica rulemaking, based on past clinical data on patients whose 
exposure history was known. Newer data from Black Lung Clinics can 
provide suggestive evidence of the risks, but because it is not yet 
incorporated into these peer-reviewed risk models, it cannot be 
included in this analysis as this commenter recommends.

B. Overview of Epidemiologic Studies

    MSHA reviewed extensive research on the health effects of 
respirable crystalline silica and quantitative risk assessments 
published in the peer-reviewed scientific literature regarding 
occupational exposure risks of illness and death from silicosis, NMRD, 
lung cancer, and ESRD. The standalone Health Effects document describes 
the specific studies reviewed by MSHA. Of the many studies evaluated, 
MSHA believes that the 13 studies used by OSHA (2013b) to estimate 
risks provide reliable estimates of the disease risk posed by miners' 
exposure to respirable crystalline silica. These studies are summarized 
in Table VI-1.
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[[Page 28250]]


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    Of these 13 studies, OSHA selected one per health endpoint for 
final modeling and estimation of lifetime excess risk and cases. 
Combining the five selected studies with the observed exposure data 
yields estimates of actual lifetime excess risks and lifetime excess 
cases among working and future retired miner populations based on real 
exposure conditions. Table VI-2 summarizes key characteristics of the 
models presented in the 13 studies from OSHA's PQRA, including the 
cohort that was investigated, the specific health endpoint (e.g., chest 
X-ray of category 2/1+), whether a lag between exposure and excess risk 
was included, and key model parameters. MSHA evaluated the evidence of 
OSHA's analysis of the 13 studies and the accompanying risks associated 
with exposure at 25, 50, 100, 250, and 500 [micro]g/m\3\. Thorough 
evaluation has led MSHA to determine that the studies OSHA selected 
still provide the best available epidemiological models (with the 
exception of lung cancer mortality). However, MSHA utilized the Miller 
and MacCalman (2010) study to estimate risks for lung cancer mortality. 
This study was included in OSHA's health effects assessment and PQRA 
but was published after OSHA completed much of its modeling for the 
PQRA. The following lists the studies used by MSHA for each health 
endpoint:
    Silicosis morbidity: Buchanan et al. (2003);
    Silicosis mortality: Mannetje et al. (2002b);
    NMRD mortality: Park et al. (2002);
    Lung cancer mortality: Miller and MacCalman (2010); and
    ESRD mortality: Steenland et al. (2002a).
    As explained in detail in the standalone FRA document, MSHA 
developed its risk estimates based on recent mortality data and certain 
assumptions that differed from those used by OSHA. Examples of these 
MSHA assumptions include a lifetime that ends at age 80, updated 
background mortality data and all-cause mortality, miner population 
sizes, and miner-specific full-time equivalents (FTEs).\24\
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    \24\ FTEs were used to adjust the cumulative exposure over a 
year based on the average number of hours that miners work.

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[[Page 28251]]

    MSHA's modeling has been done using life tables, in a manner 
consistent with OSHA's PQRA. In general, the life table is a technique 
that allows estimation of excess risk of disease-specific mortality 
while factoring in the probability of surviving to a particular age, 
assuming no exposure to respirable crystalline silica. This analysis 
accounts for competing causes of death, background mortality rates of 
disease, and the effect of the accumulation of risk due to elevated 
mortality rates in each year of a working life. For each cause of 
mortality, the selected study was used in the life table analysis to 
compute the increase in miners' disease-specific mortality rates 
attributable to respirable crystalline silica exposure.
    MSHA uses cumulative exposure (i.e., cumulative dose) to 
characterize the total exposure over a 45-year working life. Cumulative 
exposure is defined as the product of exposure duration and exposure 
intensity (i.e., exposure level). Cumulative exposure is the predictor 
variable in the selected exposure-response models.
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    Two commenters (SMI and NVMA) expressed concern that not all 
relevant studies were considered in MSHA's analysis of the health 
effects literature on occupational exposure to respirable crystalline 
silica (Document ID 1446; 1441). For example, the NVMA commented that 
the studies referenced in the health effects literature review are

[[Page 28255]]

outdated and do not recognize the changing conditions in mines that 
reduce the likelihood of prolonged exposure to respirable crystalline 
silica, such as the updates made by mines in response to the diesel 
particulate matter standard published in the early 2000s (Document ID 
1441). Similarly, the Pennsylvania Coal Alliance stated that the 
majority of research MSHA relied on did not account for significant 
technological advancements in mining and dust control technology 
(Document ID 1378). This commenter further asserted that the rule 
cannot be justified until the effects of the 2014 RCMD Standard are 
better understood (Document ID 1378).
    MSHA reviewed the relevant literature, including recent 
publications. Additionally, in response to comments on the PRA, MSHA 
read and reviewed studies suggested by commenters. MSHA selected the 
studies which provide the best available epidemiological models to 
develop the estimates of lifetime excess risks and lifetime excess 
cases. These models contain information regarding how the cumulative 
level of exposure relates to the risk of adverse health outcomes. The 
selected studies were based on analyses of miners with a range of 
exposure histories. Further, MSHA's modeling of the avoided cases in 
the FRA directly accounts for any relevant changes in exposure 
conditions because it includes exposure data from as recently as 2019 
for MNM miners and 2021 for coal miners. The exposure data captures 
actual concentrations of respirable crystalline silica that miners were 
exposed to during their shifts. To the extent that changing conditions, 
technological advancements, or the 2014 RCMD Standard have impacted 
miners' exposures to respirable crystalline silica, these effects are 
accounted for in MSHA's models, which use recent exposure data. The 
final provisions of the 2014 RCMD Standard went into effect in 2016, 
which is the first year of coal exposure data MSHA used when modeling 
coal miners' exposures to respirable crystalline silica dust.
    For each health endpoint, MSHA generated two sets of risk 
estimates--one representing a scenario of full compliance with the 
existing standards (herein referred to as the ``Baseline'' scenario) 
and another representing a scenario wherein no samples exceed the new 
PEL (herein referred to as the ``New PEL 50 [mu]g/m\3\'' scenario). In 
the Baseline scenario, MNM miners in the >100-250, >250-500, and >500 
[mu]g/m\3\ groups were assigned exposure intensities of 100 [mu]g/m\3\ 
ISO. Coal miners in the 85.7-100, >100-250, >250-500, and >500 [mu]g/
m\3\ groups were assigned exposure intensities of 85.7 [mu]g/m\3\ ISO, 
calculated as an 8-hour TWA. Exposure intensities were not changed for 
miners with lower exposure concentrations, because their exposures were 
considered compliant with the existing standards. A similar procedure 
was used for the New PEL 50 [mu]g/m\3\ scenario, except that each miner 
group whose exposure exceeded the new PEL was assigned a new exposure 
of 50 [mu]g/m\3\ ISO (for both MNM and coal). This process--of creating 
an exposure profile based on actual exposure data and modifying it 
based on the existing standards or the new PEL--allowed MSHA to 
estimate real exposure conditions that miners would encounter under 
each scenario, thereby enabling estimates of the actual excess risks 
the current population of miners would experience under each scenario 
(Baseline and New PEL 50 [mu]g/m\3\).
    For purposes of calculating risk in the FRA, both for MNM and coal 
miners, MSHA estimated excess risks by using the concentration of 
respirable crystalline silica collected over the full shift and 
calculating it as a full-shift, 8-hour TWA expressed in ISO standards. 
This metric of exposure intensity--the 8-hour TWA concentration of 
respirable crystalline silica in ISO standards--was used consistently 
across all sets of estimates (both MNM and coal sectors, and both the 
Baseline and New PEL 50 [mu]g/m\3\ scenarios), thereby facilitating 
meaningful comparison. MSHA acknowledges that this metric of exposure 
intensity does not correspond to the manner in which coal exposure 
concentrations are currently calculated for purposes of evaluating 
compliance under the existing standard. As discussed in Section 4 of 
the standalone FRA document, MSHA believes that a full-shift, 8-hour 
TWA concentration properly represents risks to miners and thus is the 
most appropriate cumulative exposure metric for computing risk given 
that FTEs were used to scale exposure durations relative to the 
assumption of 250 8-hour workdays per year.
    Commenters, including MSHA Safety Services Inc.; Silica Safety 
Coalition (SSC); the NSSGA; Jervois Idaho Cobalt Operations; and the 
EMA, suggested that disease data show respirable crystalline silica 
exposure and associated adverse health effects are not a problem or 
crisis in MNM mining or that there is only negligible exposure to 
respirable crystalline silica for certain MNM miners (Document ID 1392; 
1432; 1448; 1453; 1442). Similarly, the Portland Cement Association 
stated that silicosis is unknown in the cement industry (Document ID 
1407). One miner-related business further stated that silicosis cases 
are on the rise in coal and are decreasing in MNM and, therefore, 
MSHA's standard should focus only on coal mining, specifically 
underground coal mining (Document ID 1392). In addition, MNM mine 
operators such as K & E Excavating Inc. and K & E Alaska, Inc., also 
commented that there is little to no evidence of silicosis or other 
similar symptoms in MNM mining, especially in comparison to coal mining 
(Document ID 1435; 1436). Finally, the president of N-Compliance Safety 
Services expressed concern regarding the origin of the mortality 
reduction data included in the FRA and stated that they could not find 
deaths reported by MSHA for MNM miners or the associated 7000-1 forms 
(Document ID 1383).
    On the other hand, several commenters from labor unions and health 
organizations agreed with MSHA's finding that MNM miners are at risk of 
respirable crystalline silica-related disease from occupational 
exposures (Document ID 1447; 1449; 1418; 1373). USW asserted that rock 
crushing in iron and other surface mines can release silica-laden dust 
and that silica is also a hazard in cement plants (Document ID 1447). 
The same commenter stated that silica control in MNM mines is becoming 
increasingly important because of new technologies that are likely to 
lead to higher dust exposures (Document ID 1447). Further, Miners 
Clinic of Colorado commented that its data support the need for better 
control of exposure to respirable crystalline silica in MNM mines, and 
said that, of the 400 MNM miners the clinic provided medical 
surveillance for in the past 20 years, 62 percent reported having spent 
over half of their mining tenure in MNM or at least 10 years as a MNM 
miner and, of those 62 percent, 26 percent had pneumoconiosis (based on 
a positive chest radiograph B reading) (Document ID 1418). This 
commenter concluded that MNM miners are at risk for progressive and 
potentially disabling work-related lung disease, although information 
on silicosis disease rates among MNM miners are less readily available 
than those for coal miners (Document ID 1418). Finally, citing several 
studies (Kramer et al., 2012; Friedman et al., 2015; Leso et al., 2019; 
Rose et al., 2019; Wu et al., 2020; LACDHS, 2022; Fazio et al., 2023), 
the Association of Occupational and Environmental Clinics (AOEC) said 
that severe silicosis in the engineered stone manufacturing industry 
has been reported around the

[[Page 28256]]

world, including in the United States (Document ID 1373).
    MSHA disagree with the assertion that silicosis or other diseases 
linked to respirable crystalline silica are not risks for MNM miners. 
MSHA reviewed a wide range of studies that demonstrated disease risks 
amongst miners occupationally exposed to respirable crystalline silica. 
These studies were not limited to underground coal miners and show that 
respirable crystalline exposure produces excess risk for coal and MNM 
miners as well as underground and surface miners. The studies MSHA 
evaluated covered occupations relevant to MNM mining such as 
sandblasters (Abraham and Wiesenfeld, 1997; Hughes et al., 1982), 
industrial sand workers (Vacek et al., 2019), hard rock miners (Verma 
et al., 1982, 2008), and gold miners (Carneiro et al., 2006a; Tse et 
al., 2007b), metal miners (Hessel et al., 1988; Hnizdo and Sluis-
Cremer, 1993; Nelson, 2013), and nonmetal miners such as silica plant 
and ground silica mill workers, whetstone cutters, and silica flour 
packers (Mohebbi and Zubeyri, 2007; NIOSH, 2000a,b; Ogawa et al., 
2003a). Of the MNM exposure samples MSHA collected over the 2016-2021 
period, 18.2 percent exceed the new PEL of 50 [mu]g/m\3\ and 6.4 
percent exceed the existing PEL of 100 [mu]g/m\3\. Based on the 
analysis presented in the FRA, MNM miners are exposed to concentrations 
of respirable crystalline silica that are associated with elevated 
risks of morbidity and mortality from a variety of diseases.
    Further, the ACOEM commented that new information about the 
molecular basis for silica's adverse health effects since OSHA's 2016 
summary of the medical literature highlights the need for establishing 
and enforcing the 50 [mu]g/m\3\ PEL (Wang et al., 2018; Chanda et al., 
2019; Feng et al., 2020; Wu et al., 2021) (Document ID 1405). MSHA's 
review of the more recent health effects literature also supports a 
causal association between respirable crystalline silica exposure and 
increased risk of silicosis morbidity and mortality. Thus, MSHA 
believes that silicosis and other diseases are a risk to any miner 
exposed to high levels of silica dust concentrations, regardless of 
mining commodity.
    Regarding the comment about reported deaths, selected surveillance 
data for both silicosis cases and silicosis deaths are reported in the 
standalone Health Effects document. Nonetheless, MSHA's estimated risk 
and case reductions are based on samples MSHA collected from MNM mines 
and peer-reviewed models of the relationship between exposure to 
respirable crystalline silica and related diseases. The FRA does not 
rely on reported mortality data. MSHA previously has not required 
operators to conduct medical surveillance for MNM miners and becomes 
aware of cases only when miners inform their employer of their illness. 
Thus, these case data are not complete enough to serve as a basis for 
estimating applicable exposure-response models needed for a 
comprehensive risk analysis. However, MSHA believes that the final 
rule's MNM medical surveillance provisions, which are discussed in 
further detail in the FRIA and in the final rule text, will likely help 
to improve this gap in the data.
    Commenters from the SMI, EMA, and Vanderbilt Minerals, argued that 
the aged and occluded crystalline silica (quartz) encountered in 
sorptive minerals, does not pose the same health risk of other forms of 
crystalline silica (Document ID 1446; 1442; 1419). The SMI commented 
that their mining and processing operations do not pose a risk to 
miners' health (Document ID 1446). A more comprehensive discussion of 
these commenters' concerns is addressed in the preamble under Section 
VIII.A.3. Sorptive Minerals.
    The Agency notes that, unlike OSHA, MSHA has no requirement to 
identify a ``significant risk'' before regulating to protect miners' 
health and safety. Nat'l Mining Ass'n v. United Steel Workers, 985 F.3d 
1309, 1319 (11th Cir. 2021) (``[T]he Mine Act does not contain the 
`significant risk' threshold requirement . . . from the OSH Act.''). 
Moreover, unlike OSHA-regulated industries, the mining of sorptive 
minerals involves the removal of overburden, which can disturb 
sedimentary and other silica-rich rock that could contain unoccluded 
respirable crystalline silica. The mining and milling processes 
generate and expose miners to hazardous dust surrounding the mined 
deposits. Also, during mineral processing, sorptive minerals may be 
crushed, heated, dried to remove moisture, re-crushed, and then 
screened to produce various grades of finished products. These 
processes have the potential to fracture and change the nature of the 
surface characteristics of the quartz in the mined commodity. Sorptive 
minerals have always been subject to MSHA's previous PEL, without 
exemption.
    MSHA examined evidence and references from the commenters and 
conducted its own review of the scientific literature. MSHA agrees that 
there is some evidence to suggest that occluded silica is less toxic 
than unoccluded silica (Wallace et al., 1996). Animal studies involving 
respirable crystalline silica suggest that the aged form has lower 
toxicity than the freshly fractured form; however, the aged form still 
retains significant toxicity (Shoemaker et al., 1995; Vallyathan et 
al., 1995; Porter et al., 2002c). MSHA finds that ``lower toxicity'' 
does not imply the absence of adverse health effects. In addition, 
there is no evidence that occlusion and the initial reduced toxicity 
persist following deposition and retention of the crystalline silica 
particles in the lungs.
    There have been few epidemiological studies focused on workers 
exposed to dust generated from sorptive minerals. Examples include 
Phibbs et al. (1971) and Waxweiler et al. (1988). These small cohort 
studies did not evaluate exposures to a wide variety of sorptive 
minerals and relied on data from outdated exposure assessment methods. 
These studies neither disprove the health-based risks associated with 
exposure to respirable crystalline silica nor support a conclusion that 
sorptive minerals present no risk. Other epidemiological studies of 
workers exposed to clay-occluded respirable crystalline silica have 
shown that occupational silicosis can occur among exposed workers 
(Phibbs et al., 1971; Love et al., 1995, 1999; Chen et al., 2005, 2006, 
2012; Harrison et al., 2005). Therefore, MSHA disagrees with these 
commenters.
    MSHA finds that the limited epidemiological data involving sorptive 
minerals do not refute the conclusions drawn from other epidemiological 
and toxicological studies included in MSHA's standalone Health Effects 
document. MSHA concludes, from the best available evidence, that 
exposure to the crystalline silica present in sorptive minerals poses a 
risk of material impairment of health or functional capacity to miners. 
In the Posthearing Brief to OSHA, NIOSH (2014) concluded that 
``currently available information is not adequate to inform 
differential quantitative risk management approaches for crystalline 
silica that are based on surface property measurements.'' MSHA concurs 
with NIOSH's recommendation for a single PEL for respirable crystalline 
silica without consideration of surface properties.

C. Summary of Studies Selected for Modeling

    After reviewing the available studies that support quantitative 
modeling, MSHA selected one exposure-response model from literature for 
each of the five health outcomes that are modeled in the FRA. These 
selections and the exposure-response models are discussed below.

[[Page 28257]]

1. Silicosis Morbidity
    Due to the long latency periods associated with chronic silicosis, 
OSHA's respirable crystalline silica standard relied on the subset of 
studies that were able to contact and evaluate many workers through 
retirement. Studies that included retired workers provides the best 
available evidence of lifetime risk of silicosis morbidity.
    The health endpoint of interest in these studies was the appearance 
of opacities on chest radiographs indicative of pulmonary 
pneumoconiosis (a group of lung diseases caused by the lung's reaction 
to inhaled dusts). The most reliable estimates of silicosis morbidity, 
as detected by chest X-rays, come from the studies that evaluated those 
X-rays over time, included radiographic evaluation of workers after 
they left employment, and derived cumulative or lifetime estimates of 
silicosis disease risk.
    To describe the presence and severity of pneumoconiosis, including 
silicosis, the International Labour Organization (ILO) developed a 
standardized system to classify lung opacities identified on chest 
radiographs (X-rays) (ILO, 1980, 2002, 2011, 2022). The ILO system 
grades the size, shape, and profusion of opacities. Although silicosis 
is defined and categorized based on chest X-ray, the X-ray is an 
imprecise tool for detecting pulmonary pneumoconiosis (Craighead and 
Vallyathan, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and 
Velho, 2002). Hnizdo et al. (1993) recommended that an ILO category 0/1 
(or greater) should be considered indicative of silicosis among workers 
exposed to high respirable crystalline silica concentrations. They 
noted that the sensitivity of the chest X-ray as a screening test 
increases with disease severity and to maintain high specificity, 
category 1/0 (or 1/1) chest X-rays should be considered as a positive 
diagnosis of silicosis for miners who work in low dust occupations 
(Hnizdo et al., 1993). MSHA, consistent with NIOSH's use of chest X-
rays in their occupational respiratory disease surveillance program 
(NIOSH, 2014b), agrees that a small opacity profusion score of 1/0 is 
consistent with chronic silicosis stage 1. Most of the studies reviewed 
by MSHA considered a finding consistent with an ILO category of 1/1 or 
greater to be a positive diagnosis of silicosis, although some also 
considered an X-ray classification of 1/0 or 0/1 to be positive. The 
low sensitivity of chest radiography to detect minimal silicosis 
suggests that risk estimates derived from radiographic evidence likely 
underestimate the true risk of this disease (Craighead and Vallyathan, 
1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and Velho, 
2002; Hoy et al., 2023).
    OSHA summarized the Miller et al. (1995, 1998) and Buchanan et al. 
(2003) studies in their final respirable crystalline silica standard in 
2016 (OSHA 2016a, 81 FR 16286, 16316). These researchers reported on a 
1991 follow-up study of 547 survivors of a 1,416-member cohort of 
Scottish coal workers from a single mine. These men had all worked in 
the mine during the period between early 1971 and mid-1976, during 
which time they had experienced ``unusually high concentrations of 
freshly cut quartz in mixed coal mine dust.'' The population's 
exposures to quartz dust had been measured in unique detail for a 
considerable proportion of the men's working lives (OSHA, 2013b, page 
333).
    The 1,416 men had previous chest X-rays dating from before, during, 
or just after this high respirable crystalline silica exposure period. 
Of these 1,416 men, 384 were identified as having died by 1990/1991. Of 
the 1,032 remaining men, 156 were untraced, and, of the 876 who were 
traced and replied, 711 agreed to participate in the study. Of these, 
the total number of miners who were surveyed was 551. Four of these 
were omitted, two because of a lack of an available chest X-ray. The 
547 surviving miners (age range: 29-85 years, average=59 years) were 
interviewed and received their follow-up chest X-rays between November 
1990 and April 1991. The interviews consisted of questions on current 
and past smoking habits and occupational history since leaving the coal 
mine, which closed in 1981. They were also asked about respiratory 
symptoms and were given a spirometry test (OSHA, 2013b, pages 333-334).
    Exposure characterization was based on extensive respirable dust 
sampling; samples were analyzed for quartz content by IR spectroscopy. 
Between 1969 and 1977, two coal seams were mined. One had produced 
quarterly average concentrations of respirable crystalline silica much 
less than 1,000 [mu]g/m\3\ (only 10 percent exceeded 300 [mu]g/m\3\). 
The other more unusual seam (mined between 1971 and 1976) lay in 
sandstone strata and generated respirable crystalline silica levels 
such that quarterly average exposures exceeded 1,000 [mu]g/m\3\ (10 
percent of the quarterly measurements were over 10,000 [mu]g/m\3\). 
Thus, this cohort study allowed evaluation of the effects of both 
higher and lower respirable crystalline silica concentrations and 
exposure-rate effects on the development of silicosis (OSHA, 2013b, 
page 334).
    Three physicians read each chest film taken during the current 
survey as well as films from the surveys conducted in 1974 and 1978. 
Films from an earlier 1970 survey were read only if no films were 
available from the subsequent two surveys. Silicosis cases were 
identified if the median classification of the three readers indicated 
an ILO category of 1/1 or greater (Miller et al., 1995, page 24), plus 
a progression from the earlier reading. Of the 547 men, 203 (38 
percent) showed progression of at least 1 ILO category from the 1970s' 
surveys to the 1990-91 survey; in 128 of these (24 percent), there was 
progression of 2 or more ILO categories. In the 1970s' surveys, 504 men 
had normal chest X-rays; of these, 120 (24 percent) acquired an 
abnormal X-ray consistent with ILO category 1/0 or greater at the 
follow-up. Of the 36 men whose X-rays were consistent with ILO category 
1/0 or greater in the 1970s' surveys, 27 (75 percent) exhibited further 
progression at the 1990/1991 follow-up. Only one subject showed a 
regression from any earlier reading, and that was slight, from 1/0 to 
0/1. The earlier Miller et al. (1995) report presented results for 
cases classified as having X-ray films consistent with either 1/0+ and 
2/1+ degree of profusion; the Miller et al. (1998) analysis and the 
Buchanan et al. (2003) re-analyses emphasized the results from cases 
having X-rays classified as 2/1+ (OSHA, 2013b, page 334).
    MSHA modeled the exposure-response relationship by using cumulative 
exposure expressed as gram/m\3\-hours, assuming 2,000 work hours per 
year and a 45-year working life (after adjusting for full-time 
equivalents, including miners (excluding contract miners) and contract 
miners). MSHA estimated risk at the existing standard assuming 
cumulative exposure to 100 [mu]g/m\3\ ISO for MNM miners and 85.7 
[mu]g/m\3\ ISO (100 [mu]g/m\3\ MRE) for coal miners. Respirable 
crystalline silica exposures were calculated by commodity, and median 
exposure values were used within a variety of exposure intervals. Risks 
were computed using a life table methodology which iteratively updated 
the survival, risk, and mortality rates each year based on the results 
of the preceding year. Covariates in the regression included smoking, 
age, amount of coal dust, and percent of quartz in the coal dust during 
various previous survey periods.
    Both Miller et al. papers (1995, 1998) presented the results of 
numerous regression models, and they compared

[[Page 28258]]

the results of the partial regression coefficients using Z statistics 
of the coefficient divided by the standard error. Also presented were 
the residual deviances of the models and the residual degrees of 
freedom. In the introduction to the results section, Miller et al. 
(1995) stated that, ``in none of the models fitted was there a 
significant effect of smoking habit (current, ex-smoker, and never 
smoker), nor was there any evidence of any difference between smoking 
groups in their relationship of response with age.'' They therefore 
presented the results of the regression analyses without terms for 
smoking effects (i.e., without including smoking effects as a variable 
in the final regression analysis, because they found that smoking did 
not affect the modeling results). The logistic regression models 
developed by Miller et al. (1995) included terms for cumulative 
exposure and age. In their later publication, Miller et al. (1998) 
presented models similar to their 1995 report, but without the age 
variable. Their logistic regression model A from Table 7 of their 
report (page 56) included only an intercept (-4.32) and the respirable 
crystalline silica (quartz) cumulative exposure variable (0.416). They 
estimated that respirable crystalline silica exposure at an average 
concentration of 100 [mu]g/m\3\ for 15 years (2.6 gram/m\3\-hr assuming 
1,750 hours worked per year) would result in an increased risk of 
silicosis (ILO>2/1) of 5 percent (OSHA, 2013b, page 334).
    OSHA had a high degree of confidence in the estimates of silicosis 
morbidity risk from this Scotland coal mine study. This was mainly 
because of highly detailed and extensive exposure measurements, 
radiographic records, and detailed analyses of high exposure-rate 
effects. MSHA has reviewed and agrees with OSHA's conclusion.
    Buchanan et al. (2003) provided an analysis and risk estimates only 
for cases having X-ray films consistent with ILO category 2/1+ extent 
of profusion of opacities, after adjusting for the disproportionately 
severe effect of exposure to high respirable crystalline silica 
concentrations. Estimating the risk of 1/0+ profusions from the 
Buchanan et al. (2003) or the earlier Miller et al. (1995, 1998) 
publications can only be roughly approximated because of the summary 
information included. Table 4 of Miller et al. (1998, page 55) presents 
a cross-tabulation of radiograph progression, using the 12-point ILO 
scale, from the last baseline examination to the 1990/1991 follow-up 
visit for the 547 men at the Scottish coal mine. From this table, among 
miners having both early X-ray films and follow-up films, 44 men had 
progressed to 2/1+ by the last follow-up and an additional 105 men had 
experienced the onset of silicosis (i.e., X-ray films were classified 
as 1/0, 1/1, or 1/2). Thus, by the time of the follow-up, there were 
three times more miners with silicosis consistent with ILO category 1 
than there were miners with a category 2+ level of severity ((105 + 
44)/44 = 3.38). This suggests that the Buchanan et al. (2003) model, 
which reflects the risk of progressing to ILO category 2+, 
underestimates the risk of acquiring radiological silicosis by about 
three-fold in this population (OSHA, 2013b, page 336). This type of 
analysis shows that the risk of developing silicosis estimated from the 
Buchanan et al. (2003) and Miller et al. (1998) studies is of the same 
magnitude as the risks reported by Hnizdo and Sluis-Cremer (1993) 
(OSHA, 2013b, page 338).
    MSHA estimated silicosis risk by using the Buchanan et al. (2003) 
model that predicted the lifetime probability of developing silicosis 
at the 2/1+ category based on cumulative respirable crystalline silica 
exposures. As discussed previously, MSHA applied the Buchanan et al. 
(2003) model, assuming that miners are exposed for 45 years of working 
life extending from the start of age 21 through the end of age 65, 
using a life table approach. Buchanan et al. provides an exposure-
response model using cumulative exposure in mg/m\3\-hours as the 
predictor variable and lifetime risk of silicosis as the outcome 
variable. MSHA assumed 45 years of exposure, each such year having a 
duration of 2,000 work hours, scaled by a weighted average FTE ratio 
that accounts for the average annual hours worked by miners (excluding 
contract miners) and contract miners.
2. Accelerated Silicosis and Rapidly Progressive Pneumoconiosis (RPP) 
Study
    OSHA concluded in their risk assessment, and MSHA agrees, that 
there is little evidence of a dose-rate effect at respirable 
crystalline silica concentrations in the exposure range of 25 [mu]g/
m\3\ to 500 [mu]g/m\3\ (81 FR 16286, 16396). OSHA noted that the risk 
estimates derived from the Buchanan et al. (2003) study were not 
appreciably different from those derived from the other studies of 
silicosis morbidity (see OSHA 2016a, 81 FR 16286, 16386; Table VI-1. 
Summary of Lifetime or Cumulative Risk Estimates for Crystalline 
Silica). However, OSHA also concluded that some uncertainty related to 
dose-rate effects exists at concentrations far higher than the exposure 
range of interest. OSHA stated that it is possible for such a dose-rate 
effect to impact the results if not properly addressed in study 
populations with high concentration exposures. OSHA used the model from 
the Buchanan et al. (2003) study in its silicosis morbidity risk 
assessment to account for possible dose-rate effects at high average 
concentrations (OSHA 2016a, 81 FR 16286, 16396; OSHA, 2013b, pages 335-
342). MSHA has reviewed and agrees with OSHA's conclusions.
    NIOSH stated in its post-hearing brief to OSHA that a ``detailed 
examination of dose rate would require extensive and real time exposure 
history which does not exist for silica (or almost any other agent)'' 
(81 FR 16285, 16375). Similarly, Dr. Kenneth Crump, a researcher from 
Louisiana Tech University Foundation who served on OSHA's peer review 
panel for the Review of Health Effects Literature and Preliminary 
Quantitative Risk Assessment, wrote to OSHA that, ``[h]aving noted that 
there is evidence for a dose rate effect for silicosis, it may be 
difficult to account for it quantitatively. The data are likely to be 
limited by uncertainty in exposures at earlier times, which were likely 
to be higher'' (OSHA 2016a, 81 FR 16286, 16375). OSHA agreed with the 
conclusions of NIOSH and Dr. Crump. OSHA believed that it used the best 
available evidence to estimate risks of silicosis morbidity and 
sufficiently accounted for any dose rate effect at high silica average 
concentrations by using the Buchanan et al. (2003) study as part of 
their final Quantitative Risk Analysis (QRA) (OSHA 2016a, 81 FR 16286, 
16396). MSHA has reviewed and agrees with OSHA's conclusions.
    MSHA is using the Buchanan et al. (2003) study to explain, in part, 
the observed cases of progressive lung disease in miners, known as RPP 
in coal miners (Laney and Attfield, 2010; Wade et al., 2011; Laney et 
al., 2012b, 2017; Blackley et al., 2016b, 2018b; Almberg et al., 2018a; 
Reynolds et al., 2018b; Halldin et al., 2019, 2020; Cohen et al., 2022) 
and accelerated silicosis in MNM miners (Hessel et al., 1988; Mohebbi 
and Zubeyri, 2007; Dumavibhat et al., 2013). This research explains, in 
part, the progressive disease observed in shorter-tenured miners. MSHA 
believes that the risks estimated by the Buchanan et al. model can be 
applied to all mining populations that have similar respirable 
crystalline silica exposure exceedances. MSHA data also indicate that a 
smaller number of MSHA samples showed respirable crystalline silica 
concentrations well above the existing MSHA standard of 100 [mu]g/m\3\. 
Over the last 15 years of MNM compliance data,

[[Page 28259]]

188 samples (0.3 percent) were over 500 [mu]g/m\3\; the upper range of 
exposure was 4,289 [mu]g/m\3\ ISO (see FRA Table 4 of the FRA 
document). Over the last 5 years of coal compliance data, eight samples 
(<0.1 percent) were over 500 [mu]g/m\3\; the upper range of exposure 
was 791.4 [mu]g/m\3\ MRE (see FRA Table 7 of the standalone FRA 
document).
    Analysis provided by Buchanan et al. (2003) provides strong 
evidence of an exposure-rate effect for silicosis in a British 
Pneumoconiosis Field Research (PFR) coal mining cohort exposed to high 
levels of respirable crystalline silica over short periods of time 
(OSHA, 2013b, page 335). Exposure was categorized as pre- and post-
1964, the latter period being that of generally higher quartz 
concentrations used to estimate exposure-rate effects. For the purpose 
of this analysis, the results were presented for the 371 men (out of 
the original 547) who were between the ages of 50 and 74 at the time of 
the 1990/1991 follow-up, ``since they had experienced the widest range 
of quartz concentrations and showed the strongest exposure-response 
relations.'' Thus, combined with their exposure history, which went 
back to pre-1954, many of these men had 30 to 40+ years of highly 
detailed occupational exposure histories available for analysis. Of 
these 371 miners, there were 35 men (9.4 percent) who had X-ray films 
consistent with ILO category 2/1+, with at least 29 of them having 
progressed from less severe silicosis since the previous follow-up 
during the 1970s (from Miller et al., 1998) (OSHA, 2013b, page 335).
    The Buchanan et al. (2003) re-analysis presented logistic 
regression models in stages. In the final stage of modeling, using only 
the statistically significant post-1964 cumulative exposures, the 
authors separated these exposures into, ``two quartz concentration 
bands, defined by the cut-point 2.0 mg/m\3\.'' This yielded the final 
simplified equation, adapted from Buchanan et al., 2003, page 162:
[GRAPHIC] [TIFF OMITTED] TR18AP24.079

where p2 is the probability of profusion category 2/1 or 
higher (2/1+) at follow-up and E is the cumulative exposure.

    In this model, both the cumulative exposure concentration variables 
were ``highly statistically significant in the presence of the other'' 
(Buchanan et al., 2003, page 162). Since these variables were in the 
same units, mg/m\3\-hr, the authors noted that the coefficient for 
exposure concentrations >2,000 [micro]g/m\3\ (>2.0 mg/m\3\) was three 
times that for the concentrations <2,000 [micro]g/m\3\ (<2.0 mg/m\3\). 
They concluded that their latest analysis showed that ``the risk of 
silicosis over a working lifetime can rise dramatically with exposure 
to such high concentrations over a timescale of merely a few months'' 
(Buchanan et al., 2003, page 163; OSHA, 2013b, page 336).
    Buchanan et al. (2003) also used these models to estimate the risk 
of acquiring a chest X-ray classified as ILO category 2/1+, 15 years 
after exposure ends, as a function of low <2,000 [micro]g/m\3\ (<2.0 
mg/m\3\) and high >2,000 [micro]g/m\3\ (>2.0 mg/m\3\) quartz 
concentrations. OSHA chose to use this model to estimate the risk of 
radiological silicosis consistent with an ILO category 2/1+ chest X-ray 
for several exposure scenarios. They assumed 45 years of exposure, 
2,000 hours/year of exposure, and no exposure above a concentration of 
2,000 [micro]g/m\3\ (2.0 mg/m\3\) (OSHA, 2013b, page 336).
    Buchanan et al. (2003) used these models to estimate the combined 
effect on the predicted risk of low quartz exposures (e.g., 100 
[micro]g/m\3\, equal to 0.1 mg/m\3\) and short-term exposures to high 
quartz concentrations (e.g., 2,000 [micro]g/m\3\, equal to 2 mg/m\3\). 
Predicted risks were estimated for miners who progressed to silicosis 
level 2/1+ 15 years after exposure ended. This analysis showed the 
increase in predicted risk with relatively short periods of quartz 
exceedance exposures, over 4, 8, and 12 months. Buchanan et al. 
predicted a risk of 2.5 percent for 15 years quartz exposure to 100 
[micro]g/m\3\ (0.1 mg/m\3\). This risk increased to 10.6 percent with 
the addition of only 4 months of exposure at the higher concentration. 
The risk increased further to 72 percent with 12 months at the higher 
exposure of 2,000 [micro]g/m\3\ (2.0 mg/m\3\).
    The results indicated miners exposed to exceedances above MSHA's 
existing standard could develop progression of silicosis at an 
exaggerated rate. The results of Buchanan et al. also indicated that 
miners' exposure to exceedances at the new PEL will also suffer 
increased risk of developing progressive disease, though at a reduced 
rate (see Buchanan et al. (2003), Table 4, page 163).
    MSHA used a life table approach to estimate the lifetime excess 
silicosis morbidity from age 21 to age 80, assuming exposure from the 
start of age 21 through the end of age 65 (45 years of working life) 
and an additional 15 years of potential illness progress thereafter. 
MSHA used the Buchanan et al. (2003) model to estimate the effect of 
respirable crystalline silica exposure exceedances as seen in MSHA's 
compliance data on miners' silicosis risk at the existing and new 
standard. The model predicted the probability of developing silicosis 
at the 2/1+ category based on cumulative respirable crystalline silica 
exposures. Age-specific cumulative risk was estimated as 1/(1+EXP(-(-
4.83+0.443*cumulative exposure))). The model determined that even at 
17.4 hours on average per year at an exposure of 1,500 [micro]g/m\3\ 
(1.50 mg/m\3\), miners' risk of developing 2/1+ silicosis increased 
from a baseline of 24.8/1,000 to 29.0/1,000 at the existing standard 
and 14/1,000 to 16.6/1,000 at the new standard. Of course, the more 
hours exposed to these levels of respirable crystalline silica resulted 
in even higher increased risk. It is important to note that NIOSH's X-
ray classification of the lowest case of pneumoconiosis is 1/0 
profusion of small opacities (NIOSH, 2008c, page A-2). Using a case 
definition of level 2/1+, the miners studied by Buchanan et al. (2003) 
would be more likely to show clinical signs of disease. MSHA emphasizes 
the importance of maintaining miner exposure to respirable crystalline 
silica at or below the 50 [mu]g/m\3\ PEL to minimize these health risks 
as much as possible.
3. Silicosis and NMRD Mortality
    Silicosis mortality was ascertained in the studies included in the 
pooled analysis by Mannetje et al. (2002b). These studies included 
cohorts of U.S. diatomaceous earth workers (Checkoway et al., 1997), 
Finnish granite workers (Koskela et al., 1994), U.S. granite workers 
(Costello and Graham, 1988), U.S. industrial sand workers (Steenland 
and Sanderson, 2001), U.S. gold miners (Steenland and Brown, 1995b), 
and Australian gold miners (de Klerk and Musk, 1998). The researchers 
analyzed death certificates across all cohorts for cause of death. OSHA 
relied upon the published, peer-reviewed, pooled analysis of six

[[Page 28260]]

epidemiological studies first published by Mannetje et al. (2002b) and 
a sensitivity analysis of the data conducted by ToxaChemica 
International, Inc. (2004). OSHA used the model described by Mannetje 
et al. (2002b) and the rate ratios that were estimated from the 
ToxaChemica, International Inc. sensitivity analysis to estimate the 
risks of silicosis mortality. This process better controlled for age 
and exposure measurement uncertainty (OSHA, 2013b, page 295). MSHA has 
reviewed and agrees with OSHA's conclusions. These studies are 
summarized below, including detailed discussion and analysis of 
uncertainty in the studies and associated risk estimates.
    OSHA found that the estimates from Mannetje et al. (2002b) and 
ToxaChemica Inc. probably understated the actual risk because silicosis 
is underreported as a cause of death since there is no nationwide 
system for collecting silicosis morbidity case data (OSHA, 2016a, 81 FR 
16286, 16325). To help address this uncertainty, OSHA also included an 
exposure-response analysis of diatomaceous earth workers (Park et al., 
2002). This analysis better recognized the totality of respirable 
crystalline silica-related respiratory disease than the datasets of 
Mannetje et al. (2002b) and ToxaChemica International Inc. (2004). 
Information from the Park et al. (2002) study (described in the next 
subsection) was used to quantify the relationship between cristobalite 
exposure and mortality caused by NMRD, which includes silicosis, 
pneumoconiosis, emphysema, and chronic bronchitis. The category of NMRD 
captures much of the silicosis misclassification that results in 
underestimation of the disease. NMRD also includes risks from other 
lung diseases associated with respirable crystalline silica exposures. 
OSHA found the risk estimates derived from Park et al. (2002) were 
important to include in their range of estimates of the risk of death 
from respirable crystalline silica-related respiratory diseases, 
including silicosis (OSHA, 2013b, pages 297-298). OSHA concluded that 
the ToxaChemica International Inc. (2004) re-analysis of Mannetje et 
al.'s (2002b) silicosis mortality data and Park et al.'s (2002) study 
of NMRD mortality provided a credible range of estimates of mortality 
risk from silicosis and NMRD across many workplaces. The upper end of 
this range, based on the Park et al. (2002) study, is less likely to 
underestimate risk because of underreporting of silicosis mortality. 
However, risk estimates from studies focusing on cohorts of workers 
from different industries cannot be directly compared (OSHA 2016a, 81 
FR 16286, 16397).
a. Silicosis Mortality: Mannetje et al. (2002b); ToxaChemica, 
International, Inc. (2004)
    Mannetje et al. (2002b) relied upon the epidemiological studies 
contained within the Steenland et al. (2001a) pooled analysis of lung 
cancer mortality that also included extensive data on silicosis. The 
six cohorts included:
    (1) U.S. diatomaceous earth workers (Checkoway et al., 1997),
    (2) Finnish granite workers (Koskela et al., 1994),
    (3) U.S. granite workers (Costello and Graham, 1988),
    (4) U.S. industrial sand workers (Steenland and Sanderson, 2001),
    (5) U.S. gold miners (Steenland and Brown, 1995b), and
    (6) Australian gold miners (de Klerk and Musk, 1998).
    These six cohorts contained 18,364 workers and 170 silicosis 
deaths, where silicosis mortality was defined as death from silicosis 
(ICD-9 502, n=150) or from unspecified pneumoconiosis (ICD-9 505, 
n=20). Table VI-3 provides information on each cohort, including size, 
time period studied, overall number of deaths, and number of deaths 
identified as silicosis for the pooled analysis conducted by Mannetje 
et al. (2002b). The authors stated this definition may have 
underestimated the number of silicosis deaths some of which may have 
been misclassified as other causes (e.g., tuberculosis or COPD without 
mention of pneumoconiosis). Four cohorts were not included in the 
silicosis mortality study. The three Chinese studies did not use the 
ICD to code cause of death. In the South African gold miner study, 
silicosis was not generally recognized as an underlying cause of death. 
Thus, it did not appear on death certificates (OSHA, 2013b, page 292).

[[Page 28261]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.143

    Mannetje et al. (2002a) described the exposure assessments 
developed for the pooled analysis. Exposure information from each of 
the 10 cohort studies varied and included dust measurements 
representing particle counts, mass of total dust, and respirable dust 
mass. Measurement methods also changed over time for each of the cohort 
studies. Generally, sampling was performed using impingers in earlier 
decades, and gravimetric techniques later. Exposure data based on 
analysis for respirable crystalline silica by XRD (the current method 
of choice) were available only from the study of U.S. industrial sand 
workers. To develop cumulative exposure estimates for all cohort 
members and to pool the cohort data, all exposure data were converted 
to units of [micro]g/m\3\ (mg/m\3\) respirable crystalline silica. 
Cohort-specific conversion factors were generated based on the silica 
content of the dust to which workers were exposed. In some instances, 
results of side-by-side comparison sampling were available. Within each 
cohort, available job- or process-specific information on the silica 
composition or nature of the dust was used to reconstruct respirable 
crystalline silica exposures. Most of the studies did not have exposure 
measurements prior to the 1950s. Exposures occurring prior to that time 
were estimated either by assuming such exposures were the same as the 
earliest recorded for the cohort or by modeling that accounted for 
documented changes in dust control measures.
    To evaluate the reasonableness of the exposure assessment for the 
lung cancer pooled study, Mannetje et al. (2002a) investigated the 
relationship between silicosis mortality and cumulative exposure. They 
performed a nested case-control analysis for silicosis or unspecified 
pneumoconiosis using conditional logistic regression. Since exposure to 
respirable crystalline silica is the sole cause of silicosis, any 
finding for which cumulative exposure was unrelated to silicosis 
mortality risk would suggest that serious misclassification of the 
exposures assigned to cohort members occurred. Cases and controls were 
matched for race, sex, age (within 5 years), and 100 controls were 
matched to each case. Each cohort was stratified into quartiles by 
cumulative exposure. Standardized rate ratios (SRRs) were calculated 
using the lowest-exposure quartile as the baseline. Odds ratios (ORs) 
were also calculated for the pooled data set overall, which was 
stratified into quintiles based on cumulative exposure. For the pooled 
data set, the relationship between the ORs for silicosis mortality and 
cumulative exposure, along with each of the 95 percent confidence 
intervals (95% CI), were as follows:
    (1) 4,450 [micro]g/m\3\-years (4.45 mg/m\3\-years), OR=3.1 (95% CI: 
2.5-4.0);
    (2) 9,080 [micro]g/m\3\-years (9.08 mg/m\3\-years), OR=4.6 (95% CI: 
3.6-5.9);
    (3) 16,260 [micro]g/m\3\-years (16.26 mg/m\3\-years), OR=4.5 (95% 
CI: 3.5-5.8); and
    (4) 42,330 [micro]g/m\3\-years (42.33 mg/m\3\-years), OR=4.8 (95% 
CI: 3.7-6.2).
    In addition, in seven of the cohorts, there was a statistically 
significant trend between silicosis mortality and cumulative exposure. 
For two of the cohorts (U.S. granite workers and U.S. gold miners), the 
trend test was not statistically significant (p=0.10). An analysis 
could not be performed on the South African gold miner cohort because 
silicosis was never coded as an underlying cause of death, apparently 
due to coding practices in that country.
    Based on this analysis, Mannetje et al. (2002a) concluded that the 
exposure-response relationship for the pooled data set was ``positive 
and reasonably monotonic.'' That is, the response increased with 
increasing exposure. The results also indicated that the exposure 
assessments provided reasonable estimates of cumulative exposures. In 
addition, despite some large differences in the range of cumulative 
exposures between cohorts, a clear positive exposure-response trend was 
evident in seven of the cohorts (OSHA, 2013b, page 271).
    Furthermore, in their pooled analysis of silicosis mortality for 
six of the cohorts, Mannetje et al. (2002b) found a clear and 
consistently positive response with increasing decile of cumulative 
exposure, although there was an anomaly in the 9th decile. Overall, 
these data supported a monotonic exposure-

[[Page 28262]]

response relationship for silicosis. Although some exposure 
misclassification almost certainly existed in the pooled data set, the 
authors concluded that exposure estimates did not appear to have been 
sufficiently misclassified to obscure an exposure-response relationship 
(OSHA, 2013b, page 271).
    As part of an uncertainty analysis conducted for OSHA, Drs. 
Steenland and Bartell (ToxaChemica International, Inc., 2004) examined 
the quality of the original data set and analysis to identify and 
correct any data entry, programming, or reporting errors (ToxaChemica 
International, Inc., 2004). This quality assurance process revealed a 
small number of errors in exposure calculations for the originally 
reported results. Primarily, these errors resulted from rounding of job 
class exposures when converting the original data file for use with a 
different statistical program. Although the corrections affected some 
of the exposure-response models for individual cohorts, ToxaChemica 
International, Inc. (2004) reported that models based on the pooled 
dataset were not impacted by the correction of these errors (OSHA, 
2013b, pages 271-272).
    Silicosis mortality was evaluated using standard life table 
analysis in Mannetje et al. (2002b). Poisson regression, using 10 
categories of cumulative exposure and adjusting for age, calendar time, 
and cohort, was conducted to derive silicosis mortality rate ratios 
using the lowest exposure group of 0-100 [micro]g/m\3\-years (0-0.1 mg/
m\3\-year) as the referent group. More detailed exploration of the 
exposure-response relationship using a variety of exposure metrics, 
including cumulative exposure, duration of exposure, average exposure 
(calculated as cumulative exposure/duration), and the log 
transformations of these variables, was conducted via nested case-
control analyses (conditional logistic regression). Each case was 
matched to 100 controls selected from among those who had survived to 
at least the age of the case, with additional matching on cohort, race, 
sex, and date of birth within 5 years. The authors explored lags of 0, 
5, 10, 15, and 20 years, noting that there is no a priori reason to 
apply an exposure lag, as silicosis can develop within a short period 
after exposure. However, a lag could potentially improve the model, as 
there is often a considerable delay in the development of silicosis 
following exposure. In addition to the parametric conditional logistic 
regression models, the authors performed some analyses using a cubic-
spline model, with knots at 5, 25, 50, 75, and 95 percent of the 
distribution of exposure. Models with cohort-exposure interaction terms 
were fit to assess heterogeneity between cohorts (OSHA, 2013b, page 
294).
    The categorical analysis found a nearly monotonic increase in 
silicosis rates with cumulative exposure, from 4.7 per 100,000 person-
years in the lowest exposure category (0-990 [micro]g/m\3\-years [0-
0.99 mg/m\3\-years]) to 299 per 100,000 person-years in the highest 
exposure category (>28,000 [micro]g/m\3\-years [>28 mg/m\3\-years]). 
Nested case-control analyses showed a significant association between 
silicosis mortality and cumulative exposure, average exposure, and 
duration of exposure. The best-fitting conditional logistic regression 
model used log-transformed cumulative exposure with no exposure lag, 
with a model [chi]\2\ of 73.2 versus [chi]\2\ values ranging from 19.9 
to 30.9 for average exposure, duration of exposure, and untransformed 
cumulative exposure (1 degree of freedom). No significant heterogeneity 
was found between individual cohorts for the model based on log-
cumulative exposure. The cubic-spline model did not improve the model 
fit for the parametric logistic regression model using the log-
cumulative exposure (OSHA, 2013b, page 294).
    Mannetje et al. (2002b) developed estimates of silicosis mortality 
risk through age 65 for two levels of exposure (50 and 100 [micro]g/
m\3\ respirable crystalline silica), assuming a working life of 
occupational exposure from age 20 to 65. Risk estimates were calculated 
based on the silicosis mortality rate ratios derived from the 
categorical analysis described above. The period of time over which 
workers' exposures and risks were calculated (age 20 to 65) was divided 
into one-year intervals. The mortality rate used to calculate risk in 
any given interval was dependent on the worker's cumulative exposure at 
that time. The equation used to calculate risk is as follows:
[GRAPHIC] [TIFF OMITTED] TR18AP24.080

Where timei is equal to 1 year for every age i, and ratei is the age-, 
calendar time-, and cohort adjusted silicosis mortality rate associated 
with the level of cumulative exposure acquired at age i, as presented 
in Mannetje et al. (2002b, Table 2, page 725). The calculated absolute 
risks equal the excess risks since there is no background rate of 
silicosis in the exposed population. Mannetje et al. (2002b) estimated 
the lifetime risk of death from silicosis, assuming 45 years of 
exposure to 100 [micro]g/m\3\, to be 13 deaths per 1,000 workers; at an 
exposure of 50 [micro]g/m\3\, the estimated lifetime risk was 6 per 
1,000. Confidence intervals (CIs) were not reported (OSHA, 2013b, page 
295).
    In summary, OSHA's estimates of silicosis morbidity risks were 
based on studies of active and retired workers for which exposure 
histories could be constructed and chest X-ray films could be evaluated 
for signs of silicosis. MSHA agrees with OSHA's estimate of silicosis 
morbidity risks.
    There is evidence in the record that chest X-ray films are 
relatively insensitive to detecting lung fibrosis (OSHA 2016a, 81 FR 
16286, 16397). Hnizdo et al. (1993) found chest X-ray films to have low 
sensitivity for detecting lung fibrosis related to initial cases of 
silicosis, compared to pathological examination at autopsy. To address 
the low sensitivity of chest X-rays for detecting silicosis, Hnizdo et 
al. (1993) recommended that radiographs consistent with an ILO category 
of 0/1 or greater be considered indicative of silicosis among workers 
exposed to a high concentration of respirable crystalline silica-
containing dust. In like manner, to maintain high specificity, chest X-
rays classified as category 1/0 or 1/1 should be considered as a 
positive diagnosis of silicosis in miners who work in low dust (0.2 mg/
m\3\) occupations. The studies on which OSHA relied in its risk 
assessment typically used an ILO category of 1/0 or greater to identify 
cases of silicosis. According to Hnizdo et al. (1993), they were 
unlikely to have included many false positives (i.e., assumed diagnosis 
of silicosis in a miner without the disease), but may have included 
false negatives (i.e., failure to identify cases of silicosis). Thus, 
in OSHA's risk assessment, the use of chest X-rays to

[[Page 28263]]

ascertain silicosis cases in the morbidity studies may have 
underestimated risk given the X-rays' low sensitivity to detect 
disease. MSHA agrees with OSHA's assessment.
    To estimate the risk of silicosis mortality at the then existing 
and then proposed exposure limits, OSHA used the categorical model 
described by Mannetje et al. (2002b) but did not rely upon the Poisson 
regression in their study. Instead, OSHA used rate ratios estimated 
from a nested case-control design implemented as part of a sensitivity 
analysis (ToxaChemica International, Inc., 2004). The case-control 
design was selected because it was expected to better control for age. 
In addition, the rate ratios derived from the case control study were 
derived from a Monte Carlo analysis to reflect exposure measurement 
uncertainty (See ToxaChemica International, Inc. (2004), Table 7, page 
40). The rate ratio for each interval of cumulative exposure was 
multiplied by the annual silicosis rate assumed to be associated with 
the lowest exposure interval, 4.7 per 100,000 for exposures of 990 
[micro]g/m\3\-years (0.99 mg/m\3\-years), to estimate the silicosis 
rate for each interval of exposure. The lifetime silicosis mortality 
risk is the sum of the silicosis rate for each year of life through age 
85 and assuming exposure from age 20 to 65. From this analysis, OSHA 
estimated the silicosis mortality risk for exposure to the then 
existing general industry exposure limit (100 [micro]g/m\3\) and then 
proposed exposure limit (50 [micro]g/m\3\) to be 11 (95% CI 5-37) and 7 
(95% CI 3-21) deaths per 1,000 workers, respectively. For exposure to 
250[micro]g/m\3\ (0.25 mg/m\3\) and 500 [micro]g/m\3\ (0.5 mg/m\3\), 
the range approximating the then existing construction/shipyard 
exposure limit, OSHA estimated the risk to range from 17 (95% CI 5-66) 
to 22 (95% CI 6-85) deaths per 1,000 workers (OSHA, 2013b, page 294-
295).
    In view of the aforementioned discussion, MSHA agrees with OSHA's 
analysis, and MSHA also selected the Mannetje et al. (2002b) study for 
estimating silicosis mortality risks and cases. MSHA used a life table 
analysis to estimate the lifetime excess silicosis mortality through 
age 80. To estimate the age-specific risk of silicosis mortality at the 
existing standards, the new PEL, and the action level, MSHA used the 
same categorical model that OSHA used in their PQRA (as described above 
from Mannetje et al., 2002b; ToxaChemica International, Inc., 2004) to 
estimate lifetime risk following cumulative exposure of 45 years. MSHA 
used the 2018 all-cause mortality rates (NCHS, Underlying Cause of 
Death, 2018 on CDC WONDER Online Database, released in 2020b) as all-
cause mortality rates. As stated previously, the general (unexposed) 
population is assumed to have silicosis mortality rates equal to zero.
    In response to MSHA's question about the PRA in the proposed rule, 
the NVMA cited a 2021 study examining silica exposure in artificial 
stone workers, which this commenter asserted found higher prevalence of 
silicosis amongst those who did not use personal protective equipment 
(PPE) and amongst tobacco users (Requena-Mullor et al., 2021) (Document 
ID 1441). This commenter continued that wearing respirators is a 
beneficial aid in protecting workers and that other technological 
advances in the mining industry have reduced exposures to respirable 
crystalline silica. However, this commenter did not elaborate on how 
the cited study or the technological advances within the industry 
relate to MSHA's risk analysis or whether the commenter believes the 
presented information indicate any weaknesses or shortcomings in MSHA's 
modeling. Further, the particular study this commenter cited did not 
find a statistically significant difference between tobacco users and 
non-tobacco users (Requena-Mullor et al., 2021).
    MSHA acknowledges that the relationship between exposure to 
respirable crystalline silica and silicosis may be confounded by 
several variables, including smoking. However, confounders are 
discussed in the FRA and were considered by the original authors of the 
studies MSHA selected for modeling. Park et al. (2002), which MSHA used 
to model NMRD mortality, fit a model that was stratified on smoking 
status. Mannetje et al. (2002b) did not account for smoking but noted 
that ``no effect of smoking was detected in a study of Colorado 
miners.'' Moreover, the Mannetje et al. (2002b) model was used to 
determine how many of the NMRD deaths were attributable to silicosis as 
opposed to other forms of NMRD. The total estimate for NMRD deaths 
including silicosis is based on Park et al. (2002), which did account 
for smoking status. Buchanan et al. (2003), which MSHA used to estimate 
silicosis morbidity, originally included smoking status as a covariate, 
but the authors removed this variable from the final model because it 
did not improve the model fit by a statistically significant amount. 
Further, regarding the commenter's assertion that technological 
advancements in the mining industry may reduce exposure levels, these 
reductions are accounted for in the models, which use recent exposure 
data.
b. NMRD Mortality: Park et al. (2002)
    In addition to causing silicosis, exposure to respirable 
crystalline silica causes increased risks of other NMRD. These include 
chronic obstructive pulmonary disease (COPD), which includes chronic 
bronchitis, emphysema, and combinations of the two, and is a cause of 
chronic airways obstruction. COPD is characterized by airflow 
limitation that is usually progressive and not fully reversible. OSHA 
reviewed several studies of NMRD morbidity and used a study by Park et 
al. (2002) to assess NMRD risk. Checkoway et al. (1997) originally 
studied a California diatomaceous earth cohort for which Park et al. 
(2002) then analyzed the effect of respirable crystalline silica 
exposures on the development of NMRD. The authors quantified the 
relationship between exposure to cristobalite and mortality from NMRD 
(OSHA, 2013b, page 295).
    The California diatomaceous earth cohort consisted of 2,570 
diatomaceous earth workers employed for 12 months or more from 1942 to 
1994. As noted above, Park et al. (2002) was interested in the 
relationship between cristobalite exposure and mortality from chronic 
lung disease other than cancer (LDOC). LDOC included chronic diseases 
such as pneumoconiosis (which included silicosis), chronic bronchitis, 
and emphysema, but excluded pneumonia and other infectious diseases. 
The researchers selected LDOC as the health endpoint for three reasons. 
First, increased mortality from LDOC had been documented among 
respirable crystalline silica-exposed workers in several industry 
sectors, including gold mining, pottery, granite, and foundry 
industries. Second, the authors pointed to the likelihood that 
silicosis as a cause of death is often misclassified as emphysema or 
chronic bronchitis. Third, the number of deaths from the diatomaceous 
earth worker cohort that were attributed to silicosis was too small 
(10) for analysis. Industrial hygiene data for the cohort were 
available from the employer for total dust, respirable crystalline 
silica (mostly cristobalite), and asbestos. Smoking information was 
available for about 50 percent of the cohort and for 22 of the 67 LDOC 
deaths available for analysis, permitting Park et al. (2002) to 
partially adjust for smoking (OSHA, 2013b, pages 295-296).
    Park et al. (2002) used the exposure assessment previously reported 
by Seixas et al. (1997) and used by Rice et al. (2001) to estimate 
cumulative

[[Page 28264]]

respirable crystalline silica exposures for each worker in the cohort 
based on detailed work history files. The average respirable 
crystalline silica concentration for the cohort was 290 [micro]g/m\3\ 
(0.29 mg/m\3\) over the period of employment (Seixas et al., 1997). The 
total respirable dust concentration in the diatomaceous earth plant was 
3,550 [micro]g/m\3\ (3.55 mg/m\3\) before 1949 and declined by more 
than 10-fold after 1973, to 290 [micro]g/m\3\ (0.29 mg/m\3\) (Seixas et 
al., 1997). The concentration of respirable crystalline silica in the 
dust ranged from 1 to 25 percent and was dependent on the location 
within the worksite. It was lowest at the mine and greatest in the 
plant where the raw ore was calcined into final product. The average 
cumulative exposure values for total respirable dust and respirable 
crystalline silica were 7,310 [micro]g/m\3\-year (7.31 mg/m\3\-year) 
and 2,160 [micro]g/m\3\-year (2.16 mg/m\3\-year), respectively. The 
authors also estimated cumulative exposure to asbestos (OSHA, 2013b, 
page 296).
    Using Poisson regression models and Cox proportional hazards 
models, the authors fit the same series of relative rate exposure-
response models that were evaluated by Rice et al. (2001) for lung 
cancer (i.e., log-linear, log-square root, log-quadratic, linear 
relative rate, a power function, and a shape function). In general 
form, the relative rate model was:

Rate = exp(a0) x [fnof](E),

where exp(a0) is the background rate and E is the cumulative 
respirable crystalline silica exposure. Park et al. (2002) also 
employed an additive excess rate model of the form:

Rate = exp(a0) + exp(aE),

    Relative or excess rates were modeled using internal controls and 
adjusting for age, calendar time, ethnicity, and time since first entry 
into the cohort. In addition, relative rate models were evaluated using 
age- and calendar time-adjusted external standardization to U.S. 
population mortality rates for 1940 to 1994 (OSHA, 2013b, page 296).
    There were no LDOC deaths recorded among workers having cumulative 
exposures above 32,000 [micro]g/m\3\-years (32 mg/m\3\-years), causing 
the response to level off or decline in the highest exposure range. The 
authors believed the most likely explanation for this observation 
(which was also observed in their analysis of silicosis morbidity in 
this cohort) was some form of survivor selection, possibly smokers or 
others with compromised respiratory function leaving work involving 
extremely high dust concentrations. These authors suggested several 
alternative explanations. First, there may have been a greater 
depletion of susceptible populations in high dust areas. Second, there 
may have been greater misclassification of exposures in the earlier 
years where exposure data were lacking (and when exposures were 
presumably the highest) (OSHA, 2013b, pages 296-297).
    Therefore, Park et al. (2002) performed exposure-response analyses 
that restricted the dataset to observations where cumulative exposures 
were below 10,000 [micro]g/m\3\-years (10 mg/m\3\-years). This is a 
level more than four times higher than that resulting from 45 years of 
exposure to the former OSHA PEL for cristobalite (which was 50 
[micro]g/m\3\ (0.05 mg/m\3\) when cristobalite was the only polymorph 
present). These researchers also conducted analyses using the full 
dataset (OSHA, 2013b, page 297).
    Model fit was assessed by evaluating the decrease in deviance 
resulting from addition of the exposure term, and cubic-spline models 
were used to test for smooth departures from each of the model forms 
described. Park et al. (2002) found that both lagged and unlagged 
models fit well, but unlagged models provided a better fit. In 
addition, they believed that unlagged models were biologically 
plausible in that recent exposure could contribute to LDOC mortality. 
The Cox proportional hazards models yielded results that were similar 
to those from the Poisson analysis. Consequently, only the results from 
the Poisson analysis were reported. In general, the use of external 
adjustments for age and calendar time yielded considerably improved fit 
over models using internal adjustments. The additive excess rate model 
also proved to be clearly inferior compared to the relative rate 
models. With one exception, the use of cumulative exposure as the 
exposure metric consistently provided better fits to the data than did 
intensity of exposure (i.e., cumulative exposure divided by duration of 
exposure). As to the exception, when the highest-exposure cohort 
members were included in the analysis, the log-linear model produced a 
significantly improved fit with exposure intensity as the exposure 
metric, but a poor fit with cumulative exposure as the metric (OSHA, 
2013b, page 297).
    Among the models based on the restricted dataset [excluding 
observations with cumulative exposures greater than 10,000 [micro]g/
m\3\-years (10 mg/m\3\-years)], the best-fitting model with a single 
exposure term was the linear relative rate model using external 
adjustment. Most of the other single-term models using external 
adjustment fit almost as well. Of the models with more than one 
exposure term, the shape model provided no improvement in fit compared 
with the linear relative rate model. The log-quadratic model fit 
slightly better than the linear relative rate model, but Park et al. 
(2002) did not consider the gain in fit sufficient to justify an 
additional exposure term in the model (OSHA, 2013b, page 297).
    Based on its superior fit to the cohort data, Park et al. (2002) 
selected the linear relative rate model with external adjustment and 
use of cumulative exposure as the basis for estimating LDOC mortality 
risks among exposed workers. Competing mortality was accounted for 
using U.S. death rates published by the National Center for Health 
Statistics (1996). The authors estimated the lifetime excess risk for 
white men exposed to respirable crystalline silica (mainly 
cristobalite) for 45 years at 50 [micro]g/m\3\ (0.05 mg/m\3\) to be 54 
deaths per 1,000 workers (95% CI: 17-150) using the restricted dataset, 
and 50 deaths per 1,000 using the full dataset. For exposure to 100 
[micro]g/m\3\ (0.1 mg/m\3\), they estimated 100 deaths per 1,000 using 
the restricted dataset, and 86 deaths per 1,000 using the full dataset. 
The CIs were not reported (OSHA, 2013b, page 297).
    The estimates of Park et al. (2002) were about eight to nine times 
higher than those that were calculated for the pooled analysis of 
silicosis mortality (Mannetje et al., 2002b). Also, these estimates are 
not directly comparable to those from Mannetje et al. (2002b) because 
the mortality endpoint for the Park et al. (2002) analysis was death 
from all non-cancer lung diseases beyond silicosis (including 
pneumoconiosis, emphysema, and chronic bronchitis). In the pooled 
analysis by Mannetje et al. (2002b), only deaths coded as silicosis or 
other pneumoconiosis were included (OSHA, 2013b, pages 297-298).
    Less than 25 percent of the LDOC deaths in the Park et al. (2002) 
analysis were coded as silicosis or other pneumoconiosis (15 of 67). As 
noted by Park et al. (2002), it is likely that silicosis as a cause of 
death is often misclassified as emphysema or chronic bronchitis 
(although COPD is part of the spectrum of disease caused by respirable 
crystalline silica exposure and can occur in the absence of silicosis). 
Thus, the selection of deaths by Mannetje et al. (2002b) may have 
underestimated the true risk of silicosis mortality. The analysis by 
Park et al. (2002) would have more fairly captured the total 
respiratory mortality risk from all non-malignant causes, including

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silicosis and chronic obstructive pulmonary disease. Furthermore, Park 
et al. (2002) used untransformed cumulative exposure in a linear model 
compared to the log-transformed cumulative exposure metric used by 
Mannetje et al. (2002b). This would have caused the exposure-response 
relationship to flatten in the higher exposure ranges (OSHA, 2013b, 
page 298).
    It is also possible that some of the difference between Mannetje et 
al.'s (2002b) and Park et al.'s (2002) risk estimates reflected factors 
specific to the nature of exposure among diatomaceous earth workers 
(e.g., exposure to cristobalite vs. quartz). However, neither the 
cancer risk assessments nor assessments of silicosis morbidity 
supported the hypothesis that cristobalite is more hazardous than 
quartz (OSHA, 2013b, page 298).
    Based on the available risk assessments for silicosis mortality, 
OSHA believed that the estimates from the pooled study by Mannetje et 
al.'s (2002b) likely underestimated mortality risk given that the study 
only counted deaths where silicosis was specifically identified on 
death certificates, which are prone to misclassification. In contrast, 
the risk estimates provided by Park et al. (2002) for the diatomaceous 
earth cohort would have captured some of this misclassification and 
included risks from other lung diseases (e.g., emphysema, chronic 
bronchitis) that have been associated with respirable crystalline 
silica exposure. Therefore, OSHA believed that the Park et al. (2002) 
study provided a better basis for estimating the respirable crystalline 
silica-related risk of NMRD mortality, including that from silicosis. 
Based on Park et al.'s (2002) linear relative rate model [RR = 1 + 
[beta]x, where [beta] = 0.5469 (no standard error reported) and x = 
cumulative exposure], OSHA used a life table analysis to estimate the 
lifetime excess NMRD mortality through age 85. For this analysis, OSHA 
used all-cause and cause-specific background mortality rates for all 
males (National Center for Health Statistics, 2009). Background rates 
for NMRD mortality were based on rates for ICD-10 codes J40-J47 
(chronic lower respiratory disease) and J60-J66 (pneumoconiosis). OSHA 
believed that these corresponded closely to the ICD-9 disease classes 
(ICD 490-519) used by the original researchers. According to CDC 
(2001), background rates for chronic lower respiratory diseases were 
increased by less than five percent because of the reclassification to 
ICD-10. From the life table analysis, OSHA estimated that the excess 
NMRD risk due to respirable crystalline silica exposure at the former 
general industry PEL (100 [micro]g/m\3\) and at OSHA's final PEL (50 
[micro]g/m\3\) for 45 years are 83 and 43 deaths per 1,000, 
respectively. For exposure at the former construction/shipyard exposure 
limit, OSHA estimated that the excess NMRD risk ranged from 188 to 321 
deaths per 1,000 (OSHA, 2013b, page 298).
    Following its own independent review, MSHA agrees with and has 
followed the rationale presented by OSHA in its selection of the Park 
et al. (2002) model to estimate NMRD mortality risk in miners.
    MSHA used a life table analysis to estimate the lifetime excess 
NMRD mortality through age 80. MSHA used the Park et al. (2002) model 
to estimate age-specific NMRD mortality risk as 1 + 0.5469 * cumulative 
exposure. MSHA used all-cause and cause-specific background mortality 
rates for all males for 2018 (National Center for Health Statistics, 
Underlying Cause of Death 2018 on CDC WONDER Online Database, released 
in 2020b). Background rates for NMRD mortality were based on rates for 
ICD-10 codes J40-J47 (chronic lower respiratory disease) and J60-J66 
(pneumoconiosis).
    A state mining association cited CDC data to state that the largest 
decrease in pneumoconiosis deaths over the 1999-2018 time period was in 
the coal mining industry, with a decrease of 69.6 percent, and the 
largest increase was in the OSHA construction sector (Bell and Mazurek, 
2020) (Document ID 1368). This commenter also stated that, beyond the 
CDC data, there is little understanding of pneumoconiosis case 
attribution, such as what percentage of cases were specifically due to 
mining-related employment compared to non-mining activities that might 
lead to harmful exposure. The commenter's point that it is difficult to 
correctly attribute pneumoconiosis is precisely why MSHA's FRA has 
relied on peer-reviewed epidemiological studies, which control for 
confounders where necessary and quantify the precise exposure-response 
relationship. Regarding pneumoconiosis, the cited article was about 
declining pneumoconiosis deaths in particular. Other sources, including 
analysis by NIOSH, show that the prevalence of pneumoconiosis illness 
has risen substantially among miners since the 1990s (NIOSH, 2021d). 
This same trend in pneumoconiosis illness among coal miners was also 
mentioned by three other commenters--the ACLC, Appalachian Voices, and 
the UMWA (Document ID 1445; 1425; 1398). While it may be true that 
prevalence of pneumoconiosis deaths decreased among the entire U.S. 
population during this period, trends in pneumoconiosis deaths tend to 
lag trends in pneumoconiosis illness because people can live many years 
with the disease prior to death. The increasing prevalence of the 
illness among miners indicates that pneumoconiosis deaths also are 
expected to rise in the future. In addition, trends among the full U.S. 
population may not reflect trends among miners in particular, since the 
mining workforce has decreased in size since the 1990s. Thus, MSHA does 
not believe that pneumoconiosis illnesses or deaths among coal miners 
would decline in the future in the absence of this rule and, therefore, 
affirms that the final rule is needed to protect the health of all 
miners from various respirable crystalline silica-related diseases.
4. Lung Cancer Mortality
    Since the publication of OSHA's final rule in 2016, NIOSH has 
published two documents concerning occupational carcinogens, Chemical 
Carcinogen Policy (2017b) and Practices in Occupational Risk Assessment 
(2019a). NIOSH will no longer set recommended exposure levels for 
occupational carcinogens. Instead, NIOSH intends to develop risk 
management limits for carcinogens (RML-Cas) to acknowledge that, for 
most carcinogens, there is no known safe level of exposure. An RML-CA 
is a reasonable starting place for controlling exposures. An RML-CA 
limit is based on a daily maximum 8-hour TWA concentration of a 
carcinogen above which a worker should not be exposed (NIOSH, 2017b, 
page vi). RML-Cas for occupational carcinogens are established at the 
estimated 95% lower confidence limit on the concentration (e.g., dose) 
corresponding to 1 in 10,000 (10-4) lifetime excess risk 
(when analytically possible to measure) (NIOSH, 2019a). NIOSH stated 
that in order to incrementally move toward a level of exposure to 
occupational chemical carcinogens that is closer to background, NIOSH 
will begin issuing recommendations for RML-Cas that would advise 
employers to take additional action to control chemical carcinogens 
when workplace exposures result in excess risks greater than 
10-4 (NIOSH, 2017b, page vi).
    MSHA used the Miller et al. (2007) and Miller and MacCalman (2010) 
studies to estimate lung cancer mortality risk in miners. In British 
coal miners, excess lung cancer mortality was studied through the end 
of 2005 in a cohort of 17,800 miners (Miller et al., 2007; Miller and 
MacCalman, 2010). By that time, the cohort had accumulated

[[Page 28266]]

516,431 person-years of observation (an average of 29 years per miner), 
with 10,698 deaths from all causes. Overall lung cancer mortality was 
elevated (Standard Mortality Ratio (SMR) = 115.7, 95% CI: 104.8-127.7), 
and a positive exposure-response relationship with respirable 
crystalline silica exposure was determined from Cox regression after 
adjusting for smoking history. Three strengths of this study were: (1) 
the detailed time-exposure measurements of quartz and total mine dust, 
(2) detailed individual work histories, and (3) individual smoking 
histories. For lung cancer, analyses based on Cox regression provided 
strong evidence that, for these coal miners, although quartz exposures 
were associated with increased lung cancer risk, simultaneous exposures 
to coal dust did not cause increased lung cancer risk (OSHA 2016a, 81 
FR 16286, 16308).
    Miller et al. (2007) and Miller and MacCalman (2010) conducted a 
follow-up study of cohort mortality, begun in 1970. Their previous 
report on mortality presented a follow-up analysis on 18,166 coal 
miners from 10 British coal mines followed through the end of 1992 
(Miller et al., 1997). The 2 reports from 2007 and 2010 analyzed the 
mortality experience of 17,800 of these miners (18,166 minus 346 men 
whose vital status could not be determined) and extended the analysis 
through the end of 2005. Causes of deaths that were of particular 
interest included pneumoconiosis, other NMRD, lung cancer, stomach 
cancer, and tuberculosis. The researchers noted that no additional 
exposure measurements were included in the updated analysis, since all 
the mines had closed by the mid-1980s. However, some of these men might 
have had additional exposure at other mines or facilities not reported 
in this study (OSHA, 2013b, page 287).
    This cohort mortality study used Cox proportional hazards 
regression methods which controlled for a variety of external and 
internal factors. The external controls included British administrative 
regional age-, time-, and cause-specific mortality rates from which to 
calculate SMRs. The internal controls included each miner's age, 
smoking status, and detailed dust and respirable crystalline silica 
(quartz) time-dependent exposure measurements. Cox regression analyses 
were done in stages, with the initial analyses used to establish what 
factors were required for baseline adjustment (OSHA, 2013b, page 287).
    For the analysis using external mortality rates, the all-cause 
mortality SMR from 1959 through 2005 was 100.9 (95% CI: 99.0-102.8), 
based on all 10,698 deaths. However, these SMRs were not uniform over 
time. For the period from 1990-2005, the SMR was 109.6 (95% CI:106.5-
112.8), while the ratios for previous periods were less than 100. This 
pattern of increasing SMRs in the recent past was also seen for cause-
specific deaths from chronic bronchitis, SMR = 330.0 (95% CI:268.1-
406.2); tuberculosis, SMR = 193.4 (95% CI: 86.9-430.5); cardiovascular 
disease, SMR = 106.6 (95% CI: 102.0-111.5); all cancers, SMR = 107.1 
(95% CI:101.3-113.2); and lung cancer, SMR = 115.7 (95% CI: 104.8-
127.7). The SMR for NMRD was 142.1 (95% CI: 132.9-152.0) in this recent 
period and remained highly statistically significant. In their previous 
analysis on mortality from lung cancer, reflecting follow-up through 
1995, Miller et al. (1997) had not found any increase in the risk of 
lung cancer mortality (OSHA, 2013b, page 287).
    OSHA reported that Miller and MacCalman (2010) used these analyses 
to estimate relative risks for a lifetime exposure of 5 gram-hours/m\3\ 
(ghm-3) to quartz (OSHA, 2013b, page 288). This is 
equivalent to approximately 55 [micro]g/m\3\ (0.055 mg/m\3\) for 45 
years, assuming 2,000 hours per year of exposure and/or 100 
ghm-3 total dust. The authors estimated relative risks (see 
Miller and MacCalman (2010), Table 4, page 9) for various causes of 
death including pneumoconiosis, COPD, ischemic heart disease, lung 
cancer, and stomach cancer. Their results were based on models with 
single exposures to dust or respirable crystalline silica (quartz) or 
simultaneous exposures to both, with and without 15-year lag periods. 
Generally, the risk estimates were slightly greater using a 15-year lag 
period.
    For the models using only quartz exposures with a 15-year lag, 
pneumoconiosis, RR = 1.21 (95% CI: 1.12-1.31); COPD, RR = 1.11 (95% CI: 
1.05-1.16); and lung cancer, RR = 1.07 (95% CI: 1.01-1.13) showed 
statistically significant increased risks.
    For lung cancer, analyses based on these Cox regression methods 
provided strong evidence that, for these coal miners, quartz exposures 
were associated with increased lung cancer risk, but simultaneous 
exposures to coal dust were not associated with increased lung cancer 
risk. The relative risk (RR) estimate for lung cancer deaths using coal 
dust with a 15-year lag in the single exposure model was 1.03 (95% CI: 
0.96 to 1.10). In the model using both quartz and coal mine dust 
exposures, the RR based on coal dust decreased to 0.91, while that for 
quartz exposure remained statistically significant, increasing to a RR 
= 1.14 (95% CI: 1.04 to 1.25). According to Miller and MacCalman 
(2010), other analyses have shown that exposure to radon or diesel 
fumes was not associated with an increased cancer risk among British 
coal miners (OSHA, 2013b, page 288).
    The RRs in the Miller and MacCalman (2010) report were used to 
estimate excess lung cancer risk for OSHA's purposes. Life table 
analyses were done as in the other studies above. Based on the RR of 
1.14 (95% CI: 1.04-1.25) for a cumulative exposure of 5 
ghm-3, the regression slope was recalculated as [beta] = 
0.0524 per 1,000 [micro]g-years (per mg/m-3-years) and used 
in the life table program. Similarly, the 95-percent CI on the slope 
was 0.0157-0.08926. From this study, the lifetime (to age 85) risk 
estimates for 45 years of exposure to 50 [micro]g/m\3\ (0.05 mg/m\3\) 
and 100 [micro]g/m\3\ (0.100 mg/m\3\) respirable crystalline silica 
were 6 and 13 excess lung cancer deaths per 1,000 workers, 
respectively. These lung cancer risk estimates were less by about two- 
to four-fold than those estimated from the other cohort studies 
described above.
    However, three factors might explain these differences. First, 
these estimates were adjusted for individual smoking histories so any 
smoking-related lung cancer risk (or smoking-respirable crystalline 
silica interaction) that might possibly be attributed to respirable 
crystalline silica exposure in the other studies was not reflected in 
the risk estimates derived from the study of these coal miners. Second, 
these coal miners had significantly increased risks of death from other 
lung diseases, which may have decreased the lung cancer-susceptible 
population. Of note, for example, were the higher increased SMRs for 
NMRD during the years 1959-2005 for this cohort (Miller and MacCalman, 
2010, Table 2, Page 7). Third, the difference in risk seen in these 
coal miners may have been the result of differences in the toxicity of 
quartz present in the coal mines as compared to the work environments 
of the other cohorts. One Scottish mine (Miller et al., 1998) in this 
10-mine study had been cited as having presented ``unusually high 
exposures to [freshly fractured] quartz.'' However, this was also 
described as an atypical exposure among miners working in the 10 mines. 
Miller and MacCalman (2010) stated that increased quartz-related lung 
cancer risk in their cohort was not confined to that Scottish mine 
alone. They also stated, ``The general nature of some quartz exposures 
in later years . . . may have been different from earlier periods when 
coal extraction was

[[Page 28267]]

largely manual . . .'' (OSHA, 2013b, page 288).
    All these factors in this mortality analysis for the British coal 
miner cohort could have combined to yield an underestimation of lung 
cancer risk estimates. However, OSHA believed that these coal miner-
derived estimates were credible because of the quality of several study 
factors relating to both study design and conduct. In terms of design, 
the cohort was based on union rolls with very good participation rates 
and good reporting. The study group also included over 17,000 miners, 
with an average of nearly 30 years of follow-up, and about 60 percent 
of the cohort had died. Just as important was the high quality and 
detail of the exposure measurements, both of total dust and quartz. 
However, one exposure factor that may have biased the estimates upward 
was the lack of exposure information available for the cohort after the 
mines closed in the mid-1980s. Since the mortality ratio for lung 
cancer was higher during the last study period, 1990-2005, this period 
contributed to the increased lung cancer risk. It is possible that any 
quartz exposure experienced by the cohort after the mines had closed 
could have accelerated either death or malignant tumor (lung cancer) 
growth. By not accounting for this exposure, if there was any, the risk 
estimates would have been biased upwards. Although the 15-year lag 
period for quartz exposure used in the analyses provided slightly 
higher risk estimates than use of no lag period, the better fit seen 
with the lag may have been artificial. This may have occurred because 
there appeared to have been no exposures during the recent period when 
risks were seen to have increased (OSHA, 2013b, page 289).
    MSHA believes, as OSHA did, that this study of a large British coal 
mining cohort provides convincing evidence of the carcinogenicity of 
respirable crystalline silica. This large cohort study, with almost 30 
years of follow-up, demonstrated a positive exposure-response after 
adjusting for smoking histories. Additionally, the authors state that 
there was no evidence that exposure to potential confounders such as 
radon and diesel exhaust were associated with excess lung cancer risk 
(Miller and MacCalman (2010, page 270). MSHA is relying on the British 
studies conducted by Miller et al. (2007) as well as Miller and 
MacCalman (2010) to estimate the lung cancer risk in all miners.
    MSHA found these two studies suitable for use in the quantitative 
characterization of health risks to exposed miners for several reasons. 
First, their study populations were of sufficient size to provide 
adequate statistical power to detect low levels of risk. Second, 
sufficient quantitative exposure data were available over a sufficient 
span of time to characterize cumulative respirable crystalline silica 
exposures of cohort members. Third, the studies either adjusted for or 
otherwise adequately addressed confounders such as smoking and exposure 
to other carcinogens. Finally, these researchers developed quantitative 
assessments of exposure-response relationships using appropriate 
statistical models or otherwise provided sufficient information that 
permits MSHA to do so.
    MSHA implemented the risk model in its life table analysis so that 
the use of background rates of lung cancer and assumptions regarding 
length of exposure and lifetime were consistent across models. Thus, 
MSHA was able to estimate lung cancer risks associated with exposure to 
specific levels of respirable crystalline silica of interest to the 
Agency. MSHA used the Miller et al. (2007) and Miller and MacCalman 
(2010) model to estimate age-specific cumulative lung cancer mortality 
risk as EXP(0.0524 * cumulative exposure), lagged 15 years.
    MSHA's FRA uses risk estimates derived from 10 coal mines in the 
U.K. (Miller et al., 2007; Miller and MacCalman, 2010). These 
researchers developed regression analyses for time-dependent estimates 
of individual exposures to respirable dust. Their analyses were based 
on the detailed individual exposure estimates of the PFR program. To 
estimate mortality risk for lung cancer from the pooled cohort 
analysis, MSHA used the same life table approach as OSHA. However, for 
this life table analysis, MSHA used 2018 mortality rates for U.S. males 
(i.e., all-cause and background lung cancer). The 2018 lung cancer 
death rates were based on the ICD-10 classification of diseases codes, 
C34.0, C34.2, C34.1, C34.3, C34.8, and C34.9. Lifetime risk estimates 
reflected excess risk through age 80. To estimate lung cancer risks, 
MSHA used the log-linear relative risk model, exp (0.0524 x cumulative 
exposure), lagged 15 years. The coefficient for this model was 0.0524 
(OSHA, 2013b, page 290).
    MSHA's use of Miller and MacCalman (2010) to estimate lung-cancer 
mortality risk is in contrast to OSHA's use of Steenland et al. (2001a) 
to estimate lung-cancer mortality risk. There are several reasons for 
MSHA's use of Miller and MacCalman (2010). First, it covers coal 
mining-specific cohort large enough (with 45,000 miners) to provide 
adequate statistical power to detect low levels of risk, and it covers 
an extended follow-up period (1959-2006). Second, the study provided 
data on cumulative exposure of cohort members and adjusted for or 
addressed confounders such as smoking and exposure to other 
carcinogens. Finally, it developed quantitative assessments of 
exposure-response relationships using appropriate statistical models or 
otherwise provided sufficient information that permitted MSHA to do so.
    NVMA criticized MSHA's reliance on the Miller and MacCalman (2010) 
study because, according to the commenter, it primarily focused on coal 
miners, does not consider technological advancements in the mining 
sector, and is ``insufficient for justifying the implementation of a 
rule of this magnitude on MNM mines'' (Document ID1441). Commenters 
from the Black Lung Clinics and UMWA were in support of MSHA's use of 
Miller and MacCalman (2010) in assessing lung cancer mortality 
(Document ID 1410; 1398).
    MSHA does not agree that reliance on Miller and MacCalman (2010) 
refutes the risk of material impairment of health to MNM miners. MSHA 
considered several other studies on lung cancer mortality, which 
covered a variety of populations aside from coal miners, including gold 
miners, diatomaceous earth workers, granite workers, industrial sand 
employees, pottery workers, tin miners, and tungsten miners. As OSHA 
showed in its QRA, the estimates from Miller and MacCalman (2010) were 
lower by roughly two- to four-fold than the estimates from other cohort 
studies. In selecting Miller and MacCalman (2010), MSHA chose a study 
that found smaller risks than the other studies. The Miller and 
MacCalman (2010) study has many strengths, including the fact that it 
had very high participation rates, with over 17,000 miners and nearly 
30 years of follow up. In addition to detailed exposure information, 
the study also used individual smoking histories to adjust its 
estimates for the effect of smoking. Further, exposure changes owing to 
technological advancements are accounted for by MSHA's models which use 
recent exposure data.
    Urging MSHA to lower the PEL to 25 [micro]g/m\3\, the AIHA 
commented that the work by Steenland and Sanderson should not be 
discounted (Document ID 1351). The commenter said that a 2001 Steenland 
and Sanderson study showed a significant increase in mortality risk 
from lung cancer at average exposure levels greater than 65 [micro]g/
m\3\, indicating

[[Page 28268]]

that 50 [micro]g/m\3\ would probably not be protective of workers' 
health.
    MSHA clarifies that, although it departed from OSHA's risk 
assessment by using the exposure-response model from Miller and 
MacCalman (2010) to assess lung cancer mortality, Steenland and 
Sanderson's work was not discounted. MSHA relied on Steenland and 
Sanderson in the standalone Health Effects document and the FRA. 
Further, MSHA acknowledges that there remains a risk of material 
impairment of health at the revised PEL; however, a further reduction 
in the PEL is not achievable at all mines (see MSHA's Technological 
Feasibility analysis). MSHA concludes that the final PEL will provide a 
substantial reduction in the risk of material impairment of health to 
miners.
5. ESRD Mortality
    Several epidemiological studies have found statistically 
significant associations between occupational exposure to respirable 
crystalline silica and renal disease, although others have failed to 
find a statistically significant association. These studies are 
discussed in the standalone Health Effects document (Section 14). 
Possible mechanisms suggested for respirable crystalline silica-induced 
renal disease included a direct toxic effect on the kidney, deposition 
of immune complexes (IgA) in the kidney following respirable 
crystalline silica-related pulmonary inflammation, and an autoimmune 
mechanism (Gregorini et al., 1993; Calvert et al., 1997; Parks et al., 
1999; Steenland, 2005b) (OSHA 2016a, 81 FR 16286, 16310).
    MSHA, like OSHA, chose the Steenland et al. (2002a) study to 
include in the FRA. In a pooled cohort analysis, Steenland et al. 
(2002a) combined the industrial sand cohort from Steenland et al. 
(2001b), the gold mining cohort from Steenland and Brown (1995a), and 
the Vermont granite cohort studies by Costello and Graham (1988). All 
three were included in portions of OSHA's PQRA for other health 
endpoints: under lung cancer mortality in Steenland et al. (2001a) and 
under silicosis mortality in the related work of Mannetje et al. 
(2002b). In all, the combined cohort consisted of 13,382 workers with 
exposure information available for 12,783. The analysis demonstrated 
statistically significant exposure-response trends for acute and 
chronic renal disease mortality with quartiles of cumulative respirable 
crystalline silica exposure (OSHA 2016a, 81 FR 16286, 16310).
    The average duration of exposure, cumulative exposure, and 
concentration of respirable crystalline silica for the pooled cohort 
were 13.6 years, 1,200 [micro]g/m\3\-years (1.2 mg/m-3-
years), and 70 [micro]g/m\3\ (0.07 mg/m\3\), respectively. Renal 
disease risk was most prevalent among workers with cumulative exposures 
of 500 [micro]g/m\3\ or more (Steenland et al., 2002a). SMRs (compared 
to the U.S. population) for renal disease (acute and chronic 
glomerulonephritis, nephrotic syndrome, acute and chronic renal 
failure, renal sclerosis, and nephritis/nephropathy) were statistically 
significant and elevated based on multiple cause of death data (SMR 
1.28, 95% CI: 1.10-1.47, 194 deaths) and underlying cause of death data 
(SMR 1.41, 95% CI: 1.05-1.85, 51 observed deaths) (OSHA, 2013b, page 
315).
    A nested case-control analysis was also performed which allowed for 
more detailed examination of exposure-response. This analysis included 
95 percent of the cohort for which there were adequate work history and 
quartz exposure data. This analysis included 50 cases for underlying 
cause mortality and 194 cases for multiple-cause mortality. Each case 
was matched by race, sex, and age within 5 years to 100 controls from 
the cohort. Exposure-response trends were examined in a categorical 
analysis where renal disease mortality of the cohort divided by 
exposure quartile was compared to U.S. rates (OSHA, 2013b, page 315).
    In this analysis, statistically significant exposure-response 
trends for SMRs were observed for multiple-cause (p<0.000001) and 
underlying cause (p=0.0007) mortality (Steenland et al., 2002a, Table 
1, Page 7).
    With the lowest exposure quartile group serving as a referent, the 
case-control analysis showed monotonic trends in mortality with 
increasing cumulative exposure. Conditional regression models using 
log-cumulative exposure fit the data better than cumulative exposure 
(with or without a 15-year lag) or average exposure. Odds ratios by 
quartile of cumulative exposure were 1.00, 1.24, 1.77, and 2.86 
(p=0.0002) for multiple cause analyses and 1.00, 1.99, 1.96, and 3.93 
for underlying cause analyses (p=0.03) (Steenland et al., 2002a, Table 
2, Page 7). For multiple-cause mortality, the exposure-response trend 
was statistically significant for cumulative exposure (p=0.004) and 
log-cumulative exposure (p=0.0002), whereas for underlying cause 
mortality, the trend was statistically significant only for log-
cumulative exposure (p=0.03). The exposure-response trend was 
homogeneous across the three cohorts and interaction terms did not 
improve model fit (OSHA, 2013b, pages 216, 315).
    Based on the exposure-response coefficient for the model with the 
log of cumulative exposure, Steenland (2005b) estimated lifetime excess 
risks of death (age 75) over a working life (age 20 to 65). At 100 
[micro]g/m\3\ (0.1 mg/m\3\) respirable crystalline silica, this risk 
was 5.1 percent (95% CI 3.3-7.3) for ESRD based on 23 cases (Steenland 
et al., 2001b). It was 1.8 percent (95% CI 0.8-9.7) for kidney disease 
mortality (underlying), based on 51 deaths (Steenland et al., 2002a) 
above a background risk of 0.3 percent (OSHA, 2013b, page 216).
    MSHA notes that these studies added to the evidence that renal 
disease is associated with respirable crystalline silica exposure. 
Statistically significant increases in odds ratios and SMRs were seen 
primarily for cumulative exposures of >500 [micro]g/m\3\-years (0.5 mg/
m\3\-years). Steenland (2005b) noted that this could have occurred from 
working for 5 years at an exposure level of 100 [micro]g/m\3\ (0.1 mg/
m\3\) or 10 years at 50 [micro]g/m\3\ (0.05 mg/m\3\).
    OSHA had a large body of evidence, particularly from the three-
cohort pooled analysis (Steenland et al., 2002a), on which to conclude 
that respirable crystalline silica exposure increased the risk of renal 
disease mortality and morbidity. The pooled analysis by Steenland et 
al. (2002a) involved a large number of workers from three cohorts with 
well-documented, validated job-exposure matrices. These researchers 
found a positive, monotonic increase in renal disease risk with 
increasing exposure for underlying and multiple cause data. Thus, the 
exposure and work history data were unlikely to have been seriously 
misclassified. However, there are considerably less data available for 
renal disease than there are for silicosis mortality and lung cancer 
mortality. Nevertheless, OSHA concluded that the underlying data were 
sufficient to provide useful estimates of risk and included the 
Steenland et al. (2002a) analysis in its PQRA (OSHA, 2013b, pages 229, 
316).
    To estimate renal disease mortality risk from the pooled cohort 
analysis, OSHA implemented the same life table approach as was done for 
the assessments on lung cancer and NMRD. However, for this life table 
analysis, OSHA used 1998 all-cause and background renal mortality rates 
for U.S. males, rather than the 2006 rates used for lung cancer and 
NMRD. The 1998 rates were based on the ICD-9 classification of 
diseases, which was the same as used by Steenland et al. (2002a) to 
ascertain the cause of death of workers in their study. However, U.S.

[[Page 28269]]

cause-of-death data from 1999 to present are based on the ICD-10, in 
which there were considerable changes in the classification system for 
renal diseases. According to CDC (2001), the change in the 
classification from ICD-9 to ICD-10 increased death rates for 
nephritis, nephritic syndrome, and nephrosis by 23 percent, in large 
part due to reclassifying ESRD. The change from ICD-9 to ICD-10 did not 
materially affect background rates for those diseases grouped as lung 
cancer or NMRD. Consequently, OSHA conducted its analysis of excess 
renal disease mortality associated with respirable crystalline silica 
exposure using background mortality rates for 1998. As before, lifetime 
risk estimates reflected excess risk through age 85. To estimate renal 
mortality risks, OSHA used the log-linear model with log-cumulative 
exposure that provided the best fit to the pooled cohort data 
(Steenland et al., 2002a). The coefficient for this model was 0.269 
(SE=0.120) (OSHA, 2013b, page 316). Based on the life table analysis, 
OSHA estimated that exposure to the former general industry exposure 
limit of 100 [micro]g/m\3\ and to the final exposure limit of 50 
[micro]g/m\3\ over a working life would result in a lifetime excess 
renal disease risk of 39 (95% CI: 2-200) and 32 (95% CI: 1.7-147) 
deaths per 1,000, respectively. OSHA also estimated lifetime risks 
associated with the former construction and shipyard exposure limits of 
250 and 500 [micro]g/m\3\. These lifetime excess risks ranged from 52 
(95% CI 2.2-289) to 63 (95% CI 2.5-368) deaths per 1,000 workers (OSHA, 
2013b, page 316).
    MSHA acknowledges the uncertainty associated with the divergent 
findings in the renal disease literature; however, MSHA concludes that 
the evidence supporting causality regarding renal risk outweighs the 
evidence casting doubt on that conclusion.
    Upon reviewing the PRA, the NSSGA commented that it is unclear 
whether renal disease is causally related to occupational respirable 
crystalline silica exposure (Document ID 1448, Attachment 3). The 
commenter cited a 2017 German Federal Institute for Occupational Safety 
and Health systematic review and meta-analysis on respirable 
crystalline silica and non-malignant renal disease, which concluded 
that ``while the studies of cohorts exposed to silica found elevated 
SMRs for renal disease, no clear evidence of a dose-response 
relationship emerged.'' As detailed above in Section V. Health Effects 
Summary and further discussed in MSHA's standalone Health Effects 
document, MSHA reviewed a wide variety of studies which suggest that 
occupational exposure to respirable crystalline silica increases the 
risk of renal disease, including the risk of non-malignant cases. The 
Steenland et al. (2002a) study, which was selected for modeling ESRD 
risk in the FRA, found a monotonic increase in renal disease risk with 
increasing exposures to respirable crystalline silica. MSHA believes 
that the Steenland et al. (2002a) study has several strengths, 
including (1) a large cohort with well-documented and validated job-
exposure matrices and (2) low risk of bias from exposure 
misclassification. The FRA has selected studies for modeling risks 
based on a thorough evaluation of each study's methodology. The fact 
that other studies (which MSHA did not use for modeling) may have found 
significantly elevated mortality ratios but inconclusive exposure-
response relationships does not render invalid the findings or 
methodological strengths of Steenland et al. (2002a). Thus, MSHA 
concludes that increasing exposure to respirable crystalline silica 
increases a miner's risk of renal disease and reaffirms its decision to 
model benefits stemming from reductions in ESRD mortality due to the 
final rule in the FRA.
    To estimate renal disease mortality risk from the pooled cohort 
analysis, MSHA implemented the same life table approach as OSHA. 
However, MSHA's life table analysis used 2018 all-cause and 1998 
background renal mortality rates for U.S. males. The 1998 renal death 
rates were based on the ICD-9 classification of diseases, 580-589. This 
is the same classification used by Steenland et al. (2002a) to 
ascertain the cause of death of workers in their study. Consequently, 
MSHA conducted its analysis of excess ESRD mortality risk associated 
with exposure to respirable crystalline silica using background ESRD 
mortality rates for 1998. The U.S. cause-of-death data from 2018 were 
used as well to estimate the rate of death due to all causes among the 
unexposed population. Lifetime excess risk estimates reflect the excess 
risk through age 80. To estimate ESRD excess mortality risks, MSHA used 
the log-linear model with log-cumulative exposure that provided the 
best fit to the pooled cohort data (Steenland et al., 2002a), as 
EXP(0.269*ln(cumulative exposure)). The coefficient for this model was 
0.269 (SE=0.120) (OSHA, 2013b, page 316). 6. Coal Workers' 
Pneumoconiosis (CWP) and Progressive Massive Fibrosis (PMF).
    Exposure to respirable coal mine dust causes lung diseases 
including CWP, emphysema, silicosis, and chronic bronchitis, known 
collectively as ``black lung.'' These diseases are debilitating, 
incurable, and can result in disability and premature death. There are 
no specific treatments to cure CWP or COPD. These chronic effects may 
progress even after miners are no longer exposed to coal dust.
    MSHA's 2014 Coal Dust Rule quantified benefits among coal miners 
related to reduced cases of CWP due to lower exposure limits for 
respirable coal mine dust. In the FRA, MSHA has not quantified the 
reduction in morbidity risk associated with CWP among coal miners. 
Nonetheless, MSHA believes that the final rule would reduce the excess 
risk of morbidity from this disease. Many coal miners work extended 
shifts, increasing their potential exposure to respirable crystalline 
silica; therefore, calculating exposures based on a full-shift 8-hour 
TWA would be more protective. Thus, the final rule is expected to 
provide additional reductions in CWP risk beyond those ascribed in the 
2014 Coal Dust Rule. However, exposure-response relationships based on 
respirable crystalline silica exposure are not available for CWP, so 
the reductions in this disease due to reductions in silica exposure 
cannot be quantified.
    In the FRA, PMF deaths are captured in part by silicosis mortality 
as defined by Mannetje et al. (2002b). Those PMF deaths not captured by 
the definition in Mannetje et al. are likely captured by the definition 
of NMRD mortality adopted from Park et al. (2002). Thus, the FRA fully 
characterizes the reduction in lifetime cases of PMF mortality 
including mortality due to complicated CWP and complicated silicosis. 
However, the FRA likely underestimates reduction in PMF morbidity. This 
is because the Buchanan et al. (2003) model, which was used to model 
silicosis morbidity, likely undercounts PMF due to exclusion of cases 
below the threshold of 2/1+ profusion of opacities on a chest X-ray. 
While the FRA quantifies reduction in lifetime mortality cases from CWP 
and PMF (which are included under NMRD), there are likely additional 
unquantified morbidity benefits from CWP and PMF that are not captured.
    Finally, the Appalachian Voices expressed concern that the modeling 
conducted for the rule does not incorporate data that medical clinics 
in Appalachia have reported since 2010 (Document ID 1425). This 
commenter stated that, while not all cases can be attributed directly 
to silica exposure, reporting over the last 15 years has led medical 
experts to believe that silica is a significant driver of the increased 
prevalence of severe black lung disease

[[Page 28270]]

in Central Appalachia, and that any rule designed to reduce silica 
exposure should consider data from clinics in Central Appalachia to 
ensure a more realistic accounting of current morbidity and set a high 
goal for future morbidity. This commenter urged MSHA to review data 
from black lung clinics in Central Appalachia.
    MSHA notes that comprehensive longitudinal clinical outcome data, 
paired with exposure histories, are not available for U.S. miners. MSHA 
acknowledges that these data would be useful for the purpose of 
estimating risk reductions and acknowledges that the exposure-response 
models used in this FRA are not based on current disease incidence 
among U.S. miners. While clinic data help document pneumoconiosis as an 
important problem, these data alone are not sufficient to estimate the 
reduction in excess morbidity and mortality that are specifically 
attributable to the new PEL. Calculating future miners' reduction in 
excess cases from the current disease incidence reported by clinics 
would also require those clinic patients' exposure and work histories, 
which are not available. Moreover, the data from medical clinics in 
Appalachia represent only a portion of miners whose respirable 
crystalline silica exposures may have exceeded the existing standard 
and who may have worked during a time when the coal mining industry was 
larger. The methodology of the FRA is to use peer-reviewed exposure-
response models to estimate avoided excess deaths and illnesses that 
are specifically attributable to reducing respirable crystalline silica 
exposure from, at most, the existing standard to the new PEL of 50 
[mu]g/m\3\. MSHA has not quantified reductions in simple or complicated 
CWP morbidity, as an exposure-response model for respirable crystalline 
silica and CWP is not available, and this final rule does not regulate 
levels of coal dust. Nonetheless, miners will likely see reductions in 
CWP risk, including risk of severe forms of CWP such as PMF, due to the 
final rule, since respirable crystalline silica exposure may play a 
role in development of CWP, and because concentrations of mixed coal 
dust may decrease due to this rule. These benefits associated with 
reductions in CWP mortality and morbidity are not quantified in the 
FRA.

D. Overview of Results

    Table VI-4 summarizes the FRA's main results: once all miners and 
retirees have only been exposed under the new PEL, the final rule is 
expected to result in at least 1,067 avoided deaths and 3,746 avoided 
cases of silicosis morbidity among the working and future retired miner 
population. This is a change from the PRA, which predicted at least 799 
avoided deaths and 2,809 avoided cases of silicosis morbidity in the 
working miner population. The increased avoided deaths and cases in the 
FRA are the result of changes to MSHA's risk analysis methodology; 
specifically, the inclusion of future retired miners. This 
methodological change is discussed in detail in the standalone FRA. The 
expected reductions in death and illness in the FRA are based on actual 
exposure conditions, peer-reviewed exposure-response models, and the 
assumption that miners have 45 years of employment under the new PEL 
(from the beginning of age 21 through the end of age 65) and 15 years 
of retirement (up through the end of age 80). These estimates of the 
avoided lifetime excess mortality and morbidity represent the final 
calculations based on the five selected models and the observed 
exposure data. The first group of miners that will experience the 
avoided lifetime deaths and illnesses shown in Table VI-4 is the 
population living 60 years after the start of implementation of the 
final rule. In other words, this group will only contain miners 
exclusively exposed under the final rule for the duration of their 
working lives. To calculate benefits associated with the rulemaking, 
the economic analysis monetizes avoided deaths and illnesses while 
accounting for the fact that, during the first 60 years following the 
start of implementation of the final rule, miners will have fewer 
avoided lifetime deaths and illnesses because they will have been 
exposed under both the existing standards and the new PEL.
[GRAPHIC] [TIFF OMITTED] TR18AP24.144

    Table VI-5 summarizes miners' expected percentage reductions in 
lifetime excess risk of developing or dying from certain diseases due 
to their reduced respirable crystalline silica exposure expected to 
result from implementation of the final rule. The lifetime excess risk 
reflects the probability of developing or dying from diseases over a 
maximum lifetime of 45 years of exposure during employment and 15 years 
of retirement.\25\ The excess

[[Page 28271]]

risk reduction compares (a) miners' excess health risks associated with 
respirable crystalline silica exposure at the limits included in MSHA's 
existing standards to (b) miners' excess health risks associated with 
exposure at this standard's new PEL. MSHA expects full-scale 
implementation to reduce lifetime excess mortality risk by 9.5 percent 
and to reduce lifetime excess silicosis morbidity risk by 41.9 percent. 
Excess mortality risk includes the excess risk of death due to 
silicosis, NMRD, lung cancer, and ESRD.
---------------------------------------------------------------------------

    \25\ In the model, not every miner lives through age 80, and 
deaths occur at the expected rate given the all-cause mortality 
rates and given miners' elevated mortality risk due to their 
exposure to respirable crystalline silica. Excess risks stop 
accruing after death, and the life table methodology accounts for 
these deaths. For example, only roughly half of an original cohort 
of 21-year-old miners are expected to be alive at the start of age 
80.
[GRAPHIC] [TIFF OMITTED] TR18AP24.145

    Table VI-6 presents MSHA's estimates of lifetime excess risk per 
1,000 miners at exposure levels equal to the existing standards, the 
new PEL, and the action level. These estimates are adjusted for FTE 
ratios and thus utilize cumulative exposures that more closely reflect 
the average hours worked per year.\26\ For an MNM miner who is 
presently exposed at the existing PEL of 100 [mu]g/m\3\ (and given the 
weighted average FTE ratio of 0.87), implementing the new PEL will 
lower the miner's lifetime excess risk of death by 58.8 percent for 
silicosis, 45.7 percent for NMRD (not including silicosis), 52.7 
percent for lung cancer, and 19.9 percent for ESRD. The MNM miner's 
risk of acquiring a non-fatal case of silicosis will decrease by 80.4 
percent.
---------------------------------------------------------------------------

    \26\ The FTE ratios used in these calculations are a weighted 
average of the FTE ratio for production employees and the FTE ratio 
for contract miners.
---------------------------------------------------------------------------

    For a coal miner who is currently exposed at the existing standard 
of 85.7 [mu]g/m\3\ (and given the weighted average FTE ratio of 0.99), 
implementing the new PEL will lower the miner's lifetime excess risk of 
death by 42.6 percent for silicosis mortality, 40.2 percent for NMRD 
mortality (not including silicosis), 43.4 percent for lung cancer 
mortality, and 15.8 percent for ESRD mortality. The coal miner's 
lifetime excess risk of acquiring non-fatal silicosis will decrease by 
73.8 percent. While even greater reductions would be achieved at 
exposures equal to the action level (25 [mu]g/m\3\), some residual 
risks do remain at exposures of 25 [mu]g/m\3\. Notably, at the action 
level, ESRD risk is still 20.7 per 1,000 MNM miners and 21.6 per 1,000 
coal miners. At the action level, risk of non-fatal silicosis is 16.3 
per 1,000 MNM miners and 16.9 per 1,000 coal miners.
BILLING CODE 4520-43-P

[[Page 28272]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.146

BILLING CODE 4520-43-C
    Supporting the need for the proposed rule overall, the National 
Black Lung Association (NBLA) cited a 2023 investigation (Berkes and 
Hicks, 2023), which the commenter said reported 21,000 excessive 
respirable crystalline silica dust exposures from 1986 to 2016 
(Document ID 1402). In its above review of exposure data, MSHA also 
found exposures that exceeded the new PEL. On the other hand, 
questioning the necessity of the proposed rule for the coal industry, 
the Pennsylvania Coal Alliance asserted that only 1.2 percent of the 
samples MSHA relied on for its analysis showed an exceedance of 100 
[mu]g/m\3\ (Document ID 1378).
    While coal exposure data since 2016 may indicate a recent trend of 
less frequent noncompliance, 6.9 percent of samples for coal miners 
showed an exceedance of the new PEL. As Table VI-6 demonstrates, 
reducing a coal miner's exposure from 85.7 [mu]g/m\3\ to 50 [mu]g/m\3\ 
is expected to reduce his total silicosis morbidity risk by 71 percent 
(from 189.9 to 54.2 per 1,000), reduce his silicosis mortality risk by 
43 percent (from 14.1 to 8.1 per 1,000), reduce his total NMRD 
mortality by 41 percent (from 53.2 to 31.5 per 1,000), reduce his lung 
cancer mortality risk by 43 percent (from 5.3 to 3.0 per 1,000), and 
reduce his ESRD mortality by 16 percent (from 32.3 to 27.2 per 1,000). 
Additionally, for a typical coal miner exposed between 50 [mu]g/m\3\ 
and 85.7 [mu]g/m\3\, the new PEL is expected to reduce his silicosis 
morbidity risk by 46 percent (from 79.5 to 54.3 per 1,000), reduce his 
lung cancer mortality risks by 22 percent (from 3.6 to 3.0 per 1,000), 
reduce his silicosis mortality risk by 15 percent (from 9.4 to 8.1 per 
1,000), reduce his NMRD mortality risk by 20 percent (from 37.9 to 31.5 
per 1,000), and reduce his ESRD mortality risk by 6 percent (from 28.9 
to 27.2 per 1,000). The benefits calculated in the main analysis of the 
FRA represent only those benefits of reducing exposures from, at most, 
the existing standard to the new PEL of 50 [mu]g/m\3\. Even when 
assuming compliance with the existing standard, the results of the FRA 
affirm the need for the rule for all mining industries.

E. Healthy Worker Bias

    MSHA accounted for ``healthy worker survivor bias'' in estimating 
the risks for coal and MNM miners. The healthy worker survivor bias 
causes epidemiological studies to underestimate excess risks associated 
with occupational exposures. As with most worker populations, miners 
are composed of heterogeneous groups that possess varying levels of 
background health. Over the course of miners' careers, illness tends to 
remove the most at-risk workers from the workforce prematurely, thus 
causing the highest cumulative exposures to be experienced by the 
healthiest workers who are most resistant to developing disease. 
Failing

[[Page 28273]]

to account for this imbalance of cumulative exposure across workers 
negatively biases risk estimates, thereby underestimating true risks in 
the population. Keil et al. (2018) analyzed a type of healthy worker 
bias referred to as the healthy worker survivor bias in the context of 
OSHA's 2016 life table estimates for risk associated with respirable 
crystalline silica exposure. After analyzing data from 65,999 workers 
pooled across multiple countries and industries, Keil et al. found that 
the ``healthy worker survivor bias results in a 28% underestimate of 
risk for lung cancer and a 50% underestimate for other causes of 
death,'' with risk being defined as ``cumulative incidence of mortality 
[at age 80].''
    Given that MSHA has calculated risks using the same underlying 
epidemiological studies OSHA used in 2016, the healthy worker survivor 
bias is likely impacting the estimates in Table V-6 of lifetime excess 
risk and lifetime excess cases avoided. Accordingly, as part of a 
sensitivity analysis, MSHA re-estimated risks for MNM and coal miners 
to account for the healthy worker survivor bias. MSHA adjusted for this 
effect by increasing the risk estimates of lung cancer risk by 28 
percent and increasing the risk of each other disease by 50 percent. 
This produced larger estimates of lifetime excess risk reductions and 
lifetime excess cases avoided, which are presented in FRA Table 23 
through FRA Table 26 of the FRA document. As these tables show, when 
adjusting for the healthy worker survivor bias, the new PEL will 
decrease lifetime silicosis morbidity risk by 23.9 cases per 1,000 MNM 
miners (compared to the unadjusted estimate of 15.9 cases per 1,000 MNM 
miners, see FRA Table 15 of the FRA document) and 5.8 cases per 1,000 
coal miners (compared to 3.8 cases per 1,000 coal miners, see FRA Table 
16 of the FRA document). Still accounting for the healthy worker 
survivor bias, the new PEL will decrease total morbidity by 5,131 
lifetime cases among MNM miners (compared to 3,421 cases, see FRA Table 
17 of the FRA document) and by 487 lifetime cases among coal miners 
(compared to 325 cases, see FRA Table 18 of the FRA document). Among 
the current MNM and coal mining populations, implementation of the new 
PEL during their full lives will have avoided 1,457 deaths and 126 
deaths, respectively, over their lifetimes (compared to unadjusted 
estimates of 982 deaths and 85 deaths, respectively).
    MSHA believes adjusted estimates for the healthy worker survivor 
bias are more reliable than unadjusted estimates. However, given that 
the literature does not support specific scaling factors for each of 
the health endpoints analyzed, these adjustments for the healthy worker 
survivor bias have not been incorporated into the final lifetime excess 
risk estimates that served as the basis for monetizing benefits. 
Because the monetized benefits do not account for the healthy worker 
bias, MSHA believes the reductions in lifetime excess risks and 
lifetime excess cases, as well as the monetized benefits, likely 
underestimate the true reductions and benefits attributable to the 
final rule.
    The ACLC provided comments that the agency's proposed rule would do 
little to alter the status quo (Document ID 1445). Specifically, this 
commenter cited the findings of the PRA that thousands of miners would 
continue to get sick and die from overexposure to silica dust under the 
new proposed rule (Document ID 1445). Recommending that the Agency 
should focus on entirely preventing any disability or disease from 
inhaling silica dust, the commenter urged MSHA to strengthen the 
proposed rule such that the vast majority of miner lives will be saved 
over the coming decades (Document ID 1445). MSHA acknowledges that 
reducing respirable crystalline silica concentrations to 25 [mu]g/m\3\ 
would further reduce morbidity and mortality amongst miners. However, 
MSHA determined that a PEL of 25 [mu]g/m\3\ would not be achievable for 
all mines.
    Also, upon reviewing these results, many commenters, including the 
ACLC, the American Thoracic Society, the American Lung Association, and 
the American College of Chest Physicians (hereafter referred to as 
``The American Thoracic Society et al.''), Appalachian Voices, USW, and 
the AOEC discussed how silica-related diseases are becoming more 
prevalent and/or severe in miners (Document ID 1445; 1421; 1425; 1447; 
1373; 1391; 1439; 1372; 1353; 1375). They expressed concern that 
recently there has been an increase in cases of black lung disease, 
pneumoconiosis, and other related illnesses. The American Thoracic 
Society et al. stated that the increase in the number of cases is due 
to increasing silica exposures in mining processes, citing studies 
supporting this point (Cohen et al., 2016, 2022) (Document ID 1421). 
Appalachian Voices added that research has found that black lung 
disease is occurring at its highest level in decades, is affecting more 
younger miners now than in the past, and is more frequently presenting 
in its more severe form, PMF (Document ID 1425). The ACLC echoed this 
point, stating that, in the 1990s, the worst forms of black lung 
disease (i.e., PMF) had almost been eradicated in the United States 
(Document ID 1445). This commenter expressed concern that the 
prevalence of black lung disease has grown in the past decade, and 
clinics in eastern Kentucky and southwest Virginia have diagnosed 
hundreds of cases of PMF. The commenter cited a new analysis of data 
from NIOSH and black lung clinics that, according to the commenter, 
reveals more than 4,000 cases of the most advanced form of black lung 
since 2010, as well as more than 1,500 advanced black lung diagnoses in 
just the last 5 years (Document ID 1445). The UMWA described 
surveillance findings from the National Academies of Sciences, 
Engineering, and Medicine (NASEM) that severe pneumoconiosis where 
respirable crystalline silica is likely an important contributor is 
presenting in relatively young miners, sometimes in their late 30s and 
early 40s (Document ID1398). The ACLC and UMWA expressed concern that 
the risk estimates presented in the PRA heavily underestimated the 
avoided cases because it severely underestimated current disease 
incidence (Document ID 1445; 1398).
    There are a number of reasons why current incidence of disease 
would be higher than estimates in the FRA:
     For all diseases except silicosis, the FRA does not 
present the total number of cases that are expected in the future. The 
FRA only presents the number of excess cases that miners experience due 
to their occupational exposure to respirable crystalline silica. For 
example, the FRA presents an estimated 1,794 excess ESRD deaths over 
the next 60 years under the baseline scenario among coal miners. This 
estimate would rise from 1,794 to 2,407 when including all ESRD deaths 
and not just the excess ESRD deaths attributable to respirable 
crystalline silica exposure.\22\ For silicosis and PMF, the number of 
excess cases equals the number of total cases, since MSHA assumes non-
miners have no background risk of silicosis or PMF.
     There is a lag between the time when exposure occurred and 
new diagnoses. Many of the new cases of silicosis and PMF that are 
currently being diagnosed in coal miners are for individuals who likely 
worked during a time when the coal mining industry was substantially 
larger than (e.g., roughly double) its current size. The number of 
miners who are being diagnosed today belong to larger cohorts than 
those currently entering the mining workforce. Consequently, the number 
of disease cases and deaths amongst retired miners 60 years in the 
future

[[Page 28274]]

would be expected to be lower than that amongst currently retired 
miners because the latter group is larger in size.
     Additionally, as the FRA explains, the Baseline scenario 
involves reducing all noncompliant exposures to the existing standard 
(100 [mu]g/m\3\ for MNM or 85.7 [mu]g/m\3\ for coal). This is done to 
avoid attributing benefits to this rule which should instead be 
attributed to a previous rule. Consistent with this approach, MSHA also 
has not estimated the cost to become compliant with existing standards. 
Capping noncompliant exposures at 100 [mu]g/m\3\ for MNM or 85.7 [mu]g/
m\3\ for coal increases the discrepancy between the present-day 
incidence and expected future cases under the baseline scenario. For 
coal miners, estimates of avoided cases assume that, in the absence of 
this rule, miners would be exposed to the same levels of respirable 
crystalline silica that have been observed in the coal compliance data 
from 2016 through 2021. This more recent period was selected to account 
for the fact that MSHA's 2014 RCMD Standard likely reduced 
concentrations of respirable crystalline silica. Coal miners who are 
being diagnosed with silicosis and PMF today likely suffered from 
higher exposures than those represented by more recent compliance data, 
which would lead to higher incidence of silicosis and PMF than the QRA 
projects for future miners.
     For PMF morbidity, not all cases of this disease are 
quantified in the FRA. The term ``PMF'' is used to refer to complicated 
CWP (caused by coal dust exposure) and to refer to complicated 
silicosis (caused by respirable crystalline silica exposure). The FRA 
only captures silicosis profusion 2/1+ morbidity (which may overlap 
partially with some definitions of PMF) but does not quantify benefits 
associated with reducing CWP morbidity.

