[Federal Register Volume 88, Number 133 (Thursday, July 13, 2023)]
[Proposed Rules]
[Pages 44852-45019]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2023-14199]



[[Page 44851]]

Vol. 88

Thursday,

No. 133

July 13, 2023

Part II





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; Proposed Rule

  Federal Register / Vol. 88 , No. 133 / Thursday, July 13, 2023 / 
Proposed Rules  

[[Page 44852]]


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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: Proposed rule; request for comments; notice of public hearings.

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SUMMARY: The Mine Safety and Health Administration (MSHA) proposes to 
amend its existing standards to better protect miners against 
occupational exposure to respirable crystalline silica, a carcinogenic 
hazard, and to improve respiratory protection for all airborne hazards. 
MSHA has preliminarily determined that under the Agency's existing 
standards, miners at metal and nonmetal mines and coal mines face a 
risk of material impairment of health or functional capacity from 
exposure to respirable crystalline silica. MSHA proposes to set the 
permissible exposure limit 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, for all 
miners. MSHA's proposal would also include other requirements to 
protect miner health, such as exposure sampling, corrective actions to 
be taken when miner exposure exceeds the permissible exposure limit, 
and medical surveillance for metal and nonmetal miners. Furthermore, 
the proposal would replace existing requirements for respiratory 
protection and incorporate by reference ASTM F3387-19 Standard Practice 
for Respiratory Protection. The proposed uniform approach to respirable 
crystalline silica occupational exposure and improved respiratory 
protection for all airborne hazards would significantly improve health 
protections for all miners and lower the risk of material impairment of 
health or functional capacity.

DATES: Written comments. Written comments, including comments on the 
information collection requirements described in this preamble, must be 
received or postmarked by midnight Eastern Time on August 28, 2023.
    Public Hearings. MSHA will hold two public hearings on August 3, 
2023 in Arlington, Virginia and August 21, 2023 in Denver, Colorado. 
For more information on the public hearings, see SUPPLEMENTARY 
INFORMATION.

ADDRESSES: All submissions must include RIN 1219-AB36 or Docket No. 
MSHA-2023-0001. You should not include personal or proprietary 
information that you do not wish to disclose publicly. If you mark 
parts of a comment as ``business confidential'' information, MSHA will 
not post those parts of the comment. Otherwise, MSHA will post all 
comments without change, including any personal information provided. 
MSHA cautions against submitting personal information.
    You may submit comments and informational materials, clearly 
identified by RIN 1219-AB36 or Docket Id. No. MSHA-2023-0001, by any of 
the following methods:
    Federal E-Rulemaking Portal: https://www.regulations.gov. Follow 
the online instructions for submitting comments.
    Email: [email protected]. Include ``RIN 1219-AB36'' in the 
subject line of the message.
    Regular Mail: MSHA, Office of Standards, Regulations, and 
Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia 
22202-5450.
    Hand Delivery or Courier: MSHA, Office of Standards, Regulations, 
and Variances, 201 12th Street South, Suite 4E401, Arlington, Virginia, 
between 9:00 a.m. and 5:00 p.m. Monday through Friday, except Federal 
holidays. Before visiting MSHA in person, call 202-693-9440 to make an 
appointment. Special health precautions may be required.
    Facsimile: 202-693-9441. Include ``RIN 1219-AB36'' in the subject 
line of the message.
    Information Collection Requirements. Comments concerning the 
information collection requirements of this proposed rule must be 
clearly identified with ``RIN 1219-AB36'' or ``Docket No. MSHA-2023-
0001,'' and sent to MSHA by one of the methods previously explained.
    Docket. For access to the docket to read comments and background 
documents, go to https://www.regulations.gov. The docket can also be 
reviewed in person at MSHA, Office of Standards, Regulations, and 
Variances, 201 12th Street South, Arlington, Virginia, between 9 a.m. 
and 5 p.m. Monday through Friday, except Federal holidays. Before 
visiting MSHA in person, call 202-693-9440 to make an appointment. 
Special health precautions may be required.
    Email Notification. To subscribe to receive an email notification 
when MSHA publishes rulemaking documents in the Federal Register, go to 
https://public.govdelivery.com/accounts/USDOL/subscriber/new.

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: 
    MSHA will hold two public hearings to provide industry, labor, and 
other interested parties with an opportunity to present oral 
statements, written comments, and other information on the proposed 
rule. The public hearings will begin at 9 a.m. local time and end after 
the last presenter speaks on the following dates:

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            Date                       Location           Contact number
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August 3, 2023..............  Mine Safety and Health        202-693-9440
                               Administration, 201 12th
                               Street South, Room 7W202,
                               Arlington, VA 22202.
August 21, 2023.............  Denver Federal Center,        202-693-9440
                               Building 25 Lecture Hall,
                               West 6th Avenue and
                               Kipling Street, Denver,
                               CO 80225.
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    The public hearings will begin with an opening statement from MSHA, 
followed by an opportunity for members of the public to make oral 
presentations. Speakers and other attendees may present information to 
MSHA for inclusion in the rulemaking record. The hearings will be 
conducted in an informal manner. Formal rules of evidence or cross 
examination will not apply.
    A verbatim transcript of each of the proceedings will be prepared 
and made a part of the rulemaking record. Copies of the transcripts 
will be available to the public. MSHA will make the transcript of the 
hearings available at http://www.regulations.gov and on MSHA's website 
at https://arlweb.msha.gov/currentcomments.asp.
    MSHA will accept post-hearing written comments and other 
appropriate information for the record from any interested party, 
including those not presenting oral statements, received by

[[Page 44853]]

midnight (Eastern Time) on August 28, 2023.
    Pre-registration is not required to attend the hearings. Interested 
parties may attend the hearings virtually or in person. Interested 
parties who intend to present testimony at the hearings are asked to 
register in advance on MSHA's website (http://www.msha.gov). Speakers 
will be called in the order in which they signed up. Those who do not 
register in advance will have an opportunity to speak after all those 
who pre-registered have spoken. You may submit hearing testimony and 
documentary evidence, identified by docket number (MSHA-2023-0001), by 
any of the methods previously identified. Additional information on how 
to access the public hearings will be posted when available at https://www.msha.gov/regulations/rulemaking.
    The preamble to the proposed standard follows this outline:

I. Introduction
II. Request for Comments
III. Background
IV. Existing Standards and Implementation
V. Health Effects Summary
VI. Preliminary Risk Analysis Summary
VII. Section-by-Section Analysis
VIII. Technological Feasibility
IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory 
Alternatives
X. Initial Regulatory Flexibility Analysis
XI. Paperwork Reduction Act
XII. Other Regulatory Considerations
XIII. References Cited in the Preamble
XIV. Appendix

Acronyms and Abbreviations

COPD chronic obstructive pulmonary disease
ESRD end-stage renal disease
FEV forced expiratory volume
FVC forced vital capacity
L/min liter 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
NMRD nonmalignant respiratory disease
PEL permissible exposure limit
PMF progressive massive fibrosis
RCMD respirable coal mine dust
REL recommended exposure limit
SiO2 silica
TB tuberculosis
TLV[supreg] Threshold Limit Value
TWA time-weighted average

I. Introduction

    With the passage of the Federal Mine Safety and Health Act of 1977 
(Mine Act), Congress declared that ``the first priority and concern of 
all in the coal or other mining industry must be the health and safety 
of its most precious resource--the miner[.]'' 30 U.S.C. 801(a). In 
furtherance of that clear guiding principle, this proposed rule 
promotes MSHA's mission and statutory mandate to prevent death, 
illness, and injury from mining and promote safe and healthful 
workplaces for U.S. miners. This proposal provides the public with the 
opportunity to comment on the Agency's proposed uniform and streamlined 
regulatory approach to lowering miners' exposure to respirable 
crystalline silica and improving respiratory protection.
    Exposure to silica dust causes adverse health effects, including 
silicosis (acute silicosis, accelerated silicosis, simple chronic 
silicosis, and progressive massive fibrosis (PMF)), nonmalignant 
respiratory diseases (NMRD) (e.g., emphysema and chronic bronchitis), 
lung cancer, and renal diseases. Each of these effects is chronic, 
irreversible, and potentially disabling or fatal. Silica dust is 
generated in most mining activities, including cutting, sanding, 
drilling, crushing, grinding, sawing, scraping, jackhammering, 
excavating, and hauling materials that contain silica, and is found in 
all mines--underground and surface metal and nonmetal (MNM) and coal 
mines. In a mining context, silica exposures may occur in respirable 
dust together with exposures to other airborne contaminants and 
combustion biproducts.
    MSHA's existing standards, established in the early 1970s, help 
protect miners from the most dangerous levels of exposure to respirable 
crystalline silica. However, since their promulgation, scientific 
understanding of respirable crystalline silica toxicity has advanced, 
and the National Institute for Occupational Safety and Health (NIOSH) 
has recommended a respirable crystalline silica exposure level of 50 
[micro]g/m\3\ for workers. In 2016, the Occupational Safety and Health 
Administration (OSHA) established a permissible exposure limit (PEL) of 
50 [micro]g/m\3\ in many industry sectors that it regulates.
    To provide miners with exposure limits consistent with workers in 
other industries and NIOSH's recommendation, and to improve miners' 
health, MSHA proposes to lower its existing exposure limits to 50 
[micro]g/m\3\ for respirable crystalline silica in MNM and coal mines. 
MSHA considered exposure limits below 50 [micro]g/m\3\. However, MSHA 
believes, based on a review of the Agency's available silica sample 
data, that an exposure limit of 25 [micro]g/m\3\ may not be achievable 
for all mines. The proposed PEL would be expressed as a full-shift 
exposure, calculated as an 8-hour time-weighted average (TWA). 
Importantly, a uniform proposed PEL for all mines would make compliance 
simpler--especially for coal mines by eliminating the existing 
respirable dust standard when quartz is present.
    To meet the requirements of the proposed PEL, mine operators would 
have to implement engineering controls, followed by administrative 
controls if supplementary protection is needed. Engineering controls, 
which are most effective, are designed to remove or reduce the hazard 
at the source and could include the installation of proper ventilation 
systems, use of water sprays or wetting agents to suppress airborne 
contaminants, installation of machine-mounted dust collectors to 
capture respirable crystalline silica and other contaminants, and the 
installation of control booths or environmental cabs to enclose 
equipment operators. Administrative controls, which are often less 
effective than engineering controls, are designed to change the way 
miners work. One example would be ensuring that miners safely clean 
dust off their work clothes so that they are not exposed to respirable 
dust after their shift ends.
    MSHA's proposed rule would further protect all miners by requiring 
exposure sampling and corrective actions when miners' exposures exceed 
the proposed PEL, as well as periodic sampling when miners' exposure 
levels meet or exceed the proposed action level. The proposed rule also 
includes medical surveillance requirements for MNM miners (medical 
surveillance requirements already exist for coal miners). Proposed 
medical examinations would include chest X-rays, spirometry, symptom 
assessment, and occupational history and would be provided at no cost 
to the miner.
    Finally, the proposed rule would incorporate by reference an 
updated respiratory protection standard, ASTM F3387-19, ``Standard 
Practice for Respiratory Protection'' (ASTM F3387-19), for respirable 
crystalline silica and all other regulated airborne contaminants. This 
voluntary consensus standard represents up-to-date advancements in 
respiratory protection technologies, practices, and techniques, 
including proper selection, use, and maintenance of respirators. The 
proposed incorporation of ASTM F3387-19 by reference would better 
protect all miners from airborne hazards. However, respiratory 
protection should only be relied upon as an exposure control measure in 
limited situations and on a temporary basis, and to supplement 
engineering controls, followed by administrative controls.
    Taken together, all elements of the proposed rule are 
technologically and economically feasible. MSHA's 2014

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final rule, Lowering Miners' Exposure to Respirable Coal Mine Dust, 
Including Continuous Personal Dust Monitors (Coal Dust Rule) improved 
health protections for coal miners by lowering exposure limits to 
respirable coal mine dust and establishing sampling requirements that 
included the use of a Continuous Personal Dust Monitor (79 FR 24813, 
May 1, 2014). Coal mine operators have generally achieved compliance 
with the respirable dust standards primarily by implementing or 
adjusting existing engineering controls. Coal mine operators' sampling 
data and MSHA's compliance data show that operators have lowered coal 
miners' exposures to respirable coal mine dust and to respirable 
crystalline silica. Data show that average exposures in coal mines are 
below the proposed PEL of 50 [mu]g/m\3\, and therefore, corrective 
measures would often not be needed. Similarly, for MNM miners, MSHA 
data also show that most exposures to respirable crystalline silica are 
below the proposed PEL. However, at MNM and coal mines where elevated 
exposures are found, operators will be able to reduce exposures to the 
proposed PEL through some combination of properly maintaining existing 
engineering controls, implementing new engineering controls, and 
requiring safe work practices. Mines and laboratories will be able to 
meet exposure monitoring requirements with existing validated and 
widely used sampling and analytical methods. The proposed revision to 
the respiratory protection standard is technologically feasible because 
MSHA's existing respiratory protection requirements for selecting, 
fitting, using, and maintaining respiratory protection include similar 
requirements.
    MSHA's Preliminary Risk Analysis (PRA) suggests that exposure 
consistent with a lower proposed PEL of 50 [micro]g/m\3\ would deliver 
many health benefits to miners who currently experience exposures above 
the proposed PEL by reducing the likelihood of respirable crystalline 
silica-related diseases. For those miners working only under the 
proposed PEL, MSHA estimates that the proposed rule would result in a 
total of 799 lifetime avoided deaths (63 in coal and 736 in MNM mines) 
and 2,809 lifetime avoided morbidity cases (244 in coal and 2,566 in 
MNM mines) over a 60-year period. MSHA expects full implementation and 
compliance to reduce lifetime mortality risk due specifically to silica 
exposures by 9.5 percent and to reduce silicosis morbidity risk by 41.9 
percent. The latter statistic is particularly important to coal miners 
given surveillance findings noted by the National Academies of 
Sciences, Engineering, and Medicine that severe pneumoconiosis where 
respirable crystalline silica is likely an important contributor is 
presenting in relatively young miners, sometimes in their late 30's and 
early 40's.
    MSHA's economic analysis estimates that the proposed respirable 
crystalline silica rule would cost an average of $56.1 million per year 
in 2021 dollars at an undiscounted rate, $57.6 million at a 3 percent 
discount rate, and $59.9 million at a 7 percent discount rate. Based on 
the results of the Preliminary Regulatory Impact Analysis (PRIA), MSHA 
estimates that the proposed rule's benefits would exceed its costs, 
with or without discount rates. Monetized benefits are estimated from 
avoidance of 410 deaths related to NMRD, silicosis, ESRD, and lung 
cancer and 1,420 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 $212.8 million at 
an undiscounted rate, $118.2 million at a 3 percent discount rate, and 
$36.3 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 or . . . adversely affect 
in a material way the economy, a sector of the economy, productivity, 
competition, jobs, the environment, public health or safely, or State, 
local, or tribal governments or communities.'' The Office of Management 
and Budget has determined that the proposed rule is significant within 
the meaning of E.O. 12866 Section 3(f)(1).
    The proposed rule would strengthen MSHA's existing regulatory 
framework. It would establish a uniform proposed PEL that provides all 
MNM and coal miners with the same exposure limits for respirable 
crystalline silica consistent with exposure limits that other U.S. 
workers currently receive in non-mining industries. It would update 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. The proposed rule would also include requirements 
for all MNM operators to provide medical surveillance in the form of a 
medical examination regime similar to what coal miners already receive. 
Cumulatively, the proposed provisions would lower miners' risk 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. Request for Comments

    MSHA requests comments on the proposed rule and all relevant 
issues, including the review and conclusions of the health effects 
discussion, preliminary risk analysis, feasibility analysis, 
preliminary regulatory impact analysis and regulatory alternatives, and 
preliminary regulatory flexibility analysis. While MSHA invites 
comments on any aspect of its proposed rule and related documents, the 
Agency particularly seeks information and data in response to questions 
posed in this section and any other aspect of this proposed rule. 
Instructions for submitting and viewing comments are provided under the 
DATES heading. MSHA will consider all timely comments and may change 
the proposed rule based on such comments.
    MSHA requests that commenters organize their comments, to the 
extent possible, around the following numbered questions. The Agency is 
interested in receiving responses to the listed questions and any 
information or data supporting the responses.

Health Effects

    1. In the standalone, background document entitled ``Health Effects 
of Respirable Crystalline Silica'' and as summarized in Section V. 
Health Effects Summary of this preamble, MSHA has made a preliminary 
determination that miners' exposure to respirable crystalline silica 
presents a risk of material health impairment due to the risk of 
developing silicosis, NMRD, lung cancer, and renal disease, based on 
its extensive review of the health effects literature. MSHA requests 
comments on this preliminary determination and its literature review, 
which draws heavily from the review conducted by OSHA for its 2016 
rulemaking. Are there additional adverse health effects that should be 
included or more recent literature that offers a different perspective? 
MSHA requests that commenters submit information, data, or additional 
studies or their citations. Please be specific regarding the basis for 
any recommendation to include additional adverse health effects.

Preliminary Risk Analysis

    2. In the standalone, background document entitled ``Preliminary 
Risk Analysis'' and as summarized in Section VI. Preliminary Risk 
Analysis Summary

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of this preamble, MSHA relied on risk models that OSHA used in support 
of its 2016 respirable crystalline silica final rule. Does the context 
of the MSHA rule suggest that the model would benefit from changes? If 
so, please describe both the justification for those changes and the 
likely impact on the final risk estimates. Are there additional studies 
or sources of data that MSHA should consider? What is the rationale for 
recommending the use of these additional studies or data?
    3. MSHA's risk analysis of lung cancer mortality uses the exposure-
response model from Miller and MacCalman (2010) instead of Steenland et 
al. (2001a), on which OSHA's risk assessment of lung cancer mortality 
was based. MSHA uses Miller and MacCalman (2010) for several reasons. 
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. 
The Agency is requesting comment on MSHA's reliance on the Miller and 
MacCalman (2010) study in assessing lung cancer mortality. Please 
provide any other studies or information that MSHA should take into 
account in determining the risk of lung cancer mortality among miners.

Technological Feasibility of the Proposed Rule

    4. As discussed in Section VIII. Technological Feasibility of this 
preamble, MSHA has preliminarily determined that it is technologically 
feasible for mine operators to conduct air sampling and analysis and to 
achieve the proposed 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, and can be monitored. MSHA has also determined that 
administrative controls, used to supplement engineering controls, can 
further reduce and maintain exposures at or below the proposed PEL. 
Moreover, MSHA has preliminarily determined the proposed respiratory 
protection practices for respirator use are technologically feasible 
for mine operators to implement. MSHA requests comments on these 
preliminary conclusions. What methods have you used that proved 
effective in reducing miners' exposure to respirable crystalline silica 
in mining operations? Please explain how those methods were effective 
in reducing miners' exposures. To what extent do existing controls that 
reduce exposure to other airborne hazards (e.g., coal dust, diesel 
particulate matter) already reduce exposures to respirable crystalline 
silica below the proposed PEL? To what extent does the proposed rule 
including the PEL facilitate MSHA's workplace health and safety goals? 
Please provide supporting information, such as quantitative data if 
available.
    5. MSHA has determined that the proposed medical surveillance 
requirements for MNM are technologically feasible. MSHA requests 
comments on this preliminary conclusion. Please provide supporting 
information, such as quantitative data if available.

Preliminary Regulatory Impact Analysis and Regulatory Alternatives

    6. In the standalone background document entitled ``Preliminary 
Regulatory Impact Analysis'' and as summarized in Section IX. Summary 
of Preliminary Regulatory Impact Analysis and Regulatory Alternatives 
of this preamble, MSHA developed estimated costs of compliance with the 
proposed rule and estimated monetized benefits associated with averted 
cases of respirable crystalline silica-related diseases. MSHA requests 
comments on the methodologies, baseline, assumptions, and estimates 
presented in the Preliminary Regulatory Impact Analysis. Please provide 
any data or quantitative information that may be useful in evaluating 
the estimated costs and benefits associated with the proposed rule.
    7. MSHA considered two regulatory alternatives in developing the 
proposed rule discussed in Section IX. Summary of Preliminary 
Regulatory Impact Analysis and Regulatory Alternatives. In the 
regulatory alternatives presented, MSHA discussed alternatives to the 
proposed PEL, action level, sampling requirements, and semi-annual 
evaluations. MSHA requests comments on these and other regulatory 
alternatives and information on any other alternatives that the Agency 
should consider, including different average working-life spans and 
different average shift lengths. Please provide supporting information 
about how these alternatives could affect miners' protection from 
respirable crystalline silica exposure and affect mine operators' 
costs.

Initial Regulatory Flexibility Analysis

    8. As summarized in Section X. Initial Regulatory Flexibility 
Analysis of this preamble, MSHA examined the impact of the proposed 
rule on small mines in accordance with the Regulatory Flexibility Act. 
MSHA estimated that small-entity controllers would be expected to 
incur, on average, additional regulatory costs equaling approximately 
0.122 percent of their revenues (or $1,220 for every $1 million in 
revenues). MSHA is interested in how the proposed rule would affect 
small mines, including their ability to comply with the proposed 
requirements. Please provide information and data that supports your 
response. If you operate a small mine, please provide any projected 
impacts of the proposal on your mine, including the specific rationale 
supporting your projections.

Scope and Effective Date

    9. MSHA is proposing a unified regulatory and enforcement framework 
for controlling miners' exposures to respirable crystalline silica for 
the mining industry. MSHA requests comments on this unified regulatory 
and enforcement framework. MSHA requests the views and recommendations 
of stakeholders regarding the scope of proposed part 60, which would 
include all surface and underground MNM and coal mines. MSHA requests 
comments on whether separate standards should be developed for the MNM 
mining industry and the coal mining industry. Please provide supporting 
information.
    10. MSHA is proposing that the final rule would be effective 120 
days after its publication in the Federal Register. This period is 
intended to provide mine operators time to evaluate existing 
engineering and administrative controls, update their respiratory 
protection programs, and prepare to comply with other provisions of the 
rule including recordkeeping requirements. Please provide your views on 
the proposed effective date. In your response, please include the 
rationale for your position.

[[Page 44856]]

Definitions

    11. MSHA requests comments on the proposed action level. 
Stakeholders should provide specific information and data in support of 
or against a proposed action level. Stakeholders should include a 
discussion of how the use of a proposed action level would impact their 
mines, including the cost of monitoring respirable crystalline silica 
above the proposed action level, and other relevant information. Please 
provide supporting information.
    12. MSHA requests comments on the proposed definition for 
``objective data.'' Is it appropriate to allow mine operators to use 
objective data instead of a second baseline sample? Please provide 
supporting information.

Proposed Permissible Exposure Limit

    13. MSHA is proposing a PEL for respirable crystalline silica of 50 
[mu]g/m\3\ for a full-shift exposure, calculated as an 8-hour TWA for 
MNM and coal miners. MSHA has made a preliminary determination that the 
proposed PEL would reduce miners' risk of suffering material impairment 
of health or functional capacity over their working lives. MSHA seeks 
the views and recommendations of stakeholders on the proposed PEL. MSHA 
solicits comments on the approach of having a standalone PEL and 
whether to eliminate the reduced standard for total respirable dust 
when quartz is present at coal mines. Please provide evidence to 
support your response.
    14. MSHA is proposing a PEL of 50 ug/m\3\ and an action level of 25 
[mu]g/m\3\ for respirable crystalline silica exposure. Which proposed 
requirements should be triggered by exposure at, above, or below the 
proposed action level? Please provide supporting information.

Methods of Compliance

    15. MSHA requests comments on the proposed prohibition against 
rotation of miners as an administrative control. Please include a 
discussion of the potential effectiveness of this non-exposure approach 
and its impact on miners at specific mines. Please provide supporting 
information.
    16. MSHA requests comments on the proposed requirement that mine 
operators must install, use, and maintain feasible engineering and 
administrative controls to keep miners' exposures to respirable 
crystalline silica below the proposed PEL. Please provide supporting 
information.

Proposed Exposure Monitoring

    17. MSHA requests comments and information from stakeholders 
concerning the proposed approaches to monitoring exposures, and other 
approaches to accurately monitor miner exposure to respirable 
crystalline silica in MNM and coal mines. Please provide supporting 
information and data.
    18. MSHA proposes to require mine operators to collect a respirable 
crystalline silica sample for a miner's regular full shift during 
typical mining activities. Many potential sources of respirable 
crystalline silica are present only when the mine is operating under 
typical conditions. MSHA requests comments on this requirement and 
whether to specify environmental conditions under which samples should 
be taken to ensure that samples accurately reflect actual levels of 
respirable crystalline silica exposure. In MSHA's experience, for 
example, environmental conditions such as precipitation (e.g., rain or 
snow) or wind could affect the actual levels of respirable crystalline 
silica exposure at miners' normal or regular workplaces throughout 
their typical workday. Please provide supporting information and data.
    19. MSHA recognizes that some mining facilities operate seasonally 
or intermittently and that cumulative exposures for miners at these 
facilities may be lower than that of miners working at year-round 
operations. MSHA requests comments on the exposure monitoring approach 
under proposed Sec.  60.12, including the frequency of exposure 
monitoring necessary to safeguard the health of miners at seasonal or 
intermittent operations. Please provide supporting information and 
data.
    20. MSHA is proposing that each mine operator perform baseline 
sampling within 180 days after the rule becomes effective to assess the 
respirable crystalline silica exposure of each miner who is or may 
reasonably be expected to be exposed to respirable crystalline silica. 
MSHA requests comments on this proposed baseline sampling requirement. 
MSHA also requests comment on the ability of service providers used by 
mines such as industrial hygiene suppliers and consultants, and 
accredited laboratories that conduct respirable crystalline silica 
analysis, to meet the demand created by the baseline sampling 
requirements within the proposed timeline. Please include alternative 
approaches that might be equally protective of miners that should be 
implemented for assessing a miner's initial exposure to respirable 
crystalline silica.
    21. MSHA is proposing a requirement that mine operators 
qualitatively evaluate every 6 months any changes in production, 
processes, engineering controls, personnel, administrative controls, or 
other factors, beginning 18 months after the effective date. MSHA 
requests comments on the timing of the proposed semi-annual evaluation 
requirements, and in particular, whether miners would possibly be 
exposed unnecessarily to respirable crystalline silica levels above the 
PEL due to the gap between the effective date and the proposed 
requirements. Please provide supporting information.
    22. MSHA has determined that most occupations related to extraction 
and processing would meet the ``reasonably be expected'' threshold for 
baseline sampling. MSHA recognizes that some miners may work in areas 
or perform tasks where exposure is not reasonably expected, if at all. 
MSHA solicits comments on the 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 baseline 
sampling. Please provide supporting information.
    23. MSHA is proposing that mine operators would not be required to 
conduct periodic sampling if the baseline sampling result, together 
with another sampling result or objective data, as defined in proposed 
Sec.  60.2, confirms miners' exposures are below the proposed action 
level. MSHA seeks comments on this proposal. Please provide supporting 
information and data.
    24. MSHA is proposing that mine operators conduct periodic sampling 
within 3 months where the most recent sampling indicates miner 
exposures are at or above the proposed action level but at or below the 
proposed PEL and continue to sample within 3 months of the previous 
sampling until two consecutive samplings indicate that miner exposures 
are below the action level. MSHA solicits comments on the proposed 
frequency for periodic sampling, including whether the consecutive 
samples should be at least 7 days apart. Please provide supporting 
information and data.
    25. MSHA is proposing that mine operators may discontinue periodic 
sampling when two consecutive samples indicate that miner exposures are 
below the proposed action level. MSHA requests comments on this 
proposal. Please provide supporting information and data.
    26. MSHA is proposing that mine operators conduct semi-annual 
evaluations to evaluate whether any changes in production, processes, 
engineering controls, personnel, administrative controls, or other 
factors may reasonably be expected to result in

[[Page 44857]]

new or increased respirable crystalline silica exposures. Please 
provide comments on this proposal, as well as alternative approaches 
that would be appropriate for evaluating any potential new or increased 
respirable crystalline silica exposures. Please provide supporting 
information and data.
    27. MSHA is proposing that miners' exposures are measured using 
personal breathing-zone air samples for MNM operations and occupational 
environmental samples collected in accordance with Sec. Sec.  
70.201(c), 71.201(b), or 90.201(b) for coal operations. MSHA requests 
comments on this proposal. Please provide supporting information and 
data.
    28. MSHA is proposing the use of representative sampling. Where 
several miners perform the same task on the same shift and in the same 
work area, the mine operator may sample a representative fraction of 
miners to meet the proposed exposure monitoring requirements. MSHA 
seeks comments on the use of representative sampling. Please provide 
supporting information and data.
    29. MSHA is proposing that mine operators use laboratories 
accredited to ISO/IEC 17025 ``General requirements for the competence 
of testing and calibration laboratories,'' 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.'' MSHA solicits comments on this 
proposal. Are there additional requirements that should be incorporated 
into this proposal to ensure accurate sample analysis methods? Please 
provide supporting information and data.
    30. MSHA seeks comments on the proposal that mine operators ensure 
that laboratories evaluate all respirable crystalline silica samples 
using respirable crystalline silica analytical methods specified by 
MSHA, NIOSH, or OSHA. Are there additional requirements that should be 
incorporated into this proposal to ensure accurate sample analysis? 
Please provide supporting information and data.
    31. MSHA seeks comments and information on mine operator and 
stakeholder experience using NIOSH's rapid field-based quartz 
monitoring (RQM) monitors for determining miners' exposures to 
respirable crystalline silica. Please provide any information and data.

Proposed Medical Surveillance for Metal and Nonmetal Miners

    32. MSHA is proposing to require medical surveillance for MNM 
miners. Medical surveillance is already required for coal miners under 
30 CFR 72.100 and has played an important role in tracking the burden 
of pneumoconiosis in coal miners but is not currently required for MNM 
miners. MSHA's proposal would require MNM mine operators to provide 
each miner new to the mining industry with an initial medical 
examination and a follow-up examination no later than 3 years after the 
initial examination, at no cost to the miner. It would also require MNM 
mine operators to provide examinations for all miners at least every 5 
years, which would be voluntary for miners. Is there an alternative 
strategy or schedule, such as voluntary initial or follow-up 
examinations, tying the medical surveillance requirement to miners 
reasonably expected to be exposed to any level of silica or to the 
action level that would be more appropriate for new MNM miners? Should 
the rule make each 5-year examination mandatory? Should the 5-year 
examination be mandatory for coal mine operators as well? Please 
provide data or cite references to support your position.
    33. MSHA's proposed medical surveillance requirements for MNM 
miners do not include some requirements that are in MSHA's existing 
medical surveillance requirements for coal mine operators in 30 CFR 
72.100. For example, Sec.  72.100 requires coal mine operators to use 
NIOSH-approved facilities for medical examinations. Should MNM 
operators be required to use NIOSH-approved facilities for medical 
examinations? Coal mine operators also are required to submit for 
approval to NIOSH a plan for providing miners with the examinations 
specified. This is because NIOSH administers medical surveillance for 
coal miners with requirements for coal operators, but not MNM 
operators, in NIOSH standards (42 CFR part 37). Should the plan 
requirements be extended to MNM operators? However, the proposed 
requirements also include some requirements for MNM operators that are 
not included for coal operators. For example, the proposed provisions 
require operators of MNM mines to provide MNM miners with periodic 
medical examinations performed by physicians or other licensed health 
care professionals (PLHCP) or specialists including a history and 
physical examination focused on the respiratory system, a chest X-ray, 
and a spirometry test. The proposed rule also requires a written 
medical opinion be provided by the PLHCP or specialist to the mine 
operator regarding the miner's ability to wear a respirator. MSHA seeks 
comment on the differences between the medical surveillance 
requirements for MNM operators in this proposed rule and the existing 
medical surveillance requirements for coal mine operators in Sec.  
72.100. MSHA also seeks comment on how best to collect health 
surveillance data from PLHCPs and specialists to track MNM miners' 
health, for example how to know when pneumoconiosis cases occur. MSHA 
seeks comments on alternative approaches to scheduling periodic medical 
surveillance. MSHA proposes to require operators to keep medical 
surveillance information for the duration of a miner's employment plus 
6 months. The Agency seeks comments on this proposed requirement and on 
any alternative recordkeeping schedules that would be appropriate. 
Please provide supporting information.
    34. MSHA's proposed medical surveillance requirements for MNM 
miners would require operators of MNM mines to provide miners with 
periodic medical examinations performed by PLHCP or specialists, 
including a history and physical examination focused on the respiratory 
system, a chest X-ray, and a spirometry test. MSHA seeks comment on 
whether use of any new diagnostic technology (e.g., high-resolution 
computed tomography) for the purposes of medical surveillance should be 
used.
    35. MSHA's proposed medical surveillance requirements would require 
that the MNM mine operator provide a mandatory follow-up examination to 
the miner no later than 3 years after the miner's initial medical 
examination. If a miner's 3-year follow-up examination shows evidence 
of a respirable crystalline silica-related disease or decreased lung 
function, the operator would be required to provide the miner with 
another mandatory follow-up examination with a specialist within 2 
years. For examinations that show evidence of disease or decreased lung 
function, MSHA seeks comment on how, and to whom, test results should 
be communicated.
    36. MSHA requests comments as to whether the proposed provisions 
should include a medical removal 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 examinations has the

[[Page 44858]]

option to work in 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 
applicable standard. Under part 90, coal miners are entitled to 
retention of pay rate, future actual wage increases, and future work 
assignment, shift and respirable dust protection. MSHA seeks comment on 
whether this medical removal option should be provided to MNM miners. 
What would be the economic impact of providing MNM miners a medical 
removal option? Please provide supporting information and data.

Proposed Respiratory Protection Standard

    37. MSHA requests comments concerning the temporary, non-routine 
use of respirators and whether there are other instances or occupations 
in which the Agency should allow the use of respirators as a 
supplemental control. Please discuss any impacts on particular mines 
and mining conditions and the cost of air-purifying respirators, if 
applicable. MSHA also solicits comments on the proposed requirement 
that affected miners wear respiratory protection to maintain protection 
during temporary and non-routine use of respirators. Please provide 
supporting information.
    38. MSHA is proposing to incorporate by reference ASTM F3387-19, 
published in 2019. Whenever respiratory protective equipment is needed, 
mine operators would be required to follow practices for program 
administration, standard operating procedures, medical evaluations, 
respirator selection, training, fit testing, and maintenance, 
inspection, and storage in accordance with the requirements of ASTM 
F3387-19. Beyond these elements, MSHA is proposing to provide operators 
the flexibility to select the elements in ASTM F3387-19 that are 
applicable to their practices of respirator use at their mines. Should 
mine operators have the flexibility to choose the ASTM F3387-19 
elements that are appropriate for their mine-specific hazards because 
the need for respirators may vary due to the variability of mining 
processes, activities, airborne hazards, and commodities mined? What, 
specifically, do you think should factor into the determination of what 
is applicable? MSHA seeks comments on its proposed approach and the 
impact it would have on mine operators and on miners' life and health.
    39. ASTM F3387-19 identifies a variety of respiratory protection 
practice elements. MSHA proposes to require certain minimally 
acceptable program elements: program administration; standard operating 
procedures; medical evaluations; respirator selection; training; fit 
testing; and maintenance, inspection, and storage. Please comment on 
whether these are the appropriate elements to require, or if there are 
any other elements of ASTM F3387-19 that should be minimally included 
in any respiratory protection program. MSHA also welcomes comments on 
whether it would be appropriate to require the standard in its 
entirety. Please identify those elements that would ensure that 
approved respirators are selected, fitted, used, cleaned, and 
maintained so that the life and health of miners are safeguarded. MSHA 
also seeks data and information on the impact these changes would have 
on mine operators, especially smaller operators. What would be the 
economic impact if all or parts of ASTM F3387-19 were required 
respirator program elements? Please be specific with your response and 
provide details on respirator use at your mine to include information 
and data on mining processes and environmental conditions; level of 
exposures to airborne contaminants; frequency and duration of 
exposures; type and amount of work or physical labor, including 
frequency and duration; and medical evaluation on respirator use, if 
applicable.

Recordkeeping Requirements

    40. MSHA is proposing to require recordkeeping for records of 
evaluations, records of samplings, records of corrective actions, and 
written determination records received from a PLHCP. The proposed 
rule's recordkeeping requirements are discussed in the Section-by-
Section Analysis section of this Preamble. MSHA seeks comment on the 
utility of these recordkeeping requirements as well as the costs of 
making and maintaining these records. Please provide supporting 
information.