F. Uncertainty Analysis

    MSHA conducted extensive uncertainty analyses to assess the impact 
on risk estimates of factors including treatment of data in excess of 
the new PEL, sampling error, and use of average rather than median 
point estimates for risk. The impact of excluding insufficient mass 
(weight) samples was also examined. As discussed below, some sources of 
uncertainty suggest that miners' risks may be lower than what MSHA 
modeled, and other sources suggest that risks may be higher. MSHA's 
estimates represent central values, which are based on the most 
reliable data and assumptions. Moreover, the overall weight-of-evidence 
indicates that increased exposures to respirable crystalline silica 
cause increased risk of mortality and morbidity, from which it follows 
that reduced exposures would lead to reduced risks.
1. Sampling Error in Exposure Data
    To quantify the impact of sampling uncertainty on the risk 
estimates, 1,000 bootstrap resamples of the original exposure data were 
generated (sampling with replacement). The resamples were stratified by 
commodity to preserve the relative sampling frequencies of coal, metal, 
non-metal, sand and gravel, crushed limestone, and stone observations 
in the original dataset. Risk calculations were repeated on each of the 
1,000 bootstrap samples, thereby generating empirical distributions for 
all risk estimates. From these empirical distributions, 95 percent 
confidence intervals were calculated. These confidence intervals 
characterize the uncertainty in the risk estimates arising from 
sampling error in the exposure data. All lifetime excess risk estimates 
had narrow confidence intervals, indicating that the estimates of 
lifetime excess morbidity and mortality risks have a high degree of 
precision.
    In regard to use of average, rather than median, point estimates of 
risk, the estimates acquired from average exposures are similar to the 
estimates from median exposures, with 95 percent confidence intervals 
having similar widths. However, the 95 percent confidence intervals are 
not always overlapping, and average exposures tended to yield higher 
estimates of reduced morbidity and mortality. Among MNM miners, MSHA 
expects the new PEL to reduce lifetime excess cases of silicosis 
morbidity by 3,394-3,703 when using average exposures to model risks 
(see FRA Table 41 of the FRA document), compared to 3,271-3,576 fewer 
cases when using median exposures to model risks (see FRA Table 37 of 
the FRA document). Among coal miners, this reduction in excess cases of 
silicosis morbidity is expected to be 328-372 when using average 
exposures (see FRA Table 42 of the FRA document), compared to 305-354 
when using median exposures (see FRA Table 38 of the FRA document). The 
new PEL is estimated to prevent 981-1,056 MNM miner deaths and 87-97 
coal miner deaths when using average exposures to model risks (see FRA 
Tables 41 and 42 of the FRA document), compared to 945-1,020 fewer MNM 
miner deaths and 80-92 fewer coal miner deaths using median exposures 
to model risks (see FRA Tables 37 and 38 of the FRA document).
2. Alternate Treatment of Exposure Samples in Excess of the New 
Exposure Limit
    To estimate excess risks and excess cases under the new PEL, MSHA 
assumed that no exposures will exceed the new limit, which effectively 
reduced any exposures exceeding 50 [mu]g/m\3\ to 50 [mu]g/m\3\. 
However, if mines implement controls with the goal of reducing 
exposures to 50 [mu]g/m\3\ on every shift, then some exposure currently 
in excess of 50 [mu]g/m\3\ will likely decrease below the new PEL. For 
this reason, the estimation method of capping all exposure data at 50 
[mu]g/m\3\ represents a ``lowball'' estimate of risk reductions due to 
the new PEL. In this section, MSHA presents estimates using an 
alternate ``highball'' method wherein exposures exceeding 50 [mu]g/m\3\ 
are set equal to the median exposure value for the 25-50 [mu]g/m\3\ 
exposure group. Because this highball method attributes larger 
reductions in exposure to the new PEL, it estimates higher lifetime 
excess risk reductions and more avoided lifetime excess cases.
    As with lifetime excess risks, the highball method also yields 
larger reductions in lifetime excess cases. Using the highball method, 
MNM miners are expected to experience 4,148 fewer cases of non-fatal 
silicosis and coal miners are expected to experience 446 fewer cases of 
non-fatal silicosis over their lifetimes. MNM miners would experience 
1,519 fewer deaths and coal miners would experience 164 fewer deaths 
over their lifetimes. Compared to the lowball method--which estimates 
that the new PEL would avoid a total of 3,746 lifetime cases of non-
fatal silicosis and 1,067 lifetime excess deaths (among both MNM and 
coal miners)--the highball method estimates totals of 4,594 avoided 
lifetime cases of non-fatal silicosis and 1,683 avoided lifetime excess 
deaths.
3. Samples With Insufficient Mass
    The MSHA Laboratory does not analyze samples for respirable 
crystalline silica that do not meet a minimum threshold for total 
respirable dust mass. The MNM exposure data gathered by enforcement 
from January 1, 2005, through December 31, 2019, contain samples that 
were analyzed using the P-2 method. As discussed, the P-2 method 
specifies that filters are only analyzed for quartz if they achieve a 
net mass (weight) gain of 0.100 mg or more. If cristobalite is 
requested, a mass gain of 0.050 mg or more is required for a filter to 
be analyzed (MSHA, 2022c). During the 15-year sample period for MNM 
exposure data, 40,618 MNM

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samples were not analyzed because the filter failed to meet the P-2 
minimum net mass gain requirements.
    Similarly, the coal exposure data gathered by enforcement from 
August 1, 2016, through July 31, 2021, contains samples that were 
analyzed using the P-7 method. For samples taken in underground mines, 
the P-7 method requires a minimum sample mass of 0.100 mg \27\ of dust 
for the sample to be analyzed for quartz. For samples taken in surface 
coal mines, the P-7 method typically requires a minimum sample mass of 
0.200 mg of dust for the sample to be analyzed for quartz. During the 
five-year sample period for coal exposure data, 32,401 valid full-shift 
coal samples were not analyzed because the P-7 method's minimum mass 
requirement was not met.
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    \27\ Often the threshold for analyzing Coal samples is >=0.1 mg. 
There are, however, some exceptions based on Sample Type and 
Occupation Code. For samples with Sample Type 4 or 8, if the 
sample's Occupation Code is not 307, 368, 382, 383, 384, or 386, 
then the threshold is >=0.2 mg.
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    MNM and Coal samples that did not meet the MSHA Laboratory's 
minimum mass criteria were excluded from the risk analysis because 
their concentrations of respirable crystalline silica are not known. 
The unanalyzed samples all had very low total respirable dust mass, 
making it unlikely that many would have exceeded the existing standards 
or the new PEL. Nonetheless, excluding these unanalyzed samples from 
the exposure datasets may introduce bias, potentially causing the 
Agency to overestimate the proportion of high-intensity exposure 
values.
    As a sensitivity analysis, MSHA used imputation techniques to 
estimate the respirable crystalline silica mass for each sample based 
on the sample weight and the median percent silica content for each 
commodity and occupation. All the unanalyzed samples with imputed 
concentrations were estimated to be <25 [micro]g/m\3\, and thus 
including these unanalyzed samples in the analysis leads to lower 
estimates of estimated lifetime excess cases for both MNM and coal 
miners.
    When including the imputed values for the unanalyzed samples, the 
new PEL would result in 2,327 fewer cases of non-fatal silicosis among 
MNM miners and 171 fewer cases among coal miners, over their lifetimes. 
The new PEL would also result in 666 fewer deaths (due to all 4 
diseases) among MNM miners and 46 fewer deaths among coal miners, over 
their lifetimes. This yields a total reduction in lifetime excess 
morbidity of 2,498 miner deaths and a total reduction in lifetime 
excess mortality of 712 miner deaths. While these estimates are lower 
than those presented in Table VI-4 (of 3,746 avoided lifetime cases of 
non-fatal silicosis and 1,067 avoided lifetime excess deaths), MSHA 
nonetheless believes that--even including these unanalyzed samples--the 
new PEL would still reduce the risk of material impairment of health or 
functional capacity in miners exposed to respirable crystalline silica. 
Moreover, the possible positive bias that may arise when excluding 
these samples would be offset by other negative biases discussed herein 
(e.g., the healthy worker survivor bias and the assumption that full 
compliance with the new PEL would not produce any reductions in 
exposure below 50 [mu]g/m\3\).
    It should be noted that the imputation method has some limitations. 
For example, the method assumes that, if the insufficient mass samples 
had been analyzed, every sample would have possessed a percentage of 
quartz, by mass, equal to the median percentage for that sample's 
associated commodity and occupation. (See Section 17.1 of the 
standalone FRA document for a full discussion of the imputation 
method.) However, within a given occupation, this percentage varies 
substantially and is positively correlated with exposure concentration. 
Suppressing the variation in this percentage quartz, by mass, produces 
less variation in the resulting imputed concentrations. Consequently, 
the imputation method may underestimate the number of unanalyzed 
samples that would truly exceed 50 [mu]g/m\3\.

VII. Feasibility

A. Technological Feasibility

    This section, technological feasibility, presents MSHA's 
conclusions on the technological feasibility of the final rule for mine 
operators. The section considers whether currently available 
technologies, used alone or in combination with each other, can be used 
by mine operators to comply with the final rule and notes and responds 
to public comments received regarding technological feasibility. In the 
proposed rule, MSHA preliminarily determined that it is technologically 
feasible for mine operators to achieve the proposed requirements. In 
the proposal, MSHA requested public comments on these preliminary 
conclusions and any other aspects of the proposed rule. After receiving 
public comments, the Agency has reviewed them and has determined that 
it is technologically feasible for mine operators to conduct air 
sampling and analysis and to achieve the final rule's PEL using 
commercially available samplers. MSHA has also determined that these 
technologically feasible samplers are widely available, and a number of 
commercial laboratories provide the service of analyzing dust 
containing respirable crystalline silica. In addition, MSHA has 
determined that technologically feasible engineering controls are 
readily available, can control crystalline silica-containing dust 
particles at the source, provide reliable and consistent protection to 
all miners who would otherwise be exposed to respirable dust, can be 
monitored, and are achievable. MSHA has also determined that 
administrative controls, used to supplement engineering controls, can 
further reduce and maintain exposures at or below the final rule's PEL. 
Moreover, MSHA has determined the final rule's respiratory protection 
practices for respirator use are technologically feasible for mine 
operators to implement. For MNM operators, MSHA has determined that the 
final rule's medical surveillance requirements are technologically 
feasible. This section focuses on technological feasibility; public 
comments specifically related to technological feasibility are 
addressed here, other comments are addressed in Section VIII.B. 
Section-by-Section Analysis of this preamble.
    MSHA is required to set standards to assure, based on the best 
available evidence, that no miner will suffer material impairment of 
health or functional capacity from exposure to toxic materials or 
harmful physical agents over his working life. 30 U.S.C. 811(a)(6)(A). 
The Mine Act also instructs MSHA to set health standards to attain 
``the highest degree of health and safety protection for the miner'' 
while considering ``the latest available scientific data in the field, 
the feasibility of the standards, and experience gained under this and 
other health and safety laws.'' 30 U.S.C. 811(a)(6)(A). But the health 
and safety of the miner is always the paramount consideration: ``[T]he 
Mine Act evinces a clear bias in favor of miner health and safety,'' 
and ``[t]he duty to use the best evidence and to consider feasibility 
are appropriately viewed through this lens and cannot be wielded as 
counterweight to MSHA's overarching role to protect the life and health 
of workers in the mining industry.'' Nat'l Min. Ass'n v. Sec'y, U.S. 
Dep't of Lab., 812 F.3d 843, 866 (11th Cir. 2016); 30 U.S.C. 801(a).
    The D.C. Circuit clarified the Agency's obligation to demonstrate 
the technological feasibility of reducing occupational exposure to a 
hazardous substance. MSHA ``must only

[[Page 28276]]

demonstrate a `reasonable possibility' that a `typical firm' can meet 
the permissible exposure limits in `most of its operations.'' Kennecott 
Greens Creek Min. Co. v. Mine Safety & Health Admin., 476 F.3d 946, 958 
(D.C. Cir. 2007) (quoting American Iron & Steel Inst. v. OSHA, 939 F.2d 
975, 980 (D.C. Cir. 1991)). Additionally, MSHA has authority to 
promulgate technology-forcing rules. ``When a statute is technology-
forcing, the agency `can impose a standard which only the most 
technologically advanced plants in an industry have been able to 
achieve--even if only in some of their operations some of the time.' '' 
Id. at 957 (quoting United Steelworkers of Am. v. Marshall, 647 F.2d 
1189, 1264 (D.C. Cir. 1980)).
    This section presents technological feasibility findings that 
guided MSHA's selection of the final rule's requirements, including the 
PEL. MSHA's technological feasibility findings are organized into two 
main sections covering: (1) the technological feasibility of part 60: 
PEL and action level; engineering and administrative controls; sampling 
provisions, including methods of sampling, and sampler and sample 
analysis requirements; and medical surveillance requirements for MNM 
mines; and (2) the technological feasibility of the revision to 
previous respiratory protection standards. Based on the analyses 
presented in the two sections, MSHA concludes that the Agency's final 
rule is technologically feasible. MSHA's feasibility determinations in 
this rulemaking are supported by its findings that the majority of the 
industry is already using technology that will allow it to effectively 
comply with the final rule.
    As noted above, MSHA has determined that part 60 is technologically 
feasible. Many mine operators already maintain respirable crystalline 
silica exposures at or below the final rule's PEL of 50 [micro]g/m\3\, 
and at mines where there are elevated exposures, operators are able to 
reduce exposures to at or below the PEL by properly maintaining 
existing engineering controls and/or by implementing new engineering 
and administrative controls that are currently available. In addition, 
mine operators can satisfy the exposure monitoring requirements of part 
60 with existing, validated, and widely used sampling technologies and 
analytical methods.
    Second, the analysis shows that the final rule's update to MSHA's 
prior respiratory protection requirements is also technologically 
feasible. The mining industry's existing respiratory protection 
practices for selecting, fitting, using, and maintaining respiratory 
protection include program elements that are similar to those of ASTM 
F3387-19, ``Standard Practice for Respiratory Protection'', which MSHA 
is incorporating by reference. Existing respiratory protection programs 
must be in writing and developed by a person with relevant experience 
and capabilities.
1. Technological Feasibility of the PEL
a. Methodology
    The technological feasibility analysis for the PEL relies primarily 
on information from three key sources:
     MSHA's Standardized Information System (MSIS) respirable 
crystalline silica exposure data, which includes 57,769 MNM and 63,127 
coal mine compliance samples collected by MSHA inspectors; these 
samples were of sufficient mass gain to be analyzed for respirable 
crystalline silica by MSHA's analytical laboratory.\28\
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    \28\ These respirable crystalline silica exposure data consist 
of 15 years of MNM mine samples (January 1, 2005, through December 
31, 2019) and five years of coal mine samples (August 1, 2016, 
through July 31, 2021). These MSHA compliance samples represent the 
conditions identified by MSHA inspectors as having the greatest 
potential for respirable crystalline silica exposure during the 
periodic inspection when sampling occurred. While MSHA's laboratory 
also analyzes mine operators' respirable coal mine dust samples 
containing respirable crystalline silica, those samples are not 
included in the data used for this analysis.
---------------------------------------------------------------------------

     The NIOSH series on reducing respirable dust in mines, 
including: ``Dust Control Handbook for Industrial Minerals Mining and 
Processing, Second Edition'' (NIOSH, 2019b) and ``Best Practices for 
Dust Control in Coal Mining, Second Edition'' (NIOSH, 2021a).\29\ With 
cooperation from the MNM and coal mining industries, NIOSH has 
extensively researched and documented engineering and administrative 
controls for respirable crystalline silica in mines.
---------------------------------------------------------------------------

    \29\ Together, these two recent reports provide more than 500 
pages of detailed descriptions, discussion, and illustrations of 
dust control technologies currently used in mines.
---------------------------------------------------------------------------

     MSHA's knowledge of the mining industry. MSHA has over 
four decades of experience inspecting surface mines at least twice per 
year and underground mines at least four times per year and in 
assisting mine operators and miners with technological issues, such as 
control of respirable dust (including respirable crystalline silica) 
exposure. MSHA provides compliance assistance, including informational 
programs, training, publications, onsite evaluations, and 
investigations that document conditions in mines and help mines operate 
in a safe and healthy manner.\30\
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    \30\ MSHA also analyzes RCMD samples collected by mine 
operators, including those containing respirable crystalline silica, 
in addition to the compliance samples collected by MSHA inspectors 
(mentioned in the first bullet of this series).
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    Additionally, MSHA consulted other published reports, scientific 
journal articles, and information from equipment manufacturers and 
mining industry suppliers.\31\
---------------------------------------------------------------------------

    \31\ Project personnel reviewed 104,365 samples collected and 
analyzed by MSHA for respirable crystalline silica, plus another 
103,745 samples collected but not analyzed due to insufficient 
respirable dust collected in the sample. They examined over 200 
published reports, proceedings, case studies, analytical methods, 
and journal articles, in addition to inspecting more than 200 web 
page, product brochures, user manuals, service/maintenance manuals 
and descriptive literature for dust control products, mining 
equipment, and related services.
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    MSHA did not identify any comments specific to the technological 
feasibility analysis methodology. This final rule retains the 
methodology supporting the technological feasibility analysis of the 
PEL in the proposed rule.
b. The Technological Feasibility Analysis Process
Mining Commodity Categories and Activity Groups
    As described in the Preliminary Regulatory Impact Analysis (PRIA), 
MSHA categorized mine types into six MNM ``commodity categories'' 
(using the method of Watts et al., 2012) based on similarities in 
exposure characteristics. MNM mine categories include metal, nonmetal, 
stone, crushed limestone, and sand and gravel. All coal mines are 
categorized together as one commodity category.
    Within each commodity, MSHA further separated mining operations 
into the four activity groups widely used by the industry: (1) 
development and production miners (drillers, stone cutters); (2) ore/
mineral processing miners (crushing/screening equipment operators and 
kiln, mill, and concentrator workers in mine facilities); (3) miners 
engaged in load/haul/dump activities (conveyor, loader, and large 
haulage vehicle operators, such as dump truck drivers); and (4) miners 
in all other occupations (mobile and utility workers, such as 
surveyors, mechanics, cleanup crews, laborers, and operators of compact 
tractors and utility trucks).
    Before determining the feasibility of reducing miners' exposure to 
respirable crystalline silica, MSHA gathered and analyzed information 
to understand current miner exposures by creating an ``exposure 
profile,'' identified the existing (i.e., baseline) conditions and the 
exposure levels associated with

[[Page 28277]]

those conditions, and determined whether mines will need additional 
control methods, and if so, whether those methods were available. 
MSHA's exposure datasets for MNM and coal mining industries are 
available as part of the rulemaking record under Docket ID MSHA-2023-
0001-1290.
Exposure Profiles
    MSHA classified all valid respirable crystalline silica samples in 
the Agency's MSIS data,\32\ grouping the data by commodity category, 
followed by activity group.\33\ MSHA created an exposure profile to 
better examine the sample data for each commodity category. These 
profiles include basic summary statistics, such as sample count, mean, 
median, and maximum values, presented as ISO 8-hour TWA values. They 
also show the sample distribution within the following exposure ranges: 
<=25 [micro]g/m\3\, >25 [micro]g/m\3\ to <=50 [micro]g/m\3\, >50 
[micro]g/m\3\ to <=100 [micro]g/m\3\ (equivalent to 85.7 [micro]g/m\3\ 
in coal mines for a sample calculated as an 8-hour TWA), >100 [micro]g/
m\3\ to <=250 [micro]g/m\3\, >250 [micro]g/m\3\ to <=500 [micro]g/m\3\, 
and >500 [micro]g/m\3\.\34\
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    \32\ MSHA removed duplicate samples, samples missing critical 
information, and those identified as invalid by the mine inspector, 
for example because of a ``fault'' (failure) of the air sampling 
pump during the sampling period.
    \33\ MSHA MSIS respirable crystalline silica data for the MNM 
industry, January 1, 2005, through December 31, 2019 (version 
20220812); MSHA MSIS respirable crystalline silica data for the Coal 
Industry, August 1, 2016, through July 31, 2021 (version 20220617). 
All samples were collected by mine inspectors and were of sufficient 
mass to be analyzed for respirable crystalline silica by MSHA's 
laboratory.
    \34\ MSHA selected these ranges based on the PELs under 
consideration, then multiples of 100 [micro]g/m\3\ to show how data 
are distributed in the higher ranges. Table VII-4 also presents 
additional exposure ranges corresponding to the 85.7 [micro]g/m\3\ 
concentration for coal samples.
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    In Table VII-1, the respirable crystalline silica exposure data for 
MNM miners are summarized by commodity and for the MNM industry as a 
whole, while Table VII-2 presents the exposure profile as the 
percentage of samples in each exposure range. Overall, approximately 82 
percent of the 57,769 MNM compliance samples were at or below the PEL 
(50 [micro]g/m\3\). The exposure profile shows variability between the 
commodity categories: approximately 73 percent of metal miner exposures 
at or below the PEL (50 [micro]g/m\3\) (the lowest among all MNM 
mines), compared with approximately 90 percent of the crushed limestone 
miner exposures (the highest among all MNM mines).
    Table VII-3 and Table VII-4 present the corresponding respirable 
crystalline silica exposure information for coal miners by location 
(underground or surface). Overall, approximately 93 percent of the 
63,127 samples obtained by MSHA inspectors for coal miners were at or 
below the PEL (50 [micro]g/m\3\). There was little variation between 
samples for underground miners and surface miners (with approximately 
93 and 92 percent of the samples at or below 50 [micro]g/m\3\, 
respectively). Exposure values from the coal industry are expressed as 
ISO 8-hour TWAs, compatible with the final rule's (see notes, Table 
VII-3).
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[GRAPHIC] [TIFF OMITTED] TR18AP24.147


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[GRAPHIC] [TIFF OMITTED] TR18AP24.082


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[GRAPHIC] [TIFF OMITTED] TR18AP24.148

Existing Dust Controls in Mines (Baseline Conditions)
    MNM and coal mines are controlling dust containing respirable 
crystalline silica in various ways. As shown in Tables VII-1 through 
VII-4, respirable crystalline silica exposures exceeded the PEL of 50 
[micro]g/m\3\ in about 18 percent of all MNM samples collected. About 
seven percent of all coal samples exceeded the PEL. Overall, metal 
mines and sand and gravel mines had higher exposure levels than other 
commodity mines.
    Despite the extensive dust control methods available, dust control 
measures have been implemented in some commodity categories to a 
greater degree than in others. This is partly because some commodity 
categories tend to have larger mines. MSHA has found that the larger 
the amount (tonnage) of material a mine moves (including overburden and 
other waste rock), the faster the mine tends to operate its equipment 
(i.e., closer to the equipment capacity), creating more air turbulence 
and therefore generating more airborne respirable crystalline silica. 
The amount of material moved also influences the number of miners 
employed at a mine, and therefore, the number of miners can be 
indirectly correlated to the amount of dust generated. MSHA has 
observed that in large mines, dusty conditions typically prompt more 
control efforts, usually in the form of added engineering controls.
    MSHA has also found that metal mines, which are typically large 
operations with higher numbers of miners, tend to have available 
engineering controls for dust management. On the other hand, sand and 
gravel mines, which generally employ fewer miners and handle modest 
amounts of material, have very limited, if any, dust control measures. 
This is because most of the mined material is a commodity that only 
requires washing and screening into various sizes of product 
stockpiles, generating little waste material. Nonmetal, stone, and 
crushed limestone mines occupy the middle range in terms of employment, 
existing engineering controls, and maintenance practices.
    Over the years, staff from multiple MSHA program areas have worked 
alongside miners and mine operators to improve safety and health by 
inspecting, evaluating, and researching mine conditions, equipment, and 
operations. These key programs, each of which has an onsite presence, 
include (but are not limited to) Mine Safety and Health Enforcement; 
Directorate of Educational Policy and Development, which includes the 
National Mine Health and Safety Academy and the Educational Field and 
Small Mine Services; and the Directorate of Technical Support, which 
comprises the Approval and Certification Center and the Pittsburgh 
Safety and Health Technology Center (including its Health Field 
Division, Analytical and Laboratory Services Division, National Air and 
Dust Laboratory, Ventilation Division, and other specialized 
divisions). Table VII-5 reflects the collective observations of these 
MSHA programs, presented in terms of existing dust control (baseline 
conditions) and the classes of additional control measures that will 
provide those mines with the greatest benefit to reduce exposures below 
the PEL and action level.
    Table VII-5 shows MSHA's assessment of existing dust controls in 
mines (baseline conditions) and additional controls needed to meet the 
PEL for each commodity category, including the need for frequent 
scheduled maintenance. By conducting frequent scheduled maintenance, 
mine operators can reduce the concentration of respirable crystalline 
silica. Table VII-5 shows that metal mines have adopted extensive dust 
controls, while sand and gravel mines tend to have minimal engineering 
controls, if any.

[[Page 28282]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.149

BILLING CODE 4520-43-C
    Based on MSHA's experience, NIOSH research, and effective 
respirable dust controls currently available and in use in the mining 
industry, MSHA finds that the baseline conditions include various 
combinations of existing engineering controls selected and installed by 
individual mines to address respirable crystalline silica generated 
during mining operations.
Respirable Crystalline Silica Exposure Controls Available to Mines
    Under the final rule, the mine operator must install, use, and 
maintain engineering controls, supplemented by administrative controls, 
when necessary, to keep each miner's exposure at or below the PEL. 
Engineering controls reduce or prevent miners' exposure to hazards.\35\ 
Administrative controls establish work practices that reduce the 
duration, frequency, or intensity of miners' exposures (under the final 
rule, the rotation of miners is not considered an acceptable 
administrative control to comply with the PEL).
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    \35\ Control measures that reduce respirable crystalline silica 
can also reduce exposures to other hazardous particulates, such as 
RCMD, metals, asbestos, and diesel exhaust. Operator enclosures and 
process enclosures also reduce hazardous levels of noise by creating 
a barrier between the operator and the noise source.
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    MSHA data and experience show that mine operators already have 
numerous engineering and administrative control options to control 
miners' exposures to respirable crystalline silica. These control 
options are widely recognized and used throughout the mining industry. 
NIOSH has extensively researched and documented engineering and 
administrative controls for respirable crystalline silica in mines. As 
noted previously, NIOSH has published a series on reducing respirable 
dust in mines (NIOSH, 2019b, 2021a).
(1) Engineering Controls
    Examples of existing engineering controls used at mines and 
commercially available engineering controls that MSHA considered 
include:
     Wetting or water sprays that prevent, capture, or redirect 
dust;
     Ventilation systems that capture dust at its source and 
transport it to a dust collection device (e.g., filter or bag house), 
dilute dust already in the air, or ``scrub'' (cleanse) dust from the 
air in the work area;
     Process enclosures that restrict dust from migrating 
outside of the enclosed area, sometimes used with an attached 
ventilation system to improve effectiveness (e.g., crushing equipment 
and associated dump hopper enclosure, with curtains and mechanical 
ventilation to keep dust inside);

[[Page 28283]]

     Operator enclosures, such as mobile equipment cabs or 
control booths, which provide an environment with clean air for an 
equipment operator to work safely;
     Protective features on mining process equipment to help 
prevent process failures and associated dust releases (e.g., 
skirtboards on conveyors, which protect the conveyor system from damage 
and prevent material on the conveyor from falling off, which generates 
airborne dust);
     Preventive maintenance conducted on engineering controls 
and mining equipment that can influence dust levels at a mine, to keep 
them functioning optimally; and
     Instrumentation and other equipment to assist mine 
operators and miners in evaluating engineering control effectiveness 
and recognizing control failures or other conditions that need 
corrective action.\36\
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    \36\ These instruments include dust monitors; water, air, and 
differential air pressure gauges; pitot tubes and air velocity 
meters; and video camera (NIOSH recommends software that pairs video 
with a dust monitor to track conditions that could lead to elevated 
exposures if not corrected). These instruments are discussed in 
NIOSH's best practices guides and dust control handbooks.
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(2) Administrative Controls
    Administrative controls include practices that change the way tasks 
are performed to reduce a miner's exposure. Administrative controls can 
be very effective and can even prevent exposure entirely. MSHA has 
determined that various administrative controls are readily available 
to provide supplementary support to engineering controls. Examples of 
administrative controls include housekeeping procedures; proper work 
positions of miners; walking around the outside of a dusty process area 
rather than walking through it; cleaning of spills; and measures to 
prevent or minimize contamination of clothing to help decrease miners' 
exposure to respirable crystalline silica. However, these control 
methods depend on human behavior and intervention and are less reliable 
than properly designed, installed, and maintained engineering controls. 
Therefore, administrative controls will be permitted only as 
supplementary measures, with engineering controls required as the 
primary means of protection. Nevertheless, administrative controls play 
an important role in reducing miners' exposure to respirable 
crystalline silica.\37\
---------------------------------------------------------------------------

    \37\ Paragraph 60.11(b) prohibits the use of rotation of miners 
as an administrative control used for compliance with this part.
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(3) Combinations of Controls
    Various control options can also be used in combinations. NIOSH has 
documented in detail most control methods and has confirmed that they 
are currently used in mines, both individually and in combination with 
each other (2019b, 2021a).
Maintenance
    MSHA finds that a strong preventive maintenance program plays an 
important role in achieving consistently lower respirable crystalline 
silica exposure levels. MSHA has observed that when engineering 
controls are installed and maintained in working condition, respirable 
dust exposures tend to be below the existing exposure limits. When 
engineering controls are not maintained, dust control efficiency 
declines and exposure levels rise. When engineering controls fail due 
to a lack of proper maintenance, a marked rise in exposures can occur, 
resulting in noncompliance with MSHA's existing exposure limits. Some 
examples of the impact that proper maintenance can have on respirable 
dust levels include:
     Water spray maintenance: An experiment using water spray 
bars that could be turned on or off showed that dust reduction was less 
effective each time additional spray nozzles were deactivated. A 10 
percent decrease occurred when three of 21 sprays were shut off, but a 
50 percent decrease occurred when 12 out of the 21 sprays were shut 
off. Decreased total water spray volume and gaps in the spray pattern 
(due to deactivated nozzles) were both partially responsible for the 
decreased dust control (Seaman et al., 2020).
     Water added to drill bailing air: When introduced into the 
drill hole (with the bailing air through a hollow drill bit), water 
mixes with and moistens the drill dust ejected from the hole and can 
reduce respirable dust by more than 90% (NIOSH, 2019b, 2021a). NIOSH 
reports that this same control measure, and others, are similarly 
effective for MNM and surface coal mine drills preparing the blasting 
holes used to expose the material below (whether ore or coal).
     Ventilation system maintenance: The amount of air cleaned 
by an air scrubber is decreased by up to one-third (33 percent) after 
one continuous mining machine cut. Cleaning the scrubber screens 
restores scrubber efficacy, but this maintenance must be performed 
after every cut. Spare scrubber screens make frequent cleaning 
practical without slowing production (NIOSH, 2021a).
     Operator enclosure maintenance: Tests with mining 
equipment showed that maintenance activities such as repairing weather 
stripping and replacing clogged and missing cab ventilation system 
filters (intake, recirculation, final filters) increased miner 
protection by up to 95 percent (NIOSH, 2019b, 2021a).
     Filter selection during maintenance: Airflow is as 
important as filtration and pressurization in operator enclosures; 
during maintenance, filter selection can influence all three factors. 
Performing serial end-shift testing of enclosed cabs (on a face drill 
and a roof/rock bolter) at an underground crushed limestone mine, NIOSH 
compared installed HEPA filters and an alternative (MERV 16 filters). 
The latter provided an equal level of filtration and better overall 
miner protection by allowing greater airflow and cab pressurization. As 
an added advantage, NIOSH showed that these filters cost less and 
required less-frequent replacement, reducing maintenance expenses in 
this mining environment (Cecala et al., 2016; NIOSH, 2019b, 
2021a).38 39
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    \38\ NIOSH believes this study, like many of its other mining 
studies on operator enclosures and surface drill dust controls, is 
relevant to both MNM mining and coal mining. NIOSH reports on this 
study, conducted at an underground limestone mine, in detail in both 
its Dust Control Handbook for Industrial Minerals Mining and 
Processing (second edition) (2019b) and its Best Practices for Dust 
Control in Coal Mining (second edition) (2021a).
    \39\ Acronyms: High efficiency particulate air (HEPA). Minimum 
efficiency reporting value (MERV).
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     Proper design and installation--foundation for effective 
maintenance: A new replacement equipment operator enclosure (control 
booth) installed adjacent to the primary crusher at a granite stone 
quarry initially provided 50 to 96 percent respirable dust reduction, 
even with inadequate pressurization. The protection it offered miners 
tripled after the booth's second pressurization/filtration unit was 
activated (Organiscak et al., 2016).
    MSHA has observed that when engineering controls are properly 
maintained, exposure levels decrease or stay low. Metal mines, which 
typically have substantial controls already installed, primarily need 
reliable preventive maintenance programs to achieve the PEL. It is also 
important to repair equipment damage that contributes to dust exposure 
(for example, damage to conveyor skirtboards that protect the conveyor 
system from damage and prevent spillage which generates airborne dust). 
Maintenance and repair programs must

[[Page 28284]]

ensure that dust control equipment is functioning properly.
    Some commenters described conditions where they found engineering 
controls were not feasible. The NSSGA, the NVMA, and US Silica (a MNM 
mine operator) cited examples such as water sprays that freeze in 
winter or are not practical where the product must be kept dry so mine 
workers can bag it; and enclosures and ventilation systems that are 
sometimes impractical for portable operations at some locations and 
limited (so made less effective) by the physical constraints of others 
(Document ID 1448; 1441;1455). The MNM mine operator commenter 
indicated that at their worksite, these physical conditions cause 
engineering controls to be ineffective more than does lack of effort 
(Document ID 1455).
    In MSHA's considerable experience providing technical support to 
mines, there is always a way to eliminate overexposures to respirable 
dust (including respirable crystalline silica) by using the information 
contained in NIOSH best practice guides for mines. MSHA has found that 
the number of control options and level of detail in the guides make 
compliance achievable through engineering controls alone. By adding 
administrative controls (or procedural practices) mines routinely 
achieve consistent compliance. MSHA agrees with commenters that exposed 
water sprays are not effective in freezing weather, however, the Agency 
has found that one or more other options is available for every 
circumstance. For example, enclosing the process equipment is one 
alternative to using water sprays for dust control. Rather than 
suppressing dust, as water spray does, enclosing the dusty process 
equipment limits the amount of dust that escapes from the process 
enclosure, in turn limiting the amount of dust in the equipment 
operator's breathing zone. A process equipment enclosure can be 
constructed with baffles to help calm the air inside the enclosure, so 
dust settles more quickly inside the enclosure. As another option, a 
ventilation dust collection system can be paired with a process 
equipment enclosure to make both even more effective. Yet another 
example is to enclose the equipment operators (e.g., in a booth or 
mobile cab). Furthermore, MSHA observes that a number of surface mines 
operate intermittently; many of them are closed in seasons with harsh 
weather. Typically, those mines can use water sprays effectively when 
they are operating. MSHA notes that ventilation systems are effective 
in every season; a large variety of system components and designs 
provide a ventilation system that can be constructed for almost every 
situation. As noted in the proposed rule, some mines might need to work 
harder than others (layering different engineering controls and adding 
administrative controls) to achieve compliance.
    The Brick Industry Association (BIA) noted that their industry 
usually operates with the minimum number of personnel even under 
optimal staffing conditions and explained that it can be difficult to 
avoid rotating workers to achieve efficient workflow (Document ID 
1422). This commenter also stated that it could be difficult to 
maintain productive operations if management is not able to either 
rotate workers to minimize exposure levels or allow personnel to wear 
respirators for day-to-day tasks.
    As MSHA stated in the proposed rule and, and included in this final 
rule, miner rotation is not considered an acceptable administrative 
control for minimizing miner exposure levels or complying with any 
provision of part 60. MSHA understands that mine operators may assign a 
variety of work tasks for business reasons unrelated to compliance with 
the PEL. However, MSHA will not consider as compliance a mine 
operator's implementation of a varied task schedule for particular 
miners for purposes of avoiding conflict with the PEL, as engineering 
and administrative controls can feasibly reduce exposure levels below 
the PEL.
    This final rule prioritizes engineering controls for reducing miner 
exposures, because they (1) control crystalline silica-containing dust 
particles at the source; (2) provide reliable, predictable, effective, 
and consistent protection to miners who would otherwise be exposed to 
dust from that source; and (3) can be monitored. MSHA maintains that as 
described earlier in this section, a combination of engineering 
controls and administrative controls can reduce miner exposures to 
levels below the PEL and that equipment maintenance will help minimize 
exposures. Some examples of engineering controls include wet dust 
suppression methods; enclosure; ventilation--permanent or portable 
trunks; pre-cleaning--by washing or HEPA vacuuming; and controlling 
dust sources. Examples of administrative controls include proper miner 
positioning and improved housekeeping. For a detailed discussion on 
rotation of miners, see Section VIII.B.4. Section 60.11--Methods of 
Compliance.
    MSHA finds that the technological feasibility analysis process was 
effective and controlling exposure levels to the PEL or lower using 
engineering controls is both feasible and practical. The final rule, as 
did the proposed rule, emphasizes engineering controls, supplemented 
with administrative controls, to control miner exposure.
c. Feasibility Determination of Control Technologies
    MSHA's final PEL is 50 [mu]g/m\3\ for MNM and coal mines. As NIOSH 
(2019b, 2021a) has documented, the mining industry has a wide range of 
options for controlling dust exposure that are already in various 
configurations in mines. NIOSH has carefully evaluated most of the dust 
controls used in the mining industry and found that many of the 
controls may be used in combination with other control options. NIOSH 
has documented protective factors and exposure reductions of 30 to 90 
percent or higher for many engineering and administrative controls.
    Effective maintenance will also help mine operators comply with the 
final rule. MSHA finds that maintaining (including adjusting) or 
repairing existing equipment will help achieve exposures at or below 50 
[mu]g/m\3\. For example, NIOSH (2019b) found that performing 
maintenance on an operator enclosure can restore enclosure 
pressurization and reduce the respirable dust exposure of a miner by 90 
to 98.9 percent (e.g., by maintaining weather stripping, reseating or 
replacing leaking or clogged filters, and upgrading filtration). When 
an equipment operator remains inside a well-maintained enclosure for a 
portion of a shift (for example 75 percent of an 8-hour shift), the cab 
can reduce the exposure of the equipment operator proportionally, to a 
level of 50 [mu]g/m\3\ (or lower). This point is demonstrated by the 
following example involving a bulk loading equipment operator in a 
poorly maintained booth, exposed to respirable crystalline silica near 
the existing exposure limit (in the MNM sectors, 100 [mu]g/m\3\, as ISO 
8-hour TWA value; in the coal sector, 85.7 [mu]g/m\3\ ISO, calculated 
as an 8-hour TWA). During the 25 percent of their shift (two hours of 
an eight-hour shift) that the miner works in the poorly maintained 
enclosure, their exposure will be 100 [mu]g/m\3\, while for the other 
six hours (operating mobile equipment with a fully refurbished 
protective cab), the exposure level will be 90 percent lower, or 10 
[mu]g/m\3\, resulting in an 8-hour TWA exposure of 33 [mu]g/m\3\ for 
that miner's shift.\40\ Greater

[[Page 28285]]

exposure reductions could also be achieved by repairing or replacing 
the poorly maintained enclosure, or modifying the miner's schedule so 
that the miner works seven hours, rather than six, inside the well-
maintained enclosure.
---------------------------------------------------------------------------

    \40\ Calculating the exposure for the shift: 8-hour TWA = [(10 
[mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x 2 hours)]/8 hours = 33 
[mu]g/m\3\.
---------------------------------------------------------------------------

    Other engineering controls (e.g., process enclosure, water dust 
suppression, dust suppression hopper, ventilation systems) could reduce 
dust concentrations in the area surrounding the poorly maintained 
enclosure, which reduces the exposure of the equipment operator inside. 
As a hypothetical example, if the poorly maintained enclosure was an 
open-air control booth (windows do not close) at a truck loading 
station, adding a dust suppression hopper (which reduces respirable 
dust exposure by 39 to 88 percent during bulk loading) (NIOSH, 2019b), 
will lead to lower exposure during the two hours the miner is inside 
the open-air booth. The calculated respirable crystalline silica 8-hour 
TWA exposure of that miner could be reduced from 33 [mu]g/m\3\ (with 
improved equipment operator enclosure alone) to 23 [mu]g/m\3\ (improved 
equipment operator enclosure plus dust suppression hopper).\41\ As an 
added benefit, any helper or utility worker in the truck loading area 
will also experience reduced exposure.
---------------------------------------------------------------------------

    \41\ Calculating the exposure with both the well-maintained 
operator enclosure (6 hours) and dust suppression hopper, assuming 
only the minimum documented respirable dust concentration reduction 
(39 percent): [(10 [mu]g/m\3\ x 6 hours) + (100 [mu]g/m\3\ x (1-
0.39) x 2 hours)]/8 hours = 23 [mu]g/m\3\.
---------------------------------------------------------------------------

    A similar hypothetical example is a coal miner helper who spends 90 
minutes (1.5 hours) per 8-hour shift assisting a drilling rig operator 
(in a protective operator's cab) drilling blast holes. The combination 
of controls used to control drilling dust (including water added to the 
bailing air, which can reduce airborne respirable dust emissions by up 
to 96 percent) can keep the helper's respirable crystalline silica 
exposure in the range of 35 [mu]g/m\3\ (ISO) as an 8-hour TWA. If, 
however, the drill's on-board water tank runs dry due to poor 
maintenance, the respirable crystalline silica concentration near the 
drill will rise by 95 percent, meaning that the concentration is 20 
times greater than the usual level (NIOSH, 2021a). If the drill 
operator idles the drill and calls for water resupply, the helper will 
not experience an elevated exposure. The hypothetical helper's exposure 
level rises higher the longer the drill is operated. If the drill is 
operated dry for another 30 minutes until water resupply arrives, the 
helper will experience a respirable crystalline silica exposure of 77 
[mu]g/m\3\ (ISO) as an 8-hour TWA. If dry drilling continued for 1.5 
hours, the helper would have an exposure of 160 [mu]g/m\3\ ISO as an 8-
hour TWA.\42\ After water is delivered, drill respirable dust emissions 
will return to their normal level once water is again introduced into 
the drill bailing air.
---------------------------------------------------------------------------

    \42\ The 8-hour TWA exposure level of the helper, including the 
30-minute period of elevated exposure, is calculated as: [(35 [mu]g/
m\3\ x 7.5 hours) + (35 [mu]g/m\3\ x 20 x 0.5 hours)]/8 hours = 77 
[mu]g/m\3\. Drill bits designed for use with water may need to be 
replaced sooner if used dry.
---------------------------------------------------------------------------

    Based on these examples and the wide range of effective exposure 
control options available to the mining industry, MSHA finds that 
control technologies capable of reducing miners' respirable crystalline 
silica exposures are available, proven, effective, and transferable 
between mining commodities; however, they must be well-designed and 
consistently used and maintained. MSHA also finds that methods of 
maintaining engineering controls are known, available, and effective.
Feasibility Findings for the PEL
    Based on the exposure profiles in Table VII-1 and Table VII-2 for 
MNM mines, and in Table VII-3 and Table VII-4 for coal mines, and the 
examples in the previous section that demonstrate the beneficial effect 
of combined controls, MSHA finds that the PEL of 50 [mu]g/m\3\ is 
technologically feasible for all mines.
    Table VII-6 summarizes the technological feasibility of control 
technologies available to the mining industry, by commodity. MSHA finds 
that control technologies are technologically feasible for all six 
commodities and their respective activity groups. Under baseline 
conditions, mines in each commodity category have already achieved 
respirable crystalline silica exposures at or below 50 [mu]g/m\3\ for 
most of the miners represented by MSHA's 57,769 samples for MNM miners 
and 63,127 samples for coal miners.
BILLING CODE 4520-43-P

[[Page 28286]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.150

BILLING CODE 4520-43-C
Feasibility Findings for the Action Level
    MSHA finds that mine operators can achieve exposure levels below 
the action level of 25 [mu]g/m\3\ for most miners by implementing 
additional engineering controls and more flexible and innovative 
administrative controls, in addition to the existing control methods 
already discussed in this technological feasibility analysis. The 
exposure profiles in Tables VII-1 and VII-2 for MNM mines, and Tables 
VII-3 and VII-4 for coal mines, indicate that mine operators have 
already achieved the action level for at least half of the miners MSHA 
has sampled in each commodity category. However, to reliably maintain 
exposures below the action level for all miners, operators will need to 
upgrade equipment and facility designs, particularly in mines with 
higher respirable crystalline silica concentrations, which may be due 
to an elevated silica content in materials.
    One control option is increased automation, such as expanding the 
use of existing autonomous or remote-controlled drilling rigs, roof 
bolters, stone cutting equipment, and packaging/bagging equipment. This 
type of automation can reduce exposures by increasing the distance 
between the equipment operator and the dust source. Other options 
include completely enclosing most processes and ventilating the 
enclosures with dust extraction equipment or controlling the speed of 
mining equipment (e.g., longwall shearers, conveyors, dump truck 
emptying) and process equipment (e.g., crushers, mills) to reduce 
turbulence that increases dust concentrations in air. Additionally, 
where compatible with the material, exposure levels can be reduced by 
increased wetting to constantly maintain the material, equipment, and 
mine facility surfaces damp through added water sprays and frequent 
housekeeping (i.e., hosing down surfaces as often as necessary). In 
addition, vacuuming minimizes the amount of dust that becomes airborne 
and prevent dust that does settle on a surface from being resuspended 
in air.
    Mines that only occasionally work with higher-silica-content 
materials may not be equipped with the controls required to achieve the 
action level of 25 [mu]g/m\3\, or they may not currently have 
procedures to ensure miners are protected when they do work with these 
materials. Examples of these activities include cutting roof or floor 
rock with

[[Page 28287]]

a continuous mining machine in underground coal mines; packaging 
operations that involve materials from an unfamiliar supplier, 
including another mine; and rebuilding or repairing kilns. To address 
these activities, under the final rule, mine operators will have to add 
engineering controls to address any foreseeable respirable crystalline 
silica overexposures. Examples of additional controls include pre-
testing batches of new raw materials; improving hazard communication 
when batches of incoming raw materials contain higher concentrations of 
crystalline silica, and augmenting enclosure and ventilation (e.g., 
adding ventilation to all crushing and screening equipment, increasing 
mine facility ventilation to 30 air changes per hour, and fully 
enclosing and ventilating all conveyor transfer locations). NIOSH 
(2019b, 2021a) describes all of the dust control methods outlined in 
this section, which are already used in mines, although to a less 
rigorous extent than will be necessary to reliably and consistently 
achieve exposure levels of 25 [mu]g/m\3\ or lower for all miners.
    MSHA finds that the action level of 25 [mu]g/m\3\ is 
technologically feasible for most mines. This finding is based on the 
exposure profiles, presented in Tables VII-1 and VII-2 for MNM mines, 
and Tables VII-3 and VII-4 for coal mines, which show that within each 
commodity category, the exposure levels are at or below 25 [mu]g/m\3\ 
for at least half of the miners sampled. MSHA's finding is also based 
on the extensive control options documented by NIOSH, which can be used 
in combinations to achieve additional reductions in respirable 
crystalline silica exposure. Although most mines will need to adopt and 
rigorously implement a number of the control options mentioned in this 
section, the technology exists to achieve this level, is already in use 
in mines, and is available for most mines.
    MSHA received numerous comments related to exposure control 
methods. Several commenters recommended that the standard incorporate 
by reference certain materials to assist mine operators with 
compliance. The International Society of Environmental Enclosure 
Engineers (ISEEE) discussed ISO 23875 (Document ID 1377).\43\ The 
commenter explained that this ISO standard is a widely adopted 
international standard for cab air quality, as a practical and cost-
effective engineering control that would help mine operators meet the 
final rule's requirements since the desired outcome in all ISO 23875 
cabs is compliance with air quality regulations at the 25 [mu]g/m\3\ 
level. The commenter added that increased awareness of the standard and 
compliant cabs would lead to the development of a standardized cab 
design that could be mass-produced and therefore reduce costs. Another 
commenter, the APHA, stated that guides prepared by NIOSH for coal 
mines and metal and non-metal mines contain helpful illustrations of 
technologically feasible engineering controls that reduce exposure to 
respirable dust (Document ID 1416).
---------------------------------------------------------------------------

    \43\ ISO 23875:2021 (Mining--Air quality control systems for 
operator enclosures--Performance requirements and testing methods) 
and Amendments.
---------------------------------------------------------------------------

    MSHA has reviewed the comments and suggested material. The Agency 
agrees that ISO 23875 is a useful tool that promotes feasible dust 
control equipment manufacture and maintenance practices. Although MSHA 
has not incorporated it into the final rule, the Agency will keep this 
standard in mind during future initiatives. MSHA acknowledges that many 
other organizations and agencies, including NIOSH with its detailed and 
carefully illustrated best practice guides for the mining industries, 
have published extensive information that may be helpful to mine 
operators seeking methods to protect miners. The Agency encourages mine 
operators to use these tools to identify proper and adequate 
engineering controls, choose those that will be useful in their mines, 
and ensure that the controls are correctly installed, implemented, and 
maintained.
    MSHA received several comments regarding the description and use of 
feasible engineering controls. The NVMA requested that MSHA supply a 
definition for what is ``feasible'' (Document ID 1441).
    Within MSHA's standard development process, the term ``feasible'' 
generally means ``capable of being done.'' In the case of respirable 
crystalline silica exposure controls, these controls exist already and 
are not technology-forcing. Based on its extensive experience 
inspecting and providing compliance assistance and technical support in 
mines, MSHA has observed that U.S. mines are already using an extensive 
array of engineering controls. As documented by NIOSH in its best 
practices guides and other resources for the mining industry, the 
numerous readily available engineering controls provide evidence that 
it is technologically feasible for mine operators to reduce miner 
respirable crystalline silica exposure to levels at or below the PEL 
and, in some cases, below the action level (NIOSH, 2019b, 2021a).
    These engineering controls, including examples and data, were 
discussed in more detail previously in this Technological Feasibility 
section (see Section VII.A.1.b. The Technological Feasibility Analysis 
Process). That section explains that engineering controls reduce or 
prevent miners' exposure to hazards, while administrative controls 
establish work practices that reduce the duration, frequency, or 
intensity of miners' exposures. The different functional types of 
engineering controls (wetting or water sprays, ventilation systems, 
process enclosures, equipment operator enclosures, the associated 
preventive maintenance that keeps the control equipment operating 
effectively, and instrumentation to monitor function and identify need 
for corrective actions) work alone or in combination with the same or 
other controls to provide additional protections. To further ensure 
that mine operators can achieve the PEL under diverse mining 
conditions, the final rule allows operators who seek an added measure 
of protection for miners to supplement engineering controls with 
administrative controls (e.g., housekeeping procedures; proper work 
positions of miners; walking around the outside of a dusty process area 
rather than walking through it; cleaning of spills; and measures to 
prevent or minimize contamination of clothing to help decrease miners' 
exposure). This strategy allows a mine operator to select the set of 
engineering controls that will be most effective given the mining 
conditions and the mine environment. MSHA acknowledges that some mines 
will need to work harder than others; however, with the wide array of 
control options, MSHA is confident that the PEL is technologically 
feasible. As stated earlier with respect to a feasibility finding: 
``MSHA does not need to show that every technology can be used in every 
mine. The agency must only demonstrate a `reasonable possibility' that 
a `typical firm' can meet the permissible exposure limits in `most of 
its operations.' '' Kennecott Greens Creek Min. Co. v. Mine Safety & 
Health Admin., 476 F.3d 946, 958 (D.C. Cir. 2007) (quoting Am. Iron & 
Steel Inst. v. Occupational Safety & Health Admin., 939 F.2d 975, 980 
(D.C. Cir. 1991)).
    Some commenters, including the UMWA, American Federation of Labor 
and Congress of Industrial Organizations (AFL-CIO), Black Lung Clinics, 
and AIHA echoed the availability of effective engineering controls in 
the mining industry

[[Page 28288]]

(Document ID 1398; 1449; 1410; 1351). Two labor organizations stated 
that mine operators should already be utilizing engineering and 
administrative controls in accordance with the law and their existing 
ventilation plans (Document ID 1398; 1449). The Black Lung Clinics, 
AIHA, and UMWA expressed support for engineering and administrative 
controls as means to keep miners' exposures to respirable crystalline 
silica below the proposed PEL (Document ID 1410; 1351; 1398). Agreeing 
with MSHA that technologically feasible engineering controls are 
available, the AIHA stated that these methods can control crystalline 
silica-containing dust particles at the source and provide reliable and 
consistent protection to all miners who would otherwise be exposed to 
respirable dust (Document ID 1351).
    MSHA concurs with these comments. MSHA's experience is consistent 
with these comments. Based on MSHA's experience, consideration of the 
OSHA silica rule (2016), and documentation from NIOSH as discussed in 
this section of the preamble, MSHA determines that engineering controls 
exist for mining operations to reduce miners' exposure to the level of 
the PEL (50 [micro]g/m\3\). The Agency finds that engineering controls: 
(1) control crystalline silica-containing dust particles at the source; 
(2) provide reliable, predictable, effective, and consistent protection 
to miners who would otherwise be exposed to dust from that source; and 
(3) can be monitored. The technological feasibility analysis of the PEL 
in the proposed rule remains in effect for this final rule.
    MSHA received several comments on the technological feasibility of 
the action level (25 [micro]g/m\3\). Commenters including the Arizona 
Mining Association and American Iron Steel Institute (AISI) stated that 
the action level would not be achievable with current technology 
(Document ID 1368; 1426). The AIHA opposing the proposed action level, 
stated that the action level should be removed and the PEL should 
instead be set at the proposed action level of 25 [micro]g/m\3\ 
(Document ID 1351).
    After careful consideration of the comments, MSHA has determined a 
full-shift 8-hour TWA action level of 25 [micro]g/m\3\ is feasible, and 
the final rule is the same as the proposal. MSHA acknowledges that its 
FRA finds that there will be a greater reduction of risk for morbidity 
and mortality at the action level than the final PEL of 50 [micro]g/
m\3\.\44\ Additionally, MSHA's exposure profile (Section VII.A.1.b, 
Tables VII-1 through VII-4) indicates, based on MSHA compliance 
samples, that operators at most mines are already achieving exposure 
levels less than 25 [micro]g/m\3\ for most miners. Tables VII-1 and 
VII-3 (in this section) show that the overall median MNM miner exposure 
is 15 [micro]g/m\3\ and the overall median coal miner exposure is 16 
[micro]g/m\3\.\45\ Although these medians indicate that mine operators 
have already achieved exposure levels below 25 [micro]g/m\3\ for more 
than half of all miners sampled by MSHA, the Agency acknowledges that, 
for some mines, consistently achieving a PEL of 25 [mu]g/m\3\ for all 
the miners it employs could present a substantial challenge (i.e., a 
PEL of 25 [mu]g/m\3\ is technically feasible, but the actions required 
might not be practical for many mines).\46\ MSHA finds, however, that 
the concentration of 25 [micro]g/m\3\ is an appropriate and necessary 
action level, which most mine operators can (and may already have) 
achieve for many miners. The action level is consistent with MSHA's 
statutory purpose under the Mine Act--to provide the highest level of 
health protection for the miner. MSHA establishes the action level and 
sets a sampling frequency for concentrations above the action level to 
require mine operators to be proactive and act before miners are 
overexposed. Under the final rule, where some miners have exposures at 
or above the action level (25 [micro]g/m\3\), but not exceeding the 
PEL, mine operators are not required to install additional controls, 
but instead (in accordance with Sec.  60.12(a)(3)) must sample those 
miners quarterly to confirm exposures remain below the PEL. 
Alternatively, the mine operator may choose to take actions to further 
reduce exposures below 25 [micro]g/m\3\ and, where successful, 
discontinue sampling (after meeting the sampling requirements under 
Sec.  60.12(a)(4)).
---------------------------------------------------------------------------

    \44\ Some residual risks remain even at exposures of 25 
[micro]g/m\3\ of respirable crystalline silica. For example, at 25 
[micro]g/m\3\, end stage renal disease (ESRD) risk is 20.7 per 1,000 
MNM miners and 21.6 per 1,000 coal miners.
    \45\ The median exposure level is the midpoint concentration of 
all samples; in other words, half (50%) of all the miner exposure 
samples are below the median, and the remaining half are above. 
Tables VII-2 (MNM mines) and VII-4 (coal mines) show the percent of 
MSHA compliance exposure samples that are less than 25 [micro]g/
m\3\.
    \46\ For example, MSHA preliminarily reviewed control measures 
the could reliably maintain exposures throughout mines to levels of 
25 [micro]g/m\3\ or lower and determined these likely would include, 
as a minimum, installing multiple layers of engineering controls at 
every point throughout the entire mine site by: concurrently 
enclosing and installing ventilation along the full length of every 
conveyor, fully enclosing all process equipment, doubling or 
quadrupling all ventilation system airflow, rebuilding ventilation 
systems to capture dust at its source, installing HEPA filters at 
air exhaust points, converting to automated processes, and 
maintaining all worksurfaces damp at all times.
---------------------------------------------------------------------------

    Comments on the analytical limit of detection and reliability 
relative to the action level relate to analytical methodology and are 
addressed in Section VII.2.b. Analytical Methods and Feasibility of 
Measuring Below the PEL and Action Level.
    Section VIII.B.2.a. Action Level also addresses these and other 
comments related to the action level (25 [micro]g/m\3\).
    The action level is an important provision of this final rule, 
necessary to protect miners' health. According to NIOSH research, 
wherever exposure measurements are above one-half the PEL, the employer 
cannot be reasonably confident that the employee is not exposed to 
levels above the PEL on days when no measurements are taken (NIOSH, 
1975). Thus, an action level (in this case set at one-half of the PEL) 
allows mine operators to take action before overexposures occur. The 
action level of 25 [micro]g/m\3\ remains unchanged in the final rule 
and the methodology supporting the technological feasibility analysis 
for the action level in the proposed rule remains in effect for this 
final rule.
    MSHA finds that the PEL of 50 [micro]g/m\3\ is technologically 
feasible. This determination is based on MSHA's sound methodology and 
process for analyzing technological feasibility and control technology 
currently used in mines (described in this section and Section 
VII.A.1.b.), including the MSHA exposure profiles in Tables VII-1 
through VII-4, which show that using the exposure control measures 
already in place, most mine operators are already achieving the PEL for 
most miners.
2. Technological Feasibility of Sampling and Analytical Methods
a. Sampling Methods
    MSHA's final rule requires mine operators in both MNM and coal 
mines to conduct sampling for respirable crystalline silica using 
respirable particle size-selective samplers that conform to the 
``International Organization for Standardization (ISO) 7708:1995: Air 
Quality--Particle Size Fraction Definitions for Health-Related 
Sampling'' standard. The ISO convention defines respirable particulates 
as having a 4 micrometer ([micro]m) aerodynamic diameter median cut-
point (i.e., 4 [micro]m-sized particles are collected with 50 percent 
efficiency), which approximates the size distribution of particles that 
when inhaled can reach the alveolar region of the lungs. For this 
reason, the ISO

[[Page 28289]]

convention is widely considered biologically relevant for respirable 
particulates and provides appropriate criteria for equipment used to 
sample respirable crystalline silica.
    MSHA received supportive comments from Badger Mining Corporation 
(BMC), National Mining Association (NMA), and SKC Inc., regarding the 
requirement for samplers to conform to ISO 7708:1995 (Document ID 1417; 
1428; 1366). BMC reported having no objection to MSHA's sampling device 
provisions proposed here (Document ID 1417). NMA encouraged MSHA to 
clarify that any sampling technology that meets the characteristics for 
respirable-particle-size-selective samplers that conform to the ISO 
7708:1995 standard is acceptable for air sampling under the rule 
(Document ID 1428). NMA, BMC, and SKC, Inc. each mentioned currently 
available sampling equipment that meets the ISO criteria (Document ID 
1428; 1417; 1366), and the manufacturer SKC, Inc. pointed out that, for 
respirable crystalline silica sampling, mine operators can use any 
respirable dust sampling device that conforms to ISO 7708:1995 (and 
where appropriate, meets MSHA permissibility requirements) (Document ID 
1366). In the Section-by-Section analysis of this preamble, MSHA 
clarifies that mine operators are allowed to use any type of sampling 
device for respirable crystalline silica sampling, as long as the 
device is designed to meet the characteristics for respirable-particle-
size-selective samplers that conform to the ISO 7708:1995 standard and, 
where appropriate, meet MSHA permissibility 
requirements.47 48
---------------------------------------------------------------------------

    \47\ To comply with the final rule requirement for using 
respirable particulate samplers that meet the ISO 7708:1995 
criteria, those coal mine operators that currently use coal mine 
dust personal sampler units (CMDPSU) will need to adjust their 
samplers to the flow rate specified by the sampler manufacturer for 
complying with the ISO standard. This means that mine operators who 
wish to use sampling devices that include a Dorr-Oliver cyclone can 
adjust the associated sampling pumps so they operate at a flow rate 
of 1.7 L/min to meet the ISO criteria. MSHA reminds mine operators 
that they must continue to ensure any sampling equipment used in 
underground coal mines is approved under Title 30 Part 74--Coal Mine 
Dust Sampling Devices.
    \48\ Mine operators must continue to ensure sampling equipment 
used in underground coal mines is approved under Title 30 Part 74--
Coal Mine Dust Sampling Devices.
---------------------------------------------------------------------------

    The American Exploration & Mining Association (AEMA), NMA, and 
Portland Cement Association expressed concern that sufficient samplers 
(and sampling pumps) might not be available by the proposed compliance 
date (Document ID 1424; 1428; 1407).
    As discussed in more detail in Section VIII.B. Section-by-Section 
Analysis, MSHA has extended the compliance dates for the final rule (24 
months from publication of the final rule for MNM and 12 months from 
publication for coal) in response to concerns about the availability of 
sampling equipment, among other things. MSHA believes that this will 
resolve compliance date concerns but if concerns are not resolved by 
the time operators must comply, MSHA may exercise enforcement 
discretion as necessary.
    MSHA received comments both for and against the proposed 
requirement of sampling within 180 days after the effective date of the 
final rule to complete the baseline sampling requirements, with most 
commenters stating, for a variety of reasons, that it was not enough 
time and recommending a longer period ranging from 1 year to 3 years. 
The Metallurgical Coal Producers Association (MCPA) and MSHA Safety 
Services, Inc. stated that providing only 180 days to complete baseline 
sampling is not sufficient because of the limitation of available 
resources for conducting sampling (Document ID 1406; 1392). The 
Portland Cement Association, SSC, and the NMA stated that this 
requirement may not be feasible for many operators because of 
competition for outsourced resources such as rental equipment, media, 
professional services, and laboratory sample analysis (Document ID 
1407; 1432;1428). Concerned that mine operators will be competing to 
obtain these resources, the Portland Cement Association and National 
Lime Association (NLA) stated that small mines are likely to have the 
greatest difficulty in finding these resources in a short period of 
time (Document ID 1407; 1408). The NSSGA, NLA, BMC, and the Arizona 
Mining Association each expressed concerns about performing other tasks 
within the proposed timeframe for compliance, including establishing 
contracts with accredited laboratories and other service providers 
necessary for sampling, performing sampling for all miners who may 
reasonably be expected to be exposed to respirable crystalline silica, 
and designing and implementing new engineering controls (Document ID 
1448; 1408; 1417; 1368). The NSSGA also urged MSHA to factor in the 
increased demand that might result from the state of California's 
effort to promulgate an Emergency Temporary Standard on silica 
(Document ID 1448). The MCPA and the Portland Cement Association 
recommended a phased timeline similar to the OSHA silica rule (which 
gave employers one year before the commencement of most requirements 
and two years before the commencement of sample analysis methods) and 
the MSHA 2014 RCMD Standard (which gave operators 18 months after the 
rule became effective) for completing sampling (Document ID 1406; 
1407).
    Other commenters considered the rule feasible and practical. The 
AFL-CIO stated that technologically feasible air sampling and analysis 
exist to achieve the proposed PEL using commercially available samplers 
(Document ID 1449). This commenter noted that these technologically 
feasible samplers are widely available, and a number of commercial 
laboratories provide the service of analyzing dust containing 
respirable crystalline silica. One individual supported the proposed 
requirement that baseline sampling be conducted within 180 days of the 
rule's effective date (Document ID 1367).
    Samplers used in both MNM and coal mines can be used to perform the 
sampling, and because other commercially available (already on the 
market) samplers also conform to the ISO standard, MSHA finds that 
sampling in accordance with the ISO standard is technologically 
feasible and the technological feasibility analysis supporting the 
sampling methods provisions in the proposed rule remain in effect for 
this final rule.
b. Analytical Methods and Feasibility of Measuring Below the PEL and 
Action Level
    After a respirable dust sample is collected and submitted to a 
laboratory, it must be analyzed to quantify the mass of respirable 
crystalline silica present. The laboratory method must be sensitive 
enough to detect and quantify respirable crystalline silica at levels 
below the applicable concentration. The analytical limit of detection 
(LOD) and/or limit of quantification (LOQ), together with the sample 
volume, determine the airborne concentration LOD and/or LOQ for a given 
air sample. MSHA's final PEL for respirable crystalline silica is 50 
[mu]g/m\3\ as a full shift, 8-hour TWA for both MNM and coal mines. 
Several analytical methods are available for measuring respirable 
crystalline silica at levels well below the PEL of 50 [mu]g/m\3\ and 
action level of 25 [mu]g/m\3\.
    MSHA uses two main analytical methods (1) P-2: X-Ray Diffraction 
Determination Of Quartz And Cristobalite In Respirable Metal/Nonmetal 
Mine Dust (analysis by X-ray diffraction, XRD) for MNM mines and (2) P-
7: Determination Of Quartz In Respirable Coal Mine Dust By Fourier 
Transform Infrared Spectroscopy

[[Page 28290]]

(analysis by infrared spectroscopy, FTIR or IR) for coal mines.\49\ The 
MSHA P-2 and P-7 methods reliably analyze compliance samples collected 
by MSHA inspectors. The exposure profile portion of this technological 
feasibility analysis included 15 years of MNM compliance samples and 5 
years of coal industry compliance samples MSHA analyzed with these 
methods. These methods can measure respirable crystalline silica 
exposures at levels below the PEL and action level.
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    \49\ Other similar XRD methods include NIOSH-7500 and OSHA ID-
142. XRD methods distinguish between the different polymorphs--
quartz, cristobalite and tridymite. Other IR methods include NIOSH 
7602 and 7603. IR methods, while efficient, are prone to 
interferences and should only be used with a well-characterized 
sample matrix (e.g., coal dust).
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    For an analytical method to have acceptable sensitivity for 
determining exposures at the PEL of 50 [mu]g/m\3\ and action level of 
25 [mu]g/m\3\, the LOQ must be at or below the amount of analyte (e.g., 
quartz) that will be collected in an air sample where the concentration 
of analyte is equivalent to the PEL or action level. To determine the 
minimum airborne concentration that can be quantified, the LOQ mass is 
divided by the sample air volume, which is determined by the sampling 
flow rate and duration. Table VII-7 presents minimum quantifiable 
quartz concentrations that can be measured using particle size-
selective samplers under various sampling parameters and established 
analytical method reporting limits.
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    Two commenters mentioned the need for sampling devices with real-
time or near real-time sample analysis capabilities for respirable 
crystalline silica (Document ID 1428; 1449). One of these commenters, 
the NMA, noted that personal dust monitoring devices with real-time 
analysis did not appear in the proposed respirable crystalline silica 
rule, noting that this equipment was included in MSHA's 2014 Coal Dust 
Rule (Document ID 1428). The commenter recommended that MSHA adopt new 
technology from the domestic or international mining community to 
better protect miners. Also interested in new technology, the AFL-CIO 
stated that, to more appropriately characterize exposures, MSHA should 
incorporate continuous and rapid quartz monitoring systems into the 
rule (Document ID 1449).
    MSHA agrees with these commenters that new technology, such as 
real-time dust monitors and NIOSH's rapid field-based quartz monitoring 
(RQM) system with end-of-shift reporting \50\ can help mine operators, 
for example by identifying overexposure conditions while the operator 
evaluates and implements controls to reduce exposure. MSHA is not, 
however, including instruments such as those mentioned by the 
commenters in the

[[Page 28291]]

final rule because the Agency has reviewed the information on these 
instruments and decided that analysis of samples using accredited 
laboratories is the most accurate and reliable method of determining 
respirable crystalline silica exposures for compliance purposes. The 
final rule is the same as the proposal. Nevertheless, MSHA recommends 
that operators stay aware of and evaluate advances in technologies to 
identify control options that facilitate compliance, improve mine 
operator and miner awareness, and improve miner health.
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    \50\ NIOSH Information Circular 9533, ``Direct-on-filter 
Analysis for Respirable Crystalline Silica Using a Portable FTIR 
Instrument'' provides detailed guidance on how to implement a field-
based end-of-shift respirable crystalline silica monitoring program.
---------------------------------------------------------------------------

    A commenter, AISI, expressed concern that the action level was too 
close to the limit of accurate detection of respirable crystalline 
silica (Document ID 1426) and one commenter, SSC, stated that there is 
little confidence in the reliability of sampling results below 50 
[mu]g/m\3\ (Document ID 1432).
    MSHA agrees that limits of detection and reliability are important 
considerations, and, in this context, the agency carefully reviewed 
currently available sampling equipment and analytical methods as part 
of the final rule and in Table VII-7. In Table VII-7, MSHA demonstrates 
how exposure levels well below the PEL and action level can be reliably 
quantified using particle size-selective samplers under various 
sampling parameters and established analytical method reporting limits. 
The minimum quantifiable quartz concentrations shown in Table VII-7 are 
all less than 25 [mu]g/m\3\ and all but one are 12 [mu]g/m\3\ or less, 
therefore well below the action level (25 [mu]g/m\3\).
    MSHA finds that current analytical methods are sufficiently 
sensitive to meet the PEL and action level in the final rule. This 
finding is based on information presented in this section showing the 
availability and sensitivity of MSHA, NIOSH, and OSHA analytical 
methods capable of measuring respirable crystalline silica 
concentrations below 50 [mu]g/m\3\ and 25 [mu]g/m\3\.
c. Laboratory Capacity
    MSHA's final rule requires, for sample analysis, that mine 
operators use laboratories that meet ISO 17025, General Requirements 
for the Competence of Testing and Calibration Laboratories (ISO 17025). 
The majority of U.S. industrial hygiene laboratories that perform 
respirable crystalline silica analysis are accredited to ISO 17025 by 
the American Industrial Hygiene Association (AIHA) Laboratory 
Accreditation Program (LAP). The AIHA LAP lists 30 accredited 
commercial laboratories nationwide that, as of November 2023, performed 
respirable crystalline silica analysis using an MSHA, NIOSH, or OSHA 
method.
    MSHA received comments in support of the requirement for sample 
analysis by the AIHA and the American Association for Laboratory 
Accreditation (A2LA) (Document ID 1351; 1388). Both commenters agreed 
that MSHA should rely on laboratories accredited to the ISO 17025 
standards. The A2LA explained that relying on accredited laboratories' 
impartiality, expertise, and accuracy will permit MSHA to focus time 
and resources on policy, enforcement actions and other Agency 
responsibilities (Document ID 1388).
    MSHA interviewed three AIHA LAP accredited laboratories (one small-
capacity laboratory,\51\ one medium-capacity laboratory,\52\ and one 
large-capacity laboratory \53\) to estimate their sample-processing 
capacity. Insights from these interviews suggest that laboratories have 
the ability to provide demand capacity during the phase-in of the final 
rule. Collectively, these three laboratories could process 
approximately 33,240 samples by XRD (suitable for MNM mines) and 1,752 
samples by FTIR or IR (suitable for coal mines) within a 6-month 
period. Extrapolating this across all laboratories that can analyze 
respirable crystalline silica samples, MSHA estimates that analysis 
will be available for 664,800 samples for MNM mines and 35,000 samples 
for coal mines over any one-year period. Separately, in its FRIA (and 
summarized in Table VII-8), MSHA estimates the numbers of miners for 
whom the various types of sampling is required under the final rule, in 
the first and each subsequent year after the final rule goes into 
effect.\54\ As shown in Table VII-8, MSHA anticipates that within the 
first 12 months after the final rule effective date, mines will seek 
analysis for a total of 41,599 respirable crystalline silica samples 
(all for coal mines). In the subsequent 12-month period, mines will 
require analysis for 216,183 samples (primarily for MNM mines). The 
number of analyses will begin declining in Year 3, as mine operators 
reduce some miner exposures below the action level. Comparing these 
figures with the demand capacity estimates noted above, MSHA finds that 
there is sufficient processing capacity to meet the sampling analysis 
schedule in the final rule.
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    \51\ The small capacity laboratory has a maximum respirable 
crystalline silica sample analysis capacity of 300 samples per month 
(280 additional samples per month above the current number of 
samples analyzed), a level which the laboratory could sustain for 
two months.
    \52\ The medium capacity laboratory has a maximum respirable 
crystalline silica sample analysis capacity of 2,025 samples per 
month. Surge from the mining industry is considered to replace, 
rather than be in addition to the current number of samples 
analyzed.
    \53\ The large capacity laboratory has a maximum respirable 
crystalline silica sample analysis capacity of 4,500 samples per 
month (3,700 additional samples per month above the current number 
of samples analyzed).
    \54\ The estimated sample counts are based on MSHA's existing 
mine population data and its exposure profile, developed using 15 
years of MNM compliance sampling exposure data and 5 years of data 
from the coal industry, stratified by exposure level (less than the 
action level, from the action level to the final rule PEL, and above 
the final rule PEL). That process was described in the proposed rule 
and is summarized in Section VII.A Technological Feasibility (see 
Subsections VII.A.1.a Methodology and VII.A.1.b The Technological 
Feasibility Analysis Process). From these data, MSHA estimated for 
its FRIA how many first- and second-time samples will represent 
miners likely to have exposure below the action level and require no 
further sampling. Based on its knowledge and experience of the 
mining industry, MSHA further estimated how rapidly mine operators 
will be able to reduce the exposures of the remaining miners to 
levels below the anticipated PEL or action level, and calculated how 
many quarterly, corrective actions, and post-evaluation samples that 
the mines will collect (and require analysis for) over time.
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[[Page 28292]]

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First- and Second-Time Sampling
    MSHA's final rule requires mine operators to commence sampling, by 
the compliance date in the final rule, for each miner who is or may 
reasonably be expected to be exposed to respirable crystalline 
silica.\55\ This requirement simplifies the initial sampling 
requirement described in the proposed rule, which called for a baseline 
sample followed by a confirmatory sample (or other data, as described 
below) if samples revealed concentrations below the action level. The 
final rule eliminates the option of using objective data or historical 
sample data (mine operator and MSHA sample data from the prior 12 
months); all exposure samples used to comply with the rule must be 
collected and analyzed in accordance with the final rule. The changes 
to the proposed rule increase the number of samples that mine operators 
will collect and send to laboratories for analysis. The increased 
sampling will require an initial increase in analytical laboratory 
capacity of approximately 41,599 FTIR sample analyses in the first year 
(between the final rule's effective date and the coal mine compliance 
date), with 29,796 of these for first-time and second-time sampling. In 
the following year, MSHA estimates that MNM mine operators will require 
196,708 XRD sample analyses (in the second year due to the extended MNM 
mine compliance date) of which approximately 124,288 will be first-time 
and second-time samples.\56\
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    \55\ Where several miners perform similar activities on the same 
shift, only a representative fraction of miners (minimum of two 
miners) would need to be sampled, including those expected to have 
the highest exposures.
    \56\ Also in the second year, MSHA anticipates that the coal 
mining industry will require 19,475 analysis by FTIR method; 
relatively few (596) of these will be for first- and second-time 
samples.
---------------------------------------------------------------------------

    All mine operators covered by the rule must initiate sampling by 
the compliance dates, potentially creating a peak demand for analysis 
around those dates. MSHA finds, however, that the final rule is 
feasible for mine operators to secure the services of analytical 
laboratories. First, the extended MNM compliance date permits more time 
to accommodate and prepare for any increase in demand. MSHA expects 
many mine operators will avoid last-minute sampling and begin the 
sampling process earlier than required; thus, the sampling and 
associated analysis will be spread over many months, meaning that any 
eventual peak period for laboratory analysis will be longer and less 
intense (i.e., fewer analyses per month required) than it might be 
otherwise. Additionally, MSHA expects that the extended lead time will 
be sufficient for laboratories to increase their analytical capacity. 
For example, laboratories may acquire additional instrumentation, train 
additional analysts, or add a second or third operating shift. This is 
particularly

[[Page 28293]]

likely given that demand will be based on a regulatory requirement. 
MSHA has determined that the final rule is technologically feasible for 
mine operators to secure laboratories' analytical services.
Above-Action-Level, Corrective Actions, and Post-Evaluation Sampling
    Under Sec.  60.12(a), (b), and (d), mine operators may be required 
to conduct additional sampling. First, when the most recent sampling 
indicates that miner exposures are at or above the action level (25 
[micro]g/m\3\) but at or below the PEL (50 [micro]g/m\3\), the mine 
operator is required to sample within 3 months of that sampling and 
continue to sample within 3 months of the previous sampling until two 
consecutive samplings indicate that miner exposures are below the 
action level. Second, where the most recent sampling indicates that 
miner exposures are above the PEL, the mine operator is required to 
sample after corrective actions are taken to reduce overexposures and 
continue conducting corrective actions sampling until sampling results 
indicate miner exposures are at or below the PEL. Third, if the mine 
operator determines, as a result of the periodic evaluation, that 
miners may be exposed to respirable crystalline silica at or above the 
action level, the mine operator is required to perform sampling to 
assess miners who are or may reasonably be expected to be exposed at or 
above the action level.
    In its standalone Final Regulatory Impact Analysis (FRIA) document 
(referred to as the standalone FRIA document throughout the preamble), 
Table 4-5 ``Estimated Number of Samples Taken by Type and Year,'' MSHA 
estimates that, starting in the first 12-month period after the rule's 
effective date, coal mine operators will secure laboratory services for 
analysis of 5,423 above-action-level samples (those samples required 
when the previous sample is at or above the action level, but at or 
below the PEL), 1,991 corrective actions samples, and 4,390 post-
evaluation samples, in addition to the 29,796 first-time and second-
time samples mentioned in the previous subsection. MSHA assumes that 
coal industry analytical needs will be reduced in subsequent years as 
mine operators reduce miner exposures to levels below the PEL or action 
level. In the second 12-month period, in addition to 596 first-time and 
second time samples, coal mine operators will secure laboratory 
services for analysis for 10,556 above-action-level, 3,934 corrective 
actions, and 4,390 post-evaluation samples.
    Similarly, starting in the second 12-month period (due to the 
extended MNM compliance date), MSHA estimates that MNM mine operators 
will secure laboratory analysis for 36,442 above-action-level, 23,414 
corrective actions, and 12,564 post-evaluation samples (plus the 
124,288 first-time and second-time samples discussed previously). MSHA 
estimates that the MNM industry's need for analysis will be lower in 
the following years as mine operators reduce miner exposures to levels 
below the PEL or action level. In the third 12-month period after the 
rule goes into effect, MNM mines are projected to need analysis for 
2,486 first-time and second-time, 66,764 above-action-level, 43,041 
corrective actions, and 12,564 post-evaluation samples.\57\ Together, 
mine operators will require fewer sample (at least 10,000 fewer) 
analyses in each subsequent year than in the first 12-month period 
(coal sector) and second 12-month period (MNM mines), which are 
considered the ``worst case'' or highest demand periods for analysis 
under this rule.
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    \57\ As noted in Section VII.A.2.c (First- and second-time 
sampling) coal mines will have completed most of their first- and 
second-time sampling during the first year after the rule's 
effective date and MNM mines will complete most of it in the second 
year after the rule goes into effect. MSHA expects only a relatively 
modest amount of this sampling to continue in subsequent years (coal 
mining industry requiring 596 analyses per year and MNM mining 
industry 2,486 analyses per year) due to a steady background level 
of new activities starting or new mines opening.
---------------------------------------------------------------------------

    MSHA estimated that the total number of analyses (699,800) that 
laboratories will be able to perform per year is nearly three times the 
maximum total estimated number of samples analyses required 
(216,183).\58\ The maximum number of sample analyses required will 
occur in the second year after the rule goes into effect.\59\ Based on 
MSHA's evaluation, the Agency finds that above-action-level, corrective 
actions, and post-evaluation sampling are technologically feasible for 
mine operators both in the early years after the rule becomes 
effective, and in subsequent years.\60\
---------------------------------------------------------------------------

    \58\ Excess capacity calculated as: (estimated annual demand 
capacity of 30 AIHA LAP accredited laboratories for sample analysis) 
divided by (maximum number of XRD and FTIR samples for which mines 
will seek analysis) = 699,800/216,183 = 3.2 times more analysis 
available on a yearly basis than the number of sample analyses labs 
will complete in the peak year.
    \59\ The maximum number of samples (the peak) will occur in the 
second 12-month period (second year) after rule's effective date, 
which is the period when MNM mines will conduct most of their first-
time and second-time sampling as well as initiate above-action-
level, corrective actions, and post-evaluation sampling. 
Concurrently, coal mines will continue conducting first-time and 
second-time, above-action-level, corrective actions, and post-
evaluation sampling at somewhat lower rates. See Table 4-5 of the 
standalone FRIA document (estimates presented here are as of 11/26/
2023).
    \60\ Surplus analyses calculated: estimated annual surge 
capacity of 30 AIHA LAP accredited laboratories for sample analysis) 
minus (maximum number of XRD and FTIR samples for which mines will 
seek analysis) = 699,800-216,183 = 483,617 surplus analyses.
---------------------------------------------------------------------------

    The AEMA and NMA expressed concern that laboratory capacity might 
not be available by the proposed compliance date (Document ID 1424; 
1428). As discussed in more detail in Section VIII.B. Section-by-
Section Analysis, MSHA has extended the compliance dates in the final 
rule for MNM and coal (24 months and 12 months from publication of the 
final rule, respectively) in response to concerns about the 
availability of laboratory capacity, among other things. MSHA believes 
that this will resolve compliance date concerns but if concerns are not 
resolved by the time operators must comply, MSHA may exercise 
enforcement discretion as necessary.
    As part of the proposed rule, MSHA examined the capacity of 
laboratories that meet the ISO 17025 standard to conduct respirable 
crystalline sample analyses. MSHA made the preliminary determination 
that there would be sufficient processing capacity to meet the sampling 
analysis schedule envisioned by the proposed rule, and that the 
proposed rule is technologically feasible for laboratories to conduct 
baseline sampling analyses (88 FR 44923). MSHA also preliminarily 
determined that the availability of samplers needed to conduct the 
required baseline sampling is technologically feasible (88 FR 44921). 
This preliminary determination, however, only examined whether sampler 
technology exists to conduct the respirable crystalline silica sampling 
as required under the proposal, not the availability of that technology 
to meet the demands that the final rule will impose.
    MSHA agrees with commenters that the sampling requirements of the 
final rule will create an initial rush for sampling devices and related 
equipment and services. MSHA understands that there are more sampling 
devices (as well as related services and supplies) currently available 
in the market now than prior to OSHA's proposed silica rule. 
Nevertheless, based on OSHA's successful promulgation of that Agency's 
2016 respirable crystalline silica final rule that included new silica 
sampling requirements (with similar

[[Page 28294]]

ISO compliant sampling equipment and analytical method provisions for 
both general industry and the construction industry), MSHA expects that 
there will be another additional increase in demand (for equipment, 
services, and supplies) caused by this final rule. MSHA expects that 
the sampling device market will respond to the Agency's rule. MSHA does 
not expect that mines will experience a shortage of sampling resources 
due to a California emergency temporary standard (ETS) to address 
silicosis among engineered stone fabrication facility workers (e.g., 
kitchen countertop shop employees who often use powered hand tools to 
grind/shape engineered stone, which has a quartz content greater than 
most natural stone).\61\ Any increased demand of sampling equipment, 
services, or silica analysis for the mining industry will be related to 
MSHA's rule.
---------------------------------------------------------------------------

    \61\ The California ETS went into effect on December 29, 2023. 
The ETS includes revisions to protect workers engaged in high-
exposure tasks (cutting, grinding, etc.) involving artificial stone 
and natural stone containing more than 10% crystalline silica.
---------------------------------------------------------------------------

    Resource limitations may be an issue for MNM mine operators since 
there are far more MNM mines in the U.S. compared to coal mines (in 
2021, there were 11,231 MNM mines compared to 931 coal mines). As such, 
the expected demand for sampling devices, supplies, and services to 
meet the sampling requirements of this final rule is expected to be 
greater for MNM mines compared to coal mines.
    MSHA carefully considered the above information about availability 
of laboratory capacity and sampling devices, including the likely 
increase in demand for such services and devices. MSHA acknowledges 
commenters' concerns about the need for more time to conduct sampling 
and implement necessary engineering controls. Accordingly, MSHA has 
adjusted the requirements in the final rule to allow MNM mine operators 
a total of 24 months after the publication date of the final rule to 
comply. This will provide sufficient time for MNM mine operators to 
comply with the requirements of part 60. Actions the operator may take 
in preparation for compliance with part 60 may include, for example, 
purchasing sampling equipment, securing sampling services, making 
arrangements with laboratories, and performing sampling. MSHA has 
changed the requirements in the final rule to allow coal mine operators 
a total of 12 months after publication of the final rule to come into 
compliance. MSHA expects that the extended time for compliance will 
provide coal mine operators with time to purchase additional sampling 
equipment and acquire necessary laboratory services. MSHA also notes 
that the AIHA, an accrediting body for commercial laboratories that 
analyze respirable crystalline silica, concurred with MSHA's findings 
that technologically feasible samplers are widely available, and a 
number of commercial laboratories provide the service of analyzing dust 
containing respirable crystalline silica (Document ID 1351). Additional 
discussion of the compliance dates can be found in Section VIII.A.1.c. 
Compliance Dates.
3. Technological Feasibility of Respiratory Protection (Within Part 60)
    Under MSHA's final rule, respiratory protection will not be allowed 
for compliance. As discussed elsewhere, MSHA has determined that the 
PEL is feasible for all mines and all mines must comply with it. 
However, when exposures are above the PEL, mine operators must take 
immediate corrective actions, provide miners with respirators, and 
ensure that they are worn until exposures are below the PEL. There is a 
sufficient supply of respirators for mine operators to obtain and 
maintain for temporary use. Therefore, MSHA has determined that the 
requirements in the final rule for respirator use are technologically 
feasible. This finding is supported by the Agency's knowledge of and 
experience with the mining industry, evidence presented by NIOSH 
(2019b, 2021a), and Tables VII-1 through VII-4 (exposure profiles for 
MNM and coal mines). These tables indicate that the PEL (50 [mu]g/m\3\) 
has already been achieved for approximately 82 percent of the MNM 
miners and approximately 93 percent of the coal miners sampled by MSHA. 
MSHA believes that this data supports the Agency's approach to 
respirator use in the final rule.
    Section 60.14(b) requires that any miner unable to wear a 
respirator must receive a temporary job transfer to an area or to an 
occupation at the same mine where respiratory protection is not 
required. The paragraph also requires that a miner transferred under 
this requirement continue to receive compensation at no less than the 
regular rate of pay in the occupation held by that miner immediately 
prior to the transfer. MNM mine operators must already comply with the 
job transfer provisions under the existing standard in Sec.  
57.5060(d)(7) that requires mine operators to transfer miners unable to 
wear a respirator to work in an existing position in an area of the 
mine where respiratory protection is not required. Section 60.14(b) is 
similar to these existing requirements. MSHA finds that mine operators 
will have a similar experience implementing the job transfer provisions 
of Sec.  60.14(b). As discussed in Section VIII.B.7.b. Section 
60.14(b)--Miners unable to wear respirators, MSHA concludes that 
temporary transfer of miners unable to wear respirators to a separate 
area or occupation to ensure their health and safety is feasible. As 
noted elsewhere in the preamble, any respirator use will be temporary 
to protect miners from overexposures during activities such as the 
implementation or development engineering controls. Therefore, MSHA 
finds that the requirement in Sec.  60.14(b) is technologically 
feasible.
    For miners who need to wear respiratory protection on a temporary 
basis, section 60.14(c)(1) requires the mine operator to provide NIOSH-
approved atmosphere-supplying respirators or NIOSH-approved air-
purifying respirators equipped with high-efficiency particulate filters 
in one of the following NIOSH classifications under 42 CFR part 84: 100 
series or High Efficiency (HE). As discussed below in the Section-by-
Section analysis, MSHA finds that particulate respirators meeting these 
criteria will offer the best filtration efficiency (99.97 percent) and 
protection for miners exposed to respirable crystalline silica and are 
widely available and used by most industries. This finding is based on 
the characteristics of the 100 series as compared to the other two most 
common series (95 and 99). The 95- and 99-series particulate 
respirators do not offer as high a degree of protection as the 100-
series (95 percent and 99 percent efficiency, respectively), and are 
less likely to provide the expected level of protection due to concerns 
about poor fit and vulnerability to mishandling such as folding or 
crushing. The NIOSH-approved 100-series particulate respirators also 
have broad commercial availability.\62\ NIOSH publishes a list of 
approved respirator models along with manufacturer/supplier 
information. In November 2022, the NIOSH-approved list contained 221 
records on atmosphere-supplying respirator models, 160 records on 
elastomeric respirators with P-100 classification, and 23 records on 
filtering facepiece respirators with P-100 classification (NIOSH, 2022a 
list P-100 elastomeric, P-100 filtering facepiece, and atmosphere-
supplying respirator

[[Page 28295]]

models).\63\ Based on this information regarding the level of 
protection and the market availability, MSHA finds that Sec.  
60.14(c)(1) is technologically feasible.
---------------------------------------------------------------------------

    \62\ Class 100 particulate respirators (currently the most 
widely used respirator filter specification in the U.S.) are 
available from numerous sources including respirator manufacturers, 
online safety supply companies, mine equipment suppliers, and local 
retail hardware stores.
    \63\ The NIOSH list of approved models does not guarantee that 
each model is currently manufactured. However, the list does not 
include obsolete models, and the more popular models are widely 
available, including in bulk quantities.
---------------------------------------------------------------------------

    Section 60.14(c)(2) incorporates the ASTM F3387-19 ``Standard 
Practice for Respiratory Protection'' to ensure that the most current 
and protective respiratory protection practices are implemented by mine 
operators who temporarily use respiratory protection to control miners' 
exposures to respirable crystalline silica. The Agency is also 
incorporating this respiratory protection consensus standard under 
Sec. Sec.  56.5005, 57.5005, and 72.710. This update is also addressed 
in the next section (see Technological feasibility of updated 
respiratory protection standards). Based on the information contained 
in that section, MSHA finds that Sec.  60.14(c)(2) is technologically 
feasible.
4. Technological Feasibility of Updated Respiratory Protection 
Standards (Amendments to 30 CFR Parts 56, 57, and 72)
a. Incorporation by Reference
    This section discusses the update to MSHA's existing respiratory 
protection standards in 30 CFR 56.5005, 57.5005, and 72.710 which deal 
with other airborne contaminants and do not include respirable 
crystalline silica. Respiratory protection requirements for respirable 
crystalline silica are in final Sec.  60.14 and are substantially 
similar to MSHA existing standards. Respirators are used by mine 
operators to protect miners against respiratory hazards, including 
particulates, gases, and vapors. Under existing standards, for MNM and 
coal mine operators, respirators must not be used in place of 
engineering controls to control airborne contaminants. If respirable 
coal mine dust samples exceed the standard, coal mine operators must 
make approved respiratory equipment available to affected miners while 
taking immediate corrective actions to lower the concentration of 
respirable dust to at or below the respirable dust standard. Metal and 
nonmetal mine operators must provide miners with respirators and miners 
must use respirators while engineering control measures are being 
developed or when necessary by the nature of work involved (for 
example, while establishing controls or occasional entry into hazardous 
atmospheres to perform maintenance or investigation).
    Where respirators are used, they must seal and isolate the miner's 
respiratory system from the contaminated environment. The risk that a 
miner will experience an adverse health effect from a contaminant when 
relying on respiratory protection is a function of the toxicity or 
hazardous nature of the air contaminants present, the concentrations of 
the contaminants in the air, the duration of exposure, and the degree 
of protection provided by the respirator. When respirators fail to 
provide the expected protection, there is an increased risk of adverse 
health effects. Therefore, it is critical that respirators perform as 
they are designed.
    Accordingly, MSHA is incorporating by reference ASTM F3387-19 by 
amending Sec. Sec.  56.5005, 57.5005, and 72.710 to replace the 
Agency's existing respiratory protection standard in those sections. 
Final Sec. Sec.  56.5005, 57.5005, and 72.710 requires mine operators 
to develop a written respiratory protection program meeting the 
requirements in accordance with ASTM F3387-19. These requirements allow 
for achieving expected protection levels from respirator use. This 
revision to MSHA's existing standards will better protect miners who 
temporarily wear respiratory protection.
    The American National Standards Practices for Respiratory 
Protection ANSI Z88.2--1969 was previously incorporated by reference in 
Sec. Sec.  56.5005, 57.5005, and 72.710.\64\ Since MSHA adopted these 
standards, respirator technology and knowledge on respirator protection 
have advanced and as a result, changes in respiratory protection 
standard practices have occurred. ASTM F3387-19 is the most recent 
respirator practices consensus standard and provides more comprehensive 
and detailed guidance. MSHA finds, based on observations during 
enforcement inspections and compliance assistance visits to mines, that 
mines using respiratory protection have also already implemented 
current respiratory protection recommendations and standards such as 
ANSI/ASSE Z88.2--2015 ``Practices for Respiratory Protection'' 
standard, its similar ASTM replacement (the F3387-19 standard), or OSHA 
29 CFR 1910.134--Respiratory protection. ASTM F3387-19 standard 
practices are substantially similar to the standard practices included 
in ANSI/ASSE Z88.2--2015 or OSHA's respiratory protection standards.
---------------------------------------------------------------------------

    \64\ ASTM 3387-19 is the revised version of ANSI/ASSE Z88.2--
2015. In 2017, the Z88 respirator standards were transferred from 
ANSI/ASSE to ASTM International (source: F3387-19, Appendix XI).
---------------------------------------------------------------------------

b. Availability of Respirators
    The updated respiratory protection standard reflects current 
practice at many mines that use respiratory protection and does not 
require the use of new technology. Thus, MSHA finds that the update is 
technologically feasible for affected mines of all sizes.
c. Respiratory Protection Practices
    By amending existing standards to incorporate the updated 
respiratory protection consensus standard (ASTM F3387-19), MSHA intends 
that mine operators will develop effective respiratory protection 
practices that meet the updated consensus standard and that will better 
protect miners from respiratory hazards.
    MSHA presumes that most mines with respiratory protection programs, 
and particularly those MNM mines that have operations under both MSHA 
and OSHA jurisdiction, are already following either the ANSI/ASSE 
Z88.2--2015 standard, the ASTM F3387-19 standard, or OSHA 29 CFR 
1910.134. As several commenters noted, consistency between OSHA and 
MSHA requirements is beneficial for organizations regulated by both 
agencies, as it permits them to more easily comply with a single, 
consistent set of requirements. Mine operators with operations under 
OSHA jurisdiction would, by this logic, choose to comply with 29 CFR 
1910.134 across all operations rather than develop separate programs 
for MSHA-regulated facilities. The respiratory protection program 
elements under ASTM F3387-19 are largely similar to those in the 
previous standard.
    MSHA expects that some operators may need to adjust their current 
respiratory protection practices and standard operating procedures to 
reflect ASTM F3387-19 standard practices. Examples of adjustments 
include formalizing annual respirator training and fit testing; 
updating the training qualifications of respirator trainers, managers, 
supervisors, and others responsible for the respiratory protection 
program; reviewing the information exchanged with the physician or 
other licensed health care professional (PLHCP) conducting medical 
evaluations; and formalizing internal and external respiratory 
protection program reviews or audits.
    Overall, MSHA finds that the amendments to parts 56, 57, and 72 are 
technologically feasible because the requirements of ASTM F3378-19 have 
already been implemented at many mines.
    MSHA received several comments on the Agency's decision to limit 
respirator

[[Page 28296]]

use to temporary and non-routine use. Many commenters opposed this 
limitation in the proposal, including AIHA, Miners Clinic of Colorado, 
ACLC, and Black Lung Clinics (Document ID 1351; 1418; 1445; 1410), 
while others requested more information to help them properly interpret 
the requirement, including SSC, AMI Silica LLC, NSSGA, and AFL-CIO 
(Document ID 1432; 1440; 1448; 1449). The AFL-CIO requested that MSHA 
clarify temporary and non-routine to specify circumstances and time 
limitations (Document ID 1449). Appalachian Voices stated that mine 
construction and coal production should be excluded from the temporary 
and non-routine use of respirators (Document ID 1425).
    The Construction Industry Safety Coalition (CISC) suggested that 
coal miners should be prohibited from working in overexposures while 
using respirators, stating that the working conditions, especially in 
underground coal mines, make it very difficult for miners to 
communicate and work safely while wearing respirators (Document ID 
1430). Many commenters suggested that MSHA utilize the full hierarchy 
of controls to recognize respirators as an acceptable solution when 
combined with other efforts to lower exposure levels, including Arizona 
Mining Association, AEMA, NMA, NVMA, NSSGA, US Silica, SSC, BMC, 
Illinois Association of Aggregate Producers (IAAP) (Document ID 1368; 
1424; 1428; 1441; 1448; 1455; 1432; 1417; 1456). Advocating expanded 
use of respiratory protection, but differing in their approach, a few 
commenters, including SSC, NSSGA, US Silica, and IAAP, wrote that 
respirators are the only feasible means of protection for certain 
tasks, including housekeeping, dust collector maintenance and repair, 
and bagging operations (Document ID 1432; 1448; 1455; 1456). The AEMA 
stated that MSHA should allow the use of respirators, including PAPRs, 
whenever miners are working in exposures above the PEL (Document 1424). 
Another commenter stated that miners should always use respirators, to 
ensure complete protection from respirable crystalline silica 
exposures. MSHA finds that engineering controls, supplemented by 
administrative controls, are technologically feasible and provide 
reliable, consistent protection for miners engaged in the identified 
tasks; MSHA declines to expand the allowable use of respiratory 
protection. MSHA emphasizes that both in the existing standards for MNM 
mines and in Sec.  60.14, respiratory protection use is required to be 
temporary. The Agency emphasizes that it will continue to enforce 
``temporary'' use of respirators as meaning that respirators are used 
for only a short period of time.
    MSHA clarifies that the final rule does not permit the use of 
respirators in lieu of feasible engineering and administrative 
controls. If anything, MSHA has provided greater protection for miners 
by requiring (as opposed to making available) usage of respirators for 
all miners when exposed to respirable crystalline silica above the PEL.
5. Technological Feasibility of Medical Surveillance (Within Part 60)
    Under the final rule, MNM mine operators will be required to 
provide periodic medical examinations performed by a physician or other 
licensed health care professional (PLHCP) or specialist, at no cost to 
the miner. 30 CFR 60.15. The medical surveillance standards extend to 
MNM miners similar protections to those available to coal miners under 
existing standards in 30 CFR 72.100. The requirements in Sec.  60.15 
are consistent with the Mine Act's mandate to provide maximum health 
protection for miners, which includes making medical examinations and 
other tests available to miners at no cost. 30 U.S.C. 811(a)(7).
    Under the final rule, all MNM miners who are employed or have 
already worked in the mining industry must be provided the opportunity 
for an initial voluntary examination starting during an initial 12-
month period that begins no later than the compliance date or during a 
12-month period that begins whenever a new mine commences operations. 
Subsequent medical examinations must be available at least every 5 
years during a 6-month period that begins no less than 3.5 years and 
not more than 4.5 years from the end of the previous 6-month period. 
MNM miners who begin work in the mining industry for the first time 
must receive an initial examination within 60 days of beginning 
employment. After their initial examination, these new miners must be 
provided a follow-up examination within 3 years. If the 3-year follow-
up examination indicates any medical concerns associated with chest X-
ray findings or decreased lung function, these miners must have another 
follow-up examination in 2 years. After this 2-year follow-up 
examination, or if the 3-year follow-up examination indicates no 
medical concerns associated with chest X-ray findings or decreased lung 
function, these miners will be eligible for voluntary periodic 5-year 
examinations, transferring them into the larger cohort of miners 
already employed in the mining industry.
    The final rule requires that medical examinations include a review 
of the miner's medical and work history, a physical examination with 
special emphasis on the respiratory system, a chest X-ray, and a 
pulmonary function test. The medical and work history covers a miner's 
present and past work exposures, illnesses, and any symptoms indicating 
respirable crystalline silica-related diseases and compromised lung 
function. The required chest X-ray must be classified by a NIOSH-
certified B Reader, in accordance with the Guidelines for the Use of 
the International Labour Office (ILO) International Classification of 
Radiographs of Pneumoconioses. The ILO recently made additional 
standard digital radiographic images available and has published 
guidelines on the classification of digital radiographic images (ILO, 
2022). These guidelines provide standard practices for detecting 
changes of pneumoconiosis, including silicosis, in chest X-rays. The 
required pulmonary function test must be conducted by either a 
spirometry technician with a current certificate from a NIOSH-approved 
Spirometry Program Sponsor, or, as discussed in Section VIII.B.8.a. 
60.15(a)--Medical surveillance of this preamble, a pulmonary function 
technologist with a current credential from the National Board for 
Respiratory Care.
    MSHA has determined that it is technologically feasible for MNM 
mine operators to provide periodic examinations as described in the 
previous paragraph. Under the rule, a PLHCP, as defined, does not have 
to be an occupational medicine physician or a physician to conduct the 
initial and periodic examinations required by the rule, but can be any 
health care professional who is state-licensed to provide or be 
delegated the responsibility to provide those services. The procedures 
required (i.e., medical history, physical examination, chest X-ray, 
pulmonary function test) for initial and periodic medical examination 
are commonly conducted in the general population by a wide range of 
practitioners with varying medical backgrounds. Because the medical 
examinations consist of procedures conducted in the general population 
and because MSHA will be giving MNM mine operators flexibility in 
selecting a PLHCP or specialist able to offer these services, MSHA 
determined that operators will not experience difficulty in finding 
PLHCPs or specialists who are licensed to provide these services.

[[Page 28297]]

    Overall, MSHA finds that the medical surveillance provisions are 
technologically feasible and in the final rule maintains the proposed 
medical surveillance provisions, with some modifications.
    MSHA received several comments on the feasibility of proposed Sec.  
60.15(a). The AIHA, the American Association of Nurse Practitioners 
(AANP), and CertainTeed, LLC supported MSHA's proposal to require MNM 
mine operators to provide MNM miners with medical examinations 
performed by a PLHCP or specialist (Document ID 1351; 1400; 1423). The 
Arizona Mining Association and the BIA expressed concerns with this 
requirement and asserted that many MNM mines may experience issues with 
access to a PLHCP or specialist qualified to perform the examinations 
(Document ID 1368; 1422). The APHA, the AOEC, and the ACOEM advocated 
for medical surveillance to be performed by physicians who are board-
certified in occupational medicine or pulmonary medicine (Document ID 
1416; 1373; 1405). The Hon. Rep. Robert C. ``Bobby'' Scott and an 
individual recommended that MNM miners should be able to choose their 
own health care provider (Document ID 1439; 1412). The AIHA and Black 
Lung Clinics stated that MSHA should require MNM miners to use NIOSH-
approved facilities (Document ID 1351; 1410) while the AEMA and the NMA 
(Document ID 1424; 1428) expressed concerns about the limited 
availability of these facilities. The NMA, the Portland Cement 
Association, and the AEMA noted that there are only a limited number of 
B Readers available (Document ID 1428; 1407; 1424).
    MSHA reviewed these comments and made one change to Sec.  60.15(a) 
in the final rule. Under the proposed rule, a pulmonary function test 
must be administered by a spirometry technician with a current 
certificate from a NIOSH-approved Spirometry Program Sponsor. In the 
final rule, paragraph 60.15(a)(2)(iv) retains that language but adds 
pulmonary function technologists with current credentials from the 
National Board for Respiratory Care as individuals who may administer 
pulmonary function tests. This addition to the final rule text should 
further expand the pool of individuals eligible to administer pulmonary 
function tests.
    MSHA determined that MNM mine operators should not experience any 
significant issues identifying a PLHCP or specialist to conduct medical 
examinations and emphasizes the final rule allows flexibility by not 
mandating that the medical examinations be conducted by full-time 
health care professionals employed by mine operators. As stated in the 
proposal, a PLHCP is an individual whose legally permitted scope of 
practice (i.e., license, registration, or certification) allows that 
individual to independently provide or be delegated the responsibility 
to provide some or all of the required health services (i.e., chest X-
rays, pulmonary function test, symptom assessment, and occupational 
history). Specialist is defined in Sec.  60.2 as an American Board-
Certified Specialist in Pulmonary Disease or an American Board-
Certified Specialist in Occupational Medicine. MSHA also clarifies that 
if medical examinations are integrated within health care plans, mine 
operators must ensure that the examinations are conducted in accordance 
with the requirements in Sec.  60.15. MSHA determined that the 
requirements for testing and interpretation of results are 
technologically feasible.
    The Agency has reviewed the comments related to availability of B 
Readers. MSHA has determined that, based on technological improvements 
that remove the need for geographic proximity between patients and 
technicians such as B Readers, as well as widespread availability of 
tests such as X-rays, getting X-ray tests and the results classified by 
B Readers is technologically feasible. With respect to chest X-ray 
classification, the availability of digital X-ray technology permits 
electronic submission to remotely located B Readers for interpretation. 
After consulting NIOSH, MSHA determined there are B Readers with remote 
reading capabilities available to meet the demands of the final rule. 
Therefore, MSHA finds that the limited number of B Readers in certain 
geographic locations will not be an obstacle for MNM operators. MSHA 
further concludes that any increase in demand for these services can be 
addressed by providers. Further discussion regarding NIOSH-approved 
facilities and B Readers can be found in Section VIII.B.8.a. Section 
60.15(a)--Medical Surveillance of this preamble.
    MSHA's experience with the coal mine medical surveillance program 
has shown the Agency that PLHCPs who have the required NIOSH or other 
certifications have the training to effectively examine miners and 
identify the occurrence or progression of silica-related diseases, even 
if they may not operate within NIOSH-approved facilities. MSHA's 
updated research continues to support OSHA's conclusion in its 2016 
silica final rule that the number of B Readers in the United States is 
adequate to classify chest X-rays (OSHA 2016a, 81 FR 16286, 16821). 
Further, an increased demand for B Readers as a result of this final 
rule will lead to additional training for many health care providers. 
In addition, digital X-rays can be easily transmitted electronically to 
B Readers anywhere in the United States. The final rule ensures that 
medical examinations are comprehensive and tailored to discern and 
mitigate potential health risks associated with miners' occupational 
exposures to respirable crystalline silica. The final rule will ensure 
that the medical examinations are both robust and flexible enough to 
accommodate advancements and variations in medical evaluation 
techniques. Further discussion regarding NIOSH-approved facilities and 
B Readers can be found in Section VIII.B.8.a. Section 60.15(a)--Medical 
Surveillance of this preamble.
    The final rule does not require that examinations conducted under 
this section occur in NIOSH-approved facilities. There are only 168 
NIOSH-approved health clinics nationwide. NIOSH manages the Coal 
Workers' Health Surveillance Program and the program's facilities are 
concentrated in geographies where coal mining is prevalent (e.g., 
Appalachia, the Illinois Basin, and Powder River Basin). The NIOSH-
approved facilities are not uniformly distributed across the U.S. and 
there are many areas that have MNM mines but do not have NIOSH-approved 
facilities (e.g., the states California, Idaho, Nevada, and 
Washington). Therefore, MSHA has determined that it is not feasible to 
require NIOSH-approved facilities for medical surveillance in MNM 
mines.

[[Page 28298]]

6. Conclusions
    Based on MSHA's technological feasibility analysis, MSHA has 
determined that all elements of the rule on Lowering Miners' Exposure 
to Respirable Crystalline Silica and Improving Respiratory Protection 
are technologically feasible.

B. Economic Feasibility

    MSHA considers economic feasibility in terms of industry-wide 
revenue and overall costs incurred by the mining industry (inclusive of 
MNM and coal) under a given rule. To establish economic feasibility, 
MSHA uses a revenue screening test--whether the estimated yearly costs 
of a rule are less than 1 percent of estimated revenues or are negative 
(i.e., provide net cost savings)--to presumptively establish that 
compliance with the regulation is economically feasible for the mining 
industry. If annualized compliance costs comprise less than 1 percent 
of revenue, the Department concludes that the entities can incur the 
compliance costs without significant economic impacts.\65\ MSHA 
received comments on economic feasibility. Several commenters argued 
that it would cost thousands or millions of dollars in exposure control 
costs to meet the new PEL (Document ID 1419; 1441; 1448; 1455). Others 
noted that the action level will result in more sampling above the 
action level and additional engineering controls needed to get below 
the action level, leading to greater costs (Document ID 1419, 1455).
---------------------------------------------------------------------------

    \65\ MSHA is not required to produce hard and precise estimates 
of cost to establish economic feasibility. Rather, MSHA must provide 
a reasonable assessment of the likely range of costs of its 
standard, and the likely effects of those costs on the industry. See 
United Steelworkers, 647 F.2d at 1264; see also Nat'l Min. Ass'n, 
812 F.3d at 865.
---------------------------------------------------------------------------

    Based on its analysis of the Agency's sampling database, MSHA 
believes roughly 90 percent of mines will be able to meet the PEL 
without incurring additional costs, and only 580 mines will need to 
install engineering control to meet the new PEL (see standalone FRIA 
document Section 4). In response to public comments that MSHA 
underestimated the cost of implementing necessary exposure controls, 
MSHA increased its estimate of the number of mine operators that will 
have to implement additional exposure controls to meet the requirements 
of the final rule.
    One commenter pointed out that engineering controls need to factor 
in site-specific conditions (Document ID 1441). MSHA acknowledges that 
the exposure control costs will differ depending on the size of the 
mine, the current level of exposure to respirable crystalline silica, 
existing engineering and administrative controls, the mine layout, work 
practices, and other variables. MSHA's price and cost estimations are 
based on a variety of sources including market research and MSHA's 
experience and sample data. Some of the cost estimates from 
commenters--such as those from very large mines or those representing 
many mines controlled by one operator--are impossible to meaningfully 
compare to MSHA's estimates. Nonetheless, these and other public 
comments about the costs of the final rule are addressed in more detail 
below in Section IX. Summary of Final Regulatory Impact Analysis and 
Regulatory Alternatives, as well as in Section 8 of the standalone FRIA 
document.
    For the MNM and coal mining sectors, MSHA estimates the projected 
impacts of the rule by calculating the annualized compliance costs for 
each sector as a percentage of total estimated revenues for that 
sector. To be consistent with costs that are calculated in 2022 
dollars, MSHA first inflated estimated mine revenues in 2019 to their 
2022 equivalent using the GDP Implicit Price Deflator. See Table VII-9.

[[Page 28299]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.153

    Table VII-10 compares aggregate annualized compliance costs for the 
MNM and coal sectors at a 0 percent, 3 percent, and 7 percent discount 
rates to each sector's total annual revenues. At a 3 percent discount 
rate, total aggregate annualized compliance costs for the entire mining 
industry are projected to be $90.3 million (including both 30 CFR part 
60 and 2019 ASTM costs), while aggregate revenues are estimated to be 
$124.2 billion in 2022 dollars. MSHA estimates that the mining industry 
is expected to incur compliance costs that comprise 0.07 percent of 
total revenues.
    For the MNM sector, MSHA estimated that the annualized compliance 
costs of the final rule (including both 30 CFR part 60 and 2019 ASTM 
update costs) would be $82.1 million at a 3 percent discount rate, 
which is approximately 0.09 percent of the total estimated annual 
revenue of $95.1 billion for MNM mine operators. For the coal sector, 
MSHA estimated that the annualized cost of the final rule (including 
both 30 CFR part 60 and 2019 ASTM costs) will be $8.2 million at a 3 
percent discount rate, which is approximately 0.03 percent of the total 
estimated annual revenue of $29.1 billion for coal mine operators.
    The ratios of screening analysis are well below the 1.0 percent of 
total revenues threshold. Therefore, MSHA concludes that the 
requirements of the final rule are economically feasible, and no sector 
will likely incur a significant cost.
[GRAPHIC] [TIFF OMITTED] TR18AP24.148

VIII. Summary and Explanation of the Final Rule

    As previously mentioned, under the final rule, MSHA amends its 
existing standards on respirable crystalline silica or quartz, after 
considering all the testimonies and written comments the Agency 
received from a variety of stakeholders, including manufacturers, 
medical professionals, miners, mining associations, mining companies, 
labor organizations that represent mine workers, health associations, 
and safety associations in response to its notice of proposed 
rulemaking. The final rule establishes a PEL of respirable crystalline 
silica at 50 [micro]g/m\3\ for a full-shift exposure, calculated as an 
8-hour TWA for all mines. The final rule also establishes an action 
level for respirable crystalline silica of 25 [micro]g/m\3\ for a full-
shift exposure, calculated as an 8-hour TWA for all mines. In addition 
to the PEL and action level, the final rule includes provisions for 
methods of compliance, exposure monitoring, corrective actions, 
respiratory protection, medical surveillance for MNM mines, and 
recordkeeping. The final rule also replaces existing requirements for 
respiratory protection and incorporates by reference ASTM F3387-19 
Standard Practice for Respiratory Protection.

[[Page 28300]]

    The sections that follow address testimonies and written comments 
received on general issues and specific provisions in the proposal and 
MSHA provides its responses and final conclusions.