Training Requirements

    41. MSHA requests the views and recommendations of stakeholders 
regarding whether training requirements for miners should be included 
in proposed part 60. Please provide supporting information and data.

Conforming Changes

    42. MSHA requests comments on the proposed conforming changes to 
remove the reduced coal dust standard from 30 CFR and the potential 
impact on coal mines and miners and on whether to retain the reduced 
standard for part 90 miners. Please provide supporting information.
    43. MSHA is not proposing to adopt a similar approach as the OSHA 
Table 1 for the construction industry, where MSHA would prescribe 
specific exposure control methods for task-based work practices when 
working with materials containing respirable crystalline silica. See 29 
CFR 1926.1153(c)(1). MSHA requests comments on specific tasks and 
exposure control methods appropriate for a Table 1-approach for the 
mining industry that also would adequately protect miners from risk of 
exposure to respirable crystalline silica. Please provide specific 
rationale and supporting information, including data on how such an 
approach would be implemented.

III. Background

    The purpose of this proposed rule is to reduce miners' risk of 
developing occupational lung disease and other diseases caused by 
exposure to respirable crystalline silica and to better protect all 
miners from occupational exposure to airborne hazards. In promulgating 
mandatory standards dealing with toxic materials or harmful physical 
agents, MSHA is required 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 . . .'' 30 
U.S.C. 811(a)(6)(A).

A. Statutory Authority

    The statutory authority for this proposal 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

[[Page 44859]]

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, as appropriate, mandatory health 
standards to address toxic materials or harmful physical agents. Under 
Section 101(a), standards must protect lives and prevent injuries in 
mines and be ``improved'' over any standard that it replaces or 
revises. 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 OSH Act at 29 U.S.C. 652 with 
the Mine Act at 30 U.S.C. 811(a) 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'' 
(emphasis in original)).
    The Secretary must set standards to assure, based on the best 
available evidence, that no miners 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. However, 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. Instead, ``when MSHA itself weighs the 
evidence before it, it does so in light of its congressional mandate.'' 
Id.
    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). In general, section 103(h) requires that every mine operator 
establish and maintain records, make reports, and provide this 
information, if required by the Secretary. Id. Also, 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 proposal to lower the exposure limits for respirable 
crystalline silica and adopt an integrated monitoring approach across 
all mining sectors and to update the existing respiratory protection 
requirements would fulfill Congress' direction by preventing miners 
from suffering material impairment of health or functional capacity 
caused by exposure to respirable crystalline silica and other airborne 
contaminants.

B. 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--several different structures with the 
same chemical composition. The most common form of crystalline silica 
found in nature is quartz, but cristobalite and tridymite may also be 
found 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 is 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 occurs 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 may therefore lead to miner exposure.
    Inhaled small particles of silica dust can be deposited throughout 
the lungs. A large number of crystalline silica particles can reach and 
remain in the deep lung (i.e., alveolar region), although some small 
particles are 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 for 
prolonged periods result in a variety of cellular responses that may 
lead to pulmonary disease. 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 III-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.\1\ Table III-1 shows 
that a majority of MNM mines produce sand and gravel, while the largest 
number of MNM miners work at metal mines (not

[[Page 44860]]

including MNM contract workers (i.e., independent contractors and 
employees of independent contractors who are engaged in mining 
operations)).
---------------------------------------------------------------------------

    \1\ Commodities such as sand, gravel, silica, and/or stone for 
example are used in road building, concrete construction, 
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] TP13JY23.000

    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, as well as other components (IARC, 
1997). These activities include the general mining activities 
previously mentioned (e.g., cutting, sanding, drilling, crushing, and 
hauling materials), as well as roof bolter operations, continuous 
mining machine operations, longwall mining, and other activities. Table 
III-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).

IV. Existing Standards and Implementation

    MSHA has maintained health standards to protect MNM and coal miners 
from excessive exposure to respirable crystalline silica for decades. 
MSHA's existing standards, established in the early 1970s, limit 
miners' exposures to respirable crystalline silica. These standards 
require mine operators to monitor occupational exposures to respirable 
crystalline silica and 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 respiratory 
protection in limited situations and on a temporary basis. The existing 
standards for MNM and coal mines differ in some respects, including 
exposure limits and monitoring. 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 them in recent years.

A. Existing Standards--Metal and Nonmetal Mines

    MSHA's existing standards for exposure to airborne contaminants, 
including respirable crystalline silica, in MNM mines are found in 30 
CFR part 56, subpart D (Air Quality and Physical Agents), and 30 CFR 
part 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 TLV[supreg] for quartz is calculated by 
dividing the percent of respirable quartz plus 2, into the number 10. 
The TLV[supreg] for cristobalite and the TLV[supreg] for tridymite, 
respectively, are calculated by multiplying the same mass formula by 
one-half using the percentages of either cristobalite or tridymite 
found in the sample. Thus, 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 [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\.

[[Page 44861]]

    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, examining dust control system and 
ventilation system maintenance, and reviewing 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 to harmful airborne contaminants and the effectiveness of 
existing controls in reducing such 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 these efforts were successful. Re-surveying should be 
done as frequently as necessary to ensure that the implemented control 
measures remain adequate. MSHA's determination of whether a mine 
operator has surveyed frequently enough is based on several factors, 
including whether sampling results comply with the permissible exposure 
limit, whether there have been changes in the mining operation or 
process, and whether controls such as local exhaust ventilation systems 
need routine or special maintenance.
    Exposure Controls. MSHA's existing standards for controlling a 
miner's exposure to harmful airborne contaminants (Sec. Sec.  56.5005 
and 57.5005) require, if feasible, prevention of contamination, removal 
by exhaust ventilation, or dilution with uncontaminated air. The use of 
respiratory protective equipment is also allowed under specified 
circumstances such as when engineering controls are being developed or 
are not feasible. When respiratory protective equipment is used, the 
operator must have a respiratory protection program consistent with the 
requirements of American National Standards Practices for Respiratory 
Protection ANSI Z88.2-1969.
    Consistent with widely accepted industrial hygiene principles and 
NIOSH's recommendations, MSHA requires the use of engineering controls, 
supplemented by administrative controls, in its enforcement for the 
control of occupational exposure to respirable crystalline silica and 
other airborne contaminants (NIOSH, 1974). Engineering controls 
designed to remove or reduce the hazard at the source are the most 
effective. Examples of engineering controls include the installation of 
proper ventilation systems, use of water sprays or wetting agents to 
suppress airborne contaminants, installation of machine-mounted dust 
collectors to capture respirable crystalline silica and other 
contaminants, and the installation of control booths or environmental 
cabs to enclose equipment operators.
    Although 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. In applying administrative controls, mine 
operators can direct miners to perform certain activities in specific 
manners. For instance, as an administrative control, operators can 
specify adequate housekeeping procedures for miners to clean spills or 
handle contaminated clothing which could reduce occupational exposure 
to airborne contaminants, including respirable crystalline silica.
    In addition, respiratory protective equipment can be used in 
controlling miners' exposures to airborne contaminants, including 
respirable crystalline silica, on a temporary basis or under non-
routine, limited conditions. The use of respiratory protection is, 
however, considered to be a supplement, not an alternative to any 
engineering or administrative control, in reducing or eliminating a 
miner's exposure to airborne contaminants including respirable 
crystalline silica.
    Under the existing standards in Sec. Sec.  56.5005 and 57.5005, in 
circumstances where engineering controls are not yet developed or where 
it is necessary for miners to enter hazardous atmospheres to establish 
controls or to perform non-routine maintenance or investigation, a 
miner using appropriate respiratory protection ``may work for 
reasonable periods of time'' in concentrations of airborne contaminants 
which exceed exposure limits. 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 airborne 
contaminants. Whenever respiratory protection is used, MNM mine 
operators are required to have a respirator program consistent with the 
requirements specified in ANSI Z88.2-1969.

B. Existing Standards--Coal Mines

    Under existing standards, there is no separate standard for 
respirable crystalline silica for coal mines. 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 coal miners. Under these 
respirable dust standards, coal miners' exposures to respirable quartz 
are indirectly regulated through reductions in the overall respirable 
dust 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.\2\ Therefore, 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.
---------------------------------------------------------------------------

    \2\ 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. This 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\. The applicable dust standard, when the equivalent 
concentration of respirable crystalline silica exceeds 100 [micro]g/
m\3\, is computed by dividing the percent of quartz into the number 10.

[[Page 44862]]

The result of this calculation becomes the exposure limit for 
respirable coal mine dust (RCMD), for the sections of the mine 
represented by the sample. Various sections within a mine may have 
different reduced 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. 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\.
    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 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. In addition, respirable dust 
sampling must be representative of respirable dust exposures during a 
normal production shift. Also, sampling 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, from the start of their work day to the end of their work day, 
in their normal work locations.\3\
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    \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.
---------------------------------------------------------------------------

    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. Similar to the MNM standards, engineering 
and environmental controls include the use of dust collectors, water 
sprays, and ventilation controls. 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 
reduced RCMD standard, they are required to take corrective 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. Corrective actions can include increasing air flow, 
improving ventilation controls, repairing and maintaining existing dust 
suppression controls, adding water sprays or other controls, cleaning 
dust filters or collectors more frequently, or repositioning the miner 
away from the dust source.
    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 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

    MSHA collects respirable dust samples at mines and analyzes them 
for respirable crystalline silica to determine whether the respirable 
crystalline silica exposure limits are met and whether exposure 
controls are adequate. This section describes the respirable dust 
samples collected at MNM and coal mines in recent years and presents 
the results of the sample data analyses.
1. Respirable Dust Sample Collection
    This subsection offers a brief description of how MSHA samples for 
respirable crystalline silica under the existing standards. Upon their 
arrival at mines, MSHA inspectors determine which areas of the mine and 
which miners to select for respirable dust sampling. At MNM mines, the 
MSHA inspector often determines sampling locations based on sample 
results from previous inspections and on the inspector's onsite 
observations of work practices and work areas. At coal mines, the MSHA 
inspector conducts sampling among the occupations or from the work 
areas that are specified for operator sampling under 30 CFR parts 70, 
71, and 90. Generally speaking, MSHA inspectors collect respirable dust 
samples from the common occupations during typical and normal 
activities at the mine and from the positions that are commonly known 
to have the highest concentration of respirable dust.
    After identifying which miners and which areas at the mine will be 
sampled for respirable dust, MSHA inspectors place gravimetric samplers 
on the selected miners or at the selected locations. Gravimetric 
samplers consist of a portable air-sampling pump connected to a 
particle-size separator (i.e., cyclone) and collection medium (i.e., 
filter). MSHA inspectors use Dorr-Oliver 10-mm nylon cyclones operated 
at a 1.7 liters per minute (L/min) flow rate for MNM mine sampling and 
at a 2.0 L/min flow rate (reported as MRE-equivalent concentrations) 
for coal mine sampling.\4\ For the entire duration of the work shift, 
the gravimetric sampler captures air from the breathing zone of each 
selected miner or occupation and from each selected work area.
---------------------------------------------------------------------------

    \4\ This type of sampling equipment was developed to separate 
the airborne particles by size in a manner similar to the size-
selective deposition and retention characteristics of the human 
respiratory system. It is important to note that size-selective 
sampling does not measure the deposition of respirable particles in 
the lung. Rather, it provides a measure of the particulate mass 
available for deposition to the deep lung during breathing (Raabe 
and Stuart, 1999).
---------------------------------------------------------------------------

    MSHA inspectors use the full-shift sampling approach. When miners 
work longer than an 8-hour shift, which is common, those miners are 
sampled continuously throughout the extended work shifts. 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, the inspectors 
send the cassettes containing the full-shift respirable dust samples to 
the MSHA Laboratory for analysis.

[[Page 44863]]

2. Respirable Dust Sample Analysis
    The MSHA Laboratory analyzes inspectors' respirable dust samples, 
following its standard operating procedures (SOPs) summarized below.\5\ 
Any samples that are broken, torn, or visibly wet are voided and 
removed before analysis. Once weighing of the samples is completed, 
samples are again screened based on mass gain and examined for 
validity. 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.\6\
---------------------------------------------------------------------------

    \5\ 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.
    \6\ 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): 
X-ray diffraction (XRD) for respirable dust samples from MNM mines, and 
Fourier transform infrared spectroscopy (FTIR) for respirable coal mine 
dust samples.\7\ The XRD method uses X-rays to distinguish and measure 
the structure, composition, and physical properties of a sample. The 
FTIR method relies on the absorption of infrared light to determine the 
composition of a sample. 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. The percentage of silica is used to calculate MSHA's PELs for 
quartz and cristobalite, in accordance with Sec. Sec.  56.5001 and 
57.5001. 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. For coal mines, the percentage of quartz 
is used to calculate the reduced dust standard when the quartz 
concentration exceeds 100 [micro]g/m\3\ (MRE).
---------------------------------------------------------------------------

    \7\ 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. 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.
---------------------------------------------------------------------------

    It is worth noting how MSHA calculates full-shift exposure to 
respirable crystalline silica (and other airborne contaminants). When a 
miner who works an 8-hour shift is sampled, the miner's 8-hour TWA 
exposure is calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.001

    However, for work shifts that last longer than 8 hours, a coal 
miner's full-shift exposure is calculated differently than an MNM 
miner's full-shift exposure. In accordance with Sec.  70.2, the coal 
miner's extended full-shift exposure has, since 2014, been calculated 
in the following way:
[GRAPHIC] [TIFF OMITTED] TP13JY23.002

    For the MNM miner, MSHA calculates extended full-shift exposure 
according to the following formula:
[GRAPHIC] [TIFF OMITTED] TP13JY23.003

    For respirable dust samples from MNM mines, 480 minutes is used in 
the denominator regardless of the actual sampling time. Contaminants 
collected over extended shifts (e.g., 600-720 minutes) are calculated 
as if they had been collected over 480 minutes. MSHA has used this 
calculation approach (also known as ``shift-weighted average'') since 
the 1970s.
    Under the shift-weighted average approach, exposures for work 
schedules greater than 8 hours are proportionately adjusted to allow 
direct comparison with the 8-hour PEL. The ACGIH TLVs[supreg] adopted 
by MSHA are based on exposure periods of no more than 8 hours per day 
and 40 hours per week, with 16 hours of recovery time between shifts.

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

    This section presents 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 that met the minimum mass 
gain criteria were analyzed for respirable crystalline silica.

[[Page 44864]]

The vast majority of the 46,585 valid samples that were excluded from 
the analysis in this rulemaking did not meet the mass gain criteria 
described earlier and therefore the lab did not determine their silica 
concentration. Further information on the valid respirable dust samples 
that are excluded from the analysis in this rulemaking can be found in 
Appendix A of the preamble.
    The respirable crystalline silica concentration is calculated using 
the measured mass of each of the polymorphs and the air sampling 
volume. As discussed above, the existing PEL for quartz in MNM mines is 
approximately equivalent to 100 [micro]g/m\3\ for a full-shift 
exposure, calculated as an 8-hour TWA, while the existing PELs for 
cristobalite and tridymite, respectively, are approximately equivalent 
to 50 [micro]g/m\3\ for a full-shift exposure, calculated as an 8-hour 
TWA.\8\
---------------------------------------------------------------------------

    \8\ If more than one polymorph is present the equation used to 
calculate the TLV[supreg] for respirable dust containing quartz is 
modified per Appendix C of the 1973 ACGIH TLV[supreg] Handbook, and 
the equation is modified as follows: 10/[(% quartz + 2) + 2 (% 
cristobalite + 2)].
---------------------------------------------------------------------------

1. Annual Results of MNM Respirable Crystalline Silica Samples
    Table IV-1 below shows the variation between 2005 and 2019 in: (1) 
the numbers 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
[GRAPHIC] [TIFF OMITTED] TP13JY23.004


[[Page 44865]]


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-2 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).
[GRAPHIC] [TIFF OMITTED] TP13JY23.005

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-3 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-3 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

[[Page 44866]]

higher rates, ranging up to more than 19 percent (in the case of stone 
cutting operators).
[GRAPHIC] [TIFF OMITTED] TP13JY23.006

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. In 
addition, about 80 percent of samples taken from stone cutting 
operators did not exceed the existing PEL, which historically has had 
high exposures to respirable dust and respirable crystalline silica; 
\10\ nevertheless, this occupation continues to experience the highest 
overexposures relative to other MNM occupations. 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).
---------------------------------------------------------------------------

    MSHA believes that improved technology, engineering controls, and 
better training contributed to the reductions in exposures for miners 
who work in occupations exposed to the highest levels of respirable 
crystalline silica. 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' exposure at or below the existing limit of 100 
[micro]g/m\3\.

E. Respirable Crystalline Silica Sampling Results--Coal Mines

    To examine coal mine operators' compliance with existing respirable 
crystalline silica standards, MSHA analyzed 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 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 (Coal Dust Rule) (79 FR 24813, May 1, 
2014) went into effect. At that time, the exposure limits for RCMD

[[Page 44867]]

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 these valid 
samples, only those collected from the breathing zones of miners were 
used in the analysis for this rulemaking; no environmental dust samples 
were included.\11\ Of those samples, 63,127 samples that met the 
minimum mass gain criteria and had no other disqualifying issues were 
analyzed for respirable quartz and quartz concentrations were 
determined. 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 (the percent of samples above the exposure limit, on average 
across all coal mining occupations) 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-4, 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] TP13JY23.007

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-5, 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.

[[Page 44868]]

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.
[GRAPHIC] [TIFF OMITTED] TP13JY23.008

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 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-6 displays the number and percent of respirable coal 
mine dust samples with quartz greater than the existing exposure limit 
for each occupational category.

[[Page 44869]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.009

    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.

[[Page 44870]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.010

BILLING CODE 4520-43-C
    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 can 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 is 
contained in the standalone document, entitled Effects of Occupational 
Exposure to Respirable Crystalline Silica on the Health of Miners 
(Health Effects document), which has been placed in the rulemaking 
docket for the MSHA silica rulemaking (RIN 1219-AB36, Docket ID no. 
MSHA-2023-0001) and is available on MSHA's website.
    The purpose of the Agency's scientific review is to present MSHA's 
preliminary findings on the nature of the hazards presented by exposure 
to respirable crystalline silica and to present the basis for the 
Preliminary

[[Page 44871]]

Risk Analysis (PRA) to follow. (A PRA summary is presented in Section 
VI of this preamble and a standalone document entitled Preliminary Risk 
Analysis has been placed in the rulemaking docket for the MSHA silica 
rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is 
available on MSHA's website.) MSHA reviewed a wide range of health 
research 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. After discussing the toxicity of respirable crystalline 
silica, MSHA's review of the literature covers the following topics:
    (1) Silicosis;
    (2) NMRD, excluding silicosis;
    (3) Lung cancer and cancer at other sites;
    (4) Renal disease; and
    (5) Autoimmune diseases.
    To develop this literature review, MSHA expanded upon OSHA's 
(2013b) review of the health effects literature to support its final 
respirable crystalline silica rule (81 FR 16286, March 25, 2016). MSHA 
also 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, morbidity (having a disease or a symptom of disease) and 
mortality (disease resulting in death) analyses, progression and 
pathology evaluations, death certificate and autopsy reviews, medical 
surveillance data, health hazard assessments, in vivo (animal) and in 
vitro toxicity data, and other toxicological reviews. These sources are 
cited throughout this summary and are listed in the References section 
of the Health Effects document. Additionally, these sources appear in 
the rulemaking docket.
    MSHA's literature review is based on a weight-of-evidence approach, 
in which studies 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. Factors MSHA considered in this weight-of-
evidence analysis include: size of the cohort studied and power of the 
study to detect a sufficiently low level of disease risk, duration of 
follow-up of the study population, potential for study bias (such as 
selection bias or healthy worker effects), and adequacy of underlying 
exposure information for examining exposure-response relationships. Of 
the studies examined in the Health Effects document, studies were 
deemed suitable for inclusion in the PRA if there was adequate 
quantitative information on exposure and disease risks and the study 
was judged to be of sufficiently high quality according to the above 
criteria.
    The 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. Based on its extensive review of 
health research literature, MSHA has preliminarily determined that 
occupational exposure to respirable crystalline silica causes silicosis 
(acute silicosis, accelerated silicosis, simple chronic silicosis, and 
PMF), NMRD (including COPD), and lung cancer, and it also causes end-
stage renal disease (ESRD). In addition, MSHA believes that respirable 
crystalline silica exposure is causally related to the development of 
some autoimmune disorders through inflammation pathways. Each of these 
effects is exposure-dependent, chronic, irreversible, and potentially 
disabling or fatal. 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 and functional capacity. Based on the assessment 
of health effects of respirable crystalline silica, MSHA preliminarily 
concludes that the proposed rule, which would lower the exposure limits 
in MNM and coal mining to 50 [micro]g/m\3\ and establish an action 
level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as an 
8-hour TWA, would reduce the risk of miners developing silicosis, NMRD, 
lung cancer, and renal disease.

A. 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 it is deposited in mines or mills. Respirable crystalline silica 
particles may be irregularly shaped and variable in size. Inhaled 
respirable crystalline silica can be deposited throughout the lungs. 
Some pulmonary clearance of particles deposited in the deep lung (i.e., 
alveolar region) may occur, but a large number of 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 do not undergo metabolism into less toxic compounds. 
This is important biologically and physiologically, as 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. Researchers believe that the size and surface 
characteristics 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 (OSHA, 2013b; 
ATSDR, 2019).
    Inflammation 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. The elevated production of ROS/RNS would result in 
oxidative stress and lung injury that stimulates alveolar macrophages, 
ultimately resulting in fibroblast activation and pulmonary fibrosis. 
The prolonged recruitment of macrophages and PMN causes a persistent 
inflammation, regarded as a primary step in the development of 
silicosis.
    The strong immune response in the lung following exposure to 
respirable

[[Page 44872]]

crystalline silica may also be linked to a variety of extra-pulmonary 
adverse effects such as hypergammaglobulinemia, production of 
rheumatoid factor, anti-nuclear antibodies, and release of other immune 
complexes (Parks et al., 1999, Haustein and Anderegg, 1988; Green and 
Vallyathan, 1996). Respirable crystalline silica exposure has also been 
associated with nonmalignant renal disease 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 (Brown and 
Donaldson, 1996; Castranova, 2004; Fubini et al., 2004; Nolan et al., 
1981; Shi et al., 1989, 1998).

B. Diseases

1. Silicosis
    Silicosis is a progressive occupational disease that has long been 
identified as a cause of lung disease in miners. Based on its review of 
the literature, MSHA has preliminarily determined that exposure to 
respirable crystalline silica causes silicosis (acute silicosis, 
accelerated silicosis, simple chronic silicosis, and PMF) in MNM and 
coal miners, which is a significant cause of serious morbidity and 
early mortality in this occupational cohort (Mazurek and Attfield, 
2008; Mazurek and Wood, 2008a, 2008b; Mazurek et al., 2015, 2018).
    When respirable crystalline silica particles accumulate in the 
lungs, they cause an inflammatory reaction, leading to lung damage and 
scarring. Silicosis can continue to develop even after silica exposure 
has ceased. 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 MNM miners can lead to 
all three forms of silicosis (acute, accelerated, and chronic). These 
forms differ in the rate of exposure, pathology (i.e., the 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 
(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 it 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 can suffocate the patient. 
The radiographic (X-ray) appearance and results of microscopic 
examination of acute silicosis are like those of idiopathic pulmonary 
alveolar proteinosis.
    Chronic silicosis is the most frequently observed form of silicosis 
in the United States today (Banks, 2005; OSHA, 2013b; Cowie and 
Becklake, 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 10 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 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 chest X-ray films usually 
underestimate the true prevalence of silicosis (Craighead and 
Vallathol, 1980; Hnizdo et al., 1993; Rosenman et al., 1997; Cohen and 
Velho, 2002). However, 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 a 
chronic cough, sputum production, shortness of breath, and reduced 
pulmonary function.
    Accelerated silicosis includes both inflammation and fibrosis and 
is associated with intense respirable crystalline silica exposure. 
Accelerated silicosis usually manifests over a period of 3 to 10 years 
(Cowie and Becklake, 2016), but it can develop in as little as 2 to 5 
years if exposure is sufficiently intense (Davis, 1996). Accelerated 
silicosis may have features of both chronic and acute silicosis (i.e., 
alveolar proteinosis in addition to X-ray evidence of fibrosis). 
Although the symptoms are similar to 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.
    Among coal miners, silicosis is usually found in conjunction with 
simple coal worker's pneumoconiosis (CWP) (Castranova and Vallyathan, 
2000) because of their exposures to RCMD that contains respirable 
crystalline silica. 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, see Figure 2, 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 (Attfield et al., 1994; Cohen et al., 2016, 2019, 
2022; Davis et al., 1979; Douglas et al., 1986; Fernie and Ruckley, 
1987; Green et al., 1989, 1998b; Ruckley et al., 1981, 1984; Vallyathan 
et al., 2011). Autopsy studies in British coal miners indicated that 
the more advanced the disease, the more mixed coal mine dust 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 from the United States (Cohen et al., 2016, 
2022), 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).

[[Page 44873]]

a. Classifying Radiographic Findings of Silicosis
    Two classification methods used to characterize the radiographic 
findings of silicosis in chest X-rays are described in this literature 
review: the International Labour Office (ILO) Standardized System and 
the Chinese categorization system.\16\
---------------------------------------------------------------------------

    \16\ The ``Radiological Diagnostic Criteria of Pneumoconiosis 
and Principles for Management of Pneumoconiosis'' (GB5906-86) (Chen 
et al., 2001; Yang et al., 2006).
---------------------------------------------------------------------------

    To describe the presence and severity of pneumoconiosis from chest 
X-rays or digital radiographic images, the ILO developed a standardized 
system to classify the opacities identified (ILO, 1980, 2002, 2011, 
2022). The ILO system grades the size, shape, and profusion (frequency) 
of opacities in the lungs. The density of opacities is classified on a 
4-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 and categories 1 to 3 reflect increasing profusion of 
opacities and a concomitant increase in severity of disease.
    MSHA's analysis of silicosis studies uses NIOSH's surveillance case 
definition to determine the presence of silicosis. 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 where 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).\17\ MSHA interprets 
``minimal effects'' to mean an X-ray ILO profusion score of category 1/
0 or greater.
---------------------------------------------------------------------------

    \17\ On March 26, 1969, Charles C. Johnson, Jr., Administrator, 
Consumer Protection and Environmental Health Service, PHS, U.S. 
Department of Health, Education, and Welfare, testified before the 
General Subcommittee on Labor and presented remarks of the Surgeon 
General. They are referenced in the 91st Congress House of 
Representatives Report, 1st Session No. 91-563, Federal Coal Mine 
Health and Safety Act, October 13, 1969 (https://arlweb.msha.gov/SOLICITOR/COALACT/69hous.htm).
---------------------------------------------------------------------------

    However, some studies in MSHA's literature review use the Chinese 
categorization scheme, which includes four categories of silicosis: a 
suspected case (0+), stage I, stage II, or stage III. 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). Under this scheme, a 
panel of three radiologists determines the presence and severity of 
radiographic changes consistent with pneumoconiosis.
b. Progression and Associated Impairment
    Progression of silicosis is shown when there are changes or 
worsening of the opacities in the lungs, and sequential chest 
radiographs are 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 
uncertainty in scoring films, some investigators count progression as 
advancing two or more subcategories, such as 1/0 to 1/2.
    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 more 
recent literature (Dumavibhat et al., 2013; Mohebbi and Zubeyri, 2007; 
Wade et al., 2011) not previously reviewed by OSHA (2013b).
    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 (Almberg et al., 2020; Cochrane et al., 1956; Hall et al., 
2020b; Hurley et al., 1987; Kimura et al., 2010; Maclaren et al., 
1985). In addition, although lung function impairment is highly 
correlated with chest X-ray films indicating silicosis, researchers 
cautioned 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 (Hessel et al., 1988 
study of gold miners; Miller and MacCalman, 2010 study of coal miners; 
Miller et al., 1998 study of coal miners; Ng et al., 1987a study of 
granite 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 (i.e., the product of 
the concentration times duration of exposure, which is summed over 
time) (Hessel et al., 1988; Ng et al., 1987a; Miller and MacCalman, 
2010; Miller et al., 1998). 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. It 
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 on 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\ 
(1-3 mg/m\3\), and for a brief period, concentrations exceeded 10,000 
[micro]g/m\3\ (10 mg/m\3\) for one job. Some of these high exposures 
were associated with accelerated disease progression.
    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 [mu]g/m\3\, >2 mg/m\3\) increased the 
silicosis risk by three-fold (compared to the risk of cumulative 
exposure alone) (see the

[[Page 44874]]

separate Preliminary Risk Analysis document).
    The risks of increased rate of progression, predicted by Buchanan 
et al. (2003) have been seen in coal miners (e.g., Cohen et al., 2016; 
Laney et al., 2010, 2017; Miller et al., 1998), 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 (Mohebbi and Zubeyri, 2007; NIOSH 2000a,b; 
Ogawa et al., 2003a). Accordingly, it is important to limit higher 
exposures to respirable crystalline silica in order to minimize the 
risk of rapid progressive pneumoconiosis (RPP) in miners.
    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 a 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.
c. Occupation-Based Epidemiological Studies
    MSHA reviewed the occupation-based epidemiological literature 
(i.e., studies that examine health outcomes among workers and their 
potential association with conditions in the workplace). MSHA's review 
included the occupation-based literature OSHA cited in developing its 
respirable crystalline silica standard (OSHA, 2013b). Overall, OSHA 
found substantial evidence suggesting that occupational exposure to 
respirable crystalline silica increases the risk of silicosis, and MSHA 
concurs with this conclusion. MSHA also reviewed additional occupation-
based literature specific to respirable crystalline silica exposure in 
MNM and coal miners and preliminarily 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 2 months.
    In a population of granite quarry workers (mean length of 
employment: 23.4 years) exposed to an average respirable crystalline 
silica concentration of 480 [micro]g/m\3\ (0.48 mg/m\3\), 45 percent of 
those diagnosed with simple silicosis showed radiological progression 
of disease 2 to 10 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).
    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). 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 simple 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).
    Overall, MSHA preliminarily agrees with OSHA's conclusion that 
substantial evidence suggests that occupational exposure to respirable 
crystalline silica increases the risk of silicosis. MSHA also 
preliminarily concludes that respirable crystalline silica exposure 
increases the risk of silicosis morbidity and early mortality among 
miners.
d. Surveillance Data
    In addition to occupation-based epidemiological studies, MSHA 
reviewed surveillance studies, which provide and interpret data to 
facilitate the prevention and control of disease, and preliminarily 
finds that the prevalence of silicosis generally increases with 
duration of exposure (work tenure). However, the available statistics 
may underestimate silicosis-related morbidity and mortality in miners. 
For example, the following have been reported: (1) misclassification of 
causes of death (e.g., 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, 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 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
    Finally, in addition to the relationship between silica exposure 
and silicosis, studies indicate a relationship between silica exposure, 
silicosis, and pulmonary TB. OSHA reviewed these and concluded that 
silica exposure and silicosis increase the risk of pulmonary TB (Cowie, 
1994; Hnizdo and Murray, 1998; teWaterNaude et al., 2006). MSHA agrees 
with this conclusion.
    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 (i.e., active) pulmonary TB 
(Sherson and

[[Page 44875]]

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'' (i.e., 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 new studies (Ndlovu et al., 
2019; Oni and Ehrlich, 2015) published since OSHA's review (2013b). 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 7 percent of men (n = 54) and 3 percent of women (n = 4) were 
found to have pulmonary silicosis.
    Overall, MSHA agrees with OSHA's conclusion that silica exposure 
increases the risk of pulmonary TB and that pulmonary TB is a 
complication of chronic silicosis.
2. Nonmalignant Respiratory Disease (Excluding Silicosis)
    In addition to causing silicosis (acute silicosis, accelerated 
silicosis, simple chronic silicosis, and PMF), exposure to respirable 
crystalline silica causes other NMRD. NMRD includes emphysema and 
chronic bronchitis, which are both diagnoses within the category of 
COPD. Patients with COPD may have chronic bronchitis, emphysema, or 
both (ATS, 2010a).
    Based on its review of the literature, MSHA preliminarily 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 involves the destruction of lung architecture in the 
alveolar region, causing airway obstruction and impaired gas exchange. 
In its literature review, OSHA (2013b) concluded that exposure to 
respirable crystalline silica can increase the risk of emphysema, 
regardless of whether silicosis is present. OSHA also concluded that 
this is the case for smokers and that smoking amplifies the effects of 
respirable crystalline silica exposure, increasing the risk of 
emphysema. MSHA reviewed the studies cited by OSHA and agrees with its 
conclusion. The studies reviewed 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 white 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 life-long 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 
discussed in the OSHA (2013b) Health Effects Literature 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 
previously reported by Becklake et al. (1987).
    The OSHA (2013b) Health Effects Literature also recognized that 
several of the referenced studies (Becklake et al., 1987 Hnizdo et al., 
1994) 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. 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 tended to support human studies 
that respirable crystalline silica-induced emphysema can occur absent 
signs of silicosis.
    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. Finally, NIOSH 
(2002b) concluded in its Hazard Review that occupational exposure to 
respirable crystalline silica is associated with emphysema. However, 
some epidemiological studies suggested that this effect might be less 
frequent or absent in non-smokers.
    Overall, MSHA agrees with OSHA that exposure to respirable 
crystalline silica causes emphysema even in the absence of silicosis.
b. Chronic Bronchitis
    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 
(i.e., the presence of a productive cough sputum production for at 
least 3 months of the year for at least 2 consecutive years) (ATS, 
2010b).
    OSHA considered many studies that examined the association between 
respirable crystalline silica exposure and chronic bronchitis, 
concluding 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. 
MSHA has reviewed the literature and agrees with OSHA's conclusions.
    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 4 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\.
    Cowie and Mabena (1991) found that chronic bronchitis was present 
in 742 of

[[Page 44876]]

1,197 (62 percent) black 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 and did not 
find as clear a relationship as did the above studies, concluding 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 
(1977) found that the prevalence of chronic bronchitis rose 
significantly with increasing dust concentration and cumulative dust 
exposure in South African gold miners of 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 respirable crystalline 
silica exposure durations were very short, and control workers may also 
have been exposed to respirable crystalline silica.
    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 that had worked in the mines for over 
1 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 5 months when the study began, so miners were not exposed at 
the time of the study.
    The American Thoracic Society (ATS) (1997) published a review 
finding chronic bronchitis to be common among worker groups exposed to 
dusty environments contaminated with respirable crystalline silica. 
NIOSH (2002b) also published a review finding 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.
    Finally, Hnizdo et al. (1990) 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. However, for miners 
with the most severe impairment, the effects of smoking and dust were 
synergistic (i.e., more than additive).
    Overall, MSHA agrees with OSHA's conclusion that exposure to 
respirable crystalline silica causes chronic bronchitis regardless of 
whether silicosis is present and that an exposure-response relationship 
may exist.
c. Pulmonary Function Impairment
    Pulmonary function impairment, generally defined as reduction below 
the lower limit of normal predicted by reference equations (and in 
older literature as less than 80 percent predicted) of diffusion 
capacity for carbon monoxide (DLCOcSB), total lung capacity (TLC), FVC, 
or FEV1 is also a common condition of NMRD. 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. MSHA has reviewed the studies cited by OSHA and agrees with 
their conclusions.
    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 
and consequently did not voluntarily participate in the last of a 
series of annual pulmonary function tests (termed ``dropouts''). This 
group experienced steeper declines in lung function compared to the 
subset of workers who remained at work and participated in all tests 
(termed ``survivors''), 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 5-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 their 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 (1 mg/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 standard (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

[[Page 44877]]

exposure measurement surrogates (e.g., tenure). The results of these 
studies were similar to those longitudinal studies already discussed. 
In several studies, respirable crystalline silica exposure was found to 
reduce lung function of:
     White South African gold miners (Hnizdo et al., 1990),
     Black South African gold miners (Cowie and Mabena, 1991; 
Irwig and Rocks, 1978),
     Respirable crystalline silica-exposed workers in Quebec 
(B[eacute]gin et al., 1995),
     Rock drilling and crushing workers in Singapore (Ng et 
al., 1992b),
     Granite shed workers in Vermont (Theriault et al., 1974a, 
1974b),
     Aggregate quarry workers and coal miners in Spain (Montes 
et al., 2004a, 2004b),
     Concrete workers in the Netherlands (Meijer et al., 2001),
     Chinese refractory brick manufacturing workers in an iron-
steel plant (Wang et al., 1997),
     Chinese gemstone workers (Ng et al., 1987b),
     Hard-rock miners in Manitoba, Canada (Manfreda et al., 
1982) and in Colorado (Kreiss et al., 1989),
     Pottery workers in France (Neukirch et al., 1994),
     Potato sorters in the Netherlands (Jorna et al., 1994),
     Slate workers in Norway (Suhr et al., 2003), and
     Men in a Norwegian community with years of occupational 
exposure to respirable crystalline silica (quartz) (Humerfelt et al., 
1998).
    The OSHA (2013b) Health Effects Literature 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 in the OSHA (2013b) Health Effects 
Literature have also 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 agrees with OSHA's finding that there 
is an exposure-response relationship between respirable crystalline 
silica and the impairment of lung function. MSHA also agrees with 
OSHA's finding 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.
3. Carcinogenic Effects
a. Lung Cancer
    Lung cancer, an irreversible and usually fatal disease, is a type 
of cancer that forms in lung tissue. Agreeing with the conclusion of 
other government and public health organizations that respirable 
crystalline silica is a ``known human carcinogen,'' MSHA has 
preliminarily 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 IARC (1997b, 2012), the NTP (2000, 2016), 
NIOSH (2002b), the ATS (1997), and the American Conference of 
Governmental Industrial Hygienists (ACGIH[supreg], (2010)). The 
Agency's determination 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 (Carta et al., 2001; Attfield and Costello, 2004; Costello 
et al., 1995; Gu[eacute]nel et al., 1989a,b), 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 
(Steenland and Brown, 1995a; deKlerk and Musk, 1998; Roscoe et al., 
1995; Hessel et al., 1986, 1990; Hnizdo and Sluis-Cremer, 1991; Reid 
and Sluis-Cremer, 1996; Hnizdo et al., 1997; Chen et al., 1992; 
McLaughlin et al., 1992; Chen and Chen, 2002; Chen et al., 2006; 
Schubauer-Berigan et al., 2009; Hua et al., 1994; Meijers et al., 1991; 
Finkelstein 1998; Chen et al., 2012; Liu et al., 2017a; Wang et al., 
2020a,b; Wang et al., 2021), coal mining (Meijers et al., 1988; Miller 
et al., 2007; Miller and MacCalman, 2010; Miyazaki and Une, 2001; 
Graber et al., 2014a,b; Tomaskova et al., 2012, 2017, 2020, 2022; 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).
    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, 
confirmed by the 10-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; 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; Tomaskova et al., 2012, 2017, 2020, 2022; 
Attfield and Kuempel, 2008; Graber et al., 2014a, 2014b; Kurth et al., 
2020; NIOSH, 2019a). These studies also discuss the associations 
between RCMD and respirable crystalline silica exposures with lung 
cancer in coal mining populations. Furthermore, 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 preliminarily 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 literature, MSHA has 
preliminarily 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).
    Toxicity studies provide additional evidence of the carcinogenic 
potential of respirable crystalline silica. Studies using DNA exposed 
directly to freshly fractured respirable crystalline silica demonstrate 
the direct effect respirable crystalline silica had on DNA breakage. 
Cell culture research has investigated the processes by which 
respirable crystalline silica disrupt 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

[[Page 44878]]

genotoxicity (Schins et al., 2002; Borm and Driscoll, 1996) support 
MSHA's preliminary determination that respirable crystalline silica is 
an occupational carcinogen.
b. Cancers of Other Sites
    In addition to lung cancer, OSHA reviewed studies examining the 
relationship between silica exposure and cancers at other sites. MSHA 
notes that OSHA reviewed these mortality studies (e.g., 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. OSHA also pointed to the NIOSH (2002b) 
silica (respirable crystalline silica) hazard review, which concluded 
that no association has been established between respirable crystalline 
silica exposure and excess mortality from cancer at other sites. MSHA 
has reviewed these studies and agrees with OSHA's conclusion. The 
following summarizes the studies reviewed with inconclusive findings.
(1) Laryngeal Cancer
    Three lung cancer studies (Checkoway et al., 1997; Davis et al., 
1983; McDonald et al., 2001) included in OSHA's health literature 
review suggest an association between respirable crystalline silica 
exposure and increased mortality from laryngeal cancer. However, a 
small number of cases were reported and researchers were unable to 
determine a statistically significant effect. Therefore, there is 
little evidence of an association based on these studies.
(2) Gastric (Stomach) Cancer
    OSHA reviewed several studies in its 2013b health literature review 
to assess a potential relationship between respirable crystalline 
silica exposures and stomach cancers. OSHA's literature review noted 
observations made previously by Cocco et al. (1996) and in the NIOSH 
respirable crystalline silica hazard review (2002b), 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 (e.g., 
Finkelstein and Verma, 2005; Moshammer and Neuberger, 2004; Selikoff, 
1978; Stern et al., 2001) or did not demonstrate a statistically 
significant dose-response relationship (e.g., Calvert et al., 2003; 
Tsuda et al., 2001). For these reasons, MSHA determined these studies 
were inconclusive in the context of this rulemaking.
(3) Esophageal Cancer
    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; Wernli et al., 2006; Yu 
et al., 2005). Other studies (Tsuda et al., 2001; Xu et al., 1996a) 
also indicated elevated rates of esophageal cancer mortality with 
respirable crystalline silica exposure. However, OSHA noted that 
confounding factors 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). MSHA agrees with OSHA's conclusion 
that the literature does not support attributing increased esophageal 
cancer mortality to exposure to respirable crystalline silica.
(4) Other Sites
    NIOSH (2002b) conducted a health literature review of the health 
effects potentially associated with respirable crystalline silica 
exposure, which identified only infrequent reports of statistically 
significant excesses of deaths for other cancers. Cancer studies have 
been reported in 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.
    Overall, OSHA concluded that evidence of an association between 
silica exposure and cancer at sites other than the lungs is not 
sufficient. MSHA agrees with OSHA's conclusion.
4. Renal Disease
    Renal disease is characterized by the loss of kidney function, and 
in the case of ESRD, the need for a regular course of long-term 
dialysis or a kidney transplant. 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 
preliminarily concludes that respirable crystalline silica exposure 
increases the risk of morbidity and/or 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 (Nuyts 
et al., 1995) (severe injury to the glomeruli that, if untreated, 
rapidly leads to renal failure). 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 
preliminarily 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 preliminarily determines that respirable crystalline 
silica exposure in mining increases the risk of renal disease.

[[Page 44879]]

5. Autoimmune Disease
    Autoimmune diseases occur when the immune system mistakenly attacks 
healthy tissues within the body, causing inflammation, swelling, pain, 
and tissue damage. Examples include rheumatoid arthritis (RA), systemic 
lupus erythematosus (SLE), scleroderma, and systemic sclerosis (SSc). 
Based on its literature review, MSHA preliminarily concludes that there 
is a causal association between occupational exposure to respirable 
crystalline silica and the development of systemic autoimmune diseases 
in miners. However, no studies are available to date that can be used 
to model respirable crystalline silica-exposure risk in a formal 
quantitative risk analysis.
    Wallden et al. (2020) found that respirable crystalline silica 
exposure is correlated with an increased risk of developing ulcerative 
colitis, which 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. Finally, Vihlborg et al. (2017) found a significant 
increased risk of seropositive RA with high exposure (>0.048 mg/m\3\) 
to respirable crystalline silica dust when compared to individuals with 
no or lower exposure by examining detailed exposure-response 
relationships across four different respirable crystalline silica dose 
groups (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 and seropositive RA in relation to 
respirable crystalline silica exposure using logistic regressions 
resulting in models that could be used in the risk assessment. 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.
C. Conclusion
    MSHA preliminarily concludes that occupational exposure to 
respirable crystalline silica causes silicosis (acute silicosis, 
accelerated silicosis, simple chronic silicosis, and PMF), NMRD 
(including COPD), lung cancer, and kidney disease. Each of these 
effects is exposure-dependent, chronic, irreversible, potentially 
disabling, and can be fatal. MSHA suspects that respirable crystalline 
silica exposure is also linked to the development of some autoimmune 
disorders through inflammation pathways.
    The scientific 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 limit of 100 [mu]g/m\3\ 
still have an unacceptable amount of excess risk for developing and 
dying from diseases related to occupational respirable crystalline 
silica exposures and still suffer material impairments of health or 
functional capacity.

VI. Preliminary Risk Analysis Summary

    MSHA's preliminary risk analysis (PRA) quantifies risks associated 
with five specific health outcomes identified in the separate, 
standalone Health Effects document: silicosis morbidity and mortality, 
and mortality from NMRD, lung cancer, and ESRD. The standalone 
document, entitled Preliminary Risk Analysis (PRA document), has been 
placed into the rulemaking docket for the MSHA respirable crystalline 
silica rulemaking (RIN 1219-AB36, Docket ID no. MSHA-2023-0001) and is 
available on MSHA's website.
    MSHA developed a PRA to support the risk determinations required to 
set an exposure limit for a toxic substance under the Mine Act. MSHA's 
PRA quantifies the health risk to miners exposed to respirable 
crystalline silica under the existing exposure limits for MNM and coal 
miners, at the proposed PEL of 50 [mu]g/m\3\, and at the proposed 
action level of 25 [mu]g/m\3\.
    This analysis addresses three questions related to the proposed 
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 proposed rule would reduce those risks.
    To answer these questions, MSHA relied on the large body of 
research on the health effects of respirable crystalline silica and 
several 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 assessments are based on several studies of occupational cohorts 
in a variety of industrial sectors. The underlying studies are 
described in the Health Effects document and are summarized in Section 
V. Health Effects Summary of this preamble.
    This summary highlights the main findings from the PRA, briefly 
describes how they were derived, and directs readers interested in more 
detailed information to corresponding sections of the standalone PRA 
document.

A. Summary of MSHA's Preliminary 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 MNM and coal miners based on real exposure conditions, as 
indicated by the samples in the compliance sampling datasets.
    MSHA's PRA is largely based on the methodology and findings from a 
peer-reviewed January 2013 OSHA preliminary quantitative risk 
assessment (PQRA) and 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 PRA 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 
proposed PEL, and (3) the proposed action level. As in past MSHA 
rulemakings, MSHA estimated and compared lifetime excess risks 
associated with exposures at the existing and proposed PEL (and at the 
proposed action level) over a miner's full working life of 45 years.

[[Page 44880]]

    MSHA's PRA 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 (e.g., 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 
proposed action level (25 [mu]g/m\3\) to above the existing standards 
(100 [mu]g/m\3\ in MNM standards, 100 [mu]g/m\3\ MRE in coal standards, 
which is approximately 85.7 [mu]g/m\3\ ISO).\18\
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    \18\ As discussed in the PRA, 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 PRA converts the MRE full-shift TWA concentrations experienced 
by coal miners to ISO 8-hour TWA concentrations. (See Section 4 of 
the PRA document for a full explanation.) The equation used to 
convert MRE full-shift TWA concentrations into ISO 8-hour TWA 
concentrations is:
    ISO 8-hour TWA concentration = (MRE TWA) x (original sampling 
time)/(480 minutes) x 0.857
    Exposures at TWA 100 [mu]g/m\3\ MRE and SWA 85.7 [mu]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 [mu]g/m\3\ as 85.7 [mu]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 
proposed 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.
---------------------------------------------------------------------------

    The primary results of the PRA are the calculated number of deaths 
and illnesses avoided assuming full compliance after implementation of 
MSHA's proposed 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 illnesses and deaths currently occurring in 
the industry, assuming mines fully comply with the existing standards 
(100 [mu]g/m\3\ for MNM and 85.7 [mu]g/m\3\ ISO for coal) and (b) the 
number of deaths and illnesses expected to occur following 
implementation of the proposed rule, which includes a proposed PEL of 
50 [mu]g/m\3\ for a full shift exposure, calculated as an 8-hour TWA.
    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 proposed 50 
[mu]g/m \3\ scenario where all risks were capped at the proposed 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 proposed PEL.
    To calculate 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 
production employee 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 production employees, 
60,275 for MNM contract miners, 51,573 for coal production employees, 
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 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 \19\ 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 begin working at age 21, 
retire at the end of age 65, and do not live past age 80. From the life 
tables, MSHA acquired the lifetime mortality risk by summing the miner 
cohort's 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).
---------------------------------------------------------------------------

    \19\ 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 Proposed 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 the 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 both production employee 
FTEs and 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 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 proposed PEL, MSHA compared the lifetime excess risks and 
lifetime excess cases across the two scenarios (Baseline and Proposed 
50 [mu]g/m\3\).

B. Overview of Epidemiologic Studies

    MSHA reviewed extensive research on the health effects of 
respirable crystalline silica and several quantitative risk assessments 
published in the peer-reviewed scientific literature

[[Page 44881]]

regarding occupational exposure risks of illness and death from 
silicosis, NMRD, lung cancer, and ESRD. The 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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    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 worker populations based on real exposure conditions. Table 
VI-2 presents the 13 studies from OSHA's PQRA, which MSHA has also 
considered. 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 [mu]g/m\3\. Thorough evaluation has led MSHA to 
determine that the studies OSHA selected still provide the best 
available epidemiological models. However, MSHA utilized the Miller and 
MacCalman (2010) study to estimate risks. This study was published 
after OSHA completed much of its modeling for their 2013 PRA (OSHA, 
2013b). The study was included in OSHA's health effects assessment and 
its PQRA. The following lists the study 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).
    MSHA developed its risk estimates based on recent mortality data 
and using certain assumptions that differed from those used by OSHA, as 
explained in the standalone PRA document. 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).\20\
---------------------------------------------------------------------------

    \20\ FTEs were used to adjust the cumulative exposure over a 
year based on the average number of hours that miners work.
---------------------------------------------------------------------------

    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 
the 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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BILLING CODE 4520-43-C
    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 
proposed PEL (herein referred to as the ``Proposed 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 Proposed 50 [mu]g/m\3\ scenario, 
except that each miner group whose exposure exceeded the proposed 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 
proposed 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 Proposed 50 [mu]g/m\3\).
    For purposes of calculating risk in the PRA, both for MNM and coal 
miners, MSHA estimated excess risks by using the concentration 
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 
Proposed 50 [mu]g/m\3\ scenarios), thereby facilitating meaningful 
comparison. MSHA acknowledges that this metric does not correspond to 
the manner in which coal exposure concentrations are calculated for 
purposes of evaluating compliance under the existing standard. 
Nonetheless, MSHA believes that a full-shift, 8-hour TWA concentration 
accurately 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.

C. Summary of Studies Selected for Modeling

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. MSHA agrees that relying on studies that included retired 
workers comes closest to characterizing 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

[[Page 44886]]

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).
    OSHA summarized the Miller et al. (1995, 1998) and Buchanan et al. 
(2003) papers 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 production employees and contract workers). MSHA 
estimated risk at the existing standard assuming cumulative exposure to 
100 [micro]g/m\3\ ISO for MNM miners and 85.7 [micro]g/m\3\ ISO (100 
[micro]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 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

[[Page 44887]]

concentration of 100 [micro]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. However, in another paper, Soutar et al. (2004) noted that: 
``If the effects of silica vary according to the conditions of 
exposure, these risks are probably towards the high end of the risk 
spectrum, since the silica was freshly fractured from massive 
sandstone, and not derived from dirt bands where the quartz grains are 
aged and accompanied by clay minerals'' (OSHA 2013b, page 336). 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 exam 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 (1993b) 
(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 age 21 through 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 production employees 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 [micro]g/
m\3\ to 500 [micro]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., 2010; Laney et 
al., 2012b; 2017; Blackley et al., 2016b, 2018b; Reynolds et al., 
2018b; Halldin et al., 2019; Halldin et al., 2020; Almberg et al., 
2018a; Cohen et al., 2022) and accelerated silicosis in MNM miners 
(Dumavibhat et al., 2013; Hessel et al., 1988; Mohebbi and Zubeyri 
2007). The inclusion of this discussion in the risk analysis is to 
describe research that 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 estimated the increase of silicosis risk in miners 
exposed to extreme respirable crystalline silica exposures for varying 
periods of time ranging from 0 hours to 348 hours per year (i.e., 0.0 
percent to 20.0 percent of time at extreme exposures). This information 
is important because MSHA data indicate that many miners' respirable 
crystalline silica exposure samples over the years have exceeded the 
existing exposure limit(s) of 100 [micro]g/m\3\. MSHA data also 
indicate that a smaller number of MSHA samples showed respirable 
crystalline silica concentrations well above the existing MSHA standard 
of 100 [micro]g/m\3\. Over the last 15 years of MNM compliance data, 
188 samples (0.3 percent) were over 500 [micro]g/m\3\; the upper range 
of exposure was 4,289 [micro]g/m\3\ ISO (see PRA Table 4 of the PRA 
document). Over the last 5 years of coal compliance data, eight samples 
(<0.1 percent) were over 500 [micro]g/m\3\; the upper range of

[[Page 44888]]

exposure was 791.4 [micro]g/m\3\ MRE (see PRA Table 7 of the PRA 
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] TP13JY23.017

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 [mu]g/m\3\ (>2.0 mg/m\3\) was three 
times that for the concentrations <2,000 [mu]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 [mu]g/m\3\ (<2.0 mg/
m\3\) and high >2,000 [mu]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 [mu]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 [mu]g/
m\3\, equal to 0.1 mg/m\3\) and short-term exposures to high quartz 
concentrations (e.g., 2,000 [mu]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 [mu]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 
[mu]g/m\3\ (2.0 mg/m\3\).
    The results indicate 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 MSHA's proposed standard 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 age 
21 through 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 proposed 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 [mu]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 proposed 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 proposed standard 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 (1995a), 
and Australian gold miners (de Klerk et al., 1998). The researchers 
analyzed death certificates across all cohorts for cause of death. OSHA 
relied upon the published, peer-reviewed, pooled analysis of six 
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.

[[Page 44889]]

(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 believed this definition to err on the side 
of caution in that some cases of death from silicosis in the cohorts 
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).
[GRAPHIC] [TIFF OMITTED] TP13JY23.018


[[Page 44890]]


    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 [mu]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 [mu]g/m\3\-years (4.45 mg/m\3\-years), OR=3.1 (95% CI: 
2.5-4.0);
    (2) 9,080 [mu]g/m\3\-years (9.08 mg/m\3\-years), OR=4.6 (95% CI: 
3.6-5.9);
    (3) 16,260 [mu]g/m\3\-years (16.26 mg/m\3\-years), OR=4.5 (95% CI: 
3.5-5.8); and
    (4) 42,330 [mu]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-response relationship for 
silicosis. Thus, 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 [mu]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 [mu]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 [mu]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\

[[Page 44891]]

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 [mu]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] TP13JY23.019

Where timei is equal to one 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 [mu]g/m\3\, to be 13 deaths per 1,000 workers; at an 
exposure of 50 [mu]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. There is evidence in the record that chest X-
ray films are relatively insensitive to detecting lung fibrosis (OSHA 
2016a, 81 FR 16286, 16397). MSHA agrees with OSHA's estimate of 
silicosis morbidity risks.
    Hnizdo et al. (1993a) 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. (1993a) 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 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 existing and 
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 
[mu]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 [mu]g/m\3\) and proposed exposure limit 
(50 [mu]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[mu]g/m\3\ (0.25 mg/
m\3\) and 500 [mu]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 foregoing 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 proposed PEL, and the proposed 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.
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

[[Page 44892]]

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 investigators 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 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 one 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's 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 f(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 investigators 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

[[Page 44893]]

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 
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) represented those least likely to overestimate mortality 
risk. It was unlikely to have overstated silicosis mortality risks 
given that the estimates reflected only those deaths where silicosis 
was specifically identified on death certificates. Therefore, there was 
most likely an underestimate of the true silicosis mortality risk. 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 investigators. 
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. Coal 
miners were not included in the NMRD mortality analysis because the 
endpoint was included in the Quantitative Risk Assessment in Support of 
the Final Respirable Coal Mine Dust Rule (Dec. 2013).
    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).
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 44894]]

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 two 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 included analyses using both external 
and internal controls. The external controls used British 
administrative regional age-, time-, and cause-specific mortality rates 
from which to calculate SMRs. The internal controls from the mines used 
Cox proportional hazards regression methods, which considered 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 
ghm10-3, 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 2- to 
4-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 were 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 44895]]

largely manual . . .'' (OSHA 2013b, page 288).
    All these factors in this mortality analysis for the British coal 
miner cohort could have combined to yield lower 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 death 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 were 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 since there appeared 
to have been no exposures during the recent period when risks were seen 
to have increased (OSHA 2013b, page 289).
    OSHA believed, as does MSHA, that this study of a large British 
coal mining cohort provided 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 investigators 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 PRA uses risk estimates derived from 10 coal mines in the 
U.K. (Miller et al., 2007; Miller and MacCalman, 2010). These 
investigators 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 
programme. 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, 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).
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 Health Effects document. 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 PRA. 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

[[Page 44896]]

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 (2005) 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 investigators 
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. 
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 concludes that the evidence supporting causality regarding 
renal risk outweighs the evidence casting doubt on that conclusion. 
However, MSHA acknowledges the uncertainty associated with the 
divergent findings in the renal disease literature. 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 associated with exposure to respirable 
crystalline silica using background mortality rates for 1998. The U.S. 
cause-of-death data from 2018 were used as well. Lifetime risk 
estimates reflect excess risk through age 85. To estimate ESRD 
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)
    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 this PRA, MSHA has not quantified the 
reduction in risk associated with CWP among coal miners. Nonetheless, 
MSHA believes that the proposed rule would reduce the excess risk of 
this disease. Many coal

[[Page 44897]]

miners work extended shifts, thus increasing their potential exposure 
to respirable crystalline silica. The result of calculating exposures 
based on a full-shift 8-hour TWA would be more protective. Thus, the 
proposed 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.

D. Overview of Results

    Table VI-4 summarizes the PRA's main results: once it is fully 
effective (and all miners have been exposed only under the proposed 
PEL), the proposed rule is expected to result in at least 799 avoided 
deaths and 2,809 avoided cases of silicosis morbidity among the working 
miner population. These numbers represent the lifetime health outcomes 
expected to occur after both 45 years of employment under the proposed 
PEL (from 21 through 65 years of age) and 15 years of retirement (up to 
80 years of age). These estimates of the avoided lifetime excess 
mortality and morbidity represent the final calculations based on the 5 
selected models and the observed exposure data. The first group of 
miners that would experience the avoided lifetime fatalities and 
illnesses shown in Table VI-4 is the population living 60 years after 
promulgation of the proposed rule. In other words, this group would 
only contain miners exposed under the proposed rule. To calculate 
benefits associated with the proposed rulemaking, the economic analysis 
monetizes avoided deaths and illnesses while accounting for the fact 
that, during the first 60 years following promulgation, miners would 
have fewer avoided lifetime fatalities and illnesses because they would 
be exposed under both the existing standards and the proposed PEL.
[GRAPHIC] [TIFF OMITTED] TP13JY23.020

    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 proposed 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. The excess 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 
proposed 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.

[[Page 44898]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.021

BILLING CODE 4520-43-P
    Table VI-6 presents MSHA's estimates of lifetime excess risk per 
1,000 miners at exposure levels equal to the existing standards, the 
proposed PEL, and the proposed action level. These estimates are 
adjusted for FTE ratios and thus utilize cumulative exposures that more 
closely reflect the average hours worked per year.\21\ 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 
proposed PEL would lower the miner's lifetime excess risk of death by 
58.8 percent for silicosis, 45.6 percent for NMRD (not including 
silicosis), 52.0 percent for lung cancer, and 19.9 percent for ESRD. 
The MNM miner's risk of acquiring a non-fatal case of silicosis (would 
decrease by 80.4 percent).
---------------------------------------------------------------------------

    \21\ 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 exposure 
limit of 85.7 [mu]g/m\3\ (and given the weighted average FTE ratio of 
0.99), implementing the proposed PEL would lower the miner's lifetime 
excess risk of death by 42.3 percent for silicosis mortality, 40.2 
percent for NMRD mortality (not including silicosis), 43.5 percent for 
lung cancer mortality, and 15.8 percent for ESRD mortality. The coal 
miner's lifetime excess risk of acquiring non-fatal silicosis would 
decrease by 73.8 percent. While even greater reductions would be 
achieved at exposures equal to the proposed action level (25 [mu]g/
m\3\), some residual risks do remain at exposures of 25 [mu]g/m\3\. 
Notably, at the proposed action level, ESRD risk is still 20.7 per 
1,000 MNM miners and 21.6 per 1,000 coal miners. At the proposed action 
level, risk of non-fatal silicosis is 16.3 per 1,000 MNM miners and 
16.9 per 1,000 coal miners.

[[Page 44899]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.022

BILLING CODE 4520-43-C

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 immune to risk. Failing 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 VI-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 PRA Table 23 
through PRA Table 26 of the PRA document. As these tables show, when 
adjusting for the healthy worker survivor bias, the proposed PEL would 
decrease lifetime silicosis morbidity risk by 20.8 cases per 1,000 MNM 
miners (compared to the unadjusted estimate of 13.9 cases per 1,000 MNM 
miners, see PRA Table 15 of the PRA document) and 5.0 cases per 1,000 
coal miners (compared to 3.3 cases per 1,000 coal miners, see PRA Table 
16 of the PRA document). Still accounting for the healthy worker 
survivor bias, the proposed PEL would decrease total morbidity by 3,848 
lifetime cases among MNM miners (compared to 2,566 cases, see PRA Table 
17 of the PRA document) and by 366

[[Page 44900]]

lifetime cases among coal miners (compared to 244 cases, see PRA Table 
18 of the PRA document). Among the current MNM and coal mining 
populations, implementation of the proposed PEL during their full lives 
would have prevented 1,091 deaths and 94 deaths, respectively, over 
their lifetimes (compared to unadjusted estimates of 736 deaths and 63 
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 
proposed rule.

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 proposed 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.
1. Alternate Treatment of Exposure Samples in Excess of the Proposed 
Exposure Limit
    To estimate excess risks and excess cases under the proposed PEL, 
MSHA assumed that no exposures would exceed the proposed 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\ would likely decrease below the proposed 
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 proposed 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 proposed 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 3,111 fewer cases of non-fatal 
silicosis and coal miners are expected to experience 344 fewer cases of 
non-fatal silicosis over their lifetimes. MNM miners would experience 
1,137 fewer deaths and coal miners would experience 123 fewer deaths 
over their lifetimes. Compared to the lowball method--which estimates 
that the proposed PEL would prevent a total of 2,809 lifetime cases of 
non-fatal silicosis and 799 lifetime excess deaths (among both MNM and 
coal miners)--the highball method estimates totals of 3,445 avoided 
lifetime cases of non-fatal silicosis and 1,260 avoided lifetime excess 
deaths.
2. 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 proposed PEL to produce lifetime risk reductions of 
silicosis morbidity of 2,546-2,777 using average exposures (see PRA 
Table 41 of the PRA document), compared to 2,453-2,683 using median 
exposures (see PRA Table 37 of the PRA document). Among coal miners, 
this reduction is expected to be 246-279 using average exposures (see 
PRA Table 42 of the PRA document), compared to 229-265 using median 
exposures (see PRA Table 38 of the PRA document). The proposed PEL is 
estimated to reduce lifetime excess mortality by 735-791 MNM miner 
deaths and 65-73 coal miner deaths using average exposures (see PRA 
Tables 41 and 42 of the PRA document), compared to 708-764 MNM miner 
deaths and 60-69 coal miner deaths using median exposures (see PRA 
Tables 37 and 38 of the PRA document).
3. Samples With Insufficient 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 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 2022a). During the 15-year 
sample period for MNM exposure data, 40,618 MNM samples were not 
analyzed because the filter failed to meet the P-2 minimum net mass 
(weight) 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. The P-7 method requires a minimum sample 
mass of 0.100 mg \22\ of dust for the sample to be analyzed for quartz. 
During the five-year sample period for coal exposure data, 63,127 coal 
samples were not analyzed because the P-7 method's minimum mass 
requirement was not met.
---------------------------------------------------------------------------

    \22\ 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.
---------------------------------------------------------------------------

    For samples that do not meet a minimum threshold for total 
respirable dust mass, the MSHA lab does not analyze these samples for 
respirable crystalline silica. These samples were excluded from the 
risk analysis because their concentrations of respirable crystalline 
silica are not known. Nonetheless, the unanalyzed samples all had very 
low total respirable dust mass, making it unlikely that many would have 
exceeded the existing standards or the proposed PEL. Excluding these 
unanalyzed samples from the exposure datasets thus may introduce bias, 
potentially causing the Agency to overestimate the proportion of high-
intensity exposure values.

[[Page 44901]]

    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 [mu]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 
proposed PEL would result in 1,642 fewer cases of non-fatal silicosis 
among MNM miners and 128 fewer cases among coal miners, over their 
lifetimes. The proposed PEL would also result in 469 fewer deaths (due 
to all 4 diseases) among MNM miners and 34 fewer deaths among coal 
miners, over their lifetimes. This yields a total reduction of 1,770 in 
lifetime excess morbidity and of 503 in lifetime excess mortality, 
respectively. While these estimates are lower than those presented in 
Table VI-4 (of 2,809 avoided lifetime cases of non-fatal silicosis and 
799 avoided lifetime excess fatalities), MSHA nonetheless believes 
that--even including these unanalyzed samples--the proposed 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 proposed 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 PRA 
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. Section-by-Section Analysis

    MSHA proposes to add a new part 60, titled Respirable Crystalline 
Silica, to title 30 CFR, chapter I, subchapter M--Uniform Mine Health 
Regulations. Proposed part 60, which would apply to all MNM and coal 
mines, contains health standards to protect all miners from adverse 
health risks caused by occupational exposure to respirable crystalline 
silica (as discussed in the standalone document entitled Effects of 
Occupational Exposure to Respirable Crystalline Silica on the Health of 
Miners and as summarized in Section V. Health Effects Summary of this 
preamble). This proposed part establishes a new PEL for respirable 
crystalline silica for all mines and includes other ancillary 
provisions to improve methods of compliance, exposure monitoring, 
corrective actions, respiratory protection, medical surveillance for 
MNM miners, and recordkeeping. In addition to the new part 60, MSHA 
proposes to incorporate by reference ASTM F3387-19, Standard Practice 
for Respiratory Protection, to replace its respiratory protection 
standards under 30 CFR parts 56, 57, and 72 to better protect all 
miners from airborne contaminants. This section-by-section analysis 
discusses each provision under the proposed part 60, the conforming 
amendments related to the proposed part, and the updated respiratory 
protection standard.

A. Part 60--Respirable Crystalline Silica

    MSHA has preliminarily determined that occupational exposure to 
respirable crystalline silica causes adverse health effects, including 
silicosis (acute silicosis, accelerated silicosis, simple chronic 
silicosis, and PMF), NMRD (e.g., emphysema and chronic bronchitis), 
lung cancer, and renal diseases. MSHA has also preliminarily determined 
that under the existing standards, miners remain at risk of suffering 
material impairment of health or functional capacity from these adverse 
health effects. Each of these effects is exposure-dependent, chronic, 
irreversible, and potentially disabling or fatal. MSHA has 
preliminarily concluded that lowering the PEL for respirable 
crystalline silica to 50 [mu]g/m\3\ would substantially reduce the 
health risks to miners.
    MSHA proposes to replace its existing standards for respirable 
crystalline silica or respirable dust containing quartz with a single, 
uniform health standard for all miners. The proposed uniform standard 
would establish consistent, industry-wide requirements that directly 
address the adverse health effects of overexposure to respirable 
crystalline silica. This proposal would also facilitate mining-industry 
compliance and help MSHA and other stakeholders provide consistent 
compliance assistance. MSHA believes this unified regulatory framework 
for controlling miner exposure to respirable crystalline silica would 
improve protection for all miners and help the Agency fulfill its 
obligations under the Mine Act to prevent occupational diseases.
    Proposed part 60 includes: Scope and effective date; Definitions; 
Permissible exposure limit (PEL); Methods of compliance; Exposure 
monitoring; Corrective actions; Respiratory protection; Medical 
surveillance for metal and nonmetal miners; Recordkeeping requirements; 
and Severability.
    Detailed discussions of the proposed sections are followed by 
discussions on conforming amendments and discussions of the proposed 
update to the respiratory protection standard in parts 56, 57, and 72.
1. Section 60.1--Scope; Effective Date
    This section provides that proposed part 60 would take effect 120 
days after the final rule is published in the Federal Register. Mine 
operators would be required to comply with the requirements in this 
part starting on the proposed effective date.
    MSHA believes that the proposed 120-day period gives operators the 
necessary 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. MSHA believes that it is important to reduce 
miner exposure to respirable crystalline silica promptly because every 
exposure at levels above the proposed PEL imposes adverse health risks 
on miners. However, for implementation to be successful, mine operators 
need enough time to understand the standard and to prepare for 
compliance (e.g., by purchasing gravimetric ISO-conforming samplers 
and/or selecting a commercial laboratory for respirable crystalline 
silica analysis, if necessary). MSHA believes that the proposed 
effective date of 120 days would provide enough time for mine operators 
to take necessary steps to achieve successful compliance. Under the 
existing standards, both MNM and coal operators have had many years of 
experience with monitoring and controlling airborne contaminants, 
including respirable crystalline silica, and this experience should 
facilitate

[[Page 44902]]

implementation of the proposed standard.
2. Section 60.2--Definitions
    This section includes the proposed definitions of four terms: 
``action level,'' ``objective data,'' ``respirable crystalline 
silica,'' and ``specialist.''
    The term ``action level'' would mean 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). The action level sets the level of respirable 
crystalline silica concentration at or above which operators would be 
subject to periodic sampling requirements, which are explained in 
proposed Sec.  60.12. This proposed action level is intended to support 
operator compliance with the proposed PEL of 50 [micro]g/m\3\ by 
initiating periodic sampling requirements.
    The proposed action level of 25 [mu]g/m\3\, one-half of the 
proposed PEL, is consistent with NIOSH research findings and other MSHA 
standards. 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 has experience with 
setting an action level equivalent to 50 percent of the PEL for 
occupational noise exposure (30 CFR 62.101), applicable to MNM and coal 
mines, and an action level of 50 percent of the exhaust gas monitoring 
standards for underground coal mines (30 CFR 70.1900). Based upon 
Agency experience, MSHA believes these action levels have allowed mine 
operators to be more proactive in providing necessary protection.
    The term ``objective data'' would mean 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. Such 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. Some examples of information that would qualify as 
objective data under this definition include historical MSHA sampling 
data, NIOSH Health Hazard Evaluations and other published scientific 
reports, and industry-wide surveys compiled from mines with similar 
mining conditions, geological composition, work processes, miner tasks, 
and the same commodities.
    ``Respirable crystalline silica'' would mean 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. These characteristics are described further below.
    First, the proposed definition would apply to airborne particles 
that contain collectively or individually, quartz, cristobalite, and/or 
tridymite, three polymorphs of respirable crystalline silica that may 
be encountered in mining and for which exposures are addressed in 
existing MSHA standards. Quartz is the most common polymorph and is 
present in varying amounts in almost every type of mineral, whereas 
naturally occurring cristobalite and tridymite are rare.
    Second, airborne particles determined to be respirable are those 
particles capable of entering the gas-exchange region (alveolar region) 
of the lungs. MSHA's proposed definition would harmonize the Agency's 
existing practice with current aerosol science and be consistent with 
the nationally and internationally accepted ISO definition of 
``respirable particulate mass'' (i.e., the respirable mass fraction of 
total airborne particles that can be inhaled through the nose or 
mouth). ISO 7708:1995 defines conventions for the ``inhalable,'' 
``thoracic,'' and ``respirable'' fractions of total airborne particles. 
The inhalable fraction represents the fraction of total airborne 
particles capable of being inhaled through the nose or mouth. The 
thoracic fraction is the portion of the inhalable particles that pass 
the larynx and into the airways (trachea) and the bronchial region of 
the lungs. The respirable fraction is the portion of inhalable 
particles that can enter the gas-exchange region (alveolar region) of 
the lungs. The ISO 7708:1995 definition of ``respirable particulate 
mass'' corresponds to particulate matter (respirable dust) that is 
inhaled and capable of entering the gas-exchange region (alveolar 
region) of the lungs. MSHA considers this definition to be biologically 
relevant because exposures to airborne contaminants that are respirable 
can lead to material impairment of health or functional capacity.\23\
---------------------------------------------------------------------------

    \23\ The gas-exchange region of the human lung is the region 
where the exchange of carbon dioxide and oxygen occurs between the 
lung and blood and includes the alveoli and respiratory bronchioles.
---------------------------------------------------------------------------

    Third, respirable particles are those particles which can be 
collected by a sampling device designed to meet the characteristics for 
respirable-particle-size-selective samplers that conform to the ISO 
7708:1995 standard. While ``respirable dust'' generally refers to dust 
particles having an aerodynamic diameter of 10 micrometers ([mu]m) or 
less, ISO 7708:1995 defines the term more precisely based on the 
respiratory system's efficiency at collecting different types and sizes 
of particles. Collection efficiency is represented by particle 
collection efficiency curves based on the aerodynamic diameter of 
particles.\24\ The ISO 7708:1995 standard uses particle collection 
efficiency curves to approximate the fraction of respirable particles 
that can be deposited in the alveolar region of the human respiratory 
tract. A sampling device that conforms to the ISO 7708:1995 standard 
would ensure the collection of only respirable particles, including 
crystalline silica polymorphs.
---------------------------------------------------------------------------

    \24\ The ISO 7708:1995 standard defines aerodynamic diameter as 
the ``diameter of a sphere of density 1 g/cm\3\ with the same 
terminal velocity due to gravitational force in calm air as the 
particle, under the prevailing conditions of temperature, pressure, 
and relative humidity.''
---------------------------------------------------------------------------

    MSHA believes that the proposed definition of respirable 
crystalline silica has two main advantages. First, because the ISO 
7708:1995 definition of respirable particulate mass represents an 
international consensus, adoption of the ISO 7708:1995 criterion would 
allow harmonization with 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 proposed definition 
would eliminate inconsistencies in the existing standards for MNM and 
coal mines. Under the proposal, 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 would provide consistency across the different mining 
sectors. Using samplers that conform to ISO 7708:1995 would allow for 
uniform collection for these three polymorphs. The proposed streamlined 
approach would facilitate compliance and provide consistency in the 
development of best practices and would allow mine operators and MSHA 
to better promote the health and safety of all miners.