A. General Issues

    In this section, MSHA addresses comments that relate to the 
rulemaking as a whole and that are not specific to a single section of 
the final rule. MSHA identified six general issues for discussion 
below: Existing Respirable Dust Standards for Coal Mines; Training for 
Miners--Respirable Crystalline Silica; Sorptive Minerals; OSHA Table 1 
Approach for Compliance; Medical Removal/Transfer; and Compliance 
Assistance.
1. Existing Respirable Dust Standards for Coal Mines
    MSHA will enforce the final rule's requirements for respirable 
crystalline silica in coal mines within the context of the Agency's 
existing standards for miners' exposure to respirable coal mine dust in 
30 CFR parts 70, 71, and 90.
    Some commenters, including the Wyoming County WV Black Lung 
Association, AFL-CIO, and two individuals, were concerned that controls 
implemented as immediate corrective actions for respirable crystalline 
silica at coal mines would not be incorporated into an underground coal 
mine's approved ventilation plan required under 30 CFR part 75 
(Document ID 1393; 1449; 1399; 1412).
    Under the final rule, mine operators are required to install, use, 
and maintain feasible engineering and administrative controls to keep 
each miner's exposure to respirable crystalline silica at or below the 
PEL. Mine operators must use feasible engineering controls as the 
primary means of controlling respirable crystalline silica; 
administrative controls can only be used, when necessary, as a 
supplementary control. Rotation of miners--that is, assigning more than 
one miner to a high-exposure task or location, and rotating them to 
keep each miner's exposure below the PEL--is prohibited as a means of 
complying with the rule.
    For underground coal mines, the necessary controls to maintain 
compliance with existing respirable coal mine dust and respirable 
crystalline silica standards are contained in the ventilation plan that 
is approved by the appropriate District Manager. Under 30 CFR 
75.370(a)(1), the approved ventilation plan shall control methane and 
dust and contains the detailed engineering controls that the operator 
will use to comply with the existing dust standards.
    Under the existing respirable dust standards for coal mines, MSHA 
evaluates the approved ventilation plan to ensure that it is suitable 
to current conditions and mining systems at the mine. During each 
shift, the plan must be followed to protect miners from overexposure to 
respirable coal mine dust, which includes respirable crystalline 
silica. Currently, only MSHA sampling is used to evaluate miners' 
exposure to respirable crystalline silica. When respirable coal mine 
dust or respirable crystalline silica overexposures are documented, 
MSHA may consider the relevant portion of the ventilation plan 
deficient and require that the plan be revised to include additional 
ventilation controls, or the plan can be revoked by the Agency, as 
appropriate. MSHA evaluates the approved ventilation plan at least 
every 6 months, or more often if there are changes in the mine, mining 
processes, dust controls, or conditions at the mine affecting miners' 
exposure to respirable coal mine dust or respirable crystalline silica 
dust. MSHA typically samples all mechanized mining units and Part 90 
miners (coal miners with evidence of pneumoconiosis) during each 
quarterly regular inspection of underground coal mines. MSHA typically 
samples the Designated Areas (DA)--outby areas of the mine--at least 
annually. This sampling represents an evaluation of dust exposure 
compliance and dust controls that are in the approved ventilation plan 
to ensure that they are effective. MSHA intends to continue conducting 
this sampling.
    Under the existing respirable dust standards for coal mines, as in 
the final silica rule, when miners are overexposed, the operator must 
take immediate corrective actions to lower the miner's exposure to at 
or below the standard and sample to verify that the corrective actions 
are effective. The mine operator determines necessary engineering 
controls but must address the underlying conditions and practices which 
caused the overexposure. Corrective action sampling will be conducted 
with the control measures in place. Under the final silica rule, mine 
operators must report overexposures to the District Manager and 
corrective actions must be described in the record mandated in Sec.  
60.16. If a silica overexposure occurs, operators remain responsible 
for adjusting ventilation plans to account for additional controls 
needed to prevent future overexposures.
    The existing respirable dust standards for coal mines will also 
maintain silica controls through mine operators' pre-shift and on-shift 
examinations. These examinations must ensure the ventilation controls 
that have been evaluated and found effective are maintained. The 
examinations protect miners from health and safety hazards between and 
on sampling shifts.
    The UMWA, AFL-CIO, Wyoming County WV Black Lung Association, and an 
individual requested that additional sampling be conducted at coal 
mines (Document ID 1398; 1449; 1393; 1382). UMWA and an individual 
supported the standalone silica PEL but urged MSHA to retain the 
reduced dust standard concept due to the large number of quarterly dust 
samples operators must take that indirectly monitor silica exposure 
(Document ID 1398; 1382).
    MSHA's enforcement of respirable coal mine dust under the existing 
respirable coal mine dust standards will continue. The final rule 
establishes a standalone silica PEL and adds operator silica sampling 
that may result in additional operator silica sampling (every three 
months) in many underground coal mines. It also requires immediate 
corrective actions and resampling if exposures exceed the PEL. The 
final rule also requires periodic evaluations at least every 6 months, 
or whenever there is a change in production; processes; installation 
and maintenance of engineering controls; installation and maintenance 
of equipment; administrative controls; or geologic conditions. 
Dependent on the results of the periodic evaluation in this final rule, 
coal mine operators may have to perform additional sampling. MSHA 
expects the final rule's requirements will result in sufficient 
sampling to accurately detect miners' exposures to silica at coal 
mines.
    The final rule requires that mine operators sample miners exposed 
or reasonably expected to be exposed to respirable crystalline silica. 
If samples are above the action level and below the PEL, mine operators 
must continue to sample within three months. Operators must conduct 
representative sampling (at least two samples) of the occupations at 
highest risk of respirable crystalline silica exposure. The existing 
standards for respirable coal mine dust sampling require 15 valid 
representative consecutive shift samples for certain high-dust 
occupations, followed by more samples in other identified occupations 
and areas the District Manager designates based on anticipated or 
actual exposures.
    The final rule decouples silica sampling and enforcement from the 
existing respirable dust standard requirements that reduce the total

[[Page 28301]]

respirable coal mine dust limit based on the percentage of silica in 
the dust (an indirect way of controlling silica). Occupations and areas 
designated for dust sampling are likely to be the occupations and areas 
with the highest levels of respirable crystalline silica exposure. MSHA 
expects many of the same occupations will be sampled under this final 
rule and that the requirement that two samples be taken will mean an 
increased ability to accurately assess exposure. Also, the standalone 
respirable crystalline silica PEL allows for immediate MSHA oversight 
of corrective actions and resampling. Unlike the existing reduced dust 
standard protocols under which silica overexposures are not directly 
citable except through enforcement of the reduced dust standard, under 
the final rule, MSHA can withdraw miners under Mine Act section 104(b) 
if respirable crystalline silica overexposure citations are not 
corrected and occupations resampled within the abatement time MSHA 
sets. In response to comments, and to ensure that MSHA is informed of 
silica overexposures, the final rule requires that mine operators 
immediately report respirable crystalline silica samples above the PEL 
to the District Manager or other office designated by the District 
Manager.
2. Training for Miners--Respirable Crystalline Silica
    MSHA received several comments both in favor of and against 
including respirable crystalline silica training for miners in 30 CFR 
part 46 (Training and Retraining of Miners Engaged in Shell Dredging or 
Employed at Sand, Gravel, Surface Stone, Surface Clay, Colloidal 
Phosphate, or Surface Limestone Mines) (part 46) and 30 CFR part 48 
(Training and Retraining of Miners) (part 48). Two mining trade 
associations suggested that existing training requirements under parts 
46 and 48 for new miner training, experienced miner training, annual 
refresher training, and task training remain sufficient and that an 
additional training requirement would be unnecessary (Document ID 1424, 
1441). Other commenters, including a mining labor union and several 
professional associations, stated that the final rule should include 
new training requirements separate from parts 46 and 48 (Document ID 
1398; 1351; 1377; 1373).
    MSHA believes existing training standards in parts 46 and 48 
require appropriate training regarding health hazards, including 
exposure to respirable crystalline silica dust.
    Part 46 requires new miners and newly hired experienced miners to 
receive training on the health and safety aspects of the tasks to be 
assigned, including the safe work procedures of such tasks, the 
mandatory health and safety standards pertinent to such tasks, 
information about the physical and health hazards of chemicals in the 
miner's work area, the protective measures a miner can take against 
these hazards, and the contents of the mine's HazCom program. They must 
also receive instruction and demonstration on the use, care, and 
maintenance of self-rescue and respiratory devices, if used at the 
mine.
    Annual refresher training conducted under part 46 must include 
instruction on changes at the mine that could adversely affect the 
miner's health or safety and other health and safety subjects relevant 
to mining operations at the mine, including mandatory health and safety 
standards, health, and respiratory devices.
    For new task training, part 46 requires miners to receive training 
in the health and safety aspects of the task to be assigned, including 
the safe work procedures of such tasks, information about the physical 
and health hazards of chemicals in the miner's work area, the 
protective measures a miner can take against these hazards, and the 
contents of the mine's HazCom program. Section 46.9 requires records of 
training and includes specific provisions for the record requirements.
    Part 48 requires new miners to receive training on health including 
instruction on the purpose of taking dust, noise, and other health 
measurements, and any health control plan in effect at the mine shall 
be explained. New miners must also receive training in the health and 
safety aspects of the tasks to be assigned, including the safe work 
procedures of such tasks, the mandatory health and safety standards 
pertinent to such tasks, information about the physical and health 
hazards of chemicals in the miner's work area, the protective measures 
a miner can take against these hazards, and the contents of the mine's 
HazCom program.
    Experienced miner training under Part 48 must include instruction 
in health, including the purpose of taking dust, noise, and other 
health measurements, where applicable, and review of the health 
provisions of the Mine Act. Experienced miners must also receive 
training in the health and safety aspects of the tasks to be assigned, 
including the safe work procedures of such task, information about the 
physical and health hazards of chemicals in the miner's work area, the 
protective measures a miner can take against these hazards, and the 
contents of the mine's HazCom program.
    For new task training, part 48 requires miners to receive training 
on the health and safety aspects and safe operating procedures for work 
tasks, equipment, and machinery, including information about the 
physical and health hazards of chemicals in the miner's work area, the 
protective measures a miner can take against these hazards, and the 
contents of the mine's HazCom program.
    Annual refresher training conducted under part 48 must include 
instruction on mandatory health and safety standard requirements which 
are related to the miner's tasks and on the purpose of taking dust, 
noise, and other health measurements, as well as an explanation of any 
health control plan in effect at the mine. The health provisions of the 
Mine Act and warning labels must also be explained. Sections 48.9 
(Underground Miners) and 48.29 (Surface Miners) require records of 
training.
    Training is also a required element of the mine operator's 
respiratory protection program. Miners required to wear a respirator 
must be trained in accordance with the provisions of ASTM F3387-19 and 
records must be retrained in accordance with the provisions of section 
9.
    MSHA expects mine operators to include information in their 
existing training plans about respirable crystalline silica hazards and 
protections, including: the PEL and action level; sampling 
requirements; miners who are reasonably expected to be exposed to 
respirable crystalline silica; engineering and administrative controls 
used at the mine; the importance of maintaining controls; and, for MNM 
mines, medical surveillance requirements, including the importance of 
early disease detection. MSHA remains available to assist mine 
operators with their training plans.
3. Sorptive Minerals
    The SMI, EMA, and Vanderbilt Minerals, LLC requested that MSHA 
follow OSHA's approach to sorptive minerals and exclude them from the 
scope of the final rule (Document ID 1446; 1442; 1419). These 
commenters asserted that lower toxicity of occluded and aged 
crystalline silica indicates a lack of health risks stemming from 
inhaling sorptive mineral dust containing respirable crystalline 
silica.
    After considering the commenters' statements and evidence, as well 
as OSHA's approach to the issue, MSHA has determined that sorptive 
minerals should not be excluded from the scope of this rulemaking.

[[Page 28302]]

    MSHA evaluated all the evidence submitted by commenters during the 
rulemaking process, including the hearings, and concludes that the 
balance of the best available evidence supports that there is increased 
risk of material impairment of health or functional capacity over the 
course of a miner's working life associated with regular exposure to 
respirable crystalline silica present at sorptive mineral mines. MSHA's 
approach is consistent with NIOSH's recommendation for a single PEL for 
respirable crystalline silica without consideration of surface 
properties. MSHA is unable to substantiate one commenter's statement 
that, in every instance, the silica in sorptive minerals is either 
amorphous (i.e., opal) or occluded. Sorptive minerals occur as part of 
a geological formation with its own depositional history beginning with 
a volcanic eruption. The mining process will encounter all mineral 
constituents in the deposit, including all forms of respirable 
crystalline silica. To remove overburden and extract sorptive minerals, 
miners use large mining equipment that can disturb sedimentary and 
other silica-rich rock that could contain unoccluded respirable 
crystalline silica. In addition, the milling, screening, crushing, and 
bagging processes can and do affect the respirable crystalline silica 
dust liberated at these mines. The commenter did not submit evidence 
demonstrating that all sorptive mineral commodities mined in the United 
States exclusively contain fully or even partially occluded quartz. 
MSHA does not agree that occlusion is always present, that occlusion 
definitively provides adequate protection from adverse health effects, 
or that occlusion always provides any level of protection for miners 
exposed to respirable crystalline silica in this industry.
    MSHA's method for analyzing respirable dust samples cannot 
differentiate between ``freshly fractured'' and occluded crystalline 
silica. Respirable dust enforcement samples in MNM mines are prepared 
for crystalline silica analysis using the MSHA P-2 method for X-ray 
diffraction (XRD). Crystalline materials each have their own unique 
diffraction patterns and are quantitatively discriminated between other 
crystalline and non-crystalline materials through XRD analysis. 
Potential interferences from other minerals are removed from the result 
by scanning the sample at multiple diffraction angles specific to 
crystalline silica and using profile fitting software to separate 
adjacent diffraction peaks. MSHA cannot determine if crystalline silica 
particles in the sample are ``freshly fractured'' or occluded with a 
layer of clay, only that the diffraction pattern matches that of the 
pure crystalline silica standard reference material.
    MSHA's enforcement data in Table VIII-1 below show that miners 
working in this industry are exposed to respirable quartz at 
concentrations above both the former PEL (100 [micro]g/m\3\) and new 
PEL (50 [micro]g/m\3\). Table VIII-1 shows exposure data by contaminant 
code for respirable dust samples collected at ``clay'' or ``bentonite'' 
operations from 2005 to 2019. The samples were analyzed for respirable 
crystalline silica (quartz) and the results were calculated based on an 
8-hour TWA.
[GRAPHIC] [TIFF OMITTED] TR18AP24.155

    The results in the table indicate that 5.1 percent of miners 
working at these operations during the relevant period were exposed to 
levels of respirable crystalline silica over the former PEL of 100 
[micro]g/m\3\, and 17.6 percent were exposed over the new PEL of 50 
[micro]g/m\3\.
    MSHA disagrees with commenters' statements that the silica 
contained in sorptive minerals does not pose health risks. MSHA does 
not equate ``lower toxicity'' with other toxicological terms such as 
``non-hazardous'', ``non-toxic'', or ``safe.'' ``Lower toxicity'' does 
not mean the absence of adverse health effects, disease, or risk of 
material impairment of health or functional capacity. For example, the 
bioactivity of respirable crystalline silica (quartz) originating from 
bentonite deposits is well-recognized and documented on sorptive 
mineral-based pet litter safety data sheets (SDSs). MSHA concludes from 
its own sampling data and analyses that the mining of sorptive minerals 
creates an inhalation hazard. As confirmed by MSHA's review of 
epidemiological and toxicological studies, these mineral dusts are 
toxic and can lead to serious adverse health effects in miners such as 
silicosis or lung cancer. Accordingly, MSHA concludes that there is a 
risk of material impairment of health or functional capacity in mining, 
whether or not that risk is equal to unoccluded quartz encountered in 
other workplaces.
    In its 2016 final rule, OSHA concluded that quartz originating from 
bentonite deposits had some biological activity but ``lower toxicity'' 
than quartz encountered in most workplaces (81 FR 16377). OSHA also 
found that the record provided no sound basis for determining 
significance of risk for exposure to sorptive minerals containing 
quartz, and thus decided to exclude sorptive minerals from the

[[Page 28303]]

scope of the final rule (OSHA, 2016). MSHA, unlike OSHA, has no 
requirement to identify a ``significant risk'' before promulgating 
rules to protect miners' health and safety. Nat'l Mining Ass'n v. 
United Steel Workers, 985 F.3d 1309, 1319 (11th Cir. 2021) (``[T]he 
Mine Act does not contain the `significant risk' threshold requirement 
. . . from the OSH Act.''). The OSH Act is a ``differently worded 
statute,'' and the Mine Act ``[a]rguably . . . does not mandate the 
same risk-finding requirements as OSHA.'' Nat'l Min. Ass'n v. Mine 
Safety & Health Admin., 116 F.3d 520, 527 (D.C. Cir. 1997). Moreover, 
OSHA does not regulate mining; mining presents unique risks to miners' 
health because it exposes miners to hazards that are not present in 
operations regulated by OSHA, including hazards in overburden removal 
and milling.
    MSHA has examined research references from commenters and has 
conducted its own review of the scientific literature. These studies do 
not disprove the health-based risks associated with exposure to 
respirable crystalline silica or support a conclusion that sorptive 
minerals present no risk.
    As presented by SMI, there have been few epidemiological studies of 
workers exposed to dust generated from sorptive minerals (Document ID 
1446, Attachment 2). Two examples include Phibbs et al. (1971) and 
Waxweiler et al. (1988). These small cohort studies did not evaluate 
exposures to a wide variety of sorptive minerals and relied on data 
from outdated exposure assessment methods. MSHA finds that the limited 
epidemiological data involving sorptive minerals do not refute the 
conclusions drawn from other epidemiological studies included in MSHA's 
standalone Health Effects document and in the Agency's standalone FRA 
document (2023). MSHA concludes, from the best available evidence, that 
exposure to the crystalline silica present in sorptive minerals poses a 
risk of material impairment of health or functional capacity to miners.
    MSHA disagrees with the comment that the occluded surface of the 
silica that may be found in sorptive minerals protects miners from 
material impairment of health, including silicosis and lung cancer. 
Furthermore, there is no evidence to suggest that the occluded layer of 
the quartz particles that are inhaled remains unchanged over time 
following deposition throughout the respiratory tract. It is not 
understood how conditions and physiological responses may alter the 
characteristics of occluded quartz particles deposited in the 
respiratory tract. Likewise, while animal studies involving respirable 
crystalline silica suggest that the aged form has lower toxicity than 
the freshly fractured form, the aged form still retains significant 
toxicity (Shoemaker et al., 1995; Vallyathan et al., 1995; Porter et 
al., 2002c).
    MSHA considered commenters' statements and evidence regarding the 
toxicity of quartz in sorptive minerals. MSHA's conclusions are 
consistent with those that NIOSH provided to OSHA (NIOSH Posthearing 
Brief to OSHA, 2014d). NIOSH corrected various erroneous statements 
that referenced published papers (e.g., Waxweiler et al., 1988; Phibbs 
et al., 1971) and reports (e.g., EPA, 1996; WHO, 2005), which are also 
a part of this rulemaking record. Four examples are provided here. 
First, as noted by NIOSH, Phibbs et al. (1971) advised that 
``[b]entonite dust, once believed to be harmless, must now be added to 
the list of potentially hazardous dusts because of its content of free 
crystalline silica.'' (Document ID 0693, pg. 43). Second, NIOSH stated 
that, ``[w]hile no exposure-response relationship can be drawn from the 
Phibbs et al. [1971] study, it can be concluded that when exposures to 
respirable crystalline silica are high enough in mining/processing 
bentonite, severe and fatal occupational silicosis can occur among 
exposed workers.'' (Document ID 0693, pg. 44). Third, contrary to 
comments regarding the WHO report (2005), NIOSH stated, ``Although the 
respirable crystalline silica particles to which these bentonite 
workers were exposed may be less toxic than, say, respirable 
crystalline silica particles resulting from sandblasting, there is no 
way to assess relative toxicities from these two studies. Regardless of 
relative toxicity, the findings from these two studies indicate that, 
at the levels to which the workers in the studies were exposed, the 
crystalline silica particles were toxic enough to cause severe, 
disabling, and fatal silicosis in a relatively short period of time.'' 
Fourth, NIOSH disagreed with the commenter's reference to the lack of 
reporting of silicosis among cohorts of coal miners with pneumoconiosis 
to support its conclusion that aged/occluded silica particles do not 
represent a risk for silica-related health outcomes.
    NIOSH addressed a commenter's presumption that further study was 
needed on occluded quartz before regulation was warranted. NIOSH 
explained that further study on occluded quartz was less pertinent for 
OSHA's rulemaking than the fact that the OSHA PEL was consistent with 
the NIOSH REL in not distinguishing respirable crystalline silica 
exposures based on relative age or degree of occlusion of particle 
surfaces. MSHA concurs with NIOSH's conclusion that ``currently 
available information is not adequate to inform differential 
quantitative risk management approaches for crystalline silica that are 
based on surface property measurements.'' For these reasons, MSHA does 
not exempt the sorptive minerals sector from the requirements of this 
final rule.
4. OSHA Table 1 Approach for Compliance
    OSHA's ``Table 1--Specified Exposure Control Methods When Working 
With Materials Containing Crystalline Silica'' (Table 1) (29 CFR 
1926.1153(c)(1)) identifies common construction equipment and tasks 
that, when properly controlled, are expected to generate levels of 
respirable crystalline silica below the PEL. Construction employers who 
follow these engineering and work practice control methods and provide 
the required respiratory protection outlined in Table 1 are generally 
not required to sample their workers' exposures to silica and are 
presumed to be in compliance with OSHA's standard.
    MSHA did not propose adopting specified exposure control methods 
for task-based work practices, similar to OSHA's Table 1. However, in 
the proposal, MSHA sought comments on specific tasks and exposure 
control methods appropriate for a Table 1 approach for the mining 
industry that would also adequately protect miners from risk of 
exposure to respirable crystalline silica.
    MSHA has decided not to include a Table 1 approach for the mining 
industry in the final rule. After considering input from stakeholders 
on specific tasks and exposure control methods suitable for a Table 1 
approach, MSHA determined that such an approach would not provide the 
necessary protection for miners against overexposure to respirable 
crystalline silica under all mining conditions. The Agency has 
concluded that because of the changing nature of the mining 
environment, exposure monitoring is essential to ensure that controls 
are functioning effectively, properly maintained, and adjusted as 
necessary to ensure compliance.
    Under the final rule, mine operators are required to implement 
feasible engineering controls, and administrative controls, when 
necessary, to maintain each miner's exposure below the PEL.

[[Page 28304]]

Operators are required to conduct exposure monitoring (sampling) in 
accordance with Sec.  60.12 to verify that the implemented controls 
effectively protect miners and ensure compliance with the final rule. 
Compliance with the PEL and corrective actions after overexposures is 
required. This final rule does not allow the use of respiratory 
protection to achieve compliance.
    Commenters from an industrial hygiene association and labor 
organizations, supported MSHA's decision not to include a Table 1 
approach for mining activities (Document ID 1351; 1398; 1449). The UMWA 
stated that this approach is not necessary since mine operators already 
have access to proper dust control systems and MSHA-approved 
ventilation plans (Document ID 1398). This commenter also noted that, 
because mining conditions are constantly changing, it would be 
incorrect to assume that operators using a Table 1 approach to control 
respirable crystalline silica exposure would always be in compliance. 
Two commenters (a professional association and a labor union) stated 
that the Table 1 approach would be neither protective nor feasible in 
the mining context, while one of those commenters stated that delaying 
the final rule to develop a Table 1 approach will create more harm for 
workers (Document ID 1351; 1398).
    MSHA agrees that due to constantly changing mining conditions, 
OSHA's Table 1 is not the most effective approach for protecting 
miners' health. A fundamental aspect of mining is that the mine 
environment is dynamic, resulting in varying exposures to respirable 
crystalline silica for miners. Silica exposures can fluctuate based on 
the amount of silica present in rock, which depends on the geological 
composition of the rock. Miners engaged in tasks that generate dust 
from this rock material may face elevated exposure levels. For example, 
activities that involve cutting, grinding, drilling, or crushing rock 
with higher-silica levels can generate dust with high silica content. 
In addition, mining operations are diverse, involving different types 
of mining, each with various mining processes. Each process involves 
specific equipment and methods tailored to the unique characteristics 
of the material being mined.
    Many commenters, including trade associations, mining related 
businesses, a labor union, and a MNM operator urged MSHA to include a 
provision like Table 1 in the final rule, with Portland Cement 
Association, NSSGA, and CertainTeed, LLC submitting example tables for 
MSHA to consider (Document ID 1407; 1408; 1424; 1441; 1448; 1404; 1409; 
1429; 1442; 1417; 1431; 1423). SSC noted that certain tasks, processes, 
and environments are at least somewhat similar or common across many 
MNM mines and may be characterized by the extent to which they may 
release respirable crystalline silica, mechanisms for doing so, and 
effective exposure controls (Document ID 1432). This commenter also 
stated that a Table 1 approach would provide mine operators with a 
choice between using their own controls and sampling to evaluate 
effectiveness (and compliance with the standard) or using the controls 
listed in the table. SSC noted that a clear list of controls required 
for each type of task, exposure, or process would simplify compliance 
and enforcement. SSC further noted that if a mine operator relied on 
the table and implemented or used all the engineering and 
administrative controls in the table, they would know that, in so 
doing, they would achieve compliance.
    MSHA has determined that reliance on a task-based approach would 
not address all mining tasks and situations that could result in 
respirable crystalline silica exposures, leaving miners without 
adequate protection. In addition, a task-based approach may not address 
cumulative exposures over a shift for miners who perform multiple tasks 
that generate respirable silica during a single shift. MSHA has 
determined that because mining involves a wide range of activities, 
each with its own potential for different dust generating sources and 
potential silica exposure, a task-based approach does not protect 
miners, especially those miners who perform multiple tasks involving 
silica exposures during a single shift.
    MSHA agrees with commenters that there are many job positions in 
the mining industry that have similar exposure risks. However, as one 
commenter testified, miners may work at multiple job positions or tasks 
throughout the shift or a workweek. This commenter noted that a miner 
may work as a laborer, crusher operator, or a loader operator in a 
single shift. Another commenter acknowledged that it would be difficult 
for a Table 1 approach to work because of the various tasks a miner 
performs (this commenter referenced a discussion on this topic between 
a mine operator and the Agency at the Denver, Colorado public hearing). 
MSHA's data indicates that a significant number of miners are 
classified as laborers, mobile workers, and utility workers. 
Approximately 31 percent of the MNM miners are mobile workers and 
approximately 39 percent of coal miners are laborers, utility workers 
and other workers who do not have specific job categories. These are 
job positions that perform different work activities during a shift. 
MSHA has determined that OSHA's Table 1 would be difficult to implement 
for most mines, especially mines that employ laborers, mobile workers, 
and utility workers.
    The Portland Cement Association and NSSGA stated that OSHA's 2019 
RFI, which assessed the effectiveness of Table 1, demonstrated that it 
was effective in lowering exposures and encouraged the adoption of 
engineering controls (Document ID 1407; 1448). However, AIHA explained 
that research indicates that worker exposure in the construction 
industry can exceed the OSHA PEL of 50 [mu]g/m\3\ even with Table 1 
controls in place (Document ID 1351).
    Portland Cement Association recommended that MSHA should adopt an 
OSHA Table 1 approach that encourages mine operators to install 
engineering controls and remove the operator's obligation to assess 
exposures in work environments where individual miner's respirable 
crystalline silica exposures are controlled by engineered devices to 
ensure compliance with the action level and the PEL (Document ID 1407). 
Under OSHA's approach, prescribed engineering controls and work 
practice methods, along with respiratory protection, are assumed to be 
sufficiently effective in reducing miners' exposures; exposure 
monitoring to ensure compliance with the PEL is not required. MSHA, 
however, has determined that exposure monitoring is critical in 
safeguarding miners' health. It provides the quantitative data needed 
to assess the effectiveness of engineering controls and is essential to 
ensuring that controls remain effective at all times. This is 
consistent with NIOSH's recommendation to OSHA during its rulemaking 
that Table 1 should not replace sampling requirements for the 
construction industry because even fully implementing the control 
methods and respiratory protection described in OSHA's Table 1 would 
not ensure compliance with the PEL. In addition, MSHA, in this final 
rule, does not allow respiratory protection as a means to achieve 
compliance.
    OSHA's Table 1 approach relies on respiratory protection when 
engineering and administrative controls are not sufficient to limit 
exposures. Respiratory protection is used for compliance when control 
methods cannot reduce exposures below the PEL. MSHA has determined that 
existing engineering controls are the most

[[Page 28305]]

effective way to protect miners from exposures to respirable 
crystalline silica. Engineering controls, when properly designed, 
implemented, and maintained, can reduce the concentration of respirable 
crystalline silica and protect miners from overexposures. Well designed 
and maintained controls can eliminate or minimize respirable silica 
dust at the source, preventing dispersion of the silica dust into the 
workplace. Respiratory protection, however, has limitations and is not 
as reliable as engineering controls in reducing miners' exposures to 
respirable crystalline silica. MSHA has determined that reliance on 
respiratory protection would risk miners' exposure to silica and 
undermine the Agency's mandate to address respiratory hazards at the 
source, providing the highest level of health protection for miners.
    The mining industry encompasses a wide range of processes and 
equipment due to the diversity of mined commodities. However, as 
commenters noted, processes and equipment are tailored to the type of 
material mined. SSC noted that certain tasks, processes, and 
environments are at least somewhat similar or common across many MNM 
mines and may be characterized by the extent to which they may release 
respirable crystalline silica, mechanisms for doing so, and effective 
exposure controls (Document ID 1432). IME recommended that MSHA adopt a 
Table 1 approach for rock drilling operations that use a dust 
collection system around the drill bit and the use of low-flow water 
spray to wet the dust discharged from the dust collector (Document ID 
1404). This commenter also noted that all drill rigs used by the 
explosives industry have fully enclosed cabs to isolate operators from 
dusty conditions. EMA suggested that a Table 1 approach could include 
processes with consistent/predicable dust generation characteristics, 
such as mobile equipment cabs, control rooms with proper ventilation 
and seals on doors and windows, utility vehicles, handheld power tools 
such as jackhammers, and tasks performed in potentially high exposure 
areas, such as crushing or bagging (Document ID 1442). This commenter 
submitted that many engineering and administrative controls or work 
practices can be gleaned from NIOSH's updated Dust Control Handbook for 
Industrial Minerals Mining and Processing, Second Edition. The 
commenter further noted that the NIOSH Dust Control Handbook is an 
excellent resource and could reduce the amount of research necessary to 
create a usable Table 1.
    MSHA has determined that these controls cannot be relied on without 
independent assessment (exposure monitoring) to ensure that they are 
effective and continue to protect miners. For example, MSHA has found 
that equipment operators who are working in enclosed cabs report some 
of the highest exposures. These miners are exposed to high silica 
exposures because the enclosures are not properly maintained. Under a 
Table 1 approach, equipment operators would be presumed to be protected 
by enclosed cabs and not exposed to silica above the PEL.
    A fundamental feature of mining is that the mine environment 
constantly changes. MSHA has concluded that miners' exposures to 
respirable crystalline silica vary with much greater frequency than in 
general industry, construction, or maritime settings. A feasible 
engineering control implemented in a mine (including a mill) cutting 
into or processing lower-quartz-containing rock might not be 
appropriate for a mine cutting into rock with a higher percentage of 
quartz or using a different mining process or modified equipment.
    In addition, certain mining environments must take into account 
bystander exposure. For example, in underground mining environments, 
the ventilation is often in a series configuration, where the exhaust 
of one miner's controls could be the intake for other miners downwind. 
This results in the upwind engineering controls having an effect on all 
of the miners that are downwind. In contrast, OSHA's construction and 
general industry worksites have controls that can be exhausted to the 
outside atmosphere and will not affect other workers nearby.
    MSHA has determined that, in the context of mining, Table 1 
controls cannot be relied on without independent assessment (exposure 
monitoring) to ensure that they are effective, maintained, and continue 
to protect miners. MSHA's enforcement experience and data show that 
some of the highest respirable crystalline exposures result from mine 
operators not maintaining engineering controls. Poor maintenance of 
engineering controls, without exposure monitoring, can result in miners 
working above the PEL for extended periods, jeopardizing their health. 
For example, a miner working at a surface MNM mine was exposed to 192 
[mu]g/m\3\ of respirable crystalline silica. The miner was working in a 
control booth, but the control booth ventilation system was not 
maintained, and the door seals were defective and leaking. A second 
example involved a bulldozer operator working at a surface coal mine 
who was exposed to 109 [mu]g/m\3\ of respirable crystalline silica. The 
cab's door seals were crushed, and the cab filter was broken. A third 
example involved a miner operating a front-end loader at surface MNM 
mine, who was exposed to 213 [mu]g/m\3\ of respirable crystalline 
silica. The cab air-conditioner was not functioning. These examples 
illustrate the importance of regular exposure monitoring to alert mine 
operators to take necessary corrective actions to repair and maintain 
equipment to protect miners' health. The exposure monitoring 
requirements in the final rule provide mine operators, miners, and MSHA 
with information necessary to verify that miners' exposures remain 
below the PEL at all times, therefore protecting miners' health. Also, 
the final rule does not allow respiratory protection to achieve 
compliance.
    In addition, geological formations and quantities of quartz are not 
always predictable and the Agency believes that controlling exposures 
to respirable crystalline silica to below the PEL through sampling is 
the best way to protect miners' health. Accordingly, MSHA has concluded 
that because of the dynamic, constantly changing nature of the mining 
environment, exposure monitoring is essential to ensure that controls 
are functioning effectively, properly maintained, and adjusted as 
necessary to ensure compliance.
    In response to MSHA's solicitation for stakeholder input on a Table 
1 approach, commenters representing the stone, sand, and gravel 
industries provided information and data on an alternative Table 1 for 
MSHA's consideration. The NSSGA provided a proposed Table 1 that 
grouped various equipment operator positions by equipment and tasks 
(including a description of operation and tasks performed) and 
identified engineering and work practice control methods for the 
equipment and tasks (Document ID 1448). The commenter noted that this 
Table 1 is protective of workers and does not give operators an ``out'' 
when a worker performs a task that is listed on the table. The 
commenter further noted that under their proposed Table 1, the operator 
must ensure all engineering and work practice control methods are done 
to comply with the table and not engage in exposure monitoring. The 
commenter stated their Table 1 approach works because sampling has been 
done that demonstrates these

[[Page 28306]]

controls work and keep workers below the action level.
    The Portland Cement Association provided respirable crystalline 
silica exposure data by job classification and an alternative Table 1 
that identified equipment/tasks, engineering and work practice 
controls, and required respiratory protection and assigned protection 
factor (Document ID 1407). As the commenter noted, the table shows 
control measures in widespread use in the cement manufacturing 
industry, which the commenter believes some MNM mine operators use at 
their operations.
    MSHA considered commenters' Table 1 approaches. Like OSHA, the 
commenters' alternative approaches provide specific guidance on how to 
control work exposures to respirable crystalline silica for specific 
tasks. The suggested Table 1 approaches list the equipment/task and 
identify the similarly exposed positions and appropriate engineering 
and work practice control methods.
    MSHA has determined that because mining involves a wide range of 
activities, from drilling and blasting to crushing and processing 
materials, each with its own potential for different dust generating 
sources and potential silica exposure, as well as differing silica-
bearing strata, a task-based approach does not protect miners, 
especially those miners who perform multiple tasks involving silica 
exposures during a single shift. A Table 1 approach can be effective 
for construction activities. However, Table 1's applicability to mining 
and milling operations is limited due to the complexity, variability, 
and unique challenges inherent in mining and milling operations. 
Activities in these operations are highly variable, due to the types of 
ores, minerals, and materials processed. Mining and milling operations 
run continuously, unlike some construction activities which may not be 
continuous or steady. Continuous operations require different control 
measures and monitoring strategies to address sustained miner exposures 
over an extended period. In addition, MSHA has determined that 
specified control methods may not provide a continued and verifiable 
level of protection to miners. Exposure monitoring is essential to 
ensure that the controls remain effective at all times. Further, as 
stated earlier, this final rule does not allow respiratory protection 
as a means to achieve compliance.
    MSHA also received comments stating that a Table 1 approach would 
benefit intermittent and seasonal mining operations. The NSSGA stated 
that these mine operators do not have as much time to conduct sampling 
and would benefit from a Table 1 approach (Document ID 1448). 
Similarly, North America's Building Trades Unions (NABTU) noted that 
being able to implement controls according to job function, without 
having to take air samples, would help portable mines and construction 
contractors to achieve compliance in dynamic work environments 
(Document ID 1414). CISC explicitly requested that MSHA conduct a final 
review and produce a report for comment analyzing silica exposure from 
all jobs associated with quarrying operations, and either exclude them 
from the proposed rule or create a Table 1 approach, indicating that 
most jobs in surface quarrying operations are incapable of exceeding 
the proposed PEL (Document ID 1430). As noted above, MSHA has 
determined that, due to the diverse range of activities involved in 
mining, and constantly changing mining conditions--including drilling, 
blasting, crushing, and material processing, each with its unique 
potential for silica exposure--a Table 1 approach does not adequately 
protect miners. This is particularly true for miners who are engaged in 
multiple tasks involving silica exposure within a single shift. MSHA 
has also concluded that control methods must be assessed to ensure they 
provide sufficient protection; therefore, exposure monitoring is 
essential to verify the ongoing effectiveness of implemented controls.
    The Agency also received comments about alternative approaches to 
Table 1-type guidance. NSSGA stated that jobs where workers are in 
enclosed cabs, booths, and buildings have consensus standards and 
should be in Table 1 (Document ID 1448). Some commenters, including 
AIHA and IEEE, suggested that MSHA incorporate or recommend relevant 
control standards designed to protect workers performing certain tasks, 
such as ISO 23875: 2021, to provide operators with more tools to 
protect workers while continuing mandated exposure monitoring (Document 
ID 1351; 1377). Draeger, Inc. stated that MSHA should consider 
incorporating Table 1 content into a silica guidance document (Document 
ID 1409). NVMA suggested that MSHA should allow operators to develop 
their own Table 1 as part of their dust protection plan but cautioned 
that MSHA should not be permitted to cite the development of an 
internal tool unless the PEL is exceeded, and a respirator is not used 
(Document ID 1441). Draeger, Inc. also acknowledged that creating a 
Table 1 approach would be a significant effort and suggested that MSHA 
initially consider high-risk tasks in developing the control methods 
(Document ID 1409). EMA recommended that MSHA should consult the Dust 
Control Handbook for Industrial Minerals Mining and Processing, Second 
Edition, to reduce the amount of research necessary to create a Table 1 
approach (Document ID 1442).
    MSHA acknowledges that consensus standards can assist mine 
operators in the development and selection of proper engineering 
controls for their mine sites and supports the use of consensus 
standards in the design of operator enclosures for hazardous 
environments. MSHA also recognizes the value of providing guidance on 
engineering and work practice control methods for similar exposure 
groups to ensure compliance with the final rule. The Agency supports 
and encourages the use of NIOSH's Dust Handbook by mine operators to 
determine feasible and appropriate engineering controls for their mine 
sites. MSHA will work with operators and miners to develop and 
implement effective controls, including necessary exposure monitoring. 
MSHA encourages mine operators to be proactive in their approach to 
protecting miners from silica exposures. MSHA encourages operators to 
develop dust control plans or other engineering tools in their 
operations. MSHA also commits to developing guidance that includes 
information on consensus standards related to control methods. MSHA 
will collaborate with stakeholders, including industry and labor, as 
well as NIOSH, to help mine operators and miners in implementing 
appropriate control methods. MSHA will also provide education and 
training to mine operators and miners covering all aspects of the final 
rule.
5. Medical Removal/Transfer
    MSHA does not include a medical removal/transfer option for MNM 
miners with evidence of silica-related disease in the final rule. MSHA 
intends to consider this issue in a future rulemaking.
    In the proposed rule, MSHA solicited comments on whether the final 
rule should include a medical removal/transfer option for MNM miners 
who have developed evidence of silica-related disease that is 
equivalent to the transfer rights and exposure monitoring provided to 
coal miners in 30 CFR part 90 (part 90). Under part 90, any coal miner 
who has evidence of the development of pneumoconiosis based on a chest 
X-ray or other medical examination has the option to work in

[[Page 28307]]

an area of the mine where the average concentration of respirable dust 
in the mine atmosphere during each shift to which that miner is exposed 
is continuously maintained at or below the standard for Part 90 miners. 
Part 90 miners are ``entitled to retention of pay rate, future actual 
wage increases, and future work assignment, shift and respirable dust 
protection.'' 30 CFR 90.3(b).
    MSHA received comments from labor organizations, mining trade 
associations, black lung clinics, a federal elected official, an 
industrial hygiene professional association, an advocacy organization, 
a medical professional association, and an individual generally 
supporting medical removal/transfer rights. These commenters urged MSHA 
to include the provisions of part 90 in the rule and stated these 
protections should apply for a medically confirmed diagnosis of 
silicosis for any miner (Document ID 1351; 1398; 1416; 1418; 1421; 
1424; 1439; 1441; 1449). Many of these commenters, as well as the Black 
Lung Clinics, the USW, and an individual stated that MNM miners should 
be provided similar medical removal/transfer rights as coal miners 
(Document ID 1410; 1447; 1437). The UMWA, Black Lung Clinics, and AFL-
CIO noted that a medical removal/transfer program helps address the 
barriers related to fear of retaliation and income loss workers face 
when choosing to participate in medical surveillance (Document ID 1398; 
1410; 1449).
    After reviewing the comments and based on its experience with part 
90 for coal miners, MSHA agrees that medical removal/transfer would 
enhance health protections for MNM miners who choose to exercise their 
rights; however, the Agency has determined that this would be more 
appropriately addressed in a future rulemaking. MSHA believes that the 
NIOSH-established reporting system referenced in the final rule needs 
to be developed and implemented before implementing medical removal/
transfer requirements. For example, under part 90, NIOSH administers 
medical surveillance and notifies mine operators when a miner exercises 
their part 90 rights. Under this final rule, MNM medical surveillance 
is administered independent of NIOSH, and there are many more MNM 
miners than coal miners. Because of these differences, the Agency 
concluded that medical removal/transfer would benefit from additional 
notice and comment on a number of decision points, including protecting 
miners' privacy, adequacy of forms for notification, timing of 
benefits, what area of the mine the miner would be transferred to, 
whether NIOSH must make the determination, and consistent ILO 
classification. Further, MSHA agrees with the many commenters that 
urged the Agency to issue this final rule without delay.
    MSHA also clarifies that, under final Sec.  60.14(b), a mine 
operator must, upon receiving written notification from a PLHCP, 
facilitate the temporary transfer of an affected miner who cannot wear 
a respirator to a different area or occupation within the same mine 
where respiratory protection is not necessary. The final rule requires 
that transferred miners continue to receive compensation at no less 
than the regular rate of pay in the occupation that they held 
immediately prior to the transfer.
6. Compliance Assistance
    MSHA will provide compliance assistance to the mining community 
(including industry and labor) after publication of the final rule. 
This assistance will include guidance to assist mine operators in 
developing and implementing appropriate controls; outreach seminars 
(onsite and virtual, dates and locations will be posted on MSHA's 
website); dust control workshops held at the National Mine Health and 
Safety Academy; support from the Educational Field and Small Mine 
Services staff; support from MSHA's Technical Support staff; silica 
training and best practice materials; and information on MSHA's 
enforcement efforts.
    Additionally, MSHA will continue its Silica Enforcement Initiative 
by evaluating all sampling data and enforcement actions and providing 
compliance assistance on specific engineering controls. MSHA will 
continue to maintain a team of experts in regulatory compliance and 
respirable dust control to conduct compliance assistance visits. These 
visits will evaluate the conditions, mining practices, and controls 
that lead to silica dust overexposures. MSHA will discuss its results 
with mine operators and miners and make recommendations as a part of 
the Agency's compliance assistance activities.
    As a part of its ongoing alliance agreements, MSHA will discuss 
issues and questions in regular alliance safety and health meetings. 
MSHA will continue to work with NIOSH in the development and delivery 
of compliance assistance materials. Compliance assistance materials 
will be posted on MSHA's and NIOSH's website, some of which may be 
reposted to the MSHA app. NIOSH's Dust Control Handbook is a useful 
tool for mine operators to determine feasible and appropriate 
engineering controls for their mine sites. MSHA encourages mine 
operators to use this resource. MSHA will work with mine operators and 
miners to develop and implement effective controls, including 
evaluating exposure monitoring results. MSHA encourages mine operators 
to be proactive in their approach to protecting miners from silica 
exposures and to develop dust control plans or other engineering tools 
in their operations. MSHA also commits to developing guidance that 
includes information on consensus standards related to control methods. 
MSHA will also provide education and training to mine operators and 
miners covering all aspects of the final rule.

B. Section-by-Section Analysis

    Part 60 of the final rule establishes uniform mandatory health 
standards for exposure to respirable crystalline silica in MNM and coal 
mines. Part 60 includes 10 sections: Scope and compliance dates; 
Definitions; Permissible exposure limit (PEL); Methods of compliance; 
Exposure monitoring; Corrective actions; Respiratory protection; 
Medical surveillance for metal and nonmetal mines; Recordkeeping 
requirements; and Severability. For each section below, MSHA discusses 
the requirements of the final rule and addresses the public comments 
received in response to the July 2023 proposed rule.
1. Section 60.1--Scope; Compliance Dates
    The final rule establishes requirements for the scope of the rule 
and the compliance dates in Sec.  60.1. Section 60.1 paragraph (a) 
identifies the scope of the final rule, and the language is unchanged 
from the proposal. In a change from the proposal, paragraph (b) 
identifies the separate compliance dates for coal mine operators in 
paragraph (b)(1) and for metal and nonmetal mine operators in paragraph 
(b)(2). Paragraph (b)(1) establishes a compliance date for coal mine 
operators of 12 months after publication of the final rule. Paragraph 
(b)(2) establishes a compliance date for metal and nonmetal mine 
operators of 24 months after publication of the final rule. Below is a 
detailed discussion of the comments received on this section and 
modifications made in response to the comments.
a. Scope
    MSHA received many comments regarding the scope of the rule. Some 
commenters, including the AIHA, ACOEM, APHA, expressed support for

[[Page 28308]]

the proposed rule's unified approach to regulating respirable 
crystalline silica exposures at both MNM and coal mines, as well as at 
both underground and surface mines (Document ID 1351; 1405; 1416; 
1412). Several other commenters, including labor organizations, 
advocacy organizations, mining trade associations, and MNM operators, 
recommended separate approaches to regulating MNM and coal mines; those 
commenters differed on which mines should or should not be regulated 
and why (Document ID 1398; 1431; 1445; 1448; 1411; 1415; 1427; 1440; 
1452; 1424; 1430; 1441; 1443; 1429; 1392; 1383). Several commenters, 
including mining-related businesses and MNM operators, stated that the 
proposed rule should not apply to MNM mines (Document ID 1392; 1383; 
1411; 1415; 1427). The reasons for the commenters' position included: 
past precedent of separate rules (e.g., Document ID 1448; 1440; 1445), 
a need for consistency with OSHA's silica standard (e.g., Document ID 
1392; 1383; 1411; 1415; 1427; 1431), lower incidence of silicosis among 
MNM miners (e.g., Document ID 1431; 1413; 1448; 1456), and higher 
compliance costs under the unified approach (Document ID 1392; 1411; 
1415; 1427). The Pennsylvania Coal Alliance questioned the need for the 
rule to apply to the coal industry, stating that there had been no 
marked increase in compensation claims for pneumoconiosis or silicosis 
in coal mines (Document ID 1378). Other commenters, including a black 
lung clinic, a medical professional association, advocacy 
organizations, and a labor union, noted the risks that silica exposure 
poses to all miners (Document ID 1418; 1421; 1445; 1425; 1447). The 
Miners Clinic of Colorado at National Jewish Health observed that 
information about silicosis disease rates among MNM miners is less 
readily available in part due to a lack of medical surveillance 
(Document ID 1418). However, even with less information on silicosis 
disease rates than in coal, this commenter relayed their observations 
of substantial silicosis rates in MNM miners.
    MSHA continues to believe that a unified approach to controlling 
respirable crystalline silica provides the greatest level of health 
protection for MNM and coal miners. The purpose of this final rule is 
to reduce respirable crystalline silica-related occupational diseases 
in miners and to improve respiratory protection against airborne 
contaminants. Based on MSHA's review of the adverse health effects 
related to respirable crystalline silica--a known carcinogen--MSHA 
concludes that the health risks threaten all miners exposed to 
respirable crystalline silica. It is important that the mandatory 
health standards for MNM and coal miners be consistent to ensure that 
all miners are equally protected from exposure. Selected surveillance 
data for both silicosis cases and deaths are reported in the standalone 
Health Effects document and in the preamble in Section V. Health 
Effects Summary. Additionally, further discussion of risk related to 
silica exposure is located in the standalone FRA document.
    While MSHA acknowledges that MNM and coal mines have been regulated 
separately in the past, there is precedent for a unified approach. For 
example, MSHA's health standard for occupational noise covers both MNM 
and coal mines, as discussed in ``Evaluating hearing loss risks in the 
mining industry through MSHA citations'' (Sun and Azman, 2018). Like 
respirable crystalline silica, occupational noise is a hazard for all 
miners. MSHA's survey and enforcement data indicate that since the 
occupational noise rule became effective in September of 2000, there 
has been a drastic decrease in the rate of overexposures at both MNM 
and coal mines. Because the hazards and control methods of respirable 
crystalline silica are common to both coal and MNM, MSHA believes a 
unified standard will offer miners consistent improvement of working 
conditions in both sectors.
    As addressed in the standalone Health Effects document, MSHA has 
reviewed studies supporting increased risk of adverse health effects 
for miners working in both coal and MNM mines. After decades of 
declining prevalence of pneumoconiosis among underground coal miners in 
the U.S., prevalence, including more advanced forms of disease, has 
increased since the late 1990s (Laney and Weissman, 2012; Blackley et 
al., 2014a, 2018a; Hall et al., 2019b).
    MSHA does not agree with the assertion that silicosis or other 
diseases linked to respirable crystalline silica are not risks for MNM 
miners. MSHA reviewed a wide range of studies that demonstrated disease 
risks among miners occupationally exposed to respirable crystalline 
silica. These studies were not limited to coal miners and covered 
occupations relevant to MNM mining such as sandblasters (Hughes et al., 
1982; Abraham and Wiesenfeld, 1997), industrial sand workers (Vacek et 
al., 2019), hard rock miners (Verma et al., 1982, 2008), gold miners 
(Carneiro et al., 2006a; Tse et al., 2007b), metal miners (Hessel et 
al., 1988; Hnizdo and Sluis-Cremer, 1993; Nelson, 2013), and nonmetal 
miners such as silica plant and ground silica mill workers, whetstone 
cutters, and silica flour packers (Mohebbi and Zubeyri, 2007; NIOSH, 
2000a,b; Ogawa et al., 2003a). Of the MNM exposure samples MSHA 
collected over the 2005-2019 period, 17.7 percent exceed the new PEL of 
50 [mu]g/m\3\, and 6.1 percent exceed the current PEL of 100 [mu]g/
m\3\. Further discussion on this analysis is presented in the 
standalone FRA document.
    This rule will strengthen miners' health protections by reducing 
exposures to respirable crystalline silica, which is the root cause of 
silica-related disease. MSHA believes that this uniform approach 
provides a more protective, coherent, logical, and predictable standard 
for miners and mine operators. Unlike the existing standards, this 
final rule establishes a single, uniform PEL and action level, and 
eliminates any need for conversion based on percent respirable 
crystalline silica and any variations in calculation for different 
silica polymorphs. The final uniform PEL will provide all miners with a 
consistent level of protection that is similar to the protection 
provided to workers in industries covered by OSHA's silica standards, 
and consistent with the recommendations of NIOSH.
b. Applicability to Contractors, Portable Mines, and Sorptive Minerals 
Industry
    Several commenters requested clarification of applicability or 
exemptions to specific sectors of the mining industry: mining 
contractors, portable mines, and the sorptive minerals sector.
Contractors
    Some commenters from industry trade associations and mining trade 
associations requested that MSHA clarify the rule's applicability to 
mining contractors in the final rule (Document ID 1422; 1433; 1424; 
1428; 1378). Consistent with the Mine Act, MSHA's existing standards, 
and the Agency's longstanding policy, independent contractors engaging 
in mining activities, including construction, maintenance, and 
drilling, are required to comply with the requirements in this final 
rule. See 30 U.S.C. 802(d) (defining ``operator'' to include ``any 
independent contractor performing services or construction'' at a mine) 
and Sec.  802(g) (defining ``miner'' as ``any individual working in a 
coal or other mine''). MSHA has a long history and practice of 
enforcing its standards and regulations for mine operators and

[[Page 28309]]

independent contractors designated under part 45 of 30 CFR. The Agency 
believes that the industry is familiar with and understands this 
history and practice. Based on MSHA's experience and practice, and 
depending upon the activities that they perform for production 
operators, MSHA expects that some part 45 independent contractors will 
comply with the requirements of this final rule, as it relates to their 
miners. For example, MSHA expects that drilling and blasting 
contractors, who perform services at different mines, generally 
separate from production activities, will comply with the requirements 
of the final rule. For other part 45 independent contractors, MSHA 
anticipates that the production operator may comply with the 
requirements of this final rule for their miners, depending upon the 
types of services provided. For example, MSHA expects that production 
operators will generally comply with the requirements of this final 
rule for independent contractors that perform hauling services for 
mines. This final rule provides improved health protections for miners 
of both part 45 independent contractors and production operators. As 
with the implementation of any new MSHA standard, the Agency expects 
that production operators and part 45 independent contractors will 
communicate and coordinate with each other, as appropriate, to comply 
with the final rule and ensure that miners' safety and health are 
protected.
Portable Mines
    Some commenters (MNM operators and a mining-related business) 
requested that MSHA exempt portable mine operations from exposure 
monitoring (Document ID 1392; 1415; 1427; 1435; 1436). The mining-
related business commented that an exemption should be granted for 
portable mines that are shut down for more than 3 months out of the 
year or operate in a pit for less than 30 days before moving (Document 
ID 1392). Several portable mine operators, including B & B Roads, Inc., 
stated that rock crushing jobs are typically completed within 4 to 10 
days, at which point the portable mine moves to another job location, 
which could be between 30 to 200 miles away (Document ID 1427; 1436). 
These commenters specifically requested exemptions for sites that they 
do not own, stating that sampling data would not be applicable if done 
at pits where they do not conduct operations regularly. However, these 
commenters expressed that they were not asking for exemptions to pits 
where they regularly conduct operations or to locations they control.
    MSHA reviewed the comments and determined that because of MSHA's 
clear mandate to protect the health of all miners, the final rule does 
not exempt portable mines. Under existing MNM standards for airborne 
contaminants, portable operations are not exempt from any regulatory 
requirements or any other health standards. This final rule, like 
existing standards, requires portable mine operators to protect their 
miners from overexposure to respirable crystalline silica and other 
airborne contaminants, and to monitor miners' exposures to airborne 
contaminants, including silica. Portable mine operations often involve 
crushing, which can generate substantial amounts of dust, and they 
handle a variety of commodities generating varying amounts of 
respirable crystalline silica depending on the geological features of 
the pit.
    The final rule requires that all mine operators, including portable 
mine operators, conduct exposure monitoring in accordance with Sec.  
60.12, including first-time sampling. With respect to portable mine 
operators, MSHA has taken into consideration that these mines are 
unique and may move frequently. However, the final rule does not exempt 
portable mine operators because miners must be protected at all times, 
and the methods of compliance, sampling and evaluation provisions are 
necessary to protect miners.
    Sampling ensures engineering controls put in place by mine 
operators are effective in protecting miners. If the portable mine 
operator anticipates being at the site for at least three months, MSHA 
expects the portable mine operator to conduct the second-time sampling 
at that site within the three-month timeframe under Sec.  60.12(a)(2). 
If the portable mine operator moves to a different site before 
conducting its second-time sampling within three-months, the operator 
is required to conduct the second-time sample at the next site. If 
either operator or MSHA samples are at or above the action level and at 
or below the PEL, portable operators must sample every three months 
under Sec.  60.12(a)(3). Similarly, if the most recent sampling was 
above the PEL, the portable mine operator must take immediate 
corrective actions, immediately report the overexposure to MSHA, ensure 
provided respirators are worn appropriately by affected miners before 
the start of the next work shift, and resample, regardless of whether 
the portable mine has moved to a different site by the time the 
sampling results are received. Under the final rule, at least every 6 
months or if there are any changes in processes, production, equipment, 
or geological conditions, mine operators are required to conduct a 
qualitative evaluation. Protecting miners' health requires monitoring 
and controlling levels of respirable crystalline silica, and, 
consistent with the Mine Act, miners at portable mines must be afforded 
the same health protections and informational awareness of their 
exposures as all other miners.
    If the results of the evaluation reveal that their miners may be 
reasonably exposed to respirable crystalline silica at or above the 
action level but at or below the PEL, the sampling provisions of the 
final rule apply. Also, if sampling indicates levels above the PEL, 
under the final rule, portable mine operators must take immediate 
corrective actions, resample, and record these actions.
    MSHA provides two examples that illustrate how and why the final 
rule will affect portable mine operators. In example 1, the portable 
mine operator conducts first-time sampling on mine site A and the 
sample result is below 25 [mu]g/m\3\. One month later, the portable 
mine operator moves to mine site B. The operator performs a qualitative 
evaluation, which the operator determines does not trigger post-
evaluation sampling. Within two months (three months from the date of 
the first-time sample), the portable mine operator must take a second 
sample. This sample result is also under 25 [mu]g/m\3\. Under the final 
rule, this portable mine operator can discontinue sampling. The 
portable mine operator then moves to mine site C. The portable mine 
operator must conduct a qualitative evaluation and, depending on the 
results of the evaluation, may need to perform sampling.
    In example 2, the portable mine operator is located on mine site X. 
The portable mine operator conducts a qualitative evaluation and 
determines that miners' exposures may reasonably be at or above the 
action level, triggering sampling. The portable mine operator conducts 
sampling, and the results are above the PEL. The mine operator takes 
immediate corrective actions, immediately reports the overexposure to 
MSHA, ensures provided respirators are worn appropriately by affected 
miners before the start of the next work shift, and resamples. The 
operator then moves to mine site Y before corrective actions sampling 
results are received. Depending on the results of the corrective 
actions sampling from mine site X, the portable mine operator must 
conduct either above-action-level sampling or corrective actions 
sampling

[[Page 28310]]

at mine site Y. MSHA expects that all corrective actions, including any 
new or improved engineering controls, will remain in place at mine site 
Y. Additionally, at mine site Y, the operator must perform another 
qualitative evaluation at the new mine site. Each time the operator 
moves to a new site, it must perform a new qualitative evaluation.
    These examples illustrate that when sampling is required at one 
portable mine site, the requirement continues when the portable mine 
moves to a new mine site. Sampling across different portable mine sites 
is needed to determine whether the engineering controls applied to the 
portable mine (for example, dust collection or water spray) are 
effective to keep miners healthy. Periodic evaluations will also be 
critical for mines that move frequently and encounter different 
conditions that expose miners to respirable crystalline silica. These 
evaluations and any related samplings will allow operators to verify 
that adequate engineering controls are effective and are maintained 
properly to protect miners as they move to different worksites, 
regardless of mining location or commodity mined or milled.
    MSHA encourages portable mine operators to work with their District 
Managers to develop an appropriate compliance approach that protects 
miners' health. MSHA will provide compliance assistance to portable 
mine operators.
Sorptive Minerals
    The applicability of the rule to one specific industry within MNM--
the sorptive minerals industry--was the subject of several comments 
from SMI, EMA, and Vanderbilt Minerals, LLC (Document ID 1446; 1442; 
1419). These commenters requested that the sorptive minerals industry 
be exempted from the rule. The commenters stated that this industry 
exposes workers only to aged quartz, and that aged quartz is less toxic 
than freshly fractured quartz in other industries. After careful 
consideration, MSHA has decided not to exempt sorptive minerals mines. 
The Agency's rationale for this decision is discussed in detail above 
in Section VIII.A. General Issues.
c. Compliance Dates
    This final rule will take effect 60 days after publication in the 
Federal Register. In response to comments, MSHA is establishing two 
compliance dates for the final rule--one for MNM mine operators and the 
other for coal mine operators. MNM operators will be required to comply 
starting 24 months after publication of the final rule, whereas coal 
mine operators will be required to comply starting 12 months after 
publication of the final rule.
    MSHA received comments both in support of and against having 
compliance commence immediately when the final rule takes effect. Some 
commenters, including labor organizations, an industrial hygiene 
professional association, and an advocacy organization, supported the 
proposed effective date, citing the need for the new rule to be 
implemented as soon as possible to protect miners' health (Document ID 
1398; 1425; 1351; 1449). Appalachian Voices and the AFL-CIO stated that 
the technologies and practices necessary to reduce dust and silica 
exposure are well-known and that mine operators have had ample notice 
that this rule was forthcoming (Document ID 1425; 1449). In contrast, 
several commenters, including multiple mining trade associations and a 
mining industry organization, expressed the need for a longer 
preparation period prior to compliance (Document ID 1428; 1407; 1408; 
1442; 1441; 1448). Some commenters, including a state mining 
association, a MNM operator, and an industry trade association, 
suggested that MSHA allow more time, ranging from one to three years, 
to comply with the final rule (Document ID 1441; 1432; 1442; 1448; 
1392). Some cited reasons for allowing more time include: the two-year 
preparation period that OSHA provided for compliance with its 2016 
silica rule; the time needed for operators to plan, purchase, and 
implement engineering controls; and the challenges that the rule could 
present for MNM mine operators new to sampling and medical surveillance 
(Document ID 1407; 1419; 1424; 1428). Other commenters, including a 
professional association, industry trade associations, mining trade 
associations, and MNM operators, suggested a phased approach to 
implementation, with different compliance dates for the different 
requirements in the rule (Document ID 1377; 1407; 1413; 1428; 1424; 
1456; 1417; 1453). Examples given of past rules that had used this 
approach included: OSHA's silica rule (which became effective 90 days 
after publication, but, for example, for construction, allowed one year 
after the effective date for compliance with most of the rule 
requirements, and two years for compliance with certain laboratory 
requirements); MSHA's diesel particulate matter rule (which included 
incremental reductions in the PEL over two years); and MSHA's 2014 RCMD 
Standard (which allowed operators 18 months after the effective date to 
comply with sampling requirements and 24 months to implement the 
standards) (Document ID 1407; 1424; 1441; 1442).
    Several commenters, including three industry trade associations, a 
mining trade association, and a MNM operator, expressed concern that 
the rule would lead to excessive demand and backlogs for sampling 
devices, industrial hygienists, labs, medical facilities, and B Readers 
(Document ID 1407; 1404; 1413; 1428; 1419). The NSSGA stated that over 
80 percent of aggregate companies have fewer than 25 employees and 
therefore will likely rely on their insurance companies or industrial 
hygiene consultants for sampling, and that scheduling of sampling will 
be based on priorities outside the control of the mine operator 
(Document ID 1448). A mining trade association, industry trade 
associations, and a MNM operator also asserted that because post-
pandemic supply chain delays are continuing, and in some cases 
escalating, operators are facing long lead times for procurement of 
critical infrastructure items, including those essential for mandatory 
health and safety requirements (Document ID 1428; 1404; 1407; 1419). 
Finally, these commenters expressed concern that requiring mine 
operators to comply with the final rule 120 days after publication 
would not provide enough time for MSHA to issue guidance and for mine 
operators to digest relevant implementation and compliance guidance 
documents (Document ID 1428; 1404; 1407; 1419).
    After careful consideration, MSHA has decided to provide additional 
time for mine operators to prepare for compliance with the final rule. 
MNM mine operators must comply with the final rule by 24 months after 
publication of the final rule, while coal mine operators will have 12 
months to come into compliance with the rule (except for medical 
surveillance, which applies only to MNM mines). MSHA believes that this 
final compliance date gives coal mine operators sufficient time to plan 
and prepare for effective compliance with the new standards, while also 
ensuring that improved protections for miners from the hazards of 
respirable crystalline silica take effect as soon as practically 
possible. Unlike MNM mines, underground and surface coal mine operators 
have considerable experience with frequent sampling, and they can more 
quickly integrate the sampling requirements in this final rule into 
their existing underground mine ventilation plans and surface mine 
respirable dust control plans. In addition, coal mines already have

[[Page 28311]]

existing controls in place that control for dust; therefore, coal mine 
operators should not need as much time to maintain, repair or implement 
controls. As mentioned earlier, coal mine operators will not have to 
implement medical surveillance under this rule.
    In the case of MNM mines, MSHA has adjusted the requirements in the 
final rule to allow operators a total of 24 months after the 
publication of the final rule to comply. MSHA is allowing this longer 
period for compliance because MNM operators, particularly small mines, 
may have less experience with sampling and may also need time to 
prepare for compliance with medical surveillance. The longer period for 
compliance is generally responsive to some commenters. The Agency 
believes the longer period for compliance will provide operators 
adequate time to meet their compliance obligations under the final 
rule. MSHA believes that mine operators will use the compliance period 
to familiarize themselves with the new standard; evaluate, update, and 
enhance existing engineering controls; research, purchase, and install 
new or additional engineering controls, if necessary; arrange for 
sampling; and commence sampling. MSHA notes that the 24 months provided 
for MNM operators is the same as that provided in the OSHA rule and the 
same as MSHA provided in the 2014 RCMD Standard. MSHA believes that 
there are enough laboratories, sampling equipment, medical service 
providers, respiratory equipment, and contractor service providers for 
sampling to meet any increase in demand for equipment or services 
required by this final rule. The additional 24 months will provide MNM 
operators additional time to procure equipment and services. For a 
detailed discussion of the availability of respirators and laboratory 
and medical services necessary for compliance with the rule, see 
Section VII.A. Technological Feasibility.
    MSHA believes that these compliance periods in the final rule 
provide operators adequate time to prepare for successful 
implementation, balanced against the Agency's priority goal and 
statutory mandate to move quickly to protect miners against respirable 
crystalline silica hazards. Mine operators in both MNM and coal have 
had many years of experience with monitoring and controlling airborne 
contaminants, including respirable crystalline silica, and this 
experience should facilitate implementation of the final rule. MSHA 
data show that many mines are already meeting the respirable 
crystalline silica PEL of 50 [mu]g/m\3\ for a full-shift, calculated as 
an 8-hour TWA, using a variety of engineering controls. In addition, to 
ensure successful implementation, MSHA plans to provide compliance 
assistance to the mining industry. This assistance will include the 
development and distribution of compliance guidance materials for mine 
operators and training materials for miners, as well as technical 
assistance for small mines. Compliance assistance and training are 
discussed in more detail above in Section VIII.A. General Issues.
2. Section 60.2--Definitions
    The final rule, like the proposal, includes definitions for the 
following terms in Sec.  60.2: ``action level,'' ``respirable 
crystalline silica,'' and ``specialist.'' In a change from the 
proposal, MSHA removes the definition of ``objective data'' from the 
final rule. MSHA received multiple comments on the proposed definitions 
of action level and objective data, as discussed in more detail below. 
The Agency did not receive any comments on the proposed definitions of 
respirable crystalline silica or specialist.
a. Action Level
    The final rule, like the proposal, defines ``action level'' as ``an 
airborne concentration of respirable silica of 25 micrograms per cubic 
meter of air ([mu]g/m\3\) for a full-shift exposure, calculated as an 
8-hour time-weighted average (TWA).'' If respirable crystalline silica 
concentrations are at or above the action level but at or below the 
PEL, operators are subject to the ongoing sampling requirements 
detailed in Sec.  60.12. The action level enables mine operators to 
maintain compliance with the PEL and provide necessary protection to 
miners before overexposures occur.
    MSHA received several comments in support of and against the 
proposed adoption of an action level. Several commenters including 
labor unions, medical professional associations, and advocacy 
organizations supported the proposal to institute an action level of 25 
[mu]g/m\3\ (Document ID 1398; 1447; 1416; 1421; 1393; 1438). The UMWA 
and USW stated that the proposed action level was consistent with NIOSH 
and IARC findings and would reduce the risk of death and disease 
(Document ID 1398; 1447). Other commenters, including state mine 
organizations, mining trade associations, and MNM mine operators, did 
not support the proposed action level of 25 [mu]g/m\3\ for all mines 
(Document ID 1368; 1441; 1424; 1432; 1440; 1378; 1392; 1408; 1426). The 
commenters stated that it would not be achievable with current 
technology (Arizona Mining Association, Document ID 1368) and would not 
improve miners' health (AMI Silica LLC, Document ID 1440). The NLA 
stated that MSHA should consider setting only a PEL and not an action 
level because there is less need for an action level in the mining 
industry than in OSHA-regulated industries (Document ID 1408). The 
AEMA, NVMA, and Tata Chemicals Soda Ash Partners, LLC, stated that the 
action level should be developed on a per-mine or per-company basis or 
should be an internal control only (Document ID 1424; 1441; 1452). The 
Arizona Mining Association suggested a phased approach with incremental 
changes (Document ID 1368). The ACOEM, although in support of the 
action level and proposed PEL, urged a further lowering of the PEL to 
25 [mu]g/m\3\ in the future (Document ID 1405).
    After careful consideration of the comments, MSHA has determined an 
action level of 25 [mu]g/m\3\ is feasible, and the definition of action 
level in the final rule is the same as the proposal. MSHA's FRA shows 
that there will be a greater reduction of morbidity and mortality at 
the action level, but acknowledges that it may not be achievable for 
all mines to consistently maintain an exposure limit below 25 [mu]g/
m\3\. According to NIOSH research, wherever exposure measurements are 
above one-half the PEL, the employer cannot be reasonably confident 
that the employee is not exposed to levels above the PEL on days when 
no measurements are taken (NIOSH, 1975). MSHA establishes the action 
level and sets a sampling frequency for concentrations at or above the 
action level to allow mine operators to act before overexposures occur. 
MSHA acknowledges that, even at exposures of 25 [mu]g/m\3\, some 
residual risks remain. For example, at 25 [mu]g/m\3\, end stage renal 
disease (ESRD) risk is 20.7 per 1,000 MNM miners and 21.6 per 1,000 
coal miners.
    Commenters stated that MSHA should not have an action level. The 
AEMA and NVMA said the Agency does not use an action level in other air 
contaminant exposure rules (Document ID 1424; 1441).
    At exposures of 25 [mu]g/m\3\ or lower, risk of adverse health 
effects remains. The Agency has established action levels equivalent to 
50 percent of the PEL for occupational noise exposure in MNM and coal 
mines (30 CFR 62.101) and equivalent to 50 percent of the exhaust gas 
monitoring standards for underground coal mines (30 CFR 70.1900). MSHA 
survey and enforcement data indicate that the action levels in the 
occupational noise

[[Page 28312]]

and exhaust gas rules have contributed to greater compliance and fewer 
overexposures. Based on its experience, MSHA knows that action levels 
encourage mine operators to be more proactive in providing necessary 
health and safety protection to miners. Furthermore, MSHA was able to 
learn about the health benefits of an action level for respirable 
crystalline silica through the implementation of OSHA's silica final 
rule (2016a). In developing this final rule, MSHA took into 
consideration experience gained under other safety and health standards 
including those established by OSHA. Several OSHA standards established 
action levels for airborne contaminants, especially toxins such as 
benzene, inorganic arsenic, ethylene oxide, and methylene chloride.
    Some commenters, including trade associations, MNM operators, a 
state mining association, and a mining-related business, stated that 
the action level would increase costs for mine operators (Document ID 
1408; 1442; 1419; 1440; 1441; 1392). MSHA recognizes that costs may 
increase as a result of the sampling requirements in the final rule. 
Mine operators are encouraged to reduce exposures below the action 
level to avoid additional costs associated with the sampling 
requirements triggered when exposures are at or above the action level. 
The Agency emphasizes that the requirements of the final rule are 
established to protect miners from the adverse health effects resulting 
from exposure to respirable crystalline silica.
    Several commenters, including industry trade associations, MNM 
operators, and a mining trade association, cautioned that the action 
level was too close to the limit of accurate detection of respirable 
crystalline silica (Document ID 1426; 1413; 1432; 1440; 1448). SSC 
stated that there is little confidence in the reliability of sampling 
results below 50 [mu]g/m\3\ (Document ID 1432).
    MSHA's analytical methods for air samples can reliably detect 
respirable crystalline silica at or below the action level. The MSHA P-
2 and P-7 analytical methods have a reporting limit of 12 [mu]g for 
quartz in mine dust. Both methods are sufficiently sensitive to 
quantify levels of quartz collected on air samples from concentrations 
at the action level. Most accredited laboratories that offer 
crystalline silica analysis by X-ray diffraction use either the OSHA 
ID-142 or NIOSH 7500 methods. The OSHA method specifies a reliable 
quantification limit of 12 [mu]g/m\3\ for quartz, and the NIOSH method 
states that the estimated detection limit for quartz is 5 [mu]g. The 
NIOSH infrared methods, 7603 and 7602, state estimated detection limits 
of 1 and 5 [mu]g of quartz, respectively.
    The AEMA and NVMA disagreed with MSHA's calculation of the action 
level as an 8-hour TWA (Document ID 1424; 1441). These commenters said 
NIOSH recommends calculating exposure levels for a 10-hour shift.
    The final rule includes an 8-hour TWA because it provides more 
protection to miners who work extended shifts. Further discussion of 
the 8-hour TWA is discussed below under Section 60.10--Permissible 
Exposure Limit (PEL).
    The Arizona Mining Association stated the proposed action level is 
not achievable with current available technology (Document ID 1368). 
The commenter provided testimonial information about a mine that 
conducted a baseline test with a continuous dust monitor in an office 
setting and was close to the proposed action level.
    MSHA clarifies that the action level applies only to respirable 
crystalline silica, which is a component of respirable dust. If an 
office or other setting contains levels of respirable crystalline 
silica that meet or exceed the action level, sampling is required under 
the final rule.
    After careful consideration of the rulemaking record, MSHA has 
determined the action level is appropriate. The Agency's experience 
with existing standards indicates that an action level of one-half the 
PEL provides necessary information to mine operators on actions they 
need to take to reduce miners' exposures below the action level, where 
feasible. Operator sampling at or above the action level but at or 
below the PEL also provides critical information to miners on their 
exposures. Under Sec.  60.12(g), operators must share sampling records 
and laboratory reports with miners so that they have an awareness and 
understanding of the important role that engineering and administrative 
controls play in protecting their health. Mine operators who keep their 
exposures below the action level avoid the costs of required compliance 
with provisions triggered by the action level, provide improved health 
protection for miners, and may experience better miner health and less 
turnover. MSHA concludes that an action level is needed at one-half the 
PEL based on residual risk at the PEL of 50 [mu]g/m\3\; the feasibility 
of measuring exposures at an action level of 25 [mu]g/m\3\; and the 
administrative convenience of having the action level at one-half the 
PEL, as it is in other MSHA standards. As discussed in the standalone 
Health Effects document and standalone FRA document, risk remains at 
the PEL of 50 [mu]g/m\3\. Accordingly, MSHA is finalizing these 
additional requirements to reduce remaining risk when those 
requirements will afford benefits to miners and are feasible.
b. Objective Data
    Under the proposal, operators could use ``objective data'' to 
confirm sampling results below the action level and discontinue 
sampling.
    MSHA removes the definition of ``objective data'' in the final 
rule. The term ``objective data'' was defined in the proposed rule as 
``information such as air monitoring data from industry-wide surveys or 
calculations based on the composition of a substance that indicates the 
level of miner exposure to respirable crystalline silica associated 
with a particular product or material or a specific process, task, or 
activity.''
    MSHA received several comments on the proposed definition of 
objective data, with numerous commenters stating that the definition 
was vague and overly broad. Some commenters, including labor 
organizations, a Federal elected official, and an industry trade 
association, requested clarification on how to determine the validity 
and acceptability of objective data and who should make the 
determinations (Document ID 1398; 1449; 1439; 1442). Others, such as 
AIHA, Black Lung Clinics, and AFL-CIO, commented that objective data is 
not an accurate or reliable measure of exposure to respirable 
crystalline silica and that objective data should not be used to exempt 
operators from sampling. (Document ID 1351; 1410; 1449; 1412).
    The Agency agrees with commenters who asserted sampling is more 
accurate than using objective data as defined in the proposed rule. 
Additional discussion on the comments received on objective data and 
MSHA's response regarding the proposal are discussed in Section 
VIII.B.5. Section 60.12.--Exposure Monitoring.
c. Respirable Crystalline Silica
    The final rule, like the proposal, defines ``respirable crystalline 
silica'' as ``quartz, cristobalite, and/or tridymite contained in 
airborne particles that are determined to be respirable by a sampling 
device designed to meet the characteristics for respirable-particle-
size-selective samplers that conform to the International Organization 
for Standardization (ISO) 7708:1995: Air Quality--Particle Size 
Fraction Definitions for Health-Related Sampling.''

[[Page 28313]]

    MSHA did not receive any comments on the definition of respirable 
crystalline silica. The final rule's definition has two main 
advantages. First, the ISO 7708:1995 definition of respirable 
particulate mass represents an international consensus, and by adopting 
the ISO 7708:1995 criterion, MSHA is able to harmonize its standards 
with the standards used by other occupational health and safety 
organizations in the U.S. and internationally, including ACGIH, OSHA 
(29 CFR 1910.1053 and 29 CFR 1926.1153), NIOSH (2003b, Manual of 
Analytical Methods), and the European Committee for Standardization 
(CEN) (ISO 7708:1995). Second, the definition eliminates 
inconsistencies in the existing standards for MNM and coal mines. 
Defining respirable crystalline silica to include quartz, cristobalite, 
and/or tridymite and establishing a PEL for exposure to respirable 
particles of any combination of these three polymorphs provides 
consistency across different mining sectors.
d. Specialist
    The final rule, like the proposal, defines ``specialist'' as ``an 
American Board-Certified Specialist in Pulmonary Disease or an American 
Board-Certified Specialist in Occupational Medicine.'' The definition 
is applicable to Sec.  60.15, which addresses medical surveillance for 
MNM mines. Under the medical surveillance requirements, MNM mine 
operators are required to provide miners with medical examinations 
performed by a specialist in pulmonary disease or occupational medicine 
or a PLHCP.
    MSHA did not receive any comments on the definition of specialist. 
The medical surveillance provisions for MNM mines require a specialist 
to conduct a follow-up medical examination no later than 2 years after 
the follow-up examination for new miners if the chest X-ray shows 
evidence of pneumoconiosis or the spirometry examination indicates 
evidence of decreased lung function (Sec.  60.15(c)(3)). The provision 
is intended to ensure that any miner who shows evidence of 
pneumoconiosis or decreased lung function is seen by a professional 
with expertise in respiratory disease. The definition is important 
because it ensures miners benefit from expert medical judgment and 
receive advice regarding how work practices and personal habits could 
affect their health.
3. Section 60.10--Permissible Exposure Limit (PEL)
    The final rule, like the proposal, requires the mine operator to 
ensure that no miner is exposed to respirable crystalline silica in 
excess of 50 [mu]g/m\3\ for a full-shift exposure, calculated as an 8-
hour TWA for all mines. The PEL is the same for both MNM mines and coal 
mines. For coal mines, this provision establishes a PEL for respirable 
crystalline silica independent from the existing respirable coal mine 
dust standards. The PEL in the final rule replaces the Agency's 
existing exposure limits for respirable crystalline silica or 
respirable quartz in 30 CFR parts 56, 57, 70, 71, and 90. (The existing 
respirable coal mine dust standards unrelated to quartz remain the 
same.) Below is a detailed discussion of the comments received on this 
section and modifications made in response to the comments.
a. PEL of 50 [mu]g/m\3\
    MSHA analyzed and considered the comments received in response to 
the proposed PEL of 50 [mu]g/m\3\. Most commenters supported lowering 
the existing quartz or silica exposure limits, and many specifically 
expressed support for the proposed PEL, including labor organizations, 
an advocacy organization, medical professional associations, and mining 
trade associations, (Document ID 1398; 1447; 1449; 1416; 1421; 1424; 
1428; 1418; 1439; 1443). Some of these commenters, including AEMA and 
NMA, noted that the proposed PEL aligns with OSHA's PEL for non-mining 
industries, as well as with NIOSH recommendations (Document ID 1424; 
1428). Several commenters, including Black Lung Clinics, APHA, and 
Miners Clinic of Colorado, underscored that substantial risk of silica-
related disease exists at 100 [mu]g/m\3\ compared to lower risks at 50 
[mu]g/m\3\ (Document ID 1410; 1416; 1418). Black Lung Clinics noted 
that the indirect approach to limiting silica exposure in coal miners 
has not been effective (Document ID 1410). Other commenters, including 
the AFL-CIO and NABTU, stated that the proposed PEL is technologically 
and economically feasible and would reduce the risk of death and 
disease to miners (Document ID 1449; 1414). Other commenters similarly 
expressed support for the proposed PEL, with the USW stating that the 
proposed PEL is necessary and feasible, and The American Thoracic 
Society et al. stating that it is supported by science and could be 
readily achieved with currently available engineering interventions 
(Document ID 1447; 1421).
    AIHA and MSHA Safety Services did not believe the proposed PEL was 
appropriate, with the AIHA stating that the proposed PEL of 50 [mu]g/
m\3\ does not protect miners from adverse health effects and 
recommending a PEL of 25 [mu]g/m\3\ instead (Document ID 1351; 1392). 
While some commenters such as the USW and the AFL-CIO did support 
MSHA's proposal to lower the existing exposure limits, these commenters 
noted that several other countries or jurisdictions have set standards 
reducing legal permissible limits to 25 [mu]g/m\3\ (Document ID 1447; 
1449). One commenter, MSHA Safety Services Inc., opposed the rule 
stating that the existing standards (i.e., 100 [mu]g/m\3\), if 
followed, would be more than sufficient (Document ID 1392). This 
commenter, citing data retrieved from MSHA's Mine Data Retrieval System 
(MDRS), stated that silicosis and pneumoconiosis affect only 
underground coal miners and not MNM miners.
    After considering the data and evidence in the rulemaking record, 
the final rule establishes a PEL of 50 [mu]g/m\3\. MSHA's examination 
of health effects evidence (discussed in the preamble in Section V. 
Health Effects and Section VI.--Final Risk Analysis Summary, as well as 
in the standalone Health Effects document and standalone FRA document) 
demonstrates that exposure to respirable crystalline silica at the 
existing exposure limits results in a risk of material impairment of 
health or functional capacity, and that exposure at the lower level of 
the PEL will reduce that risk. MSHA's FRA indicates that 45 years of 
exposure to respirable crystalline silica under the new PEL would lead 
to a total of 1,067 lifetime avoided deaths, including 248 avoided 
deaths from silicosis, 536 avoided deaths from all forms of non-
malignant respiratory disease (including silicosis as well as other 
diseases such as chronic bronchitis and emphysema), 82 avoided deaths 
from lung cancer, and 200 avoided deaths from renal diseases.
    As some commenters noted, the PEL is consistent with NIOSH's 
respirable crystalline silica recommended exposure limit of 50 [mu]g/
m\3\ for workers and with the PEL of 50 [mu]g/m\3\ for respirable 
crystalline silica covering U.S. workplaces regulated by OSHA. In 1974, 
NIOSH recommended that occupational exposure to crystalline silica be 
controlled so that ``no worker is exposed to a TWA of silica 
[respirable crystalline silica] greater than 50 [mu]g/m\3\ as 
determined by a full-shift sample for up to a 10-hour workday over a 
40-hour workweek'' (NIOSH, 1974). In 2016, OSHA promulgated a rule 
establishing that, for construction, general industry, and the maritime 
industry, workers' exposures to respirable crystalline silica must not 
exceed 50 [mu]g/m\3\, averaged over an 8-hour day (29 CFR

[[Page 28314]]

1910.1053(c); 29 CFR 1926.1153(d)(1)).\66\
---------------------------------------------------------------------------

    \66\ NIOSH conducted a literature review of studies containing 
environmental data on the harmful effects of exposure to respirable 
crystalline silica. Based on these studies, and especially fifty 
years' worth of studies on Vermont granite workers during which time 
dust controls improved, exposures fell, and silicosis diagnoses 
neared zero, NIOSH recommended an exposure limit of 50 [mu]g/m\3\ 
for all industries. OSHA's examination of health effects evidence 
and its risk assessment led to the conclusion that occupational 
exposure to respirable crystalline silica at the previous PELs, 
which were approximately equivalent to 100 [mu]g/m\3\ for general 
industry and 250 [mu]g/m\3\ for construction and maritime 
industries, resulted in a significant risk of material health 
impairment to exposed workers, and that compliance with the revised 
PEL would substantially reduce that risk. (81 FR at 16755). OSHA 
considered the level of risk remaining at the revised PEL to be 
significant but determined that a PEL of 50 [mu]g/m\3\ is 
appropriate because it is the lowest level feasible.
---------------------------------------------------------------------------

    As discussed in the standalone Health Effects document, 
occupational exposure to respirable crystalline silica is detrimental 
to an individual's health. Silicosis and other diseases caused by 
respirable crystalline silica exposure are irreversible, disabling, and 
potentially fatal. At the same time, these diseases are exposure-
dependent and are therefore preventable. The lower a miner's exposure 
to respirable crystalline silica, the less likely that miner is to 
suffer from adverse health effects.
    Regarding the comments recommending MSHA adopt a PEL of 25 [mu]g/
m\3\ and some comments noting that other countries or provinces have 
set standards reducing permissible limits to 25 [mu]g/m\3\, MSHA 
considered establishing a PEL of 25 [mu]g/m\3\ as part of MSHA's 
Regulatory Alternative 2. Under this regulatory alternative, a more 
stringent PEL of 25 [mu]g/m\3\ is combined with less stringent 
monitoring provisions compared to the final rule. MSHA estimated that 
there will be a greater reduction of morbidity and mortality cases as a 
result of lowering the PEL to 25 [mu]g/m\3\. MSHA also estimated that 
the compliance costs would outweigh the benefits resulting in negative 
net benefits. MSHA's enforcement experience shows that for mining 
occupations exposed to the highest levels of respirable crystalline 
silica, in both MNM mines and coal mines, a PEL of 25 [mu]g/m\3\ is not 
generally achievable. For example, MSHA reviewed exposures of 
designated occupations in underground coal mines and crusher and 
equipment operators in MNM mines, and determined that on average, miner 
exposures exceed 25 [mu]g/m\3\ when all feasible engineering controls 
are used. Although other countries and jurisdictions may have adopted a 
PEL of 25 [mu]g/m\3\, MSHA did not choose this regulatory alternative 
because a PEL of 25 [mu]g/m\3\ may not be achievable for all mines 
(Document ID 1447; 1449). For some mines, a PEL of 25 [mu]g/m\3\ would 
present a substantial challenge. Commenters did not provide specific 
information on the regulatory programs for the countries and 
jurisdictions that have established a PEL of 25 [mu]g/m\3\. Further 
explanation and discussion of the regulatory alternatives can be found 
in the standalone FRIA document and in the preamble in Section IX. 
Summary of Final Regulatory Impact Analysis and Regulatory 
Alternatives.
    An individual urged MSHA to adopt, in addition to the proposed PEL 
of 50 [mu]g/m\3\, an upper exposure level of 100 [mu]g/m\3\ that would 
trigger the withdrawal of miners from the affected area rather than 
permit continued miner work in affected jobs in extremely elevated 
concentrations above the PEL (Document ID 1367). Because MSHA has 
determined that the final rule's sampling obligations will reduce 
overexposures and that the corrective actions requirements establish 
strong protections for miners when they are exposed over the PEL, the 
Agency has not set an upper limit that would automatically trigger the 
withdrawal of miners. As discussed at the public hearings and required 
in Sec.  60.12, operators must immediately report all exposures above 
the PEL from operator sampling to the MSHA District Manager or any 
other MSHA office designated by the District Manager, so that MSHA 
enforcement will be apprised of exposures above the PEL and can take 
appropriate actions. As discussed above in Section VIII.A. General 
Issues, failure to abate miners' exposures above the PEL could merit a 
withdrawal order under section 104(b) of the Mine Act.
    In conclusion, MSHA has determined, as presented in the standalone 
FRA document accompanying this final rule, that: (1) under previous 
respirable crystalline silica or quartz standards, miners were exposed 
to respirable crystalline silica at concentrations that result in a 
risk of material impairment of health or functional capacity and (2) 
lowering the PEL to 50 [mu]g/m\3\ will substantially reduce this risk. 
According to the CDC, between 1999 and 2014, miners died from 
silicosis, COPD, lung cancer, and NMRD at substantially higher rates 
than did members of the general population; for silicosis, the 
proportionate mortality ratio for miners was 21 times as high.\67\ 
Evidence in the standalone Health Effects document demonstrates that 
exposure to respirable crystalline silica at levels permitted under 
previous standards contributes to this excess mortality. Based on the 
evidence and data evaluated during the rulemaking process, MSHA has 
determined that a PEL of 50 [mu]g/m\3\ is appropriate and is 
technologically and economically feasible for all mines. Mine operators 
will be able to maintain miner exposures at or below the PEL of 50 
[mu]g/m\3\ through some combination of properly maintaining existing 
engineering controls, implementing new engineering controls (e.g., 
ventilation systems, dust suppression devices, and enclosed cabs or 
control booths with filtered breathing air), and requiring changes to 
work practices through administrative controls. MSHA determined not to 
set the PEL at 25 [mu]g/m\3\. MSHA's enforcement experience shows that 
for mining occupations exposed to the highest levels of respirable 
crystalline silica, in both MNM mines and coal mines, a PEL of 25 
[mu]g/m\3\ is not generally achievable. For example, MSHA reviewed 
exposures of designated occupations in underground coal mines and 
crusher and equipment operators in MNM mines, and determined that on 
average, miner exposures exceed 25 [mu]g/m\3\ when all feasible 
engineering controls are used. While MSHA estimated that there would be 
a greater reduction of morbidity and mortality cases as a result of 
lowering the PEL to 25 [mu]g/m\3\, the Agency estimates that compliance 
costs of Regulatory Alternative 2 establishing a PEL of 25 [mu]g/m\3\ 
would outweigh the benefits, resulting in negative net benefits. A PEL 
of 25 [mu]g/m\3\ may not be achievable for all mines. MSHA did not 
choose this regulatory alternative.
---------------------------------------------------------------------------

    \67\ Data on occupational mortality by industry and occupation 
can be accessed by visiting the CDC website at https://www.cdc.gov/niosh/topics/noms/default.html (last accessed Jan. 10, 2024). The 
NOMS database provides detailed mortality data for the 11-year 
period from 1999, 2003 to 2004, and 2007 to 2014.
---------------------------------------------------------------------------

b. PEL in Coal Mines
    In the case of coal mines, the final rule establishes a PEL for 
respirable crystalline silica independent from the respirable coal mine 
dust (RCMD) standard. The 2014 RCMD Standard does not directly limit 
coal miners' exposure to respirable crystalline silica; under the 
existing coal mine respirable dust standard, MSHA cannot issue a 
separate citation for silica or quartz.
    Separating the respirable crystalline silica PEL from the 
respirable coal mine dust standard allows for coal miners' exposure to 
respirable crystalline silica to be controlled directly, rather than 
only indirectly through the respirable

[[Page 28315]]

coal mine dust standard. This will ensure greater health protection for 
coal miners.
    MSHA solicited comments on whether to eliminate the reduced 
standard for total respirable dust when quartz is present at coal mines 
and received feedback from stakeholders generally agreeing with the 
Agency's proposal to establish a standard for respirable crystalline 
silica that is independent from the respirable coal mine dust standard, 
including other mine industry organizations, a labor union, mining 
trade associations, and Black Lung Clinics (Document ID 1378; 1398; 
1406; 1428; 1410). The ACLC expressed support for a standalone and 
separately enforceable PEL, but recommended maintaining a reduced 
standard for respirable dust when silica is present in coal mines, 
which would ensure that standalone effects of silica and coal dust are 
accounted for and allow for better monitoring overall (Document ID 
1445). The NMA, the MCPA, and the Pennsylvania Coal Alliance supported 
the removal of the respirable dust standards when quartz is present 
(i.e., Sec. Sec.  70.101 and 71.101, and 90.101), reasoning that they 
are no longer needed since the rule proposes a standalone standard for 
respirable crystalline silica (Document ID 1428; 1406; 1378).
    MSHA has concluded that establishing an independent and lower PEL 
for respirable crystalline silica for coal mines allows more effective 
control of respirable crystalline silica than the existing reduced 
standards because the separate standard is less complicated and more 
protective. MSHA believes that the adoption of a separate improved 
standard that carries risk of a citation and monetary penalty when 
overexposures of the respirable crystalline silica PEL occur is thus 
more protective than the indirect method under the existing reduced 
standards. MSHA clarifies that mine operators will continue to sample 
for respirable coal mine dust under existing Sec. Sec.  70.100, 71.100, 
and 90.100. MSHA agrees with the commenters supporting the removal of 
Sec. Sec.  70.101, 71.101, and 90.101. With the PEL and action level 
(both calculated as a full-shift 8-hour TWA), sampling, recordkeeping, 
and reporting requirements in this final rule, MSHA does not believe 
that retaining the reduced standard is necessary. MSHA believes that 
the implementation of the separate silica standard will ensure that 
operators are correctly evaluating and implementing controls to protect 
miners from respirable crystalline silica. Further, MSHA will continue 
its sampling. Under the final rule, MSHA is removing these sections in 
their entirety since they are no longer needed. See Section VIII.C. 
Conforming Amendments for additional details.
c. Full Shift, 8-Hour TWA
    Under the final rule, the PEL and the action level apply to a 
miner's full-shift exposure, calculated as an 8-hour TWA. This limit 
means that over the course of any work shift, exposures can fluctuate 
but the average exposure to respirable crystalline silica cannot exceed 
50 [mu]g/m\3\ for the PEL and 25 [mu]g/m\3\ for the action level. Under 
this final rule, a miner's work shift exposure is calculated as 
follows:
[GRAPHIC] [TIFF OMITTED] TR18AP24.083

    Regardless of a miner's actual working hours (full shift), 480 
minutes is used in the denominator. This means that the respirable 
crystalline silica collected over an extended period (e.g., a 12-hour 
shift) is calculated (or normalized) as if it were collected over 8 
hours (480 minutes). For example, if a miner was sampled for 12 hours 
and 55 [mu]g of respirable crystalline silica was collected in the 
sample over that 12-hour period, the miner's respirable crystalline 
silica 8-hour TWA exposure would be 67 [mu]g/m\3\, calculated as 
follows:
[GRAPHIC] [TIFF OMITTED] TR18AP24.084

    This calculation method (i.e., full shift, 8-hour TWA) is the one 
that MSHA uses to calculate exposures of MNM miners to respirable 
crystalline silica and other airborne contaminants under the existing 
standards (30 CFR 56.5001, 57.5001); it differs from the existing 
method of calculating a coal miner's exposure to respirable coal mine 
dust (30 CFR 70.101, 71.101, and 90.101). For coal miners, the existing 
calculation method uses the entire duration of a miner's work shift in 
both the numerator and denominator, resulting in the total mass of 
respirable coal mine dust collected over an entire work shift scaled by 
the sample's air volume over the same period. This is referred to as 
``full shift TWA'' hereafter.
    MSHA received comments both in agreement with the proposed 
calculation method and against it. Some commenters, including the AFL-
CIO and USW, stated that they support the proposed calculation method 
of full-shift monitoring and calculating exposures over an 8-hour 
period (i.e., using 480 minutes in the denominator) to actively capture 
the total cumulative exposure to silica dust (Document ID 1449; 1447). 
The American Thoracic Society et al. stated that working longer shifts 
means miners have longer exposure periods, which increases the 
cumulative burden of exposure and reduces the rest time miners have for 
recuperating and clearing their lungs (Document ID 1421). In contrast, 
other commenters, including other mine industry organizations, mining 
trade associations, state mining associations, and MNM operators 
preferred the use of the full shift time period in the calculation 
method denominator (i.e., using the entire duration of the miner's 
extended work shift in the denominator), stating that normalizing the 
extended shift sampling result to an 8-hour period (i.e., using 480 
minutes in the denominator) inaccurately skews the results (Document ID 
1378; 1424; 1428; 1441; 1443; 1432). These commenters stated that the 
proposed method improperly inflates the sampling results and actually 
makes the standard more stringent by effectively lowering the PEL for 
longer shifts. Some of these commenters, including MSHA Safety Services 
Inc. and NVMA, further stated that MSHA's statement in the proposal 
that the Agency uses NIOSH's recommendation is misleading because the 
NIOSH recommendation is,

[[Page 28316]]

according to the commenters, for a 10-hour workday during a 40-hour 
workweek (Document ID 1392; 1441).
    Under the final rule, the PEL and action level applies to a miner's 
full-shift exposure, calculated as an 8-hour TWA. MSHA agrees with 
commenters who stated that the full shift, 8-hour TWA captures 
cumulative exposure to silica dust accurately. The goal of the 
respirable crystalline silica final rule is to prevent miners at all 
times from suffering a body burden high enough to cause adverse health 
effects.
    ``Body burden'' refers to the total amount of a substance that has 
accumulated in the body at any given time (ATSDR, 2009). This reflects 
the interplay between cumulative exposure, pulmonary deposition, and 
lung clearance, in the case of respirable crystalline 
silica.68 69 As discussed in the standalone FRA document, 
cumulative exposure to respirable crystalline silica is well 
established as an important risk factor in the development of silica-
related disease.
---------------------------------------------------------------------------

    \68\ The pulmonary uptake and clearance of airborne mine dust 
are dependent upon many factors, including a miner's breathing 
patterns, exposure duration, concentration (dose), particle size, 
and durability or bio-persistence of the particle. These factors 
also affect the time it takes to clear particles, even after 
exposure ceases.
    \69\ Respirable crystalline silica is cleared slowly from the 
body and remains in the lungs longer than most other, more soluble 
minerals and organic particulates in mine air. Pairon et al. (1994) 
counted respirable crystalline silica particles in the 
bronchoalveolar fluid of individuals occupationally exposed to 
silica-bearing respirable dust and confirmed that respirable 
crystalline silica was one of the most persistent (i.e., most slowly 
eliminated) mineral particles in the lung. The slow clearance of 
silica particles explains the accumulation (build-up) of particles 
in the human lung that can occur with repeated exposures to airborne 
silica as well as its detection in lung tissue years after exposure 
stops (Dobreva et al., 1975; Case et al., 1995; Loosereewanich et 
al., 1995; Dufresne et al., 1998; Borm and Tran, 2002).
---------------------------------------------------------------------------

    MSHA has determined that it is important to specify that exposures 
be normalized to 8-hour TWAs.\70\ This is because working longer hours 
can lead to the inhalation of more respirable crystalline silica into 
the lungs, and the PEL and action level must take this into account. 
For example, working 12 hours leads to 50% more silica entering the 
lung compared with working 8 hours, assuming other factors are equal 
(e.g., concentration of respirable crystalline silica and breathing 
parameters). By normalizing daily exposures to 8-hour workdays, the 
final rule provides miners working longer shifts a level of protection 
against cumulative inhaled doses that is reasonably equivalent to the 
protection provided to miners working shorter shifts. This is a 
relevant issue because MSHA has observed that miners commonly work 
extended shifts, with many working 10-hour or longer 
shifts.71 72 MSHA's calculation method (like the existing 
MNM calculation method) normalizes to an 8-hour TWA. If a miner works 
an extended shift of 12 hours and a sample of 55 [mu]g of respirable 
crystalline silica is collected, the full shift 8-hour TWA calculation 
for that sample is 67 [mu]g/m\3\. This result treats the full 
cumulative exposure occurring over the entire shift in the same way as 
if it occurred over 8 hours. The full shift TWA (the existing 
calculation method for coal miners) would yield a calculated exposure 
of 45 [mu]g/m\3\, based on the entire duration of the miner's work 
shift. The full shift 8-hour TWA calculation provides more protection 
for miners than the full shift TWA calculation that makes no adjustment 
for extended shifts.
---------------------------------------------------------------------------

    \70\ The ACGIH (2022) acknowledges the issue of extended work 
shifts for airborne contaminants, including respirable crystalline 
silica, stating, ``numerous mathematical models to adjust for 
unusual work schedules have been described. In terms of toxicologic 
principles, their general objective is to identify a dose that 
ensures that the daily peak body burden or weekly peak body burden 
does not exceed that which occurs during a normal 8-hour/day, 5-day/
week shift.'' There are associated concerns with the body burden 
from an ``unusual work schedule'' such as a 10- or a 12- hour shift. 
As Elias and Reineke (2013) stated, ``if the length of the workday 
is increased, there is more time for the chemical to accumulate, and 
less time for it to be eliminated. It is assumed that the time away 
from work will be contamination free. The aim is to keep the 
chemical concentrations in the target organs from exceeding the 
levels determined by the TLVs[supreg] (8-hour day, 5-day week) 
regardless of the shift length. Ideally, the concentration of 
material remaining in the body should be zero at the start of the 
next day's work.''
    \71\ Sampling hours of coal mine dust samples approximate the 
working hours of coal miners who were sampled. According to the coal 
mine dust samples for a 5-year period (August 2016-July 2021), 90 
percent of the samples by MSHA inspectors were from miners working 8 
hours or longer and about 43 percent of the samples from miners 
working 10 hours or longer. The dust samples by coal mine operators 
show that over 98 percent of them were from miners working 8 hours 
or longer and over 26 percent from the miners working 10 hours or 
longer. Of the MNM dust samples by MSHA inspectors for a 15-year 
period (January 2005-December 2019), approximately 78 percent were 
from miners working longer than 8 hours. These dust samples are 
available at Mine Data Retrieval System [bond] Mine Safety and 
Health Administration (MSHA), https://www.msha.gov/data-and-reports/mine-data-retrieval-system (last accessed Jan. 10, 2024).
    \72\ Unlike workers in many other sectors, miners not only work 
longer shifts but also typically work much longer than 40 hours per 
week. According to BLS data, between 2017 and 2022, the average 
number of weekly working hours for all miners ranged from 45.1 to 
46.7. (Bureau of Labor Statistics, Average weekly hours of 
production and nonsupervisory employees, mining (except oil and 
gas), not seasonally adjusted, Series ID CEU1021200007, data for 
2017-2022, retrieved March 9, 2024.) From a body burden standpoint, 
this means that longer working shifts for miners are likely also 
associated with a greater number of cumulative hours of exposure. 
That suggests that it is not the case that miners are working four 
10-hour shifts instead of five 8-hour shifts, giving them shorter 
recovery time between some shifts but then a longer recovery time 
(e.g., 3 days off continuously). Instead, many miners are likely 
working more long shifts--e.g., five 10-hour shifts in a week, given 
the average of more than 45 hours for all miners--leaving their 
lungs very little recovery time after silica exposure.
---------------------------------------------------------------------------

    Because the full shift, 8-hour TWA calculation takes this 
additional factor into account, sampling using this calculation method 
likely results in more sampling results that show overexposures, which 
leads to exposure monitoring, corrective actions, and/or respiratory 
protection for miners that may not have otherwise been provided using 
the full shift TWA calculation. The concept of adjusting occupational 
exposure limits for ``extended shifts'' has been addressed by 
researchers (Brief and Scala, 1986; Elias and Reineke, 2013). Their 
research is based on the industrial hygiene concept that longer 
workdays lead to more time for the workplace chemical to accumulate in 
the body and less time for it to be eliminated. To account for this, 
the research establishes models that adjust (i.e., lower) the exposure 
limits using formulas that factor in the longer workdays and the 
corresponding shorter recovery periods.
    This final rule establishes a lower PEL and applies it to all 
miners using a consistent method for calculating exposures. These 
changes improve the health and safety of miners while making compliance 
more straightforward and transparent. NIOSH has also supported the use 
of the TWA and has discussed this term since the publication of the 
NIOSH Pocket Guide to Chemical Hazards (First Edition, 1978) (the 
``White Book'').
    MSHA's PEL for a miner's full-shift exposure calculated as an 8-
hour TWA differs from OSHA standards for extended work shifts. In the 
OSHA standards, sampling for extended work shifts is conducted using 
the worst (i.e., highest-exposure) 8 hours of a shift or collecting 
multiple samples over the entire work shift and using the highest 
samples to calculate an 8-hour TWA. 81 FR 16286, 16765. This differs 
from MSHA's calculation method because, under MSHA's standards, miners 
are sampled for the duration of their work shift and the total 
respirable crystalline silica collected over the entire duration of 
that extended work shift, not the worst 8 hours only, is used in the 
calculation.
    The NMA and AEMA disagreed with how MSHA calculates the full shift 
8-hour TWA and stated that if MSHA does not use the entire duration 
worked, the Agency should instead use OSHA's method of sampling for the 
worst 8-hour

[[Page 28317]]

time period for extended work shifts (Document ID 1428; 1424).
    MSHA has not included the commenter's suggestion in the final rule. 
MSHA's requirement in the final rule to sample miners for the entire 
duration of their work shift will provide an accurate representation of 
their exposures. Calculating the full shift 8-hour TWA will better 
protect the health of miners who work extended shifts because it 
considers the heightened risks posed by increased cumulative exposure 
and shorter recovery time. The final rule full shift 8-hour TWA 
calculation is consistent with MSHA's longstanding MNM calculation 
method, which is based on the guidance provided by the ACGIH in 1973 
(TLVs[supreg] Threshold Limit Values for Chemical Substances in 
Workroom Air Adopted by ACGIH for 1973). This calculation method is 
supported by NIOSH and continues to be supported in the current 
guidance provided by the ACGIH.
d. Error Factor
    Some commenters, including NSSGA and SSC, expressed concerns about 
whether silica can be accurately and consistently measured at the 
action level and PEL (Document ID 1448; 1432). The AIHA suggested that 
statistics of sampling and sample analysis should be considered to 
identify upper and lower confidence limits (Document ID 1351). Several 
commenters, including NMA and West Virginia Coal Association (WVCA), 
recommended that the PEL and action level should have a margin of 
error, or error factor, to account for sampling and analysis errors 
(Document ID 1428; 1443). WVCA recommended that, as in the 2014 RCMD 
Standard, MSHA should apply an error factor to the PEL to normalize 
results to account for errors in sampling and weighing that cause 
deviations in individual concentration measurements (Document ID1443). 
The NMA cited sources to assist with determining the error factor 
(Document ID 1428).
    In Section VII.A. Technological Feasibility, MSHA determined that 
current methods to sample respirable dust and analyze samples for 
respirable crystalline silica by XRD and IR methods are capable of 
reliably measuring silica concentrations in the range of the final 
rule's PEL and action level. This finding is based on the following 
considerations: (1) there are many sampling devices available that 
conform to the ISO specification for particle-size selective samplers 
with an acceptable level of measurement bias, and (2) both the XRD and 
IR methods can measure respirable crystalline silica with acceptable 
precision at amounts that would be collected by samplers when airborne 
concentrations are at or around the PEL and action level. Thus, MSHA 
finds that the sampling and analysis requirements under the final rule 
are technologically feasible.
    MSHA is confident that current sampling and analytical methods for 
respirable crystalline silica provide accurate estimates of measured 
exposures. Because there are multiple sampling methods that comply with 
the ISO 7708:1995 standard and variations in laboratory analysis 
methods, this final rule does not include a specific error factor. Mine 
operators can rely on sampling results from ISO-accredited laboratories 
to meet the sampling requirements of Sec.  60.12(f) to determine their 
compliance with the PEL and action level under the final rule. Miners 
should be confident that those exposure results provide them with 
reasonable estimates of their exposures to respirable crystalline 
silica.
4. Section 60.11--Methods of Compliance
    The final rule identifies the methods for compliance in Sec.  
60.11. Section 60.11 paragraph (a), unchanged from the proposal, 
requires mine operators to install, use, and maintain feasible 
engineering controls, supplemented by administrative controls when 
necessary, to keep each miner's exposure to respirable crystalline 
silica at or below the PEL. Paragraph (b), unchanged from the proposal, 
states that rotation of miners shall not be considered an acceptable 
administrative control used for compliance with the PEL. Below is a 
detailed discussion of the comments received on this section and 
modifications made in response to the comments.
a. 60.11(a)--Engineering and Administrative Controls
    Paragraph (a) requires mine operators to use feasible engineering 
controls as the primary means of controlling respirable crystalline 
silica; administrative controls can be used, when necessary, as 
supplementary controls.
    Examples of engineering controls include, but are not limited to, 
ventilation systems, dust suppression devices, enclosed cabs or control 
booths with filtered breathing air, and changes in materials handling 
or equipment used. Engineering controls generally suppress (e.g., using 
water sprays, wetting agents, foams, water infusion), dilute (e.g., 
ventilation), divert (e.g., water sprays, passive barriers, 
ventilation), or capture dust (e.g., dust collectors) to minimize the 
exposure of miners working in the surrounding areas. The use of 
automated ore-processing equipment and remote monitoring can also help 
to reduce or eliminate miners' exposures to respirable crystalline 
silica.
    Examples of administrative controls include, but are not limited 
to, work practices that change the way tasks are performed to reduce a 
miner's exposure. These practices could include work process training; 
housekeeping procedures; proper work positions of miners; cleaning of 
spills; and measures to prevent or minimize contamination of clothing 
to help decrease miners' exposure to respirable crystalline silica.
    MSHA requested comments on the proposed requirement that mine 
operators install, use, and maintain feasible engineering and 
administrative controls to keep miners' exposures to respirable 
crystalline silica at or below the proposed PEL. The Agency received 
comments both supporting and opposing the proposal.
    Several commenters, including an industrial hygiene professional 
association, a labor union, and black lung clinics, expressed support 
for the use of feasible engineering controls and administrative 
controls to keep miners' exposures to respirable crystalline silica 
below the proposed PEL (Document ID 1351; 1398; 1410; 1353). AFL-CIO, 
UMWA, and NMA stated that mine operators should already be utilizing 
feasible engineering and administrative controls to comply with law and 
with their existing ventilation plans (Document ID 1449; 1398; 1428). 
Black Lung Clinics urged MSHA to require that mine operators rely 
primarily on engineering controls to limit dust exposure, with 
administrative controls serving as supplemental measures (Document ID 
1410).
    Other commenters identified limitations with engineering controls. 
NSSGA, US Silica, and a presenter at one of the hearings provided the 
following examples where engineering controls will not suffice due to 
the nature of the work: non-routine maintenance tasks; periodic 
maintenance tasks; tasks of limited duration; and seasonal tasks 
(Document ID 1448; 1455; 1353). US Silica also stated that MSHA must 
offer more flexible options for control methods and give more 
consideration to the challenges of implementing certain controls at 
certain mines (Document ID 1455).
    After carefully considering the comments, MSHA has concluded that 
the requirement for installation, use, and maintenance of feasible 
engineering

[[Page 28318]]

controls, supplemented by administrative controls, when necessary, will 
remain unchanged from the proposal. In MSHA's experience, engineering 
controls are the most effective method of compliance and the most 
protective means of controlling dust generation at the source.
    Engineering controls, which address the generation of dust at its 
source, minimize respirable crystalline silica exposures of all miners, 
including those in surrounding work areas, who may not be working at 
the dust generating source. In contrast to other controls and other 
interventions, engineering controls can be regularly evaluated and 
monitored, which increase their effectiveness.
    NIOSH has long promoted the use of engineering controls to control 
miners' exposures to respirable crystalline silica. This final rule 
aligns with the 1995 NIOSH recommendation that ``the mine operator 
shall use engineering controls and work practices [administrative 
controls] to keep worker exposures at or below the REL [recommended 
exposure limit]'' (NIOSH, 1995, page 5). Specifically, NIOSH recommends 
the use of engineering controls to keep free silica dust exposures 
below the REL of 50 [mu]g/m\3\ (NIOSH, 1974). NIOSH also supported the 
use of engineering controls as the primary means of protecting miners 
from exposure to respirable crystalline silica in its public response 
to MSHA's 2019 RFI (AB36-COMM-36). NIOSH stated that ``[r]espirators 
should only be used when engineering control systems are not feasible. 
Engineering control systems, such as adequate ventilation or scrubbing 
of contaminants, are the preferred control methods for reducing worker 
exposures.''
    Requiring engineering controls as the primary method of compliance 
is consistent with generally accepted industrial hygiene principles, 
existing Agency standards, and the Mine Act. See 30 U.S.C. 801(e) 
(explaining that operators have the ``primary responsibility to prevent 
the existence of [unhealthy] conditions'' in mines); 30 U.S.C. 841(b) 
(requiring underground coal mine operators to keep work environments 
sufficiently free from respirable dust); 30 U.S.C. 842(h) (stating 
primacy of engineering controls for underground coal mines). MSHA's 
existing MNM standards for airborne contaminants require that mine 
operators control miners' exposure to airborne contaminants, where 
feasible, through preventing contamination, using exhaust ventilation 
to remove contaminants, or diluting with uncontaminated air (30 CFR 
56.5005 and 57.5005). The existing MSHA standards for respirable coal 
mine dust (RCMD) require mine operators to implement engineering 
controls to maintain compliance. In MSHA's 2014 RCMD Standard, the 
Agency required operators to use engineering and administrative 
controls and did not permit the use of respirators, including powered 
air-purifying respirators (PAPRs), as a method to achieve compliance. 
Additionally, numerous commenters representing industry, labor, and 
public health supported the proposal's priority of engineering controls 
as the primary means of reducing exposure to respirable crystalline 
silica.
    Some commenters provided specific examples when discussing 
engineering control limitations. The IME stated that MSHA should allow 
the use of equivalent dust suppression methods, where an alternative 
exists, and its effectiveness can be demonstrated (Document ID 1404). 
USW explained that engineering controls must be capable of dealing with 
all belt speeds for collection and suppression and be protected from 
freezing in cold weather which can increase their exposure (Document ID 
1447). Conspec Controls questioned whether MSHA will explain how to 
reduce dust particulate during operations and how different systems 
will be prioritized in instances where an action improves the dust 
conditions but exacerbates gas readings (Document ID 1324).
    After reviewing these comments, the Agency agrees that differences 
in mine size, job duties, commodity mined, equipment, and environmental 
conditions across the mining industry necessitate different types of 
engineering controls. However, in MSHA's experience, the mine operator 
has the information and experience at their mine to determine which 
engineering controls are feasible and effective at reducing respirable 
crystalline silica exposures for their mining conditions. For example, 
MSHA agrees with commenters that exposed water sprays are not effective 
in freezing weather; however, the Agency has found that at least one, 
or more, option is available for every circumstance. For example, 
enclosing the process equipment or using water sprays are two options 
for controlling dust. Water sprays suppress dust, and enclosures limit 
the amount of dust in the equipment operator's breathing zone. 
Equipment enclosures can be constructed with baffles to slow the 
airflow inside the enclosure, so dust settles more quickly inside the 
enclosure. As another option, a ventilation dust collection system can 
be paired with an equipment enclosure to make both more effective for 
controlling dust. MSHA intends to work with stakeholders, mine 
operators, and the mining community to develop compliance assistance 
materials and share best practices on engineering controls during and 
after the implementation of the final rule.
    MSHA received several comments on the use of administrative 
controls. AIHA emphasized that administrative controls, when used to 
supplement engineering controls, can further reduce exposures, and 
maintain them at or below the PEL (Document ID 1351). Several 
commenters, including mining trade associations, state mining 
associations, and MNM operators, stated that OSHA's 2016 silica rule 
treats engineering and administrative controls as equally effective in 
reducing silica dust exposures and urged MSHA to consider broader use 
of administrative controls and personal protective equipment to achieve 
compliance (Document ID 1428; 1424; 1432; 1455; 1441; 1443).
    MSHA has reviewed the comments and concludes that administrative 
controls are effective in protecting miners from respirable crystalline 
silica exposures when they are used as a supplement to engineering 
controls. For example, NIOSH has co-developed a clothes cleaning system 
that can clean dusty work clothes throughout the workday. This is an 
example of an administrative control that is a safe and effective 
method to remove silica dust from a miner's clothing, reducing 
exposures to respirable crystalline silica. In the final rule, 
administrative controls are secondary to engineering controls because 
administrative controls require significant oversight by mine operators 
to ensure miners understand and follow the prescribed work processes. 
If not properly implemented, understood, or followed, administrative 
controls may not be effective in preventing miners' overexposure to 
respirable crystalline silica.
    MSHA clarifies that administrative controls, except for rotation of 
miners, can be used as a method of compliance if engineering controls 
are not feasible. However, as MSHA discussed in the RFI and in its 
previous 2014 RCMD Standard, engineering controls remain the primary 
means to control all forms of respirable dust, including respirable 
crystalline silica, in the mine atmosphere (84 FR 45454; 65 FR 4214; 68 
FR 10798-10799, 10818).
    For these reasons, final paragraph Sec.  60.11(a) is the same as 
the proposal.

[[Page 28319]]

b. 60.11(b)--Rotation of Miners
    Paragraph (b) prohibits mine operators from using miner rotation as 
an administrative control.
    As noted above, prioritizing engineering controls is consistent 
with accepted industrial hygiene principles, MSHA's existing standards, 
and the Mine Act. In particular, the prohibition against rotation of 
miners to achieve compliance with the PEL is consistent with MSHA's 
June 6, 2005, diesel particulate matter (DPM) final rule (70 FR 32867) 
and its 2014 Coal Dust Rule (79 FR 24813). Under the existing standards 
in the 2014 Coal Dust Rule, MSHA does not permit rotation of miners to 
reduce exposures to coal mine dust if feasible engineering controls are 
in use (79 FR 24909). In the DPM final rule, MSHA prohibited rotation 
of miners to reduce miners' exposure to diesel particulate matter, an 
airborne contaminant that is also a carcinogen. 71 FR 28926; 30 CFR 
57.5060(e).
    MSHA received several comments on the feasibility of prohibiting 
miner rotation. AISI and SSC requested that MSHA permit the use of 
rotation of miners when engineering controls are not feasible (Document 
ID 1426; 1432). Some commenters, including Portland Cement Association, 
NSSGA, Pennsylvania Coal Alliance, Pennsylvania Aggregates & Concrete 
(PACA), BMC, CISC, and Tata Chemicals Soda Ash Partners, LLC, added 
that, because miner rotation historically has been used to lower 
miners' exposures, it should continue to be a part of the hierarchy of 
controls (Document ID 1407; 1448; 1378; 1413; 1417; 1430; 1452; 1364). 
BIA stated that, in their operations, which are already understaffed, 
worker rotation is necessary to ensure miners are not exposed to levels 
above the PEL, particularly if MSHA also discontinues the use of 
respirators as a method of control (Document ID 1422). Other 
commenters, including MSHA Safety Services, Inc., and BIA, stated that 
some mine operators will be substantially impacted by prohibiting miner 
rotation (Document ID 1392; 1422), while a few commenters, including 
NSSGA and IAAP stated that worker rotation is sometimes the only 
feasible control to limit overexposure, such as when miners perform 
periodic or non-routine tasks that do not allow for engineering 
controls (Document ID 1448; 1456).
    UMWA, AFL-CIO, and Black Lung Clinics stated that worker rotation 
could be acceptable to minimize musculoskeletal stress, but not for 
work involving respirable dust or carcinogens, since the practice would 
expose more miners to the hazards (Document ID 1398; 1449; 1410). Black 
Lung Clinics further stated that, because the risk of silica-related 
disease appears to be continuous, rather than associated with a 
threshold exposure, worker rotation does not reduce the risk of disease 
(Document ID 1410).
    However, some commenters disagreed. NVMA stated that miner rotation 
is standard practice when dealing with non-carcinogens and since there 
is not enough data on whether silica exposure alone, as opposed to in 
combination with tobacco use, is the carcinogen causing respiratory 
issues, worker rotation should not be prohibited (Document ID 1441). 
NSSGA provided literature expressing a well-established threshold for 
silicosis and lung cancer and stated that the use of miner rotation to 
reach that limit of exposure should be allowed (Document ID 1448).
    After considering the comments, the final rule prohibits rotation 
of miners. MSHA does not consider it to be an effective control because 
it does not address the root cause of the hazard, requires continuous 
attention and actions on the part of miners and management, and 
increases risks to additional miners. MSHA considers that worker 
rotation, which may be an appropriate control to minimize 
musculoskeletal stress or heat stress, is not an acceptable control for 
silica, which is classified as a Group 1 human carcinogen (IARC, 1997). 
For example, MSHA's existing standards for diesel particulate matter 
prohibit rotation of miners as an acceptable administrative control 
because diesel particulate matter is a probable human carcinogen. 30 
CFR 57.5060. MSHA's risk assessment for the diesel particulate matter 
rule noted the majority of scientific data for regulating exposures to 
carcinogens supports that job rotation is an unacceptable method for 
controlling exposure to both known and probable human carcinogens 
because it increases the number of persons exposed. The Agency 
concludes that the rotation of miners would increase the number of 
miners exposed to the hazard of respirable crystalline silica.
    MSHA considered these comments in light of the Agency's 
longstanding prohibition against rotation of miners as a means of 
compliance for exposures to carcinogens. Commenters did not provide 
specific data in support of their position that mine operators will be 
substantially impacted by the prohibition of miner rotation for 
reducing silica exposure. The intent of this final rule is to provide 
health protection to as many miners as possible from the adverse health 
effects of respirable crystalline silica exposure. The Agency has found 
that a combination of engineering and administrative controls can 
reduce miner exposures to levels at or below the PEL and is feasible 
for mine operators.
    MSHA also received comments requesting clarification on the 
implementation of the prohibition of rotation of miners under the final 
rule. NLA and NSSGA stated that MSHA has not adequately explained the 
proposed prohibition of miner rotation, which creates confusion as to 
whether worker rotation can be used for other purposes and how the 
provision will be enforced (Document ID 1408; 1448). NSSGA further 
stated that, if MSHA does not remove the prohibition in the final rule, 
it should at a minimum, confirm that it will not prohibit miner 
rotation for purposes other than compliance with the PEL, or rotating 
employees to maintain exposure below the action level (Document ID 
1448). Similarly, some commenters, including NLA, AEMA, NMA, and NSSGA 
suggested that MSHA should clarify that miner rotation can still occur 
for legitimate reasons, including avoidance of heat stress or 
musculoskeletal stress (Document ID 1408; 1424; 1428; 1448). SSC asked 
MSHA to explain whether an operator who rotates workers to comply with 
part 62 will be cited if part 60 prohibits the rotation of that miner 
(Document ID 1432).
    MSHA clarifies that this provision is not a general prohibition of 
worker rotation wherever workers are exposed to respirable crystalline 
silica and is intended only to prohibit its use as a compliance method 
for the PEL. It is not intended to bar the use of miner rotation as 
deemed appropriate by the mine operator in activities such as cross-
training or to allow workers to alternate physically demanding tasks 
with less strenuous activities.
    MSHA received comments on the proposed rule's alignment with 
industry standards. MSHA Safety Services, Inc. stated that the rotation 
of miners is accepted by everyone except MSHA (Document ID 1392). 
California Construction and Industrial Materials Association (CalCIMA) 
stated that miner rotation is recommended by NIOSH, and under the OSHA 
respirable crystalline standard, the rotation of employees as an 
administrative control is not prohibited (Document ID 1433). A couple 
commenters, including NSSGA, an individual, and Vanderbilt Minerals, 
LLC, stated that MSHA had mischaracterized the NIOSH recommendations on 
worker rotation

[[Page 28320]]

since, according to the commenters, it selectively used only parts of 
the language in the NIOSH Chemical Carcinogen Policy document to 
justify its position on worker rotation (Document ID 1448; 1367; 1419). 
Because of this alleged mischaracterization, an individual warned that 
MSHA's prohibition against miner rotation is ripe for litigation, not 
because MSHA chose to ban the practice, but because MSHA has not 
sufficiently explained their basis for doing so (Document ID 1367). 
MSHA acknowledges that the Agency may have mischaracterized NIOSH's 
position on worker rotation since its Chemical Carcinogen Policy is 
silent on the issue of worker rotation. In this final rule, MSHA 
clarifies its reference to the NIOSH policy.
    Respirable crystalline silica has long been recognized as a 
carcinogen (IARC, 1997). The Agency considers it more protective of 
miner safety and health to limit the number of miners exposed to 
respirable crystalline silica. MSHA does not consider rotation of 
miners to be an effective control because it does not address the 
source of the hazard. NIOSH's publication entitled ``Current 
Intelligence Bulletin 68: NIOSH Chemical Carcinogen Policy,'' 
recommends that occupational exposures to carcinogens should be reduced 
as much as possible through the hierarchy of controls, most 
importantly, the elimination or substitution of other chemicals that 
are known to be less hazardous and engineering controls (NIOSH, 2017b). 
According to Stewart (2011), ``rotation of workers may reduce overall 
average exposure for the workday but it provides periods of high short-
term exposure for a larger number of workers. As more becomes known 
about toxicants and their modes of action, short-term peak exposures 
may represent a greater risk than would be calculated based on their 
contribution to average exposure.'' Miner rotation is not allowed in 
assessing coal miners' exposure to respirable coal mine dust; coal 
operators must sample occupations or areas, not individual miners, to 
ensure that the environment is controlled. The Agency has determined it 
more protective of miner safety and health to limit the number of 
miners exposed to respirable crystalline silica and require engineering 
controls, supplemented by administrative controls, excluding rotation 
of miners.
    For these reasons, final paragraph Sec.  60.11(b) is the same as 
the proposal.
c. Feasible Engineering Controls
    MSHA received comments regarding the definition of the term 
``feasible'' and the use of feasible engineering controls. NVMA 
requested that MSHA supply a definition for what is ``feasible'' 
(Document ID 1441). Arizona Mining Association stated that the cost-
benefit analysis of the proposed standard is flawed and that many mines 
will face more financial hardship and require far longer implementation 
times than MSHA has anticipated (Document ID 1368). NMA stated that 
engineering controls are not always economically feasible, particularly 
for small businesses (Document ID 1428).
    MSHA clarifies that the courts have interpreted the term 
``feasible'' as meaning `` `capable of being done, executed, or 
effected,' both technologically and economically.'' See Kennecott 
Greens Creek Min. Co. v. Mine Safety & Health Admin, 476 F.3d 946, 957 
(D.C. Cir. 2007) (quoting Am. Textile Mfrs. Inst. v. Donovan, 452 U.S. 
490, 508-09 (1981)). Further, ``MSHA does not need to show that every 
technology can be used in every mine. The agency must only demonstrate 
a `reasonable possibility' that a `typical firm' can meet the 
permissible exposure limits in `most of its operations.' '' Id. at 958 
(quoting Am. Iron & Steel Inst. v. Occupational Safety & Health Admin., 
939 F.2d 975, 980 (D.C. Cir. 1991)).
    Based on MSHA's experience and enforcement and sampling data, 
consideration of the OSHA silica rule, and documentation from NIOSH as 
discussed in Section VII.A. Technological Feasibility, MSHA has 
determined that feasible engineering controls exist for mining 
operations to reduce miners' exposures so that they would not exceed 
the PEL. The Agency has found that feasible engineering controls: (1) 
control crystalline silica-containing dust particles at the source; (2) 
provide reliable, predictable, and consistent protection to all miners 
who would otherwise be exposed to dust from that source; and (3) can be 
monitored. Additionally, MSHA believes this rule is feasible because a 
review of the Agency's available silica sampling data showed that many 
mines are already in compliance with the PEL in Sec.  60.10. Further 
explanation and discussion of the economic feasibility can be found in 
the standalone FRIA document and in the preamble in Section IX. Summary 
of Final Regulatory Impact Analysis and Regulatory Alternatives.
d. Hierarchy of Controls and Respiratory Protection
    MSHA received comments about how the proposed rule related to the 
hierarchy of controls. Several commenters, including NMA, SSC, US 
Silica, AEMA, WVCA, and American Road and Transportation Builders 
Association, stated MSHA should allow mine operators to effectively 
utilize the hierarchy of controls to comply with the proposed silica 
standard (Document ID 1428; 1432; 1455; 1424; 1443; 1353). These 
commenters defined the most effective controls according to the 
hierarchy as: elimination, substitution, engineering, administrative, 
and personal protective equipment (i.e., respirators). Arizona Mining 
Association stated that the hierarchy of controls is recognized world-
wide, including by OSHA, and provides flexibility to allow mine 
operators to make decisions for maintaining safe production (Document 
ID 1368).
    Other commenters stated that respirators should be permitted to be 
used as a method of compliance. WVCA stated that the differences 
between mining environments across the industry mean that while 
engineering controls may be the most effective controls in some mines, 
other controls, like respirators, might protect miners more effectively 
in others (Document ID 1443). US Silica asked MSHA to treat respirators 
as engineering controls (Document ID 1455). IME stated that although 
engineering controls are preferred, it does not make sense to require 
the use of engineering and work practice controls the operator believes 
or knows would be inadequate to meet the PEL, knowing that respirators 
may be more effective for a given task (Document ID 1404). Some 
commenters, including the Arizona Mining Association, NVMA, and US 
Silica, stated that the OSHA standard recognizes the priority of 
engineering controls but allows respiratory protection programs as 
substitutes when engineering controls are not feasible (Document ID 
1368; 1441; 1455; 1353; 1424; 1428).
    Some commenters provided specific situations or conditions in which 
they believe respirators should be used as a method of compliance. 
NSSGA suggested that to prevent mine operators from relying on 
respirators for compliance, MSHA could require operators to outline 
their process for determining when respirators will be used in their 
respiratory protection plans (Document ID 1448). A few commenters, 
including SSC, WVCA, Vanderbilt Minerals, LLC, and IME,

[[Page 28321]]

asked MSHA to allow for NIOSH-approved respirators as a recognized 
control, and not just for instances of unexpected exposures where 
respirator use may be temporary (Document ID 1432; 1443; 1419; 1404). 
The AEMA and NMA suggested adding language as reflected in OSHA's lead 
standard (Document ID 1424; 1428). US Silica stated that MSHA is 
inconsistently recognizing when the use of personal protective 
equipment for compliance purposes may occur since MSHA's occupational 
noise exposure health standards in 30 CFR part 62 allow it, while the 
proposed rule does not (Document ID 1455).
    MSHA also received comments that supported this provision of the 
proposed rule, stating that respirators are an ineffective method of 
compliance. Black Lung Clinics discussed the limitations of 
respirators, stating that facial hair can interfere with the use of 
respirators, respirators do not provide real-time feedback on their 
effectiveness, miners' communication abilities may be impeded, and 
there is uncertainty about whether respirators are actually effective 
in the working environment in coal mines (Document ID 1410). USW stated 
that respiratory protection must never be defined as an engineering 
control because its effectiveness depends on too many variables 
(Document ID 1447). BlueGreen Alliance also supported the prohibition 
on respirators as a method of compliance and suggested that MSHA should 
strengthen the penalties for noncompliance (Document ID 1438).
    MSHA understands that employers across many industries follow the 
NIOSH Hierarchy of Controls in structuring and applying their 
industrial hygiene programs and practices. This reflects a generally 
accepted industrial hygiene principle that recommends the use of 
engineering and administrative controls to implement effective control 
solutions, in the following order (1) elimination; (2) engineering 
controls; (3) administrative controls; and finally, (4) personal 
protective equipment. MSHA recognizes that while elimination of all 
respirable crystalline silica from a mine environment would be the most 
effective means of risk reduction, it is generally not feasible. Under 
the final rule, mine operators are required to use engineering or 
environmental controls as the primary means of maintaining compliance. 
MSHA acknowledges that administrative controls may be necessary to 
further lower exposure levels and encourages mine operators to use such 
controls (with the exclusion of miner rotation).
    MSHA does not agree that respirators are an engineering control. 
Engineering controls provide consistent and reliable protection to 
miners; these controls work independently and verifiably. Engineering 
controls do not depend on individual performance, supervision, or 
intervention, to function as intended, and they can be continually 
evaluated and monitored relatively easily. Unlike PAPRs or supplied-air 
helmets, engineering controls operate at the hazard generation source, 
providing protection against both primary (miners directly involved in 
the task or immediate area) and secondary (miners not directly in the 
task or working in surrounding areas) exposures to the hazard.
    MSHA's enforcement and compliance assistance experience 
substantiate that respirators are not as reliable as engineering 
controls in reducing miners' exposure to toxic substances such as 
respirable crystalline silica. Respirator effectiveness depends on a 
number of factors, including a properly developed and fully implemented 
respiratory protection program; individual performance in donning, 
wearing, and doffing the respirator; and proper supervision to ensure 
that the protection factor is fully achieved.
    In response to comments regarding the use of respirators, MSHA 
amended the final rule, paragraph 60.14(a), to require MNM operators to 
provide respiratory protection for temporary use when miners' exposures 
are above the PEL. For MNM operators, temporary use of respirators is 
required while engineering control measures are being developed and 
implemented, which includes taking corrective actions to ensure miner 
exposures are at or below the PEL. Under the final rule, MNM mine 
operators are also required to use respirators, on a temporary basis, 
when exposures are above the PEL, and it is necessary by the nature of 
work involved (for example, occasional entry into hazardous atmospheres 
to perform maintenance or investigation). The Agency believes this will 
provide MNM miners additional protection during these specific 
circumstances. However, respiratory use under this provision does not 
constitute compliance with the PEL; all exposures above the PEL violate 
the standard. Further discussion on respiratory use in the final rule 
is located in Section 60.14--Respiratory protection.
e. Consensus Standards and Other Guidance
    MSHA received one comment from ISEEE suggesting that the Agency 
incorporate by reference ISO 23875, Cab Air Quality Standard, to assist 
mine operators with compliance for installing and using filtration 
systems to maintain exposures at or below the PEL in operator cabs 
(Document ID 1377). ISO 23875 is an international standard that unifies 
the design, testing, operation, and maintenance of air quality control 
systems for heavy machinery cabs and other operator enclosures. ISEEE 
stated that the standard provides practical and cost-effective 
requirements and testing methods for engineering controls that would 
meet the proposed rule's requirements, given that the desired outcome 
in all cabs that meet the standard's requirements is compliance with 
air quality regulations at the 25 [mu]g/m\3\ level. The commenter added 
that by implementing this consensus standard, it would lead to the 
development of a standardized design that could be mass-produced and 
therefore reduce costs.
    MSHA has reviewed the comment and has determined that an evaluation 
of the costs and benefits for economic and technological feasibility 
would need to be conducted, along with an examination of the costs to 
implement the standard for mine operators. Therefore, the Agency does 
not include the requirements of ISO 23875 in this final rule; however, 
the Agency will evaluate the standard and encourages the use of new 
technologies and consensus standards to improve miner safety and 
health.
    APHA stated that guides prepared by NIOSH for MNM mines and coal 
mines contain helpful illustrations of feasible engineering controls 
that reduce exposure to respirable dust (Document ID 1416). MSHA 
acknowledges that NIOSH and other organizations and agencies have 
published information that may be helpful to mine operators. MSHA has 
worked in partnership with NIOSH in developing this final rule and will 
continue to do so and use information from NIOSH to facilitate 
implementation of the final rule. The Agency encourages mine operators 
to use NIOSH information to ensure that feasible and effective 
engineering controls are installed, used, and maintained.
5. Section 60.12--Exposure Monitoring
    The final rule establishes requirements for exposure monitoring in 
Sec.  60.12. Section 60.12 paragraph (a) establishes the requirements 
for sampling. Paragraph (a)(1) requires mine operators to commence 
sampling by the compliance date to assess the full shift, 8-hour TWA 
exposure of respirable crystalline silica for each miner who is or may 
reasonably be expected to be exposed to respirable crystalline silica.

[[Page 28322]]

Paragraph (a)(2) is restructured from the proposal and states how the 
mine operator shall proceed if the sampling under (a)(1) is: (i) below 
the action level, (ii) at or above the action level, or (iii) above the 
PEL. Paragraph (a)(3) mirrors language in the proposal indicating that 
where the most recent sampling indicates that miner exposures are at or 
above the action level but at or below the PEL, the mine operator shall 
continue to sample within 3 months of the previous sampling. Paragraph 
(a)(4) states that mine operators may discontinue sampling when two 
consecutive samplings indicate that miner exposures are below the 
action level. In a change from the proposal, paragraph (a)(4) also 
specifies that the second sampling must be taken after the operator 
receives the results of the prior sampling but no sooner than 7 days 
after the prior sampling was conducted. Paragraph (b) states that where 
the most recent sampling indicates that miner exposures are above the 
PEL, the mine operator shall sample after corrective actions are taken 
pursuant to Sec.  60.13 until the sampling indicates that miner 
exposures are at or below the PEL. In a change from the proposal, 
paragraph (b) also requires the mine operator to immediately report all 
operator samples above the PEL to the MSHA District Manager or to any 
other MSHA office designated by the District Manager. Paragraph (c) 
requires mine operators to conduct periodic evaluations at least every 
6 months to determine whether changes may reasonably be expected to 
result in new or increased respirable crystalline silica exposures. In 
a change from the proposal, paragraph (c) also requires mine operators 
to conduct an evaluation whenever there is a change in production, 
processes, installation and maintenance of engineering controls, 
installation and maintenance of equipment, administrative controls, or 
geological conditions. Paragraph (c)(1) requires mine operators to make 
a record of the evaluation and the date of the evaluation. In a change 
from the proposal, paragraph (c)(1) also requires the record of the 
evaluation to include the evaluated change and the impact on respirable 
crystalline silica exposure. Paragraph (c)(2) requires mine operators 
to post the record on the mine bulletin board and, if applicable, by 
electronic means, for the next 31 days. Paragraph (d) is unchanged from 
the proposal and includes the requirements for post-evaluation 
sampling. Paragraph (e) includes requirements for how mine operators 
must take samples. Paragraph (e)(1) requires that sampling be performed 
for the duration of a miner's regular full shift and during typical 
mining activities. In a change from the proposal, paragraph (e)(1) 
specifically includes shaft and slope sinking, construction, and 
removal of overburden. Paragraph (e)(2) requires the full-shift, 8-hour 
TWA exposure for miners to be measured based on: (i) personal 
breathing-zone air samples for metal and nonmetal operations and (ii) 
occupational environmental samples collected in accordance with Sec.  
70.201(c), Sec.  71.201(b), or Sec.  90.201(b) of this chapter for coal 
operations. Paragraph (e)(3) includes the requirement for sampling a 
representative fraction of miners and is unchanged from the proposal. 
Paragraph (e)(4), unchanged from the proposal, includes the requirement 
for mine operators to use respirable-particle-size-selective samplers 
that conform to ISO 7708:1995 to determine compliance with the PEL. 
Paragraph (f) is unchanged from the proposal and includes the methods 
of sample analysis. Paragraph (g) is unchanged from the proposal and 
includes the requirements for sampling records.
    The exposure monitoring requirements help facilitate operator 
compliance with the PEL and harmonize MSHA's approach to monitoring and 
evaluating respirable crystalline silica exposures to better protect 
all miners' health. Below is a discussion of the comments received on 
this section and modifications made in response to the comments.
a. Section 60.12(a)--Sampling
    Under the final rule, mine operators are required to commence 
sampling by the compliance date to assess miners' exposures to 
respirable crystalline silica. Samples will be compared to the action 
level and the PEL to determine the effectiveness of existing controls 
and the need for additional controls.
Change in Terminology
    Under the final rule, MSHA removes references to ``baseline 
sampling'' and ``periodic sampling'' and only uses the term 
``sampling''. MSHA also removes proposed Sec.  60.12(a)(2)(i), which 
allowed mine operators to discontinue sampling based on objective data 
or historical sample data, i.e., sampling conducted by the Secretary or 
mine operator sampling conducted within the previous 12 months.
    MSHA determined that the terms ``baseline sampling'' and ``periodic 
sampling'' are no longer needed to describe the sampling requirements 
under the final rule. With the removal of objective data and historical 
sample data, under the final rule, discontinuing sampling is contingent 
upon the results of two consecutive samplings indicating that miner 
exposures are below the action level.
Removal of Objective Data
    Under the final rule, MSHA removes the use of ``objective data'' as 
a method of discontinuing sampling. Proposed paragraph (a)(2) allowed 
operators to discontinue sampling when, among other things, objective 
data indicated that miner exposures were below the action level. As 
discussed earlier, in the proposal, MSHA defined objective data as 
information such as air monitoring data from industry-wide surveys or 
calculations based on the composition of a substance, demonstrating 
miner exposure to respirable crystalline silica associated with a 
particular product or material or a specific process, task, or 
activity. The data must reflect mining conditions closely resembling or 
with a higher exposure potential than the processes, types of material, 
control methods, work practices, and environmental conditions in the 
operator's current operations.
    MSHA received several comments on its proposed use of objective 
data as a means for operators to discontinue periodic sampling, with 
some commenters in support of using objective data and some commenters 
against it. Several commenters, including mining and industry trade 
associations and a state mining association, expressed support for the 
use of objective data, with some commenters noting that it would reduce 
the sampling burden on mine operators (Document ID 1442; 1406; 1408; 
1441; 1424; 1428). Some commenters, including the AEMA, NMA, and 
Vanderbilt Minerals, LLC, stated that objective data more than 12 
months old should be permitted because exposures may not change, or the 
data may still be valid in certain circumstances (Document ID 1424; 
1428; 1419). Several other commenters, including AIHA, UMWA, USW, and 
Appalachian Voices, opposed the use of objective data, with most 
arguing that sampling is more accurate than objective data and that 
such data should not be used to exempt operators from sampling 
(Document ID 1351; 1398; 1447; 1425; 1412). AFL-CIO, NVMA, and Rep. 
Robert C. ``Bobby'' Scott, stated that the term ``objective data'' is 
unclear, too subjective, and capable of being manipulated; that various 
mining aspects could invalidate or skew objective data results; and 
that the proposal's use of objective data is at odds with the Mine 
Act's requirement that newly promulgated health and

[[Page 28323]]

safety standards do not reduce protection for miners (Document ID 1449; 
1441; 1439).
    While the Agency acknowledges that the use of objective data would 
ease operators' sampling burden, MSHA has determined that objective 
data cannot be used to discontinue sampling because it is not likely to 
represent mining conditions closely resembling the processes, types of 
material, control methods, work practices, and environmental conditions 
in the mine operator's current operations. The Agency agrees with 
commenters who stated that sampling is more accurate than using 
objective data and that the use of objective data as a means for 
operators to discontinue sampling, may be too subjective to confirm 
that sample results are below the action level. Furthermore, objective 
data, as defined in the proposal, utilized a historical approach, while 
the collection of samples will more accurately reflect respirable 
crystalline silica concentrations under current mining conditions.
Removal of Operator and Secretary Sampling From Preceding 12 Months
    MSHA also removes the provisions in proposed paragraph (a)(2) 
allowing operators to discontinue sampling when sampling conducted by 
the Secretary or the mine operator within the preceding 12 months 
confirmed that miner exposures were below the action level.
    Some commenters, including SSC, NVMA, Vanderbilt Minerals, LLC, and 
Portland Cement Association, supported the use of past sampling to 
discontinue sampling, noting that many operators already use such data 
to implement their current monitoring programs (Document ID 1432; 1441; 
1419; 1407). However, the UMWA opposed allowing past sampling to be 
used to discontinue sampling (Document ID 1398). The UMWA stated that 
exempting mine operators from sampling based on past sampling fails to 
protect miners from unhealthy levels of respirable crystalline silica 
or ensure that operators are complying with the standard. The UMWA 
recommended that MSHA, not mine operators, regularly sample all miners.
    MSHA agrees that operators cannot rely on samples taken within the 
preceding 12 months prior to the first sampling under the final rule to 
discontinue sampling. This is because past samples may not accurately 
represent miners' current exposures. However, operators still have 
pathways to discontinue sampling; the final rule requires two 
consecutive sample results below the action level that may come from 
operator or MSHA sampling. MSHA will continue to perform its own dust 
samplings as part of its regular health inspections and take necessary 
enforcement actions.
Change in Sampling Compliance Date
    In a change from the proposal, the final rule requires MNM mine 
operators to comply with the requirements and commence sampling within 
24 months of the publication date and requires coal mine operators to 
comply with the requirements and commence sampling within 12 months 
after the publication date.
    Under the proposal, both MNM and coal mine operators would have 
been required to perform the first sampling under this standard within 
the first 180 days (6 months) after the effective date of the final 
rule. MSHA received comments both for and against the proposed 180-day 
compliance period, with many commenters from the MNM mining industry 
stating that it was not enough time and recommending a longer period 
ranging from 1 year to 3 years (Document ID 1408; 1432; 1433; 1417; 
1392). Some commenters, including Portland Cement, SSC, CalCIMA, and 
NLA, stated that providing only 180 days to commence sampling was not 
sufficient because of the limitation of available resources for 
conducting sampling (Document ID 1407; 1432; 1433; 1408). Portland 
Cement, SSC, and AEMA stated that this requirement may not be feasible 
for many operators because of competition for outsourced resources such 
as rental equipment, media, professional services, and laboratory 
sample analysis (Document ID 1407; 1432; 1424). Commenters expressed 
concerns about performing other tasks within the proposed timeframe for 
compliance, including establishing contracts with accredited 
laboratories and other service providers necessary for sampling; 
performing sampling for all miners who may reasonably be expected to be 
exposed to respirable crystalline silica; and designing and 
implementing new engineering controls. These commenters recommended a 
phased timeline similar to OSHA's final requirement in its silica rule 
(which gave employers one year before the commencement of most 
requirements and two years before the commencement of sample analysis 
methods) and MSHA's final requirement in its 2014 RCMD Standard (which 
gave operators 18 months after the rule became effective). The NLA 
stated that small mines are likely to have the greatest difficulty 
competing for resources in a short period of time (Document ID 1408).
    In contrast, some commenters, including AIHA and SKC Inc., stated 
that technologically feasible air sampling and analysis exists to allow 
mine operators to achieve compliance with the PEL using commercially 
available samplers (Document ID 1351; 1366). These commenters stated 
that technologically feasible samplers are widely available, and a 
number of commercial laboratories provide the service of analyzing dust 
containing respirable crystalline silica. Other commenters, including 
AFL-CIO and UMWA, supported requiring first-time sampling within 180 
days of the rule's effective date (Document ID 1449; 1398). Some 
commenters, including Appalachian Voices, Rep. Robert C. ``Bobby'' 
Scott, and Robert Cohen, emphasized the need to implement the final 
rule quickly to protect miners (Document ID 1425; 1439; 1372). 
Appalachian Voices stated that the technologies and practices necessary 
to reduce dust and silica exposure are well-known and that mine 
operators have had ample warning that this rule was forthcoming 
(Document ID 1425).
    Under the proposal, MSHA examined the capacity of laboratories that 
meet the ISO/IEC 17025 standard to conduct respirable crystalline 
sample analyses. MSHA made the preliminary determination that there 
would be sufficient processing capacity to meet the sampling analysis 
schedule and that it would be technologically feasible for laboratories 
to conduct the required sampling analyses (88 FR 44923). MSHA also 
preliminarily determined that the availability of samplers needed to 
conduct the required sampling is technologically feasible (88 FR 
44921). This preliminary determination, however, only examined whether 
sampler technology exists to conduct the respirable crystalline silica 
sampling as required under the proposed rule, not the availability of 
that technology to meet the demands that the final rule would impose.
    MSHA agrees with commenters that the sampling requirements of the 
final rule may create initial increased demand for sampling devices and 
related equipment and services. MSHA understands that there are more 
sampling devices (as well as related services and supplies) currently 
available based on the increased demand resulting from the promulgation 
of the OSHA silica rule in 2016, and MSHA expects that there may be 
another increase in demand because of this final rule. MSHA expects 
that the sampling device market will respond, as it did for OSHA, with 
an increase in the supply of sampling devices to meet the

[[Page 28324]]

increased demand because of this final rule. However, AIHA stated that 
they concur with MSHA that technologically feasible samplers are widely 
available, and a number of commercial laboratories provide the service 
of analyzing dust containing respirable crystalline silica. The AIHA is 
the organization that is responsible for the AIHA-Laboratory 
Accreditation Program (AIHA LAP) that accredits the majority of 
laboratories analyzing industrial hygiene samples. MSHA has also 
identified more AIHA laboratories with respirable crystalline silica 
analysis in their scope of accreditation in 2023 compared to 2022, 
indicating an increase in such capabilities.
    MSHA carefully considered the above information about availability 
of laboratory capacity and sampling devices, including the likely 
increase in demand for such services and devices. MSHA acknowledges 
commenters' concerns about the need for more time to conduct sampling 
and implement necessary engineering controls. All mine operators 
covered by the rule must initiate sampling by the compliance dates, 
potentially creating a peak demand for sampling and analysis around 
those dates. The extended compliance dates permit more time to 
accommodate and prepare for any increase in demand. MSHA expects many 
mine operators will avoid last-minute sampling and begin the sampling 
process earlier than required; thus, the sampling and associated 
analysis will be spread over many months, meaning that any eventual 
peak period for laboratory analysis will be longer and less intense 
(i.e., fewer analyses per month required) than it might be otherwise. 
Additionally, MSHA expects that the extended lead time will be 
sufficient for laboratories to increase their analytical capacity. More 
discussion can be found in Section VII.A. Technological Feasibility. 
Additional discussion of the compliance date requirements can be found 
under Section 60.1--Scope; compliance dates.
Sampling Requirements for New Mines
    A few commenters, including Petsonk PLLC and Appalachian Voices, 
requested that MSHA clarify the sampling requirement for mines that 
begin operations after the rule goes into effect (Document ID 1399; 
1425). Petsonk PLLC suggested amending proposed Sec.  60.12(a)(1) to 
require sampling within 180 days after the rule becomes effective or 
180 days after the mine commences production, whichever occurs later.
    MSHA disagrees with the commenters regarding the need to specify a 
separate sampling schedule for new mines since mine operators would 
have knowledge of the sampling requirements before commencing 
operations. The Agency expects that new mines begin sampling 
immediately upon commencing operations in accordance with the exposure 
monitoring requirements in Sec.  60.12. Coal mine operators are 
required to begin sampling within 12 months of the publication of the 
final rule. Operators of new coal mines that begin operation after the 
12 months must begin sampling upon commencing operations. MNM mine 
operators are required to begin sampling within 24 months of the 
publication date of the final rule. Operators of new MNM mines that 
begin operation after the 24 months must begin sampling upon commencing 
operations.
Reasonably Be Expected
    Under the final rule, mine operators are required to assess the 
exposure of each miner ``who is or may reasonably be expected to be 
exposed to respirable crystalline silica.''
    In the proposal, MSHA requested comments on the Agency's assumption 
that most miners are exposed to at least some level of respirable 
crystalline silica, and on the proposed requirement that these miners 
should be subject to sampling. MSHA described its assumption that most 
occupations related to extraction and processing would meet the 
``reasonably be expected'' threshold for sampling. Further, MSHA 
assumed that some miners may work in areas or perform tasks where 
exposure is not reasonably expected, if at all.
    MSHA received many comments from advocacy organizations, mining and 
industry trade associations, MNM mine operators, labor organizations, 
and a state mining association on the ``reasonably be expected'' basis 
for sampling (Document ID 1398; 1407; 1417; 1419; 1424; 1425; 1428; 
1441; 1445; 1448; 1449). Commenters were generally divided on whether 
most miners are exposed to at least some level of respirable 
crystalline silica. The UMWA agreed with MSHA's assumption and stated 
that most mining occupations would reasonably be expected to be exposed 
to silica and thus meet the threshold for sampling, while some miners 
may not be reasonably expected to be exposed to silica, depending on 
their occupation (Document ID 1398). In contrast, Vanderbilt Minerals, 
LLC stated that it is not reasonable to assume that most miners are 
exposed to at least some level of respirable crystalline silica 
(Document ID 1419). This commenter cited MSHA's Mine Data Retrieval 
System (MDRS) data that shows many mine locations do not have any 
detectable exposure to respirable crystalline silica. Appalachian 
Voices, questioning MSHA's assumption about occupations related to 
extraction and processing meeting the ``reasonably be expected'' 
threshold for sampling, described testimony from several miners who 
worked in non-production positions and were exposed to high levels of 
silica dust (Document ID 1425). This commenter requested expansion of 
the interpretation to include or consider non-production work above 
ground because of the placement of engineering controls, such as return 
air entries near mine offices. Further, other commenters, including 
NSSGA and BMC, requested clarification on what the ``reasonably be 
expected'' threshold means since it was not defined in the proposal 
(Document ID 1448; 1417).
    MSHA has considered these comments. Based on the Agency's 
enforcement and compliance assistance experience and sampling data, the 
final rule retains the language in the proposal. This data considers 
MSHA and operator sampling experience, miners' job tasks and 
occupations, and mining conditions when overexposures are identified 
and need to be corrected. Operators already are expected to know 
whether their miners are exposed or reasonably are expected to be 
exposed to respirable crystalline silica, given coal operators' 
existing sampling regimen (that includes regular sampling) and MNM's 
requirements under Sec. Sec.  56.5002 and 57.5002 to conduct surveys 
(sampling) ``as frequently as necessary to determine the adequacy of 
control measures.'' MSHA believes that most occupations related to 
extraction and processing which generate dust are likely to meet the 
``reasonably be expected'' threshold. However, MSHA clarifies that 
sampling should not be limited to extraction and processing 
occupations; in every instance, the mine operator must determine 
whether exposure to respirable crystalline silica is or may reasonably 
be expected. In the example given by the commenter, miners performing 
above-ground non-production work who were exposed to high levels of 
silica dust would reasonably be expected to be exposed to respirable 
crystalline silica and thus would be required to be sampled. On the 
other hand, MSHA recognizes that some miners are not exposed to 
respirable crystalline silica in day-to-day mining operations, may work 
in areas or perform tasks where respirable crystalline silica exposures 
are not

[[Page 28325]]

reasonably likely, or may work in silica-free environments. Based on 
the Agency's experience, mine operators have familiarity with the 
occupations, work areas, and work activities where respirable 
crystalline silica exposures occur or are most likely to occur. Based 
on this knowledge, MSHA expects that operators will be able to assess 
the threshold conditions for sampling.
    Many commenters stated that MSHA should require an exposure 
``trigger'' level to be used as a basis for conducting sampling. 
Several commenters, including NMA, BMC, NSSGA and AEMA, stated that the 
``reasonably be expected'' threshold for sampling should be associated 
with the action level of 25 [micro]g/m \3\, similar to the OSHA 
standard (Document ID 1428; 1417; 1448; 1424). Some of these commenters 
stated that without a trigger level, even the general public would meet 
the criterion of ``reasonably expected to be exposed'' because the 
proposed requirement is too broad and lacks any meaning in the context 
of a standard.
    Under the final rule, MSHA concludes that an action level trigger 
for initial sampling is not appropriate for mining conditions. The 
extraction and milling of minerals can reasonably be expected to expose 
most miners to some level of respirable crystalline silica. In MSHA's 
experience, dust generation is common in the mining process, and the 
approach in the final rule ensures that mine operators have the 
necessary data and information to understand which miners may be 
exposed to respirable crystalline silica, can make determinations 
regarding the adequacy of existing engineering and administrative 
controls, and can make necessary changes to ensure miners are not 
overexposed.
Sampling
    In the final rule, MSHA requires mine operators to sample within 3 
months of the previous sampling when the most recent sampling indicates 
that miner exposures are at or above the action level but at or below 
the PEL. The most recent sampling could be a first sample under the 
standard, a corrective action sample, a post-evaluation sample, or a 
sample taken by MSHA during its inspections. Sampling must continue 
until two consecutive sample analyses show miners' exposures are below 
the action level. Once this happens, mine operators may discontinue 
sampling for miners whose exposures are represented by these samples, 
until such time that a subsequent MSHA sampling or post-evaluation 
sampling by the mine operator indicates that miners may be exposed at 
or above the action level. MSHA clarifies that during the compliance 
period, the two consecutive samplings needed to discontinue further 
sampling may not begin with an MSHA sampling followed by an operator 
sampling conducted within 3 months of that MSHA sampling; however, it 
may begin with an operator sampling (e.g., the operator's first 
sampling during the compliance period) followed by an MSHA sampling 
conducted within 3 months of that operator sampling. This is because 
the first sampling that operators must conduct during the compliance 
period includes a larger group of miners (i.e., each miner who is or 
may reasonably be expected to be exposed to respirable crystalline 
silica) as compared to the targeted group of miners sampled by MSHA 
during its inspections.
    MSHA received many comments on the proposed frequency of sampling, 
with some commenters stating that the 3-month sampling frequency is too 
frequent and other commenters stating that the sampling is not frequent 
enough. Some MNM mine operators, including SSC and NLA, stated that 
mines with sampling results consistently above the action level but 
below the PEL should not be required to sample every 3 months, and 
instead the frequency should be annual (Document ID 1432; 1408). The 
NVMA stated that the 3-month frequency should be associated with the 
PEL rather than the action level (Document ID 1441). The AISI stated 
that the frequency of sampling should be dictated by the history of 
miner exposures, noting that some miners should not be sampled as 
frequently as others and some miners should not be sampled at all 
(Document ID 1426). Portland Cement Association, NSSGA, BMC, and 
Vanderbilt Minerals, LLC, stated that MSHA should model its sampling 
requirements after OSHA's silica rule, where repeat monitoring is 
conducted within 6 months for exposures above the action level but 
below the PEL and within 3 months for exposures above the PEL (Document 
ID 1407; 1448; 1417; 1419). The AEMA and NMA, stated that follow-up 
sampling should occur no more frequently than every 6 months, as 
proposed in MSHA's Regulatory Alternative #1 (Document ID 1424; 1428). 
The commenters stated that sampling each miner whose exposure is at or 
above the action level but at or below the PEL every 3 months is 
excessive and causes undue burden on mine operators.
    Other commenters, including advocacy organizations and labor 
unions, stated that MSHA's proposed sampling frequency was not enough 
(Document ID 1434; 1447; 1449; 1412; 1445; 1398; 1385). The USW and the 
AFL-CIO stated that the periodic sampling requirement in the proposal 
is not sufficient to assess silica concentrations in mining and prevent 
overexposures and noted the coal mining industry is already required to 
perform quarterly periodic sampling which they believe is not frequent 
enough (Document ID 1447; 1449). An individual stated that MSHA's 
proposed sampling frequency is not aligned with a 2014 NIOSH study 
cited by the Agency that referenced a 2020 report from DOL's Inspector 
General, which recommended more frequent monitoring where there is wide 
variability in silica levels (Document ID 1412). ACLC recommended that 
MSHA require weekly sampling (over multiple shifts) by operators and 
monthly sampling by MSHA inspectors (Document ID 1445). The USW, AFL-
CIO, and Nicholas County Black Lung Association supported more frequent 
sampling by MSHA without suggesting a specific schedule and stated that 
mines should be constantly checking for silica dust, especially where 
continuous mining machine operators and roof bolters are working 
(Document ID 1447; 1449; 1385).
    As commenters noted, OSHA requires a 6-month sampling interval for 
monitoring exposures between the action level and PEL and a 3-month 
interval for monitoring exposures above the PEL. 29 CFR 
1910.1053(d)(3)(iii) and (iv). OSHA explained, ``[i]n general, the more 
frequently periodic monitoring is performed, the more accurate the 
employee exposure profile.'' 81 FR 16766. Accordingly, OSHA noted that 
``[s]electing an appropriate interval between measurements is a matter 
of judgment,'' and determined that the 6-month and 3-month frequencies 
were both ``practical for employers and protective of employees.'' Id. 
MSHA took into account OSHA's approach in developing its final rule.
    MSHA's sampling provisions differentiate between miners based on 
their exposure levels. The sampling provisions require first-time 
sampling of miners exposed or reasonably expected to be exposed to 
respirable crystalline silica, and subsequent sampling of miners 
exposed at or above the action level. In MSHA's experience, ever-
changing mining conditions require a shorter interval between samplings 
to ensure that miners are protected. MSHA's monitoring approach is 
consistent with NIOSH's recommendation to monitor miners' silica 
exposures frequently due to the variability of silica content in mining

[[Page 28326]]

environments (NIOSH, 2014e). The 3-month interval is appropriately 
protective of miners, providing a higher degree of confidence that 
miners will not be exposed to concentrations of respirable crystalline 
silica above the PEL. As discussed in Section VII. Feasibility and 
Section IX. Summary of Final Regulatory Impact Analysis, this sampling 
frequency is technologically and economically feasible for mine 
operators.
    Under the final rule, when exposures are above the PEL, mine 
operators must take immediate corrective actions and sample until 
exposures are at or below the PEL. Like the proposal, the final rule 
does not define a specific sampling frequency above the PEL but 
anticipates that operators will sample upon taking corrective actions 
and sample as frequently as needed until corrective actions have 
resolved the overexposure. Once at or below the PEL, mine operators 
will resume the 3-month schedule.
Two Consecutive Samplings Below the Action Level
    In the final rule, MSHA allows mine operators to discontinue 
sampling when two consecutive samplings indicate that miner exposures 
are below the action level. MSHA believes a short period of time--
within three months--between samples is needed to verify current 
conditions and lack of exposure to respirable crystalline silica. In 
addition, MSHA sampling may indicate exposure levels that require mine 
operators to commence sampling. The Agency also requires operators to 
conduct periodic evaluations at least every 6 months or whenever there 
is a change in production, processes, installation or maintenance of 
engineering controls, installation or maintenance of equipment, 
administrative controls, or geological conditions, to evaluate whether 
the change may reasonably be expected to result in new or increased 
respirable crystalline silica exposures. This will ensure that mine 
operators continue to monitor changes in mining conditions and 
practices that may impact exposure levels and lead to further sampling.
    MSHA received several comments on using two consecutive samples as 
a means of discontinuing sampling requirements. The AIHA and AFL-CIO 
expressed doubt that two samples can provide confidence that a task is 
safe from harmful exposures (Document ID 1351; 1449). A MNM operator 
noted that one or two sample results below the action level do not 
necessarily equate to overall lower exposures and it is likely that 
many two-samples below action level results will occur merely by chance 
(Document ID 1417). In contrast, the NMA agreed with using two 
consecutive samples and stated that OSHA has a similar requirement 
(Document ID 1428). The NMA stated that two samples should be enough to 
confirm lack of exposure in theory and in practice. Other comments from 
professional associations, labor organizations, and a miner health 
advocate questioned whether mine operators should be permanently 
exempted from sampling at all (Document ID 1372; 1377; 1398; 1449; 
1405).
    MSHA agrees with the commenter who stated that two consecutive 
samples should be enough to confirm lack of exposure to respirable 
crystalline silica. In response to the commenters' concern about 
discontinuing sampling, MSHA is confident that the results from two 
consecutive samplings will provide data to confirm that the operator's 
controls are working effectively and that miners' exposures are below 
the action level. MSHA also believes that two consecutive samplings 
below the action level indicate a low probability that, under the 
prevailing conditions, exposure levels exceed the PEL. As such, 
unchanged from the proposal, the final rule includes a requirement for 
two consecutive samples below the action level to discontinue sampling.
    Mine operators may discontinue sampling once two consecutive sample 
analyses show the miners' exposures are below the action level. 
Specifically, in paragraph 60.12(a)(4), to discontinue sampling, the 
second sampling must be taken after the operator receives the results 
of the prior sampling but no sooner than 7 days after the prior 
sampling was conducted. However, MSHA clarifies that the final rule 
includes two scenarios where mine operators are required to resume 
sampling with actual or expected miner exposures at or above the action 
level but below the PEL. First, mine operators must conduct sampling 
within 3 months if sampling by the operator or MSHA indicates that 
miner exposures are at or above the action level but at or below the 
PEL (Sec.  60.12(a)(3)), and mine operators must continue to sample 
until two consecutive samplings indicate that miner exposures are below 
the action level. Second, mine operators must conduct post-evaluation 
sampling if they determine, as a result of their periodic evaluation, 
that miners may be exposed to respirable crystalline silica at or above 
the action level (Sec.  (60.12(d)).
    A miner health advocate stated that an inadequacy of the proposal 
was that it failed to address a situation in which a mine operator took 
multiple samples at the same time (Document ID 1372). The commenter was 
concerned that if one of these samples was under the action level and 
others were over, the operator would choose the sample under the action 
level as the basis for discontinuing sampling.
    MSHA clarifies that, under the final rule, as in the proposal, 
mines that have any miners with silica exposures at or above the action 
level but at or below the PEL are required to continue conducting 
sampling for those miners at or above the action level but at or below 
the PEL in accordance with Sec.  60.12(a).
Minimum Time Between Samplings
    Under final paragraph (a)(4), for the purposes of discontinuing 
sampling, MSHA clarifies that subsequent sampling must be taken after 
the operator receives the results of the prior sampling but no sooner 
than 7 days after the prior sampling was conducted. In response to 
comments, this is a change from the proposed rule.
    In the proposal, MSHA requested comment on whether consecutive 
samples should be taken at least 7 days apart. MSHA received comments 
from AIHA, MCPA, and SSC in response to the minimum time period between 
consecutive samplings (Document ID 1351; 1406; 1432). The MCPA 
expressed concern that requiring 7 days between samplings, combined 
with the time it would take a laboratory to process the samples, could 
result in a miner having to wear a respirator for 3-4 weeks despite 
effective engineering controls being in place (Document ID 1406). This 
commenter also asked if MSHA considered the time it takes to obtain 
sample results from a laboratory. The AIHA stated that consecutive 
samples do not necessarily need to be at least 7 days apart, depending 
on workplace circumstances (Document ID 1351). The SSC stated that a 
time limit between consecutive samples is not needed and stated that 
MSHA has not offered any reason or justification for requiring 7 days 
(Document ID 1432). The ISEEE cautioned that, without a clear 
requirement in the rule, mine operators might take consecutive samples 
only during the most favorable times, i.e., when exposures are 
naturally mitigated by snow or rain (Document ID 1377).
    MSHA reviewed the comments and decided that a minimum time between 
samplings is necessary to ensure that controls are in place and are 
effective in reducing miners' exposures to respirable crystalline 
silica. The final rule requires that, to discontinue sampling, 
subsequent sampling must be taken after the operator receives the 
results of the

[[Page 28327]]

prior sampling but no sooner than 7 days after the prior sampling was 
conducted. This requirement is necessary to prevent situations where 
operators attempt to rely on samples taken too close together that do 
not adequately reflect representative exposure levels during regular 
operations, for instance, while performing a low dust generating task. 
MSHA notes that OSHA's silica final rule provides a 7-day minimum 
period between consecutive samplings under the standard for general 
industry and maritime (29 CFR 1910.1053 (d)(3)(v)) and construction (29 
CFR 1926.1153 (d)(2)(iii)). In addition, MSHA understands that it 
typically takes 2 weeks or less for mine operators to receive sampling 
results from the laboratory. MSHA also clarifies that the 7-day minimum 
interval is not included in Sec.  60.12(b) or between samples not used 
as a basis for discontinuation.
b. Section 60.12(b)--Corrective Actions Sampling
    In the final rule, as in the proposal, where the most recent 
sampling indicates that miner exposures are above the PEL, MSHA 
requires the mine operator to conduct sampling after corrective actions 
are taken and until sampling indicates that miner exposures are at or 
below the PEL. In a change from the proposal, MSHA also requires mine 
operators to immediately report all exposures above the PEL from 
operator sampling to the District Manager or to any other MSHA office 
designated by the District Manager.
    Portland Cement Association recommended that MSHA adopt OSHA's 
standard for corrective actions sampling and suggested that operators 
repeat sampling at 3-month intervals until exposures are at or below 
the PEL (Document ID 1407). An individual expressed concern that the 
proposal does not require a minimum number of full-shift samples to 
validate the effectiveness of corrective actions (Document ID 1412).
    Section 60.13 requires mine operators to take corrective actions 
when sampling results show exposure levels above the PEL. Sampling 
after taking corrective actions provides operators with specific 
information regarding the effectiveness of the corrective actions for 
the mine environment and provides additional data for use in making 
decisions about updating or improving controls. Once sampling shows 
that exposures are at or below the PEL, the Agency requires mine 
operators to conduct repeat sampling within 3-month intervals as long 
as previous sampling results indicate miners' exposures are at or above 
the action level but at or below the PEL. Corrective action sampling is 
required for all samples over the PEL at all mines, including portable 
operations.
    Some commenters, including a miner health advocate and an advocacy 
group, questioned whether citations will be issued if exposures are 
over the PEL, with Hon. Robert C. ``Bobby'' Scott suggesting that MSHA 
incorporate reporting requirements for dust samples (Document ID 1425; 
1439; 1399). AMI Silica, LLC stated that requiring operators to report 
overexposures was a departure from MSHA's current practice and requires 
operators to ``self-incriminate'' (Document ID 1440). However, other 
commenters including labor organizations and a miner health advocate 
requested more MSHA oversight of operator sampling to ensure compliance 
(Document ID 1449; 1398; 1399).
    Under the final rule, MSHA requires mine operators to immediately 
report all exposures above the PEL to the District Manager or to any 
other MSHA office designated by the District Manager. This is 
responsive to comments requesting that the Agency be more actively 
involved in operator sampling and consistent with the approach MSHA 
outlined at a public hearing. Requiring mine operators to report 
sampling results over the PEL will ensure that MSHA is aware of all 
overexposures and can take appropriate action, including compliance 
assistance and enforcement action. Samples indicating concentrations 
over the PEL should be reported immediately, without delay once the 
operator becomes aware of the information, and in accordance with 
guidance from the MSHA District Office. Once MSHA is aware that a 
sample indicates overexposure, the Agency can provide appropriate 
assistance and monitor progress toward abatement of the condition. 
Enforcement actions for samples that are over the PEL, where 
appropriate, will be handled on a case-by-case basis. Enforcement 
practices are discussed in Section VIII.A. General Issues.
c. Section 60.12(c) and (d)--Periodic Evaluation and Post-Evaluation 
Sampling
    Under the final rule, mine operators are required to conduct 
periodic evaluations at least every 6 months or whenever there is a 
change in: production; processes; installation and maintenance of 
engineering controls; installation and maintenance of equipment; 
administrative controls; or geological conditions. Mine operators are 
required to make a record of the periodic evaluation and post it on the 
mine bulletin board and, if applicable, by electronic means, for the 
next 31 days. If the mine operator determines, as a result of the 
periodic evaluation, that miners may be exposed to respirable 
crystalline silica at or above the action level, the mine operator 
shall perform sampling for each of those miners who may be exposed at 
or above the action level.
Periodic Evaluation
    The final rule is modified from the proposal, which would have only 
required operators to conduct periodic evaluations every 6 months. In 
addition to requiring mine operators to conduct periodic evaluations at 
least every 6 months, the final rule also requires mine operators to 
conduct an evaluation whenever there is a change in production, 
processes, installation and maintenance of engineering controls, 
installation and maintenance of equipment, administrative controls, or 
geological conditions.
    MSHA received comments from mining trade associations, labor 
unions, miner health advocates, professional associations, an advocacy 
organization, a black lung clinic, and a federal elected official on 
the proposed semi-annual evaluation requirement. The UMWA, ACOEM, APHA, 
and AEMA stated that mine operators should be constantly conducting 
qualitative evaluations any time a change occurs that may reasonably be 
expected to result in new or increased respirable crystalline silica 
exposures (Document ID 1398; 1405; 1416; 1424). The ISEEE stated that 
it is crucial to regularly reevaluate and address any deficiencies 
across all aspects of the mine site to prevent unnecessary exposures 
and emphasized that conducting timely risk assessments is a standard 
practice in the mining industry (Document ID 1377). The UMWA and AFL-
CIO stated the proposed evaluation requirement could create the 
possibility for miners to be exposed to dangerous levels of silica for 
up to six months (Document ID 1398; 1449). The AEMA believed the 
proposed evaluation requirement would be excessive given the lack of 
frequency with which changes occur (Document ID 1424). The AEMA and NMA 
recommended MSHA require an annual evaluation (Document ID 1424; 1428). 
The NSSGA stated that MSHA should adopt OSHA's requirement to reassess 
respirable crystalline silica exposures whenever there has been a 
change that may reasonably be expected to result in new or additional 
exposures at or above the action level, or when the employer has any 
reason to believe that new or

[[Page 28328]]

additional exposures at or above the action level have occurred (29 CFR 
1910.1053(d)(4) and 29 CFR 1926.1153(d)(2)(iv)) and eliminate the 6-
month qualitative evaluation requirement (Document ID 1448). Finally, 
the AFL-CIO stated mine operators should report significant changes 
that could increase silica concentrations to MSHA, while the Miners 
Clinic of Colorado and a miner health advocate stated that MSHA, not 
mine operators, should be responsible for deciding whether additional 
sampling should be conducted as a result of the qualitative evaluation 
(Document ID 1449; 1418; 1399).
    MSHA agrees with commenters who stated that mine operators should 
be required to conduct a qualitative evaluation when a change occurs to 
help minimize overexposures to respirable crystalline silica. The 
requirement to conduct a qualitative evaluation at least every 6 months 
or whenever a change occurs in production, processes, controls, or 
geological conditions ensures that mine operators are assessing 
changing processes, conditions, and practices that may impact miner 
exposure levels on a regular basis to determine if additional sampling 
is needed. The requirement to conduct an evaluation whenever a change 
occurs is consistent with the existing MNM requirement to conduct 
surveys as frequently as necessary to determine the adequacy of control 
measures (Sec. Sec.  56.5002 and 57.5002), while the minimum 6-month 
requirement is consistent with the underground coal requirement to 
review the ventilation plan every 6 months to assure that it is 
suitable to current conditions (Sec.  75.370(g)). This requirement is 
also consistent with the existing MNM standard for controlling diesel 
particulate matter (DPM), which requires that mine operators monitor as 
often as necessary to effectively determine, under conditions that can 
be reasonably anticipated in the mine, whether the average personal 
full-shift airborne exposure to DPM exceeds the DPM limit (57.5071(a)). 
Under the final rule, mine operators are responsible for conducting 
periodic evaluations. The Agency emphasizes that it will not conduct 
periodic evaluations but may use its enforcement discretion to review a 
mine's records of periodic evaluations, when necessary.
    In response to a comment from a miner health advocate, the final 
rule modifies proposed paragraph(c)(1), which required operators to 
``[m]ake a record of the evaluation and the date of the evaluation.'' 
The commenter stated MSHA should require the record of the evaluation 
to specify all changes that could affect respirable crystalline silica 
exposures and the effect of the changes on exposure levels (Document ID 
1372). MSHA agrees with the commenter who stated the record of the 
evaluation needs to be more informative and responds by requiring the 
record of the evaluation to also include the evaluated change and the 
impact the change has on respirable crystalline silica exposure. The 
additional required data will provide MSHA, mine operators, and miners 
with information on the specific changes that may reasonably be 
expected to result in new or increased respirable crystalline silica 
exposures.
    Unchanged from the proposal, under the final rule, MSHA requires 
mine operators to post the record on the mine bulletin board and, if 
applicable, by electronic means, for 31 days. The NSSGA stated that 
MSHA's requirement to post results on a bulletin board is too 
prescriptive and may cause an issue for operators who do not have a 
bulletin board (Document ID 1448). The final rule includes this 
requirement because it is consistent with MSHA's existing standards and 
gives miners ready access to recent sampling results, providing 
additional accountability for mine operators, and necessary information 
for miners. Also, section 109(a) of the Mine Act requires mines to have 
a bulletin board where information can be posted and shared with miners 
and their representatives. 30 U.S.C. 819(a). For portable operations 
and other operators who prefer to communicate electronically, the final 
rule permits electronic notification in addition to posting the record 
on the bulletin board.
Post-Evaluation Sampling
    Under the final rule, like the proposal, mine operators are 
required to conduct post-evaluation sampling to assess the full shift, 
8-hour TWA exposure of respirable crystalline silica when the results 
of the periodic evaluation show that miners may be exposed to 
respirable crystalline silica at or above the action level.
    MSHA received some comments on the post-evaluation sampling 
proposal from an advocacy organization, a labor union, a federal 
elected official, a medical professional association, and a black lung 
clinic stating that MSHA should require sampling whenever there are any 
changes in mine conditions that could lead to an increased risk of 
respirable crystalline silica exposures (Document ID 1416; 1398; 1439; 
1405; 1418). A miner health advocate stated that mine operators should 
not have the discretion to decide whether miners may be exposed to 
respirable crystalline silica at or above the action level or whether 
they should perform sampling to assess miners' exposure levels as a 
result (Document ID 1399). The same commenter suggested that MSHA 
should provide simple and straightforward triggers that mandate 
sampling, rather than just the requirement to conduct an evaluation 
that might lead to additional sampling.
    Post-evaluation sampling is needed to ensure workers are protected 
from respirable crystalline silica when a change may increase their 
exposure. MSHA believes that mine operators have the most knowledge 
about their mine's operations and conditions. Mine operators are aware 
of the extent and degree of miners' exposures to respirable crystalline 
silica because they have been complying with respirable dust standards 
for over 40 years. Mine operators are also aware of the occupations, 
work areas, and work activities where overexposures to respirable 
crystalline silica are most likely to occur. Further, MSHA believes 
that mine operators will make good-faith efforts to comply with the 
post-evaluation sampling requirements to ensure healthy working 
conditions for miners. The final rule, in a change from the proposal, 
requires mine operators to conduct an evaluation whenever there are 
changes that may reasonably be expected to result in new or increased 
respirable crystalline silica exposures and to require operators to 
maintain more detailed records of the evaluation. These records will 
allow miners, their representatives, and MSHA to hold operators 
accountable for conducting timely and appropriate evaluations and 
required sampling.
d. Section 60.12(e)--Sampling Requirements
    The final rule includes sampling requirements to ensure mine 
operators' respirable crystalline silica monitoring is representative 
of miners' actual exposure levels. The sampling requirements in the 
final rule are the same sampling requirements from the proposal, with a 
few modifications. Each of the sampling requirements is discussed in 
more detail below.
Typical Mining Activities
    In the final rule, MSHA includes shaft and slope sinking, 
construction, and removal of overburden to clarify that these mining 
activities are within the scope of the final rule.
    Several commenters stated the proposal was vague and did not 
clearly specify what ``typical mining activities'' includes. Black Lung 
Clinics, Hon. Robert C. ``Bobby'' Scott, and a miner

[[Page 28329]]

health advocate emphasized that MSHA should ensure the final rule 
covers all aspects of mining operations, including construction and 
development activities (Document ID 1410; 1439; 1372). The American 
Thoracic Society et al. and Appalachian Voices stated it was unclear 
whether slope mining, shaft mining, or exploratory mining were 
considered typical mining activities under the proposal (Document ID 
1421; 1425). The UMWA, Miners Clinic of Colorado, AFL-CIO, and a miner 
health advocate asserted that high silica-cutting activities such as 
blasting, drilling, excavation, cutting overcasts, cutting belt 
channels, and other outby construction should be considered typical 
mining activities under the final rule (Document ID 1398; 1418; 1449; 
1399).
    MSHA agrees with commenters that construction and development 
activities are typical mining activities and clarifies this in the 
final rule. The Agency is aware that many construction and development 
activities generate silica dust, which can lead to respirable 
crystalline silica exposures well above the PEL. MSHA stated at the 
public hearings and clarifies in this final rule that typical mining 
activities include shaft and slope mining, construction, and removal of 
overburden. In June 2022, MSHA implemented its Silica Enforcement 
Initiative (SEI) for MNM and coal mines. The purpose of the SEI is to 
reduce silica exposures in MNM and coal mines, and to provide 
compliance assistance to mine operators, where appropriate. The SEI was 
posted on MSHA's website and discussed with the mining community at 
safety and health conferences and during frequent MSHA stakeholder 
calls.\73\ The SEI specifically addresses silica exposures in shaft and 
slope mining, construction, and removal of overburden. MSHA's 
Enforcement and Educational Field and Small Mine Services staff also 
discussed the SEI with the mining community. In response to commenters' 
examples, MSHA agrees that exploratory mining, and blasting, drilling, 
or cutting rock are all considered typical mining activities.
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    \73\ https://www.msha.gov/safety-and-health/safety-and-health-initiatives/2022/06/08/silica-enforcement-initiative (last accessed 
Jan. 10, 2024).
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    MSHA also clarifies that the existing requirements for respirable 
coal mine dust sampling differ from this final rule's requirements for 
respirable crystalline silica sampling. Under the existing standards 
for respirable coal mine dust sampling, the operator is required to 
sample coal mine dust exposures for specific occupations and areas 
during consecutive normal production shifts where coal mine dust is 
generated from production activities. Under the final rule, MSHA 
interprets construction and development activities as typical mining 
activities subject to respirable crystalline silica sampling, even 
though they may not be considered production activities under the 
requirements for respirable coal mine dust sampling.
Environmental Conditions
    Under the final rule, MSHA does not specify any operating 
conditions or environmental conditions for the purposes of conducting 
respirable crystalline silica sampling.
    In the proposal, MSHA requested comments on whether the Agency 
should specify environmental conditions for sampling. The AEMA, NMA, 
and NSSGA recommended that MSHA not specify typical operating 
conditions or environmental conditions (Document ID 1424; 1428; 1448). 
MSHA Safety Services Inc. stated that it is impossible to predict the 
weather (Document ID 1392). The AFL-CIO cautioned that sampling while 
it is raining--a natural dust suppressant--could skew results, while 
two commenters stated that some mines operate in areas where rain, 
snow, and wind are common and requiring sampling in their absence is 
not feasible (Document ID 1449; 1424; 1428). The NLA stated that 
sampling should be performed under normal or typical operating 
conditions while also emphasizing the need for mine operators to have 
flexibility to determine whether conditions for testing are appropriate 
on any day (Document ID 1408). Black Lung Clinics specified that 
sampling should be conducted at something approaching full production 
for typical tasks (Document ID 1410).
    MSHA recognizes the existence of exposure variability due to 
changing mining operations and environmental conditions and agrees with 
commenters that operators should have the flexibility, within reason, 
to determine what constitutes typical operating conditions and normal 
production levels at their mine. MSHA also agrees with the commenters 
who stated it would be impossible to predict the weather, and thus 
determined that including specific environmental conditions would make 
conducting exposure sampling unduly complicated or at times difficult 
to achieve. MSHA believes that the consistent use of effective 
engineering controls and workplace practices will help reduce exposure 
variability and provide operators with greater confidence that they are 
complying with the PEL. However, MSHA acknowledges that an operator's 
conscientious application and maintenance of all feasible engineering 
controls and workplace practices cannot eliminate exposure variability.
Sampling Device Placement
    Under the final rule, MSHA requires personal breathing-zone air 
samples for MNM operations and requires occupational environmental 
samples collected in accordance with Sec.  70.201I (underground coal 
mines), Sec.  71.201(b) (surface coal mines and surface work areas of 
underground coal mines), or Sec.  90.201(b) (coal miners who have 
evidence of the development of pneumoconiosis) for coal operations.
    MSHA received a few comments on the proposed sampling device 
placement requirements. The AIHA and NMA expressed support for taking 
samples from MNM miners' personal breathing-zones with the latter 
commenter stating that the approach makes sense because MNM miners 
perform various job functions over the course of a shift (Document ID 
1351; 1428). NMA also reasoned that the personal breathing-zone method 
would be preferable for coal miners, rather than the proposed 
occupational environmental sampling, because occupational environmental 
samples may measure several miners performing the same job function 
over the course of a shift and make it more difficult to maintain 
compliance with the PEL. The NVMA stated that providing two different 
sampling methods under the same standard does not make sense and 
suggested MSHA have two separate rulemakings--one for coal mines and 
one for MNM mines (Document ID 1441).
    The Agency reiterates that the final rule creates a uniform 
standard that establishes consistent, industry-wide requirements to 
address the adverse health effects of overexposure to respirable 
crystalline silica for all miners, while still recognizing the 
differences between MNM and coal operations. MSHA believes that the 
consistent use of effective engineering controls and workplace 
practices will help all mines--MNM and coal--maintain compliance with 
the PEL and ensure effective health protection of miners. MSHA 
established the requirements for personal breathing-zone air samples 
for MNM miners and occupational environmental samples for coal miners 
to mirror existing sampling requirements for both industries. These 
sampling methods are tools that, when used appropriately, achieve the 
purpose

[[Page 28330]]

of the Mine Act by identifying the need for additional controls to help 
operators to maintain good air quality.
    A miner health advocate recommended that MSHA require coal mine 
operators to conduct both designated area sampling and designated 
occupation sampling, rather than allowing them the discretion to sample 
either (Document ID 1399). This is a misinterpretation of the rule. 
Final paragraph (e)(2)(ii), which was proposed as paragraph (f)(2)(ii), 
states that ``[t]he full-shift, 8-hour TWA exposure for such miners 
shall be measured based on . . . Occupational environmental samples 
collected in accordance with Sec.  70.201(c), Sec.  71.201(b), or Sec.  
90.201(b) of this chapter for coal operations.'' Sections 70.201(c) and 
71.201(b) both prescribe processes for occupational samples, including 
conversion of designated areas to Other Designated Occupations and 
requirements for how sampling devices must be used and worn. Paragraph 
(e)(2)(ii) does not change operators' discretion under section 
70.201(c) or 71.201(b).
Representative Sampling
    As a general principle, mine operators must accurately characterize 
miners' exposure to respirable crystalline silica. In some cases, this 
requires sampling all exposed miners, while in other cases, sampling a 
``representative'' fraction of miners is sufficient. When a mine 
operator elects to engage in representative sampling, the mine operator 
may take, and submit for analysis, fewer samples. Under this rule, mine 
operators must assess the typical circumstances of each shift and each 
employee to identify miners most at risk for overexposure (for example, 
miners working near where dust collector cleaning or bagging operations 
are taking place) and choose those miners to be ``representative'' for 
sampling purposes. This approach allows mine operators to assess the 
highest likely exposure levels and implement and adjust engineering 
controls to address the highest likely concentrations of respirable 
crystalline silica. MSHA finds that representative sampling is 
sufficient to measure the effectiveness of the engineering controls in 
place. This applies to miners who were not included in the sampling but 
who are represented by the representative samples.
    Under the final rule, like the proposal, where several miners 
perform the same tasks on the same shift and in the same work area, 
mine operators may sample a representative fraction (at least two) of 
these miners. When sampling a representative fraction of miners, mine 
operators are required to select the miners expected to have the 
highest exposure to respirable crystalline silica. For example, 
sampling a representative fraction may involve monitoring the exposure 
of those miners who are closest to the dust source. The sampling 
results for these miners can then be attributed to the remaining miners 
in the group. When miners are performing different tasks, a 
representative sample of miners in the same working area is not 
sufficient to characterize actual exposures, and therefore individual 
samples are necessary.
    MSHA received many comments on the proposed representative sampling 
requirements from MNM mine operators, mining and industry trade 
associations, labor unions, and an industrial hygiene professional 
association, with many commenters supporting the proposal (Document ID 
1398; 1392; 1351; 1407; 1432; 1448; 1417; 1378; 1424; 1419; 1441; 1378; 
1399). The AIHA, Portland Cement Association, SSC, and NSSGA suggested 
that ``similar exposure groups,'' or SEGs, be used as a method to 
determine which miners to sample for representative sampling and to 
reduce operator costs for complying with the exposure monitoring 
requirements in the rule (Document ID 1351; 1407; 1432; 1448). Arizona 
Mining Association stated that mine operators should be allowed to use 
SEGs because the alternative of viewing all miners' exposure as the 
same will result in large cost increases and wasted resources (Document 
ID 1368).
    MSHA did not adopt an SEG approach in the final rule. The Agency 
agrees that mine operators do not always need to conduct sampling for 
every exposed miner. Sampling for a representative fraction of miners 
is similar to the SEG concept because both approaches group miners with 
similar exposure characteristics for the purpose of sampling a smaller 
subset of the group.
    However, there is likely more room for error and misclassification 
using SEGs in mining, especially among smaller mines. SEGs rely on the 
principle of grouping workers into exposure profiles and assessing the 
health risks to those workers based on similar exposure conditions. 
Accordingly, SEGs are commonly established by experienced environmental 
health and safety (EHS) professionals using a combination of exposure 
characteristics, including location, job, task, and equipment used. 
Small mines may not have EHS professionals to correctly define SEGs and 
validate data using proper statistical analyses. There is also risk for 
SEG misclassification if, for example, sampling data is incorrectly 
grouped, not representative of all exposures on all shifts, or not 
collected for the full shift. MSHA is also concerned with variability 
in silica concentrations in the ore body in mining (especially in 
coal). Mines are constantly changing, which means that miners' 
exposures will also change. SEGs would need to be continuously reviewed 
by EHS professionals to ensure that they are correctly defined over 
time.
    The NSSGA, BMC, Pennsylvania Coal Alliance, and AEMA stated that 
samples from miners performing the same task in the same area but on 
different shifts should qualify as representative, with the 
Pennsylvania Coal Alliance stating that MSHA's limitation of samples to 
a single shift is unduly restrictive (Document ID 1448; 1417; 1378; 
1424).
    The final rule requires representative sampling to be restricted to 
the same shift, rather than spanning across multiple shifts. MSHA 
believes that where miners are not performing the same tasks on the 
same shift and in the same work area, representative sampling will not 
adequately characterize actual exposures. In the Agency's experience, 
mine operators may schedule high hazard-generating activities during 
one shift and not others, which would create differences in the 
environment. Humidity, changes in geology, and other environmental 
conditions that might impact sampling results could change across 
shifts, as well; for example, a typically warm and sunny day shift 
versus a cooler shift where temperatures approach or move further from 
the dewpoint. MSHA finds that rather than trying to control for 
potentially significant and unanticipated variables across shifts, 
miner health and safety is better protected if representative sampling 
is confined to the same shift, where conditions are more likely to be 
consistent across miners represented by the sampling. MSHA notes that 
OSHA's requirements for representative sampling for general industry 
and construction are also applied to individual shifts. See 29 CFR 
1910.1053(d)(3)(i).
Sampling Devices: Incorporation of ISO 7708:1995 by Reference
    ISO 7708:1995(E), ``Air quality--particle size fraction definitions 
for health-related sampling,'' First Edition, 1995-04-01, is an 
international consensus standard that defines sampling conventions for 
particle size fractions used in assessing possible health effects of 
airborne particles in the workplace and ambient environment. It defines 
conventions for the inhalable,

[[Page 28331]]

thoracic, and respirable fractions. The ISO standard also provides 
formulas for determining the fractions based on the aerodynamic 
diameter of the particles present. MSHA is incorporating by reference 
ISO 7708:1995 in Sec.  60.12(e)(4) to ensure consistent sampling 
collection by mine operators through the utilization of samplers 
conforming to ISO 7708:1995.
    Under the final rule, MSHA requires mine operators to use 
respirable-particle-size-selective samplers that conform to the ISO 
7708:1995 standard to determine compliance with the PEL. Mine operators 
are allowed to use any type of sampling device for respirable 
crystalline silica sampling, as long as the device is designed to meet 
the characteristics for respirable-particle-size-selective samplers 
that conform to the ISO 7708:1995 standard and, where appropriate, meet 
MSHA permissibility requirements.
    Sampling devices, such as cyclones \74\ and elutriators,\75\ can 
separate the respirable fraction of airborne dust from the non-
respirable fraction in a manner that simulates the size-selective 
characteristics of the human respiratory tract and that meets the ISO 
standard. These devices enable collection of dust samples that contain 
only particles small enough to penetrate deep into the lungs. Size-
selective cyclone sampling devices are typically used in the U.S. 
mining industry. These samplers generally consist of a pump, a cyclone, 
and a membrane filter. The cyclone uses a rapid vortical flow of air 
inside a cylindrical or conical chamber to separate airborne particles 
according to their aerodynamic diameter (i.e., particle size). As air 
enters the cyclone, the larger particles are centrifugally separated 
and fall into a grit pot, while smaller particles pass into a sampling 
cassette where they are captured by a filter membrane that is later 
analyzed in a laboratory to determine the mass of the respirable dust 
collected. The pump creates and regulates the flow rate of incoming 
air. As the flow rate of air increases, a greater percentage of larger 
and higher-mass particles are removed from the airstream, and smaller 
particles are collected with greater efficiency. Adjustment of the flow 
rate changes the particle collection characteristics of the sampler and 
allows calibration to a specified respirable particle size sampling 
definition, such as the ISO criterion.
---------------------------------------------------------------------------

    \74\ A cyclone is a centrifugal device used for extracting 
particulates from carrier gases (e.g., air). It consists of a 
conically shaped vessel. The particulate-containing gas is drawn 
tangentially into the base of the cone, takes a helical route toward 
the apex, where the gas turns sharply back along the axis, and is 
withdrawn axially through the base. The device is a classifier in 
which only dust with terminal velocity less than a given value can 
pass through the formed vortex and out with the gas. The particle 
cut-off diameter is calculable for given conditions.
    \75\ An elutriator is a device that separates particles based on 
their size, shape, and density, using a stream of gas or liquid 
flowing in a direction usually opposite to the direction of 
sedimentation. The smaller or lighter particles rise to the top 
(overflow) because their terminal sedimentation velocities are lower 
than the velocity of the rising fluid.
---------------------------------------------------------------------------

    A cyclone sampler calibrated to operate at the manufacturer's 
specified air flow rate that conforms to the ISO standard can be used 
to collect respirable crystalline silica samples under this final rule. 
MSHA reviewed OSHA's feasibility analysis for its 2016 silica final 
rule and agrees that there are commercially available cyclone samplers 
that conform to the ISO standard and allow for the accurate and precise 
measurement of respirable crystalline silica at concentrations below 
both the action level and PEL (OSHA, 2016a). Cyclone samplers include, 
but are not limited to, the Dorr-Oliver 10-mm nylon cyclone, as well as 
the Higgins-Dewell, GK2.69, SIMPEDS, and SKC aluminum cyclone. Each of 
these cyclones has different operating specifications, including flow 
rates, and performance criteria, but all are compliant with the ISO 
criteria for respirable dust with an acceptable level of measurement 
bias. MSHA's determination is that cyclone samplers, when used at the 
appropriate flow rates, can collect a sufficient mass of respirable 
crystalline silica to quantify atmospheric concentrations lower than 
the action level and meet MSHA's crystalline silica sample analysis 
specifications for samples collected at MNM and coal mines.
    MNM mine operators who currently use a Dorr-Oliver 10 mm nylon 
cyclone can continue to use it at a flow rate of 1.7 L/min, which 
conforms to the ISO standard, to comply with the requirements. For coal 
mine operators, the gravimetric samplers previously used to sample RCMD 
(i.e., coal mine dust personal sampling units (CMDPSUs)) were operated 
at a 2.0 L/min flow rate. Those CMDPSUs can be adjusted to operate at a 
flow rate of 1.7 L/min to conform to the ISO standard.
    The NMA, AEMA, and SKC Inc., noted that samplers other than 
cyclones and elutriators should be considered acceptable under the 
final rule (Document ID 1428; 1424; 1366). A miner health advocate 
stated that when conducting sampling under OSHA requirements, they 
currently use a type of sampler called a ``parallel particle 
impactor,'' or PPI sampler, that meets the ISO 7708:1995 standard 
(Document ID 1375). This commenter stated that there is a disconnect 
between the cyclone samplers mentioned in the proposed rule and the use 
of PPI samplers as an acceptable sampling device, implying that PPI 
samplers are not acceptable because they were not included in the list 
of example samplers that meet the ISO 7708:1995 standard in the 
Sampling Methods section of the proposed rule. This commenter also 
suggested that the PPI sampling device be considered acceptable under 
this final rule. Similarly, the NMA, AEMA and SKC stated that MSHA's 
proposal implies that only cyclone and elutriator type samplers meet 
the specifications for acceptable sampling devices.
    MSHA clarifies that cyclone and elutriator type samplers are not 
the only acceptable sampling devices that can be used to conduct 
sampling for respirable crystalline silica under this rule. In the 
Sampling Methods section of the proposed rule, MSHA included a list of 
example samplers that conform to the ISO 7708:1995 standard. This list 
was not meant to be all-inclusive, but rather provide several examples 
of samplers currently available in the marketplace that conform to the 
ISO 7708:1995 standard (88 FR 44921). As stated above, mine operators 
can use any type of sampling device, as long as it is designed to meet 
the characteristics for respirable-particle-size-selective samplers 
that conform to the ISO 7708:1995 standard and, where appropriate, meet 
MSHA permissibility requirements. MSHA clarifies that under this final 
rule, any sampling device that meets the ISO 7708:1995 particle size 
selective criteria for respirable dust samplers are acceptable for 
respirable crystalline silica sampling, even if the sampler is not 
specifically mentioned in the list of examples. Under the final rule, 
the PPI sampler would be acceptable.
    Several commenters, including labor organizations and a federal 
elected official, noted the need for sampling devices with real-time or 
near real-time sample analysis capabilities for respirable crystalline 
silica (Document ID 1449; 1447; 1398; 1412; 1399; 1439). The AFL-CIO 
stated that one of the most significant items not included in the 
proposal (that was included in the 2014 Coal Dust Rule) was personal 
dust monitoring devices with real-time analysis (Document ID 1449). The 
commenter recommended the adoption of new technology used by the 
domestic or international mining community to better protect miners. An 
individual stated that MSHA should consider and incorporate continuous 
and rapid quartz

[[Page 28332]]

monitoring systems to more appropriately characterize exposures 
(Document ID 1412).
    MSHA is aware of NIOSH's rapid field-based quartz monitoring (RQM) 
approach as an emerging technology. It provides a field-based method 
for providing respirable crystalline silica exposure measurements at 
the end of a miner's shift. With such an end-of-shift analysis, mine 
operators can identify overexposures and mitigate hazards more quickly. 
NIOSH Information Circular 9533, ``Direct-on-filter Analysis for 
Respirable Crystalline Silica Using a Portable FTIR Instrument'' 
provides detailed guidance on how to implement a field-based end-of-
shift respirable crystalline silica monitoring program.\76\ The current 
RQM monitor, however, was designed as an engineering tool specifically 
for quartz in coal mines and has not been used for measurements of 
cristobalite and tridymite. MSHA has determined that the RQM monitor 
lacks tamper-proof components and is susceptible to interferences 
(e.g., in MNM mines) which can affect its accuracy. Thus, the RQM may 
not be used for compliance with the sampling requirements of the final 
rule. MSHA continues to support NIOSH efforts to develop the RQM 
monitor.
---------------------------------------------------------------------------

    \76\ National Institute for Occupational Safety and Health 
(NIOSH). 2022b. Direct-on-filter analysis for respirable crystalline 
silica using a portable FTIR instrument. By Chubb LG, Cauda EG. 
Pittsburgh PA: U.S. Department of Health and Human Services, Centers 
for Disease Control and Prevention, National Institute for 
Occupational Safety and Health, DHHS (NIOSH) Publication No. 2022-
108, IC 9533. https://doi.org/10.26616/NIOSHPUB2022108 (last 
accessed Jan. 10, 2024). The document is intended for industrial 
hygienists and other health and safety mining professionals who are 
familiar with respirable crystalline silica exposure assessment 
techniques, but who are not necessarily trained in analytical 
techniques. It gives general instructions for setting up the field-
based monitoring equipment and software. It also provides case 
studies and examples of different types of samplers that can be used 
for respirable crystalline silica monitoring. Guidance on the use, 
storage, and maintenance of portable IR instruments is also provided 
in the document.
---------------------------------------------------------------------------

    While the current RQM cannot be used for compliance with the 
sampling requirements under this final rule, MSHA encourages mine 
operators to use the RQM as an engineering tool as the Agency believes 
it could assist operators in identifying areas of concern, including 
samples that would be most appropriate for further laboratory analysis. 
MSHA notes that samples taken by operators using the RQM with results 
above the PEL are not subject to the requirements of the final rule 
(i.e., the mine operator need not report them to MSHA, take corrective 
actions, or conduct additional sampling, etc.). MSHA continues to 
support NIOSH efforts to develop the RQM monitor to be used in mines.
    MSHA maintains that analysis of samples using accredited 
laboratories is an accurate and reliable method of determining 
respirable crystalline silica exposures. Accurate laboratory analysis 
is needed as a reference measurement at the beginning and again at the 
end of an initial exposure assessment as well as when completing 
follow-up assessments to validate compliance. However, end-of-shift 
monitoring can reduce the number of samples taken and provide quick 
results that can be used to reduce the expense of more frequent 
sampling and laboratory analysis, during implementation of corrective 
actions, to validate the effectiveness of corrective actions between 
collection of gravimetric samples, and to increase awareness of 
potential overexposures in a timely manner.
Seasonal and Intermittent Mines
    Seasonal and intermittent mines may have less time to conduct 3-
month sampling. Under the rule, all operators, including seasonal and 
intermittent, must conduct initial sampling when commencing operations 
after the listed compliance dates. If that initial sampling is below 
the action level, MSHA believes that, although the operator may wait up 
to 3 months to conduct the next sample, most operators would have an 
incentive to take another sample as soon as practicable under Sec.  
60.12(a) in order to be relieved from the continuing 3-month sampling 
requirements if a second consecutive sample result is below the action 
level. In that situation, the operator would need only to conduct its 
periodic evaluation every six months or when circumstances change 
pursuant to Sec.  60.12(c). If the initial sample is at or above the 
action level and at or below the PEL, all operators would need to take 
a second sample within 3 months, and within every three months after 
that unless they meet the criteria to discontinue sampling. Operators 
that are active during the 3-month period would need to meet these 
sampling deadlines, even if the operator is not active full-time during 
the 3-month period. Once operators have closed for the season, or for 
an extended period (more than 3 months), they would not be expected to 
continue sampling every 3 months. However, when they re-open, if they 
have not met the requirements for discontinuing sampling, they would 
need to start sampling immediately and every three months. MSHA 
encourages operators to work with their District Managers to develop a 
workable sampling schedule that protects miners as this rule intends.
e. Section 60.12 (f)--Methods of Sample Analysis
    The final rule, like the proposal, specifies the methods to be used 
for analysis of respirable crystalline silica samples, including 
details regarding the specific analytical methods to be used and the 
qualifications of the laboratories where the samples are to be 
analyzed.
ISO/IEC 17025 Accreditation
    Mine operators are required to use laboratories that are accredited 
to the International Organization for Standardization (ISO) or 
International Electrotechnical Commission (IEC) (ISO/IEC) 17025, 
``General requirements for the competence of testing and calibration 
laboratories'' with respect to respirable crystalline silica analyses, 
where the accreditation has been issued by a body that is compliant 
with ISO/IEC 17011 ``Conformity assessment--Requirements for 
accreditation bodies accrediting conformity assessment bodies.'' 
Accredited laboratories are held to internationally recognized 
laboratory standards and must participate in quarterly proficiency 
testing for all analyses within the scope of the accreditation.
    The ISO/IEC 17025 standard is a consensus standard developed by 
ISO/IEC and approved by ASTM International (formerly the American 
Society for Testing and Materials). This standard establishes criteria 
by which laboratories can demonstrate proficiency in conducting 
laboratory analysis through the implementation of quality control 
measures. To demonstrate competence, laboratories must implement a 
quality control program that evaluates analytical uncertainty and 
provides estimates of sampling and analytical error when reporting 
samples. The ISO/IEC 17011 standard establishes criteria for 
organizations that accredit laboratories under the ISO/IEC 17025 
standard. For example, the American Industrial Hygiene Association 
(AIHA) accredits laboratories for proficiency in the analysis of 
respirable crystalline silica using criteria based on the ISO/IEC 17025 
and other criteria appropriate for the scope of the accreditation.
    MSHA received a few comments regarding the proposed requirement for 
mine operators to use laboratories accredited to ISO/IEC 17025 where 
the accreditation has been issued by a body that is compliant with ISO/
IEC 17011 from AIHA, NVMA, BMC, and A2LA (Document ID 1351; 1441; 1417; 
1388). AIHA and A2LA stated that they agree

[[Page 28333]]

with MSHA's proposed requirement and BMC stated that they have no 
objection to the proposal. A2LA further stated that relying on 
accreditation for the approval of testing laboratories assures quality, 
technical competence, accuracy, compliance, and international 
recognition. A2LA stated that it provides confidence in the reliability 
of measurement results and supports regulatory compliance.
    Under the final rule, all mine operators will have to use third-
party laboratories accredited to ISO/IEC 17025 to have respirable dust 
samples analyzed for respirable crystalline silica. Many MNM mine 
operators already use third-party laboratories to perform respirable 
crystalline silica sample analyses. For most coal mine operators, using 
a third-party laboratory to analyze respirable crystalline silica 
samples is a new requirement because respirable coal mine quartz 
samples are currently analyzed by MSHA. Under the final rule, coal mine 
operators are responsible for directly monitoring crystalline silica 
(quartz) exposures in addition to coal dust. Requiring all mines to use 
third-party laboratories ensures that sample analysis requirements and 
MSHA enforcement efforts are consistent across all mines.
Analytical Methods for Sampling
    The final rule requires mine operators to ensure that laboratories 
evaluate all samples using analytical methods for respirable 
crystalline silica that are specified by MSHA, NIOSH, or OSHA. These 
are validated methods currently being used by third party accredited 
laboratories for measuring respirable crystalline silica in mine dust 
matrices. MSHA expects that samples collected in MNM mines will be 
analyzed by X-ray diffraction (XRD) and samples collected in coal mines 
will be analyzed by Fourier transform infrared spectroscopy (FTIR).
    MNM samples are currently analyzed by XRD because the XRD method 
can distinguish and isolate respirable crystalline silica for 
measurement, thereby avoiding interference or confounding of respirable 
crystalline silica analysis results. For MNM samples, the methods used 
for respirable crystalline silica sample analysis using XRD include 
MSHA P-2, NIOSH 7500, and OSHA ID-142. All three methods can 
distinguish between the three silica polymorphs.
    MSHA and NIOSH have specific FTIR methods for analyzing quartz in 
coal mine dust. The NIOSH 7603 method is based on the MSHA P-7 method 
which was collaboratively tested and specifically addresses the 
interference from kaolinite clay. Current FTIR methods, however, cannot 
quantify quartz if either of the other two forms of crystalline silica 
(cristobalite and tridymite) are present in the sample. Additional 
steps such as acid treatment can be taken to remove respirable 
crystalline silica interferences from other minerals that can be found 
in mine dust sample matrices. For coal samples, the methods used for 
respirable crystalline silica sample analysis using FTIR include MSHA 
P-7, NIOSH 7602, and NIOSH 7603.
    MSHA received some comments from mining trade associations, a MNM 
mine operator, and a labor union regarding the proposed requirements 
for specified analytical methods (Document ID 1398; 1424; 1417; 1428; 
1443). BMC stated that they have no objection to MSHA's proposed 
provisions and UMWA stated that they are supportive of MSHA's proposed 
requirements. The AEMA, NMA and WVCA cautioned that many minerals 
interfere with the laboratory's analysis of silica and cited a list 
produced by OSHA of 18 mineral types that might interfere. Some of 
these commenters expressed concern that interference could erroneously 
elevate silica sample levels and cause mine operators to spend 
resources on corrective actions that are not needed.
    As discussed above, MSHA expects that samples collected in MNM 
mines will be analyzed by XRD and samples collected in coal mines will 
be analyzed by FTIR. In response to the commenters' concern about 
mineral types that could erroneously elevate silica sample levels, MSHA 
disagrees with the commenters and notes that the OSHA method cited by 
the commenters (i.e., OSHA ID-142) addresses mineral interference and 
is one of the XRD methods that can be used for respirable crystalline 
silica sample analysis under the final rule.
f. Section 60.12 (g)--Sampling Records
    Under the final rule, the mine operator is required to create a 
record for each sample taken that includes the sample date, the 
occupations sampled, and the concentrations of respirable crystalline 
silica and respirable dust. The mine operator is also required to post 
the record and the laboratory report on the mine bulletin board and, if 
applicable, by electronic means, for the next 31 days, upon receipt.
    MSHA received a few comments on the proposed sampling records 
provision. The APHA recommended that MSHA update Sec.  60.12(h) to 
require mine operators to provide a description or data that shows the 
sample was taken during typical mining activities (Document ID 1416). 
The same commenter also recommended that MSHA require the person 
collecting the samples and recording the data to certify the accuracy 
of the records in writing. The Hon. Robert C. ``Bobby'' Scott, The 
American Thoracic Society et al. and AFL-CIO supported greater 
accessibility of records (Document ID 1439; 1421; 1449). Two of these 
commenters also recommended that sampling records be sent to the 
miners' representatives (Document ID 1439; 1449).
    In MSHA's experience, commercial laboratories that produce reports 
for respirable crystalline silica exposures include information on 
sample locations and/or activities being performed. In some cases, the 
name of the person that was sampled is also included. The final rule 
only requires the sampling record to include the date, occupations 
sampled, and concentrations of respirable crystalline silica and 
respirable dust since the laboratory report may contain additional 
information. MSHA believes the elements it requires as part of the 
sampling record provide mine operators and miners with the most 
important pieces of information while balancing concerns about 
recordkeeping burden. As required in Sec.  60.16(b), any sampling 
record that is created may be requested at any time by, and must 
promptly be made available to, miners, authorized representatives of 
miners, or an authorized representative of the Secretary.
6. Section 60.13--Corrective Actions
    The final rule establishes the requirements for corrective actions 
in Sec.  60.13. Section 60.13 paragraph (a) requires mine operators to 
take certain actions when any sampling result indicates that a miner's 
exposure to respirable crystalline silica exceeds the PEL. Paragraph 
(a) has three subparagraphs--(1), (2), and (3). Paragraph (a)(1) 
requires mine operators to make NIOSH-approved respirators available to 
affected miners before the start of the next work shift. In a change 
from the proposal, paragraph (a)(1) specifies that this requirement 
must be made in accordance with Sec.  60.14 (b) and (c). Paragraph 
(a)(2), unchanged from the proposal, requires mine operators to ensure 
that affected miners wear respirators properly for the full shift or 
during the period of overexposure until miner exposures are at or below 
the PEL. Paragraph (a)(3), unchanged from the proposal, requires mine 
operators to immediately take corrective actions to lower the 
concentration of respirable crystalline silica to at or below the PEL. 
Paragraph (b) mirrors language from the

[[Page 28334]]

proposal and specifies the mine operator's responsibility to conduct 
sampling and implement additional or new corrective actions until a 
subsequent sampling result indicates miner exposures are at or below 
the PEL once corrective actions have been taken. Paragraph (c), 
unchanged from the proposal, requires the mine operator to make a 
record of corrective actions and the dates of those actions. Below is a 
detailed discussion of the comments received on this section and 
modifications made in response to the comments.
    MSHA received several comments including an individual who is a 
director at a pulmonary rehab center, advocacy organizations, and a 
miner health advocate, recommending that mine operators stop all 
production work and withdraw miners if samples are above the PEL 
(Document ID 1445; 1395; 1396; 1425; 1394; 1399). Some commenters 
(e.g., AFL-CIO and an individual) suggested MSHA should include an 
upper exposure limit, above which operators would be required to 
withdraw miners, with ACLC suggesting miners be withdrawn at 100 [mu]g/
m\3\ (Document ID 1449; 1367; 1445). Some commenters expressed concern 
that allowing miners to continue working in hazardous dust levels 
violates the Mine Act, with one stating that conditions above the PEL 
should be considered an ``imminent danger'' under section 107(a) of the 
Mine Act.
    MSHA's existing health standards do not require the withdrawal of 
miners when sampling is over the PEL and mine operators are taking 
corrective actions, except in certain circumstances based on the risk 
and exposure to the miner according to section 104(b) of the Mine Act. 
Accordingly, under Sec.  60.13, mine operators must ensure that 
affected miners wear respirators properly for the full shift or during 
the period of overexposure while the mine operators are taking 
immediate corrective actions to lower miner exposures to at or below 
the PEL.
    MSHA received several comments on the use of respirators while 
corrective actions are being taken by the operator. A law firm said 
respirators should be used permanently as a corrective action (Document 
ID 1353). UMWA and Rep. Robert ``Bobby'' Scott opposed the mandatory 
use of respirators and stated that mandating respirator use is 
inconsistent with the Mine Act; UMWA instead supported the voluntary 
usage of respirators as a supplement to engineering controls (Document 
ID 1353; 1398; 1439). USW cautioned that the provision could allow mine 
operators to justify respirator usage on more than a temporary basis 
(Document ID 1447). The UMWA was also concerned that using respirators 
as a mandatory temporary solution might lead to reduced use of 
engineering and environmental methods as the primary means of 
controlling exposures (Document ID 1398). ACLC stated that the language 
is vague and unclear on how long miners will be required to rely on 
respirators while corrective actions are being taken (Document ID 
1445). Further, commenters including advocacy organizations, labor 
organizations, MNM operators, an industry trade association, and a 
medical professional association stated that the final rule needs to 
clarify how long miners are allowed to wear respirators when their 
exposure is over the PEL (Document ID 1404; 1421; 1425; 1432; 1439; 
1440; 1445; 1447; 1449; 1393; 1395; 1396). AFL-CIO stated that 
corrective actions should be strengthened to include actions other than 
respirator use and if sampling shows that there is continued non-
compliance with the PEL there needs to be more significant corrective 
actions taken to ensure that dust concentrations are reduced 
permanently (Document ID 1449; 1353).
    As explained earlier, respirator use is not allowed for compliance. 
Under Sec.  60.13, if sampling shows exposure above the PEL, mine 
operators are required to provide miners with approved respirators 
before the next shift begins, and affected miners must wear respirators 
properly for the full shift or during the period of overexposure until 
miner exposures are at or below the PEL. This provides miners with 
protection from respirable crystalline silica dust and thereby limits 
the serious health effects associated with respirable crystalline 
silica exposures until engineering controls are in place. Mine 
operators must also immediately take corrective actions to lower the 
concentration of respirable crystalline silica to at or below the PEL. 
This approach is consistent with the NIOSH 1995 Criteria Document in 
which NIOSH recommends the use of respirators as an interim measure 
when engineering controls and work practices are not effective in 
maintaining worker exposures at or below the PEL. Under this section, 
MSHA emphasizes that respirators are to be used only while mine 
operators take corrective actions to lower the concentration of 
respirable crystalline silica to at or below the PEL. MSHA clarifies 
that whenever exposures are over the PEL, corrective actions must be 
taken and MSHA must be notified immediately.
    Further, MSHA emphasizes that section 202(h) of the Mine Act, an 
interim standard applicable to underground coal mine operators, 
specifically prohibits operators from using respirators as a substitute 
for engineering controls in the active workings. Section 202(h) of the 
Mine Act provides that ``Respiratory equipment approved by the 
Secretary and the Secretary of Health and Human Services shall be made 
available to all persons whenever exposed to concentrations of 
respirable dust in excess of the levels required to be maintained under 
this chapter. Use of respirators shall not be substituted for 
environmental control measures in the active workings.'' 30 U.S.C. 
842(h). The final rule is consistent with the Mine Act, MSHA's existing 
standards, and case law. See, e.g., Nat'l Min. Ass'n v. Sec'y, U.S. 
Dep't of Lab., 812 F.3d 843, 884 (11th Cir. 2016) (upholding MSHA's 
Lowering Miners' Exposure to Respirable Coal Mine Dust, Including 
Continuous Personal Dust Monitors rule and noting ``MSHA has 
interpreted the statutory command correctly, however, in requiring that 
mine air quality meet the regulatory standard without resort to a 
personal control''). MSHA clarifies that the final rule does not permit 
the use of respirators in lieu of feasible engineering and 
administrative controls.
    MSHA believes the corrective actions provisions are appropriate and 
requires mine operators to make changes to reduce miners' exposures to 
respirable crystalline silica when exposures are above the PEL. MSHA 
clarifies that respirator use is not a corrective action; the 
corrective actions are those actions--such as watering roadways, 
repairing or installing new water sprays, or repairing or installing a 
new dust collection system--that reduce the respirable crystalline 
silica concentration to at or below the PEL. MSHA will determine, on a 
case-by-case basis, the adequacy of the corrective action that must be 
taken immediately and the appropriate timeframe within which it must 
occur. Although each engineering control employed as a corrective 
action is different, mine operators are expected to minimize the time 
spent performing corrective actions and, as a result, the time affected 
miners spend using respirators. Any exposures over the PEL are a 
violation of the standard. Additionally, when engineering controls are 
being developed and implemented as a part of corrective actions, mine 
operators are to continue corrective action sampling. Any operator 
samples over the PEL, including corrective action sampling,

[[Page 28335]]

are to be reported to the District Manager. If sampling continues to be 
over the PEL, the District Manager will take appropriate enforcement 
actions and may provide assistance, depending on the circumstances.
    Once corrective actions have been taken, the mine operator shall 
conduct sampling pursuant to paragraph 60.12(b). The operator will need 
to take additional or new corrective actions until sampling indicates 
miner exposures are at or below the PEL. Further corrective action 
sampling is discussed in Section VIII.B.5. Exposure Monitoring. Once 
corrective actions have been implemented, the mine operator is expected 
to make a record of the corrective actions promptly including the dates 
of the corrective actions. Record keeping is further discussed in 
Section VIII.B.9. Recordkeeping Requirements.
7. Section 60.14--Respiratory Protection
    Section 60.14 expands on the requirements for the use of 
respiratory protection for respirable crystalline silica. Section 60.14 
paragraph (a) addresses MNM mines only. This paragraph requires the 
temporary use of respirators at MNM mines when concentrations of 
respirable crystalline silica are above the PEL. In a change from the 
proposal, the final rule specifies that the requirements in paragraph 
(a) only apply to MNM mines; coal mines are not covered under this 
paragraph--coal mines are addressed under section 60.13 paragraph (a). 
The Agency also removed the term ``non-routine'' from proposed 
paragraph (a).
    Paragraph (b), unchanged from the proposal, applies to all mines 
and addresses circumstances where miners are medically unable to wear 
respirators. Paragraph (c) also applies to all mines and addresses the 
respiratory protection requirements. Paragraph (c)(1), which requires 
mine operators to provide NIOSH-approved respirators to affected 
miners, is unchanged from the proposed rule. Paragraph (c)(2) is 
changed from the proposal and specifies that where approved respirators 
are used mine operators must have a written respiratory protection 
program in accordance with ASTM F3387-19 and lists the mandatory ASTM 
program elements.
    MSHA received many comments regarding the respiratory protection 
provisions, with some commenters supporting the proposal and some 
opposing it. After reviewing all the comments, MSHA concludes that the 
proposed respiratory protection provisions should be retained, with 
some modifications.
a. Section 60.14(a)--Temporary Use of Respirators at Metal and Nonmetal 
Mines
    Final 60.14(a) states that when MNM miners must work in 
concentrations of respirable crystalline silica above the PEL while 
engineering controls are being developed and implemented or it is 
necessary by nature of the work involved, the mine operator shall use 
respiratory protection as a temporary measure. In a change from the 
proposal, MSHA removed the term ``non-routine'' from the paragraph 
heading and clarified that the requirement for temporary use of 
respirators is applicable only to MNM mines.
    MSHA received several comments on the proposed temporary non-
routine use of respirators, with many commenters opposing the proposed 
mandatory use requirement for coal mines. Commenters identified 
difficulties in wearing respirators and stated that coal mine operators 
must comply with existing standards for ventilation and dust control 
plans, which have to be submitted to and approved by MSHA. Other 
commenters expressed concern that there was an absence of a time limit 
for which silica levels over the PEL are permitted.
    Some advocacy organizations and a miner health advocate asked that 
MSHA require mine operators to withdraw miners when sampling indicated 
exposures above the PEL (Document ID 1445; 1395; 1367; 1396; 1425). A 
medical professional also requested that MSHA require operators to 
withdraw miners from hazardous conditions when sampling indicates they 
are exposed to respirable silica above the PEL (Document ID 1394).
    An individual stated that mine construction and coal production, in 
particular, should be excluded from the circumstances in which 
temporary and non-routine use of respirators are allowed (Document ID 
1412). Many commenters including advocacy organizations, black lung 
clinics, miner health advocates, and labor organizations suggested that 
coal miners should be prohibited from working in overexposures while 
using respirators, stating that the working conditions, especially in 
underground coal mines, make it very difficult for miners to 
communicate and work safely while wearing respirators (Document ID 
1372; 1399; 1398; 1447; 1449; 1421; 1393; 1395; 1396; 1402; 1425; 1445; 
1410; 1342; 1363; 1391; 1394). One of the labor organizations noted 
that respirators do nothing to address bystander exposures (Document ID 
1449).
    After considering the comments, MSHA agrees, and clarifies that 
paragraph (a) does not apply to coal mine operators. MSHA determined 
that coal mine operators control silica and coal mine dust through 
their approved ventilation and dust control plans. Underground coal 
mine operators are required to have ventilation plans, which include a 
respirable dust control plan, which must be submitted to and approved 
by MSHA. See 30 CFR 75.370(a)(1). These plans must be revised to 
address any overexposures to airborne contaminants. Surface coal mines 
that have had a dust overexposure are required to develop and implement 
respirable dust control plans that are approved by MSHA. See 30 CFR 
71.300. For those areas of a surface coal mine where methane 
accumulation is a hazard, such as tunnels and other enclosed working 
areas, mine operators are required to dilute airborne contaminants with 
ventilation controls.
    In MSHA's experience, if there are overexposures to respirable 
crystalline silica or coal mine dust, coal mine operators will adjust 
their ventilation and dust controls to address these overexposures. 
MSHA's experience has shown that these adjustments have generally been 
successful in protecting miners from silica and dust exposures without 
the need for respirators and that most conditions can be corrected 
within a day. Additionally, as is currently the case when a respirable 
coal dust overexposure occurs, under the final rule, citations for 
respirable crystalline silica overexposures will require abatement 
through immediate corrective actions before the citation is terminated. 
MSHA sets any citation abatement deadline with the protection of the 
miners as the primary consideration.
    Also, the proposal was a departure from existing standards for coal 
mine operators. Under the existing standards, coal mine operators have 
to provide respiratory protection, but miners did not have to wear 
respirators. Therefore, MSHA has changed this requirement in the final 
rule to apply to MNM mines only for paragraph (a). MSHA reiterates 
under Sec.  60.13(a) that coal mine operators must use respirators when 
sampling indicates that a miner's respirable crystalline silica 
exposure exceeds the PEL.
    Commenters including advocacy organizations, labor organizations, 
MNM operators, an industry trade association, and a medical 
professional association requested that MSHA clarify the meaning of 
``temporary non-routine''

[[Page 28336]]

to specify circumstances and time limitations (Document ID 1393; 1395; 
1396; 1425; 1445; 1447; 1449; 1432; 1440; 1404; 1421; 1409; 1439; 
1364). Some advocacy organizations and a labor organization asked that 
MSHA define ``temporary'' use for coal mines (Document ID 1393; 1395; 
1449). One of the labor organizations noted that, without defined time 
limits, operators could require miners to wear respirators for weeks or 
months (Document ID 1449).
    MSHA agrees with the commenters who stated that the meaning of 
``temporary non-routine'' needed to be clarified. MSHA removed ``non-
routine'' from the paragraph heading for clarity and to be more 
consistent with the existing requirements for MNM mine operators in 
Sec. Sec.  56.5005 and 57.5005. Final paragraph (a) applies only to MNM 
operators, is consistent with the existing requirements for controlling 
exposure to airborne contaminants in Sec. Sec.  56.5005 and 57.5005 and 
is responsive to comments.
    Final paragraph (a)(1) requires respirator use as a temporary 
measure while MNM miners must work in concentrations of respirable 
crystalline silica above the PEL while engineering control measures are 
being developed and implemented. Final paragraph (a)(2) includes a 
clarifying change from the proposal to include an example in the 
existing MNM standard that requires MNM mine operators to use 
respirators in temporary situations when it is necessary by the nature 
of work involved (for example, occasional entry into hazardous 
atmospheres to perform maintenance or investigation) when miners are 
working in concentrations of respirable crystalline silica above the 
PEL. Several existing MSHA standards use the term ``temporary'' 
although the Agency does not specify a time limit. The mining industry 
is familiar with these standards. MSHA expects ``temporary'' to have 
the same meaning as in existing standards--a short period of time.
    Under existing standards, MNM miners can work for reasonable 
periods of time in concentrations of airborne contaminants exceeding 
permissible levels if they are protected by approved respirators when 
developing and implementing engineering control measures or when 
necessary by the nature of work involved. Under these existing MNM 
standards, mine operators who have overexposures and are required to 
provide respiratory protection to miners are issued a citation for the 
overexposure. Generally, if MNM mine operators have a written 
respiratory protection program in place, the citation would be non-
Significant and Substantial.
    MSHA has always intended for miners to work in these conditions 
temporarily and the agency has enforced it as such. The final rule thus 
does not make any substantive changes from the existing standard in 
MNM. The update in language from ``reasonable periods of time'' to 
``temporary'' in the final rule is an update in line with MSHA's 
original intent and as previously noted, with other existing MSHA 
standards. Husch Blackwell (on behalf of the SSC), NSSGA, U.S. Silica, 
and IAAP stated that respirators are the only feasible means of 
protection for certain tasks in mining environments, such as 
housekeeping, working on dust collectors, and bagging operations 
(Document ID 1432; 1448; 1455; 1456). MSHA emphasizes that respiratory 
protection under Sec.  60.14 (a) is required to be temporary. The 
Agency intends for temporary to mean that miners wear respiratory 
protection only for short periods of time; for example, the time 
necessary to conduct maintenance and repair of engineering controls. 
Similar to existing MNM standards, the Agency, under this final rule, 
does not intend that miners will wear respirators for extended periods 
of time. As an example, when a crusher needs maintenance or repair 
after an overexposure resulting from a defective water spray bar, 
miners must wear respiratory protection when performing maintenance or 
conducting repairs to the spray bar. Another example includes when 
miners change defective dust bags that can cause overexposures to 
respirable crystalline silica; when replacing the dust bags, miners 
must wear respiratory protection.
    After reviewing these comments, MSHA revised paragraph (a)(2) to 
provide a clarifying example on when MNM mine operators would 
temporarily use respirators due to the nature of the work involved. 
Under the final rule, the Agency prohibits use of respirator to achieve 
compliance with the PEL. In response to the comment that respirators 
are the only means to achieve compliance for certain mining tasks, MSHA 
has reviewed its sample data and has determined that mine operators are 
generally able to achieve compliance with existing engineering 
controls, supplemented by administrative controls. MSHA is aware that 
certain mining tasks related to maintenance and repair of engineering 
controls will require respiratory protection. However, MSHA anticipates 
that respirator use will be temporary, until controls are repaired and 
effective, and respirator use will not be considered as a means to 
achieve compliance. This clarifying change on the use of respirators 
for certain tasks such as the occasional entry into hazardous 
atmospheres to perform maintenance or investigation, is consistent with 
the Agency's existing standards.
    A joint comment by The American Thoracic Society et al. suggested 
that temporary reliance on respirator use be limited to miners actively 
working at the time it is noted that silica exceeds the PEL, and only 
for as long as it takes to safely shut down operations (Document ID 
1421). The AFL-CIO suggested that MSHA treat respirator use as a 
variance from normal activity, requiring operators to prove when 
respirator use is necessary (Document ID 1449).
    MSHA understands that respirator use under paragraphs (a)(1) and 
(a)(2) will be different depending on the facts and circumstances in 
the MNM mines and that the temporary nature of respirator use will 
depend on the time needed to correct an overexposure. MSHA will 
determine the time required for temporary respirator use on a case-by-
case basis. MSHA emphasizes that the District Manager will be informed 
of all overexposures under 60.12(b). MSHA can take enforcement action, 
including issuing a withdrawal order under 104(b) of the Mine Act, if 
the facts and circumstances at the mine require it.
    An individual stated that the proposed rule rejected respirator use 
as a method of compliance in the preamble to Sec.  60.11 but proposed 
Sec.  60.14 appeared to contradict the prohibition (Document ID 1412). 
The Black Lung Clinics stated there is no real-time feedback for 
determining whether a respirator is effectively reducing exposure 
levels (Document ID 1410) which may provide a false sense of security 
that the miner is protected from cumulative exposures to respirable 
crystalline silica.
    In response, MSHA clarifies that there is not a contradiction 
between Sec.  60.11 and Sec.  60.14. Final rule Sec.  60.11 requires 
engineering controls supplemented by administrative controls to reduce 
exposures. In MSHA's experience, miners who use respirators under a 
respiratory protection program that is in accordance with MSHA's 
standards are protected from cumulative exposures to airborne hazards. 
Final Sec.  60.14(a) additionally requires the use of respirators in 
MNM mines in case of an overexposure; however, MNM mine operators will 
be cited for the overexposure. This is consistent with MSHA's existing 
standards and enforcement practice for MNM mines.