[[Page 44903]]

    ``Specialist'' would mean an American Board-Certified Specialist in 
Pulmonary Disease or an American Board-Certified Specialist in 
Occupational Medicine. The proposed definition is applicable to 
proposed Sec.  60.15, which addresses medical surveillance for MNM 
miners. Under the proposed medical surveillance requirements, which 
will be discussed later, MNM mine operators would be required to 
provide miners with medical examinations performed by a specialist in 
pulmonary disease or occupational medicine or a PLHCP.
3. Section 60.10--Permissible Exposure Limit (PEL)
    This section establishes a single, uniform PEL of 50 [mu]g/m\3\ for 
respirable crystalline silica for all mines. Under this proposed 
provision, mine operators would be required to 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.'' For coal mines, this proposal would establish a 
separate PEL for respirable crystalline silica. This proposed PEL would 
replace the Agency's existing exposure limits for respirable 
crystalline silica or respirable quartz in 30 CFR parts 56, 57, 70, 71, 
and 90.
    The proposed PEL is consistent with NIOSH's recommended exposure 
limit for workers and with the PEL for respirable crystalline silica 
covering U.S. workplaces regulated by OSHA. NIOSH recommended in 1974 
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 1910.1053(c); 29 CFR 1926.1153(d)(1)).\25\ 
MSHA's 2014 rule on respirable coal mine dust established that the 
average concentration of respirable dust in the mine atmosphere during 
each shift to which each miner is exposed be at or below 1.5 mg/m\3\, 
calculated as a TWA, and that coal miners' exposure to respirable 
crystalline silica be regulated through reductions in the overall 
respirable dust standard (30 CFR 70.100, 70.101, 71.100, 71.101, 
90.100, and 90.101).\26\
---------------------------------------------------------------------------

    \25\ 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.
    \26\ For Part 90 miners, MSHA lowered the exposure to respirable 
coal mine dust during a coal miner's shift to not exceed 0.5 mg/
m\3\.
---------------------------------------------------------------------------

    As discussed in the Health Effects Summary of this preamble, 
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. However, 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.
    As presented in the PRA, MSHA has preliminarily determined that: 
(1) under existing respirable crystalline silica or quartz standards, 
miners are exposed to respirable crystalline silica at concentrations 
that result in a risk of material impairment of health or functional 
capacity; and (2) that lowering the PEL to 50 [mu]g/m\3\ would 
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.\27\ Evidence in the standalone Health Effects document 
demonstrates that exposure to respirable crystalline silica at levels 
permitted under existing standards contributes to this excess 
mortality.
---------------------------------------------------------------------------

    \27\ 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. The NOMS database provides detailed 
mortality data for the 11-year period from 1999, 2003 to 2004, and 
2007 to 2014. https://;wwwn.cdc.gov/niosh-noms/industry2.aspx; 
accessed November 7, 2022.
---------------------------------------------------------------------------

    In the case of coal mines, the proposed rule would establish a 
separate PEL for respirable crystalline silica. Under the existing 
standard, miners' exposure to quartz is tied to exposure to respirable 
coal mine dust, making it more difficult to monitor coal miners' 
exposure to respirable crystalline silica. The proposed separate 
standard would be more transparent and make compliance easier to track, 
allowing more effective control of respirable crystalline silica.
    The proposed PEL of 50 [mu]g/m\3\ applies to a miner's full-shift 
exposure, calculated as an 8-hour TWA. Under this proposal, a miner's 
work shift exposure would be calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.023

    Regardless of a miner's actual working hours (full shift), 480 
minutes would be used in the denominator. This means that the 
respirable crystalline silica collected over an extended period (e.g., 
a 12-hour shift) would be 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 on the sample, the miner's respirable crystalline silica 8-
hour TWA exposure would be 67.4 [mu]g/m\3\, calculated as follows:
[GRAPHIC] [TIFF OMITTED] TP13JY23.024


[[Page 44904]]


    This proposed calculation method is the one that MSHA uses to 
calculate MNM miner exposures to respirable crystalline silica and 
other airborne contaminants; it differs from the existing method of 
calculating a coal miner's exposure to respirable coal mine dust. For 
coal miners, the existing calculation method uses the entire duration 
of a miner's work shift in both the denominator and numerator, 
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.
    MSHA's proposal to apply the existing method of calculating MNM 
miner exposure to all miners has two main advantages. First, the 
proposal would improve protection for coal miners who work longer 
shifts. The goal of the proposed respirable crystalline silica PEL is 
to prevent miners from suffering a body burden high enough to cause 
adverse health effects. If a miner works longer than 8 hours, the 
miner's body (lungs, in particular) may not have sufficient time to 
eliminate the respirable crystalline silica that enters the lungs or to 
reduce the body burden.\28\ Coal miners commonly work extended shifts, 
with many working 10-hour or longer shifts.\29\ In such cases, a coal 
miner's recovery time would be reduced from 16 hours to 12 to 14 hours. 
To account for this increased risk, the proposed calculation (like the 
current MNM calculation method) normalizes to an 8-hour TWA. The 
concept of adjusting occupational exposure limits for ``extended 
shifts'' has been addressed by researchers (Brief and Scala, 1986; 
Elias, 2013).
---------------------------------------------------------------------------

    \28\ The pulmonary uptake and clearance of respirable 
crystalline silica 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 will also affect the time to clear particles, even 
after exposure ceases. Of principal concern is the possibility that 
a continuous dust exposure over an extended period of time (or high 
dust level exposure during a short exposure period may excessively 
tax lung defense mechanisms (Industrial Minerals Association-North 
America and Mine Safety and Health Administration, 2008).
    The ACGIH (2022), while not specifically addressing silica, has 
stated, ``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-hours/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 (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.''
    \29\ 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. The coal mine dust samples are available at Mine Data 
Retrieval System [verbar] Mine Safety and Health Administration 
(MSHA).
---------------------------------------------------------------------------

    Second, applying the proposed calculation method for all miners 
would be more straightforward and easier to understand for mine 
operators, miners, and other stakeholders. The current calculation 
method for coal miners requires first determining the percentage of 
quartz in the sample of collected respirable dust, then dividing the 
result into the number 10 to calculate an exposure limit for respirable 
dust. The proposed calculation method requires only measuring the total 
mass of respirable crystalline silica collected and dividing it by the 
air volume over 480 minutes.
    This proposal would establish a lower PEL and apply it to all 
miners using a consistent method for calculating exposures. These 
changes would improve the health and safety of miners while making 
compliance more straightforward and transparent. The 8-hour TWA is the 
``gold standard'' for exposure assessments, except in scenarios 
involving chemical substances that are predominantly fast-acting (i.e., 
those evoking acute effects). NIOSH has also supported the use of the 
TWA and discussed this term since the publication of the NIOSH Pocket 
Guide to Chemical Hazards (First Edition, 1973) (the ``White Book'').
4. Section 60.11--Methods of Compliance
    This proposed section would require mine operators to install, use, 
and maintain feasible engineering and administrative controls to keep 
each miner's exposure to respirable crystalline silica at or below the 
proposed PEL. Mine operators would be required to use feasible 
engineering controls as the primary means of controlling respirable 
crystalline silica; administrative controls would be used, when 
necessary, as a supplementary control. However, under the proposal, 
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--would be prohibited. Under the proposal, 
respiratory protection equipment could be used in specific and limited 
situations, as discussed in Sec.  60.14--Respiratory Protection, but 
the use of respiratory protection equipment would not be acceptable as 
a method of compliance.
    This proposed approach to controlling miners' exposures is 
consistent with MSHA's existing standards, NIOSH's recommendations, and 
generally accepted industrial hygiene principles. The proposal is 
consistent with MSHA's existing respirable dust standards, which 
require engineering controls as the primary means to protect miners. 
MSHA's experience and data show that engineering controls provide 
improved, more consistent, and more reliable protection for miners than 
administrative controls or respirators. In its recommendations, NIOSH 
also stressed the importance of using engineering controls to control 
miners' exposure to respirable crystalline silica. In 1995, NIOSH 
recommended that the dust standard state 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 1995a). In its public response to MSHA's 2019 
Request for Information for Respirable Silica (Quartz) (84 FR 45452, 
Aug. 29, 2019), NIOSH also supported the use of engineering controls as 
the primary means of protecting miners from exposure to respirable 
crystalline silica, stating 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.'' \30\
---------------------------------------------------------------------------

    \30\ Comment from Paul Schulte, NIOSH (Oct. 23, 2019) to Docket 
No. MSHA 2016-0013.
---------------------------------------------------------------------------

    As discussed in the technological feasibility and preliminary 
regulatory impact analysis sections of the preamble, MSHA has 
preliminarily determined that engineering and administrative controls 
are technologically and economically feasible, and the use of these 
controls would be sufficient to achieve compliance with the proposed 
PEL. After reviewing the effectiveness of various exposure reduction 
controls which are currently available and have been successfully 
adopted in various combinations in mines, MSHA has concluded that all 
mine operators can ensure miners' exposures are below the proposed PEL 
through implementing some combination of enhanced

[[Page 44905]]

maintenance of existing engineering controls, new engineering controls, 
and improved administrative controls/work practices.
a. Engineering Controls
    Proposed paragraph (a) would require mine operators to use feasible 
engineering controls as the primary means of controlling respirable 
crystalline silica; administrative controls would be used, when 
necessary, as a supplementary control.
    This proposed paragraph would require engineering controls to be 
used as the primary means of controlling respirable crystalline silica. 
Engineering controls can include ventilation systems (i.e., main, 
auxiliary, local exhaust), dust suppression devices (i.e., wet dust 
suppression and airborne capture), and enclosed cabs or control booths 
with filtered breathing air, as well as changes in materials handling, 
equipment used in a process, ventilation, and dust capture mechanisms. 
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 use of video cameras for remote scanning and monitoring can also 
help to reduce or eliminate miners' exposures to respirable crystalline 
silica.
    Engineering controls are the most effective means of controlling 
the amount of dust to which miners are exposed. They have the advantage 
of addressing dust at its source, thus ensuring that all miners in an 
area are adequately protected from overexposure to respirable 
crystalline silica. Engineering controls provide more consistent and 
more reliable protection to miners than other interventions because the 
controls are not dependent on an individual's performance, supervision, 
or intervention to function as intended. In contrast to other controls 
and other interventions, engineering controls can also be continually 
evaluated and monitored relatively easily, allowing their effectiveness 
to be assessed regularly.
b. Administrative Controls
    Under the proposed rule, mine operators would be permitted to 
supplement engineering controls with administrative controls as a means 
of controlling exposure to respirable crystalline silica. 
Administrative controls include practices that change the way tasks are 
performed to reduce a miner's exposure. These practices would include 
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.
    Administrative controls require significant effort by mine 
operators to ensure that miners understand and follow the controls. If 
not properly implemented, understood, or followed, or if persons 
responsible for administrative controls do not properly supervise their 
implementation, they would not be effective in controlling miners' 
overexposure to respirable crystalline silica. Therefore, 
administrative controls would be permitted only as supplementary 
measures, with engineering controls required as the primary means of 
protection.
    Proposed paragraph (b) would prohibit mine operators from using 
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--as an acceptable method of compliance. MSHA 
does not believe that rotation of miners is consistent with the 
Agency's regulatory framework or its mandate under the Mine Act. Based 
on MSHA's experience, rotation of miners may, if permitted, reduce the 
amount of time each miner is exposed to the hazard by rotating miners 
out of the task faster. However, it would increase the number of miners 
working in high-exposure tasks or areas and would lead to increased 
material impairment of health or functional capacity for the additional 
miners.
    The concept of miner rotation, which may be an appropriate control 
to minimize musculoskeletal stress, is not acceptable for work 
involving carcinogens. Based on NIOSH's publication entitled ``Current 
Intelligence Bulletin 68: NIOSH Chemical Carcinogen Policy,'' MSHA 
believes that the primary way to prevent occupational cancer is to 
reduce worker exposure to chemical carcinogens as much as possible 
through elimination or substitution at the source and through 
engineering controls (NIOSH 2017b).
5. Section 60.12--Exposure Monitoring
    The proposed section addresses exposure monitoring, sampling 
method, and sample analysis methods. MSHA is proposing two types of 
exposure monitoring: quantitative, through sampling the air that miners 
breathe, and qualitative, through semi-annual evaluations of how 
changes in mining processes, production activities, and dust control 
systems affect exposures. For the quantitative monitoring, MSHA is 
proposing four types of sampling--baseline, periodic, corrective 
actions, and post-evaluation--together with methods for sampling and 
analyzing the samples.
    The proposed exposure monitoring requirements, which include 
sampling miners' exposures, would facilitate operator compliance with 
the proposed PEL, harmonize MSHA's approach to monitoring and 
evaluating respirable crystalline silica exposures in both MNM and coal 
mines, and lead to better protection of miners' health. Monitoring 
miner exposures to airborne contaminants is an effective risk 
management tool. The sampling and evaluation requirements of proposed 
Sec.  60.12 are designed to ensure maximum protection for miners and 
prevent them from suffering material impairment of health or functional 
capacity, while providing operators flexibility to tailor their 
sampling program to the miners' risk of exposure to respirable 
crystalline silica at their mines.
    The first type of exposure monitoring under the proposed rule is 
quantitative sampling for miners' exposures to respirable crystalline 
silica. This sampling would help mine operators determine the extent 
and degree of exposures, identify sources of exposure and potential 
overexposure, maintain updated and accurate records of exposures, 
select the most appropriate control methods, and evaluate the 
effectiveness of those controls. The proposal would require operators 
to conduct sampling for a miner's regular full shift during typical 
mining activities. The second type of exposure monitoring under the 
proposed rule would be qualitative evaluations, which would help 
operators identify changes in mining conditions and processes that 
affect the exposure risk to miners.
a. Section 60.12(a)--Baseline Sampling
    The first action mine operators would take to assess miners' 
exposures under the proposed rule would be to conduct baseline 
sampling. Baseline sampling would provide an initial measurement of 
respirable crystalline silica exposures that would be compared to the 
proposed action level and the proposed PEL to determine the 
effectiveness of existing controls and the need for additional 
controls.
    Proposed paragraph (a)(1) would require mine operators to perform 
baseline sampling to assess the full-shift, 8-hour TWA exposure of 
respirable crystalline silica for each

[[Page 44906]]

miner who is or may reasonably be expected to be exposed to respirable 
crystalline silica at any level. MSHA assumes that most mining 
occupations related to extraction and processing would meet the 
``reasonably be expected'' threshold; however, MSHA recognizes that 
some miners may work in areas or perform tasks where exposures are not 
reasonably likely, and some miners may work in silica-free 
environments. Based on the Agency's experience, both MNM and coal mine 
operators generally know from their existing sampling data and MSHA's 
sampling data the occupations, work areas, and work activities where 
respirable crystalline silica exposures occur. The mine operator would 
be required to sample only those miners the operator knows or 
reasonably expects to be exposed to respirable crystalline silica.
    The proposed provisions would require that, within the first 180 
days after the effective date of the final rule, the mine operator 
perform the baseline sampling. During this 180-day period, mine 
operators would acquire necessary sampling devices or sampling 
services, sample occupations or areas of known or reasonably expected 
exposures, identify appropriate laboratories, and arrange for analysis 
of samples. Given that the mining industry has experience with sampling 
programs for other airborne contaminants, as well as respirable 
crystalline silica, MSHA anticipates that the proposed 180 days would 
provide sufficient time for mine operators to comply with the proposed 
standard.
    Under this proposed standard, mine operators would need to 
accurately characterize the exposure of each miner who is or may 
reasonably be expected to be exposed to respirable crystalline silica. 
As discussed later in detail, mine operators would be permitted to use 
representative sampling whenever sampling is required. In some cases, 
however, operators may have to sample all miners to obtain an accurate 
assessment of exposures.
    This proposed requirement would ensure that mine operators have the 
quantitative information needed to evaluate miners' exposure risks, 
determine the adequacy of existing engineering and administrative 
controls, and make necessary changes to ensure miners are not 
overexposed. In addition, the results of the baseline sampling would 
determine further operator obligations for periodic sampling. A 
baseline sample result at or above the proposed action level but at or 
below the proposed PEL, would require operators to conduct periodic 
sampling under proposed Sec.  60.12(b). However, if the baseline sample 
indicated that exposures were below the proposed action level and 
operators can confirm those results, mine operators would not be 
required to conduct periodic sampling. The results can be confirmed in 
three ways: (1) sample data, collected by the operator or the Secretary 
in the 12 months preceding the baseline sampling, that also shows 
exposures below the proposed action level; (2) objective data (as 
defined in the proposal) confirming that a miner's exposure to 
respirable crystalline silica would remain below the proposed action 
level; or (3) another sample taken within 3 months showing exposure 
below the proposed action level.
    Proposed paragraph (a)(2) would allow mine operators to use 
objective data to confirm the baseline sample result. Under this 
proposal, objective data must demonstrate that respirable crystalline 
silica would not be released in airborne concentrations at or above the 
action level under any expected conditions. Objective data, as defined 
in proposed Sec.  60.2, would include air monitoring data from 
industry-wide surveys that demonstrate miners' exposure to respirable 
crystalline silica associated with a particular product or material or 
a specific process, task, or activity. Objective data must reflect 
mining conditions that closely resemble the processes, material, 
control methods, work practices, and environmental conditions in the 
mine operator's current operations. The mine operator would have the 
burden of showing that the objective data characterizes miner exposures 
to respirable crystalline silica with sufficient accuracy.
    Also, proposed paragraph (a)(2) would permit mine operators to use 
sampling conducted by the Secretary or mine operator within the 
preceding 12 months of baseline sampling to confirm miner exposures 
below the proposed action level. The proposed rule would require mine 
operator sampling that was conducted in accordance with sampling 
requirements in paragraph (f) and analyzed according to paragraph (g) 
of this section. Under proposed paragraph (a)(2), any subsequent 
sampling conducted by the operator or by the Secretary, collected 
within 3 months of the baseline sample, could also be used to confirm a 
baseline sample result.
    MSHA believes that before sampling is discontinued for miners 
previously determined to be exposed at or above the proposed action 
level, it is necessary to confirm any sample result that indicates 
miner exposures are below the proposed action level. When such a result 
is confirmed by a second measurement, an operator could reasonably 
expect exposures to remain below the action level if mining conditions 
and practices do not change. However, as discussed later, under 
proposed paragraph (d), if there is any change in conditions or 
practices that could be reasonably expected to result in exposures at 
or above the action level, sampling to assess these exposures would be 
required.
b. Section 60.12(b)--Periodic Sampling
    Periodic sampling under the proposed rule would provide mine 
operators and miners with regular information about miners' exposures. 
Changes in exposure levels can be caused by changes in the mine 
environment, inadequate engineering controls, or other changes in 
mining processes or procedures. Periodic sampling would inform mine 
operators about increases in exposures in a timely manner so they can 
prevent potential overexposures. In addition, periodic sampling alerts 
operators and miners of the continued need to protect against the 
hazards associated with exposure to respirable crystalline silica. If a 
mine operator installs new engineering controls and/or starts new 
administrative control practices, periodic sampling would show whether 
those controls are working properly to achieve the anticipated health 
results and would document their effectiveness.
    Proposed Sec.  60.12(b) would require periodic sampling of miners' 
exposures to respirable crystalline silica whenever the most recent 
sampling indicates that exposures are at or above the proposed action 
level but at or below the proposed PEL. Whether a mine operator would 
have to conduct periodic sampling under the proposal would depend on 
the results of the most recent sample, which could include a baseline 
sample, a corrective actions sample, or a post-evaluation sample, as 
well as samples taken by MSHA during its inspections. If operators are 
required to conduct periodic sampling, and periodic sampling results 
indicate that miner exposures are below the action level, a mine 
operator would be permitted to discontinue periodic sampling for those 
miners whose exposures are represented by these samples. If the most 
recent sample shows exposures at or above the action level but at or 
below the proposed PEL, periodic sampling every 3 months would continue 
until two consecutive sample analyses showed miners' exposures below 
the action level. MSHA believes that two consecutive sample analyses 
showing exposures below the

[[Page 44907]]

action level would indicate a low probability that prevailing mining 
conditions would result in overexposures.
    MSHA believes that the proposed frequency for periodic sampling--
repeating the sampling within 3 months--is practical for mine operators 
and protective of the health and safety of miners. MSHA has 
preliminarily concluded that the health risks caused by respirable 
crystalline silica overexposure warrant more regular sampling when 
exposure levels approach the proposed PEL, because this periodic 
sampling would provide a higher level of confidence that miners would 
not be overexposed. Due to the unique conditions of mining 
environments, where conditions change quickly and exposures to 
respirable crystalline silica can vary frequently, MSHA is proposing a 
three-month periodic sampling schedule (NIOSH, 2014e). This three-month 
schedule would provide a meaningful degree of confidence that mine 
operators would recognize quickly when exposures are increasing and 
approaching the proposed PEL and would respond by implementing 
additional controls to prevent overexposure. Periodic sampling data 
would also provide information that operators could use to select, 
implement, and maintain controls. MSHA has structured the proposal to 
balance the costs of periodic sampling requirements, including when 
sampling can be stopped, and the benefits of additional health 
protection for miners. Taking these factors into consideration, MSHA 
has preliminarily determined that the proposed frequency of periodic 
sampling is both economically and technologically feasible for mine 
operators. (See Section VIII. Technological Feasibility and Section IX. 
Summary of Preliminary Regulatory Impact Analysis.)
    As with the baseline sampling in proposed paragraph (a), in meeting 
the requirements of this paragraph, mine operators would be allowed to 
sample a representative fraction of at least two miners. The exposure 
result would be attributed to the remaining miners represented by this 
sample, as discussed in more detail below. When miners are not 
performing the same job under the same working conditions, a 
representative sample would not accurately characterize actual 
exposures, and individual samples would be necessary.
c. Section 60.12(c)--Corrective Actions Sampling
    Under the proposed rule, MSHA would require mine operators to take 
corrective actions when any sampling shows exposures above the proposed 
PEL. After such corrective actions, proposed Sec.  60.12(c) would 
require mine operators to conduct corrective actions sampling to 
determine whether the control measures taken under proposed Sec.  60.13 
have reduced miner exposures to respirable crystalline silica to at or 
below the proposed PEL. If not, the mine operator would be required to 
take additional or new corrective actions until subsequent corrective 
actions sampling indicates miner exposures are at or below the proposed 
PEL.
    Once corrective actions sampling indicates that miner exposures 
have been lowered to levels at or below the proposed PEL, one of two 
scenarios could occur. First, if corrective actions sampling taken 
under proposed Sec.  60.12(c) indicate that miner exposures are at or 
below the proposed PEL, but at or above the proposed action level, the 
mine operator would be required to conduct periodic sampling as 
described in proposed Sec.  60.12(b). The periodic sampling 
requirements would require mine operators to continue to conduct 
sampling every three months until two consecutive sampling results 
indicate miners' exposures are below the action level. Second, if 
corrective actions sampling taken under proposed Sec.  60.12(c) 
indicate that miner exposures are below the proposed action level, the 
mine operator would be required to conduct a subsequent sample within 3 
months as described in proposed Sec.  60.12(b); if those results show 
miners' exposures are below the action level, the mine operator could 
discontinue periodic sampling.
    Sampling after corrective actions would provide operators with 
specific information regarding the effectiveness of the corrective 
actions for the mine environment and provide additional data for use in 
making decisions about updating or improving controls. It would also 
provide mine operators with an updated profile of miners' exposures 
against which future samples could be compared.
d. Section 60.12(d) and (e)--Semi-Annual Evaluation and Post-Evaluation 
Sampling
    Historically, MSHA has recognized the importance of qualitatively 
evaluating changes in mining conditions and processes and assessing the 
effect of those changes on exposure risk. Operators have general 
experience with these types of evaluations. The proposed rule would 
require mine operators to qualitatively evaluate any changes in 
production, processes, engineering controls, personnel, administrative 
controls, or other factors including geological characteristics that 
might result in new or increased respirable crystalline silica 
exposures, beginning 18 months after the effective date and every 6 
months thereafter. Such evaluations could identify changes in miners' 
exposures to respirable crystalline silica.
    The proposed semi-annual evaluation, and post-evaluation sampling, 
as appropriate, would help confirm that the results of baseline and 
periodic sampling continue to accurately represent current exposure 
conditions. These proposed semi-annual evaluation and sampling 
requirements would also enable mine operators to take appropriate 
actions to protect exposed miners, such as implementing new or 
additional engineering controls, and would provide information to 
miners and their representatives, as necessary. An evaluation could 
identify a change in operation processes or control measures that might 
lead to increased exposures to respirable crystalline silica which need 
to be corrected. Under proposed paragraph (d)(1), the mine operator 
would be required to make a record of the evaluation, including the 
date of the evaluation. Under proposed paragraph (d)(2), the mine 
operator would be required to post the record on the mine bulletin 
board, and, if applicable, make the evaluation available 
electronically, for the next 31 days.
    Once the evaluation is complete, a mine operator would be required 
to conduct post-evaluation sampling under proposed Sec.  60.12(e) when 
the results of the evaluation show that miners may be exposed at or 
above the action level. Post-evaluation sampling would provide 
operators with information on whether existing controls are effective, 
whether additional control measures are needed, and whether respiratory 
protection is appropriate. When post-evaluation samples indicate that 
miner exposures are at or above the proposed action level, the mine 
operator would be required to conduct periodic sampling as described in 
proposed paragraph (b). Post-evaluation sampling, however, would not be 
required if the mine operator determines that mining conditions would 
not reasonably be expected to result in exposures at or above the 
action level.
e. Section 60.12(f)--Sampling Requirements
    Knowledge of typical respirable dust exposure levels is critical to 
protect the health of miners. The proposed rule includes certain 
sampling requirements that would ensure mine operators'

[[Page 44908]]

respirable crystalline silica monitoring is representative of miners' 
actual exposures.
(1) Typical Mining Activities and Sampling Device Placement
    Proposed paragraph (f)(1) would require mine operators to collect a 
respirable dust sample for the duration of a miner's regular full shift 
and during typical mining activities. Many potential sources of 
respirable crystalline silica are present only when the mine is 
operating under typical conditions. If a sample is not taken during 
typical mining activities, the actual risk to the miner may not be 
known. This proposed requirement would ensure that respirable 
crystalline silica exposure data accurately reflect actual levels of 
respirable crystalline silica exposure at miners' normal or regular 
workplaces throughout their typical workday, even if there are 
fluctuations in airborne contaminant concentrations during a work 
shift. As discussed in other sections of this preamble, the sample 
results from the full shift would be calculated as an 8-hour TWA 
concentration for comparison with the proposed action level and PEL and 
for compliance determinations.
    This proposed provision is consistent with existing standards and 
with generally accepted industrial hygiene principles, which recommend 
taking into consideration the entire duration of time a miner is 
exposed to an airborne contaminant, even if it exceeds 8 hours. Based 
on Agency data and experience, MSHA anticipates that operators would 
not have major challenges in meeting these sampling requirements.
    This proposal would continue existing procedures for sampling 
device placement during sampling. Under proposed Sec.  60.12(f)(2)(i), 
for MNM miners the regular full-shift, 8-hour TWA exposure would be 
based on personal breathing-zone air samples. A breathing zone sample 
is an individual sample that characterizes a miner's exposure to 
respirable crystalline silica during an entire work shift. More 
specifically, the sampler remains with the miner for the entire shift, 
regardless of the task or occupation performed.
    For coal miners, under proposed Sec.  60.12(f)(2)(ii), the regular 
full-shift, 8-hour TWA exposure would be based on an occupational 
environmental sample collected in compliance with existing standards 
found in Sec. Sec.  70.201(c), 71.201(b), and 90.201(b). Under the 
existing standards, the sampling device would be worn or carried 
``portal-to-portal,'' meaning from the time the miner enters the mine 
until the miner exits the mine. The sampling device would remain with 
the miner during the entire shift. For shifts that exceed 12 hours, the 
operator would be required to switch the sampling pump prior to the 
13th-hour of operation. However, except in the case of Part 90 miners, 
if a miner who is being sampled changes positions or duties, the 
sampling device would remain with the position or duty chosen for 
sampling (rather than the miner). For Part 90 miners, the sampling 
device would be operated portal-to-portal and would remain operational 
with the miner throughout the Part 90 miner's entire shift, which would 
include the time spent performing normal work duties and the time spent 
traveling to and from the assigned work location.
(2) Representative Sampling
    Under the proposed rule, mine operators must accurately 
characterize miners' exposure to respirable crystalline silica. In some 
cases, this would require sampling all exposed miners. In other cases, 
as proposed in paragraph (f)(3), sampling a ``representative'' fraction 
of miners would be sufficient. Where several miners perform the same 
tasks on the same shift and in the same work area, the mine operator 
could sample a representative fraction of miners. Under this proposed 
rule, a representative fraction of miners would consist of two or more 
miners performing the same tasks on the same shift and in the same work 
area and who are expected to have the highest exposures of all the 
miners in an area. 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 would then be 
attributed to the remaining miners in the group. When miners are not 
performing the same job under the same working conditions, a 
representative sample would not be sufficient to characterize actual 
exposures, and therefore individual samples would be necessary.
    MSHA has determined that requiring operators to sample at least two 
miners as representative, where they perform the same tasks on the same 
shift and in the same work area as the remaining miners, would be 
sufficient to ensure that exposures are accurately characterized and 
health protections are provided. This representative sampling provision 
of the proposal is similar to the approach that OSHA uses for both 
general industry (29 CFR 1910.1053(d)(3)) and construction (29 CFR 
1926.1153(d)(2)) under the scheduled sampling options.
(3) Sampling Devices
    Respirable dust sampling assesses the ambient air quality in mines 
and evaluates miners' exposure to airborne contaminants. Respirable 
dust comprises particles small enough that, when inhaled, can reach the 
gas exchange region of the lung. Measurement of respirable dust 
exposure is based on the collection efficiency of the human respiratory 
system and the separation of airborne particles by size to assess their 
respirable fraction. Proposed paragraph (f)(4) would require mine 
operators to use sampling devices designed to meet the characteristics 
for respirable-particle-size-selective samplers that conform to the ISO 
7708:1995, ``Air Quality--Particle Size Fraction Definitions for 
Health-Related Sampling,'' Edition 1, 1995-04 to determine compliance 
with the proposed respirable crystalline silica action level and PEL. 
MSHA proposes to incorporate by reference 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. Mine 
operators could use any type of sampling device they wish for 
respirable crystalline silica sampling, 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, meets MSHA permissibility requirements.\31\
---------------------------------------------------------------------------

    \31\ MSHA's permissibility requirements are specified in 30 CFR 
parts 18 and 74. Part 18, Electric Motor-Driven Mine Equipment and 
Accessories, specifies the procedures and requirements for obtaining 
MSHA approval, certification, extension, or acceptance of electrical 
equipment intended for use in gassy mines. Part 74, Coal Mine Dust 
Sampling Devices, specifies the requirements for evaluation and 
testing for permissibility of coal mine dust sampling devices.
---------------------------------------------------------------------------

    Sampling devices, such as cyclones \32\ and elutriators,\33\ can 
separate the

[[Page 44909]]

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.
---------------------------------------------------------------------------

    \32\ 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.
    \33\ 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.
---------------------------------------------------------------------------

    MSHA and many mine operators use cyclone samplers. 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 proposed rule. MSHA 
reviewed OSHA's feasibility analysis for its 2016 silica final rule and 
agrees with OSHA 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 proposed action level and PEL (OSHA 2016a) Such cyclone 
samplers include the Dorr-Oliver 10-mm nylon cyclone used by MSHA and 
many mine operators, 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 preliminary 
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 proposed 
action level and would 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 could continue to use these samplers at a flow rate of 1.7 L/
min, which conforms to the ISO standard, to comply with the proposed 
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 
could be adjusted to operate at a flow rate of 1.7 L/min to conform to 
the ISO standard.
    NIOSH's rapid field-based quartz monitoring (RQM) approach is 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.\34\ The current RQM monitor, 
however, was designed as an engineering tool; it is not currently 
designed as a compliance tool with tamper-proof components and is 
susceptible to interferences which can affect its accuracy. This means 
that the integrity of the sample cannot be guaranteed, and therefore 
the monitor cannot be used as a compliance tool. MSHA continues to 
support NIOSH efforts to develop the RQM monitor for use in mines.
---------------------------------------------------------------------------

    \34\ National Institute for Occupational Safety and Health 
(NIOSH). 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. 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.
---------------------------------------------------------------------------

f. Section 60.12 (g)--Methods of Sample Analysis.
    Proposed paragraph (g) 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 analyzed. 
Proposed paragraph (g)(1) would require mine operators 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 the 
International Organization for Standardization and the International 
Electrotechnical Commission (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 17025 and other criteria appropriate for the scope of the 
accreditation.
    Many MNM mine operators currently use third-party laboratories to 
perform respirable crystalline silica sample analyses, and under the 
proposed standard, MSHA anticipates that they would continue to use 
third-party laboratories.
    For most coal mine operators, using a third-party accredited 
laboratory to

[[Page 44910]]

analyze respirable crystalline silica samples would be a new 
requirement because respirable coal mine dust samples are currently 
analyzed only by MSHA. Under the proposed standard, all mine operators 
would have to use third-party laboratories accredited to ISO/IEC 17025 
to have respirable dust samples analyzed for respirable crystalline 
silica. By requiring all mines to use third-party laboratories, 
proposed paragraph (g)(1) would ensure that sample analysis 
requirements and MSHA enforcement efforts are consistent across all 
mines.
    Proposed paragraph (g)(2) would require 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 cited by third party 
accredited labs for measuring respirable crystalline silica in mine 
dust matrices. 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. All three methods, MSHA P-2, 
NIOSH 7500, and OSHA ID-142 for analyzing respirable crystalline silica 
using X-ray diffraction (XRD) have similar procedures for measuring 
respirable crystalline silica and are capable of distinguishing between 
the three silica polymorphs. 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. 
Consistent with MSHA's current practices for the analysis of respirable 
crystalline silica samples, analytical techniques used for samples from 
MNM mines and coal mines would generally be different due to potential 
sources of interference and cost considerations. Under the proposed 
rule, as discussed below, MSHA expects that samples collected in MNM 
mines would continue to be analyzed by X-ray diffraction (XRD) and 
samples collected for coal mines would continue to be analyzed by 
Fourier transform infrared spectroscopy (FTIR).
    Coal mine samples are currently analyzed using the FTIR method 
because it is cheaper, faster, and better suited for the coal mining 
sector, where samples contain little or no minerals that could 
interfere or confound respirable crystalline silica analysis results. 
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. Unlike coal dust samples, MNM samples may have a 
variety of minerals present, which could cause interference with 
respirable crystalline silica measurements if FTIR were used. Thus, 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. The XRD method could be used for both MNM and 
coal samples but using the XRD method is more time consuming and more 
costly, with no additional benefit for coal mine sample analysis. For 
this reason, MSHA does not expect the use of XRD on samples from coal 
mines.
    For MNM samples, the methods used for respirable crystalline silica 
sample analysis using XRD include MSHA P-2, NIOSH 7500, and OSHA ID-
142. For coal samples, the methods used for respirable crystalline 
silica sample analysis using FTIR include MSHA P-7, NIOSH 7602, and 
NIOSH 7603. (OSHA does not currently have an established FTIR method 
for analysis of respirable crystalline silica.)
g. Section 60.12 (h)--Sampling Records
    Proposed paragraph (h) would establish requirements for sampling 
records, including what mine operators would be required to do after 
receiving the analytical reports from laboratories. For each sample 
taken, this proposed paragraph would require mine operators to create a 
record that includes the sample date, the sampled occupations, and the 
reported concentrations of both respirable dust and respirable 
crystalline silica. After making such a record, the mine operator would 
be required to post the record, together with the laboratory report, on 
the mine bulletin board and, if applicable, make the record and the 
laboratory report available electronically, for the next 31 days upon 
receipt.
    When electronic means are available, mine operators would be 
required to use those electronics means such as electronic bulletin 
boards or newsletters, in addition to physically posting the sampling 
record and laboratory report on the mine bulletin board. MSHA believes 
that most mines have the ability to display this information 
electronically. For any mines where electronic means are not available, 
mine operators would only be required to physically post the sampling 
record and laboratory report on the mine bulletin board. Also, as 
required in proposed Sec.  60.16(b), the sampling records created under 
this section 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.
    MSHA believes that the posted information including sampling 
results and methodology and other relevant information would inform 
miners of the sampled exposures and would encourage them to have 
heightened awareness of potential health hazards that could impact not 
only them but other miners. It would also provide them with knowledge 
to take proactive actions to protect themselves and fellow miners 
through better and safer work practices and more active participation 
in health and safety programs. This is consistent with the Mine Act 
which states that mine operators, with the assistance of miners, have 
the responsibility to prevent the existence of unsafe and unhealthful 
conditions and practices in mines. 30 U.S.C. 801(e). Making miners 
aware that respirable crystalline silica exposures below the PEL may 
still pose a health risk could encourage them to take steps to manage 
their health risks.
6. Section 60.13--Corrective Actions
    This proposed section includes several actions a mine operator 
would be required to take to protect miners' health and safety when any 
sampling result indicates that a miner's exposure to respirable 
crystalline silica exceeds the proposed PEL. Proposed paragraph (a)(1) 
would require the mine operator to make NIOSH-approved respirators 
available to affected miners before the start of the next work shift. 
Proposed paragraph (a)(2) would require mine operators to ensure that 
affected miners wear respirators for the full shift or during the 
period of overexposure to protect miners until miner exposures are at 
or below the PEL.
    Proposed paragraph (a)(3) would require operators to take immediate 
corrective actions to lower the concentration of respirable crystalline 
silica to levels at or below the PEL. Some examples of corrective 
actions include increasing air ventilation and/or water flow rates, 
adding more water sprays, and improving maintenance of the existing 
engineering controls.
    Once corrective actions have been taken, proposed paragraph 
(a)(4)(i) would require the operator to conduct sampling in accordance 
with Sec.  60.12(c) to determine if the corrective actions have been 
successful in lowering exposures to at or below the PEL. If sampling 
indicates that the corrective actions did not reduce miner exposures to 
at or below the PEL, proposed

[[Page 44911]]

paragraph (a)(4)(ii) would require the operator to implement additional 
or new corrective actions until sampling indicates miner exposures are 
at or below the PEL.
    Proposed Sec.  60.13(b) would require the mine operator to make a 
record of corrective actions required under proposed paragraph (a) of 
this section and the dates of those actions. These records would help 
the operator and MSHA identify whether existing controls are effective, 
or whether maintenance or additional control measures are needed.
7. Section 60.14--Respiratory Protection
    This proposed provision addresses the use of respiratory protection 
equipment. As noted earlier, the use of respiratory protection 
equipment, including powered air-purifying respirators (PAPRs), would 
not be permitted as a control to achieve compliance with the proposed 
PEL because engineering controls are more effective than respirators in 
protecting miners. However, temporary non-routine use of respirators 
would be allowed under limited circumstances.
    Proposed paragraph (a) would require the mine operator to provide 
respirators to miners as a temporary measure in accordance with 
proposed paragraph (c) of this section, when miners are working in 
concentrations of respirable crystalline silica above the PEL under 
specific, limited circumstances. Proposed paragraph (a)(1) would 
require the temporary use of respirators when miners' exposures exceed 
the proposed PEL during the development and implementation of 
engineering controls.
    Proposed paragraph (a)(2) would require the use of respirators for 
temporary, nonroutine work to prevent miners' exposures at levels above 
the proposed PEL. Examples include when a miner is mixing cement to 
build a stopping to separate a main intake from return airways or is 
engaged in an unplanned entry into an atmosphere with excessive 
respirable crystalline silica concentrations to perform a repair or 
investigation that must occur before feasible engineering or 
administrative controls can be implemented.
    The proposal is consistent with NIOSH's recommendation in the 1995 
Criteria Document (NIOSH 1995a) and is similar to the existing 
standards for MNM and coal mines. NIOSH (1995a) recommended the use of 
respirators as an interim measure when engineering controls and work 
practices are not effective in maintaining worker exposures for 
respirable crystalline silica at or below the proposed PEL.
    MSHA's existing MNM standards in parts 56 and 57 permit mine 
operators to allow miners to work for reasonable periods of time 
protected by appropriate respiratory protection in locations where 
concentrations of contaminants (including respirable crystalline 
silica) exceed permissible levels and where feasible engineering 
control measures have not been developed or where necessary by the 
nature of the work involved (e.g., occasional entry into hazardous 
atmospheres to perform maintenance or investigation). MSHA's existing 
standards for respirable coal mine dust require the mine operator to 
make respiratory protection equipment available while the operator 
evaluates and implements engineering control measures when a valid 
sample meets or exceeds the applicable standard during operator 
exposure monitoring. (30 CFR 70.208(e)(1); 30 CFR 71.206(h)(1); 30 CFR 
72.700-72.701; 30 CFR 90.207(c)(1)).
    Proposed paragraph (b) addresses situations where miners are not 
able to wear a respirator while working. Proposed paragraph (b) would 
require the mine operator, upon written notification by a PLHCP, to 
transfer an affected miner who is unable to wear a respirator to work 
in another area of the same mine, or to another occupation at the same 
mine, where respiratory protection is not required.
    The operator must ensure that the occupation and the area of the 
mine to which the miner is temporarily transferred do not expose the 
miner to respirable crystalline silica above the proposed PEL. Proposed 
paragraph (b)(1) would require the mine operator to continue to 
compensate the affected miner at no less than the regular rate of pay 
in the occupation held by that miner immediately prior to the transfer. 
Under proposed paragraph (b)(2), the miner may be transferred back to 
the initial work area or occupation when the temporary, non-routine use 
of respirators is no longer required.
    MSHA believes that this proposed provision is consistent with the 
mandate in the Mine Act to provide the maximum health protection for 
miners. Also, any effect on miners by this provision should be 
temporary since the concentration of respirable crystalline silica to 
which the miner would be exposed must be controlled through feasible 
engineering and administrative controls on a long-term basis.
    Proposed paragraph (c) includes the respiratory protection 
requirements that an operator must address when providing respirators 
to miners. Proposed paragraph (c)(1), like the existing standards in 
parts 56, 57, and 72, would require mine operators to provide 
respiratory protection equipment approved by NIOSH under 42 CFR part 
84. Whenever respirators are used by miners, proposed paragraph (c)(1) 
would require the mine operator to provide miners with NIOSH-approved 
atmosphere-supplying respirators or air-purifying respirators. 
Atmosphere-supplying respirators provide clean breathing air from a 
separate source (e.g., a self-contained air tank), whereas air-
purifying respirators use filters, cartridges, or canisters to remove 
contaminants from the air.
    In mines, commonly used types of air-purifying respirators include 
elastomeric respirators, filtering facepiece respirators (FFRs), and 
PAPRs. Elastomeric respirators, such as half-facepiece or full-
facepiece tight-fitting respirators, are made of synthetic or natural 
rubber material and can be cleaned, disinfected, stored, and repeatedly 
re-used. FFRs (i.e., dust masks), designed to cover areas of the 
wearer's face from the bridge of the nose to the chin, are disposable 
respirators composed of a weave of electrostatically charged synthetic 
filter fibers and an elastic head strap. PAPRs utilize a blower to move 
ambient air through an air-purifying filter that removes particulates 
and delivers clean air to the wearer. When air-purifying respirators 
(elastomeric respirators, FFRs, and PAPRs) are used, under proposed 
paragraph (c)(1), the mine operator would be required to select only 
high-efficiency NIOSH-certified particulate protection (i.e., 100 
series or HE filters) for respirable crystalline silica protection. A 
100 series and high efficiency filter means that the filter must 
demonstrate a minimum efficiency level of 99.97 percent (i.e., the 
filter is at least 99.97 percent efficient in removing particles of 0.3 
[micro]m aerodynamic mass median diameter).
    Under proposed paragraphs (c)(1)(i) through (c)(1)(ii), air-
purifying respirators would be required to be equipped with one of the 
following three particulate protection types: (1) particulate 
protection defined as a 100 series under 42 CFR part 84; or (2) 
particulate protection defined as High Efficiency ``HE'' under 42 CFR 
part 84. MSHA believes that air-purifying respirators with the highest 
efficiency NIOSH classifications for particulate protection are most 
suitable in protecting miners from occupational exposure to a 
carcinogen such as respirable crystalline silica.
    Proposed paragraph (c)(2) would require mine operators to follow 
the provisions, as applicable, of ASTM F3387-19, ``Standard Practice 
for

[[Page 44912]]

Respiratory Protection,'' when respiratory protection equipment is 
needed. Under the proposal, MSHA would require that the respiratory 
program would be in writing and would include the following minimally 
acceptable program elements: program administration; standard operating 
procedures; medical evaluations; respirator selection; training; fit 
testing; and maintenance, inspection, and storage. Beyond the minimally 
acceptable program elements, mine operators would be allowed to comply 
with the provisions of the 2019 ASTM standard that they deem 
applicable. The need for temporary non-routine use of respirators may 
vary, given the variability of mining processes, activities, and 
commodities that are mined. MSHA believes that flexibility afforded to 
mine operators under this paragraph may lead mine operators to focus 
more appropriately on those provisions that are relevant to their mine-
specific situations, allowing them to comply more efficiently and 
effectively.
    ASTM F3387-19 is a voluntary consensus standard published by ASTM 
International and was approved in 2019. MSHA proposes to incorporate by 
reference this consensus standard for two reasons.
    First, adopting this voluntary consensus standard is consistent 
with OMB Circular A-119, which encourages Federal agencies to 
``minimize reliance on government-unique standards where an existing 
standard would meet the Federal government's objective.'' ASTM F3387-19 
comprehensively addresses all aspects of establishing, implementing, 
and evaluating respiratory protection programs, and describes 
respiratory protection program elements which include: program 
administration; standard operating procedures; medical evaluation; 
respirator selection; training; fit testing; and respirator 
maintenance, inspection, and storage.
    Second, ASTM F3387-19 reflects current respirator technology and an 
up-to-date understanding of effective respiratory protection. For 
example, ASTM F3387-19 provides detailed information on respirator 
selection that are based on NIOSH's long-standing experience of testing 
and approving respirators for occupational use and OSHA's research and 
rulemaking on respiratory protection.
    More detailed discussion on ASTM F3387-19 is provided later in C. 
Updating MSHA Respiratory Protection Standards: Proposed Incorporation 
of ASTM F3387-19 by Reference.
8. Section 60.15--Medical Surveillance for Metal and Nonmetal Miners
    This proposed provision would require MNM mine operators to provide 
mandatory medical examinations to miners who begin in the mining 
industry after the effective date of the rule and offer voluntary 
periodic examinations to all other miners. These medical examinations 
would be provided by a PLHCP or specialist. The proposed requirements 
in this section are consistent with the Mine Act's mandate to provide 
maximum health protection for miners and provide MNM miners with 
information needed for early detection of respirable crystalline 
silica-related disease, resulting in prevention of disabling disease.
    The proposed requirements for MNM mine operators are also generally 
consistent with existing medical surveillance requirements for coal 
mine operators under 30 CFR 72.100 although the requirements differ in 
some respects. For example, the proposed provision specifies that 
medical examinations must be provided by a PLHCP or specialist, while 
the existing medical surveillance requirements for coal miners in Sec.  
72.100 coordinate with the surveillance system managed by NIOSH's Coal 
Workers' Health Surveillance Program (CWHSP) which works with coal mine 
operators under NIOSH regulations to provide medical surveillance. 
Proposed paragraph 60.15(a) would require that each MNM mine operator 
make medical examinations available to each MNM miner, at no cost to 
the miner, regardless of whether miners are reasonably expected to be 
exposed to any level of respirable crystalline silica. This proposed 
requirement is consistent with section 101(a)(7) of the Mine Act.
    Proposed paragraph 60.15(a) would also require medical examinations 
to be performed by a PLHCP or specialist. 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, spirometry, symptom assessment, 
and occupational history). A specialist, as defined in proposed Sec.  
60.2, refers to an American Board-certified specialist in pulmonary 
disease or occupational medicine. The Agency believes it is appropriate 
to allow not only a physician, but also any State-licensed health care 
professional, to perform the required medical examinations. This would 
provide operators with the flexibility needed to use professionals with 
necessary medical skills and minimize cost and compliance burdens.
    Proposed paragraph (a)(1) requires periodic examinations to be 
offered to all MNM miners at the frequencies specified in this section. 
Proposed paragraph (a)(2) specifies the types of medical examinations 
and is consistent with the existing requirements for coal mine 
operators under existing Sec.  72.100.
    Proposed paragraphs (a)(2)(i) and (ii) would require MNM operators 
to provide each miner with a medical examination that includes a review 
of the miner's medical and work history and a physical examination. The 
medical and work history would cover a miner's present and past work 
exposures, illnesses, and any symptoms indicating respirable 
crystalline silica-related diseases and compromised lung function. The 
medical and work history should focus not only on any history of 
tuberculosis, smoking, or exposure to respirable crystalline silica, 
but also on any diagnoses and symptoms of respiratory system 
dysfunction, including shortness of breath, coughing, or wheezing. The 
physical examination under (a)(2)(ii) would be focused on the 
respiratory tract. For the reasons stated above, these proposed 
requirements differ from the existing requirements for coal miners. The 
existing medical surveillance requirements for coal miners in 42 CFR 37 
specify standardized data collection elements for occupational 
histories and respiratory symptom assessment while proposed paragraphs 
(a)(2)(i) and (ii) specify a respiratory-focused history and physical 
examination by a clinician.
    Under proposed paragraph (a)(2)(iii), MSHA would require all 
medical examinations to include a chest X-ray. The required chest X-ray 
is a posterior/anterior view no less than 14 x 17 inches and no more 
than 16 x 17 inches at full inspiration, recorded on either film or 
digital radiography systems. The 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). This is a standard practice in pneumoconiosis surveillance 
programs and can potentially detect other respirable crystalline 
silica-related conditions, including lung cancer (Industrial Minerals 
Association-North America and Mine Safety and Health Administration, 
2008). The test would provide data that can be used to assess

[[Page 44913]]

for progression of silicosis and for other respirable crystalline 
silica-related conditions in MNM miners.
    MSHA preliminarily concludes that the number of B readers in the 
U.S. is adequate to classify chest X-rays conducted as part of the 
respirable crystalline silica rule (OSHA 2016a, 81 FR 16286, 16821). As 
discussed in OSHA's 2016 final silica rule, the number of B Readers is 
driven by supply and demand created by a free market, and many 
physicians choose to become B readers based on demands for such 
services (OSHA 2016a, 81 FR 16286, 16822). NIOSH is also able to train 
enough B readers to handle any potential increase in demand, providing 
several pathways for physicians to become B readers, such as free self-
study materials by mail or download and free B reader examinations 
(OSHA 2016a, 81 FR 16286, 16822). In addition, courses and examinations 
for certification are periodically offered for a fee through the 
American College of Radiology (OSHA 2016a, 81 FR 16286, 16822). Even if 
B readers are scarce in certain geographical locations, digital X-rays 
can be easily transmitted electronically to B readers located anywhere 
in the U.S. (OSHA 2016a, 81 FR 16286, 16822).
    Under proposed paragraph (a)(2)(iv), MSHA would require that 
pulmonary function testing (including spirometry) be part of every 
medical examination. The pulmonary function test must be administered 
by a spirometry technician with a current certificate from a NIOSH-
approved Spirometry Training Sponsorship. The purpose of spirometry is 
to measure baseline lung function followed by periodic tests to detect 
early impairment patterns, such as obstruction of air flow and 
restriction caused by underlying respiratory disease. This measurement 
can provide critical information for the primary, secondary, and 
tertiary prevention of workplace-related lung diseases, including 
respirable crystalline silica-related diseases. The use of spirometry 
is consistent with recommendations of the Dust Advisory Committee (U.S. 
DOL, 1996) and the NIOSH Criteria Document (1974). Indeed, NIOSH 
(2014a) notes that properly conducted spirometry should be part of a 
comprehensive workplace respiratory health program. Spirometry and 
chest X-rays are complementary examinations for detecting adverse 
health effects from respirable crystalline silica exposures.
    In order to maintain a certificate from a NIOSH-approved course, 
technicians must complete an initial training and then refresher 
training every five years (OSHA 2016a, 81 FR 16286, 16825). As 
discussed in OSHA's 2016 silica final rule, course sponsors are located 
throughout the U.S. and some sponsors will travel to a requested site 
to teach a course (OSHA 2016a, 81 FR 16286, 16825). One NIOSH-approved 
sponsor offers instructor-led live virtual initial training. Several 
live virtual and web-based refresher training options are also 
available. Because the required training is not too frequent and course 
sponsors appear to be widely available throughout the U.S., MSHA 
preliminarily concludes that the requirement that technicians maintain 
a certificate from a NIOSH-approved course will not impose substantial 
burdens on providers of spirometry testing.
    MSHA believes that the proposed medical examinations consisting of 
a medical and work history, a physical examination, a chest X-ray, and 
a spirometry test would help medical professionals identify early 
symptoms of respirable crystalline silica-related diseases, assist MNM 
miners in protecting their health, and lower the risk that MNM miners 
become materially impaired due to occupational exposure to respirable 
crystalline silica.
    Under proposed paragraph (b), MSHA would require MNM mine operators 
to provide every miner employed at MNM mines with the opportunity to 
have periodic medical examinations. Miner participation would be 
voluntary, as in the case of the examination requirement for coal 
miners in 30 CFR 72.100(b). Starting on the proposed effective date, 
mine operators must provide the opportunity for an examination to MNM 
miners no later than 5 years after the date of their last medical 
surveillance examination, and in addition, 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 for medical examinations. Periodic 
examinations would allow for comparisons with a miner's prior 
examination results, help detect respirable crystalline silica-related 
disease including silicosis, and address further progression of 
existing respiratory disease. If a miner has a positive chest X-ray 
(ILO category of 1/0+), it is important to intervene as promptly as 
possible for maximum health protection. In addition, an interval of 5 
years or less between each miner's periodic examinations can ensure 
detection of declines in a miner's lung function due to potential 
occupational exposure. MSHA believes that the proposed schedule, which 
is consistent with the periodic examination for coal miners required 
under Sec.  72.100(b), would provide MNM mine operators with 
flexibility in offering examinations to miners.
    Proposed paragraph (c) would require MNM mine operators to provide 
a mandatory initial medical examination for each MNM miner who is new 
to the mining industry. Consequently, if a miner had previous mining 
experience (such as working in a coal mine) and subsequently came to 
work in an MNM mine, MSHA would not require that the MNM mine operator 
provide the miner with an initial examination after the miner begins 
employment. Mandatory initial examinations would be conducted when 
miners are first hired in the mining industry and would provide an 
individual baseline of each miner's health status. This initial 
examination would assist in the early detection of respirable 
crystalline silica-related illnesses and conditions that may make the 
miner more susceptible to the toxic effects of respirable crystalline 
silica. The individual baseline would also be valuable in assessing any 
future health changes in each miner. Overall, the initial examination 
results would enable miners to respond appropriately to information 
about their health status.
    Proposed paragraph (c)(1) would require that the mandatory initial 
medical examination occur no later than 30 days after a miner new to 
the industry begins employment. Proposed paragraphs (c)(2) and (3) 
would require MNM mine operators to provide mandatory follow-up 
examinations to new miners who were eligible for an initial mandatory 
medical examination under proposed paragraph (c). MSHA believes follow-
up examinations are important for assessments of any changes in a new 
miner's health status and for future diagnoses.
    Under proposed paragraph (c)(2), MSHA would require that the mine 
operator provide a mandatory follow-up examination to the miner no 
later than 3 years after the miner's initial medical examination. Under 
proposed paragraph (c)(3), if a miner's 3-year follow-up examination 
shows evidence of a respirable crystalline silica-related disease or 
decreased lung function, the operator would be required to provide the 
miner with another mandatory follow-up examination with a specialist, 
as defined in proposed Sec.  60.2, within 2 years. This proposed 
requirement is intended to ensure that any miner whose follow-up 
medical examination shows evidence of silicosis or evidence of 
decreased lung function, as determined by the PLHCP or specialist, is 
seen by a professional with expertise in respiratory disease. This 
would ensure that miners would benefit from not only expert medical 
judgment but

[[Page 44914]]

also counseling regarding work practices and personal habits that could 
affect the miners' health. For the reasons stated above, this proposed 
requirement differs from the existing requirements for coal miners, 
which provides for follow up surveillance testing but does not include 
interaction with a PLHCP or specialist.
    Proposed paragraph (d) would require that the results of any 
medical examination performed under this section be kept confidential 
and provided only to the miner. The miner is also entitled to request 
that the medical examination results be provided to the miner's 
designated physician. Based on MSHA's experience with coal miners' 
medical surveillance, the Agency believes that confidentiality 
regarding medical conditions is essential and that it encourages miners 
to take advantage of the opportunity to detect early adverse health 
effects due to respirable crystalline silica. See 79 FR 24813, at 
24928, May 1, 2014.
    Under proposed paragraph (e), MNM mine operators would be required 
to obtain a written medical opinion from a PLHCP or specialist within 
30 days of the medical examination that includes 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. This would allow the mine operator to 
verify the examination has occurred and would provide the mine operator 
with information on miners' ability to use respirators. Proposed 
paragraph (f) would require the mine operator to maintain a record of 
the written medical opinions obtained from the PLHCP or specialist 
under proposed paragraph (e).
9. Section 60.16--Recordkeeping Requirements.
    Section 60.16 lists all the proposed recordkeeping requirements 
under this proposed part. To ensure that mine operators track actual or 
potential exposures, risks, and controls and keep miners, miners' 
representatives, and other stakeholders informed about them, the 
proposed part 60 establishes five recordkeeping requirements. 
Discussion of these requirements follow and are summarized in table 1 
to paragraph (a) in Sec.  60.16 of the rule text.
    First, this section would require that, once mine operators 
complete the sampling or semi-annual evaluations required under 
proposed Sec.  60.12, the operators retain the associated exposure 
monitoring records for at least 2 years. Examples of exposure 
monitoring records include the date of sampling or evaluation, names 
and occupations of miners who were sampled, description of sampling or 
evaluation method, and laboratory reports of sampling analysis. The 2-
year period would give mine operators sufficient exposure monitoring 
data to evaluate the effectiveness of their engineering and 
administrative controls over different mining and weather conditions.
    Second, mine operators would also be required to retain records of 
corrective actions made under proposed Sec.  60.13(b) for at least 2 
years from the date when each corrective action was taken. This 
proposed requirement is similar to the recordkeeping requirements 
related to other corrective-action requirements under parts 56 and 57 
(for MNM mines) and parts 70, 71, and 90 (for coal mines).
    Third, this proposed section would require mine operators to 
maintain any written determination records that they receive from a 
PLHCP or specialist. When a PLHCP or specialist certifies in writing 
that a miner cannot wear a respirator, including a PAPR, that miner 
must be temporarily transferred to a different work area or task where 
respiratory protection is not required (or needed). In such cases, mine 
operators would be required to retain the written determinations by a 
PLHCP or specialist for the duration of the miner's employment plus 6 
months.
    Fourth, under this section, MNM mine operators would be required to 
maintain written medical opinion records that they obtain from a PLHCP 
or specialist who conducts medical examinations of their miners under 
proposed Sec.  60.15. This proposed recordkeeping requirement would 
apply only to MNM mine operators. Under proposed Sec.  60.15, after the 
examination has taken place, the MNM mine operator would receive from 
the PLHCP or specialist a written medical opinion that contains the 
date of the medical examination, a statement that the examination has 
met the requirements under this proposed rule, and any recommended 
limitations on the miner's use of respirators. Upon receipt, the mine 
operator would retain the medical opinion for the duration of the 
miner's employment plus 6 months.
    Proposed paragraph (b) would ensure that all the listed records 
would be made available promptly upon request to miners, authorized 
representatives of miner(s), and authorized representatives of the 
Secretary of Labor.
10. Section 60.17--Severability
    The severability clause under proposed 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. Mfrrs. 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.

B. Conforming Amendments

    The proposed rule would require conforming amendments in 30 CFR 
parts 56, 57, 70, 71, 72, 75, and 90 based on the proposed new part 60.

[[Page 44915]]

1. Part 56--Safety and Health Standards--Surface Metal and Nonmetal 
Mines
a. Section 56.5001--Exposure Limits for Airborne Contaminants
    For respirable crystalline silica, proposed part 60 would establish 
exposure limits and other related requirements for all mines. Existing 
paragraph (a) of Sec.  56.5001 governs exposure limits for airborne 
contaminants, except asbestos, for surface MNM mines. MSHA is proposing 
to amend paragraph (a) of Sec.  56.5001 to add respirable crystalline 
silica as an exception. The amended paragraph (a) of Sec.  56.5001 
would govern exposure limits for airborne contaminants other than 
respirable crystalline silica and asbestos for surface MNM mines.
2. Part 57--Safety and Health Standards--Underground Metal and Nonmetal 
Mines
a. Section 57.5001--Exposure Limits for Airborne Contaminants
    Existing paragraph (a) of Sec.  57.5001 governs exposure limits for 
airborne contaminants, except asbestos, for underground MNM mines. 
Similar to the proposed changes discussed above for Sec.  56.5001, MSHA 
is proposing to amend paragraph (a) of Sec.  57.5001 to add respirable 
crystalline silica as an exception. The amended paragraph (a) of Sec.  
57.5001 would govern exposure limits for airborne contaminants other 
than respirable crystalline silica and asbestos for underground MNM 
mines.
3. Part 70--Mandatory Health Standards--Underground Coal Mines
a. Section 70.2--Definitions.
    MSHA proposes to remove the Quartz definition in Sec.  70.2. With 
the adoption of an independent respirable crystalline silica standard 
in proposed part 60, the Agency is proposing to remove RCMD when quartz 
is present in Sec.  70.101 and the term quartz would no longer appear 
in part 70.
b. Section 70.101--Respirable Dust Standard When Quartz Is Present
    MSHA is proposing to remove the entire section and reserve the 
section number. The RCMD when quartz is present in Sec.  70.101 would 
no longer be needed because MSHA is proposing an independent respirable 
crystalline silica standard in proposed part 60.
    MSHA's proposed independent standard for respirable crystalline 
silica would result in miners' exposure to respirable crystalline 
silica no longer being controlled indirectly by reducing respirable 
dust. NIOSH, the Secretary of Labor's Advisory Committee on the 
Elimination of Pneumoconiosis Among Coal Mine Workers (Dust Advisory 
Committee), and the Department of Labor's Inspector General \35\ have 
each recommended the adoption of an independent standard for respirable 
quartz exposure in coal mines. NIOSH evaluated the effectiveness of the 
existing standard and found the approach of controlling miners' 
exposures to respirable crystalline silica indirectly through the 
control of respirable dust did not protect miners from excessive 
exposure to respirable quartz in all cases (Joy GJ 2012). The study 
concluded that a separate respirable quartz standard, as described by 
the 1995 NIOSH Criteria Document, could reduce miners' risk of 
overexposures to respirable quartz and, by extension, their risk of 
developing silicosis. The adoption of a separate standard would hold 
operators accountable, at risk of a citation and monetary penalty, when 
overexposures of the respirable crystalline silica PEL occur and 
enhance its sampling program to increase the frequency of operator 
sampling.
---------------------------------------------------------------------------

    \35\ Office of Inspector General Audit 05-21-001-06-001, MSHA 
Needs to Improve Efforts to Protect Coal Miners from Respirable 
Crystalline Silica (Nov. 12, 2020). The Inspector General 
recommended that MSHA:
    1. Adopt a lower legal exposure limit for silica in coal mines 
based on recent scientific evidence.
    2. Establish a separate standard for silica that allows MSHA to 
issue a citation and monetary penalty when violations of its silica 
exposure limit occur.
    3. Enhance its sampling program to increase the frequency of 
inspector samples where needed (e.g., by implementing a risk-based 
approach).
---------------------------------------------------------------------------

c. Section 70.205--Approved Sampling Devices; Operation; Air Flowrate
    MSHA is proposing to amend paragraph (c) of Sec.  70.205 to remove 
the reference to the reduced RCMD standard. References to the RCMD 
exposure limit specified in Sec.  70.100 would replace references to 
the applicable standard. The rest of the section would remain 
unchanged.
d. Section 70.206--Bimonthly Sampling; Mechanized Mining Units
    MSHA is proposing to amend subpart C, Sampling Procedures, by 
removing Sec.  70.206 and reserving 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 needed.
e. Section 70.207--Bimonthly Sampling; Designated Areas
    MSHA is proposing to amend subpart C, Sampling Procedures, by 
removing Sec.  70.207 and reserving 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 needed.
f. Section 70.208--Quarterly Sampling; Mechanized Mining Units
    MSHA is proposing to amend Sec.  70.208 to remove references to a 
reduced RCMD standard. Paragraph (c) in Sec.  70.208 would be removed 
and the paragraph designation reserved. References to the respirable 
dust standard specified in Sec.  70.100 would replace references to the 
applicable standard throughout the section.
    A new table 1 to Sec.  70.208 would be added. The 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. This table contains the 
remaining ECV after the removal of the reduced standard in Sec.  
70.101. It was generated from data contained in existing Tables 70-1 
and 70-2 to 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 to Sec.  70.208.
g. Section 70.209--Quarterly Sampling; Designated Areas
    Similar to the proposed changes discussed above for Sec.  70.208, 
MSHA is proposing to amend Sec.  70.209 to remove references to a 
reduced RCMD standard. Paragraph (b) in Sec.  70.209 would be removed 
and the paragraph designation reserved. References to the RCMD exposure 
limit specified in Sec.  70.100 would replace references to the 
applicable standard.
    A new table 1 to Sec.  70.209 would be added. The 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. It was generated from 
data contained in existing Tables 70-1 and 70-2 to 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 to Sec.  70.209.

[[Page 44916]]

h. Subpart C--Table 70-1 and Table 70-2
    MSHA is proposing to amend subpart C, Sampling Procedures, by 
removing Table 70-1 Excessive Concentration Values (ECV) Based on 
Single, Full-Shift CMDPSU/CPDM Concentration Measurements and Table 70-
2 Excessive Concentration Values (ECV) Based on the Average of 5 or 15 
Full-Shift CMDPSU/CPDM Concentration Measurements because Sec.  70.101 
would be removed. These tables would be replaced with new tables added 
to Sec. Sec.  70.208 and 70.209.
4. Part 71--Mandatory Health Standards--Surface Coal Mines and Surface 
Work Areas of Underground Coal Mines
a. Section 71.2--Definitions
    As discussed in the analysis of conforming amendments for Sec.  
70.2, MSHA also proposes to remove the Quartz definition in Sec.  71.2 
because the Agency is proposing to remove the respirable dust standard 
when quartz is present in Sec.  71.101. The term quartz would no longer 
appear in part 71.
b. Section 71.101--Respirable Dust Standard When Quartz Is Present
    MSHA is proposing to remove the entire section of Sec.  71.101 and 
reserve the section number. Similar to the proposed conforming 
amendments for Sec.  70.101, the respirable coal mine dust standard 
when quartz is present in Sec.  71.101 would no longer be needed 
because MSHA is proposing an independent respirable crystalline silica 
standard in part 60.
    MSHA's proposal to adopt an independent standard for respirable 
crystalline silica would replace the existing method of indirectly 
controlling miners' exposure to silica by reducing respirable coal 
dust. As stated previously, NIOSH evaluated the effectiveness of the 
existing standard and found the existing approach of controlling 
miners' exposures to respirable crystalline silica indirectly through 
the control of respirable dust did not protect miners from excessive 
exposure to respirable crystalline silica in all cases. The study 
concluded that a separate respirable crystalline silica standard, as 
described by the 1995 NIOSH Criteria Document, could reduce miners' 
risk of overexposures to respirable crystalline silica and, by 
extension, their risk of developing silicosis. The adoption of a 
separate standard would allow MSHA to issue a citation and monetary 
penalty when overexposures of the respirable crystalline silica PEL 
occur and enhance its sampling program to increase the frequency of 
inspector sampling.
c. Section 71.205--Approved Sampling Devices; Operation; Air Flowrate
    MSHA is proposing to amend paragraph (c) of Sec.  71.205 to remove 
the reference to the reduced RCMD standard. References to the 
respirable dust standard specified in Sec.  71.100 would replace the 
reference to the applicable standard. The rest of the section would 
remain unchanged.
d. Section 71.206--Quarterly Sampling; Designated Work Positions
    Similar to the analysis of conforming amendments for Sec. Sec.  
70.208 and 70.209, MSHA is proposing to amend Sec.  71.206 to remove 
references to the reduced RCMD standard. Paragraph (b) in Sec.  71.206 
would be removed and the paragraph designation reserved. Other 
conforming changes for Sec.  71.206 would remove references to the 
applicable standard and replace them, where needed, with references to 
the respirable dust standard specified in Sec.  71.100 throughout the 
section.
    MSHA is also proposing to amend 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 would be removed. They would be replaced with 
a new table added to Sec.  71.206.
    Existing paragraph (m) would be modified by removing 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 would be removed, as discussed above, which removes the 
reference to the reduced standard and replaces it with a reference to 
the respirable dust standard specified in Sec.  71.100.
    A new table 1 to Sec.  71.206 would be added. 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 to Sec.  71.206.
e. Section 71.300--Respirable Dust Control Plan; Filing Requirements
    MSHA is proposing to amend Sec.  71.300 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
71.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
f. Section 71.301--Respirable Dust Control Plan; Approval by District 
Manager and Posting
    MSHA is proposing to amend Sec.  71.301 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
71.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
5. Part 72--Health Standards for Coal Mines
a. Section 72.800--Single, Full-Shift Measurement of Respirable Coal 
Mine Dust
    MSHA is proposing to amend Sec.  72.800 in subpart E, 
Miscellaneous, and remove references to the reduced RCMD standard. The 
proposed section would also replace references to Tables 70-1, 71-1, 
and 90-1 with references to tables in Sec. Sec.  70.208, 70.209, 
71.206, and 90.207.
6. Part 75--Mandatory Safety Standards--Underground Coal Mines
a. Section 75.350(b)(3)(i) and (ii)--Belt Air Course Ventilation
    MSHA is proposing to update 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)(A) would be removed because its provision has 
not been in effect since August 1, 2016. Paragraph (b)(3)(i)(B) would 
be removed because the proposed revised language in paragraph (b)(3)(i) 
would be simplified by stating that ``[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\.'' This would 
ensure that miners would be protected from coal dust overexposures, 
including respirable crystalline silica overexposures, by maintaining 
the RCMD PEL in the belt air course at 50 [micro]g/m\3\. Therefore, 
paragraph (b)(3)(i)(B) which sets the PEL for belt course air at 0.5 
mg/m\3\ would be redundant.
    Existing paragraph (b)(3)(ii) would be removed since it refers to a 
reduced RCMD standard under Sec.  70.101 that would also be removed. 
Existing

[[Page 44917]]

paragraph (b)(3)(iii) would be redesignated to (b)(3)(ii).
7. Part 90--Mandatory Health Standards--Coal Miners Who Have Evidence 
of the Development of Pneumoconiosis
a. Section 90.2--Definitions
    Similar to the proposed changes for Sec. Sec.  70.2 and 71.2, MSHA 
proposes to remove the Quartz definition in Sec.  90.2 because the 
Agency proposes to remove the respirable dust standard when quartz is 
present in Sec.  90.101. The term quartz would no longer appear in part 
90.
    In addition, MSHA is revising the definition of Part 90 miner to 
remove references to the reduced RCMD standard. The respirable dust 
standard specified in Sec.  90.100 would replace the reference to the 
applicable standard. The definition of Part 90 miner would also be 
updated to define Part 90 miners as miners who have exercised 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 respirable 
dust standard specified in Sec.  90.100.
b. Section 90.3--Part 90 Option; Notice of Eligibility; Exercise of 
Option
    MSHA is proposing to revise paragraph (a) in Sec.  90.3 to require 
that miners diagnosed with pneumoconiosis must be afforded the option 
to work in an area of a mine where the average concentration of 
respirable dust is continuously maintained below the respirable dust 
standard specified in Sec.  90.100 rather than at or below the 
applicable standard. The rest of the section would remain unchanged.
c. Section 90.101--Respirable Dust Standard When Quartz Is Present
    MSHA is proposing to remove the entire section and reserve the 
section number. The respirable coal mine dust standard when quartz is 
present in Sec.  90.101 would no longer be needed because MSHA is 
proposing an independent respirable crystalline silica standard in 
proposed part 60.
    MSHA's proposal to adopt an independent standard for respirable 
crystalline silica would replace the existing method of indirectly 
controlling miners' exposure to respirable crystalline silica by 
reducing respirable coal dust. As stated previously, NIOSH evaluated 
the effectiveness of the existing standard and found the existing 
approach of controlling miners' exposures to respirable crystalline 
silica indirectly through the control of respirable dust did not 
protect miners from excessive exposure to respirable quartz in all 
cases. The study concluded that a separate respirable quartz standard, 
as described by the 1995 NIOSH Criteria Document, could reduce miners' 
risk of overexposures to respirable quartz and, by extension, their 
risk of developing silicosis.
d. Section 90.102--Transfer; Notice
    MSHA is proposing to amend Sec.  90.102 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
90.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
e. Section 90.104--Waiver of Rights; Re-Exercise of Option
    MSHA is proposing to amend Sec.  90.104 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
90.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
f. Section 90.205--Approved Sampling Devices; Operation; Air Flowrate
    MSHA is proposing to amend Sec.  90.205 to remove the reference to 
the reduced RCMD standard. The respirable dust standard specified in 
Sec.  90.100 would replace the reference to the applicable standard. 
The rest of the section would remain unchanged.
g. Section 90.206--Exercise of Option or Transfer Sampling
    MSHA is proposing to amend Sec.  90.206 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
90.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
h. Section 90.207--Quarterly Sampling
    Similar to the analysis of conforming amendments for Sec. Sec.  
70.208, 70.209, and 71.206, MSHA is proposing to amend Sec.  90.207 to 
remove references to the reduced RCMD standard. Paragraph (b) in Sec.  
90.207 would be removed and the paragraph designation reserved. The 
respirable dust standard specified in Sec.  90.100 would replace 
references to the applicable standard. The rest of the section would 
remain unchanged.
    MSHA is proposing to amend paragraph (g) by removing the 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 would be removed.
    A new table 1 to Sec.  90.207 would be added to replace the tables 
removed in paragraph (g). The 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. It was generated from data contained in existing Tables 90-1 
and 90-2 to subpart C of part 90. Conforming changes are made to 
paragraphs (c) and (d)(1) and (2) to update the name of the table to 
table 1 to Sec.  90.207.
i. Section 90.300--Respirable Dust Control Plan; Filing Requirements
    MSHA is proposing to amend Sec.  90.300 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
90.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.
j. Section 90.301--Respirable Dust Control Plan; Approval by District 
Manager; Copy to Part 90 Miner
    MSHA is proposing to amend Sec.  90.301 to remove references to the 
reduced RCMD standard. The respirable dust standard specified in Sec.  
90.100 would replace references to the applicable standard. The rest of 
the section would remain unchanged.