[[Page 28337]]

    Comments from MNM mining operators, mining trade associations, and 
state mining associations suggested that, consistent with the OSHA 
rule, MSHA should allow operators to use respirators as a method of 
compliance where engineering and administrative controls are unable to 
reduce silica levels below the PEL (Document ID 1368; 1424; 1428; 1441; 
1448; 1455). The NMA stated that respirators, including PAPRs, should 
be allowed to be used whenever miners are working in exposures above 
the PEL (Document ID 1428). The Pennsylvania Coal Alliance and 
Vanderbilt Minerals, LLC stated that PAPRs are comfortable to wear for 
long periods and do not restrict breathing (Document ID 1378; 1419). In 
contrast, three labor organizations opposed the use of respirators 
(Document ID 1398; 1447; 1449). These commenters stated that the Mine 
Act forbids respirator use as a mandatory administrative control or as 
a substitute for environmental controls and noted that the proposed 
rule allowed for continued production with respirators in hazardous 
silica dust levels. A medical professional stated that miners should 
always use respirators, to ensure complete protection from respirable 
crystalline silica exposures (Document ID 1375).
    MSHA disagrees with these commenters that respirators should be 
used as a method of compliance or that miners should always use 
respirators. MSHA has determined that respirators cannot be used as a 
method of compliance. Respirators do not provide effective protection 
from overexposures for various reasons that include: (1) without a 
proper fit, dust particles enter the miner's breathing zone; (2) 
inconsistent or incorrect use can compromise the effectiveness of the 
respirator; and (3) respirators can hinder effective communication 
among miners. MSHA has decided that respirators must not be used for 
compliance because they do not address the dust generation at the 
source. Engineering controls are reliable, provide consistent levels of 
protection to many miners, allow for predictable performance levels, 
can be monitored continually, and can remove harmful levels of airborne 
contaminants, including respirable crystalline silica, from the miner's 
environment. However, MSHA recognizes that respirators must be used, on 
a temporary basis, for certain mining tasks.
    MSHA has provided greater health protection for miners by requiring 
(as opposed to making available) use of respirators for coal miners 
when exposed to respirable crystalline silica above the PEL, while 
continuing necessary protection for MNM miners. Also, in Section VII.A. 
Technological Feasibility, MSHA has determined that it is 
technologically feasible for mine operators to achieve the PEL using 
commercially available engineering controls.
    Engineering controls are reliable, provide consistent levels of 
protection to many miners, allow for predictable performance levels, 
can be monitored continually, and can remove harmful levels of airborne 
contaminants, including respirable crystalline silica, from the miner's 
environment.
    The AFL-CIO stated that mine operators should be required to submit 
scenarios where respirators are necessary under limited circumstances 
and if MSHA does not have evidence respirators are needed for a 
particular task, they should not be permitted (Document ID 1449). After 
considering this comment, MSHA has decided not to require MNM mine 
operators to submit scenarios, or plans, for the temporary use of 
respirators because MSHA approval takes time and, in the Agency's 
experience, there are unforeseen circumstances in a mine that may 
require the immediate implementation of engineering controls. When 
overexposures to respirable crystalline silica occur, paragraph 
60.13(a)(3) requires the mine operator to take immediate corrective 
actions to lower concentrations of respirable crystalline silica to at 
or below the PEL. Therefore, requiring mine operators to submit a plan 
and receive MSHA approval before implementing changes would allow 
respirable crystalline silica exposures above the PEL to remain 
uncorrected for longer than necessary, and put miners' health at risk.
b. Section 60.14(b)--Miners Unable To Wear Respirators at All Mines
    The final rule is changed from proposed paragraph 60.14(b). MSHA 
has revised the heading for paragraph (b) to include ``at all mines'' 
so that it is clear that paragraph (b) is applicable to miners unable 
to wear respirators at MNM and coal mines. Paragraph (b)(2) is also 
changed from the proposal to remove ``non-routine.'' This change is 
made to be consistent with the change discussed in paragraph (a). The 
rest of paragraph (b) is unchanged from the proposal. Paragraph (b) 
requires that, upon written determination by a PLHCP that an affected 
miner is unable to wear a respirator, the miner be temporarily 
transferred to work in a separate area of the same mine or to an 
occupation at the same mine where respiratory protection is not 
required. Paragraph (b)(1) states that the affected miner shall 
continue to receive compensation at no less than the regular rate of 
pay in the occupation held by that miner immediately prior to the 
transfer. Paragraph (b)(2) states the affected miner may be transferred 
back to the miner's initial work area or occupation when temporary use 
of respirators is no longer required.
    The USW supported the temporary transfer of miners unable to wear 
respirators (Document ID 1447) while the Arizona Mining Association 
stated that it would be challenging to transfer miners who cannot wear 
respirators to another location or occupation where respirators are not 
needed (Document ID 1368).
    After reviewing the comments, MSHA has determined that no change to 
the proposal is necessary. MSHA believes that it should not be 
difficult for a mine operator to temporarily transfer miners to a 
separate area or occupation to ensure their health and safety. Under 
the rule, the concentration of respirable crystalline silica to which 
the miner is exposed must be controlled through feasible engineering 
and administrative controls; therefore, instances in which a miner is 
transferred because of an inability to wear a respirator should be 
infrequent. Miners may be able to work in other areas of the mine where 
respirable crystalline silica concentrations are under the PEL. 
Furthermore, under paragraph (b)(2) the miner may be transferred back 
to the initial work area or occupation when the limited use of 
respirators is no longer required.
c. Section 60.14(c)--Respiratory Protection Requirements at All Mines
    The final rule is changed from proposed paragraph (c). MSHA has 
revised the heading for paragraph (c) to include ``at all mines'' so 
that it is clear that paragraph (c) is applicable to MNM and coal 
mines. Paragraph (c)(1) is adopted as proposed and requires mine 
operators to provide affected miners with a NIOSH-approved atmosphere-
supplying respirator or NIOSH-approved air-purifying respirator 
equipped with particulate protection classified as 100 series under 42 
CFR part 84 or particulate protection classified as High Efficiency 
``HE'' under 42 CFR part 84.
    Some commenters, including mining and industry trade associations, 
stated that the NIOSH Pocket Guide to Chemical Hazards recommends the 
use of N-, R-, or P-95 and 99 series respirators to lower miners' 
exposures to respirable crystalline silica and suggested MSHA revise 
the final rule to also allow for these respirators

[[Page 28338]]

(Document ID 1407; 1419; 1424; 1428; 1442; 1448). Some mining trade 
associations and MNM mine operators recommended that MSHA specifically 
allow the use of PAPRs, (Document ID 1424; 1428; 1378; 1419; 1452).
    After reviewing comments, MSHA has decided to maintain paragraph 
(c)(1) in the final rule, as proposed. N-, R-, or P-95 and 99 
respirators may provide an appropriate level of filtration when 
properly fitted, worn, and maintained; however, MSHA has observed that 
the structural integrity of these respirators is very easily 
compromised in the harsh mining environment. N-, R-, or P-95 and 99 
respirators are not as durable as other types of air-purifying 
respirators. N-, R-, or P-95 and 99 respirators are easily 
contaminated, damaged, and deformed and must be routinely replaced to 
maintain effectiveness. Also, the N-, R-, or P-95 and 99 respirators do 
not hold their shape or maintain an effective seal when they become 
wet. N-, R-, or P-95 and 99 respirators that are damaged or deformed 
provide little, if any, protection and may offer a false sense of 
security to miners. MSHA recognizes that PAPRs may be more comfortable 
to wear than full-face or half-face, tight-fitting air purifying 
respirators; however, PAPRs are still not as reliable or effective as 
engineering controls and are not a permanent solution. PAPRs add noise 
from the fan and the full-face covering making it difficult for the 
miner to hear or communicate effectively, which could subject the miner 
to hazards while working. They may also reduce the miner's peripheral 
vision and decrease the wearer's situational awareness around equipment 
or other mining hazards. PAPRs, like full-face or half-face, tight-
fitting air purifying respirators, must be worn only as a temporary 
measure in accordance with paragraph 60.14(b).
    MSHA believes that air-purifying respirators classified as 100 
series or High Efficiency under the NIOSH classifications for 
particulate protection will provide the maximum level of protection 
when miners are wearing respirators and are most suitable in protecting 
the health and safety of miners from occupational exposure to 
respirable crystalline silica when exposures are above the PEL.
    Paragraph (c)(2) is modified from the proposal and requires that 
when approved respirators are used, the mine operator must have a 
written respiratory protection program that meets the following 
requirements in accordance with ASTM F3387-19: program administration; 
written standard operating procedures; medical evaluation; respirator 
selection; training; fit testing; maintenance, inspection, and storage. 
The proposal did not specify the requirement for a written respiratory 
protection program or list the mandatory program elements. The language 
in the final rule is consistent with the requirements of ASTM F3387-19, 
Standard Practice for Respiratory Protection, which is incorporated by 
reference.
    MSHA received comments on the incorporation by reference of ASTM 
F3387-19, with some commenters supporting the proposal and some 
commenters opposing it. An industrial hygiene professional association, 
labor organization and a mining related business supported the proposal 
to update the existing respirator protection standard (Document ID 
1351; 1398; 1392). The AIHA and UMWA stated that the proposed 
incorporation by reference of ASTM F3387-19 to amend the Agency's 
respiratory protection program to current and comprehensive 
requirements was appropriate (Document ID 1351; 1398). The AEMA and 
NMA, who opposed the proposal, stated that MSHA should not reference 
the ASTM F3387-19 requirements if the Agency does not allow the use of 
respirators for compliance purposes (Document ID 1424; 1428). 
Vanderbilt Minerals, LLC asserted that incorporating ASTM F3387-19 is 
beyond MSHA's statutory authority and conflicts with the intent of the 
Mine Act (Document ID 1419).
    As discussed in Section II Pertinent Legal Authority, the Mine Act 
requires the Secretary to develop and promulgate improved mandatory 
health or safety standards to prevent hazardous and unhealthy 
conditions and protect the health and safety of the nation's miners. 30 
U.S.C. 811(a). Section 101(a) of the Mine Act gives the Secretary the 
authority to develop, promulgate, and revise mandatory health standards 
to address toxic materials or harmful physical agents. Under Section 
101(a), a standard must protect lives and prevent injuries in mines and 
be ``improved'' over any standard that it replaces or revises. MSHA 
believes the incorporation by reference of ASTM F3387-19 is an 
improvement over the ANSI 1969 standard which it replaces. MSHA's 
incorporation by reference of ASTM F3387-19 is consistent with the Mine 
Act and OMB Circular A-119, ``Federal Participation in the Development 
and Use of Voluntary Consensus Standards and in Conformity with 
Assessment Activities'' (81 FR 4673). The OMB Circular directs agencies 
to use voluntary consensus standards in lieu of government-unique 
standards, except where inconsistent with law or otherwise impractical.
    The AIHA, NMA, and EMA stated that the proposed ASTM F3387-19 
standard's requirements were too prescriptive and asked that MSHA give 
operators the flexibility to select the elements of that standard that 
are most applicable to their own needs and the hazards at their mines 
(Document ID 1451; 1441; 1442). The AFL-CIO expressed concern that mine 
operators would be allowed to determine which parts of the respiratory 
standard they will follow and urged MSHA to require certain components 
(Document ID 1449). The AEMA stated that the final rule should clarify 
whether a specific written respiratory protection program is required 
and under what standards (Document ID 1424). The AEMA also asked for 
more clarity from MSHA on what elements of ASTM F3387-19 will be 
required when respiratory protection for miners is needed.
    The CISC, MSHA Safety Services, Inc., and Tata Chemicals Soda Ash 
Partners, LLC recommended that MSHA align the respiratory protection 
requirements with OSHA's requirements (Document ID 1430; 1392; 1452). 
Draeger Inc. asked that MSHA include in the rule additional specific 
provisions of ASTMF3387-19, such as the breathing gas requirements in 
section 13 of the ASTM F3387-19 standard and wearer seal checks, and 
also suggested that MSHA add requirements to the fit testing procedures 
to include physical movements that are more relevant to low-seam coal 
mines (Document ID 1409).
    The Agency agrees with commenters who expressed that the 
requirements of the respiratory protection program are appropriate, and 
the Agency makes clarifying changes to the requirements in the final 
rule. The Agency has clarified paragraph (c)(2) to state the specific 
respiratory protection program requirements. In paragraph (c)(2), MSHA 
has deleted ``as applicable'' and added that, when respirators are 
used, a mine operator must have a written respiratory protection 
program that meets the following requirements in accordance with ASTM 
F3387-19: program administration; written standard operating 
procedures; medical evaluation; respirator selection; training; fit 
testing; maintenance, inspection, and storage. MSHA has the authority, 
both under the Mine Act and Federal regulatory guidelines, to include 
the incorporation by reference of consensus standards such as ASTM 
F3387-19. The Mine Act specifically requires MSHA to issue improved 
mandatory safety and

[[Page 28339]]

health standards. The incorporation by reference of ASTM F3387-19 is an 
improved standard.
    MSHA received a comment from the MCPA asserting that the medical 
evaluation and fit testing requirements for respirators in ASTM F3387-
19 were too rigorous because there may be situations where a miner 
fails a medical evaluation or fit test simply due to personal desires, 
such as having a beard (Document ID 1406).
    MSHA believes that the medical evaluation and fit testing 
requirements for use of respirators are appropriate because they are 
critical to ensuring proper protection and safe respirator use for 
respirator wearers who are exposed to airborne contaminants. In 
addition, medical evaluations and fit tests are required under MSHA's 
current respiratory protection standard (ANSI Z88.2-1969). Therefore, 
mine operators who have used respirators previously should be familiar 
with these requirements.
    MSHA incorporates by reference this consensus standard for two 
reasons. ASTM F3387-19 reflects current respirator technology and 
accepted effective respiratory protection practices. For example, ASTM 
F3387-19 provides detailed information on respirator selection that is 
based on NIOSH's research and long-standing experience of testing and 
approving respirators for occupational use and OSHA's respiratory 
protection standards. The ASTM F3387-19 standard is prepared and 
maintained by subject matter experts, using a rigorous and well-defined 
process. The standard is reviewed by internationally recognized experts 
and is approved for use only if the appropriate procedures are 
followed. In addition, adopting voluntary consensus standards is 
consistent with OMB Circular A-119.
    MSHA has observed that many operators, especially larger mine 
operators, have already implemented respiratory protection programs 
that meet many of the OSHA requirements, which are substantially 
similar to many requirements in ASTM F3387-19. In response to 
commenters who suggested that MSHA adopt the OSHA respiratory 
protection standards, ASTM F3387-19 references OSHA's respiratory 
standards that include assigned protection factors and maximum use 
concentrations, and fit testing. MSHA believes that the mining industry 
is familiar with many provisions in ASTM F3387-19. MSHA anticipates 
that for many large mine operators, few changes to their respiratory 
protection program may be warranted, whereas small mines may need to 
revise their respiratory protection programs in accordance with the 
requirements in ASTM F3387-19. The program requirements are discussed 
in more detail in Section VIII.D. Updating MSHA Respiratory Protection 
Standards: Incorporation of ASTM F3387-19 by Reference.
Other Comments
    The AIHA stated that respirators should be used only under a 
comprehensive respiratory protection program and under the supervision 
of an industrial hygienist (Document ID 1351). AIHA suggested that MSHA 
should refer to the most recent edition of ASTM's respiratory 
protection standard and not the 2019 edition, which may become obsolete 
by the time the silica standard is adopted.
    According to the Office of the Federal Register, MSHA is required 
to inform the public of the standard to be incorporated and the 
specific edition that the Agency intends to require. In the proposed 
rule, MSHA proposed to incorporate the 2019 edition of ASTM F3387, 
which is the most recent respiratory protection standard. MSHA is 
incorporating by refence ASTM F3387-19 in this final rule. MSHA is 
aware that larger mines may have an industrial hygienist or safety 
specialist administer their respiratory protection program; this 
practice is consistent with, but not required by, the ASTM F3387-19 
standard's requirements for program administration. ASTM F3387-19 
specifies that responsibility and authority for the respirator program 
should be assigned to a single qualified person with sufficient 
knowledge of respiratory protection. Qualifications could be gained 
through training or experience; however, the qualifications of a 
program administrator must be commensurate with the respiratory hazards 
at the mine site.
    The program administrator should have access to and direct 
communication with the site manager about matters impacting worker 
safety and health. ASTM F3387-19 notes a preference that the 
administrator be in the company's industrial hygiene, environmental, 
health physics, or safety engineering department; however, a third-
party entity that meets the standard's requirements may also provide 
this service. ASTM F3387-19 outlines the respiratory protection program 
administrator's responsibilities, specifying that they should include: 
measuring, estimating, or reviewing information on the concentration of 
airborne contaminants; ensuring that medical evaluations, training, and 
fit testing are performed; selecting the appropriate type or class of 
respirator that will provide adequate protection for each contaminant; 
maintaining records; evaluating the respirator program's effectiveness; 
and revising the program, as necessary.
8. Section 60.15--Medical Surveillance for Metal and Nonmetal Mines
    The final rule establishes requirements for medical surveillance 
for MNM mines in Sec.  60.15. Paragraph (a) requires MNM mine operators 
to provide each miner periodic medical examinations performed by a 
PLHCP or specialist, at no cost to the miner. In a change from the 
proposal, under paragraph (a)(2)(iv), MSHA adds that the pulmonary 
function test may also be administered by a pulmonary function 
technologist with a current credential from the National Board for 
Respiratory Care. The rest of paragraph (a) remains unchanged from the 
proposal.
    Paragraph (b) establishes the requirements for each MNM mine 
operator to provide voluntary medical examinations every 5 years to all 
miners employed at the mine or who have already worked in the mining 
industry. In a change from the proposal, new paragraph (b)(1) specifies 
that the voluntary medical examinations must be offered during an 
initial 12-month period. New paragraph (b)(2), the same as proposed 
paragraph (b), requires mine operators to continue to offer voluntary 
medical examinations after the period in paragraph (b)(1) at least 
every 5 years during a 6-month period that begins no less than 3.5 
years and not more than 4.5 years from the end of the last 6-month 
period.
    Paragraph (c) specifies that each mine operator is required to 
provide the medical examinations specified in paragraph (a) to each 
miner who begins work in the mining industry for the first time. In a 
change from the proposal, paragraph (c)(1) requires the initial medical 
examination to take place no later than 60 days after beginning 
employment (instead of 30 days). Paragraphs (c)(2) and (c)(3) remain 
unchanged from the proposal.
    Paragraph (d) specifies the requirements for medical examination 
results. In a change from the proposal, paragraph (d)(1) specifies that 
the medical examination results must be provided from the PLHCP or 
specialist within 30 days of the medical examination. Like the 
proposal, the medical examination results must be provided to the 
miner, and at the request of the miner, to the miner's designated 
physician. In a change from the proposal, the medical examination 
results may also be provided, at the request of the miner, to another

[[Page 28340]]

designee identified by the miner. In a change from the proposal, 
paragraph (d)(2) specifies that within 30 days of the medical 
examination, the mine operator must ensure that the PLHCP or specialist 
also provide the results of chest X-ray classifications to NIOSH, once 
NIOSH establishes a reporting system. Paragraph (e) specifies the 
requirements for the written medical opinion and is unchanged from the 
proposal. Paragraph (f) requires mine operators to maintain a record of 
the written medical opinions received from the PLHCP or specialist 
under paragraph (e) and is unchanged from the proposal.
    MSHA received several comments regarding the medical surveillance 
provisions for MNM mines, offering both support and opposition. The 
PACA, IAAP, and CalCIMA opposed the proposal, stated that the 
requirements were too prescriptive, and asked that MSHA give operators 
more flexibility in implementing medical surveillance programs 
(Document ID 1413; 1456; 1433). A mining-related business owner 
asserted that medical surveillance requirements are not needed, stating 
that there is a lack of silicosis cases in MNM miners (Document ID 
1392).
    Three commenters--an elected federal official, a miner health 
clinic, and a medical association--supported the proposal and asserted 
that the medical surveillance requirements would help MNM miners track 
their respiratory health and mitigate risks for silica-related chronic 
diseases (Document ID 1439; 1418; 1373). Two unions, the AFL-CIO and 
the USW, stated that both MNM and coal miners should be provided with 
the same level of protection and care through their medical 
surveillance programs (Document ID 1449; 1447).
    After reviewing the comments, MSHA concludes that the proposed 
medical surveillance provisions for MNM mines should be retained, with 
some modifications. As discussed in Section V. Health Effects Summary 
and Section VI. Final Risk Analysis Summary of this preamble, many MNM 
mining activities generate silica dust and could lead to respirable 
crystalline silica exposures that result in adverse health effects such 
as silicosis. MSHA agrees with commenters who stated that the medical 
surveillance requirements will provide MNM miners with health 
information that could prevent silica-related diseases and believes it 
is necessary to include the medical surveillance requirements in the 
final rule. The Agency has determined that all MNM miners receive the 
same medical examination protections under the final rule.
    Some commenters requested that the Agency use a risk-based approach 
for medical surveillance. The NMA, NSSGA, AEMA, and SSC urged MSHA to 
adopt OSHA's risk-based medical surveillance framework, which requires 
medical monitoring only for those miners exposed to respirable silica 
above the action level for more than 30 days per year (Document ID 
1428; 1448; 1424; 1432).
    The Agency disagrees with this approach. Unlike OSHA's silica 
standard, the final rule does not include an exposure trigger provision 
because the Agency believes it is important to maintain consistency 
between the medical surveillance requirements for MNM and coal mines to 
ensure all miners have the information necessary for the early 
detection of silica-related disease. The purpose of medical 
surveillance is to provide MNM miners necessary information to 
determine if their health may be adversely affected by exposure to 
respirable crystalline silica and enable miners to take appropriate 
action to stop further disease progression.
    Below is a detailed discussion of the comments received on this 
section and modifications made in response to the comments.
a. 60.15(a)--Medical Surveillance
    Paragraph Sec.  60.15(a) requires that each MNM mine operator make 
medical examinations, performed by a PLHCP or specialist, available to 
each MNM miner, at no cost to the miner. Mine operators must ensure 
that medical examinations follow the requirements under Sec.  
60.15(a)(2)(i)-(iv). In a change from the proposed rule, under 
paragraph (a)(2)(iv), MSHA adds that the pulmonary function test may be 
administered by a pulmonary function technologist with a current 
credential from the National Board for Respiratory Care.
    MSHA received several comments on proposed paragraph 60.15(a). The 
AIHA, AANP, and CertainTeed, LLC supported MSHA's proposal to require 
MNM mine operators to provide MNM miners with medical examinations 
performed by a PLHCP or specialist and agreed with MSHA's broad 
definition of PLHCP (Document ID 1351; 1400; 1423). The BIA and the 
Arizona Mining Association expressed concerns with this requirement and 
asserted that many MNM mines may experience issues with getting access 
to a PLHCP or specialist qualified to perform the examinations 
(Document ID 1422; 1368). The APHA and AOEC advocated for medical 
surveillance to be performed only by physicians who are board-certified 
in occupational medicine or pulmonary medicine, or who have experience 
in silica medical surveillance (Document ID 1416; 1373). Two commenters 
recommended that MNM miners should be able to choose their own health 
care provider (Document ID 1439; 1412). The Arizona Mining Association 
inquired about whether medical examinations may be incorporated within 
the mine operator's health care plans (Document ID 1368).
    After reviewing the comments, MSHA adds under paragraph (a)(2)(iv) 
that the pulmonary function test may be administered by a pulmonary 
function technologist with a current credential from the National Board 
for Respiratory Care. This option will provide a larger pool of 
qualified respiratory care professionals who may administer pulmonary 
function tests.
    MSHA believes that MNM mine operators should not encounter any 
significant issues with identifying and hiring a qualified PLHCP or 
specialist to conduct medical examinations. The final rule provides 
flexibility in the selection of health care professionals. As discussed 
in Sec.  60.1, the final rule allows MNM mine operators more time to 
comply; MNM mine operators will have 24 months after the publication of 
the final rule, rather than 4 months after the publication of the final 
rule as specified in the proposed rule. This additional time addresses 
commenters' concerns about time needed for establishing a medical 
surveillance program.
    The Agency also clarifies that mine operators may give miners the 
option to choose their own health care provider, if the provider meets 
the requirements of this section. As stated in the proposal, a 
qualified PLHCP is an individual whose legally permitted scope of 
practice (i.e., license, registration, or certification) allows that 
individual to independently provide or be delegated the responsibility 
to provide the required health services (i.e., chest X-rays, 
spirometry, symptom assessment, and occupational history). 
``Specialist'' is defined in Sec.  60.2 as an American Board-Certified 
Specialist in Pulmonary Disease or an American Board-Certified 
Specialist in Occupational Medicine.
    MSHA does not require medical examinations in the final rule to be 
performed only by physicians who are board-certified in occupational 
medicine or pulmonary medicine, because PLHCPs may have the knowledge 
and skills to conduct these examinations independently or under

[[Page 28341]]

the supervision of board-certified specialists. MSHA believes this will 
provide mine operators more provider choices and improve accessibility 
to PLHCPs for miners. MSHA also clarifies that medical examinations may 
be integrated into mine operators' health care plans; while noting that 
in such cases, mine operators must ensure that the examinations are 
conducted in accordance with the requirements in Sec.  60.15. The final 
rule ensures that medical examinations are comprehensive and tailored 
to identify and mitigate potential health risks associated with miners' 
occupational exposures to respirable crystalline silica. The final rule 
will ensure that the medical examinations provide MNM miners with 
health surveillance information so that they are aware of the early 
development and advancement of any silica-related disease.
    The Agency received comments regarding the use of NIOSH facilities 
and NIOSH B Readers. The American Industrial Hygiene Association and 
National Coalition of Black Lung and Respiratory Disease Clinics stated 
that MSHA should require MNM operators to use NIOSH-approved facilities 
(Document ID 1351; 1410). However, several commenters, including the 
ACOEM, NLA, NVMA, and NSSGA, expressed concerns about the limited 
availability and geographic distribution of these facilities (Document 
ID 1405; 1408; 1441; 1448). The NMA, Portland Cement Association, and 
AEMA noted that there are only a limited number of B Readers available 
(Document ID 1428; 1407; 1424). The Black Lung Clinics supported MSHA's 
assertion that the availability of digital radiography allows for the 
electronic transmission of chest radiographs to remotely located B 
Readers (Document ID 1410).
    MSHA agrees with commenters who expressed concerns about the 
accessibility of NIOSH-approved facilities, and, like the proposal, the 
final rule does not include a requirement to use such facilities. MSHA 
believes that requiring a NIOSH-certified B Reader to classify chest X-
rays and requiring either a spirometry technician with a current 
certificate from a NIOSH-approved Spirometry Program Sponsor or a 
pulmonary function technologist with a current credential from the 
National Board for Respiratory Care to perform pulmonary function 
tests, will ensure that miners receive the necessary standard of care 
to protect their health while providing broader access to PLHCPs. As 
did OSHA in its 2016 silica final rule (81 FR 16286, 16821), MSHA has 
determined that the number of B Readers in the United States is 
adequate to classify the additional chest X-rays that will be required 
under this rule. In addition, digital X-rays can be transmitted 
electronically to B Readers anywhere in the United States, so this 
requirement will provide operators greater access to B Readers. 
Further, as discussed more below, under Sec.  60.15(d)(2), mine 
operators are required to ensure that, within 30 days of the medical 
examination, the PLHCP or specialist provides the results of chest X-
ray classifications to NIOSH, once NIOSH establishes a reporting 
system.
    In the proposed rule, MSHA solicited comment on whether other 
diagnostic technology, such as high-resolution computed technology 
(CT), should be included in the final rule. The AOEC, APHA, USW, and a 
medical professional urged MSHA to include a low-dose CT scan, either 
as a primary test or if recommended by the examining clinician, because 
such scans are more sensitive than conventional chest radiographs and 
would facilitate earlier detection of disease or dysfunction (Document 
ID 1373; 1416; 1447; 1437). The UMWA cautioned against requiring CT 
scans because they are not as readily available and are more costly 
(Document ID 1409). The American Thoracic Society et al. commented and 
acknowledged the benefits of low-dose chest CT scans for individual 
disease detection but noted that such a requirement might limit 
population-level disease surveillance because of a lack of 
standardization for interpreting CT scans for diagnosing pneumoconiosis 
(Document ID 1421). The AFL-CIO highlighted other initiatives such as 
the Worker Health Protection Program and the Building Trades National 
Medical Screening Program that provide low-dose CT scans through a 
mobile van to serve smaller population centers and suggested that 
similar programs could be created for MNM miners (Document ID 1449).
    MSHA agrees with commenters regarding the cost concerns and limited 
availability of low-dose chest CT scans. MSHA is aware that there are 
increased health risks from higher radiation exposures from screening 
with low dose chest CT scans. MSHA is also aware that ``ultra-low-
dose'' methods for CT scans are available that would subject the miner 
to lower radiation doses than other screening chest CT scans; however, 
this method is not widely available and is therefore not a practical 
resource for mine operators at this time. Also, as a medical 
professional association acknowledged, low-dose chest CT scans do not 
have a standard for the classification of the results, unlike 
classification standards for chest X-rays (Document ID 1421). For the 
reasons above, the final rule does not add CT scans to the medical 
examination requirements in Sec.  60.15(a).
    The Agency received some comments recommending adding testing 
requirements. The Miners Clinic of Colorado and the Black Lung Clinics 
suggested requiring diffusion capacity testing as a pulmonary function 
test (Document ID 1418; 1410). MSHA considered these comments and 
determined that diffusion capacity testing is not as widely available 
as forced vital capacity (FVC) and forced expiratory volume tests 
(i.e., spirometry tests). Spirometry is the most common and widely used 
lung function test. The final rule does not add diffusion capacity 
testing to the medical examination requirements in Sec.  60.15(a).
    MSHA also received comments on tuberculosis testing requirements. 
Commenters--the AOEC, APHA, and the NSSGA--recommended that a test for 
latent tuberculosis be required as an initial test or if recommended by 
the examining PLHCP, noting that it is included in OSHA's silica 
standard (Document ID 1373; 1416; 1448). However, the Portland Cement 
Association argued that testing for tuberculosis is unnecessary 
(Document ID 1407). After considering these comments, MSHA has decided 
not to include a tuberculosis test requirement because it would be 
duplicative of the information provided in the medical and work history 
examination, which requires an assessment of the miner's history of 
tuberculosis under Sec.  60.15(a). The Agency determined that the 
information gathered through the medical and work history examination 
will effectively screen for tuberculosis. In MSHA's experience, 
tuberculosis is not a significant health concern in the MNM mining 
industry.
b. 60.15(b)--Voluntary Medical Examinations
    Final 60.15(b) requires mine operators to provide the opportunity 
to all miners employed at the mine to have the medical examinations 
under 60.15(a). Based on its review of the comments, MSHA has modified 
the language to clarify the timing of medical examinations. Under final 
paragraph (b), MNM mine operators must provide the opportunity for 
miners to receive medical examinations as specified under (b)(1) and 
(b)(2). This applies to all MNM miners who are not new to the mining 
industry. Miners who are new to the industry are required to receive 
medical examinations as specified under paragraph (c).

[[Page 28342]]

    Paragraph (b)(1) requires mine operators to provide medical 
examinations during an initial 12-month period. This change ensures 
that examinations are offered to miners during a 12-month period that 
begins by the compliance date or during a 12-month period that begins 
whenever a new mine commences operation.
    Under paragraph (b)(2), mine operators must provide subsequent 
medical examinations to miners not new to the mining industry at least 
every 5 years after the period in paragraph (b)(1). The medical 
examinations must be available during a 6-month period that begins no 
less than 3.5 years and not more than 4.5 years from the end of the 
last 6-month period. As discussed in Section VII.A. Technological 
Feasibility, MSHA has determined that it is technologically feasible 
for MNM mine operators to provide periodic examinations. Miner 
participation would be voluntary, as is the case for coal miners in 30 
CFR 72.100(b). In the proposal, MSHA solicited comments on possible 
alternative surveillance strategies or schedules, including whether 
each voluntary examination should be mandatory.
    MSHA received many comments about proposed Sec.  60.15(b). Several 
commenters, including the AEMA, NVMA, NSSGA, SSC, and USW, urged that 
the medical examinations remain voluntary in the final rule (Document 
ID 1424; 1441; 1448; 1432; 1447; 1437;1412). The NSSGA asked MSHA to 
clarify that while operators are required to offer workers the option 
of participating in medical surveillance, workers can decline if they 
wish, unless employers require it as a condition of employment. 
(Document ID 1448).
    In response to comments, MSHA emphasizes that while MNM mine 
operators are required to make the medical examinations available, 
miner participation is voluntary. However, MSHA believes mine operators 
should encourage miner participation because medical surveillance is 
crucial for early detection and prevention of silica-related diseases 
to ensure miners' well-being and safety. MSHA expects mine operators to 
include information on medical surveillance in their parts 46 and 48 
training plans. MSHA will provide guidance to mine operators on how 
medical surveillance, as well as other silica requirements in this 
final rule, can best be integrated in their existing training plans.
    MSHA also considered comments supporting different timelines for 
medical surveillance frequency for medical examinations. The American 
Thoracic Society et al. and an industry expert recommended the adoption 
of a 3-year surveillance frequency (Document ID 1421; 1437). ACOEM also 
supported a 3-year frequency and suggested a more frequent timeline 
based on the discretion of the physician (Document ID 1405). The AFL-
CIO stated that the examination frequency should be more than every 5 
years but did not specify an alternative frequency (Document ID 1449). 
The APHA stated that medical examinations every 5 years may not be 
sufficient for all miners, particularly those with health issues or 
early evidence of silica-related diseases and recommended that MSHA 
revise this provision to allow for more frequent examinations if 
recommended by a PLHCP or specialist (Document ID 1416). Arizona Mining 
Association asked MSHA to clarify the required timing for medical 
surveillance examinations (Document ID 1368).
    Some commenters referenced the OSHA standard as a rationale for 
more frequent medical examinations. The AOEC, a medical professional, 
NSSGA, and USW said that all miners should have the same medical 
examination frequency and should follow OSHA's standard of making 
medical examinations available every 3 years (Document ID 1373; 1437; 
1448; 1447). The Portland Cement Association expressed support for 
using OSHA's exposure-based approach if medical surveillance is in the 
final rule, but with a frequency of every 5 years as in MSHA's proposal 
(Document ID 1407).
    After considering the comments, MSHA has determined that the 5-year 
period for voluntary medical examinations is appropriate, after an 
initial examination within a 12-month period starting no later than the 
compliance date or within an initial 12-month period of a new mine 
commencing operations after the compliance date. The 5-year period 
along with the initial examination will provide miners with information 
needed for the timely detection of silica-related diseases. Miners 
should use the information obtained from medical surveillance to 
establish a baseline and make informed decisions regarding their 
health. MSHA does not believe a schedule requiring more frequent 
periodic examinations is necessary. . In the Agency's experience with 
the coal miners' medical surveillance program, 5-year periodic 
examinations are appropriate to provide miners with information needed 
for early detection of silica-related disease. MSHA intends to provide 
miners and mine operators with information and education to help them 
recognize the signs and symptoms of silica related diseases. MSHA 
expects miners will use this information to help inform their decisions 
regarding their medical care. The Agency believes the medical 
examinations under the final rule are comprehensive and will promote 
miners' health and safety.
    The Agency received comments on the timeline in proposed paragraph 
60.15(b). NSSGA and IAAP stated that that prescribing a 6-month period 
when examinations must be offered creates logistical challenges for 
scheduling resources and accounting for miners' work schedules, and 
they urged MSHA not to specify when examinations should be scheduled 
(Document ID 1448; 1456). However, BMC offered support for this 
language, stating that they supported MSHA's provision that mine 
operators must provide medical surveillance to miners no later than a 
specified number of years, but within a certain range (Document ID 
1417).
    MSHA agrees that operators must provide medical surveillance to 
miners employed at the mine on a consistent schedule. However, in 
response to comments, MSHA has modified the language in this paragraph 
to clarify the timing of the voluntary medical examinations. Paragraph 
(b)(1), changed from the proposed rule, requires mine operators to 
provide medical examinations during an initial 12-month period. Under 
paragraph (b)(2), the mine operators must provide medical examinations 
at least every 5 years after the period in paragraph (b)(1). The final 
rule specifies that medical examinations must be available during a 6-
month period that begins no less than 3.5 years and not more than 4.5 
years from the end of the last 6-month period. The Agency believes the 
change in paragraph (b)(1) will provide miners necessary health 
information earlier than under the proposed rule. The final rule will 
ensure miners have early detection of adverse health effects from 
silica exposure. MSHA believes the final rule safeguards miners' 
health, while fostering enhanced preventative and protective measures 
within the mining industry.
    MSHA received comments asking the Agency to clarify how to verify 
whether miners have had previous medical evaluations. NVMA asked for 
clarification about how operators should verify whether a miner new to 
the operator but experienced in the industry has already completed a 
medical examination (Document ID 1441). Other commenters, including the 
USW, recommended that more efforts should be made to encourage 
participation and educate workers (Document ID 1447; 1437). The USW 
further stated that

[[Page 28343]]

MSHA should encourage participation, by reducing barriers such as lack 
of awareness, privacy and medical confidentiality concerns, and the 
fear of retaliation, job loss, loss of potential job advancement, and 
future employment (Document ID 1447).
    In response to the commenter regarding verification of medical 
examinations of newly hired experienced miners, MSHA encourages mine 
operators to work together to determine the completion of prior medical 
examinations without compromising the confidentiality and privacy of 
the miners' health information. MSHA clarifies that, under the final 
rule, mine operators have no obligation to verify whether a newly-hired 
experienced miner had a medical examination.
    MSHA believes that the rule is designed to prioritize the health 
and safety of miners by making medical examinations available to them. 
MSHA requires operators offer medical examinations, ensuring that 
miners are aware, through training, of their availability, purpose, and 
health benefits. MSHA agrees with commenters that fostering an informed 
environment where miners are made aware of the risk of silica exposure 
will encourage miners to take advantage of the availability of medical 
examinations. The final rule is designed to help miners become more 
aware of how medical surveillance can protect them against silica 
risks. In response to commenters' concern about discrimination and 
retaliation, MSHA investigates, in accordance with its responsibility 
under the Mine Act, discrimination complaints to encourage miners to 
exercise their rights under the Mine Act, including the right to 
medical evaluations. 30 U.S.C. 815(c).
c. 60.15(c)--Mandatory Medical Examinations
    Final paragraph (c) requires MNM mine operators to provide a 
mandatory initial medical examination for each MNM miner who is new to 
the mining industry. Under paragraph (c)(1), the mandatory initial 
medical examination must occur no later than 60 days after a miner new 
to the industry begins employment. This is a change from the proposed 
rule, which required the initial medical examination within 30 days. 
Final paragraphs (c)(2) and (3) are unchanged from the proposed rule. 
Under paragraph (c)(2), mine operators are required to provide a 
mandatory follow-up medical examination to the miner no later than 3 
years after the miner's initial medical examination. Final paragraph 
(c)(3) requires that, if a miner's 3-year follow-up medical examination 
shows evidence of pneumoconiosis or decreased lung function, the 
operator provide the miner with another mandatory follow-up medical 
examination with a specialist, as defined in Sec.  60.2, within 2 
years.
    MSHA determined that a 3-year follow-up is appropriate because 
there are some individuals who respond adversely to respirable coal 
mine dust exposure relatively quickly, and it is important to identify 
those individuals early. A 3-year interval at the start of a miner's 
career will provide necessary information for evaluating the results of 
subsequent spirometry tests and final paragraph (c)(1) requires a 
mandatory follow-up examination be given 3 years after the miner's 
initial examination. This is consistent with the 2014 RCMD Standard. 
See 30 CFR 72.100.
    MSHA received comments on mandatory medical examinations. A couple 
of commenters, including BMC and AOEC, offered support for mandatory 
medical examinations, with some stating that medical examinations 
should be a mandatory requirement for both new and existing miners 
(Document ID 1417; 1373). MCPA opposed mandatory examinations even for 
new miners, stating that participation in medical surveillance is a 
personal choice that should be left up to each miner (Document ID 
1406). NLA stated that making medical examinations mandatory for new 
miners would make it difficult to retain new hires (Document ID 1408).
    NSSGA, IAAP, and BMC stated that MSHA should not prohibit operators 
from making participation in medical surveillance a mandatory condition 
of employment, if the mine operator believes mandatory participation is 
warranted (Document ID 1448; 1456; 1417). Some commenters, including 
USW, were opposed to mine operators mandating medical examinations as a 
condition of employment (Document ID 1447; 1437; 1412). One commenter 
emphasized that miners could be terminated for declining to visit an 
operator's selected PLHCP (Document ID 1412). The Brick Industry 
Association stated that if participation in a medical surveillance 
program is a condition of employment, companies will not be able to 
staff their operations (Document ID 1422).
    Arizona Mining Association requested clarification on whether 
medical surveillance services are mandatory or are just required to be 
made available to the miners upon request. (Document ID 1368). PACA, 
IAAP, and NSSGA asked MSHA to clarify whether operators can make 
medical surveillance mandatory, and whether operators may conduct more 
extensive medical surveillance than required under the proposed rule 
(Document ID 1413; 1456; 1448). BMC asked if operators can make medical 
examinations mandatory as long as they meet MSHA's minimum medical 
surveillance requirements (Document ID 1417).
    In response to these comments, MSHA notes that it is aware that 
some mine operators already have mandatory health screening as part of 
their employment policies. MSHA is also aware that some operators 
require periodic health examinations as part of their industrial 
hygiene practices. As a result, mandatory medical examinations may not 
be new for some mine operators. Many operators make participation in 
medical surveillance a mandatory condition of employment as a part of 
their overall safety and health program for their workforce. In 
response to comments, operators can conduct more extensive medical 
surveillance and can make medical examinations mandatory as long as 
they meet MSHA's minimum medical surveillance requirements. The Agency 
does not intend for the final rule's requirements to interfere with the 
operator's decision-making process with respect to managing its 
operation and miners.
    The Agency has weighed USW and other commenters' concerns about the 
final rule making medical examinations mandatory and determined that it 
is critical to administer medical examinations when MNM miners first 
enter the profession. Mandatory examinations provided in close 
proximity to when miners are first hired and first exposed to 
respirable coal mine dust are necessary in order to establish an 
accurate baseline of each miner's health. Miners may not recognize 
early symptoms of silica-related disease; therefore, they might not be 
likely to seek medical assistance.
    MSHA received comments requesting a longer period for initial 
medical examinations. The NSSGA, PACA, CalCIMA, and IAAP suggested that 
many miners new to the industry will not continue employment beyond an 
initial probation period due to the physical demands of the work 
(Document ID1448; 1413; 1433; 1456). During the Denver, Colorado public 
hearing, one commenter suggested making the period for medical 
examinations for new miners longer, so that mine operators would be 
providing medical examinations for those new miners who are more likely 
to remain employed (Document ID 1375). MSHA agrees with the commenter 
and has changed final paragraph (c)(1) to require an initial medical 
examination no later

[[Page 28344]]

than 60 days after beginning employment. This is a change from the 
proposed rule, which would have required mine operators to ensure 
miners had a medical examination within 30 days after beginning 
employment. This will help mine operators use their resources to 
provide medical examinations for new miners who are more likely to 
continue employment.
    The NSSGA and Vanderbilt Minerals, LLC suggested eliminating the 
mandate for a follow-up examination after an observed decrease in lung 
function, as that requirement is too broad, and the decrease could be 
due to non-occupational contaminants (Document ID 1448; 1419). In 
response to comments, the Agency has not included this change in the 
final rule. MSHA acknowledges the complex nature of lung function 
decrease; the final rule includes a medically sound approach that 
aligns examinations and subsequent actions with individual miner's 
health statuses and occupational exposure profiles. Evaluating lung 
function and changes in lung burden is a normal function of assessing 
the development of lung diseases. This provision will allow for a 
uniform approach to medical surveillance that is already implemented in 
the coal industry.
    Some mining trade associations suggested that mandatory 
examinations be triggered by a specific level of exposure, instead of 
being required for all miners new to the industry (Document ID 1408; 
1428; 1448; 1424). The final rule does not include a ``trigger 
provisions because the Agency believes it is necessary to maintain 
consistency between the final rule's requirements for MNM mines and 
existing medical surveillance standards for coal mines. In MSHA's 
experience, medical surveillance requirements benefit coal miners, and 
the Agency has implemented outreach initiatives to expand coal miners' 
participation. MSHA believes that aligning the MNM medical surveillance 
requirements with the requirements for coal mines will effectively 
protect the health and safety of MNM miners.
d. 60.15(d)--Medical Examinations Results
    Proposed paragraph (d) would have required that the results of any 
medical examination performed under this section be provided by the 
PLHCP or specialist only to the miner and, at the request of the miner, 
to the miner's designated physician. In response to comments, MSHA 
added language under paragraph (d)(1) to require the PLHCP or 
specialist to provide test results within 30 days of the medical 
examination and added a requirement that the PLHCP provide test results 
to another designee identified by the miner. Under paragraph (d)(2), 
the proposed provision was changed to require mine operators to ensure, 
within 30 days of the medical examination, that the PLHCP provide 
results of the chest x-ray classifications to NIOSH, once NIOSH 
establishes a reporting system.
    MSHA received comments regarding the sharing of the medical 
examination results. Several commenters from MNM operators and mining 
industry organizations stated the medical examination results should be 
shared with the operator (Document ID 1424; 1417; 1456; 1441; 1448). 
The NSSGA suggested medical providers be required to send a written 
medical opinion to the operator if the operator requires the miner to 
sign a medical release form stating what information can be shared with 
the operator (Document ID 1448). This commenter also stated that 
examination results need to be shared with the operator as soon as 
possible, so that the operator can take actions to protect miners' 
health (Document ID 1448). Other commenters, including BMC, AEMA, and 
NVMA, suggested that medical examination results should be shared with 
mine operators (Document ID 1417; 1424; 1441). AEMA stated that the 
failure to communicate a confirmed diagnosis to the mine operator may 
inadvertently adversely hamper the miner's ability to receive 
compensation under workers' compensation program (Document ID 1424). 
However, commenters from labor organizations and medical professional 
associations stated that the proposed standard ensures that miners' 
medical confidentiality is protected when those miners undergo medical 
surveillance (Document ID 1398; 1447; 1449; 1410; 1373).
    MSHA agrees with the commenters who expressed concerns regarding 
the confidentiality and timeliness of medical examination results. 
Under final paragraph (d)(1), MSHA modified the language of the 
proposal to clarify that the final rule requires the mine operator to 
ensure the PLHCP or specialist provide the medical examination results 
only to the miner, or to the miner's designated physician or another 
designee identified by the miner, and that this be done within 30 days 
of the examination. Paragraph (d)(1) ensures that the mine operator 
does not receive the miner's medical examination results. MSHA also 
added a provision to paragraph (d)(1) specifying that the miner can add 
a designee to receive the examination results in addition to the 
miner's physician, in case the miner needs to provide the examination 
results to other persons, such as family members or a health care 
professional who is not a physician. MSHA believes the timely receipt 
of medical examination results is important to allow the miner to make 
informed decisions regarding their health. Therefore, the Agency adds 
the requirement that the mine operator must ensure that the PLHCP or 
specialist provide the miner with their medical examination results 
within 30 days.
    Under paragraph (e), the mine operator will obtain a written 
medical opinion from the PLHCP or specialist within 30 days of the 
medical examination. The written opinion must contain only the 
following: the date of the medical examination, a statement that the 
examination has met the requirements of this section, and any 
recommended limitations on the miner's use of respirators. No other 
information from the miner's medical examination may be obtained by the 
mine operator. Based on MSHA's experience with medical surveillance for 
coal miners, the Agency believes that confidentiality regarding medical 
conditions is essential, because it encourages miners to take advantage 
of the opportunity to detect early adverse health effects caused by 
respirable crystalline silica. (79 FR 24813, 24928).
    The AIHA and the Black Lung Clinics expressed support for a 
requirement that operators submit medical surveillance plans to NIOSH 
for approval (Document ID 1351; 1410). ACOEM stated that if submitting 
for NIOSH approval creates administrative bottlenecks, employers should 
instead be allowed to contract with qualified physicians for these 
examinations, with the requirement that the supervising physician be 
board-certified in pulmonary disease or occupational medicine or 
another American Board of Medical Specialties (ABMS) (Document ID 
1405). Two commenters, the NVMA and AEMA, stated that NIOSH is not a 
regulatory agency, and thus should not oversee medical surveillance 
plans (Document ID 1441; 1424).
    The Black Lung Clinics suggested that medical examination results 
should be reported to NIOSH so that MSHA can monitor the effectiveness 
of dust controls (Document 1410). This commenter further suggested that 
MSHA create a repository for all screening results accessible to health 
care providers that can help detect early disease (Document ID 1410). 
The UMWA recommended that MSHA work with NIOSH to expand the Coal 
Workers Health Surveillance Program's mobile

[[Page 28345]]

units to screen MNM miners as well or, alternatively, create new Health 
Surveillance Program mobile units targeting MNM miners (Document ID 
1398).
    After considering the comments, MSHA agrees with commenters that 
medical examination results should be submitted to NIOSH. MSHA has 
added a new final paragraph (d)(2) that requires the mine operator to 
ensure that, within 30 days of a miner's medical examination, the PLHCP 
or specialist provides the results of chest X-ray classifications to 
NIOSH, once NIOSH establishes a reporting system. The final rule does 
not require medical surveillance plans or NIOSH approval of them. MSHA 
agrees with commenters' concerns that having MNM mine operators develop 
and submit a medical surveillance plan for approval could cause 
administrative delays and adversely affect miners' health. The new 
requirement to submit chest X-ray classifications to NIOSH for 
occupational health research will provide the public important health 
information related to respirable crystalline silica disease and MSHA 
expects this information will provide a public health benefit.
    This requirement is important because NIOSH intends to work with 
MSHA and the MNM mining community to create a reporting system to help 
mine operators ensure that PLHCPs or specialists may easily submit the 
required information. MSHA and NIOSH will inform mine operators and 
other stakeholders in a timely manner when the reporting system is 
available. When NIOSH establishes the system, NIOSH and MSHA will issue 
a joint notice to the mining community. In this notice, NIOSH and MSHA 
will include the logistics of the reporting system, information on how 
operators can ensure that the PLHCPs provide the required information 
to NIOSH, and information on how miners and medical professionals can 
effectively use the system. This information will be posted on both 
Agencies' websites. MSHA enforcement and Educational Field and Small 
Mine Services (EFSMS) staff will work with operators to facilitate 
compliance.
e. 60.15(e)--Written Medical Opinion
    As discussed above, final paragraph (e), unchanged from the 
proposed rule, requires MNM mine operators to obtain a written medical 
opinion from a PLHCP or specialist within 30 days of the medical 
examination, and requires that this opinion include only the date of a 
miner's medical examination, a statement that the examination has met 
the requirements of this section, and any recommended limitations on 
the miner's use of respirators. The purpose of the opinion is to enable 
the mine operator to verify the examination has occurred and to provide 
the operator with information on miners' ability to use respirators.
    The Agency received several comments regarding proposed paragraph 
(e). One commenter, the CalCIMA, was concerned about whether the 
medical opinion would be available in a timely manner (Document ID 
1433). MSHA understands the commenter's concern. The Agency believes 
that the 30-day requirement to provide the medical opinion regarding 
the recommended limitation on the miner's use of respirators should 
provide the mine operator sufficient notice to address any issues.
    The AOEC suggested that MSHA should follow OSHA in requiring 
clinicians to prepare a written report to the worker and provide a 
written medical opinion to the employer (Document ID 1373). That 
commenter stated that under OSHA's rule, the report remains 
confidential, the clinician discusses the examination results with the 
worker, and the worker signs a medical release form that clarifies what 
information the employer has received (Document ID 1373). MSHA notes 
that its final rule includes requirements similar to OSHA's reporting 
requirements in that the operator receives very limited information and 
will not be apprised of the results of the examination. Because the 
mine operator is receiving very limited information, MSHA determined 
that a medical release form signed by the miner is not necessary.
f. 60.15(f)--Written Medical Opinion Records
    Final paragraph (f), unchanged from the proposed rule, requires the 
mine operator to maintain a record of the written medical opinion 
obtained from the PLHCP or specialist under paragraph (e). This 
requirement provides a record to ensure compliance with the standard. 
MSHA received comments on the record retention requirements for written 
medical opinion records that are discussed further in Section 
VIII.B.9.a. Records retention periods.
g. Compliance Assistance
    The NSSGA highlighted the importance of compliance assistance for 
mines, especially small mines that do not have experience with medical 
surveillance programs (Document ID 1448). MSHA agrees with the 
commenter that compliance assistance is needed and will develop 
compliance materials to assist mine operators in implementing the final 
rule, including the medical surveillance requirements. MSHA will work 
with the mining community to ensure the final rule is implemented 
consistently and in a manner that adds to existing protections for 
miners. See the more complete discussion on MSHA's compliance 
assistance for this rulemaking under Section VIII.A. General Issues.
9. Section 60.16--Recordkeeping Requirements
    Section 60.16 identifies recordkeeping retention requirements for 
records created in part 60. The final rule requires mine operators to 
retain evaluation, sampling, and corrective actions records for at 
least 5 years. The final rule requires mine operators to retain written 
determination records and written medical opinion records for the 
duration of a miner's employment plus 6 months. It also requires mine 
operators, upon request from an authorized representative of the 
Secretary, from an authorized representative of miners, or from miners, 
to promptly provide access to any record listed in Sec.  60.16.
    In the proposal, MSHA sought comment on the utility of the 
recordkeeping requirements in this section. MSHA received several 
comments on the proposed recordkeeping requirements, including from an 
industrial hygiene professional association and mining trade 
association, supporting the Agency's proposed recordkeeping provisions 
(Document ID 1351; 1424). A MNM operator and mining trade association 
opposed the recordkeeping requirements, stating that the requirements 
were duplicative and should be more flexible (Document ID 1419; 1448). 
Below is a detailed discussion of the comments received on this 
section.
a. Records Retention Periods
    MSHA received comments from labor unions, advocacy organizations, 
one MNM operator, and a federal elected official requesting an increase 
in the retention periods for sampling records (Document ID 1398; 1416; 
1417; 1425; 1439; 1447; 1449). Records that were to be retained by the 
mine operator under this section include evaluation, sampling, and 
corrective actions records, as described in proposed paragraphs 
60.16(a)(1) to (3).
    USW and AFL-CIO stated that increased record retention is 
particularly important for MNM mines,

[[Page 28346]]

which are typically surface mines and are inspected less frequently 
than underground coal mines (Document ID 1447; 1449). The UMWA 
recommended that, for MNM miners, operators should be required to keep 
records specified under paragraphs (a)(1) to (3) for 30 years and to 
provide those records to the miner on termination of employment; 
operators be required to transfer records to a successor employer; and 
when an employer is ceasing operations and there is no successor 
employer to receive the record, the employer notify affected employees 
of their rights of access to records at least 3 months prior to the 
cessation of the employer's business (Document ID 1398). BMC stated 
that the sampling and corrective actions records proposed to be 
retained for at least 2 years should be required to be preserved 
indefinitely (Document ID 1417). Appalachian Voices recommended that 
all records regarding sampling be retained for longer than the life of 
the mine operation (Document ID 1425).
    USW and AFL-CIO expressed concern that retaining records for 2 
years would be insufficient to establish a pattern of exposure or 
provide other critical information such as the evaluation of corrective 
actions. Labor unions, advocacy organizations, a MNM operator, and an 
individual suggested that MSHA should align its recordkeeping 
requirements with the OSHA silica standard recordkeeping requirements 
(29 CFR 1910.1020) (Document ID 1398; 1412; 1416; 1417; 1425; 1447).
    In response to comments requesting an increase in the record 
retention period, the final rule increases the record retention period 
for evaluation, sampling, and corrective actions records in paragraphs 
(a)(1) to (3) to at least 5 years. Increasing to the 5-year record 
retention period for evaluation, sampling, and corrective actions 
records will help mine operators, miners, and MSHA better evaluate and 
monitor changes in exposures, understand health hazards, and ensure the 
implementation and maintenance of proper controls to protect miners 
from health hazards associated with respirable crystalline silica.
    Under final (a)(1) and (2), evaluation and sampling records confirm 
that sampling results accurately represent current exposure conditions. 
The 5-year recordkeeping requirement for evaluation and sampling 
records will provide mine operators with robust information to enable 
them to understand a history of occupational exposures at the mines and 
to take appropriate actions to protect miners, such as implementing 
engineering and administrative controls. Evaluation and sampling 
records can identify overexposures due to changes in production, 
processes, controls, or geological conditions. These records help mine 
operators develop, implement, and adjust controls and other measures 
that protect miners from overexposures. In addition, these expanded 
records will provide miners and their representatives with information 
about exposure patterns over time to understand health hazards at their 
mines and to make informed decisions about their health care. As some 
commenters noted, this information can be invaluable to miners who have 
already been diagnosed with an illness or experienced negative health 
effects and help them to make decisions about their health and future 
employment. The 5-year records of evaluation and sampling will also 
enable MSHA staff in Technical Support and Educational Field and Small 
Mine Services to provide needed compliance assistance.
    The 5-year recordkeeping requirement for corrective actions records 
in final paragraph (a)(3) will help mine operators and MSHA enforcement 
staff determine if existing controls are effective, or if maintenance 
or additional controls are needed. In MSHA's experience, the cumulative 
record provides MSHA and mine operators with information to identify 
trends in exposures and operational changes. Mine operators can use 
trend information to determine the effectiveness of controls over time 
and to take proactive measures to prevent future overexposures, while 
miners and their representatives can use the trend information to 
determine health hazards and protection needs at their mines.
    MSHA has determined that the 5-year retention period in final 
paragraphs (a)(1) to (3) balances the operator's burden to maintain 
records and the need for this information to take appropriate action to 
protect miners' health. The 5-year record retention is also consistent 
with MSHA's record retention period for operator samples collected for 
diesel particulate matter in underground metal and nonmetal mines 
(Sec.  57.5071(d)(2)) and other injury and illness reports required for 
all mines (Sec.  50.40). From MSHA's experience and observation, 
informed miners who are aware of occupational health hazards around 
them are more likely to follow safe work practices and to report these 
hazards to their operators or MSHA when necessary. When miners are 
aware of occupational health hazards and participate in the 
identification, remediation, and control of those hazards, the overall 
level of safety and health at the mine will be improved. In sum, 
informed miners are more likely and better able to play an active role 
in safety and health as the Mine Act envisions and better protect 
themselves and other miners.
    MSHA notes that minor changes have been made to final paragraphs 
(a)(1) to (3) to change the citation for the records addressed and to 
reflect changes discussed in Sec.  60.12 and 60.13. MSHA has similarly 
revised the citations in Table 1 to Paragraph (a)--Recordkeeping 
Requirements.
    Like the proposal, final paragraphs (a)(4) and (5) require that the 
written determination by a PLHCP that a miner is unable to wear a 
respirator under Sec.  60.14(b), as well as the medical surveillance 
records underSec.  60.15(f), be retained for the duration of the 
miner's employment plus 6 months. MSHA received several comments 
regarding the retention period for medical surveillance records, with 
most commenters supporting a longer retention period.
    UMWA recommended that medical surveillance records be kept for 30 
years and provided to the miner on termination of employment; that 
operators be required to transfer records to a successor employer; and 
that when an employer is ceasing operations and there is no successor 
employers to receive the record, the employer be required to notify 
affected employees of their rights of access to records at least 3 
months prior to the cessation of the employer's business Document ID 
1398). AOEC, APHA, and USW suggested that MSHA should align its 
recordkeeping requirements for medical surveillance records with the 
OSHA silica standard recordkeeping requirements (29 CFR 1910.1020) 
(Document ID 1373; 1416; 1447). These same commenters and a black lung 
clinic and an individual suggested that, given the latency periods 
associated with health effects from silica exposure, medical 
surveillance records are invaluable for miners who are diagnosed with 
silica-related health conditions (Document ID 1373; 1416; 1447; 1418; 
1412).
    In response to these comments, MSHA reiterates that mine operators 
do not have access to a miner's medical information and therefore, do 
not maintain a record of such information. Only the PLHCP's written 
determination made under paragraph 60.14(b) on whether a miner is able 
to wear a respirator must be provided to mine operators. Under the 
final rule, as in the proposal, the mine operator will retain

[[Page 28347]]

the written determination record for the duration of miner employment 
plus six months.
    Under final 60.15(d), medical examination results must be provided 
to the miner, at the request of the miner, to the miner's designated 
physician or another designee identified by the miner, and to NIOSH, 
once NIOSH establishes a reporting system. MSHA is not regulating the 
retention of medical examination results since they are not provided to 
the mine operator. The medical surveillance information (the written 
medical opinion records) that the mine operator will retain under final 
paragraph (a)(5) includes a record of the date of the medical 
examination, a statement that the examination has met the requirements 
of this section, and any recommended limitations on the miner's use of 
respirators. MSHA believes that retaining these medical surveillance 
records for the duration of the miner's employment plus 6 months is 
appropriate. The requirement to retain records for an additional 6 
months beyond the miner's employment gives a miner more time to request 
records if the miner is employed at another mine. For example, a miner 
who was determined to be medically unable to wear a respirator may need 
this record for new mine operator. The final rule does not increase the 
retention period because, as described above, the written medical 
opinion that the operator receives contains only basic information 
compared to the medical examination records that are in the miner's 
possession and control.
    NVMA asked for clarification on the medical surveillance 
recordkeeping requirements, remarking that the rule does not include 
provisions requiring tracking of miners' exposure throughout their 
careers and noting that miners often change companies over the course 
of their careers (Document ID 1441). This commenter asked whether it 
would be assumed that a miner's occupational illness stems from work 
with their current employer, even if all samples and medical 
surveillance show the miner was not exposed above the PEL during their 
current employment.
    MSHA reiterates that each miner's medical examination results are 
provided to that miner, to the miner's physician or other designee at 
the request of the miner, and to NIOSH, once NIOSH establishes a 
reporting system. NIOSH's reporting system, once established, will 
provide public health information on rates of silica-related disease, 
tenure, and prevalence in the MNM industry.
    Miners will have access to all medical examination results obtained 
under this part and will be able to track any impacts of exposure. The 
purpose of the medical surveillance examination requirements is to help 
miners seek help from medical professionals who can identify early 
symptoms of respirable crystalline silica-related diseases and inform 
them of their health status, so that they can take early and necessary 
steps to protect their health.
    Vanderbilt Minerals, LLC stated that medical records are required 
to be collected under the Health Insurance Portability and 
Accountability Act and that an additional requirement by MSHA would be 
duplicative and unnecessary (Document ID 1419). MSHA clarifies that the 
mine operator is not responsible for obtaining and preserving the 
miner's medical examination results or records. Therefore, there is no 
duplication of collecting medical records.
b. Access to Records Maintained Under 60.16
    Final paragraph 60.16(b), like the proposal, requires mine 
operators to make records in this section available promptly upon 
request to miners, authorized representatives of miners, and authorized 
representatives of the Secretary of Labor. A federal elected official 
stated that MSHA should require sampling records and any other 
information required to be posted on the mine bulletin board to be 
submitted to miner representatives (Document ID 1439). This commenter 
also urged MSHA to require operators to provide cumulative exposure 
records to the miner upon request, similar to 30 CFR 57.5040. A miner 
health advocate suggested that corrective actions records should be 
required to be submitted to MSHA and miner representatives (Document ID 
1372).
    After considering the comments, MSHA determined that no change to 
final paragraph (b) is necessary. The requirement to provide all the 
listed records promptly upon request to miners, authorized 
representatives of miners, and authorized representatives of the 
Secretary of Labor ensures that miners and MSHA will have access to 
records as needed which facilitates enforcement and transparency. 
Miners, miners' representatives, and MSHA can request the records in 
this section at any time; therefore, MSHA has determined that it is not 
necessary to require operators submit records to miners, miners' 
representatives, and MSHA without request.
c. Other Comments
    The APHA suggested that all required records should be made 
available to NIOSH (Document ID 1416). As discussed in response to 
comments under paragraph 60.15(d)(2), MSHA is requiring that the 
results of chest X-ray classifications obtained under medical 
surveillance examinations be made available to NIOSH for its research. 
MSHA has determined that it is not necessary to provide other records 
required under part 60 to NIOSH.
    The AIHA supported the proposed recordkeeping requirements and 
recommended that operators be required to develop and maintain exposure 
control plans that identify the tasks that involve miners' exposures 
above the PEL and the methods used to protect miners, including 
procedures to restrict access to work areas where high exposures may 
occur (Document ID 1351).
    After considering the comment, MSHA has concluded that an exposure 
control plan record is not necessary, because of the sampling and 
control methods required. As required under part 60, mine operators 
must use engineering and administrative controls to prevent 
overexposures to respirable crystalline silica. Under Sec.  60.12(c), 
mine operators are required to evaluate these controls at least every 6 
months or whenever there is a change in production, processes, 
installation and maintenance of engineering controls, installation and 
maintenance of equipment, administrative controls, or geological 
conditions to determine if the change is reasonably expected to result 
in new or increased respirable crystalline silica exposures. The 
operator must make a record of the evaluation, including the evaluated 
change, the impact on respirable crystalline silica exposure, and the 
date of the evaluation and post the record on the mine bulletin board 
and, if applicable, by electronic means, for the next 31 days. 
Operators are expected to conduct these evaluations to assess changing 
conditions on a regular basis to ensure miners are not exposed at 
levels above the PEL. The evaluation records provide important 
information to mine operators to enable them to implement effective 
control methods to protect miners, to identify occupations and work 
areas where there is a risk of overexposure, and to make necessary 
adjustments. MSHA has determined requiring exposure control plan 
records is not necessary.
    Under paragraph 60.12(g), when mine operators sample for respirable 
crystalline silica, operators must make a record of the sample date, 
the occupations sampled, and the concentrations of respirable 
crystalline silica and respirable dust, must obtain

[[Page 28348]]

the laboratory report, and must make the information available to the 
miners. This record will enable operators and miners to identify those 
tasks where overexposures may have occurred and individuals who may be 
overexposed, as the commenter suggested. Under Sec.  60.13(b), 
operators must make a record of any corrective actions. This record 
will provide mine operators with necessary information to determine 
which control methods should be developed, implemented, and maintained 
to prevent exposures above the PEL. Miners can use this information to 
take a proactive approach to their health.
10. Section 60.17--Severability
    The final rule includes a statement of severability that each 
section of this part, as well as sections in 30 CFR parts 56, 57, 70, 
71, 72, 75, and 90 that address respirable crystalline silica or 
respiratory protection, is separate and severable from the other 
sections and provisions.
    The severability clause under Sec.  60.17 serves two purposes. 
First, it expresses MSHA's intent that if any section or provision of 
the Lowering Miners' Exposure to Respirable Crystalline Silica and 
Improving Respiratory Protection rule--including its conforming 
amendments in sections of 30 CFR parts 56, 57, 70, 71, 72, 75, and 90 
that address respirable crystalline silica or respiratory protection--
is held invalid or unenforceable or is stayed or enjoined by any court 
of competent jurisdiction, the remaining sections or provisions should 
remain effective and operative. Second, the severability clause 
expresses MSHA's judgment, based on its technical and scientific 
expertise, that each individual section and provision of the rule can 
remain effective and operative if some sections or provisions are 
invalidated, stayed, or enjoined. Accordingly, MSHA's inclusion of this 
severability clause addresses the twin concerns of Federal courts when 
determining the propriety of severability: identifying agency intent 
and clarifying that any severance will not undercut the structure or 
function of the rule more broadly. Am. Fuel & Petrochem. Mfrs. v. Env't 
Prot. Agency, 3 F.4th 373, 384 (D.C. Cir. 2021) (``Severability 
`depends on the issuing agency's intent,' and severance `is improper if 
there is substantial doubt that the agency would have adopted the 
severed portion on its own''') (quoting North Carolina v. FERC, 730 
F.2d 790, 796 (D.C. Cir. 1984) and New Jersey v. Env't Prot. Agency, 
517 F.3d 574, 584 (D.C. Cir. 2008)).
    Under the principle of severability, a reviewing court will 
generally presume that an offending provision of a regulation is 
severable from the remainder of the regulation, so long as that outcome 
appears consistent with the issuing agency's intent, and the remainder 
of the regulation can function independently without the offending 
provision. See K Mart Corp. v. Cartier, Inc., 486 U.S. 281, 294 (1988) 
(invalidating and severing subsection of a regulation where it would 
not impair the function of the statute as a whole and there was no 
indication the regulation would not have been passed but for inclusion 
of the invalidated subsection). Consequently, in the event that a court 
of competent jurisdiction stays, enjoins, or invalidates any provision, 
section, or application of this rule, the remainder of the rule should 
be allowed to take effect.
    MSHA did not receive any comments on this section. Final Sec.  
60.17 is the same as proposed.

C. Conforming Amendments

    The final rule makes conforming amendments in 30 CFR parts 56, 57, 
70, 71, 72, 75, and 90 based on the new part 60. The compliance dates 
for the conforming amendments align with the compliance dates for part 
60. Compliance with the conforming amendments to parts 56 and 57 is 
required by 24 months after publication, for MNM operators; and 
compliance with the conforming amendments to parts 70, 71, 72, 75, and 
90 is required by 12 months after publication, for coal mine operators. 
The compliance dates for the conforming amendments assure that miners 
are protected under the existing standards until mine operators are 
required to comply with part 60.
    In other words, existing sections in parts 56 and 57 will remain in 
place for 24 months following publication. For MNM operators, 
compliance with the conforming amendments in parts 56 and 57 is not 
required until 24 months after publication. Existing sections in parts 
70,71, 72, 75, and 90 will remain in place for 12 months following 
publication. For coal operators, compliance with the conforming 
amendments in these parts is not required until 12 months after 
publication.
    For the conforming amendments, a set of instructions involving the 
establishment of temporary sections and redesignation of those sections 
are required for the Federal Register to maintain existing standards 
for parts 56, 57, 70, 71, 72, 75, and 90 until their respective 
compliance dates. On the effective date of the final rule (60 days 
after publication), the conforming amendments will be published to 
temporary sections, designated by the suffix ``T'' at the end of the 
section number (e.g., Sec.  56.5001T). These temporary sections 
indicate how the paragraphs will read on the compliance dates. On the 
compliance dates, the existing sections associated with conforming 
amendments will be removed and the temporary sections will be 
redesignated without the ``T'' to replace the removed section (e.g. 
Sec.  56.5001T will be redesignated Sec.  56.5001). With the 
redesignation, compliance with the conforming amendments will be 
required.
    The conforming amendment changes to respiratory protection 
standards are discussed in Section VIII.D Updating MSHA Respiratory 
Protection Standards: Incorporation of ASTM F3387-19 by Reference.
1. Part 56--Safety and Health Standards--Surface Metal and Nonmetal 
Mines
a. Section 56.5001--Exposure Limits For Airborne Contaminants
    The final rule, like the proposal, amends Sec.  56.5001(a) to add 
respirable crystalline silica as an exception. Amended paragraph (a) 
governs exposure limits for airborne contaminants other than respirable 
crystalline silica and asbestos for surface MNM mines. MSHA did not 
receive any comments on the proposed change.
    In a change from the proposal, MSHA makes a non-substantive change 
to paragraph (a) to update the terminology for the name of the MSHA 
District Office to the Mine Safety and Health Enforcement District 
Office. The Mine Safety and Health Enforcement District Office covers 
both MNM mines and coal mines since the Agency no longer maintains 
separate offices for both types of mines. The Agency no longer 
differentiates between MNM District Offices and Coal District Offices. 
This change was not discussed in the proposal.
b. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for the 
conforming amendments in part 56. Then, 720 days after publication of 
the final rule, the existing section for the conforming amendments in 
part 56 will be removed and the temporary section will be redesignated 
without the ``T'' to replace the removed section. The result of these

[[Page 28349]]

technical changes is that mine operators must comply with the existing 
standards until the compliance dates in part 60.
2. Part 57--Safety and Health Standards--Underground Metal and Nonmetal 
Mines
a. Section 57.5001--Exposure Limits For Airborne Contaminants
    The final rule, like the proposal, amends Sec.  57.5001(a) to add 
respirable crystalline silica as an exception. Amended paragraph (a) 
governs exposure limits for airborne contaminants other than respirable 
crystalline silica and asbestos for underground MNM mines. MSHA did not 
receive any comments on the proposed change.
    In a change from the proposal, MSHA makes a non-substantive change 
to paragraph (a) to update the terminology for the name of the MSHA 
district office to the Mine Safety and Health Enforcement District 
Office. The Mine Safety and Health Enforcement District Office covers 
both MNM mines and coal mines since the Agency no longer differentiates 
between MNM District Offices and Coal District Offices. This change was 
not discussed in the proposal.
b. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for the 
conforming amendments in part 57. Then, 720 days after publication of 
the final rule, the existing section for the conforming amendments in 
part 57 will be removed and the temporary section will be redesignated 
without the ``T'' to replace the removed section. The result of these 
technical changes is that mine operators must comply with the existing 
standards until the compliance dates in part 60.
3. Part 70--Mandatory Health Standards--Underground Coal Mines
a. Section 70.2--Definitions
    The final rule, like the proposal, removes the quartz definition in 
Sec.  70.2 since the Agency is adopting an independent respirable 
crystalline silica standard in part 60. Therefore, the term quartz no 
longer appears in part 70. MSHA did not receive any comments on the 
proposed change.
b. Section 70.101--Respirable Dust Standard When Quartz Is Present
    The final rule, like the proposal, removes Sec.  70.101 in its 
entirety and reserves the section number. Section 70.101, Respirable 
dust standard when quartz is present, is no longer needed because MSHA 
is adopting an independent respirable crystalline silica standard in 
part 60.
    As discussed in greater detail in Section VIII.B.3.b PEL in coal 
mines, of this preamble, MSHA solicited comments on whether to 
eliminate the reduced standard for total respirable dust when quartz is 
present at coal mines and received feedback from stakeholders generally 
agreeing with the Agency's proposal to establish a standard for 
respirable crystalline silica that is independent from the respirable 
coal mine dust standard. For example, the NMA, the MCPA and the 
Pennsylvania Coal Alliance supported the removal of the respirable dust 
standards when quartz is present (i.e., Sec. Sec.  70.101 and 71.101, 
and 90.101), reasoning that they are no longer needed since the rule 
proposes a standalone standard for respirable crystalline silica 
(Document ID 1428; 1406; 1378).
    In response to commenters, MSHA has concluded that establishing an 
independent and lower PEL for respirable crystalline silica for coal 
mines allows more effective control of respirable crystalline silica 
than the existing reduced standards, because the separate standard is 
more transparent and protective. MSHA clarifies that the respirable 
coal mine dust standard is not eliminated, only the sampling 
requirements for when silica is present under Sec.  70.101. MSHA agrees 
with the commenters supporting the removal of Sec.  70.101.
c. Section 70.205--Approved Sampling Devices; Operation; Air Flowrate
    The final rule, like the proposal, amends paragraph 70.205(c) to 
remove the reference to the reduced RCMD standard. References to the 
RCMD exposure limit specified in Sec.  70.100 replace references to the 
applicable standard. The rest of the section remains unchanged.
d. Section 70.206--Bimonthly Sampling; Mechanized Mining Units
    The final rule, like the proposal, removes Sec.  70.206 and 
reserves the section number. Section 70.206 included requirements for 
bimonthly sampling of mechanized mining units which were in effect 
until January 31, 2016, and are no longer applicable.
e. Section 70.207--Bimonthly Sampling; Designated Areas
    The final rule, like the proposal, removes Sec.  70.207 and 
reserves the section number. Section 70.207 included requirements for 
bimonthly sampling of designated areas that were in effect until 
January 31, 2016, and are no longer applicable.
f. Section 70.208--Quarterly Sampling; Mechanized Mining Units
    The final rule, like the proposal, amends Sec.  70.208 to remove 
references to a reduced RCMD standard. Paragraph (c) in Sec.  70.208 is 
removed and the paragraph designation reserved. References to the 
respirable dust standard specified in Sec.  70.100 replace references 
to the applicable standard throughout the section.
    A new table 1 is added to Sec.  70.208. The new table contains the 
Excessive Concentration Values (ECV) for the section based on a single 
sample, 3 samples, or the average of 5 or 15 full-shift coal mine dust 
personal sampler unit (CMDPSU) or continuous personal dust monitor 
(CPDM) concentration measurements. The new table contains the remaining 
ECV after the removal of the reduced standard in Sec.  70.101 and was 
generated from data previously contained in Tables 70-1 and 70-2 in 
Subpart C of part 70. Conforming changes are made to paragraphs (e) and 
(f)(1) and (2) to update the name of the table to table 1. MSHA did not 
receive any comments on the proposed changes.
g. Section 70.209--Quarterly Sampling; Designated Areas
    The final rule, like the proposal, amends Sec.  70.209 to remove 
references to a reduced RCMD standard. Paragraph (b) in Sec.  70.209 is 
removed and the paragraph designation reserved. References to the RCMD 
exposure limit specified in Sec.  70.100 replace references to the 
applicable standard.
    A new table 1 is added to Sec.  70.209. The new table contains the 
ECVs for the section based on a single sample, 2 or more samples, or 
the average of 5 or 15 full-shift CMDPSU/CPDM concentration 
measurements. This table contains the remaining ECV after the removal 
of the reduced RCMD standard in Sec.  70.101 and was generated from 
data previously contained in Tables 70-1 and 70-2 in Subpart C of part 
70. Conforming changes are made to paragraphs (c) and (d)(1) and (2) to 
update the name of the table to table 1. MSHA did not receive any 
comments on the proposed changes.
h. Subpart C--Table 70-1 and Table 70-2
    The final rule, like the proposal, removes Table 70-1 to Subpart C 
of Part 70, Excessive Concentration Values (ECV) Based on Single, Full-
Shift CMDPSU/CPDM Concentration Measurements and Table 70-2 to

[[Page 28350]]

Subpart C of Part 70, Excessive Concentration Values (ECV) Based on the 
Average of 5 or 15 Full-Shift CMDPSU/CPDM Concentration Measurements 
because Sec.  70.101 is removed. These tables are replaced with new 
tables in Sec. Sec.  70.208 and 70.209. MSHA did not receive any 
comments on the proposed change.
i. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for most of 
the conforming amendments in part 70. Then, 360 days after publication 
of the final rule, the existing section for these conforming amendments 
in part 70 will be removed and the temporary section will be 
redesignated without the ``T'' to replace the removed section. The 
result of these technical changes is that mine operators must comply 
with the existing standards until the compliance dates in part 60.
4. Part 71--Mandatory Health Standards--Surface Coal Mines and Surface 
Work Areas of Underground Coal Mines.
a. Section 71.2--Definitions
    The final rule, like the proposal, removes the Quartz definition in 
Sec.  71.2 because the Agency is removing the respirable dust standard 
when quartz is present in Sec.  71.101. The term quartz no longer 
appears in part 71. MSHA did not receive any comments on the proposed 
change.
b. Section 71.101--Respirable Dust Standard When Quartz Is Present
    MSHA is removing Sec.  71.101 in its entirety and reserving the 
section number. The respirable coal mine dust standard when quartz is 
present in Sec.  71.101 is no longer needed because MSHA is adopting an 
independent respirable crystalline silica standard in part 60.
    As discussed in greater detail in Section VIII.B.3.b. PEL in coal 
mines, of this preamble, MSHA solicited comments on whether to 
eliminate the reduced standard for total respirable dust when quartz is 
present at coal mines and received feedback from stakeholders generally 
agreeing with the Agency's proposal to establish a standard for 
respirable crystalline silica that is independent from the respirable 
coal mine dust standard. For example, the NMA, the MCPA and the 
Pennsylvania Coal Alliance supported the removal of the respirable dust 
standards when quartz is present (i.e., Sec. Sec.  70.101 and 71.101, 
and 90.101), reasoning that they are no longer needed since the rule 
proposes a standalone standard for respirable crystalline silica 
(Document ID 1428; 1406; 1378).
    In response to commenters, MSHA has concluded that establishing an 
independent and lower PEL for respirable crystalline silica for coal 
mines allows more effective control of respirable crystalline silica 
than the existing reduced standards, because the separate standard is 
more transparent and protective. MSHA clarifies that the respirable 
coal mine dust standard is not eliminated, only the sampling 
requirements for when silica is present under Sec.  71.101. MSHA agrees 
with the commenters supporting the removal of Sec. Sec.  71.101.
c. Section 71.205--Approved Sampling Devices; Operation; Air Flowrate
    The final rule, like the proposal, amends paragraph (c) to remove 
the reference to the reduced RCMD standard. References to the 
respirable dust standard specified in Sec.  71.100 replace the 
reference to the applicable standard.
d. Section 71.206--Quarterly Sampling; Designated Work Positions
    The final rule, like the proposal, amends Sec.  71.206 to remove 
references to the reduced RCMD standard. Paragraph (b) in Sec.  71.206 
is removed and the paragraph designation reserved. Other conforming 
changes for Sec.  71.206 remove references to the applicable standard 
and replace them, where needed, with references to the respirable dust 
standard specified in Sec.  71.100.
    MSHA is also amending paragraph (l) by removing Table 71-1 
Excessive Concentration Values (ECV) Based on Single, Full-Shift 
CMDPSU/CPDM Concentration Measurements and Table 71-2 Excessive 
Concentration Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/
CPDM Concentration Measurements since reference to a reduced RCMD 
standard in Sec.  71.101 is removed. A new table has been added to 
Sec.  71.206.
    Final paragraph (m), like the proposal, removes the language, ``in 
effect at the time the sample is taken, or a concentration of 
respirable dust exceeding 50 percent of the standard established in 
accordance with Sec.  71.101,'' because the reduced standard in Sec.  
71.101 is removed.
    A new table 1 is added to Sec.  71.206. This table contains the ECV 
for the section based on a single sample, two or more samples, or the 
average of five full-shift CMDPSU/CPDM concentration measurements. This 
table contains the remaining ECV after the removal of the reduced 
standard in Sec.  71.101. It was generated from data contained in 
existing Tables 71-1 and 71-2 to Subpart C of part 71. Conforming 
changes are made to paragraphs (h) and (i)(1) and (2) to update the 
name of the table to table 1. MSHA did not receive any comments on the 
proposed changes.
e. Section 71.300--Respirable Dust Control Plan; Filing Requirements
    Final Sec.  71.300, like the proposal, removes references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
71.100 replaces references to the applicable standard. MSHA did not 
receive any comments on the proposed change.
f. Section 71.301--Respirable Dust Control Plan; Approval by District 
Manager and Posting
    Final Sec.  71.301, like the proposal, removes references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
71.100 replaces references to the applicable standard. MSHA did not 
receive any comments on the proposed change.
g. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for most of 
the conforming amendments in part 71. Then, 360 days after publication 
of the final rule, the existing section for these conforming amendments 
in part 71 will be removed and the temporary section will be 
redesignated without the ``T'' to replace the removed section. The 
result of these technical changes is that mine operators must comply 
with the existing standards until the compliance dates in part 60.
5. Part 72--Health Standards for Coal Mines
a. Section 72.800--Single, Full-Shift Measurement of Respirable Coal 
Mine Dust
    Final Sec.  72.800, like the proposal, removes references to the 
reduced RCMD standard. The section also replaces references to Tables 
70-1, 71-1, and 90-1 with references to the new tables in Sec. Sec.  
70.208, 70.209, 71.206, and 90.207. MSHA did not receive any comments 
on the proposed changes.
b. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for the 
conforming amendments in part 72. Then, 360 days

[[Page 28351]]

after publication of the final rule, the existing section for the 
conforming amendments in part 72 will be removed and the temporary 
section will be redesignated without the ``T'' to replace the removed 
section. The result of these technical changes is that mine operators 
must comply with the existing standards until the compliance dates in 
part 60.
6. Part 75--Mandatory Safety Standards--Underground Coal Mines
a. Section 75.350(b)(3)(i) and (ii)--Belt Air Course Ventilation
    The final rule, like the proposal, updates Sec.  75.350 by revising 
paragraph (b)(3)(i) and removing paragraphs (b)(3)(i)(A) and (B) and 
(b)(3)(ii). Paragraph (b)(3)(i) is revised to ``[T]he average 
concentration of respirable dust in the belt air course, when used as a 
section intake air course, shall be maintained at or below 0.5 mg/
m\3\.'' Paragraph (b)(3)(i)(A) is removed because its provision has not 
been in effect since August 1, 2016. Paragraph (b)(3)(i)(B) is removed 
because the language has been incorporated in revised paragraph 
(b)(3)(i), making (b)(3)(i)(B) redundant. Existing paragraph (b)(3)(ii) 
is removed since it refers to a reduced RCMD standard under Sec.  
70.101 that is also removed. Existing paragraph (b)(3)(iii) is 
redesignated to (b)(3)(ii). MSHA did not receive any comments on the 
proposed changes.
b. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for the 
conforming amendments in part 75. Then, 360 days after publication of 
the final rule, the existing section for the conforming amendments in 
part 75 will be removed and the temporary section will be redesignated 
without the ``T'' to replace the removed section. The result of these 
technical changes is that mine operators must comply with the existing 
standards until the compliance dates in part 60.
7. Part 90--Mandatory Health Standards--Coal Miners Who Have Evidence 
of the Development of Pneumoconiosis.
a. Section 90.2--Definitions
    The final rule, like the proposal, removes the Quartz definition in 
Sec.  90.2 because the Agency is removing the respirable dust standard 
when quartz is present in Sec.  90.101. The term quartz no longer 
appears in part 90.
    In addition, MSHA is revising the definition of Part 90 miner to 
remove ``the applicable standard'' (which referred to the reduced RCMD 
standard). The revised definition just includes ``the standard'' (which 
refers to the respirable dust standard specified in Sec.  90.100). MSHA 
did not receive any comments on the proposed change.
b. Section 90.3--Part 90 Option; Notice of Eligibility; Exercise of 
Option
    The final rule, like the proposal, revises paragraph (a) in Sec.  
90.3 to remove ``the applicable standard'' (which referred to the 
reduced RCMD standard) and just include ``the standard'' (which refers 
to the respirable dust standard specified in Sec.  90.100). MSHA did 
not receive any comments on the proposed change.
c. Section 90.100--Respirable Dust Standard
    In a change from the proposal, MSHA updates Sec.  90.100 by 
removing paragraphs (a) and (b) and revising the section to, ``After 
the 20th calendar day following receipt of notification from MSHA that 
a part 90 miner is employed at the mine, the operator shall 
continuously maintain the average concentration of respirable dust in 
the mine atmosphere during each shift to which the part 90 miner in the 
active workings of the mine is exposed, as measured with an approved 
sampling device and expressed in terms of an equivalent concentration, 
at or below 0.5 mg/m\3\.'' Paragraph (a) is removed because its 
provision has not been in effect since August 1, 2016. Paragraph (b) is 
removed because the language has been incorporated in the revised 
language above, making it redundant. MSHA makes this change in the 
final rule to match the change made in Sec.  75.350(b)(3)(i).
d. Section 90.101--Respirable Dust Standard When Quartz Is Present
    The final rule, like the proposal, removes Sec.  90.101 in its 
entirety and reserves the section number. The respirable coal mine dust 
standard when quartz is present in Sec.  90.101 is no longer needed 
because MSHA is adopting an independent respirable crystalline silica 
standard in part 60.
    As discussed in greater detail in Section VIII.B.3.b PEL in coal 
mines, of this preamble, MSHA solicited comments on whether to 
eliminate the reduced standard for total respirable dust when quartz is 
present at coal mines and received feedback from stakeholders generally 
agreeing with the Agency's proposal to establish a standard for 
respirable crystalline silica that is independent from the respirable 
coal mine dust standard. For example, the NMA, the Metallurgical Coal 
Producers Association (MCPA) and the Pennsylvania Coal Alliance 
supported the removal of the respirable dust standards when quartz is 
present (i.e., Sec. Sec.  70.101 and 71.101, and 90.101), reasoning 
that they are no longer needed since the rule proposes a standalone 
standard for respirable crystalline silica (Document ID 1428; 1406; 
1378).
    In response to commenters, MSHA has concluded that establishing an 
independent PEL of 50 [micro]g/m\3\ for a full-shift exposure, 
calculated as an 8-hour TWA for respirable crystalline silica allows 
more effective control of respirable crystalline silica than the 
existing reduced standards, because the separate standard is more 
transparent and protective. MSHA clarifies that the respirable coal 
mine dust standard is not eliminated, only the sampling requirements 
for when silica is present under Sec. Sec.  90.101. MSHA agrees with 
the commenters supporting the removal of Sec. Sec.  90.101.
e. Section 90.102--Transfer; Notice
    The final rule, like the proposal, amends Sec.  90.102 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100). MSHA did not 
receive any comments on the proposed change.
f. Section 90.104--Waiver of Rights; Re-Exercise of Option
    The final rule, like the proposal, amends Sec.  90.104 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100). MSHA did not 
receive any comments on the proposed change.
g. Section 90.205--Approved Sampling Devices; Operation; Air Flowrate
    The final rule, like the proposal, amends Sec.  90.205 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100). MSHA did not 
receive any comments on the proposed change.
h. Section 90.206--Exercise of Option or Transfer Sampling
    The final rule, like the proposal, amends Sec.  90.206 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in

[[Page 28352]]

Sec.  90.100). MSHA did not receive any comments on the proposed 
change.
i. Section 90.207--Quarterly Sampling
    The final rule, like the proposal, amends Sec.  90.207 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100).
    Paragraph (b) in Sec.  90.207 is removed and the paragraph 
designation reserved. Conforming changes are made to paragraphs (c) and 
(d)(1) and (2) to update the name of the table to table 1.
    MSHA is amending paragraph (g) by removing Table 90-1 Excessive 
Concentration Values (ECV) Based on Single, Full-Shift CMDPSU/CPDM 
Concentration Measurements and Table 90-2 Excessive Concentration 
Values (ECV) Based on the Average of 5 Full-Shift CMDPSU/CPDM 
Concentration Measurements because Sec.  90.101 is removed. A new table 
1 is added to paragraph (g) to replace the tables removed. The new 
table contains the ECV for the section based on a single sample, two or 
more samples, or the average of 5 full-shift CMDPSU/CPDM concentration 
measurements. This table contains the remaining ECV after the removal 
of the reduced standard in Sec.  90.101 and was generated from data 
contained in Tables 90-1 and 90-2. MSHA did not receive any comments on 
the proposed changes.
j. Section 90.300--Respirable Dust Control Plan; Filing Requirements
    The final rule, like the proposal, amends Sec.  90.300 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100). MSHA did not 
receive any comments on the proposed change.
k. Section 90.301--Respirable Dust Control Plan; Approval by District 
Manager; Copy to Part 90 Miner
    The final rule, like the proposal, amends Sec.  90.301 to remove 
``the applicable standard'' (which referred to the reduced RCMD 
standard) and just include ``the standard'' (which refers to the 
respirable dust standard specified in Sec.  90.100). MSHA did not 
receive any comments on the proposed change.
l. Temporary Section Until Compliance Date
    As described above, 60 days after publication of the final rule, a 
new temporary section with the suffix ``T'' will be added for the 
conforming amendments in part 90. Then, 360 days after publication of 
the final rule, the existing section for the conforming amendments in 
part 90 will be removed and the temporary section will be redesignated 
without the ``T'' to replace the removed section. The result of these 
technical changes is that mine operators must comply with the existing 
standards until the compliance dates in part 60.

D. Updating MSHA Respiratory Protection Standards: Incorporation of 
ASTM F3387-19 by Reference

    MSHA is updating the Agency's existing respiratory protection 
standard to help safeguard the life and health of all miners exposed to 
respirable airborne contaminants at MNM and coal mines. The final rule 
amends the Agency's existing respiratory protection standards to 
incorporate by reference ASTM F3387-19, ``Standard Practice for 
Respiratory Protection'', in Sec. Sec.  56.5005T and 57.5005T for MNM 
mines and Sec.  72.710T for coal mines (which will become permanent 
Sec. Sec.  56.5005 and 57.5005 720 days after publication and permanent 
Sec.  72.710 360 days after publication). This change is consistent 
with the incorporation by reference of ASTM F3387-19 in final Sec.  
60.14(c)(2) making the standard's requirements applicable to respirable 
crystalline silica, and other airborne hazards encountered by miners. 
The ASTM F3387-19 standard includes provisions for selection, fitting, 
use, and care of respirators used to remove airborne contaminants from 
the air using filters, cartridges, or canisters, as well as respirators 
that protect in oxygen-deficient or immediately dangerous to life or 
health (IDLH) atmospheres. ASTM F3387-19 is the most recent consensus 
standard developed by experts in government and professional 
associations on the selection, use, and maintenance for respiratory 
equipment. The ASTM Standard replaces American National Standards 
Institute's ANSI Z88.2-1969, ``Practices for Respiratory Protection'' 
(ANSI Z88.2-1969), which was incorporated in the existing standards.
    Incorporating this voluntary consensus standard complies with the 
Federal mandate--as set forth in the National Technology Transfer and 
Advancement Act of 1995 and OMB Circular A-119--that agencies use 
voluntary consensus standards in their regulatory activities unless 
doing so would be legally impermissible or impractical. This standard 
also improves clarity because it is a consensus standard developed by 
stakeholders.
    Under existing standards, whenever respiratory protective equipment 
is used, mine operators are required to have a respiratory protection 
program that is consistent with the provisions of ANSI Z88.2-1969. At 
the time of its publication, ANSI Z88.2-1969 reflected a consensus of 
accepted practices for respiratory protection.
    Respirator technology and knowledge on respiratory protection have 
since advanced, and as a result, changes in respiratory protection 
standards have occurred. For example, in 2006, OSHA revised its 
respiratory protection standard to add definitions and requirements for 
Assigned Protection Factors (APF) and Maximum Use Concentrations (MUCs) 
(71 FR 50122, 50123). In addition to this rulemaking, OSHA updated 
Appendix A to Sec.  1910.134: Fit Testing Procedures (69 FR 46986, 
46993, Aug. 4, 2004).
    After withdrawing the 1992 version of Z-88.2 in 2002, ANSI 
published the American National Standard, ANSI/AIHA Z88.10-2010, 
``Respirator Fit Testing Methods,'' approved in 2010. These rules and 
standards addressed the topics of APFs and fit testing. APFs provide 
employers with critical information to use when selecting respirators 
for employees exposed to atmospheric contaminants found in industry. 
Finally, in 2015, ANSI published ANSI/ASSE Z88.2-2015, ``Practices for 
Respiratory Protection,'' which referenced OSHA regulations. These 
updates included requirements for classification of considerations for 
selection and use of respirators, establishment of cartridge/canister 
change schedules, use of fit factor value for respirator fit testing, 
calculation of effective protection factors, and compliance with 
compressed air dew requirements, compressed breathing air equipment, 
and systems and designation of positive pressure respirators. In July 
2017, ANSI/ASSE transferred the responsibilities for developing 
respiratory consensus standards to ASTM International.
    The ASTM standard contains detailed guidance and provisions on 
respirator selection that are based on NIOSH's extensive experience 
with testing and approving respirators for occupational use and OSHA's 
research and rulemaking on respiratory protection. ASTM F3387-19 also 
addresses all aspects of establishing, implementing, and evaluating 
respiratory protection programs and establishes minimum acceptable 
respiratory protection program requirements in the areas of program 
administration, standard operating procedures, medical evaluation, 
respirator selection, training,

[[Page 28353]]

fit testing, respirator maintenance, inspection, and storage. ASTM 
F3387-19 comprehensively covers numerous aspects of respiratory 
protection and provides the most up-to-date provisions for current 
respirator technology and effective respiratory protection. Therefore, 
MSHA believes that ASTM F3387-19 will provide mine operators with 
information and guidance on the proper selection, use, and maintenance 
of respirators, which will protect the health and safety of miners.
1. Respiratory Protection Program Requirements
    Under the final rule, MSHA requires that the respiratory protection 
program be in writing and be consistent with the requirements of ASTM 
3387-19, including program administration, standard operating 
procedures, medical evaluation, respirator selection, training, fit 
testing; and maintenance, inspection, and storage. The following 
subsections discuss some of the requirements listed in ASTM F3387-19.
a. Program Administration
    ASTM F3387-19 specifies several practices related to respiratory 
protection program administration, including the qualifications and 
responsibilities of a program administrator. For example, ASTM F3387-19 
provides that responsibility and authority for the respirator program 
be assigned to a single qualified person with sufficient knowledge of 
respiratory protection. Qualifications may have been gained through 
training or experience; however, the qualifications of a program 
administrator must be commensurate with the respiratory hazards present 
at a worksite.
    This individual administering the program should have access to and 
direct communication with the site manager about matters impacting 
worker safety and health. ASTM F3387-19 notes a preference that the 
administrator be in the company's industrial hygiene, environmental, 
health physics, or safety engineering department; however, a third-
party entity meeting the provisions may also provide this service. ASTM 
F3387-19 outlines the respiratory protection program administrator's 
responsibilities, specifying that they should include: measuring, 
estimating, or reviewing information on the concentration of airborne 
contaminants; ensuring that medical evaluations, training, and fit 
testing are performed; selecting the appropriate type or class of 
respirator that will provide adequate protection for each contaminant; 
maintaining records; evaluating the respirator program's effectiveness; 
and revising the program, as necessary.
b. Standard Operating Procedures (SOP)
    Written SOPs shall be established by the employer and shall cover a 
complete respirator program for routine and emergency. ASTM F3387-19 
also states that written SOPs for respirator programs are necessary 
when respirators are used routinely or sporadically. Written SOPs 
should cover hazard assessment; respirator selection; medical 
evaluation; training; fit testing; issuance, maintenance, inspection, 
and storage of respirators; schedule of air-purifying elements; hazard 
re-evaluation; employer policies; and program evaluation and audit. 
ASTM F3387-19 also provides that wearers of respirators be provided 
with copies of the SOP and that written SOPs include special 
consideration for respirators used for emergency situations. The 
procedures are reviewed in conjunction with the annual respirator 
program audit and are revised by the program administrator, as 
necessary.
c. Medical Evaluation
    Medical evaluations determine whether an employee has any medical 
conditions that would preclude the use of respirators, limitation on 
use, or other restrictions. ASTM F3387-19 provides that a program 
administrator advise the PLHCP of the following conditions to aid in 
determining the need for a medical evaluation: type and weight of the 
respirator to be used; duration and frequency of respirator use 
(including use for rescue and escape); typical work activities; 
environmental conditions (e.g., temperature); hazards for which the 
respirator will be worn, including potential exposure to reduced-oxygen 
environments; and additional protective clothing and equipment to be 
worn. ASTM F3387-19 also incorporates ANSI Z88.6 Respiratory 
Protection--Respirator Use--Physical Qualifications for Personnel.
d. Respirator Selection
    Proper respirator selection is an important component of an 
effective respiratory protection program. ASTM F3387-19 provides that 
proper respirator selection consider the following: the nature of the 
hazard, worker activity and workplace factors, respirator use duration, 
respirator limitations, and use of approved respirators. ASTM F3387-19 
states that the respirator selection process for both routine and 
emergency use should include hazard assessment, selection of respirator 
type or class that can offer adequate protection, and maintenance of 
written records of hazard assessment and respirator selection.
    ASTM F3387-19 provides specific steps to establish the nature of 
inhalation hazards, including determining the following: the types of 
contaminants present in the workplace; the physical state and chemical 
properties of airborne contaminants; the likely airborne concentration 
of the contaminants (by measurement or by estimation); potential for an 
oxygen-deficient environment; an occupational exposure limit for each 
contaminant; existence of an IDLH atmosphere; and compliance with 
applicable health standards for the contaminants.
    ASTM F3387-19 includes other information to support the respirator 
selection process, including information on operational 
characteristics, capabilities, and performance limitations of various 
types of respirators. These limitations must be considered during the 
selection process. ASTM F3387-19 also describes types of respirators 
and considerations for their use, including service life, worker 
mobility, compatibility with other protective equipment, durability, 
comfort factors, compatibility with the environment, and compatibility 
with job and workforce performance. Finally, ASTM F3387-19 provides 
other information that is essential for respirator selection, including 
degree of oxygen deficiency, ambient noise, and need for communication.
e. Training
    Employee training is essential for correct respirator use. ASTM 
F3387-19 provides that all users be trained in their area of 
responsibility by a qualified person to ensure the proper use of 
respirators. A respirator trainer must be knowledgeable about the 
application and use of the respirators and must understand the site's 
work practices, respirator program, and applicable regulations. 
Employees who should receive training under ASTM F3387-19 include the 
workplace supervisor, the person issuing and maintaining respirators, 
respirator wearers, and emergency teams. To ensure the proper and safe 
use of a respirator, the standard also provides that the training for 
each respirator wearer should cover, at a minimum: the need for 
respiratory protection; the nature, extent, and effects of respiratory 
hazards in the workplace; reasons for particular respirator selections; 
reasons for engineering controls not being applied or reasons why they 
are not adequate; types of efforts made to reduce or eliminate the need 
for respirators; operation, capabilities, and limitations

[[Page 28354]]

of the respirators selected; instructions for inspecting, donning, and 
doffing the respirator; the importance of proper respirator fit and 
use; and maintenance and storage of respirators. The standard provides 
for each respirator wearer to receive initial and annual training. 
Workplace supervisors and persons issuing respirators are retrained as 
determined by the program administrator. Training records for each 
respirator wearer are maintained and include the date, type of training 
received, performance results (as appropriate), and instructor's name.
f. Respirator Fit Testing
    A serious hazard may occur if a respirator, even though properly 
selected, is not properly fitted. For example, if a proper face seal is 
not achieved, the respirator will provide a lower level of protection 
than it is designed to provide because the respirator could allow 
contaminants to leak into the breathing area. Proper fit testing 
verifies that the selected make, model, and size of a respirator fits 
adequately and ensures that the expected level of protection is 
provided. ASTM F3387-19 includes provisions for qualitative and 
quantitative fit testing to determine the ability of a respirator 
wearer to obtain a satisfactory fit with a tight-fitting respirator and 
incorporates ANSI/AIHA Z88.10, Respirator Fit Testing Methods, for 
guidance on how to conduct fit testing of tight-fitting respirators and 
on appropriate methods to be used. This includes information on the 
application of fit factors and assigned protection factors, and how 
these factors are used to ensure that a wearer is receiving the 
necessary protection. ASTM F3387-19 provides for each respirator wearer 
to be fit tested before being assigned a respirator; this fit testing 
should happen at least once every 12 months or when a wearer expresses 
concern about respirator fit or comfort or has a condition that may 
interfere with the face piece seal.
g. Maintenance, Inspection, and Storage
    Proper maintenance and storage of respirators are important in a 
respiratory protection program. ASTM F3387-19 includes specific 
provisions for decontaminating, cleaning, and sanitizing respirators, 
inspecting respirators, replacing, and repairing parts, and storing and 
disposing of respirators. For example, the decontamination provisions 
state that respirators must be decontaminated after each use and 
cleaned and sanitized regularly per manufacturer instructions. 
Following cleaning and disinfection, reassembled respirators are 
inspected to verify proper working condition. ASTM F3387-19 states that 
employers consult manufacturer instructions to determine component 
expiration dates or end-of-service life, inspect the rubber or other 
elastomeric components of respirators for signs of deterioration that 
would affect respirator performance, and repair or replace respirators 
failing inspection. ASTM F3387-19 also provides that respirators are 
stored according to manufacturer recommendations and in a manner that 
will protect against hazards (e.g., physical, biological, chemical, 
vibration, shock, temperature extremes, moisture). It also provides 
that respirators are stored in a way that prevents distortion of rubber 
or other parts.
2. Section-by-Section Analysis of Incorporation by Reference--ASTM 
F3387-19
a. Part 56--Safety and Health Standards--Surface Metal and Nonmetal 
Mines
Section 56.5005--Control of Exposure to Airborne Contaminants
    Final Sec.  56.5005 is changed from the proposal. The final rule 
requires a written respiratory protection program consistent with the 
requirements of ASTM F3387-19. In the NPRM, MSHA proposed to revise 
paragraph (b) to remove the incorporation by reference to ANSI Z88.2--
1969 and incorporate by reference ASTM F3387-19 to state that approved 
respirators must be selected, fitted, cleaned, used, and maintained in 
accordance with the requirements of ASTM F3387-19 ``as applicable.'' 
MSHA proposed to update the Agency's existing respiratory protection 
standard to help safeguard the life and health of all miners when 
exposed to respirable airborne contaminants at MNM mines while wearing 
respirators. The ASTM F3387-19 standard includes, for example, 
provisions for selection, fitting, use, and care of respirators used to 
remove airborne contaminants from the air using filters, cartridges, or 
canisters, as well as respirators that protect in oxygen-deficient or 
immediately dangerous to life or health (IDLH) atmospheres. MSHA 
proposed to incorporate by reference ASTM F3387-19 because it is the 
most recent consensus standard developed by experts in government and 
professional associations on the selection, use, and maintenance for 
respiratory equipment.
    AEMA stated that the final rule should clarify whether a specific 
written respiratory protection program is required and under what 
standards (Document ID 1424. MSHA's response to these comments is 
discussed in detail in Section VIII.B.7. Section 60.14--Respiratory 
protection. Also, the Agency provides a detailed description of some 
requirements for the respiratory protection program in Section 
VIII.D.1. Respiratory Protection Program Requirements.
    In response to comments, MSHA has modified the language in 
paragraph (b) in the final rule compared to the proposal. The 
modifications include: the removal of ``as applicable''; clarification 
that a respiratory protection program must be in writing, and one non-
substantive edit in the introductory clause. These changes clarify what 
the requirements are for MNM mine operators' respiratory protection 
programs.
    MNM mine operators do not have to create a separate written 
respiratory protection program under each of 30 CFR parts 56, 57, and 
60 where ASTM F3387-19 is incorporated by reference. Operators may 
create one single program that is applicable to respirable crystalline 
silica hazards (part 60) and other airborne contaminants (parts 56 and 
57). However, as required by ASTM F3387-19 and MSHA standards, the 
respiratory protection program must assess the potential respiratory 
hazard or hazards and the mine operator must then select approved 
respirators which are appropriate for the airborne hazard(s) 
encountered. MSHA believes the final rule provides MNM mine operators 
with additional time which should be sufficient to allow them to 
prepare and develop written respiratory protection programs, if 
necessary, that are based on the finalrule's requirements.
    Consistent with the proposal, MSHA is changing paragraph (c) to 
require the presence of at least one other person with backup equipment 
and rescue capability when respiratory protection is used in 
atmospheres that are IDLH. This change is needed to conform to language 
in the incorporation by reference of ASTM F3387-19, which defines IDLH 
as ``any atmosphere that poses an immediate hazard to life or immediate 
irreversible debilitating effects on health'' (ASTM International, 
2019).
    As described above in Section VIII.C. Conforming Amendments, 60 
days after publication of the final rule, a new temporary section with 
the suffix ``T'' will be added for the conforming amendments in part 
56. Then, 720 days after publication of the final rule, the existing 
section for the conforming amendments in part 56 will be removed and 
the temporary section will be

[[Page 28355]]

redesignated without the ``T'' to replace the removed section. The 
result of these technical changes is that mine operators must comply 
with the existing standards until the compliance dates in part 60.
b. Part 57--Safety and Health Standards--Underground Metal and Nonmetal 
Mines
Section 57.5005--Control of Exposure to Airborne Contaminants
    Final Sec.  57.5005 is changed from the proposal for the same 
reasons discussed in Sec.  56.5005. The final rule requires a written 
respiratory protection program consistent with the requirements of ASTM 
F3387-19. In the NPRM, MSHA proposed to revise paragraph (b) to remove 
the incorporation by reference to ANSI Z88.2--1969 and incorporate by 
reference ASTM F3387-19 to state that approved respirators must be 
selected, fitted, cleaned, used, and maintained in accordance with the 
requirements of ASTM F3387-19 ``as applicable.'' MSHA proposed to 
update the Agency's existing respiratory protection standard to help 
safeguard the life and health of all miners when exposed to respirable 
airborne contaminants at MNM mines while wearing respirators. The ASTM 
F3387-19 standard, for example, includes provisions for selection, 
fitting, use, and care of respirators used to remove airborne 
contaminants from the air using filters, cartridges, or canisters, as 
well as respirators that protect in oxygen-deficient or immediately 
dangerous to life or health (IDLH) atmospheres. MSHA proposed to 
incorporate by reference ASTM F3387-19 because it is the most recent 
consensus standard developed by experts in government and professional 
associations on the selection, use, and maintenance for respiratory 
equipment.
    AEMA stated that the final rule should clarify whether a specific 
written respiratory protection program is required and under what 
standards (Document ID 1424). MSHA's response to these comments is 
discussed in detail in Section VIII.B.7. Section 60.14--Respiratory 
protection. Also, the Agency provides a detailed description of each of 
the requirements for the respiratory protection program in Section 
VIII.D.1. Respiratory Protection Program Requirements.
    In response to comments, MSHA has modified the language in 
paragraph (b) in the final rule compared to the proposal. The 
modifications include: the removal of ``as applicable''; clarification 
that a respiratory protection program must be in writing, and one non-
substantive edit in the introductory clause. These changes clarify what 
the requirements are for MNM mine operators' respiratory protection 
programs.
    MNM mine operators do not have to create a written respiratory 
protection program under each of 30 CFR parts 56, 57, and 60 where ASTM 
F3387-19 is incorporated by reference. Operators may create one single 
program that is applicable to respirable crystalline silica hazards 
(part 60) and other airborne contaminants (parts 56 and 57). However, 
as required by ASTM F3387-19 and MSHA standards, the respiratory 
protection program must assess the potential respiratory hazard or 
hazards and the mine operator must then select approved respirators 
which are appropriate for the airborne hazard(s) encountered. The final 
rule provides MNM mine operators additional time for compliance, which 
MSHA believes should give them sufficient time to prepare and develop 
written respiratory protection programs, if necessary, that are based 
on the final rule's requirements.
    Consistent with the proposal, MSHA is changing paragraph (c) to 
require the presence of at least one other person with backup equipment 
and rescue capability when respiratory protection is used in 
atmospheres that are IDLH. This change is needed to conform to language 
in the proposed incorporation by reference of ASTM F3387-19, which 
defines the term IDLH as ``any atmosphere that poses an immediate 
hazard to life or immediate irreversible debilitating effects on 
health'' (ASTM International, 2019).
    As described above in Section VIII.C. Conforming Amendments, 60 
days after publication of the final rule, a new temporary section with 
the suffix ``T'' will be added for the conforming amendments in part 
57. Then, 720 days after publication of the final rule, the existing 
section for the conforming amendments in part 57 will be removed and 
the temporary section will be redesignated without the ``T'' to replace 
the removed section. The result of these technical changes is that mine 
operators must comply with the existing standards until the compliance 
dates in part 60.
c. Part 72--Health Standards for Coal Mines
Section 72.710--Selection, Fit, Use, and Maintenance of Approved 
Respirators
    Final Sec.  72.710 includes two changes from the proposal. The 
final rule requires that approved respirators be selected, fitted, 
used, and maintained in accordance with the provisions of a written 
respiratory protection program consistent with the requirements of ASTM 
F3387-19. In the NPRM, MSHA proposed an editorial change to the 
introductory statement to Sec.  72.710 and that approved respirators 
must be selected, fitted, used, and maintained in accordance with the 
requirements of ASTM F3387-19 ``as applicable.''
    MSHA proposed to update the Agency's existing respiratory 
protection standard to help safeguard the life and health of coal 
miners when exposed to respirable airborne contaminants such as 
respirable coal dust while wearing respirators. The ASTM F3387-19 
standard includes provisions for selection, fitting, use, and care of 
respirators used to remove airborne contaminants from the air using 
filters, cartridges, or canisters, as well as respirators that protect 
in oxygen-deficient or immediately dangerous to life or health (IDLH) 
atmospheres. MSHA proposed to incorporate by reference ASTM F3387-19 
because it is the most recent consensus standard developed by experts 
in government and professional associations on the selection, use, and 
maintenance for respiratory equipment.
    AEMA stated that the final rule should clarify whether a specific 
written respiratory protection program is required and under what 
standards (Document ID 1424).
    MSHA's response to these comments is discussed in detail in Section 
VIII.B.7. Section 60.14--Respiratory protection. Also, the Agency 
provides a detailed description of each of the requirements for the 
respiratory protection program in Section VIII.D.1. Respiratory 
Protection Program Requirements.
    In response to comments, MSHA has modified the language to remove 
as ``as applicable'' and to clarify that the respiratory protection 
program must be in writing and must be consistent with ASTM F3387-19. 
This change clarifies what the requirements are for coal mine 
operators' respiratory protection programs.
    Coal mine operators do not have to create a separate written 
respiratory protection program under 30 CFR parts 60 and 72 part where 
ASTM F3387-19 is incorporated by reference. Operators may create a 
single program that is applicable to respirable crystalline silica 
hazards (part 60) and other airborne contaminants (part 72). However, 
as required by ASTM F3387-19 and MSHA standards, the respiratory 
protection program must assess the potential respiratory hazard or 
hazards and the mine operator must select approved respirators which 
are

[[Page 28356]]

appropriate for the airborne hazard(s) encountered. MSHA believes the 
final rule provides coal mine operators with sufficient time to prepare 
and develop written respiratory protection programs that are based on 
the rule's requirements.
    As described above in Section VIII.C. Conforming Amendments, 60 
days after publication of the final rule, a new temporary section with 
the suffix ``T'' will be added for the conforming amendments in part 
72. Then, 360 days after publication of the final rule, the existing 
section for the conforming amendments in part 72 will be removed and 
the temporary section will be redesignated without the ``T'' to replace 
the removed section. The result of these technical changes is that mine 
operators must comply with the existing standards until the compliance 
dates in part 60.

IX. Summary of Final Regulatory Impact Analysis and Regulatory 
Alternatives

A. Introduction

    Executive Order (E.O.) 12866, as amended by E.O. 14094, and E.O. 
13563 direct agencies to assess all costs and benefits of available 
regulatory alternatives and, if regulation is necessary, to select 
regulatory approaches that maximize net benefits (including potential 
economic, environmental, public health and safety effects, distributive 
impacts, and equity).\77\ E.O. 13563 emphasizes the importance of 
quantifying both costs and benefits, of reducing costs, of harmonizing 
rules, and of promoting flexibility. E.O.s 12866 and 13563 require that 
regulatory agencies assess both the costs and benefits of regulations.
---------------------------------------------------------------------------

    \77\ Executive Order 12866 of September 30, 1993: Regulatory 
Planning and Review. 58 FR 51735. October 4, 1993. https://www.archives.gov/files/federal-register/executive-orders/pdf/12866.pdf (last accessed Jan. 10, 2024).
    Executive Order 14094 of April 6, 2023: Modernizing Regulatory 
Review. 88 FR 21879. April 11, 2023. https://www.federalregister.gov/documents/2023/04/11/2023-07760/modernizing-regulatory-review (last accessed Jan. 10, 2024).
    Executive Order 13563 of January 18, 2011: Improving Regulation 
and Regulatory Review. January 18, 2011. https://www.regulations.gov/document/EPA-HQ-OA-2018-0259-0005 (last accessed 
Jan. 10, 2024).
---------------------------------------------------------------------------

    Under E.O. 12866 (as amended by E.O. 14094), the Office of 
Management and Budget (OMB)'s Office of Information and Regulatory 
Affairs (OIRA) determines whether a regulatory action is significant 
and, therefore, subject to the requirements of the E.O. and review by 
OMB. 58 FR 51735, 51741 (1993). As amended by E.O. 14094, section 3(f) 
of E.O. 12866 defines a ``significant regulatory action'' as a 
regulatory action that is likely to result in a rule that may: (1) have 
an annual effect on the economy of $200 million or more; or adversely 
affect in a material way the economy, a sector of the economy, 
productivity, competition, jobs, the environment, public health or 
safety, or state, local, territorial, or tribal governments or 
communities; (2) create a serious inconsistency or otherwise interfere 
with an action taken or planned by another agency; (3) materially alter 
the budgetary impact of entitlements, grants, user fees or loan 
programs or the rights and obligations of recipients thereof; or (4) 
raise legal or policy issues for which centralized review would 
meaningfully further the President's priorities or the principles set 
forth in the E.O. OIRA has determined that this final rule is a 
significant regulatory action under section 3(f)(1) of E.O. 12866, and 
accordingly it has been reviewed by OMB. Pursuant to Subtitle E of the 
Small Business Regulatory Enforcement Fairness Act of 1996, also known 
as the Congressional Review Act (5 U.S.C. 801 et seq.), OIRA has 
determined that this rule meets the criteria set forth in 5 U.S.C. 
804(2).
    E.O. 13563 directs agencies to propose or adopt a regulation only 
upon a reasoned determination that its benefits justify its costs; the 
regulation is tailored to impose the least burden on society, 
consistent with achieving the regulatory objectives; and in choosing 
among alternative regulatory approaches, the agency has selected those 
approaches that maximize net benefits. E.O. 13563 recognizes that some 
benefits are difficult to quantify and provides that, where appropriate 
and permitted by law, agencies may consider and discuss qualitative 
values that are difficult or impossible to quantify, including equity, 
human dignity, fairness, and distributive impacts.
    To comply with E.O.s 12866 and 13563, MSHA has prepared a final 
regulatory impact analysis (FRIA) for the final rule. The purpose of 
the FRIA is to:
     Profile the mining industry impacted by the final rule;
     Estimate the monetized societal benefits attributable to 
the new PEL resulting from reductions in fatal cases of lung cancer, 
non-malignant respiratory disease, end-stage renal disease, and both 
fatal and non-fatal cases of silicosis;
     Identify additional non-quantified benefits expected from 
the final rule;
     Estimate the costs that the mining industry will incur to 
achieve compliance with the final rule;
     Assess the economic feasibility of the final rule for the 
mining industry; and
     Evaluate the principal regulatory alternatives to the 
final rule that MSHA has considered.
    MSHA estimates the final rule will have an annualized cost of $90.3 
million in 2022 dollars at a discount rate of 3 percent. The breakdown 
of this total cost value by compliance cost for each provision is as 
follows: approximately 59 percent is attributable to exposure 
monitoring; 21 percent to medical surveillance; 15 percent to exposure 
controls (engineering, improved maintenance and repair, and 
administrative controls); 5 percent to respiratory protection and 
incorporating ASTM F3387-19. Of the annualized compliance cost of $90.3 
million, the MNM sector will incur $82.1 million (approximately 91 
percent) and the coal sector will incur $8.2 million (approximately 9 
percent).
    Under a discount rate of 3 percent, the total monetized benefits of 
the new respirable crystalline silica final rule from avoided deaths 
and morbidity cases, including the benefits of avoided morbidity 
preceding mortality, are $246.9 million per year in 2022 dollars. The 
net quantified benefits of the final rule are calculated as the 
difference between the estimated benefits and costs. MSHA estimates 
that the net annualized benefits of the final rule, using a discount 
rate of 3 percent, is $156.6 million.
    In addition to these quantified benefits, there are unquantified 
benefits. MSHA believes that the medical surveillance program will help 
miners to detect silica-related diseases early. Early detection of 
illness often leads to early intervention and treatment, which may slow 
disease progression and/or improve health outcomes. However, MSHA lacks 
data to quantify these additional benefits. Furthermore, MSHA expects 
that there will be additional benefits from replacing ANSI Z88.2-1969 
with ASTM F3387-19. The ASTM standard reflects developments in 
respiratory protection since the time in which MSHA issued its existing 
standards. The updated standard will play a critical role in 
safeguarding the health of miners, reducing their exposures to 
respirable crystalline silica and other airborne contaminants. Again, 
due to a lack of data, MSHA did not quantify the expected additional 
benefits that would be realized by requiring respiratory protection

[[Page 28357]]

programs consistent with the ASTM F3387-19 standard.
    The standalone FRIA contains detailed supporting data and 
discussions for the summary materials presented here, including the 
profile of the mining industry, estimated costs and benefits 
attributable to the final rule, the assessment of the economic 
feasibility of the final rule for the mining industry, and the 
evaluation of regulatory alternatives. The standalone FRIA is placed in 
the rulemaking docket at www.regulations.gov, docket number MSHA-2023-
0001. The summary of the standalone FRIA is presented below.
    The FRIA includes several revisions made since the PRIA. In 
response to public comments on the proposed rule and PRIA, MSHA revised 
its cost and benefit estimates. The revisions increased both the 
estimated costs and benefits.
    Four types of changes were made to the cost and benefit estimates. 
First, the final rule includes several changes from the proposed rule, 
and these changes affected estimated costs. The changes include: 
additional time provided by MSHA for mine operator compliance; 
revisions to exposure monitoring requirements including removal of the 
use of objective data and historical sample data to discontinue 
sampling; the requirement for mine operators to immediately report all 
exposures above the PEL from operator sampling to the MSHA District 
Manager or other designated office; revisions to the requirement for 
periodic evaluations to include additional evaluations whenever changes 
are made; the requirement of respiratory protection for MNM mines when 
engineering controls are being developed and implemented, or it is 
necessary by the nature of the work performed; and changes to the 
medical surveillance requirements for MNM operators related to the 
compliance date and a new requirement for reporting miners' chest X-ray 
results to NIOSH.
    Second, MSHA revised the FRIA methodology to annualize compliance 
costs over 60 years, which is the regulatory time horizon for this 
analysis. The 60-year analysis period starts with the first day of 
compliance for the coal sector (12 months after publication of the 
final rule). Coal mine operators incur compliance costs beginning 12 
months after publication of the final rule. MNM mine operators incur 
compliance costs beginning 24 months after publication of the final 
rule. The analysis period ends 60 years after the first day of 
compliance for the coal sector, thus 60 years of compliance costs for 
coal mine operators and 59 years of compliance costs for MNM mine 
operators are included in the analysis. MSHA also updated both 
compliance costs and benefits to reflect 2022 dollars using the GDP 
implicit price deflator.
    Third, MSHA made several changes to the PRIA cost estimation 
methodology; for example, the Agency modified its assumption about the 
proportion of the miner workforce that would be sampled in larger 
mines, as well as its assumption about the number of corrective 
actions, to account for circumstances in which multiple corrective 
actions may be necessary to reduce miners' exposure to below the PEL. 
MSHA also revised estimates of maintenance and repair and 
administrative control costs each year.
    Lastly, MSHA made some changes to the PRIA benefit estimation 
methodology. Changes were also made to the benefit estimates. As 
discussed in Section VI. Final Risk Analysis Summary, the PRA 
underestimated benefits from the proposed rule by excluding future 
retired miners from the number who would benefit. Both the FRA and the 
FRIA are updated to account for benefits for working miners and future 
retired miners. It is important to note that the FRIA only monetizes 
benefits to future retired miners--i.e., retired individuals who were 
employed as miners at least one year after the start of implementation. 
The FRIA methodology does not attribute any health benefits to 
individuals who retired before the start of implementation of the final 
rule. The FRIA reflects the fact that the number of future retired 
miners increases gradually after the start of implementation. For 
example, in the first year after the start of implementation, there 
will be no retired miners who benefit from the rule. In the second year 
after the start of implementation, there will be one cohort of retired 
miners who benefit from the rule (i.e., those in their final year of 
mining when implementation began). In this way, the FRIA monetizes 
benefits to future retired miners while accounting for the fact that 
future retired miners who benefit from the rule increase in size 
gradually during the 60-year analysis period.