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

    MSHA is proposing to update the Agency's existing respiratory 
protection standard to help safeguard the life and health of all miners 
exposed to respirable airborne hazards at MNM and coal mines. The 
proposed rule would incorporate by reference ASTM F3387-19, ``Standard 
Practice for Respiratory Protection'' (ASTM F3387-19), as applicable, 
in existing Sec. Sec.  56.5005, 57.5005, and 72.710, as well as in 
proposed Sec.  60.14(c)(2). 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 based on the most recent consensus standards recognized by 
experts in government and professional associations on the selection, 
use, and maintenance for

[[Page 44918]]

respiratory equipment. The ASTM Standard would replace American 
National Standards Institute's ANSI Z88.2-1969, ``Practices for 
Respiratory Protection'' (ANSI Z88.2-1969), which is 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 A119--that agencies use 
voluntary consensus standards in their regulatory activities unless 
doing so would be legally impermissible or impractical. This standard 
proposed for incorporation would also improve 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 50121, 50122, Aug. 24, 2006). 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.
    ASTM F3387-19 is based on the most recent consensus standards 
recognized by experts in government and professional associations on 
the selection, use, and maintenance for respiratory protection 
equipment. The standard contains detailed guidance and provisions on 
respirator selection that are based on NIOSH's long-standing experience 
of 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 elements in the areas of program 
administration, standard operating procedures, medical evaluation, 
respirator selection, training, 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 would provide 
mine operators with information and guidance on the proper selection, 
use, and maintenance of respirators, which would protect the health and 
safety of miners.
    Under this proposed rule, MSHA would require that operators 
establish a respiratory protection program in writing, that includes 
minimally acceptable program elements: program administration; standard 
operating procedures; medical evaluations; respirator selection; 
training; fit testing; and maintenance, inspection, and storage.
    Beyond the minimally acceptable program elements, MSHA proposes to 
provide mine operators with flexibility to select the provisions in 
ASTM F3387-19 that are applicable to the conditions of their mines and 
respirator use by their miners. In MSHA's experience, the need for and 
actual use of respirators varies among mines for different reasons, 
including the type of commodity mined or processed and the mining 
method and controls used. At some mines, miners may not use or may only 
rarely use respirators. At other mines, miners may use respirators more 
frequently. Recognizing these differences, MSHA would allow mine 
operators to comply with the provisions in ASTM F3387-19 that they deem 
are relevant and appropriate for their mining operations and 
conditions.
    MSHA has observed that many operators, in particular larger mine 
operators, have already implemented in their respiratory programs many 
OSHA requirements, which are substantially similar to many requirements 
in ASTM F3387-19. Indeed, ASTM F3387-19 refers to OSHA's regulations on 
respiratory protection programs, APFs and MUCs, and fit testing. MSHA 
believes that the mining industry is already 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, or mines that use respirators 
intermittently, may need to revise their respiratory practices in 
accordance with the requirements, as applicable, in ASTM F3387-19.
1. Respiratory Program Elements
    Under the proposed rule, MSHA would require that the respiratory 
protection program be in writing and that it include the following 
minimally acceptable program elements: program administration; standard 
operating procedures; medical evaluations; respirator selection; 
training; fit testing; and maintenance, inspection, and storage.
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 could be 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 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 program administrator's responsibilities, specifying that 
they should include: measuring, estimating, or reviewing

[[Page 44919]]

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)
    SOPs are written policies and procedures available for all wearers 
of respirators to read and are established by the employer. ASTM F3387-
19 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 respirator selection for both routine and emergency use 
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 all 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 consideration 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 essential information regarding respirator selection such as 
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 in the 
application and use of the respirators and must understand the site's 
work practices, respirator program, and applicable regulations. 
Employees who receive training 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, 
ASTM F3387-19 also provides that the minimum training for each 
respirator wearer includes: 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 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 would 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 
adequately fits 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 
appropriate methods to be used. ASTM F3387-19 also provides information 
on conducting quantitative and qualitative fits test to determine how 
well a tight-fitting respirator fits a wearer. 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 
(currently at least once every 12 months or repeated 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

[[Page 44920]]

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 are 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 (i.e., physical, biological, chemical, vibration, shock, 
temperature extremes, moisture, etc.). It also provides that 
respirators are stored to prevent 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
    Existing Sec.  56.5005 provides that whenever respiratory 
protective equipment is used, a program for selection, maintenance, 
training, fitting, supervision, cleaning, and use shall meet the 
requirements of paragraph (b). Paragraph (b) requires that mine 
operators implement a respirator program consistent with the 
requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph 
(b) to remove the incorporation by reference to ANSI Z88.2-1969 and 
incorporate by reference ASTM F3387-19.
    MSHA is proposing to revise paragraph (b) to state that approved 
respirators must be selected, fitted, cleaned, used, and maintained in 
accordance with the requirements of ASTM F3387-19 ``as applicable.'' 
Under the proposal, MSHA would require that the respiratory program be 
in writing and that it include the following minimally acceptable 
program elements: program administration; standard operating 
procedures; medical evaluations; respirator selection; training; fit 
testing; and maintenance, inspection, and storage.
    Also, MSHA is proposing to change 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 IDLH as 
``any atmosphere that poses an immediate hazard to life or immediate 
irreversible debilitating effects on health'' (ASTM International 
2019).
b. Part 57--Safety and Health Standards--Underground Metal and Nonmetal 
Mines--Section 57.5005--Control of Exposure to Airborne Contaminants
    Existing Sec.  57.5005 provides that whenever respiratory 
protective equipment is used, a program for selection, maintenance, 
training, fitting, supervision, cleaning, and use shall meet the 
requirements of paragraph (b). Paragraph (b) requires that mine 
operators implement a respirator program consistent with the 
requirements of ANSI Z88.2-1969. MSHA is proposing to revise paragraph 
(b) to remove the incorporation by reference to ANSI Z88.2-1969 and 
incorporate by reference ASTM F3387-19.
    MSHA is proposing to revise paragraph (b) to state that approved 
respirators must be selected, fitted, cleaned, used, and maintained in 
accordance with the requirements of ASTM F3387-19 ``as applicable.'' 
Under the proposal, MSHA would require that the respiratory program be 
in writing and that it include the following minimally acceptable 
program elements: program administration; standard operating 
procedures; medical evaluations; respirator selection; training; fit 
testing; and maintenance, inspection, and storage.
    Also, MSHA is proposing to change 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).
c. Part 72--Health Standards for Coal Mines--Section 72.710--Selection, 
Fit, Use, and Maintenance of Approved Respirators
    Existing Sec.  72.710 requires approved respirators be selected, 
fitted, used, and maintained in accordance with the provisions of ANSI 
Z88.2-1969, which was incorporated by reference into coal standards in 
1995 (60 FR 30398, June 8, 1995). MSHA is proposing to revise Sec.  
72.710 by removing the requirement in the first sentence that coal mine 
operators must ensure that the maximum amount of respiratory protection 
is made available to miners when respirators are used. MSHA believes 
that the use of approved respirators and the proposed incorporation by 
reference of ASTM F3387-19 would ensure that coal miners' health is 
protected. Under the proposal, MSHA would require that the respiratory 
program be in writing and that it include the following minimally 
acceptable program elements: program administration; standard operating 
procedures; medical evaluations; respirator selection; training; fit 
testing; and maintenance, inspection, and storage.

VIII. Technological Feasibility

    This technological feasibility analysis considers whether currently 
available technologies, used alone or in combination with each other, 
can be used by operators to comply with the proposed standard.
    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).

[[Page 44921]]

    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 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)).
    This section presents technological feasibility findings that 
guided MSHA's selection of the proposed PEL. MSHA's technological 
feasibility findings are organized into two main sections covering: (1) 
the technological feasibility of proposed part 60; and (2) the 
technological feasibility of the proposed revision to existing 
respiratory protection standards. Based on the analyses presented in 
the two sections, MSHA preliminarily concludes that the Agency's 
proposal 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 would be sufficient to 
comply with the proposed rule.
    First, MSHA has preliminarily determined that proposed part 60 is 
technologically feasible. Many mine operators already maintain 
respirable crystalline silica exposures at or below the proposed PEL of 
50 [mu]g/m\3\, and at mines where there are elevated exposures, 
operators would be able to reduce exposures to at or below the proposed 
PEL by properly maintaining existing engineering controls and/or by 
implementing new engineering and administrative controls that are 
currently available. In addition, mines would be able to satisfy the 
exposure monitoring requirements of proposed part 60 with existing, 
validated, and widely used sampling technologies and analytical 
methods.
    Second, the analysis shows that the proposed update to MSHA's 
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'' (ASTM F3387-19), which 
MSHA is proposing to incorporate by reference.

A. Technological Feasibility of Sampling and Analytical Methods

1. Sampling Methods
    MSHA's proposed rule would require 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 ([mu]m) aerodynamic diameter median cut-point 
(i.e., 4 [mu]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 convention is widely considered biologically relevant 
for respirable particulates and provides appropriate criteria for 
equipment used to sample respirable crystalline silica. MSHA's current 
sampling method for MNM mines meets the ISO criteria by using a 10 mm 
Dorr-Oliver cyclone and a sampling pump operated at a flow rate of 1.7 
liter per minute (L/min), and MNM mine operators also already use this 
type of sampler for MNM sampling under existing standards. MSHA's 
current sampling method for RCMD, including respirable crystalline 
silica, uses a 10 mm Dorr-Oliver cyclone but operated at 2.0 L/min to 
approximate the British Mining Research Establishment (MRE) sampling 
criteria, and thus does not meet the ISO criteria. Although, the 
existing sampling pumps can be adjusted to operate at a flow rate of 
1.7 L/min flow rate to meet the ISO criteria. To comply with this 
proposed requirement, coal mine operators that currently use coal mine 
dust personal sampler units (CMDPSU) would need to adjust their 
samplers to the flow rate specified by the manufacturer for complying 
with the ISO.
    There are a variety of size-selective samplers on the market that 
meet the ISO respirable-particle-size selection criteria. Examples 
include Dorr-Oliver cyclone currently used by MSHA and OSHA, operated 
at 1.7 L/min; SKC aluminum cyclone (2.5 L/min); HD cyclone (2.2 L/min); 
SKC GS-3 multi-inlet cyclone (2.75 L/min); and BGI GK 2.69 (4.2 L/min). 
Each cyclone has different operating specifications and performance 
criteria, but they all are compliant with the ISO criteria for 
respirable dust with an acceptable level of measurement bias. 
Manufacturers of size-selective samplers specify the flow rates that 
are necessary to conform to the particle size collection criteria of 
the ISO standard. Samplers used in both MNM and coal mines can be used 
to perform the proposed sampling, and because other commercially 
available (already on the market) samplers conform to the ISO standard, 
MSHA preliminarily finds that sampling in accordance with the ISO 
standard is technologically feasible.
2. Analytical Methods and Feasibility of Measuring Below the Proposed 
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 proposes a PEL for respirable crystalline silica of 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 proposed 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 (analysis by infrared spectroscopy, 
FTIR or IR) for coal mines.\36\ The MSHA P-2 and P-7 methods, reliably 
analyze compliance samples collected by MSHA inspectors, including 15 
years of MNM compliance samples and 5 years of coal industry compliance 
samples MSHA used for the exposure profile portion of this 
technological feasibility analysis. These methods are capable of 
measuring respirable crystalline silica exposures at levels below the 
proposed PEL and action level.
---------------------------------------------------------------------------

    \36\ Other similar XRD methods include NIOSH-7500 and OSHA ID-
142. XRD methods are able to distinguish between the different 
polymorphs--quartz, cristobalite and tridymite. Other IR methods 
include NIOSH 7602 and 7603. IR methods are efficient, but they are 
more prone to interferences and should only be used for samples with 
a well-characterized matrix (e.g., coal dust).
---------------------------------------------------------------------------

    For an analytical method to have acceptable sensitivity for 
determining

[[Page 44922]]

exposures at the proposed 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 would be collected in an air sample where the 
concentration of analyte is equivalent to the proposed 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 VIII-1 
presents minimum quantifiable quartz concentrations, for various 
cyclones and established analytical methods.
[GRAPHIC] [TIFF OMITTED] TP13JY23.025

    Based on this discussion, MSHA preliminarily finds that current 
analytical methods are sufficiently sensitive to meet the proposed PEL 
and action level.
3. Laboratory Capacity
    MSHA's proposed standard would require that mines conduct baseline 
sampling, periodic sampling, corrective actions sampling, and post-
evaluation sampling with analyses conducted by 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 23 accredited commercial laboratories nationwide that, as of 
April 2022, perform respirable crystalline silica analysis using an 
MSHA, NIOSH or OSHA method.
    MSHA interviewed a sample of three laboratories (one small-capacity 
laboratory,\37\ one medium-capacity laboratory,\38\ and one large-
capacity laboratory) \39\ to estimate their sample-processing capacity. 
Insights from these interviews suggest that laboratories have the 
ability to provide surge capacity as the proposed rule is phased in. 
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 232,680 samples for MNM 
mines and 12,250 samples for coal mines could be processed in the 
phase-in 6-month period. Over the first 12 months after the standard 
goes into effect, analysis would be available for 465,360 samples for 
MNM mines and 24,500 samples for coal mines.
---------------------------------------------------------------------------

    \37\ 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.
    \38\ 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.
    \39\ 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).
---------------------------------------------------------------------------

    Based on exposure profiles for the MNM and coal mining industries 
and MSHA's experience and knowledge of the mining industry, MSHA 
estimates that within this first 12-month period, mines would seek 
analysis for a total of 172,907 respirable crystalline silica samples 
(including 58,126 samples for MNM mines and 12,373 samples for coal 
mines associated with the 6-month baseline sampling period). In the 
subsequent 12-month period, mines would require analysis for 102,409 
samples (includes process/control measure evaluation samples and 
periodic samples associated with the

[[Page 44923]]

proposed action level), a number that will decline over years 1 through 
6 as the mine operators reduce some miner exposures below the proposed 
action level.\40\ Comparing these figures with the surge capacity 
estimates previously noted above, MSHA believes that there would be 
sufficient processing capacity to meet the sampling analysis schedule 
envisioned in the proposed rule.
---------------------------------------------------------------------------

    \40\ MSHA anticipates that in the initial six-month baseline 
period mine operators will collect 70,498 baseline samples, of which 
12,373 will be coal mine samples. In the 12 months beginning after 
the initial baseline period, mines will collect 88,281 samples for 
miners who are exposed at or above the proposed action level (25 
[micro]g/m\3\), but at or below the proposed PEL, plus 14,128 
samples to evaluate corrective action and process change (i.e., 
processes which must be analyzed to determine whether newly 
implemented dust control measures are successful and processes newly 
identified during periodic walk-through evaluations), for a total of 
102,409 samples per year (including 25,152 coal mine samples). 
Estimates are as of December 2022.
---------------------------------------------------------------------------

a. Baseline Sampling
    MSHA's proposal would require baseline sampling for each miner who 
is or may reasonably be expected to be exposed to respirable 
crystalline silica within 180 days (6 months) of the standard's 
effective date.\41\ This would require an initial increase in 
analytical laboratory capacity of approximately 70,498 sample analyses 
over 6 months. MSHA expects that with months of lead time during the 
proposed rule and final rule stages of the rulemaking, laboratories 
would anticipate the initial baseline period increase in demand and 
would respond by increasing their analytical capacity. For example, 
laboratories could acquire additional instrumentation, train additional 
analysts, or add a second or third operating shift. This is 
particularly likely given that demand would be based on a regulatory 
requirement and during the rulemaking process MSHA would conduct 
outreach to make all relevant stakeholders aware of the rule's 
provisions. MSHA is specifically soliciting comments on the 
technological feasibility of laboratory capability to conduct baseline 
sampling. At this point in the rulemaking, MSHA believes that the 
proposed rule is technologically feasible for laboratories to conduct 
baseline sampling analyses.
---------------------------------------------------------------------------

    \41\ 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.
---------------------------------------------------------------------------

b. Periodic, Corrective Actions, and Post-Evaluation Sampling
    Under proposed Sec.  60.12 (b)-(e), three conditions would require 
mine operators to conduct additional sampling after the initial 6-month 
baseline period. First, when the most recent sampling indicates that 
miner exposures are at or above the proposed action level (25 [micro]g/
m\3\) but at or below the proposed PEL (50 [micro]g/m\3\), the mine 
operator would be 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 would be required 
to sample after corrective actions are taken to reduce overexposures, 
until sampling results indicate miner exposures are at or below the 
PEL. Third, if the mine operator determines, as a result of the semi-
annual evaluation, that miners may be exposed to respirable crystalline 
silica at or above the action level, the mine operator would be 
required to 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.
    MSHA estimates that the total number of analyses (489,860) that 
laboratories will be able to perform per year is more than 2.5 times 
the total estimated number of samples for which mines will seek 
analyses in the first year (172,907). Based on the estimated surplus 
analyses available beyond baseline sampling (419,362), MSHA 
preliminarily finds that periodic, corrective actions, and post-
evaluation sampling would also be technologically feasible both in the 
first year and in subsequent years.\42\
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    \42\ 489,860 total annual laboratory analyses divided by 172,907 
mine samples to be analyzed, equals 2.83 percent surplus sample 
analyses. 489,860 total analyses-70,498 baseline analyses = a 
surplus of 419,362 analyses available for the 102,409 periodic, 
corrective actions, and process change sampling.
---------------------------------------------------------------------------

B. Technological Feasibility of the Proposed PEL

1. Methodology
    The technological feasibility analysis for the proposed 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 to be analyzed for respirable 
crystalline silica by MSHA's analytical laboratory.\43\
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    \43\ 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 National Institute for Occupational Safety and Health 
(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).\44\ 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.
---------------------------------------------------------------------------

    \44\ 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, 
including control of respirable dust (including respirable crystalline 
silica) exposure. MSHA offers informational programs, training, 
publications, onsite evaluations, and investigations that document 
conditions in mines and help mines operate in a safe and healthy 
manner.\45\
---------------------------------------------------------------------------

    \45\ 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).
---------------------------------------------------------------------------

    MSHA also consulted other published reports, scientific journal 
articles, and information from equipment manufacturers and mining 
industry suppliers.\46\
---------------------------------------------------------------------------

    \46\ 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.
---------------------------------------------------------------------------

2. The Technological Feasibility Analysis Process
a. 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

[[Page 44924]]

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 those conditions, and determined 
whether mines would need additional control methods, and if so, whether 
those methods were available.
b. Exposure Profiles
    MSHA classified all valid respirable crystalline silica samples in 
the Agency's MSIS data,\47\ grouping the data by commodity category, 
followed by activity group.\48\ 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 [mu]g/m\3\, >25 [mu]g/m\3\ to <=50 [mu]g/m\3\, >50 [mu]g/m\3\ to 
<=100 [mu]g/m\3\ (equivalent to 85.7 [mu]g/m\3\ in coal mines for a 
sample calculated as an 8-hour TWA), >100 [mu]g/m\3\ to <=250 [mu]g/
m\3\, >250 [mu]g/m\3\ to <=500 [mu]g/m\3\, and >500 [mu]g/m\3\.\49\
---------------------------------------------------------------------------

    \47\ 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.
    \48\ 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.
    \49\ MSHA selected these ranges based on the proposed PELs under 
consideration, then multiples of 100 [mu]g/m\3\ to show how data are 
distributed in the higher ranges. Table VIII-5 also presents 
additional exposure ranges corresponding to the 85.7 [mu]g/m\3\ 
concentration for coal samples.
---------------------------------------------------------------------------

    In Table VIII-2, the respirable crystalline silica exposure data 
for MNM miners are summarized by commodity and for the MNM industry as 
a whole, while Table VIII-3 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 
proposed PEL (50 [mu]g/m\3\). The exposure profile shows variability 
between the commodity categories: approximately 73 percent of metal 
miner exposures at or below the proposed PEL (50 [mu]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 VIII-4 and Table VIII-5 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 proposed PEL (50 [mu]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 [mu]g/
m\3\, respectively). Exposure values from the coal industry are 
expressed as ISO 8-hour TWAs, compatible with the proposed PEL.
BILLING CODE 4520-43-P

[[Page 44925]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.026


[[Page 44926]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.027


[[Page 44927]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.028


[[Page 44928]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.029

c. 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 VIII-2 through 
VIII-5, respirable crystalline silica exposures exceeded the proposed 
PEL of 50 [mu]g/m\3\ in about 18 percent of all MNM samples collected. 
Of all coal samples, exposure levels exceeded the proposed PEL in about 
seven percent of the samples. 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 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 is 
comprised of the Approval and Certification Center and the Pittsburgh 
Safety and Health Technology Center (including its Health Field 
Division, National Air and Dust Laboratory, Ventilation Division, and 
other specialized divisions). Table VIII-6 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 would provide those mines with the greatest 
benefit to reduce exposures below the proposed PEL and action level.
    Table VIII-6 shows MSHA's assessment of existing dust controls in 
mines (baseline conditions) and additional controls needed to meet the 
proposed 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 VIII-6 shows that metal mines have adopted 
extensive dust controls, while sand and gravel mines tend to have 
minimal engineering controls, if any.

[[Page 44929]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.030

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 preliminarily 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.
d. Respirable Crystalline Silica Exposure Controls Available to Mines
    Under the proposal, the mine operator must install, use, and 
maintain feasible engineering controls, supplemented by administrative 
controls, when necessary, to keep each miner's exposure at or below the 
proposed PEL. Engineering controls reduce or prevent miners' exposure 
to hazards.\50\ Administrative controls establish work practices that 
reduce the duration, frequency, or intensity of miners' exposures 
(although rotation of miners would be prohibited under the proposed 
rule).
---------------------------------------------------------------------------

    \50\ 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.
---------------------------------------------------------------------------

    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; NIOSH, 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);
     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

[[Page 44930]]

effectiveness and recognizing control failures or other conditions that 
need corrective action.\51\
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    \51\ 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.
---------------------------------------------------------------------------

(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 
preliminarily determined that various administrative controls are 
readily available to provide supplementary support to engineering 
controls. Examples of administrative controls would 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 would 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.\52\
---------------------------------------------------------------------------

    \52\ Proposed paragraph 60.11(b) prohibits the use of rotation 
of miners as an administrative control used for compliance with this 
part.
---------------------------------------------------------------------------

(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).
e. Maintenance
    MSHA preliminarily finds that a strong and feasible 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 2021a, 2019b). 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 including 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 2021a, 
2019b).53 54
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    \53\ 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).
    \54\ Acronyms: High efficiency particulate air (HEPA). Minimum 
efficiency reporting value (MERV).
---------------------------------------------------------------------------

     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 proposed 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 ensure that dust 
control equipment is functioning properly.
3. Feasibility Determination of Control Technologies
    MSHA is proposing a PEL of 50 [mu]g/m\3\ for MNM and coal mines. As 
NIOSH has documented, the mining industry has a wide range of options 
for controlling dust exposure that are already in various 
configurations in mines (2019b; 2021a). 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 combinations 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.

[[Page 44931]]

    MSHA also preliminarily finds that maintaining (including 
adjusting) or repairing existing controls would help achieve exposures 
at or below 50 [mu]g/m\3\. For example, NIOSH 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) (NIOSH, 
2019b). 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 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 operator was working in the poorly 
maintained enclosure, their exposure would continue to be 100 [mu]g/
m\3\, while for the other six hours (operating mobile equipment with a 
fully refurbished protective cab), the exposure level would 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.\55\ Greater 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 of the well-maintained enclosure.
---------------------------------------------------------------------------

    \55\ 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 would reduce the exposure of the operator inside. For 
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), would lead to lower 
exposure during the two hours the miner was 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 operator 
enclosure alone) to 23 [mu]g/m\3\ (improved operator enclosure plus 
dust suppression hopper).\56\ As an added benefit, any helper or 
utility worker in the truck loading area would also experience reduced 
exposure.
---------------------------------------------------------------------------

    \56\ 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\.
---------------------------------------------------------------------------

    Similarly, considering an example for 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) usually maintain 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. If instead 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.\57\ After water is delivered, drill respirable dust emissions will 
return to their normal level once water is again introduced into the 
drill bailing air.
---------------------------------------------------------------------------

    \57\ 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 preliminarily 
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.
a. Feasibility Findings for the Proposed PEL
    Based on the exposure profiles in Table VIII-2 and Table VIII-3 for 
MNM mines, and in Table VIII-4 and VIII-5 for coal mines, and the 
examples in the previous section that demonstrate the beneficial effect 
of combined controls, MSHA preliminarily finds that the proposed PEL of 
50 [mu]g/m\3\ is technologically feasible for all mines.
    Table VIII-7 summarizes the technological feasibility of control 
technologies available to the mining industry, by commodity. MSHA 
preliminarily 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.
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BILLING CODE 4520-43-C
b. Feasibility Findings for the Proposed Action Level
    MSHA believes that mine operators can achieve exposure levels at or 
below the proposed 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. 
MSHA notes that the exposure profiles in Table VIII-2 and Table VIII-3 
for MNM mines, and Table VIII-4 and VIII-5 for coal mines indicate that 
mine operators have already achieved the proposed action level for at 
least half of the miners who MSHA has sampled in each commodity 
category. However, to do so reliably for all miners, operators would 
need to upgrade equipment and facility designs, particularly in mines 
with higher respirable crystalline silica concentrations, that may be 
due to an elevated silica content in materials.
    One control option would be 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 will minimize 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 
proposed 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 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 proposed rule, mine operators would 
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

[[Page 44933]]

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 described in this section, which are already used 
in mines, although to a less rigorous extent than would be necessary to 
reliably achieve exposure levels of 25 [mu]g/m\3\ or lower for all 
miners.
    MSHA preliminarily finds that the proposed action level of 25 
[mu]g/m\3\ is technologically feasible for most mines. This finding is 
based on the exposure profiles, presented in Table VIII-2 and Table 
VIII-3 for MNM mines, and Table VIII-4 and VIII-5 for coal mines, which 
shows 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 control 
of respirable crystalline silica. Although most mines would need to 
adopt and rigorously implement a number of the control options 
mentioned in this section, the technology exists to achieve this level 
and is already in use in mines.

C. Technological Feasibility of Respiratory Protection (Within Proposed 
Part 60)

    Under the proposed rule, respiratory protection would only be 
allowed for temporary, non-routine use. MSHA has preliminarily 
determined that it is technologically feasible to limit respirator use 
to temporary, non-routine activities based on the Agency's knowledge of 
and experience with the mining industry, evidence presented by NIOSH 
(2019b, 2020a), and Tables VIII-2 through VIII-5 (exposure profiles for 
MNM and coal mines). These tables indicate that the proposed 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.
    Proposed Sec.  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 proposed paragraph would also require that an affected 
miner 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 operations have complied with the job transfer 
provisions under the existing standard in Sec.  57.5060(d)(7) that 
states miners unable to wear a respirator must be transferred to work 
in an existing position in an area of the mine where respiratory 
protection is not required. Proposed Sec.  60.14(b) is similar to these 
existing requirements. MSHA anticipates that mine operators would have 
a similar experience implementing the job transfer provisions of 
proposed Sec.  60.14(b). Therefore, MSHA preliminarily finds that the 
proposed requirement in Sec.  60.14(b) is technologically feasible.
    For miners who would need to wear respiratory protection on a 
temporary and non-routine basis, proposed Sec.  60.14(c)(1) would 
require 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 previously discussed, MSHA preliminarily finds 
that particulate respirators meeting these criteria would 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 suitability of 
the three particulate classifications for respirable size particle 
filtration and the broad commercial availability of these NIOSH-
approved particulate respirators.\58\ 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, 2022 
list P-100 elastomeric, P-100 filtering facepiece, and atmosphere-
supplying respirator models).\59\ Based on this information, MSHA 
preliminarily finds that proposed Sec.  60.14(c)(1) is technologically 
feasible.
---------------------------------------------------------------------------

    \58\ 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.
    \59\ 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.
---------------------------------------------------------------------------

    Proposed Sec.  60.14(c)(2) would incorporate the ASTM F3387-19 
``Standard Practice for Respiratory Protection'' to ensure that the 
most current and protective respiratory protection practices would be 
implemented by 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 proposed 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 preliminarily finds that the proposed 
Sec.  60.14(c)(2) is technologically feasible.
    Based on information contained in this section, MSHA preliminarily 
finds that proposed Sec.  60.14 is technologically feasible.

D. Technological Feasibility of Updated Respiratory Protection 
Standards (Amendments to 30 CFR Parts 56, 57, and 72)

1. Incorporation by Reference
    Respirators are commonly used by miners as a means of protection 
against a multitude of respiratory hazards, including particulates, 
gases, and vapors. Respirators are needed in immediately life-
threatening (i.e., IDLH) situations as well as operations where 
engineering controls and administrative controls do not provide 
sufficient protection against respiratory hazards. 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 proper protection, there is an increased risk of adverse health 
effects. Therefore, it is critical that respirators perform as they are 
designed.
    Accordingly, MSHA is proposing to incorporate by reference ASTM 
F3387-19 under 30 CFR 56.5005, 30 CFR 57.5005, and 30 CFR 72.710. With 
this action, the Agency intends to assist mine operators in developing 
effective respiratory protection practices and programs that meet 
current industry standards. This proposed revision would better protect 
miners who temporarily wear respiratory protection.
    The American National Standards Practices for Respiratory 
Protection ANSI Z88.2-1969 is currently incorporated by reference in 30 
CFR 56.5005, 30 CFR 57.5005, and 30 CFR

[[Page 44934]]

72.710.\60\ Since MSHA issued 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 based on the most recent consensus standard and 
provides more comprehensive and detailed guidance. MSHA believes that 
most mines that use respiratory protection are already following 
current respiratory protection practices 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 standards.
---------------------------------------------------------------------------

    \60\ 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).
---------------------------------------------------------------------------

2. Availability of Respirators
    The updated respiratory protection standard reflects current 
practice at many mines that currently use respiratory protection and 
does not require the use of new technology. Thus, MSHA preliminarily 
finds that the proposed update is technologically feasible for affected 
mines of all sizes.
3. Respiratory Protection Practices
    By incorporating the updated respiratory protection consensus 
standard (ASTM F3387-19), MSHA intends that mine operators would 
develop effective respiratory protection practices that meet the 
updated consensus standard and that would better protect miners from 
respirable hazards not yet controlled by other methods.
    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 1910.134. The 
respiratory protection program elements under ASTM F3387-19 are largely 
similar to those in the existing 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 fit testing and respirator training annually; 
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); and formalizing 
internal and external respiratory protection program reviews or audits.
    Overall, MSHA preliminarily finds that the proposed amendments to 
existing parts 56, 57, and 72 are technologically feasible because the 
requirements of ASTM F3378-19 are already implemented at some mines.

E. Technological Feasibility of Medical Surveillance (Within Proposed 
Part 60)

    Under the proposed rule, mine operators would be required to 
provide periodic medical examinations for each MNM miner, at no cost to 
the miner. The proposed medical surveillance standards would extend to 
MNM miners similar protections available to coal miners under 30 CFR 
72.100. The requirements in proposed Sec.  60.15 are consistent with 
the Mine Act's mandate to provide maximum health protection for miners.
    Under the proposed standards, MNM miners new to the mining industry 
would receive an initial examination, within 30 days. If they are not 
new to mining, they are categorized as belonging to a group of workers 
who are eligible for an examination every 5 years. Workers who are new 
to mining, after they have their initial examination, would be provided 
another 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 are eligible to have 
another follow-up exam in 2 years. After this additional 2-year follow-
up exam, 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 enter the category of miners eligible for 
periodic 5-year exams.
    MSHA is proposing that medical examinations would be performed by a 
PLHCP or specialist. A medical examination would include a review of 
the miner's medical and work history and physical examination. The 
medical and work history would cover a miner's present and past work 
exposures, illnesses, and any symptoms indicating respirable 
crystalline silica-related diseases and compromised lung function. The 
medical examination would include a chest X-ray. The required chest X-
ray would be required to 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 proposed rule 
would also require spirometry test be part of the medical examination.
    MSHA has preliminarily determined that it is technologically 
feasible for MNM mine operators to provide periodic examinations. The 
procedures required for initial and periodic medical examination are 
commonly conducted in the general population (i.e., medical history, 
physical examination, chest X-ray, spirometry test) by a wide range of 
practitioners with varying medical backgrounds. Because the proposed 
medical examinations consist of procedures conducted in the general 
population and because MSHA would be giving MNM mine operators maximum 
flexibility in selecting a PLHCP who would be able to offer these 
services, MSHA anticipates that operators would not experience 
difficulty in finding PLHCPs who are licensed to provide these 
services.
    In addition, in the case of classifying chest X-rays, MSHA has 
preliminarily determined that the availability of digital X-ray 
technology allows for electronic submission to remotely located B 
Readers for interpretation; therefore, MSHA anticipates that the 
limited number of B Readers in certain geographic locations would not 
be an obstacle for MNM operators. Overall, MSHA preliminarily finds 
that the proposed medical surveillance provisions are technologically 
feasible.