B. Miners and Mining Industry

    This section provides information on the characteristics of the MNM 
and coal mining sectors, including their estimated revenues, number of 
mines in each sector, commodities the industry produces, and employment 
sizes. In addition, this section provides the respirable crystalline 
silica exposure profiles for miners across different occupational 
categories in the MNM and coal sectors. These data come from the U.S. 
Department of the Interior (DOI), U.S. Geological Survey (USGS); U.S. 
Department of Labor (DOL), Mine Safety and Health Administration 
(MSHA), Educational Policy and Development and Program Evaluation and 
Information Resources; DOL, Bureau of Labor Statistics (BLS), 
Occupational Employment and Wage Statistics (OEWS); U.S. Census Bureau, 
Statistics of U.S. Businesses (SUSB); and the Energy Information 
Administration (EIA).
    In general, economic profiles were developed using 2019 data 
because this was the most recent year available that was not impacted 
by temporary changes resulting from the COVID-19 pandemic. To estimate 
the current number of miners, MSHA used the 2019 Quarterly Employment 
Production Industry Profile (MSHA, 2019a) and the 2019 Quarterly 
Contractor Employment Production Report (MSHA, 2019b). MSHA estimated 
the number of and type of mines using 2019 data from the Mine Data 
Retrieval System, including the Mines database, (MSHA, 2022d) and the 
2019 employment data (MSHA, 2019a,b).
    The size of the mining industry is difficult to forecast given the 
uncertainties in future demand for various mined commodities, as well 
as uncertainties about technological changes. MSHA assumed the current 
mining workforce and the current number of mines would not change 
during the 60 years following implementation of the final rule. If the 
industry were to contract or expand in the future, the relative ratio 
of benefits to costs would remain roughly the same because both the 
benefits and costs of the final rule are in proportion to the size of 
the industry.
1. Structure of the Mining Industry
    The mining industry can be divided into two major sectors: (1) MNM 
mines and (2) coal mines, with further distinction made regarding type 
of operation (i.e., underground mines or surface mines) and commodity. 
The MNM mining sector is made up of metal mines (e.g., copper, iron 
ore, gold, silver, etc.) and nonmetal mines. Nonmetal mines can be 
further categorized into four commodity groups: (1) nonmetal (mineral) 
materials such as clays, potash, soda ash, salt, talc, and 
pyrophyllite; (2) stone, including granite, limestone, dolomite, 
sandstone, slate, and marble; (3) crushed limestone; and (4) sand and 
gravel, including industrial sands.
    MSHA categorizes mines by size based on employment. For purposes of

[[Page 28358]]

this industry profile and the FRIA analyses, MSHA categorized mines 
into the following four size groups: \78\ (1) 1 to 20 miners; (2) 21 to 
100 miners; (3) 101 to 500 miners; and (4) 501 or more miners.
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    \78\ Miner employment is based on the information submitted 
quarterly through the MSHA Form 7000-2, excluding Subunit 99--Office 
(professional and clerical employees at the mine or plant working in 
an office); https://www.msha.gov/sites/default/files/Support_Resources/Forms/7000-2_0.pdf (last accessed Jan. 10, 2024).
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    MSHA tracks mine characteristics and maintains a database 
containing the number of mines by mine type and size, number of 
employees, and employee hours worked. MSHA also collects data on the 
number of independent contractor firms who provide miners to the 
industry, the number of contract miners they employ, and their employed 
contract miners' hours worked. Contract miners may work at any mine.
    Table IX-1 presents an overview of the mining industry, including 
the number of MNM and coal mines, their employment (excluding contract 
miners), and their estimated revenues by commodity and size. As 
mentioned above, all data regarding the number of miners and mines are 
current in reference to the year 2019 and are assumed to remain 
constant during the 60 years following the implementation of the final 
rule. Estimated revenues are also based on 2019 data but have been 
inflated to 2022 dollars using the GDP implicit price deflator (U.S. 
Bureau of Economic Analysis, 2023).
    The MNM mining sector is comprised of an estimated 11,525 mines 
which employ an estimated 169,070 individuals, of which 150,928 are 
miners (excluding contract miners) and 18,142 are office workers. In 
addition, contract miners work an estimated 71.3 million hours in MNM 
mines each year.
    The coal mining sector is comprised of an estimated 1,106 mines 
that employ an estimated 52,966 individuals, of which 51,573 are miners 
(excluding contract miners) and 1,393 are office workers. In addition, 
contract miners work an estimated 28.0 million hours in coal mines each 
year.
    A further breakdown of MNM mines and coal mines by mine commodity 
and mine size is provided below.
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BILLING CODE 4520-43-C
a. Metal Mining
    There are 24 groups of metal commodities mined in the U.S. Metal 
mines represent an estimated 2.4 percent (280/11,525) of all MNM mines 
and employ an estimated 24.5 percent of all MNM miners (excluding 
contract miners). Of these 280 estimated mines, 157 (56.1 percent) 
employ 20 or fewer miners and 22 (7.9 percent) employ greater than 500 
miners. Additionally, MSHA data show that there is an estimated total 
of 13,792 contract miners in the metal mining industry with an 
estimated 18.9 million reported production hours in a year.
b. Non-Metal (Mineral) Mining
    There are 35 non-metal commodities mined in the U.S., not including 
stone and sand and gravel. Non-metal mines represent an estimated 7.8 
percent (897/

[[Page 28360]]

11,525) of all MNM mines and employ an estimated 15 percent of all MNM 
miners (excluding contract miners). The majority of non-metal mines 
(71.9 percent) employ fewer than 20 miners and less than 1 percent 
employ more than 500 miners. According to MSHA data, there are an 
estimated 11,346 contract miners in the non-metal mining industry with 
an estimated 14.5 million reported production hours in a year.
c. Stone Mining
    The stone mining subsector includes eight different stone 
commodities. Of these eight, seven are further classified as either 
dimension stone or crushed and broken stone. Stone mines make up an 
estimated 20.9 percent (2,409/11,525) of all MNM mines and employ an 
estimated 23.4 percent of all MNM miners (excluding contract miners). 
The majority of these mines (83.1 percent) employ fewer than 20 miners 
and one mine employs over 500 miners. According to MSHA data, there are 
an estimated 18,559 contract miners in the stone mining industry with 
an estimated total of 18.8 million reported production hours in a 
single year.
d. Crushed Limestone
    Crushed limestone mines make up an estimated 16.2 percent (1,862/
11,525) of all MNM mines and are estimated to employ about the same 
percentage (16.0 percent) of all MNM miners (excluding contract 
miners). Of the 1,862 crushed limestone mines, the vast majority (83.5 
percent) employ fewer than 20 miners; none employ over 500 miners. 
Additionally, MSHA data show that there are an estimated 9,065 contract 
miners in the crushed limestone mining industry with an estimated total 
of 10.2 million reported production hours in a single year.
e. Sand and Gravel Mining
    Sand and gravel mines account for an estimated 52.7 percent (6,077/
11,525) of all MNM mines and employ an estimated 21.1 percent of all 
MNM miners (excluding contract miners). Nearly all (96.7 percent) 
employ fewer than 20 employees; none employ over 500 miners. MSHA data 
show that there are an estimated 7,512 contract miners in the sand and 
gravel mining industry with an estimated 8.9 million production hours 
in a single year.
f. Coal
    Of the estimated 1,106 total coal mines, an estimated 63.9 percent 
(707/1,106) employ fewer than 20 miners and 1.1 percent employ more 
than 500 miners. Overall coal mine employment is estimated to be 
52,966, of which 51,573 are miners (excluding contract miners) and the 
remaining 1,393 are office workers. Additionally, there are an 
estimated total of 22,003 contract miners in the coal mining industry 
with an estimated 28.0 million reported production hours in a single 
year.
2. Economic Characteristics of the Mining Industry
    The value of all MNM mining output in 2022 dollars was estimated at 
$95.1 billion (U.S. Department of Interior, 2019). Metal mines, which 
include iron, gold, copper, silver, nickel, lead, zinc, uranium, 
radium, and vanadium mines, contributed $30.5 billion. In the USGS 
Mineral Commodity Summaries, production values for nonmetals, stone, 
sand and gravel, and crushed limestone are combined into one commodity 
group titled ``industrial minerals.'' Therefore, MSHA estimated the 
production value of each individual commodity by taking the proportion 
of revenues for the commodity in question among all commodities in the 
2017 SUSB and applying that proportion to the 2019 production value for 
all industrial minerals reported by USGS. This approach yields the 
following estimates: non-metal production is valued at an estimated 
$22.3 billion, stone mining at $14.6 billion, crushed limestone at 
$14.4 billion, and sand and gravel at $10.2 billion.
    The U.S. coal mining sector is made up of three major commodity 
groups: bituminous, anthracite, and lignite. According to MSHA data, 
bituminous operations represent approximately 92.1 percent of total 
coal production in short tons and employ 91.9 percent of all coal 
miners (excluding contract miners). Anthracite operations represent 0.4 
percent of coal production and employ 1.9 percent of coal miners 
(excluding contract miners). Lignite operations represent roughly 7.5 
percent of total coal production and employ 6.2 percent of coal miners 
(excluding contract miners).
    To estimate coal revenues in 2019, MSHA combined production 
estimates with unit prices. Mine production data were taken from MSHA 
quarterly data and the coal unit prices per ton were taken from the 
2019 EIA Annual Coal Report. Estimated revenues were then inflated to 
2022 dollar values using the GDP implicit price deflator. As shown in 
Table IX-1, 2019 total coal revenues expressed in 2022 dollars totaled 
an estimated $29.1 billion.
3. Respirable Crystalline Silica Exposure Profile of Miners
    Using the quarterly employment data submitted by mines and the 
Occupational Employment and Wage Statistics (OEWS) reported by the BLS, 
MSHA estimated the distribution of miners (excluding contract miners) 
across different occupational categories. For contract miners, MSHA 
lacked information on occupational categories. However, based on MSHA's 
program experience, MSHA assumed that the distribution of contract 
miners across the different occupational categories mirrors that of the 
miners (excluding contract miners) in each of the two sectors. For 
example, MSHA assumed that, because 1.9 percent of MNM production 
miners are drillers, 1.9 percent of contract miners working in MNM 
mines are also drillers.
    As discussed in Section VI. Final Risk Analysis Summary, full-time 
equivalents (FTEs) are used to account for the fact that miners may 
experience more or less than 2,000 hours of exposure to respirable 
crystalline silica per year. MSHA calculates the number of miner FTEs 
by dividing the estimated total number of hours worked across all mines 
in a given sector by 2,000 hours. Based on these calculations, MSHA 
estimates 184,615 FTEs in the MNM sector of which 148,966 (81 percent) 
are miner FTEs (excluding contract miners) and the remaining 35,649 (19 
percent) are contract miner FTEs (Table IX-2). For the coal sector, 
MSHA estimates 72,768 FTEs of which 58,764 (81 percent) are miner FTEs 
(excluding contract miners) and the remaining 14,004 (19 percent) are 
contract miner FTEs.

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[GRAPHIC] [TIFF OMITTED] TR18AP24.157

    MSHA's exposure data is described in Section VI. Final Risk 
Analysis Summary. In summary, MSHA used compliance data from 2005 
through 2019 to estimate the current levels of exposure to respirable 
crystalline silica among MNM miners (MSHA, 2022b). For the coal sector, 
MSHA used data from 2016-2021 (MSHA, 2022a). For the coal sector, MSHA 
only used exposure data since 2016, by which time all provisions of the 
Coal Mine Dust Standard had gone into effect. MSHA did not use earlier 
data so that the benefits in this FRIA are clearly attributable to this 
final rule and not to the Coal Mine Dust Standard.
    MSHA distributed the respirable dust samples in its MNM and coal 
exposure datasets by occupational category and exposure interval. 
Because exposure data associated with individual miners are not 
available, MSHA derived the imputed exposure profile of miners and 
miner FTEs stratified by occupational category and exposure interval. 
Based on this imputation, MSHA found that, in the MNM sector, an 
estimated 13,242 miners (6 percent), including contract miners, 
currently have respirable crystalline silica exposures above the 
existing PEL of 100 [micro]g/m\3\, an estimated 37,966 (18 percent) 
have exposures above the new PEL of 50 [micro]g/m\3\, and an estimated 
77,736 (37 percent) have exposures at or above the action level of 25 
[micro]g/m\3\. On an FTE basis, an estimated 11,579 miner FTEs (6 
percent), including contract miner FTEs, have respirable crystalline 
silica exposures above the existing PEL of 100 [micro]g/m\3\, an 
estimated 33,146 (18 percent) have exposures above the new PEL of 50 
[micro]g/m\3\, and an estimated 67,946 (37 percent) have exposures at 
or above the action level of 25 [micro]g/m\3\.
    In the coal sector, an estimated 1,406 miners (2 percent), 
including contract miners, currently have respirable crystalline silica 
exposures above the existing PEL of 85.7 [micro]g/m\3\, an estimated 
4,080 (6 percent) have exposures above the new PEL of 50 [micro]g/m\3\, 
and an estimated 13,971 (19 percent) have exposures at or above the 
action level of 25 [micro]g/m\3\. On an FTE basis, the figures are 
similar with an estimated 1,391 miner FTEs (2 percent), including 
contract miner FTEs, having respirable crystalline silica exposures 
above the existing PEL of 85.7 [micro]g/m\3\, an estimated 4,035 (6 
percent) having exposures above the new PEL of 50 [micro]g/m\3\, and an 
estimated 13,818 (19 percent) having exposures at or above the action 
level of 25 [micro]g/m\3\.

C. Cost Analysis

    The FRIA assesses the costs in the MNM and coal sectors of reducing 
miners' exposures to silica to 50 [mu]g/m\3\ for a full-shift exposure, 
calculated as an 8-hour TWA and the costs of complying with the final 
rule's other requirements.
    Under the final rule, mine operators are required to: implement 
exposure controls (Sec.  60.11); conduct exposure monitoring and report 
all samples over the PEL to MSHA (Sec.  60.12); take immediate 
corrective actions and provide miners with respirators when a sampling 
result indicates that miner exposure exceeds the PEL (Sec.  60.13); 
respiratory protection is required as a temporary measure for all MNM 
miners when MNM miner exposure exceeds the PEL while engineering 
controls are being developed and implemented or when it is necessary by 
the nature of work involved (for example, occasional entry to hazardous 
atmospheres to perform maintenance or investigation) (Sec.  60.14)(a); 
make periodic medical examinations available to MNM miners and ensure 
certain medical results are reported to NIOSH (Sec.  60.15); develop or 
revise existing respiratory protection programs and practices in 
accordance with the ASTM F3387-19 (Sec. Sec.  56.5005, 57.5005, and 
72.710); and retain records for the specified durations (Sec.  60.16).
    MSHA estimates the annualized costs of the final rule range from 
$88.8 million to $92.4 million, depending on the discount rate used 
(Table IX-3). Of this total, about 91 percent will be incurred by mine 
operators in the MNM sector and 9 percent by mine operators in the Coal 
sector. The difference in cost between the MNM and coal sectors is 
driven by the much larger number of MNM mines, as well as differences 
in mine size and the extent to which current exposures are already 
below 50 [mu]g/m\3\. In addition, MNM mine operators will incur costs 
to meet the medical surveillance requirements which further drives the 
difference in total costs between the MNM and coal sectors.

[[Page 28362]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.158

    For the PRIA, MSHA estimated annualized costs would range from 
$56.2 million (0 percent discount rate) to $60.0 million (7 percent 
discount rate). However, the estimated compliance costs for the PRIA 
were calculated in 2021 dollars. To compare PRIA and FRIA costs on an 
equivalent basis, MSHA inflated estimated PRIA compliance costs from 
2021 dollars to 2022 dollars, which increases PRIA costs by about 7 
percent. In 2022 dollars, estimated PRIA costs range from $60.1 million 
(0 percent discount rate) to $64.2 million (7 percent discount rate). 
Annualized estimated FRIA compliance costs exceed PRIA costs by about 
$28.2 to $28.7 million per year.
    After accounting for the inflation to 2022 dollars, the remaining 
difference in estimated compliance costs between the PRIA and FRIA are 
attributable to several changes to the proposed rule, including:
     A longer phase-in implementation is provided for both coal 
and MNM mines.
     Objective data and historical sample data may no longer be 
used to demonstrate compliance with exposure monitoring requirements.
     Sample results exceeding the PEL must be reported to the 
MSHA district manager or other designated office.
     Periodic evaluations must be conducted at least every 6 
months or whenever there is a change in: production; processes; 
installation or maintenance of engineering controls; installation or 
maintenance of equipment; administrative controls; or geological 
conditions.
     Limited temporary use of respirators is permitted in MNM 
mines only.
     For medical surveillance, the first medical examination 
offered to all MNM miners must be within 12 months of the compliance 
date. Also, chest X-ray results must be reported to NIOSH.
    Under the FRIA, annualized costs are attributable to the following 
provisions of the final rule:
     Exposure Monitoring ($53.2 million, 59 percent of total)
     Exposure Controls ($13.7 million, 15 percent of total)
     Respiratory Protection ($3.3 million, 4 percent of total)
     Medical Surveillance ($18.8 million, 21 percent of total), 
and
     ASTM Update ($1.2 million, 1 percent of total).
    Nearly two-thirds of the increase in estimated compliance costs 
($19.0 million) is attributable to the exposure monitoring requirements 
under the final rule. The remainder is largely attributable to 
increased estimates for exposure controls ($7.5 million) and 
respiratory protection ($2.2 million). MSHA expects that the amount of 
sampling performed by mine operators will increase because the final 
rule does not allow mine operators to use objective data and historical 
sample data (operator and MSHA sample data from prior 12 months) to 
demonstrate compliance with exposure monitoring requirements. Below the 
estimate of each cost component is discussed in more detail.
1. Costs for Exposure Monitoring
    There are five types of exposure monitoring required under the 
final rule:
     First-time sampling and second-time sampling based on a 
representative fraction of miners (Sec.  60.12(a)). First-time sampling 
occurs starting by the rule's respective compliance dates for coal 
mines and MNM mines. Second-time sampling occurs within three months of 
first-time sampling.
     Above-action-level sampling of a representative fraction 
of miners. If the most recent sampling results are at or above the 
action level (Sec.  60.12(a)), above-action-level sampling starts three 
months after the most recent sampling and continues until two 
consecutive samples demonstrate that miners' exposures are below the 
action level.
     Corrective actions must be performed for samples over the 
PEL. The mine operator must take corrective actions to reduce exposure 
and conduct corrective actions sampling until sample results are at or 
below the PEL (Sec.  60.12(b)). All corrective actions sample results 
exceeding the PEL must be immediately reported to the MSHA District 
Manager or other office designated by the District Manager.
     Periodic evaluations (qualitative monitoring) must be 
performed at least every 6 months, or whenever there is a change in 
production, processes, engineering or administrative controls, or 
geological conditions that may reasonably be expected to result in new 
or increased respirable crystalline silica exposures to ensure that any 
change will not have increased miners' exposures (Sec.  60.12(c)).
     If the periodic evaluations conducted under Sec.  60.12(c) 
determine that increased exposures are likely, post-evaluation sampling 
must be conducted to ensure exposures remain at or above the action 
level (Sec.  60.12(d)).
    For quantitative monitoring, MSHA estimates total sampling costs as 
a function of several factors: the unit cost of sampling, made up of 
labor costs (miners' and external consultants' time and hourly wage), 
laboratory costs for analyzing the samples, and clerical costs for 
recording the results; the number of samples that constitutes the 
required representative fraction each time the operator conducts 
sampling; and the frequency with which operators are assumed to carry 
out different types of monitoring (samplings and evaluation). MSHA 
assumes that regardless of the type of sampling, the unit cost of 
sampling does not vary, since the process of collecting a dust sample 
and

[[Page 28363]]

analyzing for respirable crystalline silica is relatively similar at 
different mines. For the qualitative monitoring, MSHA estimates 
periodic evaluation costs as a function of labor costs and the 
frequency of evaluation. The calculation of each of these factors is 
discussed below.
Labor Costs of Exposure Monitoring
    The most important component of sampling and evaluation cost is the 
time required to conduct the activities. For sampling, this includes 
the time needed to prepare for sampling, take the samples, and perform 
recordkeeping tasks on the results. Sampling takes time, which is 
valued at the hourly wage of the person wearing the sampling equipment 
and the person conducting the sampling. To err on the side of 
overestimates, MSHA assumed that in MNM mines, sample preparation and 
collection is performed by an industrial hygienist (IH).\79\ The IH may 
be an in-house specialist or an external consultant. For coal mines, 
miners certified to perform sampling under 30 CFR 70.202, 71.202, and 
90.202 can conduct the sampling required under the final rule.
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    \79\ In reality, some MNM mines may train their miners or other 
in-house employees to conduct sampling. In such scenarios, an IH 
would not be used and the labor cost of sampling would be based on 
the loaded hourly wage for the participating employee.
---------------------------------------------------------------------------

    In addition, MSHA assumed the personnel conducting sampling can 
collect 2, 3, and 4 samples per day at small, medium, and large mines, 
respectively. This determines the number labor hours needed to complete 
sampling at a mine, and therefore directly affects labor costs.
    Sampling labor costs: For coal mines, MSHA estimates sampling labor 
cost at $398 per sample at mines with 20 or fewer employes; $264 per 
sample at mines with 21 to 500 employees; and $248 per sample at mines 
with more than 500 employees. For metal mines, MSHA estimates sampling 
labor cost at $747 per sample for mines with 20 or fewer employes; $380 
per sample at mines with 21 to 500 employees; and $334 per sample for 
mines with more than 500 employees. For nonmetal mines, MSHA estimates 
sampling labor cost at $772 per sample at mines with 20 or fewer 
employees; $366 per sample at mines with 21 to 500 employees; and $322 
per sample at mines with more than 500 employees. These figures include 
the recordkeeping costs specified below.
    Evaluation labor costs: MSHA estimates that a periodic evaluation 
will typically require two hours of time for an IH. Thus, the cost 
ranges from $131 to $162 per evaluation.
Laboratory Analysis Costs of Sampling
    MSHA estimates that laboratory analysis will cost the mine operator 
$150 per sample. This includes the cost of packing and shipping the 
sample to the lab, the laboratory analysis, and reporting sample 
results to the operator.
Recordkeeping Cost of Sampling
    The labor time required for recording results of sampling is 
estimated at 17 minutes and is valued at the loaded hourly wage of an 
industrial hygienist. Thus, costs for recordkeeping time due to 
sampling range from $19 to $23 per sample.
Number of Samples--Representative Sampling
    While the cost of labor time and laboratory analysis are the 
primary components of cost per sample, a second major determinant of 
sampling cost at any mine is the number of samples required each time 
sampling occurs. Where several miners perform the same tasks on the 
same shift and in the same work area, the mine operator may sample a 
representative fraction (i.e., at least two) of these miners to meet 
the sampling requirements. The final rule requires that mine operators 
sample a representative fraction of miners who are expected to have the 
highest exposure to respirable crystalline silica. MSHA estimated the 
number of miners considered a representative sample based on the size 
of the mine. In small mines that employ 20 or fewer miners (including 
contract miners), MSHA assumes that a sample comprising at least 50 
percent of miners will be necessary to collect a representative sample. 
In medium-sized mines with 20 to 100 miners, the assumption is that a 
minimum 25 percent of miners will need to be sampled for the sample to 
be representative. In large mines with 100 or more miners, the Agency 
assumes that a minimum 15 percent of miners will need to be sampled for 
the sample to be representative.
Frequency of Exposure Monitoring--Number of Samples and Evaluations
    The third component of sampling cost is the frequency with which it 
must be performed. Sampling frequency depends on sample results, as 
specified by MSHA's exposure monitoring requirements.
    First-time and second-time sampling. First-time and second-time 
sampling is performed by all mine operators. First-time sampling occurs 
by the relevant compliance date for existing mines. Second-time 
sampling occurs within 3 months following first-time sampling. First-
time and second-time sampling is representative sampling. The number of 
samples taken at a mine will depend on the size of the mine. After the 
first-time sampling is completed, each operator will determine the next 
action based on the first sample result. If that result is below the 
action level, the mine operator will have to conduct the second 
sampling. If the results from both samplings are below the action 
level, no further sampling is required, unless there are changes 
identified by periodic evaluations that may reasonably be expected to 
result in new or increased respirable crystalline silica exposures. 
(Periodic evaluations are further discussed below.) The second-time 
sampling must be taken after the operator receives the results of the 
first-time sampling but no sooner than 7 days after the prior sampling 
was conducted.
    Above-action-level sampling. Sampling above the action level is 
also representative. Unlike first- and second-time sampling, this type 
of sampling will not be required of all mines, but only of those mines 
showing exposure levels at or above the action level of 25 [mu]g/m\3\. 
This sampling continues as long as the most recent sample results 
demonstrate exposure at a mine is at or above the action level of 25 
[mu]g/m\3\ but below the new PEL of 50 [mu]g/m\3\.
    MSHA estimated the percent of samples exceeding the action level in 
Year 1 based on its exposure profile developed using the Agency's 
compliance sampling data. MSHA assumed that mine operators will reduce 
the percentage of samples exceeding the action level from their current 
level of 31 percent to about 15 percent of samples by Year 7.
    Corrective Actions Sampling. Corrective actions sampling is 
required when a sample result exceeds the new PEL. A sample result 
above the PEL requires the mine operator to take corrective actions and 
conduct corrective actions sampling to determine if the actions reduced 
exposures to the PEL. MSHA uses the estimated number of samples 
exceeding 50 [mu]g/m\3\ to estimate the number of corrective actions 
taken. Each sample result above the PEL requires a corrective action 
and an additional sample to ensure that the corrective action was 
effective. Not all corrective actions may be effective in reducing 
exposures below the PEL. Therefore, MSHA increased the number of 
samples exceeding the new PEL by 25 percent to account for situations 
requiring more

[[Page 28364]]

than one corrective action taken by mine operators.
    Periodic Evaluation. MSHA assumed that mines operating only two 
quarters or less per year will conduct this evaluation once per year, 
while mines operating more than two quarters per year will perform this 
evaluation twice per year.
    However, because the rule requires periodic evaluation whenever 
factors change that may affect exposures, some mines, such as portable 
mines, will likely have to conduct evaluations more frequently than 
semi-annually. Therefore, MSHA increased its estimate of the number of 
periodic evaluations by 20 percent (i.e., annual periodic evaluations 
are equal to 2.4 times the number of mines) to account for mines that 
will need to perform evaluations more than twice per year.
    Post-Evaluation Sampling. Periodic evaluation may lead to sampling 
performed for purposes of evaluating whether exposure levels might have 
changed or if they remain below the action level. MSHA assumed that 
post-evaluation sampling comprises 2.5 percent of miners. This 
percentage is relatively small because mine operators are already 
collecting sample data which can be used for these purposes. However, 
MSHA estimated that some additional sampling might be needed and 
included additional post-evaluation sampling costs.
    Table IX-4 summarizes how the costs of each type of monitoring 
measures are estimated.
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[GRAPHIC] [TIFF OMITTED] TR18AP24.159

    Table IX-5 below presents the estimated number of samples by 
sampling type and by commodity sector in the first 7 years of the 
analysis because MSHA expects a long-run average to be reached in Year 
7. MSHA projects that in the first 2 years (following the coal and MNM 
compliance dates), 259,059 samples will be taken compared to 92,663 per 
year in Years 7 through 60. This is a result of: (a) declines in first-
time and second-time sampling after the first year of compliance, and 
(b) declines in above-action-level and corrective actions sampling as 
mine operators become more experienced in developing and implementing 
new controls.

[[Page 28366]]

    First-time and second-time sampling. Of the 259,059 samples 
expected to be taken in the first 2 years following the coal and MNM 
compliance dates, MSHA projects that approximately 60 percent (154,680/
259,059) will be from first-time and second-time sampling. After Year 1 
for Coal, and Year 2 for MNM, all first-time and second-time sampling 
will only be performed by new mines. MSHA projects that about 2 percent 
of mines in any given year will be new entrants to the mining industry, 
although the total number of mines in each year remains roughly 
constant.
[GRAPHIC] [TIFF OMITTED] TR18AP24.160


[[Page 28367]]


[GRAPHIC] [TIFF OMITTED] TR18AP24.161


[[Page 28368]]


[GRAPHIC] [TIFF OMITTED] TR18AP24.162

    Above-action-level sampling. MSHA projects that the number of 
above-action-level samples will increase from 5,423 in Year 1 to 48,275 
in Year 2 and to 79,062 in Year 3 as more mines start their above-
action-level sampling. This type of sampling is projected to decline 
starting from Year 4, due to the implementation of engineering 
controls, maintenance and repair of controls, and implementation of 
administrative controls, all of which will result in fewer miners and 
contract miners with exposure levels at or above the action level. MSHA 
projects that by Year 7, about 45,000 samples per year will be taken.
    Corrective actions sampling. MSHA also projects that the number of 
corrective actions samples--those taken after corrective actions, to 
ensure exposures have been reduced to below the new PEL--will be 46,912 
in Year 3. This figure is also projected to decline over time, to 
27,743 by Year 7.
    Evaluations. MSHA projects that starting with Year 2 following 
implementation, 12,631 mines will take about 28,308 evaluations per 
year.
    Post-evaluation sampling. Similarly, post-evaluation sampling 
remains constant at approximately 16,953 samples per year since these 
samples are independent of the above-action-level sampling.
Total Annualized Exposure Monitoring Costs
    Table IX-6 below presents estimated total annualized exposure 
monitoring costs by type of monitoring and mining sector. The five 
types of exposure monitoring (samplings and evaluation) are projected 
to cost mine operators an average of about $53.2 million (3 percent 
discount rate) per year over 60 years. The first-time and second-time 
sampling ($4.2 million per year) account for about 8 percent of 
exposure monitoring costs; above-action-level sampling ($23.5 million) 
accounts for 44 percent; corrective actions sampling ($14.9 million) 
accounts for 28 percent; and periodic evaluations and post-evaluation 
sampling ($10.7 million) together account for about 20 percent. Of the 
total exposure monitoring costs, about 89 percent are expected to be 
incurred by MNM mines and the remaining 11 percent by coal mines.

[[Page 28369]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.163

BILLING CODE 4520-43-C
    Several commenters disagreed with MSHA's estimates for sampling 
costs (Document ID 1419; 1441; 1442; 1448) in the PRIA. For example, a 
mining trade association NSSGA provided estimates from several mine 
operators that exposure monitoring costs would be substantially higher 
than those reported in MSHA's PRIA (Document ID 1448). This commenter 
provided sampling costs ranging from a low of $139 to a maximum of 
$1,800 per sample, with a median of $650 per sample, that would 
increase costs by $34 million to $162 million for 250,000 MNM miners. 
This commenter further stated that sampling costs vary according to the 
number of miners sampled: $2,866 for one miner, but $3,247 for 3 miners 
(approximately $1,082 per miner). A second commenter, a MNM mine 
operator/owner Vanderbilt Minerals, LLC, listed costs in excess of 
$11,000 for a single 3-day sampling event (Document ID 1419). A third 
commenter, an industry trade association EMA, stated that 400 of its 
446 employees would require 1,200 individual samples over the course of 
one year to meet the sampling requirements (Document ID 1442). A fourth 
commenter, NVMA, stated that one of its members estimated sampling 
costs would increase by $1.2 million for its 7,000 employees (Document 
ID 1441).
    MSHA acknowledges that the range of costs per sample provided by 
commenters likely exceeds MSHA's own estimates. As explained earlier, 
and in greater detail in Section 4 of the standalone FRIA document, 
MSHA's calculations of the average unit costs of sampling, sample 
analysis, and evaluation take into account the labor cost of time spent 
sampling, laboratory fees for sample analysis, lost work time due to 
sampling, recordkeeping time, plus the cost of performing periodic 
evaluations. MSHA assumes that the labor cost of sampling varies by 
commodity and mine size. MSHA estimates that mine operators will take 
5.76 million samples at a cost of $3.09 billion over the 60-year 
analysis period. MSHA estimated the weighted average (mean) cost at 
$500 per sample, with costs ranging from $250 per sample (for coal 
mines with more than 500 employees) to $750 per sample (for metal mines 
with 20 or fewer employees). A direct comparison with the cost 
estimates provided by the above commenter (NSSGA) is not possible 
because NSSGA presents the median but not the mean cost per sample from 
the organization's members who provided data. Because the distribution 
of costs provided by this commenter is skewed towards higher values, 
the mean cost is likely to exceed the median value. Thus, these data 
suggest the sampling costs provided by the commenter are probably 
falling within the range of MSHA's estimates.

[[Page 28370]]

    However, MSHA estimates sampling costs of a ``typical'' mine for 
the purpose of this analysis.\80\ NSSGA presented costs of $1,800 per 
sample, $2,866 for sampling one miner, and $3,247 for sampling 3 miners 
are not necessarily inconsistent with MSHA's cost estimates. For 
example, the operator who lists costs exceeding $11,000 for a 3-day 
sampling episode did not provide the number of miners sampled or the 
number of samples taken in that sampling episode. Using MSHA's lowest 
estimate of $330 per sample for a mine with more than 500 miners, this 
estimate is equivalent to about 33 samples, which is not unreasonable 
for three, 10-hour days of sampling. The commenter's cost estimate of 
$11,000 over 3 days is consistent with MSHA's estimate.
---------------------------------------------------------------------------

    \80\ Industry-wide, a ``typical'' mine is considered as a small 
surface mine, most likely to produce MNM commodity. Such a mine: 
would likely have a small number of buildings, such as a maintenance 
shop, an office, and a couple of storage; might employ up to 50 
miners plus managerial and office staff; and would likely have a 
crusher and screening plant, a conveyor, and several pieces of heavy 
equipment and haulage vehicles.
---------------------------------------------------------------------------

    MSHA acknowledges that some mine operators will incur higher 
sampling costs than the operator of a ``typical'' mine. MSHA believes 
that some small mine operators may experience higher sampling costs 
than MSHA estimates due to operating in remote areas where it may be 
more difficult to procure sampling services, and to the size of the 
mine. MSHA estimates the labor cost per sample at a small MNM mine will 
be nearly twice the cost per sample at larger MNM mines. Under MSHA 
estimates, the percentage of miners needed to achieve representative 
sampling (50 percent) is twice as large as the percentage at larger 
mines (25 percent or less).
    MSHA was unable to determine from the information provided by 
commenters, how they determined a representative sample and the 
frequency of samples taken. For example, the range of values provided 
by the NSSGA was based on ``more than 20 companies.'' However, there 
are more than 6,000 sand and gravel mines affected by the rule, and it 
is unclear whether this cost data represents the whole sector.
    MSHA's estimated cost per sample is largely influenced by a mine's 
need to hire a sampling professional. Some mines might perform their 
own sampling, others may hire a sampling professional (e.g., industrial 
hygienist); and others may use a combination of the two, based on 
sample timing, numbers of samples, and mine location. In estimating 
sampling costs, MSHA assumed half of the MNM samples would be collected 
in house and half collected by a sampling professional. MSHA considers 
that mine operators (or controllers) will evaluate the costs of options 
and make the most cost-effective decision. The Agency's estimated 
average cost per sample collected by a contracted industrial hygienist 
is nearly equivalent to the high-end cost examples provided by some 
commenters. Differences are attributable assumptions made on travel 
time and expense, numbers of samples collected per day, numbers of days 
per trip (over which travel time and expense are averaged). To the 
extent that more remote mines are able to coordinate through a local, 
state, or national industry association, insurance carrier, their 
common mine controller, or other affiliation, these costs can be 
reduced by coordinating sampling dates. In addition, organizations and 
associations provide training on conducting air sampling. A trained 
technician working under an experienced industrial hygienist can reduce 
sampling costs.
    Estimated total sampling costs from some commenters are much higher 
than MSHA's estimates because they assume more miners would have to be 
sampled than MSHA estimated under the proposed rule. For example, NSSGA 
estimated that at a cost per sample of $139 per sample, industry costs 
will increase by $34 million, while its median cost of $650 per sample 
will increase industry cost by $162 million (Document ID 1448). This 
commenter appears to have multiplied the cost per sample by its 
estimated number of affected miners, 250,000. Similarly, EMA mentioned 
an operator who assumes that 400 of 446 employees would be sampled 
(Document ID 1442), while a member mentioned by the NVMA appears to 
assume that all, or at least the vast majority of its 7,000 employees 
would be sampled (Document ID 1441).
    In response to public comments, MSHA increased its estimate of the 
number of samples operators would need to take to meet the sampling 
requirements of the final rule by increasing the number of samples that 
constitutes the required representative fraction (or sampling 
representativeness) and frequency of sampling and evaluation. For 
example, over the first six years starting from the start of 
implementation, MSHA now estimates 758,000 samples of all types will be 
taken (Table IX-5), compared to 499,000 under the proposed rule.
    Based on exposure profiles for the MNM and coal mining industries 
and MSHA's experience and knowledge of the mining industry, MSHA 
expects that on average the ratio of samples to miners sampled will be 
smaller than estimated by commenters. The final rule allows mine 
operators to sample a representative fraction of miners to meet the 
rule requirement. That is, a mine operator would be required to sample 
a minimum of two miners where several miners perform the same tasks on 
the same shift and in the same work area, so not all miners working in 
the same mine need to be sampled. Additionally, this sampling will stop 
when sampling results demonstrate exposure at a mine is below the 
action level. In Section 8.2.2 of the standalone FRIA document, MSHA 
provides two examples of how representative sampling will reduce the 
number of samples required based on MSHA experience in exposure 
sampling at mines and occupation categories.
    MSHA has determined that exposure monitoring requirements in the 
final rule are necessary to maintain exposure levels at a safe level to 
ensure miners' health. The exposure monitoring requirements are also 
consistent with the Mine Act's statutory purpose to provide improved 
health protection for miners. Section 8.2.2 of the standalone FRIA 
document outlines a number of steps mine operators can take to reduce 
their monitoring cost.
2. Costs for Exposure Controls
    To estimate the installation cost and to determine which mines will 
likely incur exposure control costs to reach compliance with the new 
PEL, MSHA analyzed the most recent 5 years of data on silica exposure 
(2015-2019 for MNM and August 2016-July 2021 for coal). As a starting 
point, it assumed that a mine will incur costs to meet the new PEL if 
it had a single sample result that exceeded the new PEL from the most 
recent day for which sample results were available. Analysis of the 
data yielded an initial estimate that 9.7 percent of all mines would 
incur costs, as reported in the PRIA. In response to public comments, 
MSHA updated this estimate to reflect the likelihood that more mines 
would incur additional costs of exposure controls. Based on its 
analysis and experience, MSHA projects in this FRIA that each year, 
about 20 percent of mines will incur some type of exposure control 
costs under the final rule.
    MSHA estimated three types of exposure control costs, as described 
in the following sections:
     Installation costs, consisting of the costs of purchasing 
new engineering control equipment and installing it or

[[Page 28371]]

purchasing new services to clean or ventilate dust from work areas.
     Maintenance and repair costs, to ensure proper use of 
existing engineering controls with increased frequency of dust control 
maintenance and repair.
     Costs of administrative controls to reduce dust exposure 
(for example, the costs of training or posting signage regarding new 
policies).
    Breaking down the total by type of cost, each year 5 percent of 
mines are expected to incur additional amortized installation costs, 
while 20 percent (that 5 percent plus an additional 15 percent) are 
expected to incur additional maintenance and repair costs and costs for 
administrative controls.
Costs for New Engineering Controls
    Some affected mines will incur installation costs because they will 
need to implement additional engineering control measures to reduce 
exposure levels. Using historical data and institutional knowledge, 
MSHA estimates the number of mines, by size, that will require 
additional engineering controls to meet the new PEL and the estimated 
level of capital investment (i.e., minimal, moderate, and large) 
needed. It projects that 580 mines--or a little under half of those 
with exposures above the new PEL at the time of their most recent 
sampling--will require these additional engineering controls, with a 
large majority requiring minimal capital expenditure. (Table IX-7).
[GRAPHIC] [TIFF OMITTED] TR18AP24.164

    MSHA estimates an average cost for engineering controls based on 
NIOSH evaluation of the dust controls used in the mining industry. MSHA 
assumed operating and maintenance (O&M) costs to be 35 percent of 
initial capital expenditure and assumed that installation cost, when 
appropriate, will be equal to initial capital expenditure. MSHA assumed 
most controls will have a 10-year service life, with exceptions for 
some equipment. For example, heavy haulage and excavating machinery are 
assumed to have a 15-year service life, and new or substantially 
renovated structural ventilation systems are assumed to have a 30-year 
service life. Within each category of capital expenditures, MSHA takes 
an average of the engineering control costs, inclusive of installation, 
maintenance, capital, and replacements costs over the 60-year analysis 
period and annualized the costs. Each affected mine is assigned the 
average value for its capital expenditure category. At a 3 percent 
discount rate, annualized costs range from $556 per mine for the lowest 
cost tier of capital equipment to $24,345 per mine for the highest cost 
tier. The annualized cost is $2,573 per mine per year when averaged 
across all mines.
    Table IX-8 presents total annualized engineering costs calculated 
at $1.43 million (0 percent) to $1.58 million (7 percent) over 60 
years.

[[Page 28372]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.165

Costs for Maintenance & Repair of Engineering Controls
    Beyond adopting more advanced engineering control infrastructure, 
an integral method of reducing respirable crystalline silica exposure 
is by increasing the frequency of maintenance and repairs for dust 
control systems. In MSHA experience, when there are overexposures, 
often engineering controls are in place but the operator has neglected 
maintenance and repair. MSHA has determined that, when the appropriate 
dust control systems are used, effective and regular maintenance and 
repair of such systems can help reduce respirable crystalline silica 
exposure below the new PEL. Maintenance and repair activities are 
usually conducted at the beginning of each shift (or as frequently as 
necessary) and can be a part of existing safety and operational checks 
performed on most equipment.
    MSHA estimates, on average, that mine operators would spend 16 
hours per quarter on additional inspection and maintenance (i.e., 64 
hours per year). To account for additional maintenance and repair costs 
that would result from using inspection checklists to cover maintenance 
and repair of dust suppression and control equipment, MSHA added 25 
percent to the costs for maintenance and repairs. These maintenance and 
repair costs will be incurred every year over a 60-year analysis 
period, resulting annual cost of $3,389 per mine for MNM and $4,789 per 
mine for coal.
    MSHA anticipates that additional mines will incur increased 
maintenance and repair costs each year to reduce exposure below the 
action level to avoid exposure monitoring costs. MSHA assumes that in 
total, these maintenance and repair costs will be incurred by 19.7 
percent of mines, or 2,489 mines (2,249 MNM mines and 241 coal mines). 
These mines include the 4.7 percent that will incur new installation 
costs, plus an additional 15 percent that will incur only maintenance 
and repair costs and costs of administrative controls. MSHA assumes 
that this is the share of mines industrywide that will incur costs in 
each year, even as the specific mines incurring those costs may vary 
from year to year. Multiplying the average maintenance and repair cost 
per mine by the estimated 2,489 mines that will incur costs ranging 
from $8.65 million (0 percent discount rate) to $8.27 million (7 
percent discount rate) for increased maintenance and repair (Table IX-
9).

[[Page 28373]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.166

Costs for Administrative Controls
    Administrative controls comprise a variety of methods to reduce 
exposure to respirable crystalline silica dust. In general, mine 
operators evaluate situations in which exposure can be reduced through 
changes in policies and work practices, and implements those changes by 
informing miners through training, published announcements, procedures, 
instructions, and signage. Examples of administrative controls include 
enclosing cabs to work with doors and windows shut and setting speed 
limits and minimum distances for equipment operated on dusty haul 
roads.
    While many of these examples are applications of common-sense 
policies, they can be circumvented either accidently or deliberately. 
Administrative controls are not always effective, or as effective as 
they could be, because unlike engineering controls, administrative 
controls depend on miners' adherence to the policies and work 
practices. Administrative controls rank lower than engineering controls 
in the hierarchy of effectiveness.
    The cost of administrative controls is composed of labor hours. 
MSHA believes that 2,489 mines will spend, on average, 16 labor hours 
on administrative controls starting in Year 1 for coal and Year 2 for 
MNM of the 60-year analysis period. As with the estimates of additional 
maintenance and repair costs, this figure for number of affected mines 
is based on MSHA's assumption that, beyond those mines with exposures 
currently above the new PEL, an additional 10 percent of mines might 
incur increased administrative costs each year to reduce exposure to 
below the action level.
    In addition to the time spent identifying administrative controls, 
mine staff need to prepare and publish training and instructional 
materials, and post signage and/or other informational materials to 
implement such controls; to account for this, MSHA increases the value 
of labor hours by a factor of 2.0. MSHA estimates that the additional 
labor costs spent on administrative controls as an average of the 
loaded hourly wage rate weighted by the relative employment of these 
occupations in the mining industry. The estimated average cost is 
$1,439 per affected MNM mine (Year 2--60) and $2,222 per coal mine 
(Year 1--60).
    Table IX-10 shows the estimated number of mines and annual costs 
expected to be incurred in Year 1 and Years 2 through 60 for 
administrative controls. Additionally, Table IX-11 shows that total 
annualized costs range from $3.7 million (0 percent discount rate) to 
$3.6 million (7 percent discount rate) based on the discount rate used. 
The higher totals for the MNM sector are attributable to the much 
larger number of affected mines than the coal sector.
[GRAPHIC] [TIFF OMITTED] TR18AP24.167


[[Page 28374]]


[GRAPHIC] [TIFF OMITTED] TR18AP24.168

    Several commenters did not agree with MSHA's exposure control 
estimates as applied to their mines, stating that MSHA underestimated 
the costs of implementing exposure controls (Document ID 1419; 1441; 
1448; 1455), and/or asserted that most mine operators who meet the 
current PEL will need to install significant new engineering controls 
to meet the new PEL. For example, Nevada Mining Association, stated 
that estimated compliance costs for one of their members was $22.7 
million for the first year and $13.6 million for each following year to 
retrofit mobile equipment with filtered pressurized air as well as 
medical surveillance and exposure sampling costs (Document ID 1441). 
NSSGA stated that ``[b]ased on communications with 13 member companies, 
costs for exposure controls will vary widely, but on average are 
$920,000 annually, with a median of $225,000 (Document ID 1448).'' 
Neither the types of controls nor the number of mines installing the 
controls was included with the commenter's estimate. One of NSSGA's 
members also stated that its 2023 budget for exposure controls is 
approximately equal to the MSHA annual estimate for all of MNM. Another 
commenter, US Silica, stated that in 2023 alone, it incurred $3.6 
million in capital costs on two automated projects and multiple other 
projects exceeding MSHA's estimate for the industry (Document ID 1455). 
A fifth commenter, Vanderbilt Minerals, LLC provided expected costs of 
$7 million for a list of renovations to existing facilities and new 
equipment purchases (Document ID 1419).
    Based on its analysis of the Agency's sampling database, MSHA 
believes roughly 90 percent of mines will be able to meet the PEL 
without incurring additional costs. In Section 4 of the standalone FRIA 
document, MSHA estimates that about 1,230 mines are expected to incur 
exposure control costs to meet the new PEL. Of these, a little more 
than 50 percent (650 mines) should be able to meet the new PEL using 
controls such as additional maintenance and repair, and administrative 
controls. The remaining 47 percent of mines (580 mines) expected to 
incur costs will also implement engineering controls--in addition to 
increased maintenance, repair, and administrative costs--to meet the 
new PEL.\81\ The distinction between the two types of mines is related 
to sample data that shows compliance with the existing PEL. 
Additionally, MSHA includes an extra 10 percent of total mines (111 
coal mines and 1,153 MNM mines) that will incur exposure control costs, 
including enhanced administrative controls and frequent maintenance and 
repair. MSHA's analysis is described in more detail in the standalone 
FRIA. Twenty operators commented that MSHA underestimated exposure 
control costs. A couple of these commenters did not provide specific 
evidence to support their position that many operators will incur 
substantial engineering control costs.
---------------------------------------------------------------------------

    \81\ The maintenance, repair, and administrative costed for the 
additional 1,260 mines are not to meet the new PEL but to reduce 
exposures below the action level to reduce monitoring costs.
---------------------------------------------------------------------------

    MSHA assumes that all mines are currently in compliance with the 
existing PEL when estimating compliance costs. Costs incurred by 
operators are attributed to lowering exposures from the existing PEL to 
the new PEL. Some mine operators have found it difficult to 
consistently control exposures to meet the existing PEL; any additional 
costs incurred by them will be more appropriately attributed to 
maintaining compliance with the existing PEL.
    The estimated costs presented in the standalone FRIA represent the 
average estimated compliance costs for a typical mine. MSHA 
acknowledges that the exposure control costs will differ depending on 
the size of the mine, the current level of exposure to respirable 
crystalline silica, existing engineering and administrative controls, 
the mine layout, work practices, and other variables. MSHA's price and 
cost estimations are based on a variety of sources including market 
research and MSHA's experience and sample data. The evidence provided 
by the commenters was collected from members of trade organizations. It 
appears that at least some of the cost estimates are from either very 
large mines--far larger than the ``typical'' mine used for MSHA cost 
estimates--or may reflect an estimate for all mines controlled by an 
operator. For example, the comment that the ``total amount to retrofit 
all underground and surface mobile equipment with filtered pressurized 
air, medical surveys and increased sampling is $22.7 million for the 
first year, and $13.6 million each year after'' is from an MNM operator 
with 7,000 employees. If this represents a single mine, only 26 MNM 
mines (0.2 percent) employed more than 500 miners in 2019 (Table IX-1), 
if this represents multiple mines, then the anticipated compliance 
costs per mine would be smaller. Because the number of mines is 
unknown, and because the commenter includes sampling costs (provided 
separately as $1.2 million per year) and medical surveillance costs in 
the total, it is impossible to meaningfully compare this estimate with 
MSHA's estimates.
    Similarly, US Silica presented costs exceeding $3.6 million in 
capital expenditures on two automated projects; totaling all projects, 
US Silica states it exceeded MSHA's estimate for the entire industry 
(Document ID 1455). However, it is unclear how many mines owned by US 
Silica incurred the costs. In addition, US Silica installed two 
automated systems. Generally, an automated bagging operation is more 
costly to purchase and install than a manual bagging system. The higher 
capital cost of an automated system also likely results in offsetting 
cost savings (e.g., labor costs), and thus US Silica's estimated 
compliance costs likely include decisions made for other business 
reasons, not just the cost of reducing worker exposure.
    Vanderbilt Minerals LLC provided expected costs of $7 million for 
renovations to existing facilities and new equipment purchases at a 
single site, including ``the purchase/installation of such items as a 
new

[[Page 28375]]

bagging system for 50-pound bags, new dust collectors for drying/
milling equipment, renovation of a laboratory, office, break room, mill 
control office, and crusher operator booth, purchase of larger water 
trucks and an increase in paved haul roads (Document ID 1419).'' In 
this case, the costs by the commenter are clearly higher than MSHA's 
estimated compliance costs for a single typical mine. However, the site 
in question appears to be highly atypical of most of MNM mining and 
therefore not appropriate for extrapolating industry costs. More 
details are provided in Section 8 of the standalone FRIA document.
    A further difficulty in evaluating commenters' estimates of 
engineering costs is that MSHA presents annualized costs; that is, 
compliance costs with initial capital and one-time costs amortized over 
the service life of the control. Many commenters provided first-year 
costs (without identifying capital, one-time, or recurring (operation 
and maintenance) cost components) to show that MSHA underestimated 
exposure control costs. The comparison of commenters' first-year costs 
with MSHA's annualized cost estimates is inappropriate. For example, a 
MNM mine operator provided $3.6 million as the first-year cost estimate 
without offering information about the actual service lives of these 
automation projects (Document ID 1455). If those costs are amortized at 
a 3 percent discount rate using an assumed 10-year service life 
(implying the system will be replaced 6 times over the course of the 
60-year analysis period), the annualized capital component of their 
cost is about $410,000; if the expected service life is 30 years 
(replaced twice over 60 years), the annualized cost is about $178,000. 
Similarly, when amortized using a 3 percent rate, a $7 million in 
initial capital cost is equivalent to less than $800,000 annualized 
cost per year if the system has a 10-year service life, and less than 
$400,000 if the service life is 30 years. Thus, it is difficult to 
directly compare MSHA's annualized costs with first-year costs provided 
by commenters without service life information.
    Small mine operators specifically questioned MSHA's estimates of 
the cost of controlling exposure to respirable silica crystalline 
silica dust (Document ID 1411; 1415; 1427; 1435; 1436). Water based 
dust suppression, especially if combined with magnesium chloride, is 
likely to be more expensive at some remote mines in arid regions due to 
the cost of obtaining and transporting water. However, these commenters 
did not discuss the applicability of other methods of reducing 
exposures presented in the FRIA and Technological Feasibility 
discussions. For example, operating vehicles with windows closed, 
reduced vehicle speed, and wider vehicle spacing have all been shown to 
decrease operator exposure to dust. These commenters provided the cost 
of cabin air filters and their preference to not use air conditioning, 
but it should be noted that there may be trade-offs in the choices mine 
operators make to reduce exposure to dust. For example, the use of air 
conditioning by vehicle operators will increase costs (filters, fuel 
use), but will decrease exposures. These increased operating costs 
should be offset by reduced sampling costs.
3. Costs for Respiratory Protection
    The new PEL may result in an increased use of respirators by miners 
when compared with usage under the existing PEL. This additional usage 
will result from provisions Sec.  60.13: Corrective actions and Sec.  
60.14 (a): Respiratory protection. Under Sec.  60.13, if sampling 
results indicate miners' exposure exceeds the new PEL, mine operators 
must make approved respirators available to affected miners; ensure 
that miners wear respirators properly during the period of 
overexposure; and take corrective actions to lower the concentration of 
respirable crystalline silica to at or below the PEL. Section 60.14 (a) 
requires the temporary use of respirators by MNM miners when 
engineering controls are developed and implement or when necessary due 
to the nature of work involved (e.g., entry into a hazardous atmosphere 
to perform maintenance). MSHA expects that additional use of 
respiratory protection will occur because exposure levels that were 
below the existing PEL will now be above the new PEL. MSHA believes 
that most respirator use will occur during the first few years after 
implementation of the rule until mine operators can consistently 
control sources of respirable crystalline silica dust exposure at the 
new PEL using engineering controls, but that the respirator use will 
decline as mines implement and improve additional controls. However, 
with little data to support an assumption concerning how quickly 
incremental respirator use might decline, MSHA chose to model 
respirator use as remaining constant over the 60-year analysis period.
    Under Sec.  60.13 MSHA believes that miners who are most likely to 
need incremental respirator use to perform corrective actions work in 
the following occupations:

 Kiln, Mill, and Concentrator Workers (MNM mines)
 Mobile Workers & Jackhammer Operators (MNM mines)
 Miners in Other Occupations (MNM mines)
 Underground Miners (Coal mines)
 Surface Miners (Coal mines)

    To estimate the number of miners who might be required to use 
respirators under Sec.  60.13, MSHA first uses sample data to estimate 
the number of miners in these occupations with respirable crystalline 
silica exposures between the new PEL and the existing standards (50 
[mu]g/m\3\ to 100 [mu]g/m\3\ range for MNM and 50 [mu]g/m\3\ to 85.7 
[mu]g/m\3\ for coal) to identify the miners most likely to increase 
their use of respirators as a result of the rule. MSHA then assumes 
that 20 percent of that total, about 2,109 miners would these miners 
end up using respirators as a result of the rule. MSHA thus estimates 
that mine operators will incur costs for increased respiratory 
protection by 1,984 MNM miners and 125 coal miners per year to meet the 
requirements of Sec.  60.13.
    Under Sec.  60.14, MSHA uses sample data to estimate the number of 
MNM miners that might need to increase their use of respirators due to 
the rule. MSHA assumes that MNM mine operators will need to provide 
additional respiratory protection for 20 percent of MNM miners in all 
occupations with exposures between the new PEL and the existing PEL. 
MSHA estimates MNM operators will need to provide respiratory 
protection to 4,945 MNM miners to meet the requirements of Sec.  60.14.
    Under sections 60.13 and 60.14 together, mine operators are 
expected to increase respirator protection for approximately 7,054 
miners and contract miners (6,928 MNM miners and 125 coal miners).
    MSHA estimates two types of respiratory protection costs: the 
purchase of new respirators to be issued and the incremental cost of 
additional temporary respirator use. MSHA believes that given the 
existing respiratory protection standards, most miners have already 
been issued respirators to deal with intermittent, temporary 
circumstances where exposures exceed the existing standards. However, 
some mine operators with miners at low risk of exceeding the existing 
standard may need to purchase respirators to account for possible 
temporary exposures in the range between the new PEL and existing 
standards. It is likely that some miners newly at risk for exposure in 
this range will not have respirators. In addition,

[[Page 28376]]

because respirators will be used more under the new PEL, respirators 
will deteriorate more quickly and need replacement. In addition to 
miners who did not need to wear a respirator under the existing 
standards but might have occasional temporary need for respiratory 
protection under the new PEL, some mine operators will need to replace 
respirators for miners more frequently due to a small increase in the 
need for temporary respiratory protection.
    MSHA assumes that in Year 1, coal mine operators will incur costs 
for new respirators for 50 percent of their coal miners who are 
expected to increase respirator use (i.e., a total of 63 new 
respirators) under Sec.  60.13. In Year 2, MNM mine operators will 
similarly incur costs for new respirators for 50 percent of the total 
MNM coal miners who are expected to increase their respirator use 
(i.e., 3,464 new respirators under Sec.  60.13 and Sec.  60.14 
combined). In Years 2 through 60 (for coal) and Years 3 through 60 (for 
MNM), mine operators will incur replacement costs for 50 percent of the 
total number of new respirators purchased in Year 1 (for coal) and Year 
2 (for MNM). Therefore, in Year 3 and onwards, coal and MNM mine 
operators will purchase a total of 1,763 new respirators per year. 
Furthermore, MSHA assumed that all new respirator purchases in any year 
throughout the analysis period will require fit testing and training.
    MSHA assumed that mine operators will purchase tight-fitting, re-
useable half-mask elastomeric respirators at a cost of $39.57 each plus 
$17.29 for filters.\82\ In addition, MSHA assumed respirators are 
assigned to individuals, not shared equipment. Furthermore, miners 
issued new respirators will require an additional 2 hours of labor time 
for fit testing and training which is valued at the weighted average 
loaded wage of all mine workers in the given sector ($50.60 for Metal 
miners, $40.47 for Nonmetal miners, and $49.97 for coal 
miners).83 84 The resulting annual cost per miner requiring 
a new respirator is estimated to be $145 for MNM miners and $157 for 
coal miners.
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    \82\ Based on online (non-discount) prices: websites for 
Northern Safety, 2022: $29.14/each 3MSeries 6500 half mask 
respirator, $10.25/pair for P100 pancake filters; and Grainger, 
2022: $50.00 for MSA 420 series half mask respirator, $24.32 for 
P100 filter cartridges (package of 2). Prices are higher end of 
potential range, supplier bulk discounts available from numerous 
other sources.
    \83\ OSHA APF rulemaking (update to 29 CFR 1910.134) Unit Costs: 
1 hour employee training, 1 hour employee qualitative fit testing. 
Alternatively, 2 hours for quantitative fit testing (from costs 
estimated in 2001-2006; may be reduced due to efficiency of more 
modern quantitative fit testing equipment currently available and 
widely used). MSHA assumed that worker fit testing is conducted in 
small groups; two to four miners are fit tested during the hour, but 
all remain part of the group for the full hour.
    \84\ MSHA assumed there will be no additional labor costs for 
personnel conducting fit testing or training because current 
respiratory protection programs already require these steps.
---------------------------------------------------------------------------

    Table IX-12 presents the estimated annual costs of purchasing new 
respirators for respiratory protection under the new PEL for miners who 
did not require respiratory protection under the existing PEL. In Year 
1 of compliance for coal mines, 63 coal miners (including contract 
miners), who occasionally perform corrective actions where they would 
likely be exposed to respirable crystalline silica in the range between 
the new PEL and the existing standards are expected to be provided with 
new respirators by mine operators t a cost of $9,821. In Year 1 of 
compliance for MNM mines (Year 2 following publication of the final 
rule), 3,464 MNM miners will also be provided with new respirators for 
corrective actions and temporary use at a cost to mine operators of 
$502,282. New respirator purchase costs in Year 1 of compliance for 
coal and MNM mine operators are estimated to total $512,103 across both 
sectors. In subsequent years (Years 2 through 60 for coal mines; Years 
3 through 60 for MNM mines), annual costs are expected to be about half 
of first year costs ($256,052).
[GRAPHIC] [TIFF OMITTED] TR18AP24.169

    Table IX-13 summarizes the total annualized cost of new respirator 
purchases by sector. Overall, the new PEL is expected to lead mine 
operators to purchase new respirators costing an average of $256,134 
(at a 0 percent discount rate) to $255,285 (at a 7 percent discount 
rate) per year over the 60-year analysis period.

[[Page 28377]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.170

    MSHA estimates the cost of additional respirator use under the new 
PEL for miners who did not need it under the existing standards. MSHA 
assumes the cost of additional respirator use starts in Year 1 (for 
coal mines) and Year 2 (for MNM mines) will remain constant over the 
60-year analysis period. On average, MSHA believes additional 
respirator use will be necessary for 4 hours per week per miner, or an 
additional 208 hours per year (4 hours per week x 52 weeks per year). 
For estimating costs, if an elastomeric respirator uses two filters at 
a time, and the filters last eight hours before requiring replacement, 
then these miners will need an additional 26 pairs of filters per year 
(208 hours per year/8 hours per filter pair). At an average price of 
$17.29 per pair of filters, mine operators will spend an additional 
$450 per miner per year ($17.29 x 26 filter pairs) for respirator 
filters.
    Table IX-14 and Table IX-15 present the estimated total annual and 
annualized cost of additional respirator usage by sector. The annual 
cost of additional temporary respirator use is expected to be $450 per 
miner per year over the 60-year analysis period (Table IX-14) and total 
annualized cost is expected to range from $3.12 million (0 percent 
discount rate) to $2.96 million (7 percent discount rate) per year 
(Table IX-15).
[GRAPHIC] [TIFF OMITTED] TR18AP24.171

[GRAPHIC] [TIFF OMITTED] TR18AP24.172

    The estimate presented in Table IX-15 may be an overestimate of the 
cost of respirator use. MSHA assumed respiratory use would remain 
constant over the 60-year analysis period, it is likely that need for 
additional respirator use will decline as mines implement and improve 
engineering and administrative controls. However, with little data to 
support an assumption concerning how quickly the need for additional 
respirators might decline, MSHA chose to model it as constant. Second, 
while most mines operate year-round, some mines may operate for as 
little as 3 months per year. This will also decrease the need for 
respirators use.

[[Page 28378]]

    Some commenters provided unit cost data for respirators and filters 
that were greater than the unit cost estimates that used in the PRIA 
(Document ID 1411; 1415; 1427; 1435; 1436). First, based on their data, 
the replacement filter cartridges last much longer than those costed by 
MSHA, so that the cost of one year's use will be lower than MSHA's cost 
estimate due to the long life span of replacement filters used by 
commenters. Second, the commenters assumed all employees would require 
new respirators and did not account for baseline use (or availability) 
of respirators at the mine. The final rule requires MNM mine operator 
to use respiratory protection as a temporary measure when miners must 
work in concentrations of respirable crystalline silica above the PEL 
when engineering control measures are being developed and implemented 
or necessitated by the nature of work involved. MSHA determined that 
its cost assumption is more comprehensive and likely overestimates 
respirator protection costs.
4. Cost for Medical Surveillance
    Under the final rule, MSHA will require each MNM mine operator to 
provide mandatory medical examinations to miners who are new to the 
mining industry and voluntary periodic examinations to all currently 
employed miners. These new medical surveillance standards extend to MNM 
miners the opportunity for medical surveillance that is already 
available to coal miners under the existing rules.
    The medical examinations will be provided by a physician or other 
licensed health care professional (PLHCP), or by a specialist. The 
medical examination will include a miner's medical and work history, a 
physical examination, a chest X-ray, and a pulmonary function test. For 
those miners new to the mining industry, the first mandatory 
examination must take place within 60 days after beginning employment. 
This must be followed by a mandatory follow-up examination at 3 years. 
Should the follow-up examination indicate any medical issues related to 
lung disease, a second mandatory follow-up examination must take place 
in 2 years. In addition to these mandatory examinations, mine operators 
must also offer voluntary periodic medical examinations to all MNM 
miners at least every 5 years. The first periodic medical examination 
for existing MNM miners must be provided within 12 months of the final 
rule's MNM compliance date, or if a MNM mine commences operation after 
the compliance date, within 12 months of the mine beginning operations. 
All of the medical examinations must be provided at no cost to the 
miner.
    Additionally, the MNM mine operator must ensure that, within 30 
days of the medical examination, the PLHCP or specialist provides the 
results of chest X-ray classifications to NIOSH, once NIOSH establishes 
a reporting system. The cost of the x-ray includes the cost of 
preparing the report and transmitting those results to NIOSH.
    To estimate the costs of compliance with the medical surveillance 
requirement, MSHA first estimated the ``unit cost'' of a single medical 
examination. MSHA then estimated how many examinations would occur in 
each year over the 60-year analysis period and multiplied the numbers 
of examinations by the unit cost to determine total costs in each year. 
MSHA summed the costs in each year to estimate a total cost over the 
full 60-year period.
Unit Costs
    MSHA assumed that all examinations entail the same cost elements 
(in decreasing order of cost): the physical examination, chest X-ray, 
spirometry test, lost work time while being examined, lost travel time, 
symptom assessment and occupational history, transportation cost, and 
recordkeeping of the mine operator. Table IX-16 displays estimated 
components in 2022 dollars, which sum to a unit cost of $628.58 per 
examination.
[GRAPHIC] [TIFF OMITTED] TR18AP24.173

    To estimate the number of examinations expected per year, MSHA used 
the estimated number of full-time equivalent (FTE) employees in MNM 
mining, which is 184,615 FTE workers. MSHA assumed that the MNM 
employment will remain constant over the 60-year analysis period 
following compliance of the medical surveillance requirement.\85\ MSHA 
estimates that the average length of employment as an MNM miner (before 
leaving the mining occupation) is 22 years, which is derived from a 
NIOSH survey that found the average mining experience of MNM miners is 
approximately 11 years.\86\

[[Page 28379]]

Based on this estimate, MSHA assumed that each year 8,392 miners (i.e., 
about 1/22, or 4.55 percent, of 184,615 FTE MNM miners) would leave the 
industry, and be replaced by the same number of new entering workers.
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    \85\ MSHA chose to express mine employment in FTEs for the 
benefits analysis because health impacts would differ between part-
time miners, who would experience less exposure to respirable 
crystalline silica dust and thus would be less likely to experience 
the same negative health effects in the same amount of time as 
miners who worked full-time or more. A similar logic applies to 
miners deciding whether to accept medical examinations, thus medical 
surveillance costs are also estimated based on FTE miners.
    \86\ The 2012 report by NIOSH, entitled, ``National Survey of 
the Mining Population: Part 1: Employees,'' includes the findings of 
its 2008 survey on mine operators and miners in the U.S. https://www.cdc.gov/niosh/mining/works/coversheet776.html (last accessed 
Jan. 10, 2024). Details on the survey methodology and results are 
available in the link. The NIOSH survey found the following mine 
experiences for different types of MNM mines, which average to about 
11 years (11.375 to be precise): metal mines, 10.7 years; nonmetal, 
12.0 years; stone, 12.5 years, and sand and gravel 10.3 years. For 
comparison, the same survey found the average mining experience for 
coal miners was 16.0 years. These averages reflected the average 
number of years that respondent miners had worked at mines at the 
time the survey was conducted. MSHA considered these average mine 
experiences to represent approximately one half of the mining tenure 
these miners would have (the years in mining when they leave). 
Conversely, MSHA estimated miners' total expected tenure to be twice 
these average mining experiences.
---------------------------------------------------------------------------

    MSHA estimates total medical surveillance costs over the 60-year 
analysis period under two different scenarios due to the uncertainty of 
how many currently employed miners will participate in voluntary 
medical surveillance programs. Assuming a participation rate of 25 
percent (Scenario 1), annualized costs range from $14.6 million (with a 
0 percent discount) to $14.0 million (with a 7 percent discount rate) 
and the annualized cost per MNM miner ranges from $79 (with 0 percent 
discount rate) to $76 (with a 7 percent discount rate).
    In scenario 2, MSHA assumed that the participation rate is 75 
percent. Annualized costs range from $23.7 million (0 percent discount 
rate) to $23.1 million (7 percent discount rate). The annualized cost 
per MNM miner range from $128 (7 percent discount rate) to $125 (0 
percent discount rate). A summary of estimated medical surveillance 
costs under the two scenarios is presented in Table IX-17.
[GRAPHIC] [TIFF OMITTED] TR18AP24.174

    Vanderbilt Minerals LLC stated that MSHA underestimated the cost of 
medical surveillance and stated its program cost approximately $9,400 
per site per year, plus an additional $4,000 per site per year in 
employee time at 3 hours per employee (Document ID 1419). Assuming an 
average loaded wage of a nonmetal sector extraction worker at $40.47 
per hour, $4,000 in employee time would cover 33 employees. This 
suggests that average medical surveillance costs would be about $406 
per employee by dividing total costs of $13,400 (= $9,400 + $4,000) per 
site by 33 employees.\87\ This is significantly lower than MSHA's 
estimated unit cost for medical surveillance of $629 per examination in 
2022 dollars (Table IX-16).
---------------------------------------------------------------------------

    \87\ The commenter does not state whether employee time is 
valued at a loaded hourly rate (including benefits and overhead) or 
the raw hourly rate. If the latter rate is used ($24.34 per hour), 
then the commenter's program would cover 55 employees at a cost of 
$244 per employee.
---------------------------------------------------------------------------

    Another commenter, National Mining Association, stated that the 
proposed medical surveillance requirements would impose significant 
costs on its members, due to the expansion to cover potentially 200,000 
MNM miners at more than 11,000 mines (Document ID 1428). As mentioned 
above, MSHA assumes that under the final rule, operators are required 
to conduct medical surveillance on currently employed miners and new 
miners (those who start to work on the mining industry for the first 
time). For currently employed miners, MSHA assumes two participation 
rates (25 percent and 75 percent) for medical surveillance and 
estimates the number of tests per year as 6,700 under 25 percent 
participation rate and 20,200 under 75 percent participation rate tests 
per year at an average cost of $4.24 million to $12.7 million each year 
(undiscounted). Average over the two participation rates, MSHA 
estimates that operators will conduct an average of 13,500 tests per 
year on the new miners at an average cost of $8.5 million each year 
(undiscounted).
    Commenters also shared concerns on medical surveillance costs for 
small mine operators (Document ID 1408; 1411; 1415; 1427; 1435; 1436). 
The specific issue raised by these commenters concerned the cost of 
hourly wages and travel expenses from remote mine locations to obtain 
medical examinations. Thus, their costs will be larger than estimated 
by MSHA. MSHA acknowledges these concerns but notes that commenters 
provided no specific data in support of their position.
    At least two commenters, NSSGA and Illinois Association of 
Aggregate Producers, stated that, under the proposed rule, companies 
would incur millions of dollars in costs that do not benefit miners' 
health and safety, using as examples requiring sampling every 3 months 
indefinitely for exposures between 25 [mu]g/m\3\ and 50 [mu]g/m\3\, 
requiring that medical surveillance be offered to miners with less than 
30 days a year of exposure to respirable silica at

[[Page 28380]]

or above the action level and requiring initial sampling even for 
facilities that have had exposure monitoring for decades (Document ID 
1448; 1456). MSHA has determined that on-going sampling and periodic 
evaluations are necessary to ensure that exposures to respirable 
crystalline silica meet the new PEL and that miners' health is 
protected. Exposure monitoring, that includes an action level, provides 
mine operators and miners with necessary information to take actions to 
prevent miners' overexposures. Allowing mine operators to cease 
monitoring once exposure is maintained below the action level provides 
operators with the incentive to reduce and maintain exposures below the 
PEL. For medical surveillance, MSHA believes it is important for MNM 
operators to provide medical surveillance so that MNM miners will have 
information about their health to take necessary action early to 
prevent any further progression of disease.
5. Cost for ASTM Update
    Under the final rule, mine operators are required to have a written 
respiratory protection program in accordance with the 2019 ASTM F3387-
19 standard. A written respiratory protection program must include: 
program administration; written standard operating procedures; medical 
evaluations; respirator selection; training; fit testing; and 
maintenance, inspection, and storage. Mine operators will compare the 
ASTM standard to their existing respiratory protection program or 
practices and identify the elements of their existing respiratory 
protection program or practices that need to be revised. MSHA evaluated 
the components of the 2019 ASTM standard that have the potential to 
impose additional costs on mine operators.
    MSHA assumes that 20 percent of MNM mines will incur costs to meet 
the 2019 ASTM standard each year. MSHA assumes that all coal mines are 
affected by the update to the 2019 ASTM standard because 30 CFR 
72.700(a) requires coal mine operators to make respirators available to 
their miners. This should be an overestimate because it is likely that 
many coal mines already meet the 2019 ASTM standard. MSHA assumes that 
only a small subset of miners uses respirators each year. MSHA assumes 
about 10 percent of MNM miners and 3.7 percent of coal miners are 
expected to be required to use respirators each year.
    Table X-18 presents the total number of mines compared to the total 
number of mines expected to incur compliance costs to update their 
respiratory protection program and practices. In Year 1, MSHA assumes 
that 1,106 coal mines will incur costs to update their respiratory 
protection program and practices to the 2019 ASTM standard, and 2,722 
coal miners and contract miners are expected to wear respirators. 
Starting in Year 2, MSHA estimates that 3,411 mines (i.e., 20 percent 
of the 11,525 MNM mines and 100 percent of the 1,106 coal mines) are 
expected to incur costs. In addition, MSHA estimates 6,946 miners and 
contract miners wear respirators each year, which represents less than 
2.5 percent of all miners including contract miners (6,946/284,778). 
Respirators are worn to protect miners from airborne contaminants 
(including respirable crystalline silica and coal dust) at a small 
percentage of mines each year and only a small fraction of the miners 
at those mines wear respirators.
[GRAPHIC] [TIFF OMITTED] TR18AP24.175

    MSHA evaluates the components of the 2019 ASTM standard that may 
impose additional costs on mine operators, and the assumptions in 
estimating those costs.
    Approved Respirators. Mine operators are familiar with MSHA's 
existing requirements for using NIOSH-approved respirators, and this 
analysis assumed that mine operators will not incur additional costs 
for these requirements. MSHA assumed recordkeeping primarily results in 
labor costs.
    Program Audit. Program costs for an annual review and written 
report by the program administrator are included with the annual labor 
time. A program administrator will perform the review and prepare the 
report. A second review in the form of an outside audit is conducted by 
a person not involved in the respirator program. The audit is to be 
repeated at a frequency determined by the complexity of the program.
    Written Standard Operating Procedures. MSHA assumes that most mines 
have established written Standard Operating Procedures (SOPs) that 
comply with the ASTM standard. MSHA assumed that 50 percent of affected 
mine operators will prepare new or updated SOPs at the start of 
implementation. Following this initial period, these costs will be 
incurred only by new mines.
    Medical Evaluations. Under this provision, mine operators would 
update the information provided to the PLHCP concerning each miner's 
work area, type and weight of respirator, duration and frequency of 
respirator use, work activities and environmental conditions, hazards, 
and other PPE worn. This information is assumed to be part of the 
miner's job description and personnel records (e.g., fit-test results) 
and is likely available electronically at most mines. As a result, the 
cost of this provision is associated with the requirement to document 
this information in the miner's records and transmit it to the PLHCP.
    Respirator Selection. The provisions for respirator selection in 
the 2019 ASTM standard reflect the current standard of care for 
respirator use in the U.S. In this analysis, MSHA assumed

[[Page 28381]]

that mine operators are already using these criteria for selecting 
respiratory protection. MSHA assumed that mine operators will not incur 
additional costs for this provision.
    Mine Operator Responsibilities. The 2019 ASTM standard provides 
that mine operators allow miners wearing respirators to leave a 
hazardous atmosphere for any reason related to the respirator. The mine 
operator will also investigate the cause of respirator failures and 
communicate with the respirator manufacturer and government agencies 
about defects. Respirator failures or defects are considered rare 
events. To account for the potential time involved should defective 
respirators be encountered, this analysis adds a minimal amount of 
labor time.
    Training the ``Respirator Trainer''. Under the 2019 ASTM standard, 
the respirator trainer will provide training to others with 
responsibilities for implementing the mine operator's respirator 
program, and therefore, this person must have an appropriate training 
or experience. For existing mines, this cost is unlikely to recur 
except when a respirator trainer leaves the mine operator's employment. 
However, it is likely to be incurred by the 2 percent of new mines 
entering the market in any given year.
    Training for the Mine Operator/Supervisor and the Person Issuing 
Respirators. The mine operator or supervisor of any miner who must wear 
a respirator must receive training on the elements of the respiratory 
protection program in the SOPs and related topics. The cost in the 
first year of compliance will also be incurred in subsequent years by--
at a minimum--new mines entering the market.
    Miner Training. Miners required to use respirators already receive 
training each year under the 1969 ANSI standard and under 30 CFR part 
46 and Part 48. Most mines incorporate this into their existing annual 
health and training plan, and therefore MSHA estimates that there are 
no incremental costs attributable to this provision.
    Fit Testing Frequency. The 2019 ASTM standard provides for annual 
respirator fit testing to ensure that the make, model, and size of the 
respirator issued to the miner are appropriate and the miner is still 
able to achieve a good face seal. MSHA assumed that, on average, miners 
receive annual fit testing under existing training standards. A 
provision under the 2019 ASTM standard is that the fit testing must be 
overseen by a trained technician or supervisor. The time of the trained 
supervisor is an additional cost incurred under this provision.
    Maintenance, Inspection, and Storage. The provisions for respirator 
selection in the 2019 ASTM standard reflect the current standard of 
care for respirator use in the U.S. In this analysis, MSHA assumed that 
mine operators are already using these criteria for maintaining, 
inspecting, and storing respirators. Therefore, MSHA assumed that mine 
operators will not incur additional costs for this provision.
    Table IX-19 presents average compliance costs per mine by sector. 
In Year 1, compliance costs average about $1,700 for coal mines. In 
Year 2, compliance costs average about $1,200 for MNM mines and $500 
for coal mines. In Years 3 and following, average compliance costs per 
mine are smaller, ranging from $262 for MNM mines to $479 for coal 
mines, with an overall average of $332 per mine.
    MSHA assumes that all mines are affected by the requirement to have 
a written respiratory protection program that meets the ASTM standard 
but not all mines are expected to incur costs for this requirement. 
MSHA estimates, in Year 1 (for coal mines) and Year 2 (for MNM mines), 
only 50 percent of affected mines are expected to incur costs under 
provision 2 (SOPs) because many mines already have SOPs that comply 
with the ASTM. In Years 2 through 60 (for coal) and Years 3 through 60 
(for MNM), the number of affected mines that would incur costs is 
smaller than in Years 1 and 2 because following Year 1 (for coal) and 
Year 2 (for MNM), additional compliance costs are expected to be 
incurred primarily by new mines entering the industry. For example, 
provisions related to written SOPs, Training for the Respirator 
Trainer, and Training for the Mine Operator and Person Responsible for 
Issuing Respirators are initial costs incurred in the first year of 
compliance. In subsequent years, those costs would generally be 
incurred only by the 2 percent of new mines entering the industry.
[GRAPHIC] [TIFF OMITTED] TR18AP24.176


[[Page 28382]]


    Below in Table IX-20 are the annualized costs associated with the 
ASTM requirement. The total annualized cost to the mining industry 
ranges from $1.18 million (0 percent discount rate) to $1.32 million (7 
percent discount rate), with 53 percent of those costs attributable to 
MNM mines and 47 percent attributable to coal mines.
[GRAPHIC] [TIFF OMITTED] TR18AP24.177

6. Cost Summary
    MSHA estimates that the annualized cost of the final rule will 
range from $88.8 million to $92.4 million in 2022 dollars. At a 
discount rate of 3 percent,\88\ 59.0 percent is attributable to 
exposure monitoring; 20.9 percent to medical surveillance; 15.1 percent 
to engineering, improved maintenance and repair, and administrative 
controls; 3.7 percent to additional respiratory protection (e.g., when 
miners need temporary respiratory protection from exposure at the new 
PEL when it would not have been necessary at the existing PEL); and 1.4 
percent related to the selection, use, and maintenance of approved 
respirators in accordance with ASTM F3387-19, respiratory protection 
practices (see Table IX-21).
---------------------------------------------------------------------------

    \88\ In its analysis, MSHA annualizes all costs using 3 percent 
and 7 percent real discount rates as recommended by OMB. Using a 7 
percent discount rate, the annualized cost of the rule is estimated 
at $75.4 million in 2022 dollars.
[GRAPHIC] [TIFF OMITTED] TR18AP24.178

    Given the larger size of the MNM sector and the higher proportion 
of samples in the MNM sector that are above 50 [mu]g/m\3\, most costs 
are attributable to MNM mines (see Table IX-1 and Table IX-2). Of the 
$90.3 million total, MSHA estimates that the MNM sector will incur 
$82.1 million (91 percent) and the coal sector will incur $8.2 million 
(9 percent) in annualized compliance costs (see Table IX-22).

[[Page 28383]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.179

    To estimate compliance costs, MSHA determined the expected measures 
necessary for mines to comply with each provision of the final rule 
then estimated the costs incurred by a typical mine to comply with each 
provision. These include one-time costs, such as those to purchase and 
install an engineering control, provide equipment expected to last 
multiple years (e.g., respirators), or devise and implement an 
administrative control. They also include recurring costs, such as the 
operating and maintenance (O&M) costs of using an engineering control 
or the value of the labor hours and supplies used to perform periodic 
exposure monitoring. To aggregate costs for each provision, MSHA 
multiplies the average cost per mine by the number of mines expected to 
incur that cost or the average cost per miner by the number of miners 
expected to be affected by the given provision. These costs are summed 
across all provisions for each of the two major mining sectors to 
estimate total industry costs. For purposes of the cost analysis, MSHA 
assumes employment is constant over this period.
    MSHA annualizes all costs using 3 percent and 7 percent discount 
rates as recommended by OMB.\89\ All costs and benefits are annualized 
over a 60-year analysis period. MSHA annualized benefits to reach the 
long-run steady state values projected in MSHA's FRA.\90\ Costs are 
also estimated and annualized over a 60-year period. This means that 
costs for durable equipment, for example, are estimated based on their 
expected service life. If the expected service life of a building 
ventilation system is 30 years, MSHA assumes that a mine operator would 
purchase the system in year 1 and again in year 31 to estimate 60 years 
of capital costs. This is the major change in costing methodology for 
the final rule. Under the proposed rule, MSHA annualized costs over 
shorter periods. Given the types of controls appropriate for meeting 
the requirements of the proposed rule, this approach was reasonable. 
Because MSHA set a 1-year difference between the compliance dates for 
the coal and MNM sectors under the final rule, that method is no longer 
accurate. MSHA's analysis of this final rule is based on a timeframe of 
60 years (which is enough time to analyze 45 years of working life and 
15 years of retirement for new miners who only experience exposures 
under the new PEL).
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    \89\ Discount rates throughout this section refer to real 
discount rates. Real discount rates are distinct from nominal 
discount rates because they do not include inflation.
    \90\ Technically, MNM benefits would not reach their long-run 
average values until 61 years following the compliance date for the 
coal sector since the compliance deadline for MNM is 1 year after 
the compliance deadline for coal.
---------------------------------------------------------------------------

    For both MNM and coal mines, the estimated costs to comply with the 
new PEL (50 [mu]g/m\3\) assumes that all mines are compliant with the 
existing PEL of 100 [mu]g/m\3\ for MNM mines (for a full shift, 
calculated as an 8-hour TWA) and 85.7 [mu]g/m\3\ for coal mines (for a 
full shift, calculated as an 8-hour TWA).
    Two mining trade organizations, American Exploration and Mining 
Association and Nevada Mining Association, stated that MSHA's cost 
projections were inaccurate because they predicted fixed costs based on 
gross proceeds (instead of net proceeds) (Document ID 1424; 1441). 
These commenters also noted that, because the cost model for each 
commodity differs, compliance costs for each commodity will differ. 
MSHA did not estimate compliance costs based on either gross or net 
proceeds. MSHA has determined that its approach better identifies 
likely costs than the approach recommended by the commenters. The 
Agency estimated compliance costs based on a wide range of quantitative 
and qualitative data including: sampling data on miner exposure, MSHA 
program experience, and MSHA's knowledge of typical controls, 
maintenance, and work practices at mines of different types and size. 
MSHA estimates compliance costs using mine size, labor cost, and other 
factors at commodity level, which is more flexible and accurate than 
the estimation of proceeds.
    One commenter, a mining-related business, stated that MSHA's cost 
estimates were based on flawed sampling data, that ``used samples taken 
by MSHA inspectors and then weighted these based on the number of 
samples plus exposures to the current standard (Document ID 1392). The 
commenter stated that powered haulage operators account for the bulk of 
samples, while conveyor operators account for the fewest samples, 
resulting in a ratio of about 1 conveyor operator to 79 powered haulage 
operators. The commenter stated that in its experience, the ratio is 
about 1 conveyor operator to 4 haulage operators. Because conveyor 
operators are underrepresented in the analysis, this would affect 
MSHA's cost estimates.
    As described in Part B--Miners and Mining Industry, MSHA used 2019 
OEWS data to estimate the number of miners in each occupational 
group.\91\ The OEWS is a nationally representative dataset and MSHA 
uses it to examine labor force in the mining industry. While BLS 
reported the number of workers under powered haulage operators, it did 
not report any employment in the OCC Code 53-7011 (Conveyor Operators 
and Tenders) due to an insufficient number of respondents identified as 
Conveyor Operators and Tenders.
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    \91\ OEWS data available at https://www.bls.gov/oes/ (last 
accessed Jan. 10, 2024).
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    The samples taken by MSHA inspectors were not weighted based on

[[Page 28384]]

the ``number of samples plus exposures to the current standard,'' as 
the commenter suggested, but rather by the estimated number of workers 
in each occupational group (Document ID 1392). MSHA took this approach 
because the samples taken by inspectors are not representative of all 
jobs at a mine, rather they are concentrated in areas where miners are 
at the greatest risk for dust exposure. The FRIA analysis is based on 
sample and employment data to provide an overview of all occupational 
groups and their associated risks for the mining industry.
    One commenter, N-Compliance Safety Services, Inc., stated that 
large mining company costs under the proposed rule would be in the 
millions of dollars annually, a figure that does not include the cost 
of citations, downtime, and contesting violations (Document ID 1383). 
Stating that the proposed rule's costs would drive up the costs of 
commodities and impact transportation needs and expenses, the commenter 
said that the proposed 25 [mu]g/m\3\ action level would place most 
mines in violation, as it is four times less than the current PEL and 
would require four times the actions to maintain compliance below it. 
Downtime to maintain controls is included in the cost of the final 
rule. In response to the comment from mine operators that the action 
level would place most mines in violation, MSHA clarifies that mine 
operators are not required to maintain exposures below the action 
level. The purpose of the action level is to alert mine operators and 
miners when exposures are approaching the PEL. Mine operators will be 
in violation if exposures exceed the new PEL. Mine operators who 
maintain exposures at or above the action and at or below the new PEL 
will incur sampling costs but will not be in violation of the final 
rule and will not be faced with citations, downtime, or contesting 
violations. MSHA notes that the commenter has provided no data to 
support their statement that the rule will cost large mining companies 
millions of dollars in compliance costs.

D. Benefit Analysis

    In the FRIA, MSHA estimates that, during the 60 years following the 
compliance date for the coal sector (i.e., the start of the timeframe 
for the cost analysis), annual benefits will gradually increase, as the 
share of miners' working lives under the new PEL (rather than the 
existing standards) increases.\92\ In the FRA, MSHA estimated the 
avoided cases attributable to the new PEL using a comparison of a 
population of miners exposed only under the new PEL to one exposed only 
under the existing standards throughout their working and retired 
lives. These benefits included reductions to excess cases of fatal 
silicosis, fatal non-malignant respiratory diseases (NMRD), fatal end-
stage renal disease, fatal lung cancer, and non-fatal silicosis. These 
five health outcomes were chosen based on their well-established 
exposure-response relationships with occupational respirable 
crystalline silica exposure.\93\
---------------------------------------------------------------------------

    \92\ Throughout this document, the term ``long-run'' refers to 
the period of time when all surviving working and retired miners 
will have only been exposed under the new PEL.
    \93\ The standalone Health Effects document and the FRA discuss 
the evidence for these relationships in depth, as well as the 
exposure-response models used for analysis in the FRA.
---------------------------------------------------------------------------

    In the FRIA, MSHA estimates and monetizes the excess morbidity and 
mortality cases avoided during the same 60-year analysis timeframe as 
considered by the cost analysis so that benefits can be directly 
compared with the costs of the final rule. The number of avoided cases 
presented in the FRIA during the 60-year analysis period is less than 
the number of lifetime cases avoided estimated in the FRA, since miners 
with exposure under the current limits are gradually replaced by miners 
with exposure under the new PEL during the 60 years following the start 
of implementation.
    In the PRA, MSHA underestimated the number of miners who would 
benefit from this rule. Based on the 2019 Quarterly Employment 
Production Industry Profile (MSHA, 2019a) and the 2019 Quarterly 
Contractor Employment Production Report (MSHA, 2019b), the current 
number of working miners full-time equivalents (FTEs) is assumed to be 
184,615 for MNM and 72,768 for coal.\94\ In the PRA, MSHA assumed 
excess cases of disease would be reduced only among these working 
miners. However, once the current mining workforce is replaced with new 
entrants to the mining industry so that the entire workforce has worked 
only under the new PEL for their 45-years of working life (i.e., 60 
years after the start of implementation), the future mining workforce 
will experience fewer excess deaths and illnesses from excess exposure 
to respirable crystalline silica. The PRA's methodology did not include 
the number of future retired miners who experienced lower exposures for 
their working lives under the final rule and will continue to benefit 
during their retirement, and therefore, the PRA underestimated the 
benefits attributable to the final rule.
---------------------------------------------------------------------------

    \94\ The analysis of this FRIA assumes the mining workforce will 
not change size during the 60 years following compliance with the 
rule to simplify estimation of health benefits. The current and 
long-term size of the mining workforce was estimated using 2019 
data, since the COVID-19 pandemic may have led to temporary changes 
in the mining workforce that will be reversed in coming years.
---------------------------------------------------------------------------

    Both the FRA and the FRIA are updated to account for benefits among 
both working miners and future retired miners. It is important to note 
that the FRIA only monetizes benefits to future retired miners--i.e., 
retired individuals who were employed as miners after the start of 
implementation. The FRIA methodology does not attribute any health 
benefits to individuals who retired before the start of implementation 
of the final rule. The FRIA is updated to reflect the number of future 
retired miners, which increases gradually after the start of 
implementation. For example, in the first year after the start of 
implementation, there will be no retired miners who benefit from the 
rule. In the second year after the start of implementation, there will 
be one cohort of retired miners (i.e., those in their final year of 
mining when implementation began). In this way, the FRIA monetizes 
benefits to future retired miners while accounting for the fact that 
future retired miners who benefit from the rule increase in size 
gradually during the 60-year analysis period.
    MSHA estimates that:
     For a population of working and retired miners exposed 
only under the new PEL, the final respirable crystalline silica rule 
will result in a total of 1,067 lifetime avoided deaths (982 in MNM 
mines and 85 in coal mines) and 3,746 lifetime avoided morbidity cases 
(3,421 in MNM mines and 325 in coal mines). These avoided cases will be 
achieved once all miners, working and retired, have been exposed 
exclusively under the new PEL (see Table IX-23).
     Over the first 60 years immediately following the start of 
implementation, fewer cases will be avoided than are shown in Table IX-
23. This is because the annual number of cases avoided will increase 
gradually to the long-run steady-state values, which ultimately will be 
achieved only when all miners have been exposed only under the new PEL. 
Table IX-24 shows that, in the first 60 years following the start of 
implementation, the final rule will result in a total of 531 avoided 
deaths (487 in MNM and 44 in coal) and 1,836 avoided morbidity cases 
(1,673 in MNM and 162 in coal), which are the benefits MSHA monetized 
in its FRIA. In general, the actual number of cases that will be 
avoided in the 60 years

[[Page 28385]]

following the start of implementation is approximately half the number 
of avoided cases once benefits reach their long-run average annual 
values (see Table IX-24).
     Under a discount rate of 3 percent, the total benefits of 
the new respirable crystalline silica rule from these avoided deaths 
and morbidity cases, including the benefits of avoided morbidity 
preceding mortality, are $246.9 million per year in 2022 dollars (see 
Table IX-25).
     Because a higher monetary value is placed on avoided death 
as compared to an avoided morbidity case, the majority (62.5 percent; 
$154.3 million) of these benefits is attributable to avoided mortality 
due to non-malignant respiratory disease (NMRD) ($75.4 million), 
silicosis ($40.3 million), and end-stage renal disease (ESRD) ($28.4 
million), and lung cancer ($10.2 million) (see Table IX-25).
    [cir] Benefits from avoided morbidity due to non-fatal silicosis 
are $72.8 million per year. Of this, $66.3 million are due to cases 
avoided in MNM mines and $6.5 million are due to cases avoided in coal 
mines (see Table IX-25).
    [cir] Benefits from avoided morbidity that precedes fatal cases of 
NMRD, silicosis, renal disease, and lung cancer, are $19.8 million. Of 
this, $18.2 million are due to cases avoided in MNM mines and $1.6 
million are due to cases avoided in coal mines (see Table IX-25).
BILLING CODE 4520-43-P
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[[Page 28386]]


[GRAPHIC] [TIFF OMITTED] TR18AP24.182

BILLING CODE 4520-43-C
    MSHA acknowledges that its benefit estimates are influenced by 
underlying assumptions and that the long timeframe of this analysis 
(i.e., 60 years) is a source of uncertainty. The main assumptions 
underlying these estimates of avoided mortality and morbidity include 
the following:
     Employment is held constant over the 60 years (i.e., the 
analysis period of the final rule).\95\
---------------------------------------------------------------------------

    \95\ MSHA recognizes that it is very challenging to predict 
economic factors over such a long period with high degrees of 
confidence. Given known information and forecast limitations, MSHA 
believes assuming constant employment is reasonable.
---------------------------------------------------------------------------

     For analyses under the ``Baseline'' scenario, any 
exposures to respirable crystalline silica above the existing standards 
(i.e., 100 [mu]g/m\3\ for MNM miners and 85.7 [mu]g/m\3\ for coal 
miners) were capped at 100 [mu]g/m\3\ and 85.7 [mu]g/m\3\ for MNM and 
coal exposures, respectively.
     For analyses under the ``New PEL 50'' scenario, any 
exposures to respirable crystalline above the new PEL are capped at the 
new PEL (i.e., 50 [mu]g/m\3\).
     Miners have identical employment and hence identical 
exposure tenures (i.e., 45 years).
    In addition to the above-mentioned quantified health benefits, MSHA 
expects that there will be additional benefits from requiring approved 
respirators be selected, fitted, used, and maintained in accordance 
with ASTM F3387-19. The ASTM standard reflects improved developments in 
respiratory protection since the time in which MSHA issued its existing 
standards. ASTM F3387-19 also includes respiratory protection program 
elements such as program administration; standard operating procedures 
(SOPs); medical evaluation; respirator selection; training; fit 
testing; and respirator maintenance, inspection, and storage.
    This provision of the final rule will ensure that, in circumstances 
where respirator use is required, mine operators will provide miners 
with respiratory protection that incorporates advances in technology 
and changes in respiratory protection practices. This respiratory 
protection will play a critical role in safeguarding the health of 
miners and reducing their exposures to respirable crystalline silica 
and other airborne contaminants. As demonstrated in the FRA, reductions 
in occupational exposure to respirable crystalline silica are expected 
to reduce adverse health outcomes. However, given the uncertainty about 
the current state of mine operator respiratory protection practices, 
MSHA did not quantify the expected additional benefits that would be 
realized by requiring approved respirators to be selected, fitted, 
used, and maintained in accordance with the requirements of ASTM F3387-
19.
    MSHA believes that reductions in coal miners' exposure to 
respirable crystalline silica may also lead to lower levels of coal 
mine dust inhalation. MSHA expects that adverse health outcomes 
attributable to respirable coal mine dust exposure, such as simple and 
complex coal workers' pneumoconiosis (CWP), will also be reduced. MSHA 
has not estimated the reduction in risk associated with CWP among coal 
miners because the literature does not contain an exposure-response 
model that quantifies the impact of respirable crystalline silica on 
CWP mortality risk, and because MSHA is not making any assumptions 
about whether levels of coal mine dust will be reduced due to the final 
rule. MSHA anticipates that there will be additional unquantified 
benefits from the reduction in CWP provided by the final rule. Within 
the avoided silicosis and NMRD deaths, however, MSHA includes benefits 
from avoided mortality due to progressive massive fibrosis (PMF)--
including mortality due to complicated CWP and complicated silicosis.
    Finally, MSHA also expects that the final rule's medical 
surveillance provisions will reduce mortality and morbidity from 
respirable crystalline silica exposure among MNM miners. The initial 
mandatory examination that assesses a new miner's baseline pulmonary 
status, coupled with periodic examinations, will assist in the early 
detection of respirable crystalline silica-related illnesses. Early 
detection of illness often leads to early intervention and treatment, 
which may slow disease progression and/or improve health outcomes. This 
may also result in less miner time-off and less miner turnover. 
However, MSHA lacks data to quantify these additional benefits.

[[Page 28387]]

    National Coalition of Black Lung and Respiratory Disease Clinics 
was concerned that the projected benefits of the proposed rule for coal 
miners were significantly lower than the projected benefits for MNM 
miners and suggested that MSHA correct for this by including dust 
samples from coal mines taken prior to August 1, 2016 (Document ID 
1410). Similarly, the Appalachian Citizens' Law Center asserted that 
the benefits estimated in the PRA are low and urged MSHA to include a 
longer history of coal dust sampling data (Document ID 1445). MSHA 
believes that samples from before August 1, 2016, may not accurately 
reflect the current conditions in coal mines and therefore should not 
be used in analyzing the impact of this final rule. As discussed in 
Appendix A of the preamble, on August 1, 2016, Phase III of the 2014 
RCMD Standard went into effect, and this lowered the PEL for RCMD in 
coal mines. The controls put in place to achieve that new PEL impacted 
both RCMD with and without respirable crystalline silica dust in coal 
mines, and as such, these controls likely lowered concentrations of 
respirable crystalline silica. Using data from after the coal mine dust 
rule went into effect helps to ensure that benefits attributable to 
that rule are not attributed to this rule incorrectly. More details 
about the respirable crystalline silica sample dataset, including the 
time coverage and brief statistics, are described in ``Description of 
MSHA Respirable Crystalline Silica Samples'' (Appendix A of the 
preamble of Proposed Rule). In addition to the prior effects of the 
2014 RCMD Standard on respirable crystalline silica exposure in the 
coal sector, there will also be greater benefits to MNM miners owing to 
the medical surveillance requirements which are already existing for 
coal miners. However, these benefits are unquantified in the FRA and 
FRIA analyses and therefore, do not specifically contribute to the 
discrepancy mentioned by these commenters.
    Further, the benefits quantified here may underestimate the true 
benefits to coal miners. MSHA believes this final rule will likely 
lower not only respirable crystalline silica concentrations, but also 
RCMD levels. As a result, MSHA believes this final rule will provide 
additional reductions in CWP, NMRD, and PMF beyond those conferred by 
the 2014 RCMD Standard. In the 2014 Coal Dust Rule, NIOSH emphasized 
the important role respirable crystalline silica plays in causing these 
diseases, stating that, ``in concentrating on this particular exposure-
response relationship with coal mine dust, we must not forget that 
[coal] miners today are being exposed to excess silica levels, 
particularly in thinner seam and small mines, and that this situation 
could well get worse as the thicker seams are mined out. Hence, since 
silica is more toxic than mixed coal dust, tomorrow's [coal] miners 
could well be at greater risk, despite a reduction in the mixed coal 
mine dust standard.'' While additional reductions in total RCMD would 
be expected due to this final rule, these reductions cannot be 
quantified as the reductions depend on the particular control measures 
that mine operators implement. Additionally, exposure-response models 
for respirable crystalline silica exposure and resultant CWP are not 
available. Thus, the benefits quantified in this FRIA may underestimate 
the true benefits to coal miners, as MSHA does not account for expected 
reductions in CWP or in other diseases due to reduced RCMD.

E. Benefit-Cost Analysis

    The net benefits of the final rule are the differences between the 
estimated benefits and costs. Table IX-26 shows estimated net benefits 
using alternative discount rates of 0, 3, and 7 percent. The choice of 
discount rate has an effect on annualized costs, benefits, and net 
benefits. While the net benefits of the final respirable crystalline 
silica rule vary depending on the choice of discount rate used to 
annualize costs and benefits, total benefits exceed total costs under 
all discount rate considered. MSHA's estimate of the net annualized 
benefits of the final rule, using a discount rate of 3 percent, is 
$156.6 million a year, with the majority ($143.9 million; 91.9 percent) 
attributable to the MNM sector.

[[Page 28388]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.183

F. Sensitivity Analysis on the Tenure of Miners

    As mentioned in Part E. Benefit-Cost Analysis, in performing the 
benefit analysis, MSHA assumed that all miners have a working tenure of 
45 years, from the start of age 21 to the end of age 65. MSHA also 
assumed that each miner's level of exposure remains the same in each 
day of each year. MSHA also performed a sensitivity analysis to see how 
benefits would differ under three scenarios with alternative tenures, 
though with all three sharing the same simplifying assumption that 
exposure remains constant for each miner across all of their working 
years. These alternative scenarios involved: (1) a tenure of 35 working 
years (rather than 45), between the ages of 26 and 60; (2) a tenure of 
25 working years, between the ages of 31 and 55; and a tenure of 15 
years, between the ages of 36 and 50. These age ranges were selected to 
maintain the same midpoint miner age of 43.
    Under the assumption that the same number of miners (257,383) are 
working at any given time the lower the tenure, the more turnover there 
would be among miners, the greater the number of new miners who would 
enter each year to replace those who are retiring or changing jobs. For 
example, when the scenario changes from a 45-year tenure (which was 
used in the benefit analysis) to a 15-year tenure, the analysis would 
require a single miner who would work for 45 years to be effectively 
replaced by three miners who would each be working for 15 years (one 
after another) during those same 45 years. This means that, in these 
lower-tenure scenarios, each miner would have accumulated less exposure 
by the time they retire, but there would be more miners retiring with 
that level of exposure.
    From analyzing the alternative scenarios with different tenures, 
using its risk model, MSHA found that lower tenures tended to result in 
more avoided cases of mortality. This is because, while the risk of 
mortality increases for any miner who works more years, at lower tenure 
rates, many more miners are exposed and are put at risk of dying from 
the disease. According to the models, the increased number of exposed 
miners, when tenure is short, leads to a greater increase in overall 
mortality than does the increased likelihood of mortality occurring for 
each miner, when the tenure is long. As a result, this sensitivity 
analysis found that the rule would have greater benefits, in terms of 
reducing mortality, under scenarios with shorter tenure than under the 
45-year tenure assumption used in the benefits analysis. The assumption 
of a 45-year tenure may be seen as effectively leading to an 
underestimate the benefits of the rule in terms of reduced mortality, 
relative to assumptions involving lower tenures.
    From the way the risk model is designed, however, the opposite 
effect was observed with regard to morbidity cases, where there were 
more cases of morbidity under longer tenure rates. Under longer tenure 
rates, there are estimated to be more cases of morbidity overall, and 
therefore the rule has a greater estimated effect on reducing cases of 
morbidity under the assumption of a 45-year tenure than under the 
alternative scenarios. Nevertheless, because the benefits of reduced 
mortality cases count much more than the benefits of reduced morbidity 
cases, it may be concluded that under the shorter tenures of the 
alternative scenarios, the benefits of the rule would be greater. In 
other words, if the tenures of miners are, in fact, shorter than 45 
years, the assumption of a 45-year tenure has the net effect of 
underestimating the benefits of the rule.

[[Page 28389]]

G. Regulatory Alternatives

    In developing the final rule, MSHA considered three regulatory 
alternatives. The first two alternatives contain less stringent 
exposure monitoring provisions than the final rule, which comparatively 
presents a comprehensive approach for lowering miners' exposure to 
respirable crystalline silica and improving respiratory protection for 
all airborne contaminants. The first alternative includes no change to 
the final rule's PEL and action level, whereas the second alternative 
includes a more stringent PEL. The second alternative combines less 
stringent exposure monitoring with a more stringent PEL. The third 
alternative examines a different methodology for calculating miners' 
exposures and assessing compliance. MSHA discusses the regulatory 
options in the sections below.
1. Regulatory Alternative 1: Changes in Sampling and Evaluation 
Requirements
    Under this alternative, the new PEL would remain unchanged at 50 
[mu]g/m\3\ and the action level would remain unchanged at 25 [mu]g/
m\3\. Further, mine operators would conduct: (1) first-time and second-
time sampling for miners who may be exposed to respirable crystalline 
silica at or above the action level of 25 [mu]g/m\3\, (2) above-action-
level sampling twice per year for miners who are at or above the action 
level of 25 [mu]g/m\3\ but at or below the PEL of 50 [mu]g/m\3\, and 
(3) annual evaluation of changing mining processes or conditions that 
would reasonably be expected to result in new or increased exposures.
    Mine operators would still be required to conduct sampling under 
this Regulatory Alternative and would thus incur compliance costs. 
However, exposure monitoring requirements under this alternative are 
less stringent than the requirements under the final rule because the 
frequency of above-action-level sampling and periodic evaluations are 
set at half the frequency of the final exposure monitoring 
requirements. Therefore, the cost of compliance would be lower under 
this alternative. MSHA estimates that annualized exposure monitoring 
costs would total $29.3 million for this alternative (at a 3 percent 
discount rate), compared to $53.2 million for the final exposure 
monitoring requirements, resulting in an estimated difference of $24.0 
million in compliance costs per year (Table IX-27).
    Although this alternative does not eliminate exposure monitoring, 
the requirements are minimal relative to the monitoring requirements 
under the final rule. However, MSHA believes it is necessary for mine 
operators to establish an initial baseline for any miner who may be 
reasonably expected to be exposed to respirable crystalline silica. In 
addition, above-action-level sampling helps mine operators correlate 
mine conditions to miner exposure levels and see exposure trends more 
rapidly than would result from semi-annual or annual sampling. This 
will enable mine operators to take necessary measures to ensure 
continued compliance with the new PEL. Further, more frequent 
monitoring will enable mine operators to ensure the adequacy of 
controls at their mines and better protect miners' health. These 
benefits cannot be quantified, but they are nevertheless material 
benefits that increase the likelihood of compliance.
[GRAPHIC] [TIFF OMITTED] TR18AP24.184

    MSHA also believes that requiring more frequent above-action-level 
sampling will provide mine operators with greater confidence that they 
are in compliance with the new PEL. Because of the variable nature of 
miner exposures to airborne concentrations of respirable crystalline 
silica, maintaining exposures below the action level

[[Page 28390]]

provides mine operators with reasonable assurance that miners would not 
be exposed to respirable crystalline silica at levels above the PEL on 
days when sampling is not conducted. MSHA believes that the benefits of 
the final sampling requirements justify the additional costs relative 
to Regulatory Alternative 1.
    Two mining trade associations, American Exploration and Mining 
Association and National Mining Association, expressed support for 
Regulatory Alternative #1 (Changes in Sampling and Evaluation 
Requirements) as a more appropriate approach than the one in the 
proposed rule, with one clarifying that its support for Regulatory 
Alternative #1 is only secondary to its primary recommendation that 
MSHA adopt OSHA's risk-based approach to sampling and evaluation 
requirements (Document ID 1424; 1428). Specifically, these commenters 
supported the Regulatory Alternative #1 requirement for baseline 
sampling for miners whose exposure is at or above the proposed action 
level of 25 [micro]g/m\3\ in lieu of the requirement for baseline 
sampling of each miner who is or may reasonably be expected to be 
exposed to respirable crystalline silica of any level. Further, these 
commenters supported the Regulatory Alternative #1 periodic sampling 
requirement of twice per year for miners between the action level and 
the PEL, which they said was more in line with established industrial 
hygiene guidelines and would allow mine operators to allocate 
industrial hygiene resources to those areas where they are better used, 
including areas where there is higher risk of exposure above the PEL. 
Finally, these commenters supported the Regulatory Alternative #1 
requirement for annual evaluation of mine processes or conditions, 
instead of the proposed rule's semi-annual review, stating that it 
would provide an equal amount of protection to miners (given that 
mining processes and conditions are relatively stable and non-
changing), while lowering operator compliance costs.
    MSHA believes it is necessary for mine operators to establish a 
solid baseline for any miner who is reasonably expected to be exposed 
to respirable crystalline silica. In addition, frequent, regular 
sampling and evaluation help mine operators correlate mine conditions 
to mine exposure levels and see exposure trends more rapidly than would 
result from semi-annual sampling and annual evaluation. This will 
enable mine operators to take measures necessary to ensure continued 
compliance with the PEL. Further, more frequent monitoring will enable 
mine operators to ensure the adequacy of controls at their miners and 
better protect miners' health. These benefits cannot be quantified, but 
they are nevertheless material benefits that increase the likelihood of 
compliance. MSHA believes that the benefits of the sampling and 
evaluation requirements justify the additional costs for the final rule 
relative to Regulatory Alternative 1. Therefore, MSHA did not select 
Regulatory Alternative 1.
2. Regulatory Alternative 2: Changes in Sampling and Evaluation 
Requirements and the PEL
    Under this Regulatory Alternative, the PEL would be set at 25 
[mu]g/m\3\, mine operators would install whatever controls were 
necessary to meet the PEL, and no action level would be designated. 
Further, under this Regulatory Alternative, mine operators would not be 
required to conduct first-time and second time sampling, above-action-
level sampling, and corrective actions sampling. However, mine 
operators would be required to perform periodic evaluations of changing 
conditions and to sample as frequently as necessary to determine the 
adequacy of controls. Additionally, mine operators would be required to 
perform post-evaluation sampling when the operators determine as a 
result of the periodic evaluation that miners may be exposed to 
respirable crystalline silica at or above the action level of 25 [mu]g/
m\3\.
    When estimating the cost of monitoring requirements under the final 
rule, MSHA assumed that the number of samples for post-evaluation 
sampling are relatively small (2.5 percent of miners) because mine 
operators are already collecting information which can be used for 
these purposes through the significant amount of above-action-level 
sampling. Since Regulatory Alternative 2 does not require above-action-
level sampling given the lack of an action level under this 
alternative, MSHA increases the share of samples after each evaluation 
to 10 percent of miners to ensure the monitoring requirements can be 
met.
    In addition, to meet the PEL of 25 [mu]g/m\3\, mine operators would 
incur greater engineering control costs as compared to the estimated 
cost of compliance for reaching a PEL of 50 [mu]g/m\3\. To estimate 
these additional engineering control costs, MSHA largely uses the same 
methodology as for mines affected at the new PEL of 50 [mu]g/m\3\.
a. Number of Mines Affected Under Regulatory Alternative 2
    MSHA first estimated the number of mines expected to incur the cost 
of implementing engineering controls to reach the more stringent PEL. 
After excluding mines that are affected at the new PEL of 50 [mu]g/m\3\ 
(to avoid double-counting), MSHA finds that 3,477 mines (2,991 MNM 
mines and 486 coal mines) operating in 2019 had at least one sample at 
or above 25 [mu]g/m\3\ but below 50 [mu]g/m\3\.\96\
---------------------------------------------------------------------------

    \96\ About 8,053 of mines active in 2019 either had neither a 
sample >25 [mu]g/m\3\ nor a sample in the last 5 years.
---------------------------------------------------------------------------

    In addition, MSHA also includes the 1,226 affected mines expected 
to incur costs to reach the new PEL of 50 [mu]g/m\3\. Based on its 
experience and knowledge, MSHA does not expect the mines that install 
engineering controls to meet the PEL of 50 [mu]g/m\3\ would also be 
able to comply with a PEL of 25 [mu]g/m\3\. For example, to comply with 
the PEL of 50 [mu]g/m\3\, a mine might need to add the engineering 
controls necessary to achieve an additional 10 air changes per hour 
over that achieved by existing controls, which are included in the 
costs presented in Table IX-21. However, such a mine facility would 
then need to add an additional 10 air changes per hour to meet the more 
stringent PEL of 25 [mu]g/m\3\, which is not included in the costs 
presented in Table IX-21. Thus, MSHA expects that the 1,226 affected 
mines will incur additional costs to meet the PEL of 25 [mu]g/m\3\ 
specified under this alternative.
    MSHA estimates a total of 4,703 mines will incur costs to purchase, 
install, and operate engineering controls to meet the more stringent 
PEL of 25 [mu]g/m\3\ under this alternative. MNM mines account for 
4,087 (87 percent) and coal accounts for the remaining 616 mines (13 
percent).
b. Estimated Engineering Control Costs Under Regulatory Alternative 2
    MSHA identified potential engineering controls that would enable 
mines with respirable crystalline silica dust exposures at or above 25 
[mu]g/m\3\ but below 50 [mu]g/m\3\ categories to meet the more 
stringent PEL of 25 [mu]g/m\3\ for this alternative. While MSHA assumed 
that mine operators will base such decisions on site-specific 
conditions such as mine layout and existing infrastructure, MSHA cannot 
make further assumptions about the specific controls that might be 
adopted and instead assumed the expected value of purchased 
technologies should equal the simple average of the technologies listed 
in each control category.
    Where more precise information is unavailable, MSHA assumed 
operating and maintenance (O&M) costs to be 35 percent of initial 
capital expenditure

[[Page 28391]]

and installation cost to be equal to the initial capital expenditure 
(Table IX-28). MSHA also assumed the larger capital expenditure 
controls will have a 30-year service life.
[GRAPHIC] [TIFF OMITTED] TR18AP24.185

    However, the difficulty of meeting a PEL of 25 [mu]g/m\3\ is such 
that MSHA's experience suggests a single control from Table IX-29 would 
not be sufficient. For example, respirable crystalline silica dust 
exposure at such a stringent limit is likely to occur in more than one 
area of the mine; in addition to increasing ventilation to a crusher/
grinder, enclosing and ventilating the belt conveyor would likely be 
necessary to reduce concentrations below a PEL of 25 [mu]g/m\3\. 
Similarly, increasing facility ventilation from 20 to 30 air changes 
per hour may not be adequate to meet the PEL. Rather, 40 air changes 
per might be necessary. Therefore, MSHA assumes mine operators will 
purchase and install at least two of the engineering controls listed in 
Table IX-28 under this Regulatory Alternative. This assumption was made 
to err on the side of overestimation.
    Table IX-29 presents the annualized engineering control costs per 
mine and total annualized engineering control costs by mine sector. At 
a 3 percent discount rate, the annualized engineering control costs are 
about $98,124 per mine, resulting in an additional cost of $461.5 
million if the PEL were set at 25 [mu]g/m\3\ instead of 50 [mu]g/m\3\.
[GRAPHIC] [TIFF OMITTED] TR18AP24.186


[[Page 28392]]


    Table IX-30 summarizes the estimated annualized cost of this 
Regulatory Alternative under consideration. At a 3 percent discount 
rate, exposure monitoring costs less than it does for the final rule. 
However, this lower monitoring cost is more than offset by the 
increased control costs necessitated by the requirement that mines 
maintain respirable crystalline silica exposure levels below 25 [mu]g/
m\3\. At an estimated annualized cost of $520.7 million, this 
alternative would cost nearly six times more than the final 
requirements.
[GRAPHIC] [TIFF OMITTED] TR18AP24.187

c. Avoided Mortality and Morbidity Under Regulatory Alternative 2
    Regulatory Alternative 2 increases miner protection by establishing 
the PEL at 25 [mu]g/m\3\, resulting in measurable increases in avoided 
mortality cases and other health benefits. Table IX-31 presents the 
avoided morbidity and mortality cases over the 60-year regulatory 
analysis time horizon under this alternative. Under this alternative, 
1,271 mortality cases are expected to be avoided, which is 2.4 times 
higher than the 531 mortality cases expected to be avoided under the 
new PEL (50 [mu]g/m\3\). Additionally, 2,521 morbidity cases are 
expected to be avoided under this alternative, which is 1.4 times 
higher than the 1,836 morbidity cases expected to be avoided under the 
new PEL (50 [mu]g/m\3\).

[[Page 28393]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.188

d. Monetized Benefits Under Regulatory Alternative 2
    Table IX-32 presents the monetized benefits associated with this 
avoided morbidity and mortality. The expected total benefits, 
discounted at 3 percent, are $516.3 million, which is more than twice 
the expected total benefits of $246.9 million under the new PEL (50 
[mu]g/m\3\).
    Under this Regulatory Alternative, these benefits are made up of 
$369.0 million due to avoided mortality, $47.3 million due to avoided 
morbidity preceding mortality, and $100.0 million due to avoided 
morbidity not preceding mortality. However, when compared to the 
annualized costs of $520.7 million (3 percent) and $662.2 million (7 
percent) for the Part 60 requirements, the net benefits of this 
alternative are negative at a 3 percent and 7 percent discount rate.

[[Page 28394]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.189

    A professional association, American Industrial Hygiene 
Association, expressed support for Regulatory Alternative 2 (Changes in 
Sampling and Evaluation Requirements and the Proposed PEL) (Document ID 
1351). However, the commenter recommended that mine operators be 
required to (1) conduct baseline sampling and periodic sampling, (2) 
conduct semi-annual or more frequent evaluations of changing 
conditions, and (3) sample as frequently as necessary to determine the 
adequacy of controls. In addition, the commenter stated that, under 
this alternative, mine operators should be required to perform post-
evaluation sampling when the operators determine from the semi-annual 
evaluation that miners are exposed at the 95-percent confidence level 
to respirable crystalline silica above the PEL of 50 [mu]g/m\3\, 
referencing a NIOSH Occupational Sampling Strategy Manual.
e. Net Benefits Under Regulatory Alternative 2
    Although the benefits associated with this avoided morbidity and 
mortality under Regulatory Alternative 2 (Table IX-31 and Table IX-32) 
are greater than those for the final rule, the net benefits of this 
alternative are negative at both a 3 percent and 7 percent real 
discount rate owing to the much higher compliance costs for this 
alternative as compared to those for the final rule (Table IX-31). 
Further, MSHA determines that meeting a PEL of 25 [mu]g/m\3\ is not 
achievable for all mines and therefore, Regulatory Alternative 2 is not 
chosen.
3. Regulatory Alternative 3: Changes in the Calculation of Exposure 
Concentrations
    Regulatory Alternative 3 calculates exposure concentrations as an 
entire-shift time-weighted average, called a ``full shift TWA''. Under 
this Regulatory Alternative, a different methodology is used for 
calculating exposures and assessing compliance. Elsewhere in the final 
rule, the costs and benefits are based on calculating exposure for a 
full shift, calculated as an 8-hour TWA. In this Regulatory 
Alternative, MSHA calculates exposure as a full shift TWA and re-
analyzes the costs and benefits of the rule. No other changes, such as 
changes to the rule requirements, are included under this Regulatory 
Alternative.
a. Number of Mines Affected Under Regulatory Alternative 3
    MSHA expects a change in the number of affected mines. MSHA has 
estimated the number of mines expected to incur costs when baseline 
exposure concentrations are re-calculated as full shift TWAs. Based on 
the use of a full shift TWA, MSHA finds that 1,053 mines operating in 
2019 would incur costs to purchase, install, and operate exposure 
controls under the final rule. Of this total, 955 are MNM mines and 98 
are coal mines. This total is 173 fewer mines than what would incur new 
compliance costs under an 8-hour TWA (1,226 affected mines).
b. Estimated Costs Under Regulatory Alternative 3
    Aside from the change to the calculation of exposure concentrations 
and the number of affected mines at those concentrations, MSHA does not 
make any additional changes in assumptions or calculations under this 
Regulatory Alternative. Therefore, the cost estimates of this 
Regulatory Alternative are calculated using the same methodology as 
described in Section 4 of the FRIA. The changes in cost estimates are 
completely attributable to changes in the estimated baseline exposure 
conditions and the total number of affected mines, as described in 
Section 7.3.1 of the FRIA.
    Table IX-33 below presents the estimated annualized compliance 
costs of part 60 if exposure concentrations were calculated using a 
full shift TWA instead of a full shift, 8-hour TWA.

[[Page 28395]]

Total part 60 annualized compliance costs are estimated at $86.4 
million (at a 3 percent discount rate), with 92.3 percent of costs 
attributable to MNM mines and 7.7 percent attributable to coal mines. 
This is $2.7 million (3.0 percent) less than the total part 60 
annualized compliance costs when using an 8-hour TWA ($89.1 million). 
The difference is explained by the decreased number of mines and miners 
who are affected by the rule under this Regulatory Alternative as 
compared to the main analysis.
[GRAPHIC] [TIFF OMITTED] TR18AP24.190

c. Avoided Mortality and Morbidity Under Regulatory Alternative 3
    While the compliance costs decrease when a full shift TWA is used, 
the estimated benefits of the rule are also expected to decrease. When 
miners work shifts that are longer than 8 hours (which commonly occurs, 
as seen both in the exposure data and in the employment data), the full 
shift, 8-hour TWA will result in a higher calculated exposure level 
than the full shift TWA.
    Table IX-34 presents the estimated number of avoided deaths and 
illnesses during the 60 years following the start of implementation of 
the new rule, under the Regulatory Alternative. The total number of 
avoided morbidity cases over the 60-year analysis period is 1,500, 
which is 18 percent lower under the Regulatory Alternative than the 
estimate of 1,836 avoided morbidity cases in the main analysis (see 
Table IX-24). The total number of avoided mortality cases over the 60-
year analysis period is 434, which is 18 percent lower under the 
Regulatory Alternative than the estimate of 531 avoided mortality cases 
in the main analysis (see Table IX-24).

[[Page 28396]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.191

d. Monetized Benefits Under Regulatory Alternative 3
    Table IX-35 presents the annualized benefits of the final rule 
under this Regulatory Alternative. The undiscounted annualized benefits 
under the Regulatory Alternative are estimated at $312.8 million, with 
$291.5 million attributable to MNM mines and $21.3 million attributable 
to coal mines. The discounted annualized benefits under the Regulatory 
Alternative are estimated at $201.9 million at a 3 percent discount 
rate and $107.9 million at a 7 percent discount rate. At a 3 percent 
discount rate, the annualized benefits are $45.0 million (18 percent) 
less under the Regulatory Alternative than when using an 8-hour TWA 
($246.9 million). The annualized benefits under the Regulatory 
Alternative are also 18 percent lower both at the 0 percent discount 
and 7 percent discount rates.
BILLING CODE 4520-43-P

[[Page 28397]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.192

BILLING CODE 4520-43-C
e. Net Benefits Under Regulatory Alternative 3
    The net annualized benefits under the Regulatory Alternative are 
$226.5 million (undiscounted), $114.3 million (3 percent discount 
rate), and $18.6 million (7 percent discount rate). The net benefits 
under the Regulatory Alternative are lower than those in the main 
analysis by 23 percent (0 percent discount rate), 27 percent (3 percent 
discount rate), and 53 percent (7 percent discount rate).\97\
---------------------------------------------------------------------------

    \97\ There are limitations in how the risk calculations can be 
performed because of limitations in the underlying exposure-response 
models from the literature. The exposure-response models were not 
designed to detect the impact of longer work shifts, nor were they 
based on longitudinal data that could track individuals' work shifts 
over their careers. These calculations presented in this Alternative 
analysis provide new estimates of avoided cases when calculating 
exposure as a full shift TWA and when accounting for the fact that 
fewer samples would meet the threshold of the new PEL or the new 
action level under a full shift TWA.
---------------------------------------------------------------------------

    MSHA received comments both in agreement with the Agency's proposed 
``full-shift, 8-hour TWA'' calculation method and against it. 
Commenters in favor stated that the proposed calculation method of 
collecting a sample for a full-shift and calculating the exposure level 
over an 8-hour period (i.e., normalizing a longer work shift to an 8-
hour shift) capture the total cumulative exposure to silica dust 
properly. Those against the proposal preferred the use of the entire 
duration of the miner's extended work shift without any adjustment, and 
stated that normalizing the extended shift sampling result to an 8-hour 
period inaccurately skews the results. For more details on the comments 
received, please see section VIII.B.3 of this preamble.
    The Agency does not choose Regulatory Alternative 3, that uses full 
shift TWA as an alternate calculation of exposure concentration. 
Regulatory Alternative 3 yields much smaller net benefits than the 
final rule. Importantly, Regulatory Alternative 3 would provide miners 
less health protection. Cumulative exposure to respirable crystalline 
silica is an important risk factor in the development of silica-related 
disease, as discussed in the standalone FRA document and section 
VIII.B.3.c of this preamble. However, the full shift TWA methodology 
does not account for the increased health risks associated with the 
higher cumulative exposures that can occur during longer work shifts. 
The full shift TWA calculation does not differentiate between the 
impacts of working 8-hour shifts and working extended shifts. 
Regulatory Alternative 3 would provide less protection for miners 
working longer shifts.

[[Page 28398]]

X. Final Regulatory Flexibility Analysis

A. The Regulatory Flexibility Act

    The Regulatory Flexibility Act of 1980 as amended by the Small 
Business Regulatory Enforcement Fairness Act of 1996, hereafter jointly 
referred to as the RFA, requires that an agency consider the economic 
impact that a final rulemaking will have on small entities. The RFA 
provides that, ``[w]hen an agency promulgates a final rule under 
section 553 of this title, after being required by that section or any 
other law to publish a general notice of proposed rulemaking . . . the 
agency shall prepare a final regulatory flexibility analysis.'' 5 
U.S.C. 604(a). However, under section 605(b), in lieu of an initial 
regulatory flexibility analysis (IRFA) or final regulatory flexibility 
analysis (FRFA), the head of an agency may certify that the final rule 
``will not, if promulgated, have a significant economic impact on a 
substantial number of small entities.'' 5 U.S.C. 605(b). That 
certification must be supported by a factual basis.
    As part of its notice of proposed rulemaking, MSHA prepared an IRFA 
that analyzed the potential impact of the proposed rule on small 
entities. See 5 U.S.C. 603(a). After considering public comments on the 
IRFA, MSHA believes that the final rule will not have a significant 
economic impact on a substantial number of small entities. However, in 
the furtherance of good governance principles and consistent with 
guidance from the Small Business Administration (SBA), the Agency has 
prepared a FRFA. Under section 604(a), the FRFA analysis must contain:
    (1) a statement of the need for, and objectives of, the rule;
    (2) a statement of the significant issues raised by the public 
comments in response to the initial regulatory flexibility analysis, a 
statement of the assessment of the agency of such issues, and a 
statement of any changes made in the proposed rule as a result of such 
comments;
    (3) the response of the agency to any comments filed by the Chief 
Counsel for Advocacy of the Small Business Administration in response 
to the proposed rule, and a detailed statement of any change made to 
the proposed rule in the final rule as a result of the comments;
    (4) a description of and an estimate of the number of small 
entities to which the rule will apply or an explanation of why no such 
estimate is available;
    (5) a description of the projected reporting, recordkeeping and 
other compliance requirements of the rule, including an estimate of the 
classes of small entities which will be subject to the requirement and 
the type of professional skills necessary for preparation of the report 
or record; and
    (6) a description of the steps the agency has taken to minimize the 
significant economic impact on small entities consistent with the 
stated objectives of applicable statutes, including a statement of the 
factual, policy, and legal reasons for selecting the alternative 
adopted in the final rule and why each one of the other significant 
alternatives to the rule considered by the agency which affect the 
impact on small entities was rejected; and for a covered agency, as 
defined in section 609(d)(2), a description of the steps the agency has 
taken to minimize any additional cost of credit for small entities. 5 
U.S.C. 604(a).
    While a full understanding of MSHA's analysis and conclusions with 
respect to costs and economic impacts on small entities requires a 
reading of the standalone FRIA document, this FRFA summarizes the key 
aspects of MSHA's analysis as they affect small entities.

B. Initial Assessment

    As part of the proposed rule, MSHA published an IRFA. MSHA's 
proposed rule would affect MNM and coal mining operations. The IRFA 
identified which mine controllers were small entities, estimated the 
direct compliance costs for those small entities, and compared the 
compliance costs to the revenues of the small entities. Results from 
the IRFA are summarized below.
1. Definition of Small Entities
    In its IRFA analysis, MSHA relied on the Small Business 
Administration (SBA)'s 2017 Table of Size Standards to define the size 
thresholds for small entities. MSHA identified small-entity controllers 
in each North American Industry Classification System (NAICS) code, 
after determining that a ``controller,'' the entity that owns and 
controls one or more mines, is the appropriate unit of the IRFA 
analysis, based on SBA guidance.\98\ (SBA, 2017).\99\ The IRFA detailed 
how SBA's size standards vary by North American Industry Classification 
System (NAICS) code, which NAICS codes were used in the IRFA, and which 
controllers were small entities according to these standards.
---------------------------------------------------------------------------

    \98\ Small Business Administration, Office of Advocacy, How to 
Comply with the Regulatory Flexibility Act, August 2017.
    \99\ A controller is a parent company owning or controlling one 
or more mines, whereas a mine is an establishment of a parent 
company. Small entities subject to the requirements of the 
Regulatory Flexibility Act are entities that are parent companies 
only and not establishments. See Small Business Administration, 
Office of Advocacy, How to Comply with the Regulatory Flexibility 
Act, August 2017. Sec. 3(d) of the Mine Act defines ``operator'' as 
``any owner, lessee, or other person who operates, controls, or 
supervises a coal or other mine.'' 30 U.S.C. 802(d). Under 30 CFR 
part 41, an operator must file a legal identity report with MSHA, 
and with this report, MSHA identifies a controller for each mine. 30 
U.S.C. 819(d) (each operator shall file the name and address of the 
``person who controls or operates the mine''). In the FRFA, 
consistent with SBA guidance and the Mine Act, MSHA determines 
whether the controller is a small entity.
---------------------------------------------------------------------------

2. Number of Affected Small Entities
    MSHA estimated that in 2021, there were a total of 11,791 mines and 
a total of 5,879 controllers. Of the controllers, 5,007 were small-
entity controllers; these small-entity controllers owned 8,240 mines. 
Many controllers owned one or two mines, while some controllers owned 
hundreds of mines nationwide (or worldwide).
3. Results of the Initial Regulatory Flexibility Analysis
    MSHA estimated the regulatory compliance costs and revenues for 
each of the 5,007 small-entity controllers identified in 2021. In 
estimating compliance costs for small-entity controllers, MSHA factored 
in the types of commodities that controllers produced and their 
employment size, which were gathered from the MSHA Standardized 
Information System (MSIS). MSHA estimated the revenues of the small-
entity controllers based on data from the Statistics of U.S. Businesses 
published by the U.S. Census Bureau, using NAICS codes and each 
controller's employment size.\100\ MSHA then calculated the compliance 
costs as a proportion of revenues and used that as an indicator of the 
relative burden of the compliance costs for small-entity controllers.
---------------------------------------------------------------------------

    \100\ U.S. Census Bureau, ``Statistics of U.S. Businesses,'' 
released May 2021. https://www.census.gov/data/tables/2017/econ/susb/2017-susb-annual.html (last accessed Jan. 10, 2024). Data in 
the report were in reference to the year 2017, which MSHA adjusted 
to 2021 dollars. Data on revenues are presented in the report under 
the equivalent term ``receipts.'' MSHA converted the 2017 revenues 
to 2021 dollars using the GDP Implicit Price Deflator published by 
the Bureau of Economic Analysis October 26, 2022, Table 1.1.9 
Implicit Price Deflators for Gross Domestic Product, Series A191RD. 
https://apps.bea.gov/histdata/fileStructDisplay.cfm?HMI=7&DY=2022&DQ=Q3&DV=Advance&dNRD=October-28-2022 (last accessed Jan. 10, 2024). The index was 107.749 for 
2017 and 118.895 for 2021, creating an adjustment factor (from 2017 
to 2021 dollars) of 118.895/107.749 or 1.103.
---------------------------------------------------------------------------

    From these two sets of estimates, MSHA generated estimates of the 
ratios of regulatory compliance cost to revenue for each controller. 
Table X-1 shows the number of controllers, average annual regulatory 
costs, average annual

[[Page 28399]]

revenues, and average cost as a percent of revenue presented in the 
IFRA. As shown in Table X-1, for every $1 million in revenue earned by 
a small-entity controller, the average compliance cost was estimated to 
be $1,220.
[GRAPHIC] [TIFF OMITTED] TR18AP24.193

C. MSHA Compliance With RFA Requirements

1. Outreach and Small Business Advocacy Review
    On July 13, 2023, MSHA published its notice of proposed rulemaking 
in the Federal Register. The proposed rule was also posted on 
Regulations.gov and on MSHA's website to ensure that members of the 
public, including small businesses, had more than one way to access the 
proposal. Prior to publication, MSHA made an informal copy of the 
proposed rule available on the Agency's website to provide small 
businesses and other stakeholders with additional time to become 
familiar with the proposal. MSHA also reached out to mining labor and 
industry stakeholders, public interest groups, and trade associations, 
notifying them of the upcoming publication of the proposed rule. Some 
of these stakeholders represented small businesses.
    During the public comment period, MSHA held three public hearings 
(virtual and in-person)--in Arlington, Virginia (on August 3, 2023), 
Beckley, West Virginia (on August 10, 2023), and Denver, Colorado (on 
August 21, 2023)--to facilitate the participation of the public, small 
businesses and organizations that represent them, and all other 
stakeholders.
    On August 30, 2023, MSHA attended a Small Business Labor Safety 
Roundtable organized by the SBA's Office of Advocacy to discuss the 
proposal. The Roundtable was also attended by the small business 
community and representatives from industry and labor. MSHA provided 
education about the NPRM's content at this roundtable.\101\
---------------------------------------------------------------------------

    \101\ MSHA considered the testimonies from the public hearings 
and written comments submitted to the docket for its development of 
the final rule, but not the discussion at the Roundtable. For 
transparency, however, MSHA makes the materials presented at the 
Roundtable available in the docket at Regulations.gov.
---------------------------------------------------------------------------

2. Final Regulatory Flexibility Analysis
a. Objectives of, and Need for, the Final Rule
    Based on its review of the health effects literature, MSHA 
determined that occupational exposure to respirable crystalline silica 
causes silicosis and other diseases. In its FRA, MSHA also determined 
that, under existing standards, miners face a risk of material 
impairment of health or functional capacity from exposures to 
respirable crystalline silica.
    Following these determinations, MSHA is issuing a final rule to 
better protect miners against occupational exposure to respirable 
crystalline silica, a carcinogen, and to improve respiratory protection 
for airborne contaminants. The final rule will affect both MNM and coal 
mining operations.
    The final rule establishes, for mines of all sizes, a PEL of 50 
[micro]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA, 
and an action level of 25 [micro]g/m\3\ for a full-shift exposure, 
calculated as an 8-hour TWA. In addition to the PEL and

[[Page 28400]]

action level, the rule includes provisions for methods of compliance, 
exposure monitoring, corrective actions, respiratory protection, 
medical surveillance for MNM mines, and recordkeeping. MSHA also amends 
existing standards for other airborne contaminants to replace 
requirements for respiratory protection and incorporates by reference 
ASTM F3387-19 Standard Practice for Respiratory Protection to update 
existing respiratory protection standards. The final rule will 
significantly improve health protections for all miners over the course 
of their working lives.
b. The Agency's Response to Public Comments
    MSHA received written comments from trade associations representing 
small businesses or small mines (Document ID 1406; 1408; 1411; 1413; 
1415; 1422; 1424; 1427; 1430; 1435; 1436; 1441; 1448; 1453; 1456; 1300; 
1302; 1303; 1349; 1368; 1369; 1378; 1383; 1392; 1398). The Agency also 
received a letter from the Deputy Chief Counsel and Assistant Chief 
Counsel for Advocacy of the SBA requesting a 60-day extension of the 
public comment period to give small businesses more time to comment and 
provide small business representatives time to consult their membership 
about their operations and how the proposed rule would impact them.
    On August 14, 2023, MSHA published a notice in the Federal Register 
extending the comment period by changing the closing date from August 
28, 2023, to September 11, 2023 (88 FR 54961).
    Commenters raised concerns about MSHA's estimates of the proposed 
rule's costs and impacts. MNM operators, mining and industry trade 
associations, and a mining related business stated that MSHA had 
underestimated the costs of the proposal for small mines (Document ID 
1427; 1430; 1435; 1436 1448; 1456; 1392). Commenters, including mining 
related businesses, MNM operators, and mining trade associations, also 
stated that, for some mines, there would be high costs of initial 
compliance or high costs of annual compliance thereafter (Document ID 
1408; 1411; 1415; 1427; 1430; 1435; 1436; 1448; 1453; 1456; 1383; 
1392). Commenters including mining trade associations and MNM operators 
cited the cost of obtaining equipment and services needed to establish 
sampling and medical surveillance programs, as well as the cost of 
implementing engineering controls (Document ID 1408; 1411; 1415; 1427; 
1435; 1436; 1441; 1448; 1392). MNM operators, mining trade 
associations, and other mine organizations commented on the costs of 
lab fees, respirators, and travel to undergo medical examinations for 
medial surveillance (Document ID 1408; 1411; 1415; 1435; 1436; 1448; 
1453; 1378; 1392). Several MNM operators and a mining-related business 
stated that compliance with the proposal would substantially increase 
their water costs (Document ID 1411; 1415; 1427; 1435; 1436; 1392). 
Some commenters including a mining-related business, mining trade 
associations, MNM operators, and other mine industry organizations 
noted that the costs of compliance would be higher for small mines 
operating in remote locations (Document ID 1408; 1411; 1415; 1422; 
1424; 1453; 1378; 1392). A mining trade association and a mining-
related business stated that MSHA failed to consider that some small 
mines might go out of business due to being unable to afford to comply 
with the new rule, which would result in losses to local economies 
(Document ID 1429; 1368; 1392).
    Taking these comments into consideration, MSHA changed its 
compliance dates and other requirements, which resulted in revisions to 
some of previous cost estimates. MSHA's cost estimates are detailed in 
Section 4 of the standalone FRIA document. MSHA believes its cost 
estimates for sampling, exposure controls, laboratory fees, and medical 
surveillance are accurate for small-entity controllers. As explained in 
Section 8 of the standalone FRIA document, MSHA adjusted some 
compliance costs upwards in response to commenters; in particular, 
sampling and exposure control costs. MSHA incorporated these adjusted 
costs in the cost estimates for small entities. In the FRFA 
methodology, the compliance costs that were derived in the FRIA, per 
mine employee, were estimated for specific size categories of mines, 
and for the type of commodity produced in the mine.\102\ Based on these 
costs, and the number of employees at mines, MSHA estimated the 
average, expected compliance cost for each small-entity controller in 
2021. These are average costs, which will vary among small-entity 
controllers. However, overall, MSHA believes that these estimates 
support the conclusion that the compliance costs incurred by small-
entity controllers, on average, will be a small fraction of the revenue 
that small controllers earn from their operations. MSHA found that, 
among small-entity controllers, the compliance costs of the final rule 
represent, on average, about 0.318 percent of the revenues that small 
entities earn. MSHA concluded that these compliance costs are generally 
unlikely to have significantly negative economic impacts on small-
entity controllers or on local economies.
---------------------------------------------------------------------------

    \102\ These size categories were mines with 20 or fewer 
employees, 21-100 employees, 101-500 employees, and over 500 
employees.
---------------------------------------------------------------------------

    MSHA understands that some small-entity controllers might have high 
initial capital investments for the installation of new engineering 
controls. However, high initial capital expenses, in general, are not 
uncommon in mining operations, especially with regard to the purchase 
of major units of equipment for engineering controls. Because these new 
engineering controls will last for many years, their purchase is 
comparable to any other type of investment in physical capital, for 
mining operations, that will be either paid directly or financed 
through periodic payments. If they are paid directly, this would be a 
one-time payment to cover several years, resulting in a lower cost per 
year. If the payment is financed, the annual (or monthly) costs will be 
much lower as well. Because these costs, on an annual basis, as 
determined by the useful life of the engineering controls, will be much 
lower than the initial investment, and these annual costs will be a 
small fraction of the revenues earned in those years, MSHA believes 
these new engineering controls will not, on average, be significantly 
burdensome to small-entity controllers. Moreover, MSHA expects that 
many of the mines that implement new engineering controls will be able 
to discontinue sampling once exposure levels are reduced below the 
action level. Thus, even mines with higher initial expenditures are 
unlikely to also have high annual costs thereafter.
    MSHA acknowledges the concerns from small mine operators in rural 
and remote areas. Because of the nature of mining, many mine operators, 
including small-entity operators, operate in rural and remote areas. 
MSHA believes that this final rule will not present major logistical 
challenges for small mine operators. As MSHA has stated in Section 
VIII.A. General Issues, once the final rule is implemented, the Agency 
will provide compliance assistance, including training and best 
practice materials, to all mine operators, with an emphasis on small 
operators.
    A mining-related business noted that the IRFA included no estimates 
of indirect costs of the rule (Document ID 1392). Examples of such 
costs cited by the commenter included lost

[[Page 28401]]

production, the expenses of employees traveling to medical 
examinations, and impacts on local communities of reductions in 
charitable donations by operators.
    MSHA considered the comment that the rule might lead to lost 
production. MSHA is providing additional compliance time for mine 
operators, including small-entity controllers, to prepare for the final 
rule's requirements. The extended compliance period under the final 
rule (24 months after the publication date for MNM operators and 12 
months after the publication date for coal operators) provides 
additional time for mine operators to comply with the requirements, 
such as implementing engineering controls and finding appropriate 
resources (industrial hygienists, medical facilities, laboratories, 
sampling devices, etc.). This extended compliance period is intended to 
provide industry additional time for planning. For example, a MNM small 
entity mine operator could use the increased time to identify and 
implement engineering controls to reduce miners' exposures.
    As in the IRFA, the FRFA includes the travel expenses related to 
miners' time lost due to travelling to medical examinations and their 
transportation costs. Regarding the costs of travel time to medical 
examinations, MSHA believes its estimates of the average travel time 
spent to and from medical examinations and the related cost are 
reliable, though it should be recognized that these are averages and 
that travel times could be different for different mines.
    MSHA considered the comment that the rule could incur ``costs to 
communities'' by making it harder for mine operators to make charitable 
donations to those communities. MSHA has not included charitable 
donations from operators in its analysis, as charitable donations are 
voluntary. MSHA believes that the final rule will benefit communities 
because the health and safety of miners is greatly improved. In this 
regard, MSHA's final rule is expected to have a net beneficial effect 
on mining communities through the improved health of miners, which 
should reduce the need for charitable support. Details on the revised 
estimates are provided in Section X.D. Analysis of Small Business 
Impacts.
c. Description of the Number of Small Entities to Which the Final Rule 
Will Apply
    The final rule, like the proposed rule, will affect MNM and coal 
mining operations. As in its IRFA, MSHA considered a controller (parent 
company) that owns and operates one or more mines as the appropriate 
unit of this FRFA.
    To determine the number of small entities subject to the final 
rule, MSHA used SBA's 2023 Size Standards and other guidance from the 
Office of Advocacy such as how to determine if a government entity is a 
small entity, NAICS codes, and MSIS, which identifies mines and their 
numbers of employees working at mines.
    MSHA estimated that the number of small-entity controllers in 2021 
was 5,462 out of the total number of controllers (5,879). The 5,462 
small-entity controllers owned a total of 9,395 mines out of a total of 
12,529 mines owned by all controllers in 2021.\103\ The estimated 
number of small-entity controllers reflects an increase from 5,007 in 
the IRFA; this revision is due to the use of more current NAICS codes 
and more current SBA size standards. In addition, MSHA performed a more 
thorough analysis of potential enterprises that might be small but had 
not been estimated as small in the IFRA, such as small local 
governments that owned mines.
---------------------------------------------------------------------------

    \103\ The total number of mines (12,529) was updated in the FRFA 
based on additional analysis of the data.
---------------------------------------------------------------------------

    In analyzing controllers of mines, MSHA determined that mining 
operations subject to the final rule would fall under 19 NAICS codes. 
These industry categories and their accompanying six-digit NAICS codes 
are shown in Table X-2.\104\ MSHA then matched the NAICS codes with SBA 
small-entity size standards (based on the number of employees) to 
determine the number of small entities within each of the respective 
NAICS codes. MSHA then counted the number of small-entity controllers 
in each NAICS code, after determining which controllers owned which 
mines. Many controllers owned one or two mines, while some controllers 
owned hundreds of mines nationwide (or worldwide).105 106 
Table X-2 shows the count of all controllers and a count of small-
entity controllers in each NAICS code.
---------------------------------------------------------------------------

    \104\ The NAICS classifications used in this analysis are drawn 
from the latest version of the NAICS, which was effective in July 
2022. MSHA also used, in the analysis, an earlier version of NAICS 
categories that was effective in August 2019. MSHA had begun 
developing this analysis prior to the most current NAICS being 
effective. The older NAICS categories were still used in the part of 
the current analysis that estimated revenues. This is because the 
older categories were still needed in order for MSHA to cross-
tabulate (or crosswalk) its data on mines and controllers with 
Bureau of Census data on revenues by NAICS codes, where these Census 
data were organized by the same NAICS codes that were in the earlier 
version. No comparable revenue data, at this writing, had yet been 
revised to the most recent NAICS categories.
    \105\ The number of controllers and mines examined in this 
regulatory flexibility analysis are those specifically known to 
operate in 2021. The year 2021 is the most current year for which 
complete information was available. Such information about 
controllers as parent companies might include, for example, 
knowledge of whether the parent company is a large, multinational 
corporation, which would then have bearing on this regulatory 
flexibility analysis.
    \106\ Each mine is assigned only one NAICS code, reflecting the 
commodity that mine primarily produces. There are several cases in 
which more than one mine, owned by the same controller, have 
different NAICS codes, so that there are different NAICS codes for 
that one controller. In particular, of the 5,879 unique controllers 
identified in 2021, 608 of them each had mines that had different 
NAICS codes. In theory, this could present an ambiguity as to 
whether a controller with more than one NAICS code should be 
considered a small entity or not. Since NAICS codes vary by their 
small-entity thresholds, it is theoretically possible for a 
controller with more than one NAICS code to be a small entity 
according to the threshold for one of its NAICS codes, while not 
being a small entity according to a lower threshold for a different 
one of its NAICS codes. However, this situation was not found to 
occur for any of the mine controllers; all controllers that were 
determined to be small entities met the conditions for a small 
entity for each of their NAICS codes.
---------------------------------------------------------------------------

    Table X-2 presents the distribution of controllers by the one NAICS 
code for which they have the most employees, because some controllers 
are in more than one mining NAICS code.
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d. Reporting, Recordkeeping, and Other Compliance Requirements of the 
Final Rule
    The final rule not only establishes a PEL of 50 [micro]g/m\3\ and 
an action level of 25 [micro]g/m\3\ for respirable crystalline silica, 
but also includes provisions for methods of compliance, exposure 
monitoring, corrective actions, respiratory protection, and medical 
surveillance for MNM mines. Under the

[[Page 28403]]

final rule, mine operators are required to install, use, and maintain 
feasible engineering and administrative controls to keep each miner's 
exposure to respirable crystalline silica at or below the PEL. Mine 
operators are required to conduct sampling to assess miners' exposure 
to respirable crystalline silica. MNM operators are required to provide 
to all miners, including those who are new to the mining industry, 
periodic medical examinations performed by a PLHCP or specialist, at no 
cost to the miner. This requirement will ensure that MNM miners, like 
coal miners, are able to monitor their health and detect early signs of 
respiratory illness.
    In addition, the final rule creates new information collection 
requirements for mine operators. As described in greater detail in 
Section XI. Paperwork Reduction Act, operators are required to collect 
information involving: (1) exposure monitoring, (2) corrective actions, 
(3) respiratory protection, and (4) medical surveillance for MNM mines. 
(Table XI-1 in that section displays an estimate of the annualized 
information collection burden for the whole mining industry.)
e. Steps the Agency Has Taken To Minimize the Economic Impact on Small 
Entities
    In response to commenters who expressed concerns that the rule 
would lead to excessive demand and backlogs for sampling devices, 
industrial hygienists, labs, medical facilities, and NIOSH B Readers, 
MSHA adjusted the requirements in the final rule to provide additional 
time for small-entity controllers and other controllers, to prepare for 
compliance (24 months after publication of the final rule for MNM mines 
and 12 months after publication of the final rule for coal mines). MSHA 
is allowing this longer period for compliance because MNM operators, 
particularly small-entity controllers, may have less experience with 
sampling and may also need time to prepare for compliance with medical 
surveillance. For coal mines, the delayed compliance period gives 
operators sufficient time to plan and prepare for effective compliance 
with the new standards, while also ensuring that improved protections 
for miners from the hazards of respirable crystalline silica take 
effect as soon as practically possible. For additional details on the 
compliance dates, see Section VIII.B. Section-by-Section Analysis.
    MSHA will also provide compliance assistance to small-entity 
controllers and the mining community overall (including industry and 
labor) after publication of the final rule. This assistance will 
include guidance to assist mine operators in developing and 
implementing appropriate controls; outreach seminars (onsite and 
virtual, dates and locations will be posted on MSHA's website); dust 
control workshops at the National Mine Health and Safety Academy; 
support from the Educational Field and Small Mine Services staff; 
support from MSHA's Technical Support staff; silica training and best 
practice materials; and information on MSHA's enforcement efforts.
    MSHA examined three possible regulatory alternatives to this final 
rule and considered how they could affect small-entity controllers.
    Under Regulatory Alternative 1, the PEL would remain unchanged at 
50 [mu]g/m3 and the action level would remain unchanged at 25 [mu]g/m3. 
Further, mine operators would conduct: (1) first-time and second-time 
sampling for miners who may be exposed to respirable crystalline silica 
at or above the action level of 25 [mu]g/m3, (2) periodic sampling 
twice per year, and (3) an annual evaluation of changing mining 
processes or conditions that would reasonably be expected to result in 
new or increased respirable crystalline silica exposures. Under 
Regulatory Alternative 2, the PEL would be set at 25 [mu]g/m3; mine 
operators would install whatever controls are necessary to meet the 
PEL; and there would not be an action level. Further, mine operators 
would (1) not be required to conduct any sampling, but they would be 
required to (2) conduct periodic evaluations of changing conditions and 
(3) sample as frequently as necessary to determine the adequacy of 
controls.
    MSHA determined that the final rule will provide improved health 
protections for miners and will be achievable for all mines, including 
those that are owned and operated by small entities. MSHA has made the 
following determinations regarding the three alternatives considered:
     Regulatory Alternative 1, ``Changes in Sampling and 
Evaluation Requirements,'' would reduce overall costs to the mining 
industry by 26.9 percent for costs calculated at a 3 percent, and by 
26.4 percent for costs calculated at a 7 percent discount rate. These 
reduced costs would be proportionally experienced by small entities. 
The average costs as a percent of revenues for small entities would 
then be reduced (relative to the final rule) from 0.318 percent to 
0.232 percent based on a 3 percent discount rate, or to 0.234 percent 
based on a 7 percent discount rate.
     Regulatory Alternative 2, ``Changes in Sampling and 
Evaluation Requirements and the Proposed PEL,'' would increase overall 
costs to the mining industry by 484.8 percent for costs calculated at a 
3 percent discount rate, and by 627.1 percent for costs calculated at a 
7 percent discount rate. The average costs as a percent of revenues for 
small entities would then rise (relative to the final rule) from 0.318 
percent to 1.859 percent based on a 3 percent discount rate, and from 
0.318 percent to 2.31 percent based on a 7 percent discount rate.
     Regulatory Alternative 3, ``Changes in the Calculation of 
Exposure Concentrations,'' would change the methodology used for 
calculating exposures and assessing compliance to a full shift TWA, 
rather than a full-shift exposure, calculated as an 8-hour TWA. MSHA 
estimated that this alternative would decrease overall costs to the 
mining industry by 3.02 percent for costs calculated at a 3 percent 
discount rate, and by 3.41 percent for costs calculated at a 7 percent 
discount rate. The average costs as a percent of revenues for small 
entities would then fall from 0.318 percent to 0.308 percent based on a 
3 percent discount rate, and to 0.307 percent based on a 7 percent 
discount rate.
    Regulatory Alternative 1 would reduce the costs to small entities. 
However, the final rule will better protect miners from exposures to 
respirable crystalline silica. The final rule's exposure monitoring 
requirements are necessary to ensure that miners' health is adequately 
protected. MSHA determined that Regulatory Alternative 1 would not 
protect miners' health. The final rule's exposure monitoring 
requirements, including monitoring on a more frequent basis, will 
provide mine operators with greater confidence that they are in 
compliance with the final rule.
    Regulatory Alternative 2 would increase costs to small entities, 
making it an unsuitable choice for small mines. Additionally, this 
alternative would not be achievable for all mines because a PEL of 25 
[micro]g/m\3\, while technically feasible, is not practical for all 
mines.
    Regulatory Alternative 3 would reduce the costs to small entities. 
However, the final rule will better protect miners by using an exposure 
calculation method that recognizes the importance of cumulative 
exposure to respirable crystalline silica being an important risk 
factor in the development of silica-related disease. Regulatory 
Alternative 3 does not take into account the increased health risks 
associated

[[Page 28404]]

with the higher cumulative exposures that can occur during longer work 
shifts, and, therefore, is less protective for those miners who work 
longer shifts. A more in-depth discussion of the costs associated with 
each regulatory alternative is presented in Section IX. Summary of 
Final Regulatory Impact Analysis and Regulatory Alternatives and the 
standalone FRIA document.

D. Analysis of Small Business Impacts

1. Data and Methodology
a. Average Annual Cost per Small-Entity Controller
    Because the controllers vary in the scale of their mining 
operations, MSHA first estimated regulatory costs on a per-miner basis. 
MSHA anticipated that the regulatory costs per miner would vary across 
the six major commodity categories: coal, metal, nonmetal, stone, 
crushed limestone, and sand and gravel.\107\ The differences in 
regulatory costs by commodity reflect the varying levels of expected 
exposure to silica, as calculated in the FRIA.
---------------------------------------------------------------------------

    \107\ MSHA also anticipated that regulatory costs would vary by 
the size of the mine in terms of the number of miners, with the size 
categories of: (1) 20 or fewer miners, (2) 21-100 miners, (3) 101-
500 miners, and (4) over 500 miners.
---------------------------------------------------------------------------

    MSHA examined employment data for each controller. By combining 
this information with per-mine compliance cost information, MSHA 
derived estimates of the regulatory costs for each of the 5,462 small-
entity controllers identified in 2021. See the average annual 
regulatory cost per controller in Table X-3.
    The compliance burden on the controllers, large and small, consists 
primarily of the costs of additional dust control measures, exposure 
monitoring, medical surveillance for MNM mines, and other program 
activities needed to comply with the rule. For costs estimates by 
component, by commodity, and by mine size, please see Section 4 of the 
standalone FRIA document.
b. Average Annual Revenue per Small-Entity Controller
    MSHA estimated revenues for each small-entity controller. The 
Agency estimated revenues per employee, by mine, and by controller, 
using data published by the U.S. Bureau of Census in their report, 
``Statistics of U.S. Businesses'' (SUSB).\108\ The SUSB data provided 
revenue estimates for enterprises (mines) in each NAICS code and for 
each ``size category'' (based on number of employees) within each NAICS 
code.\109\
---------------------------------------------------------------------------

    \108\ U.S. Census Bureau, ``Statistics of U.S. Businesses,'' 
released May 2021. https://www.census.gov/data/tables/2017/econ/susb/2017-susb-annual.html (last accessed Jan. 10, 2024). Data in 
the report were in reference to the year 2017, which MSHA adjusted 
to 2021 dollars. Data on revenues are presented in the report under 
the equivalent term ``receipts.'' MSHA converted the 2017 revenues 
to 2022 dollars using Price Indexes for Gross Domestic Product, 
Bureau of Economic Analysis, Table 1.1.4. https://apps.bea.gov/iTable/?reqid=19&step=3&isuri=1&1910=x&0=-99&1921=survey&1903=4&1904=2009&1905=2018&1906=a&1911=0 (last 
accessed Jan. 10, 2024). The index was 100 for 2017 and 117 for 
2021, creating an adjustment factor (from 2017 to 2022 dollars) of 
1.118.
    \109\ In a small number of cases (in terms of NAICS codes and 
size categories) the SUSB data were incomplete. In these cases, MSHA 
imputed revenue/employee ratios based on closely related data for 
comparable NAICS-size categories. MSHA then used these imputed 
revenue/employee ratios to estimate the revenues of some small-
entity controllers, by the methodology just described.
---------------------------------------------------------------------------

    Some of the small-entity controllers have operations in non-mining 
industries. Non-mining revenues are not accounted for in this analysis, 
as the data was not available. If non-mining revenues were accounted 
for, the ratio of regulatory costs to revenues shown in the summary 
table would be even smaller.
    MSHA calculated the number of mining employees for each small-
entity controller, and for each NAICS category (for mining NAICS) 
within each controller's activities. MSHA then combined these data with 
SUSB data on revenues by NAICS category and size category to generate 
estimated revenues for each small-entity controller. See the estimated 
average annual revenue per controller in Table X-3.
c. Average of Cost as a Percent of Revenue (Among Small-Entity 
Controllers)
    MSHA estimated the average annual regulatory cost per small-entity 
controller, as well as the average annual revenue per small-entity 
controller. MSHA estimated, for each controller, the annual compliance 
cost of the final rule as a proportion of that controller's annual 
revenue.
2. Economic Analysis Results
    Based on the methodology described above, MSHA generated estimates 
of the ratios of regulatory compliance cost to revenue for each 
controller. Table X-3 shows the number of controllers, average annual 
regulatory costs, average annual revenues, and average cost as a 
percent of revenue.
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    MSHA estimated that the final rule would have an average cost, per 
small-entity controller, of $11,026 per year in 2022 dollars. The 
estimated costs for the final rule represent the costs necessary for 
small-entity mine operators to achieve full compliance with the final 
rule.\110\
---------------------------------------------------------------------------

    \110\ MSHA estimated the costs of the rule for small-entity 
controllers by summing the costs for each of these controller's 
mines. The estimated cost for each mine was based on the number of 
miners and the mine's industry category. A controller's estimated 
cost was the sum of costs for each of its mines. Similarly, the 
estimated revenues of a controller was the sum of the revenues of 
each of its mines.
---------------------------------------------------------------------------

    From the cost and revenue estimates described above, MSHA estimated 
the ratio of annual regulatory cost to annual revenue for each small-
entity controller. As shown in Table X-3, the average of these 
proportions (weighting controllers equally) was 0.318 percent. In other 
words, for every $1 million in revenue earned by a small-entity 
controller, the average compliance cost was estimated to be 
approximately $3,000. This compliance cost-to-revenue ratio is slightly 
lower for controllers with five or fewer employees (0.299), implying 
that the low compliance cost-to-revenue ratios are generally applicable 
for the smallest of the small-entity controllers. The low cost-to-
revenue ratio of these controllers with five or fewer employees is due 
largely to the estimated annual revenues of these controllers averaging 
above $1 million in 2022 dollars, in comparison to their estimated 
compliance costs averaging approximately $3,000 per year.
    MSHA believes that the Agency could certify the economic impact of 
this final rule on small entities, however, in the interest of public 
disclosure and transparency, the Agency prepared a full analysis to 
inform the public of its decision-making process.

XI. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3521) provides 
for the Federal Government's collection, use, and dissemination of 
information. The goals of the Paperwork Reduction Act include 
minimizing paperwork and reporting burdens and ensuring the maximum 
possible utility from the information that is collected under 5 CFR 
part 1320. The Paperwork Reduction Act requires Federal agencies to 
obtain approval from the Office of Management and Budget (OMB) before 
requesting or requiring ``a collection of information'' from the 
public.
    As part of the Paperwork Reduction Act process, agencies are 
generally required to provide a notice in the Federal Register 
concerning each proposed collection of information to solicit, among 
other things, comment on the necessity of the information collection 
and its estimated burden, as required in 44 U.S.C. 3506(c)(2)(A). To

[[Page 28406]]

comply with this requirement, MSHA published a notice of proposed 
collection of information in the Agency's notice of proposed rulemaking 
on July 13, 2023 (88 FR 44852). MSHA solicited comment on the proposed 
information collection requirements and provided an opportunity for 
comments to be sent directly to OMB. MSHA also prepared and submitted 
an information collection request (ICR) to OMB for the collection of 
information requirements identified in the proposal for OMB's review in 
accordance with 44 U.S.C. 3507(d).
    MSHA has made several additions and changes to the proposed rule 
and methodology that have paperwork burden implications. Key additions 
include the immediate reporting of samples over the PEL to MSHA, 
reporting chest X-ray classification results to NIOSH, as well as a 
written respiratory protection program consistent with the requirements 
of ASTM F3387-19. Key changes include certain compliance dates, 
sampling requirements, medical examination dates for current miners, as 
well as the frequency of periodic evaluations and post-evaluation 
recordkeeping. Each addition and change and reasons for each are 
discussed in detail in Section VIII.B. Section-by-Section Analysis. The 
Agency has also changed the compliance dates from the proposed rule to 
provide mine operators adequate preparation time to comply effectively 
with the final rule's requirements.

A. Responses to Comments

    MSHA sought comment on the utility of the recordkeeping 
requirements in part 60. MSHA received multiple comments on the 
proposed recordkeeping requirements, with several commenters supporting 
MSHA's proposed recordkeeping provisions or recommending that records 
have a longer retention period than proposed. None of the comments 
addressed the methodology, assumptions, or calculations made in the 
Paperwork Reduction Act portion of the proposal.
    This section presents a summary of the comments received and the 
Agency's responses. Section VIII.B.9. Section 60.16--Recordkeeping 
Requirements provides a more detailed summary of the comments related 
to recordkeeping and MSHA's responses.
    The NSSGA stated that MSHA should adopt the same rule as the 
Occupational Safety and Health Administration's (OSHA) 2016 Silica Rule 
since some companies have OSHA and MSHA regulated facilities (Document 
ID 1448). This commenter stated that MSHA's silica rule with different 
requirements than OSHA creates excessive, unnecessary paperwork for 
these companies.
    The Agency clarifies that the Mine Act gives MSHA jurisdiction over 
each MNM or coal mine and each operator of such mine. The mining 
industry is different from the industries that are subject to OSHA's 
standards. MSHA did consider and adopt, as appropriate, some of OSHA's 
regulatory approach to controlling workers' exposures to respirable 
crystalline silica in developing its final rule. This final rule will 
better protect miners against occupational exposure to respirable 
crystalline silica, a carcinogenic hazard, and improve respiratory 
protection for airborne contaminants miners encounter. Nonetheless, the 
Agency has developed the rule's paperwork requirements to minimize 
burden on mine operators.
    For records retained under proposed paragraphs 60.16(a)(1) through 
(3)--evaluation records, sampling records, and corrective action 
records, respectively--many commenters, including labor organizations, 
advocacy organizations, and a MNM mine operator, recommended that 
record retention periods should be extended beyond the proposed 
requirements, especially for MNM mines (Document ID 1416; 1417; 1425; 
1439; 1447; 1449). A miner health advocate recommended that sampling 
records under Sec.  60.16(a)(2) be preserved for as long as the mine is 
in operation instead of the 2-year proposed requirement (Document ID 
1372). Additionally, Appalachian Voices recommended that the records 
under Sec.  60.16(a)(2) should be retained for longer than the life of 
the mine operation (Document ID 1425).
    In response to comments requesting an increase in the record 
retention period, in the final rule, MSHA increases the record 
retention period for evaluation, sampling, and corrective actions 
records in paragraphs (a)(1) to (3) to at least 5 years. The 5-year 
record retention period for evaluation, sampling, and corrective 
actions records is consistent with the 5-year record retention period 
for operator samples collected while monitoring for airborne exposure 
to diesel particulate matter in underground metal and nonmetal mines 
(Sec.  57.5071(d)(2)) and other injury and illness reports required 
under section 50.40. MSHA concludes in this final rule that a 5-year 
retention period for the records retained under paragraphs Sec.  
60.16(a)(1) through (3) is effective in providing information for the 
protection of miners. This is because the evaluation, Sec.  
60.16(a)(1), and sampling, Sec.  60.16(a)(2), records can identify a 
change in operation that might lead to increased exposures to 
respirable crystalline silica. Similarly, the 5-year recordkeeping 
requirement for corrective action records under Sec.  60.16(a)(3) is 
intended to help the operator and MSHA identify the effectiveness of 
existing controls, or the need for maintenance or additional control 
measures. In MSHA's experience, recent records can more effectively 
assist MSHA and mine operators in achieving these goals. MSHA believes 
the 5-year retention period achieves the proper balance between the 
operator's burden to maintain records and the effective utility of 
older records to mine operators, miners, and MSHA.
    For records retained under proposed paragraphs Sec.  60.16(a)(4) 
and (5)--written determination and medical opinion records, 
respectively, received from a PLHCP or specialist--some commenters such 
as a medical professional organization, a public health advocacy 
organization, and labor unions also suggested an increased retention 
period to help miners diagnosed with silica-related health conditions 
request workers' compensation claims (Document ID 1416; 1425; 1373; 
1437; 1412; 1398; 1447). A labor union recommended that medical 
surveillance data collected by mine operators should be kept for the 
duration of a miner's employment plus 20 or 30 years and for the 
records to be provided to the miner upon termination of employment 
(Document ID 1398). MSHA concludes in this final rule that it is 
appropriate to retain determination and medical opinion records, which 
have very limited medical information only relevant to the miner's 
ability to wear a respirator, for the duration of the miner's 
employment plus 6 months because the miner may need to wear a 
respirator at some point without notice. The requirement to retain 
records for an additional 6 months beyond the miner's employment gives 
miners more time to request records once they terminate their 
employment at the mine.
    A commenter (NVMA) asked for clarification on the medical 
surveillance recordkeeping requirements, stating that the rule does not 
include provisions requiring tracking of miners' silica exposure 
throughout their careers and noting that miners often change companies 
over the course of their careers (Document ID 1441). MSHA clarifies 
that mine operators do not have access to a miner's medical information 
and, therefore, do not maintain a record of such information. Instead, 
the mine operator will retain a record of the date of the medical 
examination, a statement

[[Page 28407]]

that the examination has met the requirements of this section, and any 
recommended limitations on the miner's use of respirators. Each miner, 
or the miner's physician or other designee at the request of the miner, 
will have access to all medical examination results.
    Two commenters including a labor union also suggested that 
corrective action records and cumulative exposure records be submitted 
to MSHA, miner representatives, or miners (Document ID 1447; 1439). 
After considering the comments, MSHA determined that it is not 
necessary to change the requirement of providing all the listed records 
promptly upon request to miners, authorized representatives of miners, 
and authorized representatives of the Secretary of Labor. This is 
because the requirement to provide all the listed records promptly upon 
request ensures that miners and MSHA will have access to records as 
needed can facilitate enforcement and transparency. Because miners, 
miners' representatives, and MSHA can request the records at any time 
for their own recordkeeping purposes, MSHA does not believe it is 
necessary to have operators submit the records to miners and MSHA 
without request. However, in response to comments, the final rule 
requires mine operators to immediately report all exposures above the 
PEL from operator sampling to the MSHA District Manager or to any other 
MSHA office designated by the District Manager. This modification will 
allow the Agency to promptly address overexposures as appropriate. As 
discussed below, this change from the proposal presents a modest 
increase in the estimated paperwork burden.
    The final rule requires a new information collection as well as 
modifications to existing collections. As required by the Paperwork 
Reduction Act, the Department has submitted information collections, 
including a new information collection and revisions of two existing 
collections, to OMB for review to reflect new burdens and changes to 
existing burdens. Once OMB completes its review, the Agency will 
publish a notice on the new information collection under OMB Control 
Number 1219-0156. (The regulated community is not required to respond 
to any collection of information unless it displays a current, valid, 
OMB Control Number.)

B. New Information Collection Under Part 60, Respirable Crystalline 
Silica

    Under final part 60, certain new burdens apply to all mine 
operators, and other burdens apply to only some mine operators. Section 
60.16 lists all the recordkeeping requirements related to part 60. Each 
of the requirements are discussed below:
    Section 60.12 requires mine operators to make a record for each 
sampling and each periodic evaluation conducted pursuant to the 
section. The samplings identified in Sec.  60.12(a) include: sampling 
by the compliance date (Sec.  60.12(a)(1)), an additional sampling 
(Sec.  60.12(a)(2)), above-action-level-sampling (Sec.  60.12(a)(3)), 
corrective actions sampling (Sec.  60.12(b)), and post-evaluation 
sampling (Sec.  60.12(d)). The sampling record consists of the sampling 
date, the occupations sampled, and the concentrations of respirable 
crystalline silica and respirable dust, and the mine operator must also 
retain laboratory reports on sampling results under Sec.  60.12(g).
    In a change from the proposal, under final Sec.  60.12(c), the 
periodic evaluations must be conducted at least every 6 months or 
whenever there is a change in: production; processes; installation and 
maintenance of engineering controls; installation and maintenance of 
equipment; administrative controls; or geological conditions; mine 
operators shall evaluate whether the change may reasonably be expected 
to result in new or increased respirable crystalline silica exposures. 
The periodic evaluation record includes the evaluated change, the 
impact on respirable crystalline silica exposure, and the date of the 
evaluation under Sec.  60.12(c)(1). In addition, the mine operator is 
required to post the sampling and evaluation records and the laboratory 
report on the mine bulletin board and, if applicable, by electronic 
means, for 31 days, upon receipt under Sec.  60.12(c)(2).
    The mine operator must immediately report all exposures above the 
PEL to the MSHA District Manager or to any other MSHA office designated 
by the District Manager under Sec.  60.12(b). A corrective action must 
be taken immediately to lower the concentration of respirable 
crystalline silica to at or below the PEL, once a sample reporting 
exposure above the PEL is recorded. The corrective actions record must 
include the corrective actions taken, including any related respirator 
use by affected miners, and the dates of the corrective actions under 
Sec.  60.13(c). All records must be retained for at least 5 years from 
the date of each sampling, evaluation, or corrective action.
    Section 60.14(b) requires mine operators to temporarily transfer a 
miner either to work in a separate area of the same mine or to an 
occupation at the same mine where respiratory protection is not 
required if the miner has a written determination from the PLHCP that 
the miner is unable to wear a respirator. Section 60.16(a)(4) requires 
the written determination record to be retained for the duration of a 
miner's employment plus 6 months. In a change from the proposal, final 
Sec.  60.14(c)(2) requires mine operators to have a written respiratory 
protection program that meets the following requirements in accordance 
with ASTM F3387-19: program administration; written standard operating 
procedures; medical evaluation; respirator selection; training; fit 
testing; maintenance, inspection, and storage.
    Section 60.15 requires MNM mine operators to provide miners 
periodic medical examinations at no cost to the miner. Section 
60.15(d)(1) requires the mine operator to ensure that the results of 
medical examinations or tests are provided from the PLHCP or specialist 
to the miner within 30 days of the medical examination, and, at the 
request of the miner, to the miner's designated physician or another 
designee identified by the miner. Section 60.15(d)(2) requires MNM mine 
operators to ensure that, within 30 days of the medical examination, 
the PLHCP or specialist provides the results of chest X-ray 
classifications to the National Institute for Occupational Safety and 
Health (NIOSH), once NIOSH establishes a reporting system. Mine 
operators are required to obtain a written medical opinion from the 
PLHCP or specialist within 30 days of a miner's medical examination. 
The written medical opinion must contain only the date of the medical 
examination, a statement that the examination has met the requirements 
of the section, and any recommended limitations on the miner's use of 
respirators under Sec.  60.15(e). The written medical opinion record 
must be retained by MNM mine operators for the duration of a miner's 
employment plus 6 months under Sec.  60.15(f).

C. Existing Information Collections

    The final rule results in changes to two existing information 
collection packages: a non-substantive change to information collection 
package under OMB Control Number 1219-0011, Respirable Coal Mine Dust 
Sampling; and a substantive change to information collection package 
under OMB Control Number 1219-0048, Respirator Program Records. This is 
a change from the proposal, which only contained non-substantive 
changes to existing information collections.
    Non-substantive changes to OMB Control Number 1219-0011 involve 
references to respirable dust when

[[Page 28408]]

quartz is present in the respirable coal mine dust standard. OMB 
Control Number 1219-0011 involves records for quarterly sampling of 
respirable dust in coal mines. MSHA's standards require that coal mine 
operators sample respirable coal mine dust quarterly and submit these 
samples to MSHA for analysis to determine if the mine is complying with 
the respirable coal mine dust standards. The supporting statement 
references quartz and a reduced standard for respirable dust when 
quartz is present. Since the final rule eliminates the reduced standard 
and establishes a separate standard for respirable crystalline silica, 
MSHA will make a non-substantive change to the supporting statement by 
removing such references. However, there will be no changes from the 
proposal in paperwork burden and costs in this information collection 
because the change only contains non-substantive changes to existing 
information collections.
    OMB Control Number 1219-0048 involves recordkeeping requirements 
under 30 CFR parts 56 and 57 for MNM mines when respiratory protection 
is used. Under the final rule, MSHA updates the existing respiratory 
protection standard and requires a written respiratory protection 
program that meets the following requirements in accordance with ASTM 
F3387-19: program administration; written standard operating 
procedures; medical evaluation; respirator selection; training; fit 
testing; maintenance, inspection, and storage. This substantive change 
will result in an increase in the paperwork burden and costs associated 
with respiratory protection in the existing information collection.

D. Information Collection Requirements

1. New Information Collection 1219-0156
    Type of Review: New Collection.
    OMB Control Number: 1219-0156.
    Title: Respirable Crystalline Silica Standard.
    Description of the ICR: The final rule on respirable crystalline 
silica contains information collection requirements on sampling, 
periodic evaluations, medical examinations, and respirator protection 
practices. The collected information will assist miners and mine 
operators in tracking actual and potential miners' occupational 
exposure to respirable crystalline silica, and identifying possible 
actions taken to control such exposure.
    There are provisions of this rule that will take effect at 
different times after the date of publication of this rule, and there 
are information collection provisions that will have different 
respondents, responses, burden hours, and costs in each year. 
Therefore, this ICR estimates the first 3 years of compliance.
    There were changes in this ICR between the proposed and final rule 
based on changes in methodology and the rule text. Based on changes to 
Sec.  60.1 in the final rule, MNM mines are not expected to begin 
implementing the rule until year 2. This change decreases the 
recordkeeping burden for all cost items in the final rule. In the 
proposed rule, operators were allowed to use historical and objective 
data instead of a second-time sampling. In the final rule, every mine 
is required to conduct a first-time and second-time sampling, thereby 
increasing the related time burden. The methodology for calculating 
corrective actions samples and post-evaluation samples was also 
changed, leading to an increased time burden for both. Additionally, 
based on changes to Sec.  60.12(b) in the final rule, operators are now 
required to notify MSHA after every overexposure.
    The inclusion of ASTM F3387-19 costs in this ICR was a result of a 
change in the rule text between the proposed rule and final rule. In 
the proposed rule, operators could choose which ASTM F3387-19 elements 
to adopt. In the final rule, mine operators must have a written 
respiratory protection program that meets an explicit set of 
requirements in accordance with ASTM F3387-19. This change leads to a 
substantial increase in the recordkeeping burden for this ICR. Lastly, 
the addition of Sec.  60.15(d)(2) in the final rule, which requires the 
mine operator to ensure that a miner's PLHCP or specialist provides the 
results of chest X-ray classifications to the National Institute for 
Occupational Safety and Health (NIOSH), created a new recordkeeper 
cost.
Summary of the Collection of Information
    Highlighted below are the key assumptions, by provision, used in 
the burden estimates in Table XI-1:
a. Section 60.12--Exposure Monitoring
    ICR. Section 60.12 requires mine operators to make a record for 
each sampling, corrective actions sampling, periodic evaluation, and 
post-evaluation sampling. Per Sec.  60.1, the compliance date for MNM 
mines begins one year after the compliance date for coal mines.
    Number of respondents. For Sec.  60.12, the respondents consist of 
all active mines, because operators of active mines are assumed to 
perform sampling and conduct periodic evaluations. MSHA counts the 
number of active mines in 2019, defining an active mine as one that had 
at least 520 employment hours (equivalent to 1 person working full time 
for a quarter of a year) in at least one quarter of 2019. Using this 
definition, MSHA estimates that a total of 12,631 mines (11,525 MNM 
mines and 1,106 coal mines) will generate sampling and evaluation 
records.
    Annual number of responses. Annual responses are summed from 
several separate activities including: all types of sampling (e.g., the 
first-time/second-time sampling, above-action-level sampling, 
corrective actions sampling, and post-evaluation sampling), and 
periodic evaluations. The estimated average annual number of responses 
is 199,817, including 52,587 first-time and second-time samples (the 
first sample is taken by the compliance date or within 6 months after 
beginning operations and the second-time sample is taken within 3 
months after the first sample), 44,253 above-action-level samples, 
50,834 corrective action samples and MSHA notifications, 12,766 post-
evaluation samples, and 39,377 periodic evaluation recordings and 
postings. Details of each type of sampling and periodic evaluations are 
discussed below.
    First-time sampling and second-time sampling apply to every coal 
and MNM mine. However, a certain number of mines are predicted to be 
able to discontinue sampling if the results of these samples are below 
the action level. Furthermore, subsequent to Year 1 for Coal, and Year 
2 for MNM, all first-time and second-time sampling will only be 
performed by new mines. MSHA projects that about 2 percent of mines in 
any given year will be new entrants to the mining industry. MSHA 
assumes that all active coal mines (1,106 mines) will conduct first-
time and second-time sampling in year 1 of compliance (producing 29,796 
samples). In years 2 and 3, an estimated 22 new coal mines will conduct 
first-time and second-time sampling (producing 596 samples each year). 
Similarly, MSHA assumes that all 11,525 MNM mines will conduct first-
time and second-time sampling in year 2 of compliance (producing 
124,288 samples). In year 3, 231 new MNM mines will conduct first-time 
and second-time sampling (producing 2,486 samples). MSHA estimates that 
an annual average of 52,587 first-time and second-time samples will be 
collected in the first 3 years of compliance.
    The estimated number of above-action-level sampling is calculated 
based on the following factors: the number of miners with sampling 
results at or above the action level (25 [mu]g/m\3\) but at or below 
the permissible exposure

[[Page 28409]]

limit (PEL) (50 [mu]g/m\3\), the percent of miners needed for 
representative samples, and the number of quarters in a year that mines 
will be in operation. Estimation of above-action-level sampling does 
not include costs related to first-time sampling and second-time 
sampling. MSHA has revised its methodology from the proposal, 
increasing the number of corrective actions samples to account for some 
operators needing multiple corrective actions samples before obtaining 
a sample below the PEL. The estimated number of samples is based only 
on previous operator samples, not ones from MSHA inspectors. MSHA does 
not expect above-action-level sampling to begin until the second half 
of year 1 for coal mines. MSHA estimates there will be 5,423 above-
action-level coal samples in the second half of year 1. Due to the 
projected decrease in the share of samples over the action level for 
coal mine compliance due to more mines engaging in increased 
administrative controls and frequent maintenance and repair, the number 
of above-action-level coal samples is projected to decrease to 10,556 
in year 2 and 10,170 in year 3. A more detailed discussion is provided 
in Section 4.2 of the standalone FRIA document. MSHA expects above-
action-level sampling to begin in the second half of year 2 for MNM 
mines, resulting in the number of above-action-leveling samples 
increasing from 37,719 in the second half of year 2 to 68,892 in all of 
year 3. Consequently, MSHA estimates that an annual average of 44,253 
above-action-level samples will be collected from coal and MNM mines in 
the first 3 years of compliance.
    MSHA estimates that an annual average of 731 active mines (604 MNM 
and 127 coal) will carry out an annual average of 25,417 corrective 
actions (22,152 MNM and 3,265 coal) due to overexposure, and these 
mines will then conduct corrective actions sampling for each corrective 
action. Miner operators will have to immediately notify MSHA about each 
overexposure. MSHA estimates that an annual average of 25,417 
corrective action notifications will be sent to MSHA.
    Next, MSHA assumes that all 1,106 coal mines will record periodic 
evaluation results approximately 2.4 times, on average, per year, and 
then post those results on a mine bulletin board, or if applicable, by 
electronic means. In a change from the proposal, MSHA increased its 
estimate for the number of periodic evaluations from about 2 per year 
to about 2.4 per year, a 20 percent increase. This was done for two 
reasons. First, Sec.  60.12(c) now requires periodic evaluations at 
least every 6 months after commencing sampling or whenever there is a 
change in production; processes; installation or maintenance of 
engineering controls; installation or maintenance of equipment; 
administrative controls; or geological conditions. Second, MSHA now 
accounts for portable mines, which move frequently and are therefore 
more likely to experience one of the changes noted in Sec.  60.12(c). A 
more thorough explanation for this calculation can be found in Section 
4.2 of the standalone FRIA document.
    The number of records for periodic evaluation in coal mines is 
2,449 each year. All 11,525 MNM mines will record periodic evaluation 
results approximately 2.4 times, on average, a year, and then post 
those results on a mine bulletin board, or if applicable, by electronic 
means, starting in year 2. The number of records for periodic 
evaluation in MNM mines is 0 for year 1, and 25,859 for years 2 and 3. 
Mine operators will also post results of each periodic evaluation on 
mine bulletin boards, creating an annual average of 19,688 records 
(2,449 in year 1, 28,308 in year 2, and 28,308 in year 3). 
Additionally, MSHA estimates mines will conduct post-evaluation 
sampling as a result of their periodic evaluations, resulting in an 
annual average of 12,766 sampling records (8,376 for MNM mines and 
4,390 for coal mines). MSHA estimates an annual average of 39,377 
periodic evaluation recordings and postings and 12,766 post-evaluation 
samples.
    The assumption for calculating corrective actions samples and post-
evaluation samples was changed from the proposal. In the proposed rule, 
the number of corrective actions samples was combined with the number 
of post-evaluation samples and their sum was assumed to be equivalent 
to a constant 2.5 percent of all miners per periodic evaluation. In the 
final rule, the number of corrective actions samples is based on the 
projected share of samples over the PEL, increased by 25 percent to 
account for some operators needing multiple samples before obtaining a 
sample below the PEL, while the number of post-evaluation samples alone 
is now equivalent to 2.5 percent of miners per periodic evaluation. The 
change in methodology is intended to made estimates more consistent 
with existing sampling data. In year 1 for coal mines and year 2 for 
MNM mines, they will sample for only half a year. See Section 4.2 of 
the standalone FRIA document for more details.
    Estimated annual burden. The estimated average annual burden is 
41,781 hours, including 13,147 hours for first-time and second-time 
sampling, 11,063 hours for above-action-level sampling, 8,472 for 
corrective actions sampling, 5,907 hours for periodic evaluations 
recording and posting, and 3,192 hours for post-evaluation sampling.
    MSHA estimates that it takes 15 minutes to record the sampling 
results, 15 minutes to record the results of a periodic evaluation, 5 
minutes to notify MSHA after an overexposure, and 3 minutes to post 
each of the evaluation results on the mine bulletin board, and, if 
applicable, by electronic means.
b. Section 60.13--Corrective Actions
    ICR. Section 60.13 requires mine operators to make approved 
respirators available to affected miners and immediately take 
corrective actions to lower the concentration of respirable crystalline 
silica to at or below the PEL if any sampling indicates overexposure. 
Once corrective actions are taken, the mine operator is expected to 
make a record of corrective actions. As per Sec.  60.1, the compliance 
date for MNM mines begins one year after the compliance date for coal 
mines. Based on changes to MSHA's methodology, there is no longer a 
separate paperwork burden related to respirator records. In the 
proposal, MSHA estimated an annual average of 5,685 records of miners 
who are provided respirator until corrective actions are complete. In 
the final rule, MSHA does not treat the paperwork burden of respirator 
records as a separate cost. Instead, it is assumed to be part of the 
corrective action records. Hence, the paperwork burden of respirator 
records is not a separate cost.
    Number of respondents. For Sec.  60.13, only those mines with at 
least one miner exposure above the PEL are assumed to carry out the 
requirement. MSHA estimates that an annual average of 731 active mines 
(604 MNM mines and 127 coal mines) will require corrective actions, 
starting in the second half of year 1 for coal mines and second half of 
year 2 for MNM mines. This change from the proposed rule is based on 
MSHA's new methodology for calculating corrective actions samples, 
which required updating corrective actions calculations to be 
consistent with that methodology. In the proposal, corrective actions 
samples were combined with post-evaluation samples, accounting for 2.5 
percent of all miners per periodic evaluation. The number of 
respondents was assumed to be one-fourth of the number of responses for 
each full year of sampling. In the final rule, the overexposure rate is 
expected to decrease linearly in the first several

[[Page 28410]]

years after the start of implementation of the rule. As a result, the 
number of corrective actions respondents is assumed to start with the 
current number of operators with an overexposure in their last sampling 
event from an MSHA inspector (as of 2019 for MNM mines and 2021 for 
coal mines) and falls each year based on the decreasing overexposure 
rate in each year. Additionally, some operators are expected to need 
multiple corrective actions before they carry out a sample below the 
PEL, thereby increasing the number of corrective actions by 25 percent.
    Annual number of responses. The estimated average annual number of 
responses is 25,417 (22,152 MNM and 3,265 coal). MSHA assumes that each 
corrective actions sample, whose calculations are described above and 
in Section 4.2 of the standalone FRIA document, will be preceded by a 
corrective action, resulting in 25,417 corrective action records.
    Estimated annual burden. The estimated average annual burden is 
2,118 hours. MSHA estimates that on average it takes 5 minutes to 
record a corrective action and the date.
c. Section 60.14--Respiratory Protection
    ICR. Section 60.14(b) requires mine operators to temporarily 
transfer a miner when the miner has a written determination from the 
PLHCP that the miner is unable to wear a respirator. Section 60.14(a) 
requires the temporary use of respirators in MNM mines under conditions 
specified in Sec. Sec.  60.14(a)(1) and 60.14(a)(2). The written 
determination record must be retained for the duration of a miner's 
employment plus 6 months under Sec.  60.16(a)(4). Section 60.14(c)(2) 
requires mine operators to have a written respiratory protection 
program that meets the following requirements in accordance with ASTM 
F3387-19: program administration; written standard operating 
procedures; medical evaluation; respirator selection; training; fit 
testing; maintenance, inspection, and storage, which is incorporated by 
reference in the final rule. As per Sec.  60.1, the compliance date for 
MNM mines is one year after the compliance date for coal mines.
    Number of respondents. For Sec.  60.14(b), MSHA assumes that each 
mine taking a corrective action (an annual average of 604 MNM mines and 
127 coal mines) will have one miner unable to wear a respirator. MSHA 
estimates that an additional 10 percent of MNM mines, which temporarily 
use respirators, will also have one miner unable to wear a respirator 
in years 2 and 3 (an annual average of 769 mines). Consequently, MSHA 
estimates that an annual average of 1,500 (1,373 MNM and 127 coal) 
mines will have a miner unable to wear a respirator.
    This is a change from the proposal, where MSHA assumed that \1/3\ 
of mine operators affected by respiratory protection requirements would 
have their miners wear respiratory protection in year 1 and 10 percent 
of the same mine operators would have their miners wear respiratory 
protection in years 2 and 3. This change is a result of MSHA updating 
its methodology to be consistent with the final rule requirements.
    For the ASTM F3387-19 incorporation by reference under Sec.  
60.14(c)(2), MSHA assumes, to err on the side of overestimation, that a 
total of 3,411 mine respondents (2,305 MNM mines and 1,106 coal mines) 
would have respiratory protection programs. MSHA assumes that a half of 
the coal mines (553 mines) would write new standard operating 
procedures (SOPs) relating to the respiratory protection program and 
the remaining half (533 mines) would revise existing SOPs in year 1. 
New coal mines, estimated at 2 percent (22 mines), are assumed to write 
respiratory protection SOPs in years 2 and 3. Similarly, for MNM mines, 
MSHA assumes that: a half of them (1,153 mines) would write new SOPs 
relating to the respiratory protection program; the remaining half 
(1,152 mines) would revise existing SOPs in year 2; and approximately 
46 new MNM mines to write respiratory protection SOPs in year 3.
    The inclusion of ASTM F3387-19 costs in this ICR is a result of a 
change between the proposed rule and final rule. In the proposed rule, 
operators could choose which ASTM F3387-19 elements to adopt. In the 
final rule, mine operators must have a written respiratory protection 
program that meets the following requirements in accordance with ASTM 
F3387-19: program administration; written standard operating 
procedures; medical evaluation; respirator selection; training; fit 
testing; maintenance, inspection, and storage. MSHA estimates that 
3,411 mines will be affected by respiratory protection requirements, an 
annual average of 599 existing mines will have to write new respiratory 
protection SOPs, and an annual average of 569 mines will have to revise 
existing SOPs each year.
    Annual number of responses. The estimated average annual number of 
responses is 5,310, including 1,500 for records relating to miners' 
inability to wear respirators (Sec.  60.14(b)) and 3,810 for 
respiratory protection requirements of writing and updating SOPs (Sec.  
60.14 (c)(2)). MSHA estimates that the annual average of 1,500 mines 
that will need records of miners' inability to wear respirators will 
each have one miner requiring such record, totaling 1,500 records per 
year (Sec.  60.14(b)). The annual 3,810 responses concerning Sec.  
60.14 (c)(2) are estimated in the following. First, MSHA assumes that 
approximately half of the 3,411 existing mine operators affected by 
respiratory protection requirements, as well as all new mines affected 
by these requirements, will have to write new respiratory protection 
SOPs, resulting an annual average of 599 new written SOPs (553 in year 
1, 1,175 in year 2, and 68 in year 3). Second, MSHA makes a similar 
assumption that the other half of mines affected by respiratory 
protection requirements will have to revise existing ones, generating 
an annual average of 569 revised SOPs. Together, there will be a total 
of 1,168 records of new (599) and revised (569) SOPs per year. Finally, 
based on ASTM F3387-19 guidelines adopted in Sec.  60.14(c)(2) of this 
rule, MSHA determines that existing and new mine operators will keep 
records of the new and revised SOPs, which results in an annual average 
of 2,642 records in total.
    Estimated annual burden. The estimated annual burden is 11,333 
hours, including 750 for records relating to miners' inability to wear 
respirators and 10,583 for the ASTM F3387-19 incorporation by 
reference. MSHA assumes it takes 30 minutes to determine and record 
where a miner unable to wear a respirator can be temporarily 
transferred either to work in a separate area of the same mine or to an 
occupation at the same mine where respiratory protection is not 
required. This will impact one miner in each of the 1,500 affected 
mines. MSHA estimates that, on average, it takes 4 hours for mine 
operators to write respiratory protection program SOPs and 1 hour to 
revise existing respiratory protection program SOPs. For coal mines, 
MSHA estimates that it takes 4 hours in year 1 and 2 hours in years 2 
and 3 to carry out recordkeeping relating to the respiratory protection 
program SOPs. For MNM mines, MSHA estimates that it takes 4 hours in 
year 2 and 2 hours in year 3 to perform the same tasks.
d. Section 60.15--Medical Surveillance for Metal and Nonmetal Mines
    ICR. Section 60.15 requires MNM mine operators to ensure that the 
results of medical examinations or tests will be provided from the 
PLHCP or specialist

[[Page 28411]]

within 30 days of the medical examination to the miner, and at the 
request of the miner, to the miner's designated physician or another 
designee identified by the miner. MNM mine operators also must ensure 
that within 30 days of the medical examination, the PLHCP or specialist 
provides the results of chest X-ray classifications to NIOSH, once 
NIOSH establishes a reporting system [Sec.  60.15(d)(2)].
    Also, MNM mine operators must obtain a written medical opinion from 
a PLHCP or specialist regarding any recommended limitations on a 
miner's use of respirators under Sec.  60.15(e). The written medical 
opinion must contain the date of the medical examination, a statement 
that the examination has met the requirements of the section, and any 
recommended limitations on the miner's use of respirators. The written 
medical opinion record must be retained by MNM mine operators for the 
duration of a miner's employment plus 6 months under Sec.  60.16(a)(5).
    As per Sec.  60.1, the compliance date for MNM mines begins one 
year after the compliance date for coal mines.
    Number of respondents. Due to uncertainty regarding participation 
of currently employed miners, including contract workers, in medical 
surveillance programs, MSHA considered two rates (25 percent and 75 
percent) when estimating medical surveillance costs. To be consistent 
with FRIA estimates, the values presented here are the average number 
of MNM miners between the assumed participation rates of 25 percent and 
75 percent. Furthermore, MSHA expects that 50 percent of current miners 
will obtain their voluntary medical examinations in year 2, as that is 
when the compliance period begins for MNM mines. Given that the 
examinations for current miners do not need to be repeated until 5 
years later there is no cost burden associated with this cost item in 
year 3. As a result, an average of 29,371 current MNM miners are 
estimated to receive voluntary medical examinations per year (0 in year 
1, 88,112 in year 2, 0 in year 3).
    MSHA further estimates that 8,392 miners each year, including 
contract workers, are new miners and contractors working in MNM mines 
and receive mandatory medical examinations. MSHA estimates that the 
turnover of MNM miners will be 8,392 miners per year, starting from 
year 2 (1/22 of the estimated total of 184,615 MNM workers, with an 
average number of 22 years on the job before leaving the mining 
industry). This results in an annual average of 5,595 MNM miners 
receiving mandatory medical examinations (0 in year 1, 8,392 in years 2 
and 3). The estimated total respondents per year therefore will be 
34,965 (= 29,371 current miners x 5,595 new miners).
    Annual number of responses. The estimated annual number of 
responses is 34,965, including 5,595 medical opinion records for new 
miners and 29,371 records for current miners.
    Estimated annual burden. The estimated annual burden is 8,741 
hours, including 1,399 hours for new MNM miners and 7,343 hours for 
current MNM miners. MSHA estimates it will take 15 minutes to record 
the medical examination results for each of the 34,965 miners.
Total Recordkeeping Burden for Part 60
    Total recordkeeping burden for Part 60 is summarized in Table XI-1.
    [GRAPHIC] [TIFF OMITTED] TR18AP24.196
    
    The total annual number of respondents is 47,596; the total annual 
number of responses will be 265,509; and the estimated annual burden 
will be 63,972 hours.
    The following estimates of information collection burden are 
summarized in Table XI-2.
    Affected Public: Businesses or For-Profit.
    Estimated Number of Respondents: 1,106 respondents in year 1; 
109,135 respondents in the year 2; and 21,023 respondents in year 3.
    Frequency: On Occasion.
    Estimated Number of Responses: 52,821 responses in year 1; 433,240 
responses in year 2; and 310,467 responses in year 3.
    Estimated Number of Burden Hours: 18,720 hours in year 1; 109,983 
hours in year 2; and 63,215 hours in year 3.
    Estimated Hour Burden Costs: $1,260,819 in year 1; $7,704,098 in 
year 2; and $4,238,135 in year 3.

[[Page 28412]]

    Estimated Capital Costs to Respondents: $27,044 in year 1; 
$2,093,280 in year 2; and $206,725 in year 3.
[GRAPHIC] [TIFF OMITTED] TR18AP24.197

    The number of responses and burden hours decreased from year 2 to 
year 3 mainly as a result of decreases in sampling in current MNM 
mines. In year 2, MNM mines will conduct first-time and second-time 
sampling, while only a small number of new mines starting operations in 
year 3 are required to conduct this type of sampling. The increase in 
capital costs in year 2 is a result of all medical examinations for 
current miners taking place in that year.
    For a detailed summary of the burden hours and related costs by 
provision, see the FRIA accompanying the final rule. The FRIA includes 
the estimated costs and assumptions related to the paperwork 
requirements under this final rule.
2. Existing Information Collection 1219-0011
    Type of Review: Non-substantive change to currently approved 
information collection.
    OMB Control Number: 1219-0011.
    Title: Respirable Coal Mine Dust Sampling.
Description of the ICR
Background
    In October 2022, MSHA received OMB approval for the reauthorization 
of Respirable Coal Mine Dust Sampling under OMB Control Number 1219-
0011. This information collection request outlines the legal authority, 
procedures, burden, and costs associated with recordkeeping and 
reporting requirements for coal mine operators. MSHA's standards 
require that coal mine operators sample respirable coal mine dust 
quarterly and make records of such samples.
Summary of Changes
    This non-substantive change request revises the supporting 
statement for this information collection request due to the 
establishment of a PEL for respirable crystalline silica separate from 
coal mine dust in this final rule. These revisions remove any reference 
in the information collection request to quartz or the reduction of the 
respirable coal mine dust standard due the presence of quartz. This 
change does not modify the authority, affected mine operators, or 
paperwork burden in this information collection request.
Summary of the Collection of Information
Changes in Burden
    The calculated burden including respondents and responses remain 
the same.
    Affected Public: Businesses or For-Profit.
    Estimated Number of Respondents: 676 (0 from this rule).
    Frequency: On occasion.
    Estimated Number of Responses: 995,102 (0 from this rule).
    Estimated Number of Burden Hours: 58,259 (0 from this rule).
    Estimated Hour Burden Costs: $3,271,611 ($0 from this rule).
    Estimated Capital Costs to Respondents: $29,835 ($0 from this 
rule).
3. Existing Information Collection 1219-0048
    Type of Review: Substantive change to currently approved 
information collection.
    OMB Control Number: 1219-0048.
    Title: Respirator Program Records.
Description of the ICR
Background
    Title 30 CFR parts 56 and 57 incorporate by reference requirements 
of ANSI Z88.2-1969, ``Practices for Respiratory Protection.'' Under 
this standard, certain records are required to be kept in connection 
with respirators in MNM mines. The final rule incorporates by reference 
ASTM F3387-19, ``Standard Practice for Respiratory Protection,'' in 30 
CFR parts 56 and 57 to replace the Agency's existing respiratory 
protection standard. The final rule requires respiratory protection 
programs to be in writing and to meet the following requirements in 
accordance with ASTM F3387-19: program administration; written standard 
operating procedures; medical evaluation; respirator selection; 
training; fit testing; maintenance, inspection, and storage.
Summary of Changes
    This substantive change request is to revise the supporting 
statement for this information collection request due to a modification 
of respiratory protection standard from ANSI Z88.2-1969 to ASTM F3387-
19 in the final rule. These revisions require mine operators to update 
their respiratory protection standard and increase recordkeeping costs. 
The change does not modify the authority or affected mine operators but 
increases the paperwork burden and costs associated with respiratory 
protection in this information collection request.

[[Page 28413]]

Summary of the Collection of Information
Changes in Burden
    The calculated burden including respondents and responses 
increases.
    Affected Public: Businesses or For-Profit.
    Estimated Number of Respondents: 2,305 (1,955 from this rule).
    Frequency: On occasion.
    Estimated Number of Responses: 43,795 (37,495 from this rule).
    Estimated Number of Burden Hours: 23,626 (20,038 from this rule).
    Estimated Hour Burden Costs: $1,459,309 ($1,175,211 from this 
rule).
    Estimated Capital Costs to Respondents: $140,000 ($0 from this 
rule).

XII. Other Regulatory Considerations

A. National Environmental Policy Act

    The National Environmental Policy Act (NEPA) of 1969 (42 U.S.C. 
4321 et seq.), requires each Federal agency to consider the 
environmental effects of final actions and to prepare an Environmental 
Impact Statement on major actions significantly affecting the quality 
of the environment. MSHA has reviewed the final standard in accordance 
with NEPA requirements, the regulations of the Council on Environmental 
Quality (40 CFR part 1500), and the Department of Labor's NEPA 
procedures (29 CFR part 11). As a result of this review, MSHA has 
determined that this final rule will not have a significant 
environmental impact. Accordingly, MSHA has not conducted an 
environmental assessment nor provided an environmental impact 
statement.

B. The Unfunded Mandates Reform Act of 1995

    MSHA reviewed this rule according to the Unfunded Mandates Reform 
Act of 1995 (UMRA) (2 U.S.C. 1501 et seq.). Under section 202(a) of the 
UMRA, 2 U.S.C. 1532(a), an agency must prepare a written qualitative 
and quantitative assessment of any regulation that may result in the 
expenditure by State, local, or tribal governments, in the aggregate, 
or by the private sector, of $100 million (adjusted annually for 
inflation) or more in any one year. That threshold is $196 million as 
of 2023.
    The statutory authority for the final rule is provided by the Mine 
Act under sections 101(a), 103(h), and 508. 30 U.S.C. 811(a), 813(h), 
and 957. MSHA implements the provisions of the Mine Act to prevent 
death, illness, and injury from mining and promote safe and healthful 
workplaces for miners. The Mine Act requires the Secretary of Labor 
(Secretary) to develop and promulgate improved mandatory health and 
safety standards to prevent hazardous and unhealthy conditions and 
protect the health and safety of the nation's miners. 30 U.S.C. 811(a).
    MSHA concludes that the final rule would impose a federal mandate 
on the private sector in excess of $196 million in expenditures in one 
of the 60-year implementation years, as documented in the standalone 
FRIA document (see Table C-2, Appendix C). The expenditure burden on 
the private sector will be borne by mine operators. Such expenditures 
may include conducting exposure monitoring; selecting, improving, and 
implementing exposure controls; providing respiratory protection; 
updating respiratory protection practices in accordance with the 2019 
ASTM standard; and, for MNM mine operators, making specified medical 
examinations available for all their miners. However, the rule will not 
require State, local, or tribal governments to expend, in the 
aggregate, $196 million or more in any one year for their commercial 
activities. Accordingly, the rule does not trigger the requirements of 
the UMRA based on its impact on State, local, or tribal governments.
    Section 202(c) of the UMRA, 2 U.S.C. 1532(c), authorizes a Federal 
agency to prepare any written statement required under section 202(a) 
of the UMRA in conjunction with or as a part of any other statement or 
analysis that accompanies the final rule. The FRIA constitutes the 
written statement containing a qualitative and quantitative assessment 
of these anticipated costs and benefits required under Section 202(a) 
of the UMRA.
    In addition, section 205(a) of UMRA, 2 U.S.C. 1535(a), requires 
MSHA to identify and consider a reasonable number of regulatory 
alternatives before promulgating a rule for which a written statement 
under section 202 is required. MSHA is required to select from those 
alternatives the most cost-effective and least burdensome alternative 
that achieves the objectives of the rule unless the Agency publishes an 
explanation for doing otherwise, or the selection of such an 
alternative is inconsistent with law. After considering three 
regulatory alternatives, this final rule presents a comprehensive 
approach for lowering miners' exposure to respirable crystalline silica 
and MSHA has determined the rule is both technologically feasible and 
economically justified as described in Section VII. Feasibility. A full 
discussion of the alternatives considered is presented in Section IX. 
Summary of the Final Regulatory Impact Analysis and Regulatory 
Alternatives and the standalone FRIA document.

C. The Treasury and General Government Appropriations Act of 1999: 
Assessment of Federal Regulations and Policies on Families

    Section 654 of the Treasury and General Government Appropriations 
Act of 1999 (5 U.S.C. 601 note) requires agencies to assess the impact 
of Agency action on family well-being. MSHA has determined that the 
final rule will have no effect on family stability or safety, marital 
commitment, parental rights and authority, or income or poverty of 
families and children, as defined in the Act. The final rule impacts 
the mining industry and does not impose requirements on states or 
families. Accordingly, MSHA certifies that this final rule will not 
impact family well-being, as defined in the Act.

D. Executive Order 12630: Government Actions and Interference With 
Constitutionally Protected Property Rights

    Section 5 of E.O. 12630 requires Federal agencies to ``identify the 
takings implications of proposed regulatory actions . . .'' MSHA has 
determined that the final rule does not implement a taking of private 
property or otherwise have takings implications. Accordingly, E.O. 
12630 requires no further Agency action or analysis.

E. Executive Order 12988: Civil Justice Reform

    The final rule was written to provide a clear legal standard for 
affected conduct and was carefully reviewed to eliminate drafting 
errors and ambiguities to minimize litigation and avoid undue burden on 
the Federal court system. Accordingly, the final rule meets the 
applicable standards provided in section 3 of E.O. 12988, Civil Justice 
Reform.

F. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    E.O. 13045 requires Federal agencies submitting covered regulatory 
actions to OMB's Office of Information and Regulatory Affairs (OIRA) 
for review, pursuant to E.O. 12866, to provide OIRA with (1) an 
evaluation of the environmental health or safety effects that the 
planned regulation may have on children, and (2) an explanation of why 
the planned regulation is preferable to other potentially effective and 
reasonably feasible alternatives considered by the agency. In E.O. 
13045,

[[Page 28414]]

``covered regulatory action'' is defined as rules that may (1) be 
significant under Executive Order 12866 Section 3(f)(1) (i.e., a 
rulemaking that has an annual effect on the economy of $200 million or 
more or would adversely affect in a material way the economy, a sector 
of the economy, productivity, competition, jobs, the environment, 
public health or safety, or State, local, territorial, or tribal 
governments or communities), and (2) concern an environmental health 
risk or safety risk that an agency has reason to believe may 
disproportionately affect children. Environmental health risks and 
safety risks refer to risks to health or to safety that are 
attributable to products or substances that the child is likely to come 
in to contact with or ingest through air, food, water, soil, or product 
use or exposure.
    MSHA has determined that, in accordance with E.O. 13045, while the 
final rule is considered significant under E.O. 12866 Section 3(f)(1), 
it does not concern an environmental health or safety risk that may 
have a disproportionate impact on children. MSHA's final rule would 
lower the occupational exposure limit to respirable crystalline silica 
for all miners, including pregnant miners, take other actions to 
protect miners from adverse health risks associated with exposure to 
respirable crystalline silica, and require updated respiratory 
standards to better protect miners from airborne contaminants.
    MSHA is aware of studies which have characterized and assessed the 
risks posed by ``take-home'' exposure pathways for hazardous dust 
particles. However, the final rule's primary reliance on engineering 
and administrative controls to protect miners from respirable 
crystalline silica exposures helps minimize risks associated with 
``take-home'' exposures by reducing or eliminating silica that is in 
the mine atmosphere or the miner's personal breathing zone. The risks 
of take-home exposures are further minimized by MSHA's existing 
standards, mine operators' policies and procedures, and mine operators' 
use of clothing cleaning systems.
    MSHA's existing standards limit miners' exposures to respirable 
crystalline silica. MSHA also requires coal mine operators to provide 
miners with bathing facilities and change rooms. Miners have access to 
these facilities to shower and change their work clothes at the end of 
each shift. In addition, some mine operators provide miners with clean 
company clothing for each shift, have policies and procedures for 
cleaning or disposing of contaminated clothing, and provide a boot wash 
for miners to clean work boots during and after each shift. Moreover, 
some mine operators use clothing cleaning systems that can remove dust 
from a miner's clothing. Many of these systems include NIOSH-designed 
dust removal booths that use compressed air to remove dust, which is 
then vacuumed through a filter to remove airborne contaminants. 
Overall, the Agency's standards, mine operators' policies and 
procedures, and other safety and health practices including the use of 
clothing cleaning systems help to reduce or eliminate the amount of 
take-home exposure, therefore protecting other persons in a miner's 
household or persons who come into contact with the miner outside of 
the mine site.
    MSHA identified one epidemiological study (Onyije et al., 2022) 
that suggests a possible association between paternal exposure to 
respirable crystalline silica and childhood leukemia. However, this 
study does not provide dose-response data which would be needed to 
establish the dose of respirable crystalline silica which results in a 
no-adverse-effect-level (NOAEL) for childhood leukemia. This potential 
association has not been independently confirmed by another study.
    MSHA has no evidence that the environmental health or safety risks 
posed by respirable crystalline silica, including ``take-home'' 
exposure to respirable crystalline silica, disproportionately affect 
children. Therefore, MSHA concludes no further analysis or action is 
needed, in accordance with E.O. 13045.

G. Executive Order 13132: Federalism

    MSHA has determined that the final rule does not have ``federalism 
implications'' because it will not ``have substantial direct effects on 
the States, on the relationship between the national government and the 
States, or on the distribution of power and responsibilities among the 
various levels of government.'' Accordingly, under E.O. 13132, no 
further Agency action or analysis is required.

H. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    MSHA has determined the final rule does not have ``tribal 
implications'' because it will not ``have substantial direct effects on 
one or more Indian tribes, on the relationship between the Federal 
Government and Indian tribes, or on the distribution of power and 
responsibilities between the Federal Government and Indian tribes.'' 
Accordingly, under E.O. 13175, no further Agency action or analysis is 
required.

I. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    E.O. 13211 requires agencies to publish a Statement of Energy 
Effects for ``significant energy actions,'' which are agency actions 
that are ``likely to have a significant adverse effect on the supply, 
distribution, or use of energy'' including a ``shortfall in supply, 
price increases, and increased use of foreign supplies.'' MSHA has 
reviewed the final rule for its impact on the supply, distribution, and 
use of energy because it applies to the mining industry. The final rule 
would result in annualized compliance costs of $8.2 million using a 3 
percent discount rate and $8.6 million using a 7 percent discount rate 
for the coal industry relative to annual revenue of $29.1 billion. The 
final rule would also result in annualized compliance costs of $81.9 
million using a 3 percent discount rate and $83.6 million using a 7 
percent discount rate for the metal/nonmetal mine industry relative to 
annual revenue of $95.1 billion. Because it is not ``likely to have a 
significant adverse effect on the supply, distribution, or use of 
energy'' including a ``shortfall in supply, price increases, and 
increased use of foreign supplies,'' it is not a ``significant energy 
action.'' Accordingly, E.O. 13211 requires no further agency action or 
analysis.

J. Executive Order 13272: Proper Consideration of Small Entities in 
Agency Rulemaking

    MSHA has thoroughly reviewed the final rule to assess and take 
appropriate account of its potential impact on small businesses, small 
governmental jurisdictions, and small organizations. MSHA's analysis is 
presented in Section X. Final Regulatory Flexibility Analysis.

K. Executive Order 13985: Advancing Racial Equity and Support for 
Underserved Communities Through the Federal Government

    E.O. 13985 provides ``that the Federal Government should pursue a 
comprehensive approach to advancing equity for all, including people of 
color and others who have been historically underserved, marginalized, 
and adversely affected by persistent poverty and inequality.'' E.O. 
13985 defines ``equity'' as ``consistent and systematic fair, just, and 
impartial treatment of all individuals, including individuals who 
belong to underserved communities that have been denied such treatment, 
such

[[Page 28415]]

as Black, Latino, and Indigenous and Native American persons, Asian 
Americans and Pacific Islanders and other persons of color; members of 
religious minorities; lesbian, gay, bisexual, transgender, and queer 
(LGBTQ+) persons; persons with disabilities; persons who live in rural 
areas; and persons otherwise adversely affected by persistent poverty 
or inequality.'' To assess the impact of the final rule on equity, MSHA 
considered two factors: (1) the racial/ethnic distribution in mining in 
NAICS 212 (which does not include oil and gas extraction) compared to 
the racial/ethnic distribution of the U.S. workforce (Table XII-1), and 
(2) the extent to which mining may be concentrated within general 
mining communities (Table XII-2).
    In 2008, NIOSH conducted a survey of mines, which entailed sending 
a survey packet to 2,321 mining operations to collect a wide range of 
information, including demographic information on miners. NIOSH's 2012 
report, entitled ``National Survey of the Mining Population: Part I: 
Employees'' reported the findings of this survey (NIOSH, 2012a). Race 
and ethnicity information about U.S. mine workers is presented in Table 
XII-1. Of all mine workers, including miners as well as administrative 
employees at mines, 93.4 percent of mine workers were white, compared 
to 80.6 percent of all U.S workers.\111\ There were larger percentages 
of American Indian or Alaska Native and Native Hawaiian or Other 
Pacific Islander people in the mining industry compared to all U.S. 
workers, while there were smaller percentages of Asian, Black or 
African American, and Hispanic/Latino people in the mining industry 
compared to all U.S. workers.
---------------------------------------------------------------------------

    \111\ National data on workers by race were not available for 
the year 2008; comparable data for 2012 are provided for comparison 
under the assumption that there would not be major differences in 
distributions between these two years.
---------------------------------------------------------------------------

    Table XII-2 shows that there are 22 mining communities, defined as 
counties where at least 2 percent of the population is working in the 
mining industry.\112\ Although the total population in this table 
represents only 0.15 percent of the U.S. population, it represents 12.0 
percent of all mine workers. The average per capita income in these 
communities in 2020, $47,977,\113\ was lower than the U.S. average, 
$59,510, representing 80.6 percent of the U.S. average. However, each 
county's average per capita income varies substantially, ranging from 
56.4 percent of the U.S. average to 146.8 percent.
---------------------------------------------------------------------------

    \112\ Although 2 percent may appear to be a small number for 
identifying a mining community, one might consider that if the 
average household with one parent working as a miner has five 
members in total, then approximately 10 percent of households in the 
area would be directly associated with mining. While 10 percent may 
also appear small, this refers to the county. There are likely 
particular areas that have a heavier concentration of mining 
households.
    \113\ This is a simple average rather than a weighted average by 
population.
---------------------------------------------------------------------------

    The final rule would lower exposure to respirable crystalline 
silica and improve respiratory protection for all mine workers. MSHA 
determined that the final rule is consistent with the goals of E.O. 
13985 and would support the advancement of equity for all workers at 
mines, including those who are historically underserved and 
marginalized.
BILLING CODE 4520-43-P

[[Page 28416]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.198

BILLING CODE 4520-43-C

[[Page 28417]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.199

L. Incorporation by Reference

    The Office of the Federal Register (OFR) has regulations concerning 
incorporation by reference. 5 U.S.C. 552(a); 1 CFR part 51. These 
regulations require that information that is incorporated by reference 
in a rule be ``reasonably available'' to the public. They also require 
discussion in the preamble to the rule of the ways in which materials 
are reasonably available to interested parties or how the Agency worked 
to make those materials reasonably available to interested parties. 
Additionally, the preamble to the rule must summarize the material. 1 
CFR 51.5(b).

[[Page 28418]]

    In accordance with the OFR's requirements, MSHA provides the 
following: (a) summaries of the materials to be incorporated by 
reference and (b) information on the public availability of the 
materials and on how interested parties can access the materials.
ASTM F3387-19, ``Standard Practice for Respiratory Protection''
    ASTM F3387-19 is a voluntary consensus standard that represents up-
to-date advancements in respiratory protection technologies, practices, 
and techniques. The standard includes provisions for selection, 
fitting, use, and care of respirators designed to remove airborne 
contaminants from the air using filters, cartridges, or canisters, as 
well as respirators that protect miners in oxygen-deficient or 
immediately dangerous to life or health atmospheres. These provisions 
are based on NIOSH's long-standing experience of testing and approving 
respirators for occupational use and OSHA's respiratory protection 
standards on assigned protection factors and fit testing. This final 
rule incorporates by reference ASTM F3387-19 in Sec. Sec.  56.5005T, 
57.5005T, and 72.710T (which will become permanent Sec. Sec.  56.5005 
and 57.5005 720 days after publication and permanent Sec.  72.710 360 
days after publication) and in Sec.  60.14(c)(2) to better protect all 
miners from airborne contaminants. MSHA believes that incorporating by 
reference ASTM F3387-19 provides mine operators with up-to-date 
requirements for respirator technology, reflecting an improved 
understanding of effective respiratory protection and therefore better 
protecting the health and safety of miners. For further details on 
MSHA's update to the Agency's existing respiratory protection standard, 
please see Section VIII.D. Updating MSHA Respiratory Protection 
Standards: Incorporation of ASTM F3387-19 by Reference.
    A paper copy or printable version of ASTM F3387-19 may be purchased 
by mine operators or any member of the public at any time from ASTM 
International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, 
PA 19428-2959; www.astm.org. ASTM International makes read-only 
versions of its standards that have been referenced or incorporated 
into Federal regulation or laws available free of charge at its online 
Reading Room, www.astm.org/products-services/reading-room.html.
    In addition, upon finalization of this rule, ASTM F3387-19 will be 
available for review free of charge at MSHA headquarters at 201 12th 
Street South, Arlington, VA 22202-5450 (202-693-9440) and at Mine 
Safety Health Enforcement District and Field Offices.
ISO 7708:1995(E): Air quality--Particle Size Fraction Definitions for 
Health-Related Sampling
    ISO 7708:1995 is an international consensus standard that defines 
sampling conventions for particle size fractions used in assessing 
possible health effects of airborne particles in the workplace and 
ambient environment. It defines conventions for the inhalable, 
thoracic, and respirable fractions. The final rule incorporates by 
reference ISO 7708:1995 in Sec.  60.12(e)(4) to ensure consistent 
sampling collection by mine operators through the utilization of 
samplers conforming to ISO 7708:1995. For further details on MSHA's 
incorporation by reference of ISO 7708:1995, please see Section 
VIII.B.5.d. Sampling Devices: Incorporation of ISO 7708:1995 by 
Reference.
    A paper copy or printable version of ISO 7708:1995 may be purchased 
by mine operators or any member of the public at any time from ISO, CP 
56, CH-1211 Geneva 20, Switzerland; phone: + 41 22 749 01 11; fax: + 41 
22 733 34 30; website: www.iso.org/. ISO makes read-only versions of 
its standards that have been incorporated by reference in the CFR 
available free of charge at its online Incorporation by Reference 
Portal, http://ibr.ansi.org/Default.aspx.
    In addition, upon finalization of this rule, ISO 7708:1995 will be 
available for review free of charge at MSHA headquarters at 201 12th 
Street South, Arlington, VA 22202-5450 (202-693-9440) and at Mine 
Safety Health Enforcement District and Field Offices.
TLVs[supreg] Threshold Limit Values for Chemical Substances in Workroom 
Air Adopted by ACGIH for 1973
    ACGIH's publication entitled ``TLVs[supreg] Threshold Limit Values 
for Chemical Substances in Workroom Air Adopted by ACGIH for 1973'' 
presents Threshold Limit Value (TLV[supreg]) guidelines for hundreds of 
chemical substances found in the work environment (particulates, gases, 
and vapors). TLVs[supreg] are airborne concentrations of chemical 
substances that represent conditions under which it is believed that 
nearly all workers may be repeatedly exposed, day after day, over a 
working lifetime, without adverse effects. TLVs[supreg] generally refer 
to time-weighted average concentrations (TWAs) for a 7 or 8-hour 
workday and 40-hour workweek that are applied as guidelines in the 
control of health hazards.
    TLVs[supreg], which appears the amendatory text of this rule, was 
previously approved for use in Sec. Sec.  56.5001 and 57.5001.
    Copies of the document may be purchased from the American 
Conference of Governmental Industrial Hygienists, 3640 Park 42 Drive, 
Cincinnati, OH 45241; 513-742-2020; http://www.acgih.org. This 
publication is also available for examination free of charge at MSHA's 
Office of Standards, Regulations, and Variances, 201 12th Street South, 
Arlington, VA 22202-5452; 202-693-9440; and at Mine Safety and Health 
Enforcement District and Field Offices.
American National Standards Practices for Respiratory Protection ANSI 
Z88.2-1969.
    ANSI Z88.2-1969, which appears the amendatory text of this rule, 
was previously approved for use in Sec.  72.710.

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Almberg, K.S., Cohen, R.A., Blackley, D.J., Laney, A.S., Storey, E., 
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XIV. Appendix

Appendix A--Description of MSHA Respirable Crystalline Silica Samples

    This document describes the respirable crystalline silica 
samples used in this rule. The Mine Safety and Health Administration 
(MSHA) collected these samples from metal/nonmetal (MNM) and coal 
mines, then analyzed the data to support this rulemaking. Technical 
details are discussed in the attachments that follow.

MNM Respirable Dust Sample Dataset, 2005-2019

    From January 1, 2005, to December 31, 2019, 104,354 valid MNM 
respirable dust samples were entered into the MSHA Technical Support 
Laboratory Information Management System (LIMS) database.\114\ The 
dataset includes MNM mine respirable dust personal exposure samples 
collected by MSHA inspectors. A total of 57,824 samples contained a 
respirable dust mass of 0.100 mg or greater (referred as 
``sufficient-mass dust samples''), while a total of 46,530 samples 
contained a respirable dust mass of less than 0.100 mg (referred as 
``insufficient-mass dust samples'').\115\
---------------------------------------------------------------------------

    \114\ Only valid (non-void) MNM respirable dust samples were 
included in the LIMS dataset. Voided samples include any samples 
with a documented reason which occurred during the sampling and/or 
the MSHA's laboratory analysis for invalidating the results.
    \115\ Sufficient-mass dust samples are analyzed for their quartz 
content, whereas insufficient-mass dust samples are not. This is 
because even if the insufficient-mass dust samples contained only 
quartz they would not have exceeded the permissible exposure limit 
(PEL) at that time.
---------------------------------------------------------------------------

    Respirable dust samples collected by MSHA inspectors are 
assigned a three-digit ``contaminant code'' based on the contaminant 
in the sample. MSHA's contaminant codes group contaminants based on 
their health effects \116\ and are assigned by the MSHA Laboratory 
based on sample type and analysis results. The codes link 
information to the sample, such as contaminant description, 
permissible exposure limit (PEL), and the units of measure for each 
contaminant sampled.
---------------------------------------------------------------------------

    \116\ For example, contaminant code 523 indicates that dust from 
that sample contained 1 percent or more respirable crystalline 
silica (quartz). Exposure to respirable crystalline silica has been 
linked to the following health outcomes: silicosis, non-malignant 
respiratory disease, lung cancer, and renal disease.
---------------------------------------------------------------------------

    The MNM respirable crystalline silica dataset includes five 
contaminant codes.

MNM Respirable Dust Sample Contaminant Codes

     Contaminant code 521--MNM respirable dust samples that 
were not analyzed for respirable crystalline silica.
     Contaminant code 523--MNM respirable dust samples 
containing 1 percent or more quartz.
     Contaminant code 525--MNM respirable dust samples 
containing cristobalite.
     Contaminant code 121--MNM respirable dust samples 
containing less than 1 percent quartz where the commodity is listed 
as a ``nuisance particulate'' in Appendix E of the TLVs[supreg] 
Threshold Limit Values for Chemical Substances in Workroom Air 
Adopted by ACGIH for 1973 (reproduced in Table A-1).
     Contaminant code 131--MNM respirable dust samples 
containing less than 1 percent quartz where the commodity is not 
listed as a ``nuisance particulate'' in Appendix E of the 1973 ACGIH 
TLV[supreg] Handbook (reproduced below).

[[Page 28432]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.130

MNM Respirable Dust Samples With a Mass of at Least 0.100 Milligram 
(mg) (Sufficient-Mass Dust Samples)

    The 57,824 samples that contained at least 0.100 mg of 
respirable dust were analyzed to quantify their respirable 
crystalline silica content--mostly respirable quartz but also 
respirable cristobalite. The respirable crystalline silica 
concentrations were entered into the MSHA Standardized Information 
System (MSIS) database (internal facing) and Mine Data Retrieval 
System (MDRS) database (public facing). MSIS and MDRS differ from 
LIMS in that some of the fields associated with a sample can be 
modified or corrected by the inspector who conducted the sampling. 
These correctable fields include Mine ID, Location Code, and Job 
Code. Inspectors cannot access or modify the fields in the LIMS 
database.
    Fifty-five samples \117\ were removed from the dataset because 
they were erroneous, had an incorrect flow rate, had insufficient 
sampling time, or were duplicates. This resulted in a final dataset 
consisting of 57,769 MNM samples that contained a mass of at least 
0.100 mg of respirable dust. The dataset containing the analyzed 
samples that MSHA retained can be found in the rulemaking docket 
MSHA-2023-0001.
---------------------------------------------------------------------------

    \117\ There were 55 samples removed: 7 samples had no detected 
mass gain (denoted as ``0 mg''); 1 sample was a partial shift that 
was not originally marked correctly; 1 sample was removed at the 
request of the district; 44 samples had flow rates outside the 
acceptable range of 1.616-1.785 L/min; and 2 samples were duplicates 
of samples that were already in the dataset. This resulted in the 
final sample size of 57,769 = 57,824-(7 + 1 + 1 + 44 + 2).
---------------------------------------------------------------------------

MNM Respirable Dust Samples With a Mass of Less Than 0.100 mg 
(Insufficient-Mass Dust Samples)

    The LIMS database also included 46,530 MNM respirable dust 
samples that contained less than 0.100 mg of respirable dust. These 
samples did not meet the minimum dust mass criterion of 0.100 mg and 
were not analyzed for respirable crystalline silica by MSHA's 
Laboratory.
    From these 46,530 samples, 167 samples \118\ were removed 
because they were erroneous, had an incorrect flow rate, or had 
insufficient sampling time. This resulted in 46,363 remaining MNM 
samples containing less than 0.100 mg of respirable dust. These 
samples were assigned to contaminant code 521, indicating that the 
samples were not analyzed for quartz. The dataset containing the 
unanalyzed samples that MSHA retained can be found in the rulemaking 
docket MSHA-2023-0001.
---------------------------------------------------------------------------

    \118\ There were 167 samples removed: 75 samples had a cassette 
mass less than -0.03 mg (based on instrument tolerances, samples 
that report a cassette mass between -0.03 mg and 0 mg were treated 
as having a mass of 0 mg, samples with masses below that threshold 
of -0.03 mg were excluded); 52 samples had Mine IDs that did not 
report employment in any year from 2005-2019; 31 samples had flow 
rates outside the acceptable range of 1.615-1.785 L/min ; six 
samples had sampling times of less than 30 minutes; and three 
samples had invalid Job Codes. This resulted in the final sample 
size of 46,363 = 46,530-(75 + 52 + 31 + 6 + 3).
---------------------------------------------------------------------------

All MNM Respirable Dust Samples

    After removing the 222 samples mentioned above (55 sufficient-
mass and 167 insufficient-mass), the dataset consisted of 104,132 
MNM respirable dust samples: 57,769 sufficient-mass samples and 
46,363 insufficient-mass samples. A breakdown of the MNM respirable 
dust samples is included in Table A-2.

[[Page 28433]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.200

Coal Respirable Dust Sample Dataset, 2016-2021

    From August 1, 2016, to July 31, 2021, 113,607 valid respirable 
dust samples from coal mines were collected by MSHA inspectors and 
entered in the LIMS database.\119\ For coal mines, the reason the 
analysis is based on samples collected by inspectors beginning on 
August 1, 2016, is that this is when Phase III of MSHA's 2014 RCMD 
Standard went into effect. Samples taken prior to implementation of 
the RCMD standard would not be representative of current respirable 
crystalline silica exposure levels in coal mines.
---------------------------------------------------------------------------

    \119\ Only valid (non-void) coal respirable dust samples were 
included in the LIMS dataset. Voided samples include any samples 
with a documented reason which occurred during the sampling and/or 
the MSHA's Laboratory analysis for invalidating the results.
---------------------------------------------------------------------------

    Of these samples collected by MSHA inspectors, 67,963 samples 
were analyzed for respirable crystalline silica; 45,644 samples were 
not. The record of a respirable dust sample from coal mines contains 
a record of the sample type and the occupation of the miner sampled. 
A coal sample's type is based on the location within the mine as 
well as the occupation of the miner sampled. Below is a list of coal 
sample types and descriptions, as well as the mass of respirable 
dust required for that type of sample to be analyzed for respirable 
crystalline silica.
     Type 1--Designated occupation (DO). The occupation on a 
mechanized mining unit (MMU) that has been determined by results of 
respirable dust samples to have the greatest respirable dust 
concentration. Designated occupation samples must contain at least 
0.100 mg of respirable dust to be analyzed for respirable 
crystalline silica.
     Type 2--Other designated occupation (ODO). Occupations 
other than the DO on an MMU that are also designated for sampling, 
required by 30 CFR part 70. These samples must contain at least 
0.100 mg of respirable dust to be analyzed for respirable 
crystalline silica.
     Type 3--Designated area (DA). Designated area samples 
are from specific locations in the mine identified by the operator 
in the mine ventilation plan under 30 CFR 75.371(t), where samples 
will be collected to measure respirable dust generation sources in 
the active workings. These samples must contain at least 0.100 mg of 
respirable dust to be analyzed for respirable crystalline silica.
     Type 4--Designated work position (DWP). A designated 
work position in a surface coal mine or surface work area of an 
underground coal mine that is designated for sampling in order to 
measure respirable dust generation sources in the active workings. 
Designated work position samples must contain at least 0.200 mg of 
respirable dust to be analyzed for respirable crystalline silica. 
There are exceptions for certain occupations: bulldozer operator 
(MSIS general occupation code 368), high wall drill operator (code 
384), high wall drill helper (code 383), blaster/shotfirer (code 
307), refuse/backfill truck driver (code 386), or high lift 
operator/front end loader (code 382). Samples from these occupations 
must have at least 0.100 mg of respirable dust to be analyzed for 
respirable crystalline silica.
     Type 5--Part 90 miner. A Part 90 miner is employed at a 
coal mine and has exercised the option under the old section 203(b) 
program (36 FR 20601, Oct. 27, 1971) or under 30 CFR 90.3 to work in 
an area of a mine where the average concentration of respirable dust 
in the mine atmosphere during each shift to which a miner is exposed 
is continuously maintained at or below the applicable standard and 
has not waived these rights. A sample from a Part 90 miner must 
contain at least 0.100 mg of respirable dust to be analyzed for 
respirable crystalline silica.
     Type 6--Non-designated area (NDA). Non-designated area 
samples are taken from locations in the mine that are not identified 
by the operator in the mine ventilation plan under 30 CFR 75.371(t) 
as areas where samples will be collected to measure respirable dust 
generation sources in the active workings. These samples are not 
analyzed for respirable crystalline silica.
     Type 7--Intake air samples are taken from air that has 
not yet ventilated the last working place on any split of any 
working section or any worked-out area, whether pillared or non-
pillared, as per 30 CFR 75.301. These samples are not analyzed for 
respirable crystalline silica.

[[Page 28434]]

     Type 8--Non-designated work position (NDWP). A work 
position in a surface coal mine or a surface work area of an 
underground coal mine that is sampled during a regular health 
inspection to measure respirable dust generation sources in the 
active workings but has not been designated for mandatory sampling. 
For the analysis of respirable crystalline silica, these samples 
must have at least 0.200 mg of respirable dust. There are exceptions 
for certain occupations: bulldozer operator (MSIS general occupation 
code 368), high wall drill operator (code 384), high wall drill 
helper (code 383), blaster/shotfirer (code 307), refuse/backfill 
truck driver (code 386), or high lift operator/front end loader 
(code 382). Samples taken from these occupations must contain at 
least 0.100 mg respirable dust to be analyzed for respirable 
crystalline silica.

Coal Respirable Dust Samples Analyzed for Respirable Crystalline Silica

    There were 67,963 samples from coal mines collected by MSHA 
inspectors from underground and surface coal mining operations that 
were analyzed for respirable crystalline silica. These results were 
entered first into LIMS, and then into MSIS and MDRS. Results from 
MSIS were used as they may be updated by the inspectors at later 
dates.\120\ From those 67,963 samples, 4,836 samples were removed as 
they were environmental samples, voided in MSIS, or had other 
errors.\121\ This resulted in a dataset of 63,127 samples from coal 
mines that were analyzed for respirable crystalline silica. The 
dataset containing the analyzed samples that MSHA retained can be 
found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------

    \120\ As mentioned in the section concerning samples for MNM 
mines, MSIS and MDRS differ from LIMS in that some data fields can 
be modified or corrected by the inspector. These correctable fields 
include market.
    \121\ There were 4,836 samples removed: 4,199 samples were 
environmental and not personal samples (see Sample Type explanation 
for more detail); 631 samples had been voided after they had been 
entered into MSIS; and 6 had invalid Job Codes. This resulted in the 
final sample size of 63,127 = 67,963-(4,199 + 631 + 6).
---------------------------------------------------------------------------

Coal Respirable Dust Samples Not Analyzed for Respirable Crystalline 
Silica

    Similar to MNM respirable dust samples, the LIMS database 
includes 45,644 coal samples that did not meet the criteria for 
analysis and were thus not analyzed for respirable crystalline 
silica content.\122\ After removing 13,243 \123\ samples that were 
environmental samples, erroneous, or had voided controls, there were 
32,401 samples that were not analyzed for respirable crystalline 
silica. The dataset containing the unanalyzed samples that MSHA 
retained can be found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------

    \122\ In addition to the criteria listed above, samples from 
Shop Welders (code 319) are not analyzed for respirable crystalline 
silica as they are instead analyzed for welding fumes.
    \123\ There were 13,243 samples removed: 6 samples had 
typographical errors; 14 samples had a cassette mass less than -0.03 
mg (based on instrument tolerances, samples that report a cassette 
mass between -0.03 mg and 0 mg were treated as having a mass of 0 
mg); 92 samples had invalid Job Codes; 12,724 were environmental 
samples; 44 samples had an occupation code of 000 despite having a 
personal sample `Sample Type'; 271 samples had controls that were 
voided; and 92 came from Job Code 319--Welder (see Footnote 119). 
This resulted in the final sample size of 32,401 = 50,545-(6 + 14 + 
92 + 12,724 + 44 + 271 + 92).
---------------------------------------------------------------------------

All Coal Respirable Dust Samples

    In total, 18,079 respirable dust samples from coal mines were 
removed from the original datasets: 4,836 samples that were analyzed 
for respirable crystalline silica and 13,243 samples that were not. 
This created a final dataset of 95,528 samples: 63,127 analyzed 
samples and 32,401 samples that were not analyzed.\124\ A breakdown 
of respirable dust samples from coal mines is included in Table A-3.
---------------------------------------------------------------------------

    \124\ This dataset did not include any other coal mine 
respirable dust sample types collected by MSHA inspectors--i.e., 
sample types 3 (designated area samples), types 6 (Non-face 
occupations) and 7 (Intake air), samples taken on the surface mine 
shop welder (n=319), and all voided samples. Voided samples are any 
samples that have a documented reason which occurred during the 
sampling and/or laboratory analysis for invalidating the results.
[GRAPHIC] [TIFF OMITTED] TR18AP24.201


[[Page 28435]]



Attachment 1. MNM Samples Analyzed for Cristobalite

    Cristobalite is one of the three polymorphs of respirable 
crystalline silica. At the request of the inspector, MNM \125\ 
respirable dust samples that contain at least 0.050 mg of respirable 
dust are analyzed for cristobalite. Of the 57,769 retained MNM 
samples that contained at least 0.050 mg of respirable dust, 0.6 
percent (or 359 samples) were analyzed for cristobalite. Coal 
respirable dust samples are not analyzed for cristobalite.\126\
---------------------------------------------------------------------------

    \125\ See Attachment 2. Technical Background about Measuring 
Respirable Crystalline Silica, for more information.
    \126\ See Attachment 2. Technical Background about Measuring 
Respirable Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TR18AP24.202

    While the samples that were analyzed for cristobalite were 
assigned to all four contaminant codes seen in this dataset, the 
majority were assigned contaminant code 523.
[GRAPHIC] [TIFF OMITTED] TR18AP24.203

    The distribution of the 359 samples by cristobalite mass can be 
seen in Table A1-3.\127\
---------------------------------------------------------------------------

    \127\ Of the 369 samples that were analyzed for cristobalite, 
334 had a value for cristobalite mass that was less than the limit 
of detection (LOD) for cristobalite, 10[mu]g. As such these samples 
were assigned a value of 5[mu]g of cristobalite, one half the LOD. 
See Attachment 2. Technical Background about Measuring Respirable 
Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TR18AP24.204


[[Page 28436]]


    The mass of each sample was then used to calculate a 
cristobalite concentration by dividing the mass of cristobalite by 
the volume of air sampled (0.816 m\3\). The calculated 
concentrations ranged from 6[mu]g/m\3\ to 53[mu]g/m\3\.\128\
---------------------------------------------------------------------------

    \128\ One sample had a cristobalite concentration of 53[mu]g/
m\3\. It was sampled in July of 2011 at Mine ID 4405407 and cassette 
number 610892. The commodity being mined was Stone: Crushed, Broken 
Quartzite. The occupation of the miner being sampled was Miners in 
Other Occupations: Job Code 513--Building and Maintenance.
[GRAPHIC] [TIFF OMITTED] TR18AP24.205

Attachment 2. Technical Background About Measuring Respirable 
Crystalline Silica

    In the proposed rule, respirable crystalline silica refers to 
three polymorphs: quartz, cristobalite, and tridymite. MSHA's 
Laboratory uses two methods to analyze respirable crystalline silica 
content in respirable dust samples. The first method, X-ray 
diffraction (XRD), separately analyzes quartz, cristobalite, and 
tridymite contents in respirable dust samples that mine inspectors 
obtain at MNM mine sites (MSHA Method P-2, 2018a). The second 
method, Fourier transform infrared spectroscopy (FTIR), is used to 
analyze quartz in respirable dust samples obtained at coal mines 
(MSHA Method P-7, 2018b and 2020b). Although the XRD method can be 
expanded from MNM to coal dust samples, MSHA chooses to use the FTIR 
method for coal dust samples because it is a faster and less 
expensive method. However, the current MSHA P-7 FTIR method cannot 
quantify quartz if cristobalite and/or tridymite are present in the 
sample. The method also corrects the quartz result for the presence 
of kaolinite, an interfering mineral for quartz analysis when found 
in coal dust.

Limits of Detection and Limits of Quantification for Silica Sample Data

    The Limits of Detection (LOD) and Limits of Quantification (LOQ) 
are the two terms used to describe a method's capability. The LOD 
refers to the smallest amount of the target analyte (respirable 
crystalline silica) that can be detected in the sample and 
distinguished from zero with an acceptable confidence level that the 
analyte is actually present. It can also be described as the 
instrument signal that is needed to report with a specified 
confidence that the analyte is present. The LOQ refers to the 
smallest amount of the target analyte that can be repeatedly and 
accurately quantified in the sample with a specified precision. The 
LOQ is higher than the LOD. The values of the LOD and LOQ are 
specific to MSHA's Laboratory as well as the instrumentation and 
analytical method used to perform the analysis. These values do not 
change from one batch to another when samples are analyzed on the 
same equipment using the same method. However, their levels may 
change over time due to updated analytical methods and technological 
advances. The values of the LOD and LOQ for the methods (XRD and 
FTIR) used in analyzing respirable crystalline silica samples are 
explained in MSHA documents for MNM samples and coal samples (MSHA 
Method P-2, 2018a; MSHA Method P-7, 2018b and 2020b). MSHA 
periodically updates these values to reflect progress in its 
analytical methods. The values of LOD and LOQ were last updated in 
2022 for MNM samples and in 2020 for coal samples.
    The values of LODs and LOQs for respirable crystalline silica in 
samples from MSHA inspectors depend on several factors, including 
the analytical method used (XRD or FTIR) and the silica polymorph 
analyzed (quartz, cristobalite, or tridymite), as presented in Table 
A2-1.
    For a sample with respirable crystalline silica content less 
than the method LOD, the maximum concentration is calculated as the 
respirable crystalline silica mass equivalent to LOD divided by the 
volume of air sampled. For example, the XRD analysis as performed 
for a MNM sample, as a method LOD of 5[mu]g. If a such a sample is 
analyzed using that method and no quartz is detected and that sample 
is collected at 1.7 L/min air flow rate for 480 minutes (i.e., 8 
hours), the air sample volume would be 816 L (= 1.7 L/min * 480 
minutes), or 0.816 m\3\. The calculated maximum concentration 
associated with such sample having respirable crystalline silica 
mass below the method LOD would be 6[mu]g/m\3\ (= 5[mu]g/0.816 
m\3\). The ``half maximum concentration'' is the midpoint between 0 
and the calculated maximum respirable crystalline silica 
concentration, which is 3[mu]g/m\3\ (= \1/2\ * 6[mu]g/m\3\) in this 
example.
BILLING CODE 4520-43-P

[[Page 28437]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.206

BILLING CODE 4520-43-C
    The air volume is treated differently for MNM and coal samples 
under the existing standards. In the case of MNM samples, 8-hour 
equivalent time weighted averages (TWAs) are calculated using 480 
minutes (8 hours) and a flow rate of 1.7 L/min, even if samples are 
collected for a longer duration. In contrast, coal TWAs are 
calculated using the full duration of the shift and a flow rate of 
2.0 L/min and converted to an MRE equivalent concentration under 
existing standards.