F. Conclusions

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

IX. Summary of Preliminary Regulatory Impact Analysis and Regulatory 
Alternatives

A. Introduction

    Executive Orders (E.O.s) 12866 and 13563 direct agencies to assess 
all costs and benefits of available regulatory alternatives and, if 
regulation is

[[Page 44935]]

necessary, to select regulatory approaches that maximize net benefits 
(including potential economic, environmental, public health and safety 
effects, distributive impacts, and equity). 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.
    A regulatory action is considered ``significant'' if it is likely 
to ``have an annual effect on the economy of $200 million or more . . 
.'' under E.O. 12866 Section 3(f)(1), as amended by E.O. 14094. The 
proposed rule ``Lowering Miners' Exposure to Respirable Crystalline 
Silica and Improving Respiratory Protection'' is a significant rule. To 
comply with E.O.s 12866 and 13563, MSHA has prepared a standalone PRIA 
for this proposed rule. A summary of the PRIA is presented below. The 
standalone PRIA contains detailed supporting data and explanation for 
the summary materials presented here, including the mining industry, 
costs and benefits, and economic feasibility. The standalone PRIA can 
be accessed electronically at http://www.msha.gov and has been placed 
in the rulemaking docket at www.regulations.gov, docket number MSHA-
2023-0001. MSHA requests comments on all estimates of costs and 
benefits presented in this PRIA and on the data, assumptions, and 
methodologies the Agency used to develop the cost and benefit 
estimates.

B. Miners and Mining Industry

    The proposed rule would affect mine operators and miners. This 
section provides information on the structure of the Metal/Nonmetal 
(MNM) and coal mining industries, including the revenue, number, 
employment by commodity and size; economic characteristics of MNM and 
coal mines; and the respirable crystalline silica exposure profiles for 
miners across different occupations in the MNM and coal industry. The 
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; the Statistics of US 
Businesses (SUSB); and the Energy Information Administration (EIA).
1. Structure of the Mining Industry
    The mining industry can be divided into two major sectors based on 
commodity: (1) Metal/Nonmetal mines (hereafter referred to as MNM 
mines) and (2) coal mines with further distinction made regarding type 
of operation (e.g., underground coal mines or surface coal mines). The 
MNM mining sector is made up of metal mines (copper, iron ore, gold, 
silver, etc.) and nonmetal mines. Nonmetal mines can be categorized 
into four commodity groups: (1) nonmetal (mineral) materials such as 
clays, potash, soda ash, salt, talc, and pyrophyllite; (2) sand and 
gravel, including industrial sand; (3) stone including granite, 
limestone, dolomite, sandstone, slate, and marble; and (4) crushed 
limestone.
    MSHA categorizes mines by size based on employment. For purposes of 
this industry profile, MSHA has categorized mines into the following 
four groups for analytical purposes \61\--mines that employ: (1) 1-20 
miners (Emp <=20); (2) 21 to 100 miners (20< Emp <=100); (3) 101 to 500 
miners (100< Emp <=500); and (4) 501 or more miners (500< Emp).
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    \61\ 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.
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    MSHA tracks mine characteristics and maintains a database 
containing the number of mines by commodity and size, number of 
employees, and employee hours worked. MSHA also collects data on the 
number of mining contractors, their employees, and employee hours. 
While contractors are issued a unique MSHA contractor identification 
number, they 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 
contractors, and revenues by commodity and size. All data are current 
in reference to the year 2019. In 2019, the MNM mining sector of 11,525 
mines employed 169,070 individuals, of which 150,928 were miners and 
18,142 were office workers. There were 1,106 coal mines that reported 
production and that employed 52,966 individuals, of which 51,573 were 
miners and 1,393 were office workers.
BILLING CODE 4520-43-P

[[Page 44936]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.032

BILLING CODE 4520-43-C
a. Metal Mining
    There are 24 groups of metal commodities mined in the U.S. Metal 
mines, which represent about 2.4 percent (280 out of 11,525) of all MNM 
mines and employ roughly 24.5 percent of all MNM miners. Of these 280 
mines, 157 employ 20 or fewer miners and 22 employ greater than 500 
miners. Additionally, the 2019 MSHA data show that there are a total of 
13,792 contract miners in the metal mining industry.
b. Non-Metal (Mineral) Mining
    Thirty-five non-metal commodities are mined in the U.S., not 
including stone, and sand and gravel. Non-metal mines represent about 
7.8 percent of all MNM mines and employ roughly 15 percent of all MNM 
miners. The majority of non-metal mines (71.9 percent) employ fewer 
than 20 miners and less than 1 percent employ more than 500 employees. 
In 2019, there were 11,346 contract miners in the non-metal mining 
industry.
c. Stone Mining
    The stone mining subsector includes eight different stone 
commodities. Seven of the eight are further classified as either 
dimension stone or crushed and broken stone. Stone mines make up 20.9 
percent of all MNM mines and employ 23.4 percent of all MNM miners. The 
majority of these mines (83.1 percent) employ less than 20 miners. In 
2019, there were 18,559 contract miners in the stone mining industry.

[[Page 44937]]

d. Crushed Limestone
    Crushed limestone mines make up 16.2 percent of all MNM mines and 
employ about the same percentage (16.0 percent) of all MNM miners. Of 
the 1,862 crushed limestone mines, 83.5 percent employ fewer than 20 
miners, and there are no crushed limestone mines that employ over 500 
miners. In 2019, there were 9,605 contract miners in the crushed 
limestone mining industry.
e. Sand and Gravel Mining
    Sand and gravel mines account for 52.7 percent of all MNM mines and 
employ 21.1 percent of all MNM miners. Nearly all (96.7 percent) of 
these mines employ fewer than 20 employees. In 2019, MSHA data show 
that there were 7,512 contract miners in the sand and gravel mining 
industry.
f. Coal
    In the coal sector, 707 mines (63.9 percent) employed fewer than 20 
miners. Overall, coal mine employment in 2019 was 52,966, of which 
51,573 were miners and the remaining 1,393 were office workers. 
Additionally, there were a total of 22,003 contract miners in the coal 
mining industry in 2019.
2. Economic Characteristics of the Metal/Non-Metal Mining Industry
    The value of all MNM mining output in 2019 was estimated at $83.8 
billion (U.S. Department of Interior, 2019). Metal mines, which include 
iron, gold, copper, silver, nickel, lead, zinc, uranium, radium, and 
vanadium mines, contributed $26.9 billion. In the USGS Mineral 
Commodity Summaries, nonmetals, stone, sand and gravel, and crushed 
limestone are combined in to one commodity group called industrial 
minerals. MSHA estimated the production value of each individual 
commodity by applying the proportion of revenues represented by each 
among all commodities in the SUSB and applying that proportion to the 
2019 production value for all industrial minerals reported by USGS. 
This approach yielded the following estimates: metal production was 
valued at $26.9 billion, non-metal production at $22.3 billion, stone 
mining at $12.85 billion, sand and gravel at $9.0 billion, and crushed 
limestone at $12.7 billion.
    Production in the U.S. coal sector amounted to 706.1 million tons 
in 2019.\62\ To estimate coal revenues in 2019, MSHA combined 
production estimates with prices per ton. Mine production data was 
taken from MSHA quarterly data and the coal price per ton was taken 
from the 2019 EIA Annual Coal Report. As shown in Table IX-1, total 
coal revenues in 2019 equaled $25.6 billion.
---------------------------------------------------------------------------

    \62\ Source: MSHA MSIS Data (reported on MSHA Form 7000-2).
---------------------------------------------------------------------------

    The U.S. coal mining sector produces three major types of coal: 
bituminous, lignite, and anthracite. According to MSHA data, bituminous 
operations account for approximately 92.1 percent of total coal 
production in short tons, and 91.9 percent of all coal miners. Lignite 
operations account for roughly 7.5 percent of total coal production and 
6.2 percent of coal miners. Anthracite operations account for 0.4 
percent of coal production and 1.9 percent of coal miners.

C. Cost-Benefit Analysis

    The PRIA is based on MSHA's Preliminary Risk Analysis and the 
Technological Feasibility analysis. The PRIA presents estimated 
benefits and costs of the proposed rule for informational purposes 
only. Under the Mine Act, MSHA is not required to use estimated net 
benefits as the basis for its decision. MSHA requests comments on the 
methodologies, baseline, assumptions, and estimates presented in the 
PRIA and also asks for any data or quantitative information that may be 
useful in evaluating the estimated costs and benefits associated with 
the proposed rule. The PRIA assesses the costs and benefits in the MNM 
and coal industries of reducing miners' exposures to silica to 50 
[mu]g/m\3\ for a full shift, calculated as an 8-hour time weighted 
average (TWA) and of complying with the standard's ancillary 
requirements. The PRIA also assesses the costs and benefits from 
requiring medical surveillance of MNM miners. It also assesses the 
costs and benefits from revising the existing respiratory protection 
standards. MSHA is proposing to incorporate by reference ASTM F3387-19, 
``Standard Practice for Respiratory Protection'' (ASTM F3387-19). ASTM 
F3387-19 would replace the 1969 American National Standards Institute 
(ANSI) ``Practices for Respiratory Protection.''
    MSHA estimates the proposed rule would have an annualized cost of 
$57.6 million in 2021 dollars at a real discount rate of 3 percent. Of 
this cost, over 55 percent is attributable to exposure monitoring; 30 
percent to medical surveillance; 10 percent to engineering, improved 
maintenance and repair, and administrative controls; 2.4 percent 
related to the selection, use, and maintenance of approved respirators 
in accordance with ASTM F3387-19, respiratory protection practices; and 
1.8 percent to additional respiratory protection (e.g., when miners 
need temporary respiratory protection from exposure at the proposed PEL 
when it would not have been necessary at the existing PEL). MSHA 
further estimates that the MNM sector will incur $52.7 million (91 
percent), and the coal sector will incur $4.9 million (9 percent) in 
annualized compliance costs (see Table IX-2).
BILLING CODE 4520-43-P

[[Page 44938]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.033

    In its analysis, MSHA annualizes all costs using 3 percent and 7 
percent discount rates as recommended by OMB. MSHA bases the 
annualization periods for expenditures on equipment life cycles and 
primarily uses a 10-year annualization period for one-time costs and 
20-year for medical surveillance. However, MSHA annualizes the benefits 
of the proposed rule over a 60-year period to reflect the time needed 
for benefits to reach the steady-state values projected in MSHA's PRA. 
Therefore, MSHA's complete analysis of this rule is 60 years (which 
corresponds to 45 years of working life and 15 years of retirement for 
the current miner population). MSHA holds the employment and production 
constant over this period for purposes of the analysis.\63\
---------------------------------------------------------------------------

    \63\ This modeling strategy implicitly assumes that the ten-year 
cost annualization repeats five more times to cover the same 60-year 
analytic period as the benefits model. Thus, one-time costs incurred 
in the first year implicitly repeat in years 11, 21, 31, 41 and 51. 
This may introduce a tendency toward overestimation of compliance 
costs.
---------------------------------------------------------------------------

    For both MNM and coal mines, the estimated costs to comply with the 
proposed 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).
    MSHA estimates that:
    [ssquf] The proposed respirable crystalline silica rule will result 
in a total of 799 lifetime avoided deaths (63 in coal and 736 in MNM 
mines) and 2,809 lifetime avoided morbidity cases (244 in coal and 
2,566 in MNM mines) once it is fully effective (i.e., beginning 60 
years post rule promulgation through year 120 such that all miners, 
working and retired, have been exposed only under the proposed PEL) 
(see Table IX-3).
    [ssquf] Over the first 60 years, annual cases avoided will increase 
gradually to the steady-state values (i.e., long-run per-year 
averages). Upon reaching the steady-state values, annual cases avoided 
will be constant from year 60 onward because all miner cohorts will 
have identical lifetime risks. From Table IX-4, in the first 60 years, 
the proposed rule would result in a total of 410 avoided deaths (377 in 
MNM and 33 in Coal) and 1,420 avoided morbidity cases (1,298 in MNM and 
122 in Coal), which are the benefits MSHA monetized in its benefits 
analysis.
    [ssquf] The total benefits of the proposed respirable crystalline 
silica rule from these avoided deaths and morbidity cases are $175.7 
million per year in 2021 dollars.

--The majority (60.7 percent) of these benefits ($108.0 million) are 
attributable to avoided mortality due to non-malignant respiratory 
disease (NMRD) ($52.8 million), silicosis ($28.1 million), and end-
stage renal disease (ESRD) ($19.9 million), and lung cancer ($7.2 
million).
--Benefits from avoided morbidity due to silicosis are $53.2 million 
per year: $48.7 million for MNM mines and $4.6 million for coal mines 
(see Table IX-5).
--Benefits from avoided morbidity that precedes fatal cases associated 
with NMRD, silicosis, renal disease, and lung cancer, are $14.5 
million: $13.3 million for MNM mines and $1.2 million for coal mines 
(see Table IX-5).

[[Page 44939]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.034

[GRAPHIC] [TIFF OMITTED] TP13JY23.035


[[Page 44940]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.036

    MSHA acknowledges that its benefit estimates are influenced by the 
underlying assumptions and that the long-time frame of this analysis 
(first 60 years) is a source of uncertainty. The main assumptions 
underlying these estimates of avoided mortality and morbidity include 
the following:
    [ssquf] Employment and production are held constant over the 60 
years--the analysis period of the proposed rule.\64\
---------------------------------------------------------------------------

    \64\ MSHA recognizes that it is impossible to predict economic 
factors over such a long period. Given known information and 
forecast limitations, MSHA believes this is a reasonable assumption.
---------------------------------------------------------------------------

    [ssquf] Any miners currently exposed above the existing PELs are 
exposed to levels of respirable crystalline silica at existing 
standards (100 [mu]g/m\3\ for a full-shift exposure, calculated as an 
8-hour TWA at MNM mines and 85.7 [mu]g/m\3\ for a full-shift exposure, 
calculated as an 8-hour TWA at coal mines).
    [ssquf] The proposed rule will result in miners being exposed at or 
below the proposed PEL (50 [mu]g/m\3\).
    [ssquf] Miners have identical employment and hence exposure tenures 
(45 years). The assumptions inherent in developing the exposure-
response functions for the modeled health outcomes are reasonable 
throughout the exposure ranges relevant to this benefits analysis. In 
the final rule, the agency plans to augment the Regulatory Impact 
Analysis, for informational purposes, so as to incorporate different 
durations of working life based on exposure information, while 
continuing to also present calculations based on a 45-year working life 
assumption.
    In addition to the above quantified health benefits of the lower 
PEL, MSHA projects that there would be additional benefits from 
requiring approved respirators be selected, used, and maintained in 
accordance with the requirements, as applicable, of ASTM F3387-19. The 
ASTM standard reflects developments in respiratory protection since 
MSHA issued its existing standards. These developments include OSHA's 
research and rulemaking on respiratory protection. Under the proposed 
rule, MSHA would require operators' respiratory protection plans to 
include minimally acceptable respiratory program elements: program 
administration; standard operating procedures (SOPs); medical 
evaluation; respirator selection; training; fit testing; and 
maintenance, inspection, and storage. Given the uncertainty about the 
current state of operator respiratory protection practices, MSHA did 
not quantify the benefits that would be realized by requiring approved 
respirators to be selected, used, and maintained in accordance with 
ASTM F3387-19.
    MSHA believes the proposed rule would lower exposures to respirable 
crystalline silica and respirable coal mine dust. The available 
exposure-response models do not account for separate health effects 
from exposure to mixed dust that contains both respirable crystalline 
silica and coal mine dust. However, MSHA anticipates that there would 
be additional unquantified benefits provided by the proposed rule--
reduced adverse health outcomes attributable to respirable coal mine 
dust exposure, such as CWP.\65\ The proposed rule does quantify the 
benefits of avoided deaths and illnesses from reducing coal miners' 
exposures to respirable crystalline silica. Among coal miners, MSHA 
estimates 35 lifetime avoided deaths and illnesses from NMRD (see Table 
IX-3).
---------------------------------------------------------------------------

    \65\ The following references document miner exposures that 
could be simultaneously below the PEL for RCMD but exceed the PEL 
for silica: Rahimi, E., Shekarian, Y., Shekarian, N. et al. 
Investigation of respirable coal mine dust (RCMD) and respirable 
crystalline silica (RCS) in the U.S. underground and surface coal 
mines. Sci Rep 13, 1767 (2023). https://doi.org/10.1038/s41598-022-24745-x.
    Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G, 
Laney AS. Respirable coal mine dust in underground mines, United 
States, 1982-2017. Am J Ind Med. 2019 Jun;62(6):478-485. doi: 
10.1002/ajim.22974. Epub 2019 Apr 29. PMID: 31033017; PMCID: 
PMC6800046.
    Doney BC, Blackley D, Hale JM, Halldin C, Kurth L, Syamlal G, 
Laney AS. Respirable coal mine dust at surface mines, United States, 
1982-2017. Am J Ind Med. 2020 Mar;63(3):232-239. doi: 10.1002/
ajim.23074. Epub 2019 Dec 9. PMID: 31820465; PMCID: PMC7814307.
---------------------------------------------------------------------------

    Finally, MSHA also expects that the proposed rule's medical 
surveillance provisions would 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, would 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

[[Page 44941]]

improve health outcomes. However, as noted, MSHA lacks data to quantify 
these additional benefits.
    The net benefits of the proposed rule are the differences between 
the estimated benefits and costs. Table IX-6 shows estimated net 
benefits using alternative discount rates of 0, 3, and 7 percent for 
benefits and costs. As is observed from the table, the choice of 
discount rate has a significant effect on annualized costs, benefits, 
and hence net benefits. While the net benefits of the proposed 
respirable crystalline silica rule vary considerably depending on the 
choice of discount rate used to annualize costs and benefits, total 
benefits exceed total costs under each discount rate considered. MSHA's 
estimate of the net annualized benefits of the proposed rule, using a 
uniform discount rate for both costs and benefits of 3 percent, is 
$118.2 million a year with the largest share ($108.8 million; 92.0 
percent) attributable to the MNM sector.
[GRAPHIC] [TIFF OMITTED] TP13JY23.037

D. Economic Feasibility

    To establish economic feasibility, MSHA uses a revenue screening 
test--whether the yearly costs of a rule are less than 1 percent of 
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. The resulting ratio of 
annualized compliance costs to revenues from the screener analysis 
should be interpreted with care. If annualized compliance costs 
comprise less than 1 percent of revenue, the Department of Labor 
presumes that the affected entities can incur the compliance costs 
without significant economic impacts.
    For the MNM and coal mining sectors, MSHA estimates the projected 
impacts of the rule by calculating the average annualized compliance 
costs for each sector as a percentage of total revenues. To be 
consistent with costs that are calculated in 2021 dollars, MSHA first 
inflated mine revenues expressed in 2019 to their 2021 equivalent using 
the GDP Implicit Price Deflator. Due to inflation, the nominal value of 
a dollar in 2021 is estimated to be about 5.4 percent higher than in 
2019.

[[Page 44942]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.038

    Table IX-8 presents the projected impacts of the proposed rule. The 
table compares aggregate annualized compliance costs for MNM and coal 
sectors at a 0 percent, 3 percent, and 7 percent real discount rate to 
total annual revenues. At a 3 percent real discount rate, total 
aggregate annualized compliance costs are projected to be $57.6 million 
(including both 30 CFR part 60 and 2019 ASTM Upgrade Costs), while 
aggregate revenues are estimated to be $115.3 billion in 2021 dollars. 
Thus, the mining industry is expected to incur compliance costs that 
comprise 0.05 percent of total revenues.
    For the MNM sector, MSHA estimates that the annualized costs of the 
proposed rule (including ASTM update costs) would be $52.7 million at 3 
percent discount rate, which is approximately 0.06 percent of total 
annual revenue of $88.3 billion ($52.7 million/$88.3 billion) for MNM 
mine operators. For the coal sector, MSHA estimates that the annualized 
cost of the proposed rule would also be $4.9 million at 3 percent, 
which is approximately 0.02 percent of total annual revenue of $27.0 
billion ($4.9 million/$27.0 billion) for coal mine operators.
    The ratios of screening analysis are well below the 1.0 percent 
threshold, and therefore, MSHA has concluded that the requirements of 
the proposed rule are economically feasible, and no sector of the 
industry will likely incur significant costs.
[GRAPHIC] [TIFF OMITTED] TP13JY23.039

E. Regulatory Alternatives

    The proposed rule presents a comprehensive approach for lowering 
miners' exposure to respirable crystalline silica. The proposal 
includes the following regulatory provisions: lowering miners' 
respirable crystalline silica exposure to a PEL of 50 [mu]g/m\3\ for a 
full-shift exposure, calculated as an 8-hour TWA; initial baseline 
sampling for miners who are reasonably expected to be exposed to 
respirable crystalline silica; periodic sampling for miners who are at 
or above the proposed action level of 25 [mu]g/m\3\ but at or below the 
proposed PEL of 50 [mu]g/m\3\; and semi-annual evaluation of changing 
mining processes that would reasonably be expected to result in new or 
increased exposures.
    In developing the proposed rule, MSHA considered two regulatory 
alternatives. Both alternatives include less stringent monitoring 
provisions than the proposed monitoring provisions. One of the 
alternatives also combines less stringent monitoring with a more 
stringent PEL. MSHA discusses the regulatory options in the sections 
below, from least expensive to most expensive. Both alternatives would 
retain the respiratory protection updates and medical surveillance from 
the proposed rule.
1. Regulatory Alternative #1: Changes in Sampling and Evaluation 
Requirements
    Under this alternative, the proposed PEL would remain unchanged at 
50 [mu]g/m\3\ and the proposed action level would remain unchanged at 
25 [mu]g/m\3\. Further, mine operators would conduct: (1) baseline 
sampling for miners who may be exposed to respirable crystalline silica 
at or above the proposed action level of 25 [mu]g/m\3\, (2) periodic 
sampling twice per year for miners who are at or above the proposed 
action level of 25 [mu]g/m\3\ but at or below the proposed PEL of 50 
[mu]g/m\3\, and (3) annual evaluation of changing mining processes or 
conditions that would reasonably be

[[Page 44943]]

expected to result in new or increased exposures.
    Mine operators would be required to undertake sampling under this 
regulatory alternative and would thus incur compliance costs. However, 
monitoring requirements under this alternative are less stringent than 
the requirements under the proposed rule because the number of miners 
to be sampled for baseline sampling would be smaller than in the 
proposed rule and the frequency of periodic sampling and evaluations of 
changing mining processes or conditions are set at half the frequency 
of the proposed monitoring requirements. Therefore, the cost of 
compliance will be lower under this alternative. MSHA estimates that 
annualized monitoring costs will total $17.3 million for this 
alternative (at a 3 percent discount rate), compared to $32.0 million 
for the proposed monitoring requirements, resulting in an estimated 
$14.7 million in lower costs per year (Table IX-9).
    Although this alternative does not eliminate exposure monitoring, 
the requirements are minimal relative to the monitoring requirements 
under the proposed rule. However, 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, quarterly monitoring 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 
would enable mine operators to take measures necessary to ensure 
continued compliance with the PEL. Further, more frequent monitoring 
would 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] TP13JY23.040

    MSHA also believes that requiring more frequent periodic sampling 
would provide mine operators with greater confidence that they are in 
compliance with the proposed rule. Because of the variable nature of 
miner exposures to airborne concentrations of respirable crystalline 
silica, maintaining exposures below the proposed action level 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 proposed sampling requirements justify the additional costs 
relative to Regulatory Alternative 1.
2. Regulatory Alternative #2: Changes in Sampling and Evaluation 
Requirements and the Proposed PEL
    Under this regulatory alternative, the proposed PEL would be set at 
25 [mu]g/m\3\; mine operators would install whatever controls are 
necessary to meet this PEL; and no action level would be proposed. 
Further, mine operators: (1) would not be required to conduct baseline 
sampling or periodic sampling; (2) would conduct semi-annual 
evaluations of changing conditions; and (3) would sample as frequently 
as necessary to determine the adequacy of controls.
    Mine operators would not be required to undertake baseline or 
periodic sampling. However, mine operators would be required to perform 
semi-annual evaluations of changing mining processes or conditions. 
Further, mine operators would be required to perform post-evaluation 
sampling when the operators determine as a result of the semi-annual 
evaluation that miners may be exposed to respirable crystalline silica 
at or above proposed PEL at 25 [mu]g/m\3\. When estimating the cost of 
the proposed monitoring requirements, MSHA assumes that the number of 
samples for corrective action and semi-annual evaluation are relatively 
small (2.5 percent of miners) because samples from sampling to 
determine the adequacy of controls and from MSHA can both be used to 
meet the requirements. Since this alternative

[[Page 44944]]

does not require periodic sampling, MSHA increases samples after each 
evaluation to 10 percent of miners to ensure the monitoring 
requirements can be met.
    This alternative also sets the proposed PEL at 25 [mu]g/m\3\. In 
addition to the estimated cost of compliance with a PEL of 50 [mu]g/
m\3\, mine operators would incur additional engineering control costs 
to meet a PEL of 25 [mu]g/m\3\. To estimate these additional 
engineering control costs, MSHA largely uses the same methodology as 
for mines affected at the proposed 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 proposed 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\.\66\
---------------------------------------------------------------------------

    \66\ About 8,053 of mines active in 2019 either did not have a 
sample > 25 [mu]g/m\3\ or did not have a sample in the last 5 years.
---------------------------------------------------------------------------

    To this number, MSHA adds the 1,226 affected mines expected to 
incur costs to reach the proposed PEL of 50 [mu]g/m\3\. Based on its 
experience and knowledge, MSHA does not expect the mines that installed 
engineering controls to meet the PEL of 50 [mu]g/m\3\ will also be able 
to comply with a PEL of 25 [mu]g/m\3\. For example, to comply with the 
proposed 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 costed in the 
following section. 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 costed in the following section. 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 PEL of 25 [mu]g/
m\3\ under this alternative. MNM mines account for 4,087 (87 percent) 
and coal mines 616 (13 percent). Further, of the estimated 4,087 MNM 
mines and 616 coal mines, 1,096 MNM mines (27 percent) and 130 coal 
mines (21 percent) are also estimated to incur compliance costs to 
reach the proposed PEL of 50 [mu]g/m\3\.
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 PEL of 25 
[mu]g/m\3\ under consideration for this alternative. While MSHA assumes 
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 assumes 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 assumes 
operating and maintenance (O&M) costs to be 35 percent of initial 
capital expenditure and installation cost, when appropriate, will be 
equal to the initial capital expenditure (Table IX-10). MSHA also 
assumes the larger capital expenditure controls will have a 30-year 
service life. MSHA welcomes public comment concerning the engineering 
controls selected for this analysis and the assumptions used to 
estimate installation and O&M costs for these controls.
[GRAPHIC] [TIFF OMITTED] TP13JY23.041

    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-10 will 
not be sufficient. For example, respirable crystalline silica dust 
exposure at such a stringent limit

[[Page 44945]]

as 25 [mu]g/m\3\ is likely to occur at more than one area of the mine; 
in addition to increasing ventilation to a crusher/grinder, enclosing 
and ventilating the conveyor belt mine would be necessary to reduce 
concentrations below the limit. Similarly, increasing facility 
ventilation from 20 to 30 air changes per hour may not be adequate to 
meet the limit; 40 air changes per hour might be necessary. Therefore, 
MSHA assumes mine operators will purchase and install at least two of 
the engineering controls listed in Table IX-10. This may be a 
conservative assumption.
    Table IX-11 presents the average annualized engineering control 
costs per mine and total annualized engineering control costs by mine 
sector. Because the service life of nearly all components is expected 
to be 30 years, the costs of all engineering controls are annualized 
over 30 years. At a 3 percent real discount rate, the average 
annualized engineering control costs are about $94,300 per mine, 
resulting in an additional cost of $443.6 million if the PEL is set at 
25 [mu]g/m\3\ instead of 50 [mu]g/m\3\.
[GRAPHIC] [TIFF OMITTED] TP13JY23.042

    Table IX-12 summarizes the estimated annualized cost of this 
alternative under consideration. At a 3 percent real discount rate, 
exposure monitoring costs less than the proposed rule; however, this 
lower 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 $491.2 million, this alternative would cost nearly 
eight times more than the proposed requirements.
[GRAPHIC] [TIFF OMITTED] TP13JY23.043


[[Page 44946]]


    This alternative requires exposure monitoring that is more 
stringent than Regulatory Alternative 1, but less stringent than the 
proposed requirements. In addition, Regulatory Alternative 2 increases 
miner protection by proposing to set the PEL at 25 [mu]g/m\3\, 
resulting in measurable avoided mortality and other health benefits. 
Table IX-13 presents the avoided morbidity and mortality cases over the 
60-year regulatory analysis time horizon under this alternative. Under 
this alternative, the avoided 60-year mortality is expected to be 981, 
which is 2.4 times higher than the expected avoided mortality of 410 
under a proposed PEL of 50 [mu]g/m\3\. The avoided 60-year morbidity 
under the regulatory alternative of 25 [mu]g/m\3\ is expected to be 
1,948, which is 1.4 times higher than the expected avoided 60-year 
morbidity of 1,420 under the proposed PEL of 50 [mu]g/m\3\.
[GRAPHIC] [TIFF OMITTED] TP13JY23.044

    Table IX-14 presents the benefits associated with this avoided 
morbidity and mortality. The expected total benefits, discounted at 3 
percent, are $365.5 million, which is twice the expected total benefits 
of $175.7 million under the proposed PEL of 50 [mu]g/m\3\. Under this 
regulatory alternative, these benefits are made up of $258.0 million 
due to avoided mortality, $34.5 million due to morbidity preceding 
mortality, and $73.0 million due to morbidity not preceding mortality. 
However, when compared to the annualized costs, the net benefits of 
this alternative are negative at both a 3 percent and 7 percent real 
discount rate.

[[Page 44947]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.045

BILLING CODE 4520-43-C
    MSHA solicits further comment on the extent to which these or other 
regulatory alternatives (including different ways of calculating 
respirable crystalline silica concentration) may change the effects of 
the proposed rule.

X. Initial Regulatory Flexibility Analysis

    The Regulatory Flexibility Act (RFA) of 1980, as amended by the 
Small Business Regulatory Enforcement Fairness Act (SBREFA) of 1996, 
requires preparation of an Initial Regulatory Flexibility Analysis 
(IRFA) for any rule that by law must be proposed for public comment, 
unless the agency certifies that the rule, if promulgated, will not 
have a significant economic impact on a substantial number of small 
entities. 5 U.S.C. 601- 612. Because MSHA's proposed rule on respirable 
crystalline silica, including the incorporation of ASTM F3387-19 by 
reference, would regulate the mining industry, the proposed rule falls 
within the purview of the RFA. MSHA has evaluated the impact of the 
proposed rule on small entities in this IRFA. MSHA's analysis is 
presented in the following.

Description of the Reasons Why MSHA is Considering Regulatory Action

    Based on its review of the health effects literature, MSHA has 
preliminarily determined that occupational exposure to respirable 
crystalline silica causes silicosis and other diseases. Based on its 
preliminary risk analysis, MSHA has also determined that under its 
existing standards, miners face a risk of material impairment of health 
or functional capacity from exposures to respirable crystalline silica.
    Based on these preliminary determinations, MSHA proposes to amend 
its existing standards to better protect miners against occupational 
exposure to respirable crystalline silica, a carcinogen, and to improve 
respiratory protection for all airborne contaminants. The proposed rule 
would establish for mines of all sizes, a PEL of 50 [micro]g/m\3\ for a 
full shift, calculated as an 8-hour TWA, for all miners, and an action 
level of 25 [micro]g/m\3\ for a full-shift exposure, calculated as 8-
hour TWA. MSHA's proposal would also include other requirements to 
protect miner health, such as periodic exposure sampling and corrective 
actions to be taken when miners' exposures exceed the PEL. MSHA also 
proposes to replace existing requirements for respiratory protection 
and to incorporate by reference the ASTM F3387-19 Standard Practice for 
Respiratory Protection. MSHA believes that the proposed changes would 
significantly improve health protections for all miners over the course 
of their working lives.

Objectives of, and Legal Basis for, the Proposed Rule

    The proposed rule would fulfill MSHA's statutory obligation to 
``promulgate improved mandatory health . . . standards to protect'' 
miners' health under the Mine Act, as amended. 30 U.S.C. 801(g). 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). The Secretary must set standards 
to assure, based on the best available evidence, that no miners 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). 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 
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.

[[Page 44948]]

Description and Estimate of the Number of Small Entities to Which the 
Proposed Rule Would Apply

    The proposed rule would affect MNM and coal mining operations. To 
determine the number of small entities subject to the proposed rule, 
MSHA reviewed the North American Industrial Classification System 
(NAICS), the standard used by Federal statistical agencies in 
classifying business establishments, as well as information from the 
Office of Advocacy of the Small Business Administration (SBA). MSHA 
used its data from the MSHA Standardized Information System (MSIS) to 
identify the responsible party for each mine. MSHA then combined that 
information with the size classification information.
    First, MSHA determined that mining operations that fall into 25 
NAICS-based industry classifications may be subject to the proposed 
rule. These industry categories and their accompanying six-digit NAICS 
codes are shown in Table X-1.\67\
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    \67\ The NAICS classifications used in this analysis are drawn 
from a recent version of the NAICS (though, for reasons described 
below, not the latest version, which was published in January 2022). 
SBA established definitions of small entities for each of the 
categories in the earlier version, which were effective in August 
2019. This version of NAICS categories was needed for this analysis, 
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, which prevented MSHA from using those categories. MSHA 
identified 25 NAICS categories (in the previous system) that 
accounted for all mining activities.
---------------------------------------------------------------------------

    Second, MSHA matched the NAICS classifications with SBA small-
entity size standards (based on number of employees) to determine the 
number of small entities within each of the respective NAICS codes. See 
Table X-1.
    Third, MSHA counted the number of small-entity controllers in each 
NAICS code, after determining that a ``controller'' who owns and 
controls a mine as the appropriate unit of this IRFA analysis (based on 
SBA guidance) (Small Business Administration 2017). A controller is a 
parent company owning or controlling one or more mines. A controller 
can also be a firm, whereas a mine can be an establishment. Table X-1 
shows the count of all controllers and a count of small-entity 
controllers in each NAICS code. Some ``unique controllers'' are 
included in more than one NAICS code because they own or control 
multiple mines, each producing a different commodity. For this 
analysis, however, MSHA single-counted these unique controllers; for 
example, a controller who owns three mines in three different NAICS 
codes was only counted once.
    Based on this methodology, MSHA estimated that in 2021, there were 
a total of 5,879 controllers, 5,007 of which were small-entity 
controllers. Many controllers owned one or two mines, while some 
controllers owned hundreds of mines nationwide (or worldwide). The 
5,007 small-entity controllers owned a total of 8,240 mines out of 
11,791 mines in operation in 2021.\68\
---------------------------------------------------------------------------

    \68\ 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 were available. Such information about 
controllers as parent companies might include, for example, 
knowledge of whether the parent company is a large, multinational 
corporation, which has bearing on this regulatory flexibility 
analysis. Because the benefit-cost analysis performed on the 
proposed rule did not need this kind of detailed information about 
controllers, it was able to have a broader scope to include data 
from other years besides 2021, which it did. As a result, the 
benefit cost analysis included a larger number of mines (and 
affected mines) and controllers. The key factor for this regulatory 
flexibility analysis is the estimated ratio of the regulatory cost 
per revenue for controllers, as reflected by the most current data. 
The estimation of this ratio is robustly addressed in MSHA's 
analysis of the 5,879 controllers in 2021 (which is not impacted by 
the exclusion of other years in this analyis).
---------------------------------------------------------------------------

BILLING CODE 4520-43-P

[[Page 44949]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.046

BILLING CODE 4520-43-C

[[Page 44950]]

Description of the Projected Reporting, Recordkeeping, and Other 
Compliance Requirements for Small Entities

    As explained earlier, the proposed rule would establish a PEL of 50 
[micro]g/m\3\ and an action level of 25 [micro]g/m\3\ for a full-shift 
exposure, calculated as 8-hour TWA. The proposed rule would also 
include other requirements. Examples include baseline, periodic, and 
corrective action sampling, semi-annual evaluations, medical 
surveillance, respiratory protection, and recordkeeping.
    With regard to the paperwork burden on small entities, MSHA's 
proposed rule would create new information collection requests for the 
mining industry. As described in greater detail in Section XI below, 
these requirements include the collection of information involving: (1) 
exposure monitoring--samplings and semi-annual evaluations, (2) 
corrective actions taken, (3) miners unable to wear respirators, and 
(4) medical surveillance for MNM miners. Table XI-2 displays an annual 
estimate of information collection burden for the whole mining 
industry. Compliance costs on small entities that include recordkeeping 
costs are discussed below.