Assumptions for Analyzed Samples

    Samples from MNM mines that contain at least 0.100 mg of dust 
mass are analyzed for the presence of quartz and/or cristobalite. 
For samples from coal mines, the minimum amount of respirable dust 
for a sample to be analyzed for respirable crystalline silica is 
determined by sample type and the occupation of the miner sampled. 
For Sample Types 1, 2, and 5, the sample must contain at least 0.100 
mg of respirable dust. For Sample Types 4 and 8, the sample must 
contain at least 0.200 mg of respirable dust unless it comes from 
one of the following occupations: bulldozer operator (MSIS general 
occupation code 368), high wall drill operator (code 384), high wall 
drill helper (code 383), blaster/shotfirer (code 307), refuse/
backfill truck driver (code 386), and high lift operator/front end 
loader (code 382). Samples taken from these occupations must contain 
at least 0.100 mg respirable dust to be analyzed for respirable 
crystalline silica.
    MSHA makes separate assumptions based on the mass of respirable 
crystalline silica for a sample, whether it is above or below the 
method LOD. For all samples reporting a mass of respirable 
crystalline silica greater or equal to the method LOD, MSHA used the 
reported values to calculate the respirable crystalline silica 
concentration for the sample. For samples with values below the 
method LOD, including samples reported as containing 0 [mu]g of 
silica, MSHA used \1/2\ of the LOD to calculate the respirable 
crystalline silica concentration of the sample. MSHA understands 
that its assumptions regarding samples with respirable crystalline 
silica mass below the method LOD will have a minimal impact on the 
assessment.\129\
---------------------------------------------------------------------------

    \129\ In its Final Regulatory Economic Analysis (FREA) for its 
2016 silica rule, OSHA observed: `` . . . that XRD analysis of 
quartz from samples prepared from reference materials can achieve 
LODs and LOQs between 5 and 10 [mu]g was not disputed in the 
[rulemaking] record.'' (OSHA, 2016).

---------------------------------------------------------------------------

[[Page 28438]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.207

    The reported value of respirable crystalline silica mass from an 
MNM or coal sample can fall under one of four groups: (1) at or 
above the method LOQ, (2) at or above the method LOD but below the 
LOQ, (3) greater than 0 [mu]g but less than the method LOD, or (4) 
equal to 0 [micro]g. MSHA treats these samples differently based on 
their respirable crystalline silica mass.

Quartz Mass at or Above the Method LOQ

    For MNM and coal samples reporting quartz mass at or above the 
method LOQs, MSHA uses the values reported by the MSHA's Laboratory.

Quartz Mass Between Method LOD and LOQ

    For MNM and coal samples reporting quartz mass at or above the 
method LOD but below the LOQ, MSHA uses the values reported by the 
MSHA's Laboratory.

Quartz Mass Between the Method LOD and 0 [mu]g

    A review of respirable crystalline silica samples in LIMS 
reveals that some samples had a respirable crystalline silica mass 
below the LOD of the analytical methods but greater than 0 [mu]g. 
Values in this range (i.e., below the method LOD but greater than 0 
[mu]g) cannot reliably indicate the presence of respirable 
crystalline silica. The mass of silica in these is too small to 
reliably detect, but the concentration of silica could be up to the 
calculated maximum concentration based on the method LOD. For 
example, consider a sample from an MNM mine that was analyzed for 
quartz and had a reported quartz mass of 4 [mu]g. This falls below 
the LOD of 5 [mu]g but above 0 [mu]g, and as such the sample could 
actually contain anywhere from 0 [mu]g of quartz up to the LOD value 
of 5 [mu]g of quartz.
    In these cases, MSHA used \1/2\ the LOD value to calculate 
respirable crystalline silica concentration. MSHA explored other 
options to treat these samples such as treating the reported silica 
mass as 0 [mu]g/m\3\ (lower bound) as well as assuming the sample 
silica mass is just below the LOD and assigning each sample a value 
of the method LOD (upper bound). The use of the \1/2\ LOD value is 
considered a reasonable assumption since using either the lower 
bound of 0 [mu]g/m\3\ or the upper bound of the associated method's 
LOD could under or overestimate exposures, respectively. The 
assumption is not expected to impact the assessment of silica 
concentration because any sample results with respirable crystalline 
silica mass below the method LODs (between 3-10 [mu]g/m\3\) would 
also have been well below the lowest exposure profile range (<25 
[mu]g/m\3\).

Quartz Mass of 0 [mu]g

    A portion of the MNM and coal samples below the LOD are listed 
as having respirable crystalline silica (specifically quartz) mass 
levels of 0 [mu]g. For these samples, instead of treating the mass 
of silica in the sample as a true zero, MSHA replaced the value with 
\1/2\ the LOD of the associated method. Although the respirable 
crystalline silica mass of these samples is less than the LOD, it is 
likely that the sample still contains a small amount of respirable 
crystalline silica. Hence, MSHA assumes a value of \1/2\ LOD in its 
calculation of respirable crystalline silica concentration for these 
samples. This assumption is considered to be reasonable because 
using the lower bound of 0 [mu]g/m\3\ for these samples could 
underestimate the respirable crystalline silica concentration while 
using the upper bound of method LODs could overestimate the 
respirable crystalline silica concentration.
    Table A2-3 presents an example for quartz, one of the respirable 
crystalline silica polymorphs. This table shows the LOD of quartz 
mass and the possible range of quartz concentrations for samples 
reporting a quartz mass of 0 [mu]g. These adjusted concentrations 
are expected to have a limited impact of the assessment of 
respirable crystalline silica concentration, as supported by MSHA's 
sensitivity analyses.

[[Page 28439]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.208

Cristobalite Measurement

    Respirable dust samples from MNM mines are rarely analyzed for 
cristobalite by MSHA, and respirable coal dust samples are not 
analyzed for the presence of cristobalite. MNM samples are analyzed 
for the presence of cristobalite only when requested by MSHA 
inspectors because the geological or work conditions indicate this 
specific polymorph may be present. The LIMS database includes 
samples for which cristobalite was analyzed, either with or without 
quartz analysis. MSHA uses similar assumptions for cristobalite and 
quartz.
    The cristobalite LOD for these samples is 10 [mu]g. The MSHA 
Laboratory-reported values are used for analyzed dust samples with 
cristobalite mass values equal to or above the method LODs. Samples 
that were analyzed for cristobalite and had a cristobalite mass 
value below the method LOD were assigned values of \1/2\ LOD, or 5 
[mu]g. For example, 267 samples, or 74.4 percent of the 359 samples 
that were analyzed for cristobalite, reported a value of 0 [mu]g of 
cristobalite; these were assigned a value of 5 [mu]g.
    When a sample is analyzed for two polymorphs (i.e., both quartz 
and cristobalite), detectable quartz and cristobalite are summed to 
generate the total respirable crystalline silica. If only one of 
these polymorphs is detected, the sample concentration is based on 
the detected polymorph. If the concentrations of both polymorphs 
(quartz and cristobalite) are reported as 0 [mu]g/m\3\, \1/2\ the 
LOD mass is assumed in calculating the concentrations and the 
resulting concentrations are summed.

Unanalyzed Samples

    There are also samples whose dust mass fell below their 
associated mass threshold, and as such, they were not analyzed for 
the presence of quartz and/or cristobalite. The respirable dust mass 
for a sample was considered to be 0 [mu]g when the net mass gain of 
dust was 0 [mu]g or less.

References

MSHA. 2018. P-2: X-Ray Diffraction Determination of Quartz and 
Cristobalite in Respirable Metal/Nonmetal Mine Dust.
MSHA. 2018a. P-7: Infrared Determination of Quartz in Respirable 
Coal Mine Dust.
MSHA. 2020b. P-7: Determination of Quartz in Respirable Coal Mine 
Dust by Fourier Transform Infrared Spectroscopy.
OSHA, 2016. Final Regulatory Economic Analysis (FEA) for OSHA's 
Final Rule on Respirable Crystalline Silica, Chapter IV.3.2.3--
Sensitivity of Sampling and Analytical Methods.

Appendix B--Mining Commodity Groups

    For this final rule, the mining industries are grouped into six 
commodities--Coal, Metal, Nonmetal, Stone, Crushed Limestone, and 
Sand and Gravel. The table below shows the six commodity groupings 
based on the Standard Industrial Classification (SIC) codes and the 
2022 North American Industry Classification System (NAICS) codes. 
The SIC system is a predecessor of NAICS using industry titles to 
standardize industry classification. The NAICS is widely used by 
Federal statistical agencies, including the Small Business 
Administration (SBA), for classifying business establishments for 
the purpose of collecting, analyzing, and publishing statistical 
data related to the U.S. business economy.
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[[Page 28441]]


[GRAPHIC] [TIFF OMITTED] TR18AP24.210


[[Page 28442]]


BILLING CODE 4520-43-C

Appendix C--Occupational Categories for Respirable Crystalline Silica 
Sample Collection

    This Appendix explains how MSHA categorized MNM and coal samples 
in constructing respirable crystalline silica exposure profile 
tables for the final rule. MSHA developed respirable crystalline 
silica exposure profile tables using its inspectors' sampling 
results. One set of exposure profile tables displays the analysis of 
15 years of respirable crystalline silica sampling data collected 
from MNM mines (Attachment 1), and the other set displays the 
analysis of 5 years of respirable crystalline silica samples 
collected from coal mines (Attachment 2).\130\ In the MNM tables, 
the respirable crystalline silica concentration information is 
broken out by 5 commodities (e.g., ``Metal,'' ``Crushed Limestone,'' 
etc.) and then by 11 occupational categories (e.g., ``Drillers,'' 
``Stone Cutting Operators,'' etc.). The data for coal mining is 
disaggregated by 2 locations (``Underground'' and ``Surface'') and 
then by 9 occupational categories (e.g., ``Crusher Operators,'' 
``Continuous Mining Machine Operators,'' etc.).
---------------------------------------------------------------------------

    \130\ For coal mines, the analysis is based on samples collected 
by inspectors beginning on August 1, 2016, when Phase III of MSHA's 
2014 RCMD standard went into effect. Samples taken prior to 
implementation of the RCMD standard would not be representative of 
current respirable crystalline silica exposure levels in coal mines.
---------------------------------------------------------------------------

Job Codes and Respirable Dust Sampling

    MSHA inspectors use job codes to label samples of respirable 
dust when they conduct health inspections.\131\ Following the 
sampling strategy outlined in the most recent MSHA Health Inspection 
Procedures Handbook (December 2020; PH20-V-4), the inspectors 
determine potential airborne contaminants to which miners may be 
exposed, including respirable dust, and then take samples from the 
appropriate miners or working areas at a mine. Using gravimetric 
samplers, the inspectors collect respirable dust samples at MNM and 
coal mines. When submitting the collected samples to MSHA's 
Laboratory for analysis, the inspectors label their samples with the 
three-digit job code that best describes the duties that each miner 
was performing during the sampling period.
---------------------------------------------------------------------------

    \131\ The job codes have been referred to as both job codes and 
occupation codes by MSHA. For example, in the Mine Data Retrieval 
System, they are called job codes; in other materials, including 
MSHA's Inspection Application System (IAS), they are called 
occupational codes. For the purposes of this document, the term job 
code has been used to clearly differentiate the job codes from the 
occupational categories.
---------------------------------------------------------------------------

    The three-digit job codes are taken from MSHA's Inspection 
Application System (IAS), which includes 220 job codes for coal 
mines and 121 job codes for MNM mines. Attachments 3 and 4 list the 
complete list of IAS job codes for coal and MNM operations, 
respectively.
    Coal Job Codes: The coal job codes have generally been 
consistent over time, with new codes added when needed. In the 
three-digit coal job code, the first digit generally identifies 
where the work is taking place in the mine: 0 (Underground Section 
Workers--Face); 1 (General Underground--Non-Face); 2 (Underground 
Transportation--Non-Face); 3 (Surface); 4 (Supervisory and Staff); 5 
(MSHA--State); and 6 (Shaft and Slope Sinking). The coal codes 
starting with 6 were added in 2020 to better delineate the samples 
for miners conducting shaft and slope sinking activities. An example 
is presented below in Table C-1. IAS has the same job code for the 
duties of a coal ``supervisor/foreman'' as two predecessor 
documents--the ``Job Code Pocket Cards'' for coal mining, used by 
MSHA's predecessor, the Mining Enforcement and Safety Administration 
(MESA) (see Attachment 5), and a Fall 1983 Mine Safety and Health 
publication.
[GRAPHIC] [TIFF OMITTED] TR18AP24.211

    MNM Job Codes: Many of the 121 MNM job codes are similar to the 
coal job codes, as noted in Attachment 4. One major difference is 
that unlike the coal job codes, MNM job codes are not based on the 
location of the work/job. The first digit of the three-digit MNM job 
code does not indicate whether a job is located at an underground or 
surface area of the mine. For example, a ``MNM Diamond Drill 
Operator'' (Job Code 034) could be working on the surface or 
underground, whereas a ``Coal Drill Operator'' would have a 
different job code based on the miner's location within a mine (Job 
Code 034--underground at the face; Job Code 334--at the surface).

Occupational Categories for the Respirable Crystalline Silica 
Rulemaking

    Some of the original work to group the MNM job codes into 
occupational categories was completed in 2010 in support of earlier 
rulemaking efforts. The MNM occupational categories were developed 
first and were later updated with additional sampling data as it 
became available. The coal occupational categories were developed 
several years later and were generally modeled after the MNM tables; 
however, coal occupational categories are first divided based on 
surface and underground locations because occupational activities at 
different locations of a mine can have differing impacts on coal 
miners' exposures to respirable crystalline silica. Originally, MSHA 
used 9 coal and 14 MNM occupational categories for its respirable 
crystalline silica data analyses.
    For the respirable crystalline silica exposure profile tables in 
the proposed

[[Page 28443]]

respirable crystalline silica rule, MSHA made no change to the 9 
coal occupational categories, but condensed the 14 MNM occupational 
categories to 11. These occupational categories are meant to 
reasonably group multiple job codes with similar occupational 
activities/tasks and engineering controls. The grouping of job codes 
into occupational categories purposely focused on the occupational 
activities/tasks and exposure risk of the miner performing a 
particular job rather than the type of mining equipment utilized by 
the miner. The creation of occupational categories based on the 
types of equipment utilized by miners would have failed to 
accurately characterize the risk of individual miners.

Coal Occupational Categories

    There are 220 job codes for coal miners in IAS.\132\ Overall, 
209 job codes are included in the 9 occupational categories. Some 
job codes were excluded, primarily because sampling data were not 
available for those job codes. The codes that have been excluded 
are:
---------------------------------------------------------------------------

    \132\ IAS also contains 272 coal job codes that are used to fill 
out a Mine Accident, Injury and Illness Report (MSHA Form 7000-1). 
These codes were not included in the respirable crystalline silica 
exposure profile tables and are not discussed further in this 
document.
---------------------------------------------------------------------------

     Job code 0 ``Area,'' because area samples are not 
specific to any one occupation.
     Job code 398 ``Groundman,'' because there were no 
sample data for this code in the respirable crystalline silica 
sampling dataset.
     Job codes 590 ``Education Specialist,'' 591 ``Mineral 
Industrial Safety Officer,'' 592 ``Mine Safety Instructor,'' and 594 
``Training Specialist,'' because there were no coal respirable 
crystalline silica (quartz) data for these codes for the timeframe 
selected.
     Job codes 602 ``Electrician,'' 604 ``Mechanic,'' 609 
``Supply Person,'' 632 ``Ventilation Worker,'' and 635 ``Continuous 
Miner Operator Helper,'' because there were no sample data for these 
codes in the respirable crystalline silica sampling dataset.
    The remaining 209 coal job codes are first divided by the job 
location--underground or surface--because potential respirable 
crystalline silica exposures at coal mines can vary depending on 
where a miner works at a given mine. (Three job codes are used in 
both underground and surface locations: job codes 402 ``Master 
Electrician,'' 404 ``Master Mechanic,'' and 497 ``Clerk/
Timekeeper.'') The underground and surface job codes are further 
grouped on the basis of the types of tasks and typical engineering 
controls. For example, as shown in Figure C-1, the underground 
``Continuous Mining Machine Operators'' occupational category 
includes 14 different occupations that involve drilling activities--
occupations such as ``Coal Drill Helper,'' ``Coal Drill Operator,'' 
and ``Rock Driller.'' The underground ``Operators of Large Powered 
Haulage Equipment'' occupational category has 12 similar occupations 
including ``Loading Machine Operator,'' ``Shuttle Car Operator,'' 
and ``Motorman.''

Figure C-1: Examples of the Grouping of Coal Job Codes Into Coal 
Occupational Categories
[GRAPHIC] [TIFF OMITTED] TR18AP24.085

    There are five categories of underground occupations and four 
categories of surface occupations.
    The five underground occupational categories include:
    (1) Continuous Mining Machine Operators (e.g., Coal Drill Helper 
and Coal Drill Operator);
    (2) Operators of Large Powered Haulage Equipment (e.g., Shuttle 
Car, Tractor, Scoop Car);
    (3) Longwall Workers (e.g., Headgate Operator and Jack Setter 
(Longwall));
    (4) Roof Bolters (e.g., Roof Bolter and Roof Bolter Helper); and
    (5) Underground Miners (e.g., Electrician, Mechanic, Belt Man/
Conveyor Man, and Laborer, etc.).
    The four surface occupational categories include:
    (1) Drillers (e.g., Coal Drill Operator, Coal Drill Helper, and 
Auger Operator);
    (2) Operators of Large Powered Haulage Equipment (e.g., Backhoe, 
Forklift, and Shuttle Car);
    (3) Crusher Operators (e.g., Crusher Attendant, Washer Operator, 
and Scalper-Screen Operator); and
    (4) Mobile Workers (e.g., Electrician, Mechanic, Blaster, 
Cleanup Man, Mine Foreman, etc.).
    Attachments 1 and 3 provide the full lists of occupational 
categories and coal job codes.

MNM Occupational Categories

    From the 121 MNM job codes in IAS, 120 job codes are included in 
the occupational categories and 1 job code is excluded. The code 
that has been excluded is:
     Job code 413 ``Janitor,'' because there were no sample 
data for this code in the respirable crystalline silica sampling 
dataset.
    Of the 120 job codes included, 1 job code was listed in both the 
``Crushing Equipment and Plant Operators'' occupational category and 
the ``Kiln, Mill and Concentrator Workers'' category. The code that 
was used twice is:
     Job Code 388 ``Screen/Scalper Operators,'' because MNM 
job codes do not indicate the location where the work is taking 
place and this work can be conducted either in a plant or on the 
surface of the mine.
    The final 121 MNM job codes (with job code 388 included twice) 
were first grouped into 14 occupational categories based on the 
types of tasks and typical engineering controls used. For example, 
as seen in Figure C-2, the ``Drillers'' occupational category 
includes the 20 different occupations that involve drilling 
activities, such as ``Diamond Drill Operator,'' ``Drill Operator 
Churn,'' and ``Continuous Miner Operator.'' ``Belt Cleaner,'' ``Belt 
Crew,'' and ``Belt Vulcanizer'' are included in the occupational 
category, ``Conveyor Operators.'' Similar tasks were grouped 
together because the work activities and respirable crystalline 
silica exposures were anticipated to be comparable.

Figure C-2: Examples of the Grouping of MNM Job Codes Into MNM 
Occupational Categories

[[Page 28444]]

[GRAPHIC] [TIFF OMITTED] TR18AP24.086

    The 14 occupational categories were:
    (1) Bagging Machines;
    (2) Stone Saws;
    (3) Stone Trimmers, Splitters;
    (4) Truck Loading Stations;
    (5) Mobile Workers (e.g., Laborers, Electricians, Mechanics, and 
Supervisors);
    (6) Conveyors;
    (7) Crushers;
    (8) Dry Screening Plants;
    (9) Kilns/Dryers, Rotary Mills, Ball Mills, and Flotation/
Concentrators;
    (10) Large Powered Haulage Equipment (e.g., Trucks, FELs, 
Bulldozers, and Scalers);
    (11) Small Powered Haulage Equipment (e.g., Bobcats and 
Forklifts);
    (12) Jackhammers;
    (13) Drills; and
    (14) Other Occupations.
    After additional consideration, it was determined that the 
original 14 categories could be further condensed into the final 11 
categories since some of the occupational categories contained job 
codes where the types of tasks and engineering and administrative 
controls were similar enough to be combined.
    The final 11 occupational categories include:
    (1) Drillers (e.g., Diamond Drill Operator, Wagon Drill 
Operator, and Drill Helper);
    (2) Stone Cutting Operators (e.g., Jackhammer Operator, Cutting 
Machine Operator, and Cutting Machine Helper);
    (3) Operators of Large Powered Haulage Equipment (e.g., Trucks, 
Bulldozers, and Scalers);
    (4) Conveyor Operators (e.g., Belt Cleaner, Belt Crew, and Belt 
Vulcanizer);
    (5) Crushing Equipment and Plant Operators (Crusher Operator/
Worker, Scalper Screen Operator, and Dry Screen Plant Operator);
    (6) Kiln, Mill, and Concentrator Workers (e.g., Ball Mill 
Operator, Leaching Operator, and Pelletizer Operator);
    (7) Operators of Small Powered Haulage Equipment (e.g., Bobcats, 
Shuttle Car, and Forklifts);
    (8) Packaging Equipment Operators (e.g., Bagging Operator and 
Packaging Operations Worker);
    (9) Truck Loading Station Tenders (e.g., Dump Operator and Truck 
Loader);
    (10) Mobile Workers (Laborers, Electricians, Mechanics, and 
Supervisors, etc.); and
    (11) Miners in Other Occupations (Welder, Dragline Operator, 
Shotcrete/Gunite Man, and Dredge/Barge Operator, etc.).
    The sampling data for each of the 11 occupational categories 
were then summarized by commodity group (``Metal,'' ``Nonmetal,'' 
``Stone,'' ``Crushed Limestone,'' and ``Sand and Gravel'') based on 
the material being extracted.\133\ The available sampling data were 
then collated for each occupation and commodity and summarized by 
concentration ranges in the exposure profile tables for MNM mines.
---------------------------------------------------------------------------

    \133\ Crushed Limestone and Sand and Gravel were considered 
separately because these commodities make up a large percentage of 
inspection samples. Watts et al. (2012). Respirable crystalline 
silica [Quartz] Concentration Trends in Metal and Nonmetal Mining, J 
Occ Environ Hyg 9:12, 720-732.
---------------------------------------------------------------------------

BILLING CODE 4520-43-P

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BILLING CODE 4520-43-C

List of Subjects

30 CFR Part 56

    Chemicals, Electric power, Explosives, Fire prevention, Hazardous 
substances, Incorporation by reference, Metal and nonmetal mining, Mine 
safety and health, Noise control, Reporting and recordkeeping 
requirements, Surface mining.

30 CFR Part 57

    Chemicals, Electric power, Explosives, Fire prevention, Gases, 
Hazardous substances, Incorporation by reference, Metal and nonmetal 
mining, Mine safety and health, Noise control, Radiation protection, 
Reporting and recordkeeping requirements, Underground mining.

30 CFR Part 60

    Coal, Incorporation by reference, Metal and nonmetal mining, 
Medical surveillance, Mine safety and health, Respirable crystalline 
silica, Reporting and recordkeeping requirements, Surface mining, 
Underground mining.

30 CFR Part 70

    Coal, Mine safety and health, Reporting and recordkeeping 
requirements, Respirable dust, Underground coal mines.

30 CFR Part 71

    Coal, Mine safety and health, Reporting and recordkeeping 
requirements, Surface coal mines, Underground coal mines.

30 CFR Part 72

    Coal, Health standards, Incorporation by reference, Mine safety and 
health, Training, Underground mining.

30 CFR Part 75

    Coal, Mine safety and health, Reporting and recordkeeping 
requirements, Underground coal mines, Ventilation.

30 CFR Part 90

    Coal, Mine safety and health, Reporting and recordkeeping 
requirements, Respirable dust.

Christopher J. Williamson,
Assistant Secretary of Labor for Mine Safety and Health.

    For the reasons discussed in the preamble, the Mine Safety and 
Health Administration is amending 30 CFR subchapters K, M, and O as 
follows:

Subchapter K--Metal and Nonmetal Mine Safety and Health

PART 56--SAFETY AND HEALTH STANDARDS--SURFACE METAL AND NONMETAL 
MINES

0
1. The authority citation for part 56 continues to read as follows:

    Authority:  30 U.S.C. 811.

Subpart D--Air Quality and Physical Agents

0
2. Amend Sec.  56.5001 by revising the introductory text to read as 
follows:


Sec.  56.5001  Exposure limits for airborne contaminants.

    The following is required until April 7, 2026. Except as permitted 
by Sec.  56.5005--
* * * * *

0
3. Add Sec.  56.5001T to read as follows:


Sec.  56.5001T  Exposure limits for airborne contaminants.

    As of April 8, 2026 the following is required, except as permitted 
by Sec.  56.5005--
    (a) TLVs standard. Except as provided in paragraph (b) of this 
section and in part 60 of this chapter, the exposure to airborne 
contaminants shall not exceed, on the basis of a time weighted average, 
the threshold limit values adopted by the American Conference of 
Governmental Industrial Hygienists, as set forth and explained in the 
1973 edition of the Conference's publication, entitled TLV's Threshold 
Limit Values for Chemical Substances in Workroom Air Adopted by ACGIH 
for 1973, pages 1 through 54. This publication is incorporated by 
reference into this section with the approval of the Director of the 
Federal Register under 5 U.S.C. 552(a) and 1 CFR part 51. This 
incorporation by reference (IBR) material is available for inspection 
at the Mine Safety and Health Administration (MSHA) and at the National 
Archives and Records Administration (NARA). Contact MSHA at: MSHA's 
Office of Standards, Regulations, and Variances, 201 12th Street South, 
Arlington, VA 22202-5450; (202) 693-9440; or at any Mine Safety and 
Health Enforcement District Office. For information on the availability 
of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected]. The material may be 
obtained from American Conference of Governmental Industrial 
Hygienists, 1330 Kemper Meadow Drive, Attn: Customer Service, 
Cincinnati, OH 45240; www.acgih.org.
    (b) Asbestos standard--(1) Definitions. Asbestos is a generic term 
for a number of asbestiform hydrated silicates that, when crushed or 
processed, separate into flexible fibers made up of fibrils.
    Asbestos means chrysotile, cummingtonite-grunerite asbestos 
(amosite), crocidolite, anthophylite

[[Page 28469]]

asbestos, tremolite asbestos, and actinolite asbestos.
    Asbestos fiber means a fiber of asbestos that meets the criteria of 
a fiber.
    Fiber means a particle longer than 5 micrometers ([micro]m) with a 
length-to-diameter ratio of at least 3-to-1.
    (2) Permissible Exposure Limits (PELs)--(i) Full-shift limit. A 
miner's personal exposure to asbestos shall not exceed an 8-hour time-
weighted average full-shift airborne concentration of 0.1 fiber per 
cubic centimeter of air (f/cc).
    (ii) Excursion limit. No miner shall be exposed at any time to 
airborne concentrations of asbestos in excess of 1 fiber per cubic 
centimeter of air (f/cc) as averaged over a sampling period of 30 
minutes.
    (3) Measurement of airborne asbestos fiber concentration. Potential 
asbestos fiber concentration shall be determined by phase contrast 
microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos 
standard found in 29 CFR 1910.1001, Appendix A, or a method at least 
equivalent to that method in identifying a potential asbestos exposure 
exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. 
When PCM results indicate a potential exposure exceeding the 0.1 f/cc 
full-shift limit or the 1 f/cc excursion limit, samples shall be 
further analyzed using transmission electron microscopy according to 
NIOSH Method 7402 or a method at least equivalent to that method.
    (c) Required action. Employees shall be withdrawn from areas where 
there is present an airborne contaminant given a ``C'' designation by 
the Conference and the concentration exceeds the threshold limit value 
listed for that contaminant.


Sec.  56.5001  [Removed]

0
4. Effective April 8, 2026, remove Sec.  56.5001.


Sec.  56.5001T  [Redesignated as Sec.  56.5001]

0
5. Effective April 8, 2026, redesignate Sec.  56.5001T as Sec.  
56.5001.

0
6. Amend Sec.  56.5005 by revising the introductory text to read as 
follows:


Sec.  56.5005  Control of exposure to airborne contaminants.

    The following is required until April 7, 2026. Control of employee 
exposure to harmful airborne contaminants shall be, insofar as 
feasible, by prevention of contamination, removal by exhaust 
ventilation, or by dilution with uncontaminated air. However, where 
accepted, engineering control measures have not been developed or when 
necessary by the nature of work involved (for example, while 
establishing controls or occasional entry into hazardous atmospheres to 
perform maintenance or investigation), employees may work for 
reasonable periods of time in concentrations of airborne contaminants 
exceeding permissible levels if they are protected by appropriate 
respiratory protective equipment. Whenever respiratory protective 
equipment is used a program for selection, maintenance, training, 
fitting, supervision, cleaning, and use shall meet the following 
minimum requirements:
* * * * *

0
7. Add Sec.  56.5005T to read as follows:


Sec.  56.5005T  Control of exposure to airborne contaminants.

    As of April 8, 2026, the following is required. Control of employee 
exposure to harmful airborne contaminants shall be, insofar as 
feasible, by prevention of contamination, removal by exhaust 
ventilation, or by dilution with uncontaminated air. However, where 
accepted engineering control measures have not been developed or when 
necessary by the nature of work involved (for example, while 
establishing controls or occasional entry into hazardous atmospheres to 
perform maintenance or investigation), employees may work for 
reasonable periods of time in concentrations of airborne contaminants 
exceeding permissible levels if they are protected by appropriate 
respiratory protective equipment. Whenever respiratory protective 
equipment is used, its selection, fitting, maintenance, cleaning, 
training, supervision, and use shall meet the following minimum 
requirements:
    (a) Respirators approved by NIOSH under 42 CFR part 84 which are 
applicable and suitable for the purpose intended shall be furnished and 
miners shall use the protective equipment in accordance with training 
and instruction.
    (b) A written respiratory protection program consistent with the 
requirements of ASTM F3387-19, Standard Practice for Respiratory 
Protection, approved August 1, 2019, which is incorporated by reference 
into this section with the approval of the Director of the Federal 
Register under 5 U.S.C. 552(a) and 1 CFR part 51. This incorporation by 
reference (IBR) material is available for inspection at the Mine Safety 
and Health Administration (MSHA) and at the National Archives and 
Records Administration (NARA). Contact MSHA at: MSHA's Office of 
Standards, Regulations, and Variances, 201 12th Street South, 
Arlington, VA 22202-5450; (202) 693-9440; or any Mine Safety and Health 
Enforcement District Office. For information on the availability of 
this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected]. The material may be obtained 
from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959; www.astm.org.
    (c) When respiratory protection is used in atmospheres immediately 
dangerous to life or health (IDLH), the presence of at least one other 
person with backup equipment and rescue capability shall be required in 
the event of failure of the respiratory equipment.


Sec.  56.5005  [Removed]

0
8. Effective April 8, 2026, remove Sec.  56.5005.


Sec.  56.5005T  [Redesignated as Sec.  56.5005]

0
9. Effective April 8, 2026, redesignate Sec.  56.5005T as Sec.  
56.5005.

PART 57--SAFETY AND HEALTH STANDARDS--UNDERGROUND METAL AND 
NONMETAL MINES

0
10. The authority citation for part 57 continues to read as follows:

    Authority:  30 U.S.C. 811.

Subpart D--Air Quality, Radiation, Physical Agents, and Diesel 
Particulate Matter

0
11. Amend Sec.  57.5001 by revising the introductory text to read as 
follows:


Sec.  57.5001  Exposure limits for airborne contaminants.

    The following is required until April 7, 2026. Except as permitted 
by Sec.  57.5005--
* * * * *

0
12. Add Sec.  57.5001T to read as follows:


Sec.  57.5001T  Exposure limits for airborne contaminants.

    As of April 8, 2026, except as permitted by Sec.  57.5005--
    (a) TLVs standard. Except as provided in paragraph (b) of this 
section and in part 60 of this chapter, the exposure to airborne 
contaminants shall not exceed, on the basis of a time weighted average, 
the threshold limit values adopted by the American Conference of 
Governmental Industrial Hygienists, as set forth and explained in the 
1973 edition of the Conference's publication, entitled TLV's Threshold 
Limit Values for Chemical Substances in Workroom Air Adopted by ACGIH 
for 1973, pages 1 through 54. This publication is incorporated by 
reference into this section with the approval of the Director of the 
Federal Register under 5 U.S.C.

[[Page 28470]]

552(a) and 1 CFR part 51. This incorporation by reference (IBR) 
material is available for inspection at the Mine Safety and Health 
Administration (MSHA) and at the National Archives and Records 
Administration (NARA). Contact MSHA at: MSHA's Office of Standards, 
Regulations, and Variances, 201 12th Street South, Arlington, VA 22202-
5450; (202) 693-9440; or at any Mine Safety and Health Enforcement 
District Office. For information on the availability of this material 
at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or 
email [email protected]. The material may be obtained from 
American Conference of Governmental Industrial Hygienists, 1330 Kemper 
Meadow Drive, Attn: Customer Service, Cincinnati, OH 45240; 
www.acgih.org.
    (b) Asbestos standard--(1) Definitions. Asbestos is a generic term 
for a number of asbestiform hydrated silicates that, when crushed or 
processed, separate into flexible fibers made up of fibrils.
    Asbestos means chrysotile, cummingtonite-grunerite asbestos 
(amosite), crocidolite, anthophylite asbestos, tremolite asbestos, and 
actinolite asbestos.
    Asbestos fiber means a fiber of asbestos that meets the criteria of 
a fiber.
    Fiber means a particle longer than 5 micrometers ([micro]m) with a 
length-to-diameter ratio of at least 3-to-1.
    (2) Permissible Exposure Limits (PELs)--(i) Full-shift limit. A 
miner's personal exposure to asbestos shall not exceed an 8-hour time-
weighted average full-shift airborne concentration of 0.1 fiber per 
cubic centimeter of air (f/cc).
    (ii) Excursion limit. No miner shall be exposed at any time to 
airborne concentrations of asbestos in excess of 1 fiber per cubic 
centimeter of air (f/cc) as averaged over a sampling period of 30 
minutes.
    (3) Measurement of airborne asbestos fiber concentration. Potential 
asbestos fiber concentration shall be determined by phase contrast 
microscopy (PCM) using the OSHA Reference Method in OSHA's asbestos 
standard found in 29 CFR 1910.1001, Appendix A, or a method at least 
equivalent to that method in identifying a potential asbestos exposure 
exceeding the 0.1 f/cc full-shift limit or the 1 f/cc excursion limit. 
When PCM results indicate a potential exposure exceeding the 0.1 f/cc 
full-shift limit or the 1 f/cc excursion limit, samples shall be 
further analyzed using transmission electron microscopy according to 
NIOSH Method 7402 or a method at least equivalent to that method.
    (c) Required action. Employees shall be withdrawn from areas where 
there is present an airborne contaminant given a ``C'' designation by 
the Conference and the concentration exceeds the threshold limit value 
listed for that contaminant.


Sec.  57.5001  [Removed]

0
13. April 8, 2026, remove Sec.  57.5001.


Sec.  57.5001T  [Redesignated as Sec.  57.5001]

0
14. Effective April 8, 2026, redesignate Sec.  57.5001T as Sec.  
57.5001.

0
15. Amend Sec.  57.5005 by revising the introductory text to read as 
follows:


Sec.  57.5005  Control of exposure to for airborne contaminants.

    The following is required until April 7, 2026. Control of employee 
exposure to harmful airborne contaminants shall be, insofar as 
feasible, by prevention of contamination, removal by exhaust 
ventilation, or by dilution with uncontaminated air. However, where 
accepted engineering control measures have not been developed or when 
necessary by the nature of work involved (for example, while 
establishing controls or occasional entry into hazardous atmospheres to 
perform maintenance or investigation), employees may work for 
reasonable periods of time in concentrations of airborne contaminants 
exceeding permissible levels if they are protected by appropriate 
respiratory protective equipment. Whenever respiratory protective 
equipment is used a program for selection, maintenance, training, 
fitting, supervision, cleaning, and use shall meet the following 
minimum requirements:
* * * * *

0
16. Add Sec.  57.5005T to read as follows:


Sec.  57.5005T  Control of exposure to airborne contaminants.

    As of April 8, 2026, the following is required. Control of employee 
exposure to harmful airborne contaminants shall be, insofar as 
feasible, by prevention of contamination, removal by exhaust 
ventilation, or by dilution with uncontaminated air. However, where 
accepted engineering control measures have not been developed or when 
necessary by the nature of work involved (for example, while 
establishing controls or occasional entry into hazardous atmospheres to 
perform maintenance or investigation), employees may work for 
reasonable periods of time in concentrations of airborne contaminants 
exceeding permissible levels if they are protected by appropriate 
respiratory protective equipment. Whenever respiratory protective 
equipment is used, its selection, fitting, maintenance, cleaning, 
training, supervision, and use shall meet the following minimum 
requirements:
    (a) Respirators approved by NIOSH under 42 CFR part 84 which are 
applicable and suitable for the purpose intended shall be furnished and 
miners shall use the protective equipment in accordance with training 
and instruction.
    (b) A written respiratory protection program consistent with the 
requirements of ASTM F3387-19, Standard Practice for Respiratory 
Protection, approved August 1, 2019, which is incorporated by reference 
into this section with the approval of the Director of the Federal 
Register under 5 U.S.C. 552(a) and 1 CFR part 51. This incorporation by 
reference (IBR) material is available for inspection at the Mine Safety 
and Health Administration (MSHA) and at the National Archives and 
Records Administration (NARA). Contact MSHA at: MSHA's Office of 
Standards, Regulations, and Variances, 201 12th Street South, 
Arlington, VA 22202-5450; (202) 693-9440; or any Mine Safety and Health 
Enforcement District Office. For information on the availability of 
this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected]. The material may be obtained 
from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959; www.astm.org.
    (c) When respiratory protection is used in atmospheres immediately 
dangerous to life or health (IDLH), the presence of at least one other 
person with backup equipment and rescue capability shall be required in 
the event of failure of the respiratory equipment.


Sec.  57.5005  [Removed]

0
17. Effective April 8, 2026, remove Sec.  57.5005.


Sec.  57.5005T  [Redesignated as Sec.  57.5005]

0
18. Effective April 8, 2026, redesignate Sec.  57.5005T as Sec.  
57.5005.

Subchapter M--Uniform Mine Health Regulations

0
19. Add part 60 to subchapter M to read as follows:

PART 60--RESPIRABLE CRYSTALLINE SILICA

Sec.
60.1 Scope; compliance dates.
60.2 Definitions.
60.10 Permissible exposure limit (PEL).
60.11 Methods of compliance.
60.12 Exposure monitoring.
60.13 Corrective actions.

[[Page 28471]]

60.14 Respiratory protection.
60.15 Medical surveillance for metal and nonmetal mines.
60.16 Recordkeeping requirements.
60.17 Severability.

    Authority:  30 U.S.C. 811, 813(h) and 957.


Sec.  60.1  Scope; compliance dates.

    (a) This part sets forth mandatory health standards for each 
surface and underground metal, nonmetal, and coal mine subject to the 
Federal Mine Safety and Health Act of 1977, as amended. Requirements 
regarding medical surveillance for metal and nonmetal mines are also 
included.
    (b) The compliance dates for the provisions of this part are as 
follows:
    (1) For coal mine operators, April 14, 2025.
    (2) For metal and nonmetal mine operators, April 8, 2026.


Sec.  60.2  Definitions.

    The following definitions apply in this part:
    Action level means an airborne concentration of respirable 
crystalline silica of 25 micrograms per cubic meter of air ([mu]g/m\3\) 
for a full-shift exposure, calculated as an 8-hour time-weighted 
average (TWA).
    Respirable crystalline silica means quartz, cristobalite, and/or 
tridymite contained in airborne particles that are determined to be 
respirable by a sampling device designed to meet the characteristics 
for respirable-particle-size-selective samplers that conform to the 
International Organization for Standardization (ISO) 7708:1995: Air 
Quality--Particle Size Fraction Definitions for Health-Related 
Sampling.
    Specialist means an American Board-Certified Specialist in 
Pulmonary Disease or an American Board-Certified Specialist in 
Occupational Medicine.


Sec.  60.10  Permissible exposure limit (PEL).

    The mine operator shall ensure that no miner is exposed to an 
airborne concentration of respirable crystalline silica in excess of 50 
[mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA.


Sec.  60.11  Methods of compliance.

    (a) The mine operator shall install, use, and maintain feasible 
engineering controls, supplemented by administrative controls when 
necessary, to keep each miner's exposure at or below the PEL, except as 
specified in Sec.  60.14.
    (b) Rotation of miners shall not be considered an acceptable 
administrative control used for compliance with this part.


Sec.  60.12  Exposure monitoring.

    (a) Sampling. (1) Mine operators shall commence sampling by the 
compliance date in Sec.  60.1 to assess the full shift, 8-hour TWA 
exposure of respirable crystalline silica for each miner who is or may 
reasonably be expected to be exposed to respirable crystalline silica.
    (2) If the sampling under paragraph (a)(1) of this section is:
    (i) Below the action level, the mine operator shall take at least 
one additional sampling within 3 months.
    (ii) At or above the action level but at or below the PEL, the mine 
operator shall take another sampling within 3 months.
    (iii) Above the PEL, the mine operator shall take corrective 
actions and sample pursuant to Sec.  60.12(b).
    (3) Where the most recent sampling indicates that miner exposures 
are at or above the action level but at or below the PEL, the mine 
operator shall continue to sample within 3 months of the previous 
sampling.
    (4) The mine operator may discontinue sampling when two consecutive 
samplings indicate that miner exposures are below the action level. The 
second of these samplings must be taken after the operator receives the 
results of the prior sampling but no sooner than 7 days after the prior 
sampling was conducted.
    (b) Corrective actions sampling. Where the most recent sampling 
indicates that miner exposures are above the PEL, the mine operator 
shall sample after corrective actions are taken pursuant to Sec.  60.13 
until the sampling indicates that miner exposures are at or below the 
PEL. The mine operator shall immediately report all operator samples 
above the PEL to the MSHA District Manager or to any other MSHA office 
designated by the District Manager.
    (c) Periodic evaluation. At least every 6 months after commencing 
sampling under 60.12(a)(1) or whenever there is a change in: 
production; processes; installation or maintenance of engineering 
controls; installation or maintenance of equipment; administrative 
controls; or geological conditions; mine operators shall evaluate 
whether the change may reasonably be expected to result in new or 
increased respirable crystalline silica exposures. Once the evaluation 
is completed, the mine operator shall:
    (1) Make a record of the evaluation, including the evaluated 
change, the impact on respirable crystalline silica exposure, and the 
date of the evaluation; and
    (2) Post the record on the mine bulletin board and, if applicable, 
by electronic means, for the next 31 days.
    (d) Post-evaluation sampling. If the mine operator determines as a 
result of the periodic evaluation under paragraph (c) of this section 
that miners may be exposed to respirable crystalline silica at or above 
the action level, the mine operator shall perform sampling to assess 
the full shift, 8-hour TWA exposure of respirable crystalline silica 
for each miner who is or may reasonably be expected to be at or above 
the action level.
    (e) Sampling requirements. (1) Sampling shall be performed for the 
duration of a miner's regular full shift and during typical mining 
activities, including shaft and slope sinking, construction, and 
removal of overburden.
    (2) The full-shift, 8-hour TWA exposure for such miners shall be 
measured based on:
    (i) Personal breathing-zone air samples for metal and nonmetal 
operations; or
    (ii) Occupational environmental samples collected in accordance 
with Sec.  70.201(c), Sec.  71.201(b), or Sec.  90.201(b) of this 
chapter for coal operations.
    (3) Where several miners perform the same tasks on the same shift 
and in the same work area, the mine operator may sample a 
representative fraction (at least two) of these miners to meet the 
requirements in paragraphs (a) through (e) of this section. In sampling 
a representative fraction of miners, the mine operator shall select the 
miners who are expected to have the highest exposure to respirable 
crystalline silica.
    (4) The mine operator shall use respirable-particle-size-selective 
samplers that conform to ISO 7708:1995(E) to determine compliance with 
the PEL. ISO 7708:1995(E), Air quality--Particle size fraction 
definitions for health-related sampling, First Edition, 1995-04-01, is 
incorporated by reference into this section with the approval of the 
Director of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 
51. This incorporation by reference (IBR) material is available for 
inspection at the Mine Safety and Health Administration (MSHA) and at 
the National Archives and Records Administration (NARA). Contact MSHA 
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th 
Street South, Arlington, VA 22202-5450; (202) 693-9440; or any Mine 
Safety and Health Enforcement District Office. For information on the 
availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected]. The 
material may be obtained from the International Organization for

[[Page 28472]]

Standardization (ISO), CP 56, CH-1211 Geneva 20, Switzerland; phone: + 
41 22 749 01 11; fax: + 41 22 733 34 30; website: www.iso.org.
    (f) Methods of sample analysis. (1) The mine operator shall use a 
laboratory that is accredited to ISO/IEC 17025 ``General requirements 
for the competence of testing and calibration laboratories'' with 
respect to respirable crystalline silica analyses, where the 
accreditation has been issued by a body that is compliant with ISO/IEC 
17011 ``Conformity assessment--Requirements for accreditation bodies 
accrediting conformity assessment bodies.''
    (2) The mine operator shall ensure that the laboratory evaluates 
all samples using respirable crystalline silica analytical methods 
specified by MSHA, the National Institute for Occupational Safety and 
Health (NIOSH), or the Occupational Safety and Health Administration 
(OSHA).
    (g) Sampling records. For each sample taken pursuant to paragraphs 
(a) through (e) of this section, the mine operator shall make a record 
of the sample date, the occupations sampled, and the concentrations of 
respirable crystalline silica and respirable dust and post the record 
and the laboratory report on the mine bulletin board and, if 
applicable, by electronic means, for the next 31 days, upon receipt.


Sec.  60.13  Corrective actions.

    (a) If any sampling indicates that a miner's exposure exceeds the 
PEL, the mine operator shall:
    (1) Make approved respirators available to affected miners before 
the start of the next work shift in accordance with Sec.  60.14(b) and 
(c);
    (2) Ensure that affected miners wear respirators properly for the 
full shift or during the period of overexposure until miner exposures 
are at or below the PEL; and
    (3) Immediately take corrective actions to lower the concentration 
of respirable crystalline silica to at or below the PEL.
    (b) Once corrective actions have been taken, the mine operator 
shall:
    (1) Conduct sampling pursuant to Sec.  60.12(b); and
    (2) Take additional or new corrective actions until sampling 
indicates miner exposures are at or below the PEL.
    (c) The mine operator shall make a record of corrective actions and 
the dates of the corrective actions under paragraph (a) of this 
section.


Sec.  60.14  Respiratory protection.

    (a) Temporary use of respirators at metal and nonmetal mines. The 
metal and nonmetal mine operator shall use respiratory protection as a 
temporary measure in accordance with paragraph (c) of this section when 
miners must work in concentrations of respirable crystalline silica 
above the PEL while:
    (1) Engineering control measures are being developed and 
implemented; or
    (2) It is necessary by the nature of work involved (for example, 
occasional entry into hazardous atmospheres to perform maintenance or 
investigation).
    (b) Miners unable to wear respirators at all mines. Upon written 
determination by a physician or other licensed health care professional 
(PLHCP) that an affected miner is unable to wear a respirator, the 
miner shall be temporarily transferred either to work in a separate 
area of the same mine or to an occupation at the same mine where 
respiratory protection is not required.
    (1) The affected miner shall continue to receive compensation at no 
less than the regular rate of pay in the occupation held by that miner 
immediately prior to the transfer.
    (2) The affected miner may be transferred back to the miner's 
initial work area or occupation when temporary use of respirators under 
paragraph (a) of this section or section 60.13 is no longer required.
    (c) Respiratory protection requirements at all mines. (1) Affected 
miners shall be provided with a NIOSH-approved atmosphere-supplying 
respirator or NIOSH-approved air-purifying respirator equipped with the 
following:
    (i) Particulate protection classified as 100 series under 42 CFR 
part 84; or
    (ii) Particulate protection classified as High Efficiency ``HE'' 
under 42 CFR part 84.
    (2) When approved respirators are used, the mine operator must have 
a written respiratory protection program that meets the following 
requirements in accordance with ASTM F3387-19: program administration; 
written standard operating procedures; medical evaluation; respirator 
selection; training; fit testing; maintenance, inspection, and storage. 
ASTM F3387-19, Standard Practice for Respiratory Protection, approved 
August 1, 2019, is incorporated by reference into this section with the 
approval of the Director of the Federal Register under 5 U.S.C. 552(a) 
and 1 CFR part 51. This incorporation by reference (IBR) material is 
available for inspection at the Mine Safety and Health Administration 
(MSHA) and at the National Archives and Records Administration (NARA). 
Contact MSHA at: MSHA's Office of Standards, Regulations, and 
Variances, 201 12th Street South, Arlington, VA 22202-5450; (202) 693-
9440; or any Mine Safety and Health Enforcement District Office. For 
information on the availability of this material at NARA, visit 
www.archives.gov/federal-register/cfr/ibr-locations or email 
[email protected]. The material may be obtained from ASTM 
International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, 
PA 19428-2959; www.astm.org.


Sec.  60.15  Medical surveillance for metal and nonmetal mines.

    (a) Medical surveillance. Each operator of a metal and nonmetal 
mine shall provide to each miner periodic medical examinations 
performed by a physician or other licensed health care professional 
(PLHCP) or specialist, as defined in Sec.  60.2, at no cost to the 
miner.
    (1) Medical examinations shall be provided at frequencies specified 
in this section.
    (2) Medical examinations shall include:
    (i) A medical and work history, with emphasis on: past and present 
exposure to respirable crystalline silica, dust, and other agents 
affecting the respiratory system; any history of respiratory system 
dysfunction, including diagnoses and symptoms of respiratory disease 
(e.g., shortness of breath, cough, wheezing); history of tuberculosis; 
and smoking status and history;
    (ii) A physical examination with special emphasis on the 
respiratory system;
    (iii) A chest X-ray (a single posteroanterior radiographic 
projection or radiograph of the chest at full inspiration recorded on 
either film (no less than 14 x 17 inches and no more than 16 x 17 
inches) or digital radiography systems), classified according to the 
International Labour Office (ILO) International Classification of 
Radiographs of Pneumoconioses by a NIOSH-certified B Reader; and
    (iv) A pulmonary function test to include forced vital capacity 
(FVC) and forced expiratory volume in one second (FEV1) and 
FEV1/FVC ratio, administered by a spirometry technician with 
a current certificate from a NIOSH-approved Spirometry Program Sponsor 
or by a pulmonary function technologist with a current credential from 
the National Board for Respiratory Care.
    (b) Voluntary medical examinations. Each mine operator shall 
provide the opportunity to all miners employed at the mine to have the 
medical examinations specified in paragraph (a) of this section as 
follows:

[[Page 28473]]

    (1) During an initial 12-month period; and
    (2) At least every 5 years after the end of the period in paragraph 
(b)(1). The medical examinations shall be available during a 6-month 
period that begins no less than 3.5 years and not more than 4.5 years 
from the end of the last 6-month period.
    (c) Mandatory medical examinations. For each miner who begins work 
in the mining industry for the first time, the mine operator shall 
provide medical examinations specified in paragraph (a) of this section 
as follows:
    (1) An initial medical examination no later than 60 days after 
beginning employment;
    (2) A follow-up medical examination no later than 3 years after the 
initial examination in paragraph (c)(1) of this section; and
    (3) A follow-up medical examination conducted by a specialist no 
later than 2 years after the examinations in paragraph (c)(2) of this 
section if the chest X-ray shows evidence of pneumoconiosis or the 
spirometry examination indicates evidence of decreased lung function.
    (d) Medical examinations results. (1) The mine operator shall 
ensure that the results of medical examinations or tests made pursuant 
to this section shall be provided from the PLHCP or specialist within 
30 days of the medical examination to the miner, and at the request of 
the miner, to the miner's designated physician or another designee 
identified by the miner.
    (2) The mine operator shall ensure that, within 30 days of the 
medical examination, the PLHCP or specialist provides the results of 
chest X-ray classifications to the National Institute for Occupational 
Safety and Health (NIOSH), once NIOSH establishes a reporting system.
    (e) Written medical opinion. The mine operator shall obtain a 
written medical opinion from the PLHCP or specialist within 30 days of 
the medical examination. The written opinion shall contain only the 
following:
    (1) The date of the medical examination;
    (2) A statement that the examination has met the requirements of 
this section; and
    (3) Any recommended limitations on the miner's use of respirators.
    (f) Written medical opinion records. The mine operator shall 
maintain a record of the written medical opinions received from the 
PLHCP or specialist under paragraph (e) of this section.


Sec.  60.16  Recordkeeping requirements.

    (a) Table 1 to this paragraph (a) lists the records the mine 
operator shall retain and their retention period.
    (1) Evaluation records made under Sec.  60.12(c) shall be retained 
for at least 5 years from the date of each evaluation.
    (2) Sampling records made under Sec.  60.12(g) shall be retained 
for at least 5 years from the sample date.
    (3) Corrective actions records made under Sec.  60.13(c) shall be 
retained for at least 5 years from the date of each corrective action. 
These records must be stored with the records of related sampling under 
Sec.  60.12(g).
    (4) Written determination records received from a PLHCP under Sec.  
60.14(b) shall be retained for the duration of the miner's employment 
plus 6 months.
    (5) Written medical opinion records received from a PLHCP or 
specialist under Sec.  60.15(f) shall be retained for the duration of 
the miner's employment plus 6 months.

          Table 1 to Paragraph (a)--Recordkeeping Requirements
------------------------------------------------------------------------
                                     Section
             Record                references        Retention period
------------------------------------------------------------------------
1. Evaluation records..........            Sec.  At least 5 years from
                                       60.12(c)   date of each
                                                  evaluation.
2. Sampling records............            Sec.  At least 5 years from
                                       60.12(g)   sample date.
3. Corrective actions records..            Sec.  At least 5 years from
                                       60.13(c)   date of each
                                                  corrective action.
4. Written determination                   Sec.  Duration of miner's
 records received from a PLHCP.        60.14(b)   employment plus 6
                                                  months.
5. Written medical opinion                 Sec.  Duration of miner's
 records received from a PLHCP         60.15(f)   employment plus 6
 or specialist.                                   months.
------------------------------------------------------------------------

    (b) Upon request from an authorized representative of the 
Secretary, from an authorized representative of miners, or from miners, 
mine operators shall promptly provide access to any record listed in 
this section.


Sec.  60.17  Severability.

    Each section of this part, as well as sections in 30 CFR parts 56, 
57, 70, 71, 72, 75, and 90 that address respirable crystalline silica 
or respiratory protection, is separate and severable from the other 
sections and provisions. If any provision of this subpart is held to be 
invalid or unenforceable by its terms, or as applied to any person, 
entity, or circumstance, or is stayed or enjoined, that provision shall 
be construed so as to continue to give the maximum effect to the 
provision permitted by law, unless such holding shall be one of utter 
invalidity or unenforceability, in which event the provision shall be 
severable from these sections and shall not affect the remainder 
thereof.

Subchapter O--Coal Mine Safety and Health

PART 70--MANDATORY HEALTH STANDARDS--UNDERGROUND COAL MINES

0
20. The authority citation for part 70 continues to read as follows:

    Authority:  30 U.S.C. 811, 813(h), 957.

Subpart A--General


Sec.  70.2  [Amended]

0
21. Effective April 14, 2025, amend Sec.  70.2 by removing the 
definition of ``Quartz''.

Subpart B--Dust Standards


Sec.  70.101  [Removed and Reserved]

0
22. Effective April 14, 2025, remove and reserve Sec.  70.101.

Subpart C--Sampling Procedures

0
23. Amend Sec.  70.205 by adding introductory text to read as follows:


Sec.  70.205  Approved sampling devices; operation; air flowrate.

    The following is required until April 14, 2025:
* * * * *

0
24. Add Sec.  70.205T to read as follows:


Sec.  70.205T  Approved sampling devices; operation; air flowrate.

    As of April 14, 2025:
    (a) Approved sampling devices shall be operated at the flowrate of 
2.0 L/min if using a CMDPSU; at 2.2 L/min if

[[Page 28474]]

using a CPDM; or at a different flowrate recommended by the 
manufacturer.
    (b) If using a CMDPSU, each approved sampling device shall be 
examined each shift by a person certified in sampling during:
    (1) The second hour after being put into operation to assure it is 
in the proper location, operating properly, and at the proper flowrate. 
If the proper flowrate is not maintained, necessary adjustments shall 
be made by the certified person. This examination is not required if 
the sampling device is being operated in an anthracite coal mine using 
the full box, open breast, or slant breast mining method.
    (2) The last hour of operation to assure that the sampling device 
is operating properly and at the proper flowrate. If the proper 
flowrate is not maintained, the respirable dust sample shall be 
transmitted to MSHA with a notation by the certified person on the back 
of the dust data card stating that the proper flowrate was not 
maintained. Other events occurring during the collection of respirable 
dust samples that may affect the validity of the sample, such as 
dropping of the sampling head assembly onto the mine floor, shall be 
noted on the back of the dust data card.
    (c) If using a CPDM, the person certified in sampling shall monitor 
the dust concentrations and the sampling status conditions being 
reported by the sampling device at mid-shift or more frequently as 
specified in the approved mine ventilation plan to assure: The sampling 
device is in the proper location and operating properly; and the work 
environment of the occupation or DA being sampled remains in compliance 
with the standard at the end of the shift. This monitoring is not 
required if the sampling device is being operated in an anthracite coal 
mine using the full box, open breast, or slant breast mining method.


Sec.  70.205  [Removed]

0
25. Effective April 14, 2025, remove Sec.  70.205.


Sec.  70.205T  [Redesignated as Sec.  70.205]

0
26. Effective April 14, 2025, redesignate Sec.  70.205T as Sec.  
70.205.


Sec. Sec.  70.206 and 70.207  [Removed and Reserved]

0
27. Effective April 14, 2025, remove and reserve Sec. Sec.  70.206 and 
70.207.

0
28. Amend Sec.  70.208 by revising the introductory text to read as 
follows:


Sec.  70.208  Quarterly sampling; mechanized mining units.

    The following is required from February 1, 2016, until April 14, 
2025:
* * * * *

0
29. Add Sec.  70.208T to read as follows:


Sec.  70.208T  Quarterly sampling; mechanized mining units.

    As of April 14, 2025:
    (a) The operator shall sample each calendar quarter:
    (1) The designated occupation (DO) in each MMU on consecutive 
normal production shifts until 15 valid representative samples are 
taken. The District Manager may require additional groups of 15 valid 
representative samples when information indicates the operator has not 
followed the approved ventilation plan for any MMU.
    (2) Each other designated occupation (ODO) specified in paragraphs 
(b)(1) through (10) of this section in each MMU or specified by the 
District Manager and identified in the approved mine ventilation plan 
on consecutive normal production shifts until 15 valid representative 
samples are taken. Sampling of each ODO type shall begin after 
fulfilling the sampling requirements of paragraph (a)(1) of this 
section. When required to sample more than one ODO type, each ODO type 
must be sampled over separate time periods during the calendar quarter.
    (3) The quarterly periods are:
    (i) January 1-March 31
    (ii) April 1-June 30
    (iii) July 1-September 30
    (iv) October 1-December 31.
    (b) Unless otherwise directed by the District Manager, the approved 
sampling device shall be worn by the miner assigned to perform the 
duties of the DO or ODO specified in paragraphs (b)(1) through (10) of 
this section or by the District Manager for each type of MMU.
    (1) Conventional section using cutting machine. DO--The cutting 
machine operator;
    (2) Conventional section blasting off the solid. DO--The loading 
machine operator;
    (3) Continuous mining section other than auger-type. DO--The 
continuous mining (CM) machine operator or mobile bridge operator when 
using continuous haulage; ODO--The roof bolting machine operator who 
works nearest the working face on the return air side of the continuous 
mining machine; the face haulage operators on MMUs using blowing face 
ventilation; the face haulage operators on MMUs ventilated by split 
intake air (``fishtail ventilation'') as part of a super-section; and 
face haulage operators where two continuous mining machines are 
operated on an MMU.
    (4) Continuous mining section using auger-type machine. DO--The 
jacksetter who works nearest the working face on the return air side of 
the continuous mining machine;
    (5) Scoop section using cutting machine. DO--The cutting machine 
operator;
    (6) Scoop section, blasting off the solid. DO--The coal drill 
operator;
    (7) Longwall section. DO--The longwall operator working on the 
tailgate side of the longwall mining machine; ODO--The jacksetter who 
works nearest the return air side of the longwall working face, and the 
mechanic;
    (8) Hand loading section with a cutting machine. DO--The cutting 
machine operator;
    (9) Hand loading section blasting off the solid. DO--The hand 
loader exposed to the greatest dust concentration; and
    (10) Anthracite mine sections. DO--The hand loader exposed to the 
greatest dust concentration.
    I [Reserved]
    (d) If a normal production shift is not achieved, the DO or ODO 
sample for that shift may be voided by MSHA. However, any sample, 
regardless of production, that exceeds the standard by at least 0.1 mg/
m\3\ shall be used in the determination of the equivalent concentration 
for that occupatioI(e) When a valid representative sample taken in 
accordance with this section meets or exceeds the ECV in table 1 to 
this section that corresponds to the particular sampling device used, 
the operator shall:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to at or below the respirable dust standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine f'reman's or equivalent of'icial's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.

[[Page 28475]]

    (f) Noncompliance with the standard is demonstrated during the 
sampling period when:
    (1) Three or more valid representative samples meet or exceed the 
ECV in table 1 to this section that corresponds to the particular 
sampling device used; or
    (2) The average for all valid representative samples meets or 
exceeds the ECV in table 1 to this section that corresponds to the 
particular sampling device used.
    (g)(1) Unless otherwise directed by the District Manager, upon 
issuance of a citation for a violation of the standard involving a DO 
in an MMU, paragraph (a)(1) of this section shall not apply to the DO 
in that MMU until the violation is abated and the citation is 
terminated in accordance with paragraphs (h) and (i) of this section.
    (2) Unless otherwise directed by the District Manager, upon 
issuance of a citation for a violation of the standard involving a type 
of ODO in an MMU, paragraph (a)(2) of this section shall not apply to 
that ODO type in that MMU until the violation is abated and the 
citation is terminated in accordance with paragraphs (g) and (h) of 
this section.
    (h) Upon issuance of a citation for violation of the standard, the 
operator shall take the following actions sequentially:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine f'reman's or equivalent of'icial's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.
    (4) Begin sampling, within 8 calendar days after the date the 
citation is issued, the environment of the affected occupation in the 
MMU on consecutive normal production shifts until five valid 
representative samples are taken.
    (i) A citation for a violation of the standard shall be terminated 
by MSHA when:
    (1) Each of the five valid representative samples is at or below 
the standard; and
    (2) The operator has submitted to the District Manager revised dust 
control parameters as part of the mine ventilation plan applicable to 
the MMU in the citation and the changes have been approved by the 
District Manager. The revised parameters shall reflect the control 
measures used by the operator to abate the violation.

 Table 1 to Sec.   70.208T--Excessive Concentration Values (ECV) Based on a Single Sample, Three Samples, or the
                  Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
                                                                                           ECV (mg/m\3\)
                  Section                                  Samples               -------------------------------
                                                                                      CMDPSU           CPDM
----------------------------------------------------------------------------------------------------------------
70.208 (e).................................  70.1-0(a)--Single sample...........            1.79            1.70
                                             70.1-0(b)--Single sample...........            0.74            0.57
70.208(f)(1)...............................  70.1-0(a)--3 or more samples.......            1.79            1.70
                                             70.1-0(b)--3 or more samples.......            0.74            0.57
70.208(f)(2)...............................  70.1-0(a)--5 sample average........            1.63            1.59
                                             70.1-0(b)--5 sample average........            0.61            0.53
70.208(f)(2)...............................  70.1-0(a)--15 sample average.......            1.58            1.56
                                             70.1-0(b)--15 sample average.......            0.57            0.52
70.208(i)(1)...............................  70.1-0(a)--Each of 5 samples.......            1.79            1.70
                                             70.1-0(b)--Each of 5 samples.......            0.74            0.57
----------------------------------------------------------------------------------------------------------------

Sec.  70.208  [Removed]

0
30. Effective April 14, 2025, remove Sec.  70.208.


Sec.  70.208T  [Redesignated as Sec.  70.208]

0
31. Effective April 14, 2025, redesignate Sec.  70.208T as Sec.  70.208 
and redesignate table 1 to Sec.  70.208T as table 1 to Sec.  70.208.

0
32. Amend Sec.  70.209 by revising the introductory text to read as 
follows:


Sec.  70.209  Quarterly sampling; designated areas.

    The following is required until April 14, 2025:
* * * * *

0
33. Add Sec.  70.209T to read as follows:


Sec.  70.209T  Quarterly sampling; designated areas.

    As of April 14, 2025:
    (a) The operator shall sample quarterly each designated area (DA) 
on consecutive production shifts until five valid representative 
samples are taken. The quarterly periods are:
    (1) January 1-March 31
    (2) April 1-June 30
    (3) July 1-September 30
    (4) October 1-December 31.
    (b) [Reserved].
    (c) When a valid representative sample taken in accordance with 
this section meets or exceeds the ECV in table 1 to this section that 
corresponds to the particular sampling device used, the operator shall:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to at or below the respirable dust standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.
    (d) Noncompliance with the standard is demonstrated during the 
sampling period when:

[[Page 28476]]

    (1) Two or more valid representative samples meet or exceed the ECV 
in table 1 to this section that corresponds to the particular sampling 
device used; or
    (2) The average for all valid representative samples meets or 
exceeds the ECV in table 1 to this section that corresponds to the 
particular sampling device used.
    (e) Unless otherwise directed by the District Manager, upon 
issuance of a citation for a violation of the standard, paragraph (a) 
of this section shall not apply to that DA until the violation is 
abated and the citation is terminated in accordance with paragraphs (e) 
and (f) of this section.
    (f) Upon issuance of a citation for a violation of the standard, 
the operator shall take the following actions sequentially:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.
    (4) Begin sampling, within 8 calendar days after the date the 
citation is issued, the environment of the affected DA on consecutive 
normal production shifts until five valid representative samples are 
taken.
    (g) A citation for a violation of the standard shall be terminated 
by MSHA when:
    (1) Each of the five valid representative samples is at or below 
the standard; and
    (2) The operator has submitted to the District Manager revised dust 
control parameters as part of the mine ventilation plan applicable to 
the DA in the citation, and the changes have been approved by the 
District Manager. The revised parameters shall reflect the control 
measures used by the operator to abate the violation.

  Table 1 to Sec.   70.209T--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                  Average of Five or Fifteen Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
                                                                                           ECV (mg/m\3\)
                  Section                                  Samples               -------------------------------
                                                                                      CMDPSU           CPDM
----------------------------------------------------------------------------------------------------------------
70.209 (c).................................  70.100(a)--Single sample...........            1.79            1.70
                                             70.100(b)--Single sample...........            0.74            0.57
70.209(d)(1)...............................  70.100(a)--2 or more samples.......            1.79            1.70
                                             70.100(b)--2 or more samples.......            0.74            0.57
70.209(d)(2)...............................  70.100(a)--5 sample average........            1.63            1.59
                                             70.100(b)--5 sample average........            0.61            0.53
70.209(d)(2)...............................  70.100(a)--15 sample average.......            1.58            1.56
                                             70.100(b)--15 sample average.......            0.57            0.52
70.209(g)(1)...............................  70.100(a)--Each of 5 samples.......            1.79            1.70
                                             70.100(b)--Each of 5 samples.......            0.74            0.57
----------------------------------------------------------------------------------------------------------------

Sec.  70.209  [Removed]

0
34. Effective April 14, 2025, remove Sec.  70.209.


Sec.  70.209T  [Redesignated as Sec.  70.209]

0
35. Effective April 14, 2025, redesignate Sec.  70.209T as Sec.  70.209 
and redesignate table 1 to Sec.  70.209T as table 1 to Sec.  70.209.

Tables 70-1 and 70-2 to Subpart C of Part 70 [Removed]

0
36. Effective April 14, 2025, remove tables 70-1 and 70-2 to subpart C 
of part 70.

PART 71--MANDATORY HEALTH STANDARDS--SURFACE COAL MINES AND SURFACE 
WORK AREAS OF UNDERGROUND COAL MINES

0
37. The authority citation for part 71 continues to read as follows:

    Authority:  30 U.S.C. 811, 813(h), 957.

Subpart A--General


Sec.  71.2  [Amended]

0
38. Effective April 14, 2025, amend Sec.  71.2 by removing the 
definition of ``Quartz''.

Subpart B--Dust Standards


Sec.  71.101  [Removed and Reserved]

0
39. Effective April 14, 2025, remove and reserve Sec.  71.101.

Subpart C--Sampling Procedures

0
40. Amend Sec.  71.205 by adding introductory text to read as follows:


Sec.  71.205  Approved sampling devices; operation; air flowrate.

    The following is required until April 14, 2025:
* * * * *

0
41. Add Sec.  71.205T to read as follows:


Sec.  71.205T  Approved sampling devices; operation; air flowrate.

    As of April 14, 2025:
    (a) Approved sampling devices shall be operated at the flowrate of 
2.0 L/min, if using a CMDPSU; at 2.2 L/min, if using a CPDM; or at a 
different flowrate recommended by the manufacturer.
    (b) If using a CMDPSU, each sampling device shall be examined each 
shift by a person certified in sampling during:
    (1) The second hour after being put into operation to assure it is 
in the proper location, operating properly, and at the proper flowrate. 
If the proper flowrate is not maintained, necessary adjustments shall 
be made by the certified person.
    (2) The last hour of operation to assure that it is operating 
properly and at the proper flowrate. If the proper flowrate is not 
maintained, the respirable dust sample shall be transmitted to MSHA 
with a notation by the certified person on the back of the dust data 
card stating that the proper flowrate was not maintained. Other events 
occurring during the collection of respirable dust samples that may 
affect the validity of the sample, such as

[[Page 28477]]

dropping of the sampling head assembly onto the mine floor, shall be 
noted on the back of the dust data card.
    (c) If using a CPDM, the person certified in sampling shall monitor 
the dust concentrations and the sampling status conditions being 
reported by the sampling device at mid-shift or more frequently as 
specified in the approved respirable dust control plan, if applicable, 
to assure: The sampling device is in the proper location and operating 
properly; and the work environment of the occupation being sampled 
remains in compliance with the standard at the end of the shift.


Sec.  71.205  [Removed]

0
42. Effective April 14, 2025, remove Sec.  71.205.


Sec.  71.205T  [Redesignated as Sec.  71.205]

0
43. Effective April 14, 2025, redesignate Sec.  71.205T as Sec.  
71.205.

0
44. Amend Sec.  71.206 by adding introductory text to read as follows:


Sec.  71.206  Quarterly sampling; designated work positions.

    The following is required until April 14, 2025:
* * * * *

0
45. Add Sec.  71.206T to read as follows:


Sec.  71.206T  Quarterly sampling; designated work positions.

    As of April 14, 2025:
    (a) Each operator shall take one valid representative sample from 
the DWP during each quarterly period. The quarterly periods are:
    (1) January 1-March 31
    (2) April 1-June 30
    (3) July 1-September 30
    (4) October 1-December 31.
    (b) [Reserved].
    (c) Designated work position samples shall be collected at 
locations to measure respirable dust generation sources in the active 
workings. The specific work positions at each mine where DWP samples 
shall be collected include:
    (1) Each highwall drill operator (MSHA occupation code 384);
    (2) Bulldozer operators (MSHA occupation code 368); and
    (3) Other work positions designated by the District Manager for 
sampling in accordance with Sec.  71.206(m).
    (d) Operators with multiple work positions specified in paragraphs 
(b)(2) and (3) of this section shall sample the DWP exposed to the 
greatest respirable dust concentration in each work position performing 
the same activity or task at the same location at the mine and exposed 
to the same dust generation source. Each operator shall provide the 
District Manager with a list identifying the specific work positions 
where DWP samples will be collected for:
    (1) Active mines--by October 1, 2014.
    (2) New mines--Within 30 calendar days of mine opening.
    (3) DWPs with a change in operational status that increases or 
reduces the number of active DWPs--within 7 calendar days of the change 
in status.
    (e) Each DWP sample shall be taken on a normal work shift. If a 
normal work shift is not achieved, the respirable dust sample shall be 
transmitted to MSHA with a notation by the person certified in sampling 
on the back of the dust data card stating that the sample was not taken 
on a normal work shift. When a normal work shift is not achieved, the 
sample for that shift may be voided by MSHA. However, any sample, 
regardless of whether a normal work shift was achieved, that exceeds 
the standard by at least 0.1 mg/m\3\ shall be used in the determination 
of the equivalent concentration for that occupation.
    (f) Unless otherwise directed by the District Manager, DWP samples 
shall be taken by placing the sampling device as follows:
    (1) Equipment operator: On the equipment operator or on the 
equipment within 36 inches of the operator's normal working position.
    (2) Non-equipment operators: On the miner assigned to the DWP or at 
a location that represents the maximum concentration of dust to which 
the miner is exposed.
    (g) Upon notification from MSHA that any valid representative 
sample taken from a DWP to meet the requirements of paragraph (a) of 
this section exceeds the standard, the operator shall, within 15 
calendar days of notification, sample that DWP each normal work shift 
until five valid representative samples are taken. The operator shall 
begin sampling on the first normal work shift following receipt of 
notification.
    (h) When a valid representative sample taken in accordance with 
this section meets or exceeds the excessive concentration value (ECV) 
in table 1 to this section that corresponds to the particular sampling 
device used, the mine operator shall:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.
    (i) Noncompliance with the standard is demonstrated during the 
sampling period when:
    (1) Two or more valid representative samples meet or exceed the ECV 
in table 1 to this section that corresponds to the particular sampling 
device used; or
    (2) The average for all valid representative samples meets or 
exceeds the ECV in table 1 to this section that corresponds to the 
particular sampling device used.
    (j) Unless otherwise directed by the District Manager, upon 
issuance of a citation for a violation of the standard, paragraph (a) 
of this section shall not apply to that DWP until the violation is 
abated and the citation is terminated in accordance with paragraphs (j) 
and (k) of this section.
    (k) Upon issuance of a citation for violation of the standard, the 
operator shall take the following actions sequentially:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the representative of miners.
    (4) Begin sampling, within 8 calendar days after the date the 
citation is issued, the environment of the affected DWP on consecutive 
normal work shifts until five valid representative samples are taken.

[[Page 28478]]

    (l) A citation for violation of the standard shall be terminated by 
MSHA when the equivalent concentration of each of the five valid 
representative samples is at or below the standard.
    (m) The District Manager may designate for sampling under this 
section additional work positions at a surface coal mine and at a 
surface work area of an underground coal mine where a concentration of 
respirable dust exceeding 50 percent of the standard has been measured 
by one or more MSHA valid representative samples.
    (n) The District Manager may withdraw from sampling any DWP 
designated for sampling under paragraph (m) of this section upon 
finding that the operator is able to maintain continuing compliance 
with the standard. This finding shall be based on the results of MSHA 
and operator valid representative samples taken during at least a 12-
month period.

  Table 1 to Sec.   71.206T--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                        Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
                                                                                           ECV (mg/m\3\)
                  Section                                  Samples               -------------------------------
                                                                                      CMDPSU           CPDM
----------------------------------------------------------------------------------------------------------------
71.206(h)..................................  Single sample......................            1.79            1.70
71.206(i)(1)...............................  2 or more samples..................            1.79            1.70
71.206(i)(2)...............................  5 sample average...................            1.63            1.59
71.206(l)..................................  Each of 5 samples..................            1.79            1.70
----------------------------------------------------------------------------------------------------------------

Sec.  71.206  [Removed]

0
46. Effective April 14, 2025, remove Sec.  71.206.


Sec.  71.206T  [Redesignated as Sec.  71.206]

0
47. Effective April 14, 2025, redesignate Sec.  71.206T as Sec.  71.206 
and redesignate table 1 to Sec.  71.206T as table 1 to Sec.  71.206.

Subpart D--Respirable Dust Control Plans

0
48. Amend Sec.  71.300 by adding introductory text to read as follows:


Sec.  71.300  Respirable dust control plan; filing requirements.

    The following is required until April 14, 2025:
* * * * *

0
49. Add Sec.  71.300T to read as follows:


Sec.  71.300T  Respirable dust control plan; filing requirements.

    As of April 14, 2025:
    (a) Within 15 calendar days after the termination date of a 
citation for violation of the standard, the operator shall submit to 
the District Manager for approval a written respirable dust control 
plan applicable to the DWP identified in the citation. The respirable 
dust control plan and revisions thereof shall be suitable to the 
conditions and the mining system of the coal mine and shall be adequate 
to continuously maintain respirable dust to at or below the standard at 
the DWP identified in the citation.
    (1) The mine operator shall notify the representative of miners at 
least 5 days prior to submission of a respirable dust control plan and 
any revision to a dust control plan. If requested, the mine operator 
shall provide a copy to the representative of miners at the time of 
notification;
    (2) A copy of the proposed respirable dust control plan, and a copy 
of any proposed revision, submitted for approval shall be made 
available for inspection by the representative of miners; and
    (3) A copy of the proposed respirable dust control plan, and a copy 
of any proposed revision, submitted for approval shall be posted on the 
mine bulletin board at the time of submittal. The proposed plan or 
proposed revision shall remain posted until it is approved, withdrawn, 
or denied.
    (4) Following receipt of the proposed plan or proposed revision, 
the representative of miners may submit timely comments to the District 
Manager, in writing, for consideration during the review process. Upon 
request, a copy of these comments shall be provided to the operator by 
the District Manager.
    (b) Each respirable dust control plan shall include at least the 
following:
    (1) The mine identification number and DWP number assigned by MSHA, 
the operator's name, mine name, mine address, and mine telephone number 
and the name, address, and telephone number of the principal officer in 
charge of health and safety at the mine;
    (2) The specific DWP at the mine to which the plan applies;
    (3) A detailed description of the specific respirable dust control 
measures used to abate the violation of the respirable dust standard; 
and
    (4) A detailed description of how each of the respirable dust 
control measures described in response to paragraph (b)(3) of this 
section will continue to be used by the operator, including at least 
the specific time, place and manner the control measures will be used.


Sec.  71.300  [Removed]

0
50. Effective April 14, 2025, remove Sec.  71.300.


Sec.  71.300T  [Redesignated as Sec.  71.300]

0
51. Effective April 14, 2025, redesignate Sec.  71.300T as Sec.  
71.300.

0
52. Amend Sec.  71.301 by adding introductory text to read as follows:


Sec.  71.301  Respirable dust control plan; approval by District 
Manager and posting.

    The following is required until April 14, 2025:
* * * * *

0
53. Add Sec.  71.301T to read as follows:


Sec.  71.301T  Respirable dust control plan; approval by District 
Manager and posting.

    As of April 8, 2026:
    (a) The District Manager will approve respirable dust control plans 
on a mine-by-mine basis. When approving respirable dust control plans, 
the District Manager shall consider whether:
    (1) The respirable dust control measures would be likely to 
maintain concentrations of respirable coal mine dust at or below the 
standard; and
    (2) The operator's compliance with all provisions of the respirable 
dust control plan could be objectively ascertained by MSHA.
    (b) MSHA may take respirable dust samples to determine whether the 
respirable dust control measures in the operator's plan effectively 
maintain concentrations of respirable coal mine dust at or below the 
applicable standard.
    (c) The operator shall comply with all provisions of each 
respirable dust control plan upon notice from MSHA that the respirable 
dust control plan is approved.
    (d) The approved respirable dust control plan and any revisions 
shall be:

[[Page 28479]]

    (1) Provided upon request to the representative of miners by the 
operator following notification of approval;
    (2) Made available for inspection by the representative of miners; 
and
    (3) Posted on the mine bulletin board within 1 working day 
following notification of approval, and shall remain posted for the 
period that the plan is in effect.
    (e) The operator may review respirable dust control plans and 
submit proposed revisions to such plans to the District Manager for 
approval.


Sec.  71.301  [Removed]

0
54. Effective April 14, 2025, remove Sec.  71.301.


Sec.  71.301T  [Redesignated as Sec.  71.301]

0
55. Effective April 14, 2025, redesignate Sec.  71.301T as Sec.  
71.301.

PART 72--HEALTH STANDARDS FOR COAL MINES

0
56. The authority citation for part 72 continues to read as follows:

    Authority:  30 U.S.C. 811, 813(h), 957.

Subpart E--Miscellaneous

0
57. Revise Sec.  72.710 to read as follows:


Sec.  72.710  Selection, fit, use, and maintenance of approved 
respirators.

    The following is required until April 14, 2025. In order to ensure 
the maximum amount of respiratory protection, approved respirators 
shall be selected, fitted, used, and maintained in accordance with the 
provisions of the American National Standards Institute's (ANSI) 
Practices for Respiratory Protection ANSI Z88.2-1969, which is 
incorporated by reference into this section with the approval of the 
Director of the Federal Register under 5 U.S.C. 552(a) and 1 CFR part 
51. This incorporation by reference (IBR) material is available for 
inspection at the Mine Safety and Health Administration (MSHA) and at 
the National Archives and Records Administration (NARA). Contact MSHA 
at: MSHA's Office of Standards, Regulations, and Variances, 201 12th 
Street South, Arlington, VA 22202-5450; (202) 693-9440; or any Mine 
Safety and Health Enforcement District Office. For information on the 
availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected].

0
58. Add Sec.  72.710T to read as follows:


Sec.  72.710T  Selection, fit, use, and maintenance of approved 
respirators.

    As of April 14, 2025: Approved respirators shall be selected, 
fitted, used, and maintained in accordance with the provisions of a 
written respiratory protection program consistent with the requirements 
of ASTM F3387-19. ASTM F3387-19, Standard Practice for Respiratory 
Protection, approved August 1, 2019, is incorporated by reference into 
this section with the approval of the Director of the Federal Register 
under 5 U.S.C. 552(a) and 1 CFR part 51. This incorporation by 
reference (IBR) material is available for inspection at the Mine Safety 
and Health Administration (MSHA) and at the National Archives and 
Records Administration (NARA). Contact MSHA at: MSHA's Office of 
Standards, Regulations, and Variances, 201 12th Street South, 
Arlington, VA 22202-5450; (202) 693-9440; or any Mine Safety and Health 
Enforcement District Office. For information on the availability of 
this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations or email [email protected]. The material may be obtained 
from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959; www.astm.org.


Sec.  72.710  [Removed]

0
59. Effective April 14, 2025, remove Sec.  72.710.


Sec.  72.710T  [Redesignated as Sec.  72.710]

0
60. Effective April 14, 2025, redesignate Sec.  72.710T as Sec.  
72.710.

0
61. Revise Sec.  72.800 to read as follows:


Sec.  72.800  Single, full-shift measurement of respirable coal mine 
dust.

    The Secretary will use a single, full-shift measurement of 
respirable coal mine dust to determine the average concentration on a 
shift since that measurement accurately represents atmospheric 
conditions to which a miner is exposed during such shift. Until April 
14, 2025, noncompliance with the respirable dust standard, in 
accordance with this subchapter, is demonstrated when a single, full-
shift measurement taken by MSHA meets or exceeds the applicable ECV in 
table 1 to Sec.  70.208, table 1 to Sec.  70.209, table 1 to Sec.  
71.206, or table 1 to Sec.  90.207 of this chapter that corresponds to 
the particular sampling device used. Upon issuance of a citation for a 
violation of the standard, and for MSHA to terminate the citation, the 
mine operator shall take the specified actions in this subchapter.

0
62. Add Sec.  72.800T to read as follows:


Sec.  72.800T  Single, full-shift measurement of respirable coal mine 
dust.

    The Secretary will use a single, full-shift measurement of 
respirable coal mine dust to determine the average concentration on a 
shift since that measurement accurately represents atmospheric 
conditions to which a miner is exposed during such shift. As of April 
14, 2025, noncompliance with the respirable dust standard, in 
accordance with this subchapter, is demonstrated when a single, full-
shift measurement taken by MSHA meets or exceeds the applicable ECV in 
table 1 to Sec.  70.208, table 1 to Sec.  70.209, table 1 to Sec.  
71.206, or table 1 to Sec.  90.207 of this chapter that corresponds to 
the particular sampling device used. Upon issuance of a citation for a 
violation of the standard, and for MSHA to terminate the citation, the 
mine operator shall take the specified actions in this subchapter.


Sec.  72.800  [Removed]

0
63. Effective April 14, 2025, remove Sec.  72.800.


Sec.  72.800T  [Redesignated as Sec.  72.800]

0
64. Effective April 14, 2025, redesignate Sec.  72.800T as Sec.  
72.800.

PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES

0
65. The authority citation for part 75 continues to read as follows:

    Authority:  30 U.S.C. 811, 813(h), 957.

Subpart D--Ventilation

0
66. Amend Sec.  75.350 by adding introductory text to read as follows:


Sec.  75.350  Belt air course ventilation.

    The following is required until April 14, 2025:
* * * * *

0
67. Add Sec.  75.350T to read as follows:


Sec.  75.350T  Belt air course ventilation.

    As of April 14, 2025:
    (a) The belt air course must not be used as a return air course; 
and except as provided in paragraph (b) of this section, the belt air 
course must not be used to provide air to working sections or to areas 
where mechanized mining equipment is being installed or removed.
    (1) The belt air course must be separated with permanent 
ventilation controls from return air courses and from other intake air 
courses except as provided in paragraph (c) of this section.

[[Page 28480]]

    (2) Effective December 31, 2009, the air velocity in the belt entry 
must be at least 50 feet per minute. When requested by the mine 
operator, the district manager may approve lower velocities in the 
ventilation plan based on specific mine conditions. Air velocities must 
be compatible with all fire detection systems and fire suppression 
systems used in the belt entry.
    (b) The use of air from a belt air course to ventilate a working 
section, or an area where mechanized mining equipment is being 
installed or removed, shall be permitted only when evaluated and 
approved by the district manager in the mine ventilation plan. The mine 
operator must provide justification in the plan that the use of air 
from a belt entry would afford at least the same measure of protection 
as where belt haulage entries are not used to ventilate working places. 
In addition, the following requirements must be met:
    (1) The belt entry must be equipped with an AMS that is installed, 
operated, examined, and maintained as specified in Sec.  75.351.
    (2) All miners must be trained annually in the basic operating 
principles of the AMS, including the actions required in the event of 
activation of any AMS alert or alarm signal. This training must be 
conducted prior to working underground in a mine that uses belt air to 
ventilate working sections or areas where mechanized mining equipment 
is installed or removed. It must be conducted as part of a miner's 30 
CFR part 48 new miner training (Sec.  48.5), experienced miner training 
(Sec.  48.6), or annual refresher training (Sec.  48.8).
    (3)(i) The average concentration of respirable dust in the belt air 
course, when used as a section intake air course, shall be maintained 
at or below 0.5 milligrams per cubic meter of air (mg/m\3\).
    (ii) A permanent designated area (DA) for dust measurements must be 
established at a point no greater than 50 feet upwind from the section 
loading point in the belt entry when the belt air flows over the 
loading point or no greater than 50 feet upwind from the point where 
belt air is mixed with air from another intake air course near the 
loading point. The DA must be specified and approved in the ventilation 
plan.
    (4) The primary escapeway must be monitored for carbon monoxide or 
smoke as specified in Sec.  75.351(f).
    (5) The area of the mine with a belt air course must be developed 
with three or more entries.
    (6) In areas of the mine developed after the effective date of this 
rule, unless approved by the district manager, no more than 50% of the 
total intake air, delivered to the working section or to areas where 
mechanized mining equipment is being installed or removed, can be 
supplied from the belt air course. The locations for measuring these 
air quantities must be approved in the mine ventilation plan.
    (7) The air velocity in the belt entry must be at least 100 feet 
per minute. When requested by the mine operator, the district manager 
may approve lower velocities in the ventilation plan based on specific 
mine conditions.
    (8) The air velocity in the belt entry must not exceed 1,000 feet 
per minute. When requested by the mine operator, the district manager 
may approve higher velocities in the ventilation plan based on specific 
mine conditions.
    (c) Notwithstanding the provisions of Sec.  75.380(g), additional 
intake air may be added to the belt air course through a point-feed 
regulator. The location and use of point feeds must be approved in the 
mine ventilation plan.
    (d) If the air through the point-feed regulator enters a belt air 
course which is used to ventilate a working section or an area where 
mechanized mining equipment is being installed or removed, the 
following conditions must be met:
    (1) The air current that will pass through the point-feed regulator 
must be monitored for carbon monoxide or smoke at a point within 50 
feet upwind of the point-feed regulator. A second point must be 
monitored 1,000 feet upwind of the point-feed regulator unless the mine 
operator requests that a lesser distance be approved by the district 
manager in the mine ventilation plan based on mine specific conditions;
    (2) The air in the belt air course must be monitored for carbon 
monoxide or smoke upwind of the point-feed regulator. This sensor must 
be in the belt air course within 50 feet of the mixing point where air 
flowing through the point-feed regulator mixes with the belt air;
    (3) The point-feed regulator must be provided with a means to close 
the regulator from the intake air course without requiring a person to 
enter the crosscut where the point-feed regulator is located. The 
point-feed regulator must also be provided with a means to close the 
regulator from a location in the belt air course immediately upwind of 
the crosscut containing the point-feed regulator;
    (4) A minimum air velocity of 300 feet per minute must be 
maintained through the point-feed regulator;
    (5) The location(s) and use of a point-feed regulator(s) must be 
approved in the mine ventilation plan and shown on the mine ventilation 
map; and
    (6) An AMS must be installed, operated, examined, and maintained as 
specified in Sec.  75.351.


Sec.  75.350  [Removed]

0
68. Effective April 14, 2025, remove Sec.  75.350.


Sec.  75.350T  [Redesignated as Sec.  75.350]

0
69. Effective April 14, 2025, redesignate Sec.  75.350T as Sec.  
75.350.

PART 90--MANDATORY HEALTH STANDARDS--COAL MINERS WHO HAVE EVIDENCE 
OF THE DEVELOPMENT OF PNEUMOCONIOSIS

0
70. The authority citation for part 90 continues to read as follows:

    Authority:  30 U.S.C. 811, 813(h), 957.

Subpart A--General

0
71. Revise Sec.  90.2 to read as follows:


Sec.  90.2  Definitions.

    Until April 14, 2025, the following definitions apply in this part:
    Act. The Federal Mine Safety and Health Act of 1977, Public Law 91-
173, as amended by Public Law 95-164 and Public Law 109-236.
    Active workings. Any place in a coal mine where miners are normally 
required to work or travel.
    Approved sampling device. A sampling device approved by the 
Secretary and Secretary for Health and Human Services (HHS) under part 
74 of this subchapter.
    Certified person. An individual certified by the Secretary in 
accordance with Sec.  90.202 to take respirable dust samples required 
by this part or certified in accordance with Sec.  90.203 to perform 
the maintenance and calibration of respirable dust sampling equipment 
as required by this part.
    Coal mine dust personal sampler unit (CMDPSU). A personal sampling 
device approved under part 74, subpart B, of this subchapter.
    Concentration. A measure of the amount of a substance contained per 
unit volume of air.
    Continuous personal dust monitor (CPDM). A personal sampling device 
approved under part 74, subpart C, of this subchapter.
    District Manager. The manager of the Coal Mine Safety and Health 
District in which the mine is located.
    Equivalent concentration. The concentration of respirable coal mine 
dust, including quartz, expressed in milligrams per cubic meter of air 
(mg/

[[Page 28481]]

m\3\) as measured with an approved sampling device, determined by 
dividing the weight of dust in milligrams collected on the filter of an 
approved sampling device by the volume of air in cubic meters passing 
through the filter (sampling time in minutes (t) times the sampling 
airflow rate in cubic meters per minute), and then converting that 
concentration to an equivalent concentration as measured by the Mining 
Research Establishment (MRE) instrument. When the approved sampling 
device is:
    (1) The CMDPSU, the equivalent concentration is determined by 
multiplying the concentration of respirable coal mine dust by the 
constant factor prescribed by the Secretary.
    (2) The CPDM, the device shall be programmed to automatically 
report end-of-shift concentration measurements as equivalent 
concentrations.
    Mechanized mining unit (MMU). A unit of mining equipment including 
hand loading equipment used for the production of material; or a 
specialized unit which uses mining equipment other than specified in 
Sec.  70.206(b) or in Sec.  70.208(b) of this subchapter. Each MMU will 
be assigned a four-digit identification number by MSHA, which is 
retained by the MMU regardless of where the unit relocates within the 
mine. However, when:
    (1) Two sets of mining equipment are used in a series of working 
places within the same working section and only one production crew is 
employed at any given time on either set of mining equipment, the two 
sets of equipment shall be identified as a single MMU.
    (2) Two or more sets of mining equipment are simultaneously engaged 
in cutting, mining, or loading coal or rock from working places within 
the same working section, each set of mining equipment shall be 
identified as a separate MMU.
    MRE instrument. The gravimetric dust sampler with a four channel 
horizontal elutriator developed by the Mining Research Establishment of 
the National Coal Board, London, England.
    MSHA. The Mine Safety and Health Administration of the U.S. 
Department of Labor.
    Normal work duties. Duties which the part 90 miner performs on a 
routine day-to-day basis in his or her job classification at a mine.
    Part 90 miner. A miner employed at a coal mine who has exercised 
the option under the old section 203(b) program (30 CFR part 90, 
effective as of July 1, 1972), or under Sec.  90.3 of this part to work 
in an area of a mine where the average concentration of respirable dust 
in the mine atmosphere during each shift to which that miner is exposed 
is continuously maintained at or below the applicable standard, and who 
has not waived these rights.
    Quartz. Crystalline silicon dioxide (SiO2) not chemically combined 
with other substances and having a distinctive physical structure.
    Representative sample. A respirable dust sample, expressed as an 
equivalent concentration, that reflects typical dust concentration 
levels in the working environment of the part 90 miner when performing 
normal work duties.
    Respirable dust. Dust collected with a sampling device approved by 
the Secretary and the Secretary of HHS in accordance with part 74 (Coal 
Mine Dust Sampling Devices) of this subchapter.
    Secretary. The Secretary of Labor or a delegate.
    Secretary of Health and Human Services. The Secretary of Health and 
Human Services (HHS) or the Secretary of Health, Education, and 
Welfare.
    Transfer. Any change in the work assignment of a part 90 miner by 
the operator and includes:
    (1) Any change in occupation code of a part 90 miner;
    (2) any movement of a part 90 miner to or from an MMU; or
    (3) any assignment of a part 90 miner to the same occupation in a 
different location at a mine.
    Valid respirable dust sample. A respirable dust sample collected 
and submitted as required by this part, including any sample for which 
the data were electronically transmitted to MSHA, and not voided by 
MSHA.

0
72. Add Sec.  90.2T to read as follows:


Sec.  90.2T  Definitions.

    As April 14, 2025, the following definitions apply in this part:
    Act. The Federal Mine Safety and Health Act of 1977, Public Law 91-
173, as amended by Public Law 95-164 and Public Law 109-236.
    Active workings. Any place in a coal mine where miners are normally 
required to work or travel.
    Approved sampling device. A sampling device approved by the 
Secretary and Secretary for Health and Human Services (HHS) under part 
74 of this subchapter.
    Certified person. An individual certified by the Secretary in 
accordance with Sec.  90.202 to take respirable dust samples required 
by this part or certified in accordance with Sec.  90.203 to perform 
the maintenance and calibration of respirable dust sampling equipment 
as required by this part.
    Coal mine dust personal sampler unit (CMDPSU). A personal sampling 
device approved under part 74, subpart B, of this subchapter.
    Concentration. A measure of the amount of a substance contained per 
unit volume of air.
    Continuous personal dust monitor (CPDM). A personal sampling device 
approved under part 74, subpart C, of this subchapter.
    District Manager. The manager of the Coal Mine Safety and Health 
District in which the mine is located.
    Equivalent concentration. The concentration of respirable coal mine 
dust, including quartz, expressed in milligrams per cubic meter of air 
(mg/m\3\) as measured with an approved sampling device, determined by 
dividing the weight of dust in milligrams collected on the filter of an 
approved sampling device by the volume of air in cubic meters passing 
through the filter (sampling time in minutes (t) times the sampling 
airflow rate in cubic meters per minute), and then converting that 
concentration to an equivalent concentration as measured by the Mining 
Research Establishment (MRE) instrument. When the approved sampling 
device is:
    (1) The CMDPSU, the equivalent concentration is determined by 
multiplying the concentration of respirable coal mine dust by the 
constant factor prescribed by the Secretary.
    (2) The CPDM, the device shall be programmed to automatically 
report end-of-shift concentration measurements as equivalent 
concentrations.
    Mechanized mining unit (MMU). A unit of mining equipment including 
hand loading equipment used for the production of material; or a 
specialized unit which uses mining equipment other than specified in 
Sec.  70.206(b) or in Sec.  70.208(b) of this subchapter. Each MMU will 
be assigned a four-digit identification number by MSHA, which is 
retained by the MMU regardless of where the unit relocates within the 
mine. However, when:
    (1) Two sets of mining equipment are used in a series of working 
places within the same working section and only one production crew is 
employed at any given time on either set of mining equipment, the two 
sets of equipment shall be identified as a single MMU.
    (2) Two or more sets of mining equipment are simultaneously engaged 
in cutting, mining, or loading coal or rock from working places within 
the same working section, each set of mining equipment shall be 
identified as a separate MMU.

[[Page 28482]]

    MRE instrument. The gravimetric dust sampler with a four channel 
horizontal elutriator developed by the Mining Research Establishment of 
the National Coal Board, London, England.
    MSHA. The Mine Safety and Health Administration of the U.S. 
Department of Labor.
    Normal work duties. Duties which the part 90 miner performs on a 
routine day-to-day basis in his or her job classification at a mine.
    Part 90 miner. A miner employed at a coal mine who has exercised 
the option under the old section 203(b) program (30 CFR part 90, 
effective as of July 1, 1972), or under Sec.  90.3 to work in an area 
of a mine where the average concentration of respirable dust in the 
mine atmosphere during each shift to which that miner is exposed is 
continuously maintained at or below the standard, and who has not 
waived these rights.
    Representative sample. A respirable dust sample, expressed as an 
equivalent concentration, that reflects typical dust concentration 
levels in the working environment of the part 90 miner when performing 
normal work duties.
    Respirable dust. Dust collected with a sampling device approved by 
the Secretary and the Secretary of HHS in accordance with part 74 (Coal 
Mine Dust Sampling Devices) of this subchapter.
    Secretary. The Secretary of Labor or a delegate.
    Secretary of Health and Human Services. The Secretary of Health and 
Human Services (HHS) or the Secretary of Health, Education, and 
Welfare.
    Transfer. Any change in the work assignment of a part 90 miner by 
the operator and includes:
    (1) Any change in occupation code of a part 90 miner;
    (2) any movement of a part 90 miner to or from an MMU; or
    (3) any assignment of a part 90 miner to the same occupation in a 
different location at a mine.
    Valid respirable dust sample. A respirable dust sample collected 
and submitted as required by this part, including any sample for which 
the data were electronically transmitted to MSHA, and not voided by 
MSHA.


Sec.  90.2  [Removed]

0
73. Effective April 14, 2025, remove Sec.  90.2.


Sec.  90.2T  [Redesignated as Sec.  90.2]

0
74. Effective April 14, 2025, redesignate Sec.  90.2T as Sec.  90.2.

0
75. Amend Sec.  90.3 by adding the introductory text to read as 
follows:


Sec.  90.3  Part 90 option; notice of eligibility; exercise of option.

    The following is required until April 14, 2025:
* * * * *

0
76. Add Sec.  90.3T to read as follows:


Sec.  90.3T  Part 90 option; notice of eligibility; exercise of option.

    Effective April 14, 2025:
    (a) Any miner employed at a coal mine who, in the judgment of the 
Secretary of HHS, has evidence of the development of pneumoconiosis 
based on a chest X-ray, read and classified in the manner prescribed by 
the Secretary of HHS, or based on other medical examinations shall be 
afforded the option to work in an area of a mine where the average 
concentration of respirable dust in the mine atmosphere during each 
shift to which that miner is exposed is continuously maintained at or 
below the standard. Each of these miners shall be notified in writing 
of eligibility to exercise the option.
    (b) Any miner who is a section 203(b) miner on January 31, 1981, 
shall be a part 90 miner on February 1, 1981, entitled to full rights 
under this part to retention of pay rate, future actual wage increases, 
and future work assignment, shift and respirable dust protection.
    (c) Any part 90 miner who is transferred to a position at the same 
or another coal mine shall remain a part 90 miner entitled to full 
rights under this part at the new work assignment.
    (d) The option to work in a low dust area of the mine may be 
exercised for the first time by any miner employed at a coal mine who 
was eligible for the option under the old section 203(b) program 
(www.msha.gov/REGSTECHAMEND.htm), or is eligible for the option under 
this part by sending a written request to the Chief, Division of 
Health, Mine Safety and Health Enforcement, MSHA, 201 12th Street 
South, Arlington, VA 22202-5452.
    (e) The option to work in a low dust area of the mine may be re-
exercised by any miner employed at a coal mine who exercised the option 
under the old section 203(b) program (www.msha.gov/REGSTECHAMEND.htm) 
or exercised the option under this part by sending a written request to 
the Chief, Division of Health, Mine Safety and Health Enforcement, 
MSHA, 201 12th Street South, Arlington, VA 22202-5452. The request 
should include the name and address of the mine and operator where the 
miner is employed.
    (f) No operator shall require from a miner a copy of the medical 
information received from the Secretary or Secretary of HHS.


Sec.  90.3  [Removed]

0
77. Effective April 14, 2025, remove Sec.  90.3.


Sec.  90.3T  [Redesignated as Sec.  90.3]

0
78. Effective April 14, 2025, redesignate Sec.  90.3T as Sec.  90.3.

Subpart B--Dust Standards, Rights of Part 90 Miners

0
79. Amend Sec.  90.100 by adding introductory text to read as follows:


Sec.  90.100  Respirable dust standard.

    The following is required until April 14, 2025. After the 20th 
calendar day following receipt of notification from MSHA that a part 90 
miner is employed at the mine, the operator shall continuously maintain 
the average concentration of respirable dust in the mine atmosphere 
during each shift to which the part 90 miner in the active workings of 
the mine is exposed, as measured with an approved sampling device and 
expressed in terms of an equivalent concentration, at or below:
* * * * *

0
80. Add Sec.  90.100T to read as follows:


Sec.  90.100T  Respirable dust standard.

    The following is required as of April 14, 2025. After the 20th 
calendar day following receipt of notification from MSHA that a part 90 
miner is employed at the mine, the operator shall continuously maintain 
the average concentration of respirable dust in the mine atmosphere 
during each shift to which the part 90 miner in the active workings of 
the mine is exposed, as measured with an approved sampling device and 
expressed in terms of an equivalent concentration, at or below 0.5 mg/
m\3\.


Sec.  90.100  [Removed]

0
81. Effective April 14, 2025, remove Sec.  90.100.


Sec.  90.100T  [Redesignated as Sec.  90.100]

0
82. Effective April 14, 2025, redesignate Sec.  90.100T as Sec.  
90.100.


Sec.  90.101  [Removed and Reserved]

0
83. Effective April 14, 2025, remove and reserve Sec.  90.101.

0
84. Amend Sec.  90.102 by adding introductory text to read as follows:


Sec.  90.102  Transfer; notice.

    The following is required until April 14, 2025:
* * * * *

0
85. Add Sec.  90.102T to read as follows:


Sec.  90.102T  Transfer; notice.

    As of April 14, 2025:

[[Page 28483]]

    (a) Whenever a part 90 miner is transferred in order to meet the 
standard, the operator shall transfer the miner to an existing position 
at the same coal mine on the same shift or shift rotation on which the 
miner was employed immediately before the transfer. The operator may 
transfer a part 90 miner to a different coal mine, a newly created 
position or a position on a different shift or shift rotation if the 
miner agrees in writing to the transfer. The requirements of this 
paragraph do not apply when the respirable dust concentration in a part 
90 miner's work position complies with the standard but circumstances, 
such as reductions in workforce or changes in operational status, 
require a change in the miner's job or shift assignment.
    (b) On or before the 20th calendar day following receipt of 
notification from MSHA that a part 90 miner is employed at the mine, 
the operator shall give the District Manager written notice of the 
occupation and, if applicable, the MMU unit to which the part 90 miner 
shall be assigned on the 21st calendar day following receipt of the 
notification from MSHA.
    (c) After the 20th calendar day following receipt of notification 
from MSHA that a part 90 miner is employed at the mine, the operator 
shall give the District Manager written notice before any transfer of a 
part 90 miner. This notice shall include the scheduled date of the 
transfer.


Sec.  90.102  [Removed]

0
86. Effective April 14, 2025, remove Sec.  90.102.


Sec.  90.102T  [Redesignated as Sec.  90.102]

0
87. Effective April 14, 2025, redesignate Sec.  90.102T as Sec.  
90.102.

0
88. Revise Sec.  90.104 to read as follows:


Sec.  90.104  Waiver of rights; re-exercise of option.

    The following is required until April 14, 2025:
    (a) A part 90 miner may waive his or her rights and be removed from 
MSHA's active list of miners who have rights under part 90 by:
    (1) Giving written notification to the Chief, Division of Health, 
Mine Safety and Health Enforcement, MSHA, that the miner waives all 
rights under this part;
    (2) Applying for and accepting a position in an area of a mine 
which the miner knows has an average respirable dust concentration 
exceeding the applicable standard; or
    (3) Refusing to accept another position offered by the operator at 
the same coal mine that meets the requirements of Sec. Sec.  90.100, 
90.101 and 90.102(a) after dust sampling shows that the present 
position exceeds the applicable standard.
    (b) If rights under part 90 are waived, the miner gives up all 
rights under part 90 until the miner re-exercises the option in 
accordance with Sec.  90.3(e) (Part 90 option; notice of eligibility; 
exercise of option).
    (c) If rights under part 90 are waived, the miner may re-exercise 
the option under this part in accordance with Sec.  90.3(e) (Part 90 
option; notice of eligibility; exercise of option) at any time.

0
89. Add Sec.  90.104T to read as follows:


Sec.  90.104T  Waiver of rights; re-exercise of option.

    As of April 14, 2025:
    (a) A part 90 miner may waive his or her rights and be removed from 
MSHA's active list of miners who have rights under part 90 by:
    (1) Giving written notification to the Chief, Division of Health, 
Mine Safety and Health Enforcement, MSHA, that the miner waives all 
rights under this part;
    (2) Applying for and accepting a position in an area of a mine 
which the miner knows has an average respirable dust concentration 
exceeding the standard; or
    (3) Refusing to accept another position offered by the operator at 
the same coal mine that meets the requirements of Sec. Sec.  90.100, 
90.101 and 90.102(a) after dust sampling shows that the present 
position exceeds the applicable standard.
    (b) If rights under part 90 are waived, the miner gives up all 
rights under part 90 until the miner re-exercises the option in 
accordance with Sec.  90.3(e) (Part 90 option; notice of eligibility; 
exercise of option).
    (c) If rights under part 90 are waived, the miner may re-exercise 
the option under this part in accordance with Sec.  90.3(e) (Part 90 
option; notice of eligibility; exercise of option) at any time.


Sec.  90.104  [Removed]

0
90. Effective April 14, 2025, remove Sec.  90.104.


Sec.  90.104T  [Redesignated as Sec.  90.104]

0
91. Effective April 14, 2025, redesignate Sec.  90.104T as Sec.  
90.104.

Subpart C--Sampling Procedures

0
92. Amend Sec.  90.205 by adding introductory text to read as follows:


Sec.  90.205  Approved sampling devices; operation; air flowrate.

    The following is required until April 14, 2025:
* * * * *

0
93. Add Sec.  90.205T to read as follows:


Sec.  90.205T  Approved sampling devices; operation; air flowrate.

    As of April 14, 2025:
    (a) Approved sampling devices shall be operated at the flowrate of 
2.0 L/min if using a CMDPSU; at 2.2 L/min if using a CPDM; or at a 
different flowrate recommended by the manufacturer.
    (b) If using a CMDPSU, each approved sampling device shall be 
examined each shift, by a person certified in sampling during:
    (1) The second hour after being put into operation to assure it is 
in the proper location, operating properly, and at the proper flowrate. 
If the proper flowrate is not maintained, necessary adjustments shall 
be made by the certified person. This examination is not required if 
the sampling device is being operated in an anthracite coal mine using 
the full box, open breast, or slant breast mining method.
    (2) The last hour of operation to assure that the sampling device 
is operating properly and at the proper flowrate. If the proper 
flowrate is not maintained, the respirable dust sample shall be 
transmitted to MSHA with a notation by the certified person on the back 
of the dust data card stating that the proper flowrate was not 
maintained. Other events occurring during the collection of respirable 
dust samples that may affect the validity of the sample, such as 
dropping of the sampling head assembly onto the mine floor, shall be 
noted on the back of the dust data card.
    (c) If using a CPDM, the person certified in sampling shall monitor 
the dust concentrations and the sampling status conditions being 
reported by the sampling device at mid-shift or more frequently as 
specified in the approved respirable dust control plan, if applicable, 
to assure: The sampling device is in the proper location and operating 
properly; and the work environment of the Part 90 miner being sampled 
remains in compliance with the standard at the end of the shift. This 
monitoring is not required if the sampling device is being operated in 
an anthracite coal mine using the full box, open breast, or slant 
breast mining method.


Sec.  90.205  [Removed]

0
94. Effective April 14, 2025, remove Sec.  90.205.

[[Page 28484]]

Sec.  90.205T  [Redesignated as Sec.  90.205]

0
95. Effective April 14, 2025, redesignate Sec.  90.205T as Sec.  
90.205.

0
96. Amend Sec.  90.206 by adding introductory text to read as follows:


Sec.  90.206  Exercise of option or transfer sampling.

    The following is required until April 14, 2025:
* * * * *

0
97. Add Sec.  90.206T to read as follows:


Sec.  90.206T  Exercise of option or transfer sampling.

    (a) The operator shall take five valid representative dust samples 
for each part 90 miner within 15 calendar days after:
    (1) The 20-day period specified for each part 90 miner in Sec.  
90.100; and
    (2) Implementing any transfer after the 20th calendar day following 
receipt of notification from MSHA that a part 90 miner is employed at 
the mine.
    (b) Noncompliance with the standard shall be determined in 
accordance with Sec.  90.207(d).
    (c) Upon issuance of a citation for a violation of the standard, 
the operator shall comply with Sec.  90.207(f).


Sec.  90.206  [Removed]

0
98. Effective April 14, 2025, remove Sec.  90.206.


Sec.  90.206T  [Redesignated as Sec.  90.206]

0
99. Effective April 14, 2025, redesignate Sec.  90.206T as Sec.  
90.206.

0
100. Amend Sec.  90.207 by adding introductory text to read as follows:


Sec.  90.207  Quarterly sampling.

    The following is required until April 14, 2025:
* * * * *

0
101. Add Sec.  90.207T to read as follows:


Sec.  90.207T  Quarterly sampling.

    As of April 14, 2025:
    (a) Each operator shall take five valid representative samples 
every calendar quarter from the environment of each part 90 miner while 
performing normal work duties. Part 90 miner samples shall be collected 
on consecutive work days. The quarterly periods are:
    (1) January 1-March 31
    (2) April 1-June 30
    (3) July 1-September 30
    (4) October 1-December 31.
    (b) [Reserved]
    (c) When a valid representative sample taken in accordance with 
this section meets or exceeds the ECV in table 1 to this section 
corresponding to the particular sampling device used, the mine operator 
shall:
    (1) Make approved respiratory equipment available to affected 
miners in accordance with Sec.  72.700 of this chapter;
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to below the standard; and
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the part 90 miner.
    (d) Noncompliance with the standard is demonstrated during the 
sampling period when:
    (1) Two or more valid representative samples meet or exceed the ECV 
in table 1 to this section that corresponds to the particular sampling 
device used; or
    (2) The average for all valid representative samples meets or 
exceeds the ECV in table 1 to this section that corresponds to the 
particular sampling device used.
    (e) Unless otherwise directed by the District Manager, upon 
issuance of a citation for a violation of the standard, paragraph (a) 
of this section shall not apply to that Part 90 miner until the 
violation is abated and the citation is terminated in accordance with 
paragraphs (e) and (f) of this section.
    (f) Upon issuance of a citation for a violation of the standard, 
the operator shall take the following actions sequentially:
    (1) Make approved respiratory equipment available to the affected 
part 90 miner in accordance with Sec.  72.700 of this subchapter.
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to below the standard. If the corrective action 
involves:
    (i) Reducing the respirable dust levels in the work position of the 
part 90 miner identified in the citation, the operator shall implement 
the proposed corrective actions and begin sampling the affected miner 
within 8 calendar days after the date the citation is issued, until 
five valid representative samples are taken.
    (ii) Transferring the Part 90 miner to another work position at the 
mine to meet the standard, the operator shall comply with Sec.  90.102 
and then sample the affected miner in accordance with Sec.  90.206(a).
    (3) Make a record of the corrective actions taken. The record shall 
be certified by the mine foreman or equivalent mine official, no later 
than the end of the mine foreman's or equivalent official's next 
regularly scheduled working shift. The record shall be made in a secure 
book that is not susceptible to alteration or electronically in a 
computer system so as to be secure and not susceptible to alteration. 
Such records shall be retained at a surface location at the mine for at 
least 1 year and shall be made available for inspection by authorized 
representatives of the Secretary and the part 90 miner.
    (g) A citation for a violation of the standard shall be terminated 
by MSHA when the equivalent concentration of each of the five valid 
representative samples is below the standard.

  Table 1 to Sec.   90.207T--Excessive Concentration Values (ECV) Based on a Single Sample, Two Samples, or the
                        Average of Five Full-Shift CMDPSU/CPDM Concentration Measurements
----------------------------------------------------------------------------------------------------------------
                                                                                           ECV (mg/m\3\)
                  Section                                  Samples               -------------------------------
                                                                                      CMDPSU           CPDM
----------------------------------------------------------------------------------------------------------------
90.207(c)..................................  Single sample......................            0.74            0.57
90.207(d)(1)...............................  2 or more samples..................            0.74            0.57
90.207(d)(2)...............................  5 sample average...................            0.61            0.53
90.207(g)..................................  Each of 5 samples..................            0.74            0.57
----------------------------------------------------------------------------------------------------------------


[[Page 28485]]

Sec.  90.207  [Removed]

0
102. Effective April 14, 2025, remove Sec.  90.207.


Sec.  90.207T  [Redesignated as Sec.  90.207]

0
103. Effective April 14, 2025], redesignate Sec.  90.207T as Sec.  
90.207.

Subpart D--Respirable Dust Control Plans

0
104. Amend Sec.  90.300 by adding introductory text to read as follows:


Sec.  90.300  Respirable dust control plan; filing requirements.

    The following is required until April 14, 2025:
* * * * *

0
105. Add Sec.  90.300T to read as follows:


Sec.  90.300T  Respirable dust control plan; filing requirements.

    As of April 14, 2025:
    (a) If an operator abates a violation of the standard by reducing 
the respirable dust level in the position of the Part 90 miner, the 
operator shall submit to the District Manager for approval a written 
respirable dust control plan for the Part 90 miner in the position 
identified in the citation within 15 calendar days after the citation 
is terminated. The respirable dust control plan and revisions thereof 
shall be suitable to the conditions and the mining system of the coal 
mine and shall be adequate to continuously maintain respirable dust 
below the standard for that Part 90 miner.
    (b) Each respirable dust control plan shall include at least the 
following:
    (1) The mine identification number assigned by MSHA, the operator's 
name, mine name, mine address, and mine telephone number and the name, 
address and telephone number of the principal officer in charge of 
health and safety at the mine;
    (2) The name and MSHA Individual Identification Number of the part 
90 miner and the position at the mine to which the plan applies;
    (3) A detailed description of how each of the respirable dust 
control measures used to continuously maintain concentrations of 
respirable coal mine dust below the standard; and
    (4) A detailed description of how each of the respirable dust 
control measures described in response to paragraph (b)(3) of this 
section will continue to be used by the operator, including at least 
the specific time, place, and manner the control measures will be used.


Sec.  90.300  [Removed]

0
106. Effective April 14, 2025, remove Sec.  90.300.


Sec.  90.300T  [Redesignated as Sec.  90.300]

0
107. Effective April 14, 2025, redesignate Sec.  90.300T as Sec.  
90.300.

0
108. Amend Sec.  90.301 by adding introductory text to read as follows:


Sec.  90.301  Respirable dust control plan; approval by District 
Manager; copy to part 90 miner.

    The following is required until April 14, 2025:
* * * * *

0
109. Add Sec.  90.301T to read as follows:


Sec.  90.301T  Respirable dust control plan; approval by District 
Manager; copy to part 90 miner.

    As of April 14, 2025:
    (a) The District Manager will approve respirable dust control plans 
on a mine-by-mine basis. When approving respirable dust control plans, 
the District Manager shall consider whether:
    (1) The respirable dust control measures would be likely to 
maintain concentrations of respirable coal mine dust below the 
standard; and
    (2) The operator's compliance with all provisions of the respirable 
dust control plan could be objectively ascertained by MSHA.
    (b) MSHA may take respirable dust samples to determine whether the 
respirable dust control measures in the operator's plan effectively 
maintain concentrations of respirable coal mine dust below the 
standard.
    (c) The operator shall comply with all provisions of each 
respirable dust control plan upon notice from MSHA that the respirable 
dust control plan is approved.
    (d) The operator shall provide a copy of the current respirable 
dust control plan required under this part to the part 90 miner. The 
operator shall not post the original or a copy of the plan on the mine 
bulletin board.
    (e) The operator may review respirable dust control plans and 
submit proposed revisions to such plans to the District Manager for 
approval.


Sec.  90.301  [Removed]

0
110. Effective April 14, 2025, remove Sec.  90.301.


Sec.  90.301T  [Redesignated as Sec.  90.301]

0
111. Effective April 14, 2025, redesignate Sec.  90.301T as Sec.  
90.301.

[FR Doc. 2024-06920 Filed 4-16-24; 8:45 am]
BILLING CODE 4520-43-P