Estimation of the Compliance Costs and Relative Burden to Small 
Entities

    MSHA estimated the average annual regulatory cost per small-entity 
controller (based on a 3 percent discount rate), as well as the average 
annual revenue per small-entity controller. MSHA estimated, for each 
controller, the additional annual cost of the proposed regulation as a 
proportion of that controller's annual revenue. The average of these 
proportions (weighting controllers equally) was 0.122 percent, below a 
3 percent threshold used for significant impact. That is, for every $1 
million in revenue earned by a controller, the average regulatory cost 
was estimated to be $1,220.
    Total Compliance Cost. MSHA estimated that the proposed rule would 
have an average cost of $60.23 million per year in 2021 dollars at a 
real discount rate of 3 percent. The estimated costs for the proposed 
rule would represent the additional costs necessary for mine operators 
to achieve full compliance with the proposed rule.
    Compliance Costs by Small-Entity Controllers. Because mines (as 
well as controllers) vary in the scale of their operations, MSHA first 
estimated additional regulatory costs on a per-miner basis. MSHA 
anticipated that the additional regulatory costs per miner would vary 
across the six major commodity categories: coal, metal, nonmetal, 
stone, crushed limestone, and sand and gravel. MSHA analyzed employment 
data linked with controller data. By combining this information with 
compliance cost information, MSHA derived estimates of the regulatory 
costs for small-entity controllers. MSHA then estimated the regulatory 
cost for each of the 5,007 small-entity controllers identified in 2021. 
See the average annual regulatory cost per controller in Table X-2.
    Revenues by Small-Entity Controllers. 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).\69\ The SUSB data provided revenue estimates for enterprises in 
each NAICS code and for each ``size category'' (based on number of 
employees) within each NAICS code. The enterprise data considered 
controllers that had operations in more than one NAICS code. MSHA 
summed the estimated revenue for the establishments within the same 
NAICS code to create multiple enterprises with different NAICS codes 
and compare constructed enterprises with the SUSB data to estimate the 
revenue for each of these size-category-specific enterprises. This 
methodology was relevant for the ``largest'' of small-entity 
controllers, which controlled more than one mine, sometimes operating 
in different NAICS categories. Most small-entity controllers operated 
only one mine, meaning that no summation was required because only the 
number of employees in a single mine needed to be counted.
---------------------------------------------------------------------------

    \69\ 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. 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. 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.
---------------------------------------------------------------------------

    MSHA estimated revenues for each small-entity controller. Some 
small-entity controllers had mines belonging to different NAICS codes. 
This factor precluded MSHA from being able to precisely categorize 
small-entity controllers by NAICS code. MSHA estimated each small-
entity controller's revenues.\70\
---------------------------------------------------------------------------

    \70\ 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 may also have operations in 
non-mining industries. If so, total revenues, including those from non-
mining operations, would be higher than estimated here, and the ratios 
of regulatory costs to revenues shown in the summary table may be 
overestimated.
    MSHA developed estimates of the number of miners for each small-
entity controller, and for each NAICS category 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-2.
    Ratio of Compliance Cost to Revenue. From the two sets of estimates 
described above--costs and revenues--for each small-entity controller, 
MSHA generated estimates of the ratios of regulatory cost to revenue, 
for each controller. Table X-2 shows the number of controllers, average 
annual regulatory costs, average annual revenue, and average cost as a 
percent of revenue.

[[Page 44951]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.047

Relevant Federal Rules Which May Duplicate, Overlap, or Conflict With 
the Proposed Rule

    There are no Federal rules that may duplicate, overlap, or conflict 
with the proposed rule.

Significant Alternatives and Their Impact on Small Entities

    MSHA considered two alternatives in the proposed rule. Under 
Alternative 1, the proposed PEL would remain unchanged at 50 [mu]g/m\3\ 
and the proposed action level would remain unchanged at 25 [mu]g/m\3\. 
Further, mine operators would conduct: (1) baseline sampling for miners 
who may be exposed to respirable crystalline silica at or above the 
proposed action level of 25 [mu]g/m\3\, (2) periodic sampling twice per 
year, and (3) annual evaluation of changing mining processes or 
conditions that would reasonably be expected to result in new or 
increased exposures. Under Alternative 2, the proposed PEL would be set 
at 25 [mu]g/m\3\; mine operators would install whatever controls are 
necessary to meet this PEL; and no action level would be proposed. 
Further, mine operators would: (1) not be required to conduct baseline 
sampling or periodic sampling, (2) conduct semi-annual evaluations of 
changing conditions, and (3) sample as frequently as necessary to 
determine the adequacy of controls. Additional detail on the two 
regulatory alternatives MSHA considered can be found in IX. Summary of 
Preliminary Regulatory Impact Analysis and Regulatory Alternatives and 
in the standalone PRIA document.
    MSHA believes the proposed rule would provide improved health 
protections for miners and would be achievable for all mines. In 
developing the proposed rule, MSHA has included flexibilities for 
operators in the implementation of updated respiratory protection 
standard, which would reduce the burden on small entities. MSHA has 
made the following determinations regarding the two alternatives 
considered:
     Alternative 1, ``Changes in Sampling and Evaluation 
Requirements,'' would reduce overall costs to the mining industry by 
26.2 percent, for costs calculated at both a 3 percent and 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 proposed rule) from 
0.12 percent to 0.09 percent.
     Alternative 2, ``Changes in Sampling and Evaluation 
Requirements and the Proposed PEL,'' would increase overall costs to 
the mining industry by 701.9 percent, for costs calculated at a 3 
percent discount rate, and by 930.2 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 proposed rule) from 
0.12 percent to 0.98 percent, based on a 3 percent discount rate, and 
from 0.12 percent to 1.259 percent based on a 7 percent discount rate.
    MSHA is seeking comments or additional information from 
stakeholders on whether there are alternatives the Agency should 
consider that would accomplish the objectives of this rulemaking while 
reducing the impact on small entities.
Conclusion
    MSHA estimated that small-entity controllers would be expected to 
incur, on average, additional regulatory costs equaling approximately 
0.122 percent of their revenues (or $1,220 for every $1 million in 
revenues).
    As required under the RFA, MSHA is complying with its obligation to 
consult with the SBA's Chief Counsel for Advocacy on this proposed rule 
and on this initial regulatory flexibility analysis. Consistent with 
Agency's practice, notes of any meetings with the Chief Counsel for 
Advocacy's office on this proposed rule, or any written communications, 
will be placed in the rulemaking record.

XI. Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3501-3521) provides 
for the Federal Government's collection, use,

[[Page 44952]]

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 
comply with this requirement, MSHA is publishing a notice of proposed 
collection of information in the proposed rule titled, Lowering Miners' 
Exposure to Respirable Crystalline Silica and Improving Respiratory 
Protection.
    This rulemaking would require the creation of a new information 
collection as well as modification to the burdens for 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.

I. New Information Collection Under Proposed Part 60, Respirable 
Crystalline Silica

    Under proposed part 60 entitled ``Respirable Crystalline Silica,'' 
some new burdens would apply to all mine operators, and other burdens 
would apply to only some mine operators. Below, the new information 
collection burden that would be created by proposed part 60 is 
discussed.
    Proposed Sec.  60.16 lists all the recordkeeping requirements 
related to proposed part 60. Each of the requirements are discussed 
below:
    Proposed Sec.  60.12 would require mine operators to make a record 
for each sampling and each evaluation conducted pursuant to this 
section. The sampling record would consist of the sample date, the 
occupations sampled, and the concentrations of respirable crystalline 
silica and respirable dust. The mine operator would also retain 
laboratory reports on sampling results. The semi-annual evaluation 
record would include the date of the evaluation and a record of the 
mine operator's evaluation of any changes in mining operations that may 
reasonably be expected to result in new or increased respirable 
crystalline silica exposures. In addition, the mine operator would be 
required to post the sampling and evaluation records and the laboratory 
report on the mine bulletin board and, if applicable, by electronic 
means, for the next 31 days, upon receipt. All records would be 
retained for at least 2 years from the date of each sampling or 
evaluation.
    Proposed Sec.  60.13 would require mine operators to make a record 
of corrective actions and the dates of the corrective actions. The 
corrective action records would be retained for at least 2 years from 
the date of each corrective action.
    Proposed Sec.  60.14 would require mine operators to retain a 
record of the written determination by a PLHCP that a miner who may be 
required to use a respirator is unable to wear a respirator. The 
written determination record would be retained for the duration of a 
miner's employment plus 6 months.
    Proposed Sec.  60.15 would require MNM mine operators to obtain a 
written medical opinion from the PLHCP or specialist within 30 days of 
a miner's medical examination. The written medical opinion would 
contain the date of the medical examination, a statement that the 
examination has met the requirements of this proposed section, and any 
recommended limitations on the miner's use of respirators. The written 
medical opinion record would be retained for the duration of a miner's 
employment plus 6 months.

II. Changes to Existing Information Collections

    This proposed rulemaking would result in non-substantive changes to 
existing information collection packages. One change under OMB Control 
Number 1219-0011 is to occur after 1219-0NEW, Respirable Crystalline 
Silica Standard, is approved by OMB. The other change is the 
discontinuance of the existing information collection package under OMB 
Control Number 1219-0048 which is also to occur after OMB approval of 
1219-0NEW, Respirable Crystalline Silica Standard.
    OMB Control Number 1219-0011, Respirable Coal Mine Dust Sampling, 
involves records for quarterly sampling of respirable dust in coal 
mines. The supporting statement references quartz and a reduced 
standard for respirable dust when quartz is present; however, there is 
no specific recordkeeping requirement that is associated with those 
references. Due to changes in the proposed rule, MSHA would make a non-
substantive change to the supporting statement by removing such 
references. However, there would be no changes in paperwork burden and 
costs in this information collection.
    OMB Control Number 1219-0048, Respirator Program Records, involves 
recordkeeping requirements under 30 CFR parts 56 and 57 for MNM mines 
when respiratory protection is used. MSHA is proposing to update the 
existing respiratory protection standard and permit mine operators to 
select the requirements of the standard that are applicable to their 
mines. This proposed change would eliminate the paperwork burden 
associated with respiratory protection resulting in the request to 
discontinue the existing information collection.

A. Solicitation of Comments

    Pursuant to the Paperwork Reduction Act, MSHA has prepared and 
submitted an information collection request (ICR) to OMB for the 
collection of information requirements identified in this proposed rule 
for OMB's review in accordance with 44 U.S.C. 3507(d). MSHA is 
soliciting comments concerning the proposed information collection 
related to respirable crystalline silica. MSHA is particularly 
interested in comments that:
     Evaluate whether the proposed collection of information is 
necessary for the proper performance of the functions of the agency, 
including whether the information will have practical utility;
     Evaluate the accuracy of the agency's estimate of the 
burden of the proposed collection of information, including the 
validity of the methodology and assumptions used;
     Suggest methods to enhance the quality, utility, and 
clarity of the information to be collected; and
     Minimize the burden of the collection of information on 
those who are to respond, including through the use of appropriate 
automated, electronic, mechanical, or other technological collection 
techniques or other forms of information technology (e.g., permitting 
electronic submission of responses).

B. Proposed Information Collection Requirements

    I. Type of Review: New Collection.
    OMB Control Number: 1219-0NEW.
    1. Title: Respirable Crystalline Silica Standard.
    2. Description of the ICR: The proposed rule on respirable 
crystalline silica contains collection of information requirements that 
would assist miners and mine operators in identifying exposures to 
respirable crystalline silica

[[Page 44953]]

in order to track actual and potential occupational exposure and action 
taken to control such exposure.
    There are provisions of this proposed rule that would take effect 
at different times after the implementation of this proposed rule, and 
there are provisions that would have different burden hours, burden 
costs, and responses each year. Therefore, MSHA shows the estimates of 
burden hours, burden costs, and responses in three separate years.
    3. Summary of the Collection of Information: Highlighted below are 
the key assumptions, by provision, used in the burden estimates in 
Table XI-1:
Proposed Sec.  60.12--Exposure Monitoring
    ICR. Proposed Sec.  60.12 would require mine operators to make a 
record for each baseline sampling, corrective action sampling, periodic 
sampling, semi-annual evaluation, and post-evaluation sampling, as 
previously described.
    Number of respondents. For proposed Sec.  60.12, the respondents 
would consist of all active mines because operators of active mines are 
assumed to perform baseline sampling and conduct semi-annual 
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) 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) would generate sampling 
and evaluation records.
    Annual number of responses. The estimated average annual number of 
responses would be 142,408, including 24,439 for baseline sampling, 
9,237 for sampling after corrective actions, 64,116 for periodic 
sampling, 42,103 for semi-annual evaluation recording and posting, and 
2,513 for post-evaluation sampling.
    MSHA assumes that all the active mines (12,631 mines) would conduct 
baseline sampling once in the first year. In succeeding years, about 
253 new mines would conduct baseline sampling with an average of 5.6 
samples per mine. The estimated number of periodic samplings is 
calculated based on the following factors: the number of miners with 
sampling results at or above the proposed action level (25 [mu]g/m\3\) 
but at or below the PEL (50 [mu]g/m\3\), the percent of miners needed 
for representative samples, and the number of quarters mines would be 
in operation. In year 1, MSHA expects the sampling to begin in the 
second half of the year, thereby decreasing the number of samples by 
half. As a result, MSHA estimates that an annual average of 64,116 
periodic samples would be conducted in the first three years. 
Furthermore, MSHA assumes that all 12,631 mines would record semi-
annual evaluation results twice a year--except in year 1, when it would 
be done once--and then post those results on a mine bulletin board, or 
if applicable, by electronic means. MSHA estimates mines would conduct 
sampling as a result of their semi-annual evaluations and an average of 
four miners would be sampled, resulting in an annual average of 2,513 
samples.
    MSHA estimates that about 22 percent of active mines (2,771 mines 
in total) would have at least one miner overexposed to respirable 
crystalline silica. MSHA further estimates that the 2,771 mines that 
would then conduct corrective action sampling for about four areas per 
mine. In year 1, they would sample in half as many areas.
    Estimated annual burden. The estimated average annual burden would 
be 31,392 hours, including 6,110 hours for baseline sampling, 2,309 for 
corrective action sampling, 16,029 hours for periodic sampling, 6,316 
hours for semi-annual evaluation recording and posting, and 628 hours 
for post-evaluation sampling. MSHA estimates that it would take 15 
minutes to record the sampling results, 15 minutes to record the 
results of a semi-annual evaluation, and 3 minutes to post each of the 
evaluation results on the mine bulletin board, and, if applicable, by 
electronic means.
Proposed Sec.  60.13--Corrective Actions
    ICR. Proposed Sec.  60.13 would require mine operators to make a 
record of corrective actions, as previously described.
    Number of respondents. For proposed Sec.  60.13, only those mines 
with at least one miner exposure above the proposed PEL are assumed to 
carry out the proposed requirement. MSHA estimates that about 22 
percent of active mines (2,771 mines in total) would have at least one 
miner overexposed to respirable crystalline silica.
    Annual number of responses. The estimated average annual number of 
responses would be 14,922, including 9,237 for corrective action 
records, and 5,685 for miner respirator records. MSHA estimates that 
the 2,771 mines that will be required to conduct and record corrective 
actions will do so for about four mine areas, except in year 1, when it 
would be done in half as many mine areas. MSHA further estimates this 
will affect 6,822 miners per year--except in year 1, when half as many 
miners would be affected--with each miner requiring a record of the 
miner being given access to a respirator until the corrective action is 
taken.
    Estimated annual burden. The estimated average annual burden would 
be 1,054 hours, including 769.7 for corrective action records and 284.3 
for miner respirator records. MSHA estimates that it takes five minutes 
to record a corrective action and the date. On average, it takes three 
minutes to note a miner's access to a respirator.
Proposed Sec.  60.14--Respiratory Protection
    ICR. Proposed Sec.  60.14 would require mine operators to retain a 
record of the determination by a PLHCP that a miner who may be required 
to use a respirator is unable to wear a respirator, as previously 
described.
    Number of respondents. For proposed Sec.  60.14, MSHA assumes that 
33 percent of mine operators would have their miners use respiratory 
protection as a temporary measure and keep records of their miners' 
ability to wear respirators. The number of respondents would be, on 
average, 603 mines per year, with each mine assumed to have at least 
some miners wearing respirators.
    Annual number of responses. The estimated annual number of 
responses would be 1,205, with an average of two miners for each of the 
603 mines.
    Estimated annual burden. The estimated annual burden would be 603 
hours. MSHA assumes it takes 30 minutes to record this information for 
about two miners for each of the 603 mines.
Proposed Sec.  60.15--Medical Surveillance for Mental and Nonmetal 
Miners
    ICR. Proposed Sec.  60.15 would require MNM mine operators to 
obtain a written medical opinion from a PLHCP or specialist regarding 
any recommended limitations on a miner's use of respirators, as 
previously described.
    Number of respondents. MSHA assumes that 75 percent of eligible MNM 
miners (current MNM miners), including contract workers, would make use 
of the opportunity to receive a voluntary medical exam that is paid by 
their mine operator. As a result, an average of 25,175 current miners 
are estimated to receive voluntary medical exams per year. This 
estimate represents the upper range of the participation rate of 
voluntary medical exams by miners. MSHA is using the upper end of the 
range to avoid underestimating compliance costs.
    MSHA further estimates that 8,392 miners in a given year, including 
contract workers, would be new miners and contractors who would undergo 
mandatory medical examinations.

[[Page 44954]]

MSHA estimated that the turnover of MNM miners would be 8,392 miners 
per year (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). The estimated total respondents per year therefore would be 
33,567 (= 8,392 + 25,175).
    Annual number of responses. The estimated annual number of 
responses would be 33,567, including 8,392 new miners and 25,175 
current miners.
    Estimated annual burden. The estimated annual burden would be 8,392 
hours, including 2,098 hours for new MNM miners and 6,294 hours for 
current miners. MSHA estimates it takes 15 minutes to record the 
medical examination results for each of the 33,567 miners.

Total Recordkeeping and Documentation Burden for Proposed Part 60
[GRAPHIC] [TIFF OMITTED] TP13JY23.048

    As shown in Table XI-1, the total number of respondents is 46,198: 
12,631 mines plus 33,567 miners; the estimated annual number of 
responses would be 192,102; and the estimated annual burden would be 
41,440 hours. These estimates are based on the conservative assumption 
that 75 percent of eligible current miners would take part in medical 
surveillance, which could overestimate the recordkeeping cost and 
burden. The following estimates of information collection burden are 
summarized in Table XI-2.
    1. Affected Public: Businesses or For-Profit.
    2. Estimated Number of Respondents: 47,456 respondents in the first 
year; 46,198 respondents in the second year; and 44,939 respondents in 
the third year.
    3. Frequency: On Occasion.
    4. Estimated Number of Responses: 192,990 responses in the first 
year; 197,021 responses in the second year; and 186,294 responses in 
the third year.
    5. Estimated Number of Burden Hours: 44,678 hours in the first 
year; 41,162 hours in the second year; and 38,480 hours in the third 
year.
    6. Estimated Hour Burden Costs: $2,843,901 in the first year; 
$2,558,724 in the second year; and $2,377,996 in the third year.
    7. Estimated Capital Costs to Respondents: $25,262 in each of the 
three years.
[GRAPHIC] [TIFF OMITTED] TP13JY23.049

    Most of the reduction in the number of responses and burden hours 
from the first year to the second year is a result of baseline sampling 
being carried out in all current mines in the first year

[[Page 44955]]

while only being carried out in new mines starting from the second 
year.
    For a detailed summary of the burden hours and related costs by 
provision, see the Preliminary Regulatory Impact Analysis (PRIA) 
accompanying the proposed rule. The PRIA includes the estimated costs 
and assumptions for the paperwork requirements related to this proposed 
rule.

C. Changes to Existing Information Collection Requirements

    I. Type of review: Non-substantive change to currently approved 
information collection.
    OMB Control Number: 1219-0011.
    1. Title: Respirable Coal Mine Dust Sampling.
    2. Description of the ICR:
Background
    In October 2022, MSHA received OMB approval for the reauthorization 
of the 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 is to revise the supporting 
statement for this information collection request due to the proposed 
PEL for respirable crystalline silica for all miners in this proposed 
rule. These proposed revisions would remove any reference in the 
information collection request to quartz or the reduction of the 
respirable dust standard due to the presence of quartz. This change 
does not modify the authority, affected mine operators, or paperwork 
burden.
    3. 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 rulemaking).
    Frequency: On occasion.
    Estimated Number of Responses: 995,102 (0 from this rulemaking).
    Estimated Number of Burden Hours: 58,259 (0 from this rulemaking).
    Estimated Hour Burden Costs: $3,271,611 ($0 from this rulemaking).
    Estimated Capital Costs to Respondents: $29,835 ($0 from this 
rulemaking).
    II. Type of Review: Discontinued information collection request.
    OMB Control Number: 1219-0048.
    1. Title: Respirator Program Records.
    2. 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. The proposed rule would incorporate 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 proposal would require mine operators' respiratory 
protection plans to include certain minimally acceptable program 
elements, but beyond that, would permit mine operators to select the 
requirements of ASTM F3387-19 that are applicable to their mines.
Summary of Changes
    The proposed rule would remove the paperwork burden associated with 
respiratory protection in the information collection request.
    3. Summary of the Collection of Information:
Changes in Burden
    MSHA has submitted a request to discontinue OMB Control Number 
1219-0048, eliminating all paperwork burden associated with the 
information collection request. It would discontinue upon the effective 
date of the final rule.
    Affected Public: Businesses or For-Profit.
    Estimated Number of Respondents: 0 (-350 from this rulemaking).
    Frequency: On occasion.
    Estimated Number of Responses: 0 (-630 from this rulemaking).
    Estimated Number of Burden Hours: 0 (-3,588 from this rulemaking).
    Estimated Hour Burden Costs: $0 (-$284,084 from this rulemaking).
    Estimated Capital Costs to Respondents: $0 (-$140,000 from this 
rulemaking).

D. Submitting Comments

    The information collection package for this proposal has been 
submitted to OMB for review under 44 U.S.C. 3506(c) of the Paperwork 
Reduction Act of 1995, as amended. Comments on the information 
collection requirements should be sent to MSHA by one of the methods 
previously explained in the DATES section of this preamble.
    The information collection request will be available on http://www.regulations.gov. MSHA cautions the commenter against providing any 
information in the submission that should not be publicly disclosed. 
Full comments, including personal information provided, will be made 
available on www.regulations.gov and www.reginfo.gov.
    The public may also examine publicly available documents at the 
Mine Safety and Health Administration, 201 12th South, Suite 4E401, 
Arlington, VA 22202-5450. Sign in at the receptionist's desk on the 4th 
floor via the East elevator. Before visiting MSHA in person, call 202-
693-9440 to make an appointment and determine if any special health 
precautions are required in keeping with the Department of Labor's 
COVID-19 policy.
    Questions about the information collection requirements may be 
directed to the contact person listed in the FOR FURTHER INFORMATION 
CONTACT section of this preamble.

E. Docket and Inquiries

    Those wishing to download comments and other materials relating to 
paperwork determinations should use the procedures described in this 
preamble. One may also obtain a copy of this ICR by going to http://www.reginfo.gov/public/do/PRAMain, clicking on ``Currently under 
Review--Open for Public Comments'' and scrolling down to ``Department 
of Labor.''
    A Federal agency cannot conduct or sponsor a collection of 
information unless it is approved by OMB under the Paperwork Reduction 
Act and displays a currently valid OMB control number. The public is 
not required to respond to a collection of information unless the 
collection of information displays a currently valid OMB control 
number.

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 proposed 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 proposed rule will

[[Page 44956]]

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 has reviewed the proposed rule under the Unfunded Mandates 
Reform Act of 1995 (2 U.S.C. 1501 et seq.). The Unfunded Mandates 
Reform Act requires Federal agencies to assess the effects of their 
discretionary regulatory actions. In particular, the Act addresses 
actions that may result in the expenditure by State, local, and Tribal 
governments, in the aggregate, or by the private sector, of $100 
million or more (adjusted annually for inflation) in any 1 year (5 
U.S.C. 1532(a)). MSHA has determined that this proposed rule does not 
result in such an expenditure. Accordingly, the Unfunded Mandates 
Reform Act requires no further Agency action or analysis.

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 
proposed 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 proposed rule 
impacts the mine industry and does not impose requirements on states or 
families. Accordingly, MSHA certifies that this proposed 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 proposed 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 proposed rule was written to provide a clear legal standard for 
affected conduct and was carefully reviewed to eliminate drafting 
errors and ambiguities so as to minimize litigation and avoid undue 
burden on the Federal court system. Accordingly, the proposed 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, ``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 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 
proposed 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 proposed 
rule would lower the occupational exposure limit to respirable 
crystalline silica for all 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 all airborne hazards.
    MSHA is aware of studies which have characterized and assessed the 
risks posed by ``take-home'' exposure pathways for hazardous dust 
particles. However, the proposed 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, operators' policies and procedures, and 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 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 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 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 in 
to 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 
invites comment on the identification of any other scientific or 
academic study or information that evaluates the potential association 
between paternal exposure to respirable crystalline silica and 
childhood leukemia during the NPRM's public comment period.
    MSHA also invites comment on the identification of any scientific 
or academic study or information that evaluates the potential risks to 
female workers who are exposed to respirable crystalline silica during 
pregnancy.
    MSHA has no evidence that the environmental health or safety risks 
posed by respirable crystalline silica,

[[Page 44957]]

including ``take-home'' exposure to respirable crystalline silica, 
disproportionately affect children. Therefore, MSHA preliminarily 
concludes no further analysis or action is needed, in accordance with 
E.O. 13045.

G. Executive Order 13132: Federalism

    MSHA has determined that the proposed 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 proposed 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 proposal for its impact on the supply, distribution, and 
use of energy because it applies to the mining industry. The proposed 
rule would result in annualized compliance costs of $4.85 million using 
a 3 percent real discount rate and $4.97 million using a 7 percent real 
discount rate for the coal mine industry relative to annual revenue of 
$27.03 billion. The proposal would also result in annualized compliance 
costs of $54.23 million using a 3 percent real discount rate and $55.72 
million using a 7 percent real discount rate for the metal/nonmetal 
mine industry relative to annual revenue of $88.32 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 proposed 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. Initial 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 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 proposed 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.\71\ 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.
---------------------------------------------------------------------------

    \71\ 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.\72\ 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,\73\ 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.
---------------------------------------------------------------------------

    \72\ 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.
    \73\ This is a simple average rather than a weighted average by 
population.
---------------------------------------------------------------------------

    The proposed rule would lower exposure to respirable crystalline 
silica and improve respiratory protection for all mine workers. MSHA 
determined that the proposed 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.
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BILLING CODE 4520-43-C

L. Availability of Materials To Be Incorporated 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 
it proposes to incorporate by reference are reasonably available to 
interested parties or how it 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).
    In accordance with the OFR's requirements, MSHA provides in 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 during 
the comment period and upon finalization of the rule.
    ASTM F3387-19, ``Standard Practice for Respiratory Protection'' 
(ASTM F3387-19) 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 research and rulemaking on respiratory protection. The 
proposed rule would incorporate by reference ASTM F3387-19 in existing 
Sec. Sec.  56.5005, 57.5005, and 72.710 and in proposed Sec.  
60.14(c)(2) to better protect all miners from airborne hazards. MSHA 
believes that incorporating by reference ASTM F3387-19 would provide 
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 proposed update to the Agency's 
existing respiratory protection standard, please see section VII.C of 
this preamble, Updating MSHA Respiratory Protection Standards by 
Incorporating by Reference ASTM F3387-19.
    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, PO Box C700, West Conshohocken, 
PA 19428-2959; https://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, https://www.astm.org/products-services/reading-room.html. During the comment period, a read-only version of 
ASTM F3387-19 will be made available free of charge.\74\
---------------------------------------------------------------------------

    \74\ The read-only version of ASTM F3387-19 available for public 
review during the comment period can be accessed using the following 
link--https://tinyurl.com/mwk97hjn.
---------------------------------------------------------------------------

    In addition, during the comment period and 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).
    ISO 7708:1995: 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 proposed rule would incorporate 
by reference ISO 7708:1995 in proposed Sec.  60.12(f)(4) to ensure 
consistent sampling collection by mine operators through the 
utilization of samplers conforming to ISO 7708:1995.
    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, during the comment period and 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).
    TLV's Threshold Limit Values for Chemical Substances in Workroom 
Air Adopted by ACGIH for 1973.
    This material is referenced in the amendatory text of this document 
but has already been approved for appendix A. No changes are proposed.

XIII. References Cited in the Preamble

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an ongoing epidemic of accelerated silicosis in oilfield 
sandblasters: Lung pathology and mineralogy. Annals of Occupational. 
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Agency for Toxic Substances and Disease Registry (ATSDR). 2019. 
Toxicological profile for silica. U.S. Department of Health and 
Human Services, Centers for Disease Control and Prevention, Division 
of Toxicology and Human Health Sciences, Atlanta, GA.
Almberg, K.S., Friedman, L.S., Rose, C.S., Go, L.H.T., Cohen, R.A. 
2020. Progression of coal workers' pneumoconiosis absent further 
exposure. Occupational and Environmental Medicine. 77:748-751.
Almberg, K.S., Halldin, C.N., Blackley, D.J., Laney, A.S., Storey, 
E., Rose, C.S., Go, L.H.T. and Cohen, R.A. 2018a. Progressive 
massive fibrosis resurgence identified in U.S. coal miners filing 
for black lung benefits, 1970-2016. Annals of American Thoracic 
Society. 15(12): 1420-1426.
Am. Fuel & Petrochemical Manufacturers v. Env't Prot. Agency, 3 
F.4th 373, 384 (D.C. Cir. 2021).
American Conference of Governmental Industrial Hygienists (ACGIH) 
2022. TLV chemical substances introduction. https://www.acgih.org/science/tlv-bei-guidelines/tlv-chemical-substances-introduction/.
American Conference of Governmental Industrial Hygienists (ACGIH). 
2010: Silica, crystalline: [alpha]-Quartz and cristobalite. 
Documentation of TLV Recommendation. Cincinnati, Ohio.
American Conference of Governmental Industrial Hygienists (ACGIH). 
TLVs[supreg] Threshold limit values for chemical substances in 
workroom air adopted by the American Conference of Government 
Industrial Hygienists for 1973. Journal of Occupational Medicine. 
1974; 16(1):39-49 PMID: 4814108.
American Iron and Steel Institute et al., v. Occupational Safety and 
Health Administration, 577 F.2d 825 (3d Cir. 1978).
American Society of Testing and Materials (ASTM). 2019. Standard 
practice for respiratory protection. F3387-19. West Conshohocken, 
PA.
American Thoracic Society (ATS). 2010a. Breathing in America: 
Diseases, progress, and hope. Ed: D.E. Schraufnagel. American 
Thoracic Society. 282 pages.
American Thoracic Society (ATS). 2010b. An official American 
Thoracic Society public policy statement: Novel risk factors and the 
global burden of chronic obstructive pulmonary disease. By: Eisner 
M.D., Anthonisen, N., Coultas, D., Kuenzli, N., Perez-Padilla, R., 
Postma, D., Romieu, I., Silverman, E.K., and Balmes, J.R. American 
Journal of Respiratory and Critical Care Medicine. 182:693-718.

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American Thoracic Society (ATS). 1997. Adverse effects of 
crystalline silica exposure. Committee members Beckett W., Abraham, 
J., Becklake M., et al. American Journal of Respiratory Critical 
Care Medicine. 155:761-768.
Ant[atilde]o, V.C., Petsonk, E.L., Sokolow, L.Z., Wolfe, A.L., 
Pinheiro, G.A., Attfield, M.D., 2005. Rapidly progressive coal 
workers' pneumoconiosis in the United States: geographic clustering 
and other factors. Occup Environ Med. 62(10):670-4.
Attfield, M. and Costello, J. 2004. Quantitative exposure-response 
for silica dust and lung cancer in Vermont granite workers. American 
Journal of Industrial Medicine. 45:129-138.
Attfield, M.D. and Kuempel, E.D. 2008. Mortality among U.S. 
underground coal miners, a 23- year follow-up. American Journal of 
Industrial Medicine. 51(4):231-245.
Attfield, M.D., Vallyathan, V., and Green, F.H.Y. 1994. Radiographic 
appearances of small opacities and their correlation with pathology 
grading of macules, nodules and dust burden in the lungs. Annals of 
Occupational Hygiene. 38(Suppl. 1):783-789.
Balaan, M.R. and Banks, D.E. 1998. Silicosis. In: Rom W.N., ed. 
Environmental and Occupational Medicine, Third Edition. 435-448.
Banks, D.E. 2005. Silicosis. In: Rosenstock L., M.R. Cullen, C.A. 
Brodkin, and C.A. Redlich, eds. Textbook of Clinical Occupational 
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Saunders. Pages 380-392.
Barnes, H., Goh, N.L., Leong, T.L., and Hoy, R. 2019. Silica-
associated lung disease: An old- world exposure in modern 
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Becklake, MR. 1994. Pneumoconioses. In: Murray J.F. and J.A. Nadel, 
eds. Textbook of Respiratory Medicine. Second edition. Philadelphia, 
PA. W.B. Saunders Co. Pages 1955-2001.
Becklake, M.R., Irwig, L., Kielowski, D., Webster, I., DeBeer, M., 
and Landau, S. 1987. The predictors of emphysema in South African 
gold miners. American Review of Respiratory Disease. 135:1234-1241.
B[eacute]gin, R., Filion, R., and Ostiguy, G. 1995. Emphysema in 
silica- and asbestos-exposed workers seeking compensation. A CT scan 
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B[eacute]gin, R., Bergeron, D., Samson, L., Boctor, M., Cantin, A. 
1987. CT assessment of silicosis in exposed workers. American 
Journal of Roentgenology. 148(3):509-14. doi: 10.2214/ajr.148.3.509. 
PMID: 3492877.
Benmerzoug, S., Rose, S., Bounab, B., Gosset, D., Duneau, L., 
Chenuet, P., Mollet, L., Le Bert, M., Lambers, C., Geleff, S., Roth, 
M., Fauconnier, L., Sedda, D., Carvalho, C., Perche, O., Laurenceau, 
D., Ryffel, B., Apetoh, L., Kiziltunc, A., Uslu1, H., Albez, FS., 
Akgun, M., Togbe, D., Quesniaux, VFJ. 2018. STING-dependent sensing 
of self-DNA drives silica-induced lung inflammation. Nature 
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Blackley, D., Reynolds, L., Short, C., Carson, R., Storey, E., 
Halldin, C.N. and Laney, A.S. 2018b. Research letter: Progressive 
massive fibrosis in coal miners from 3 clinics in Virginia. Journal 
of the American Medical Association.
Blackley, D., Halldin, C., Cohen, R., Cummings, K., Storey, E., 
Laney, S. 2017. Misclassification of occupational disease in lung 
transplant recipients. J Heart Lung Transplant. 36(5):588-590.
Blackley, D., Halldin, C., and Laney, A. 2016b. Resurgence of 
progressive massive fibrosis in coal miners--Eastern Kentucky, 2016. 
Morbidity and Mortality Weekly Report. 65(49):1385-9.
Blackley, D.J., Laney, A.S., Halldin, C.N., Cohen R.A. 2015. 
Profusion of opacities in simple coal workers pneumoconiosis is 
associated with reduced lung function. Official Publication of the 
American Chest Physicians. 148(5):1293-1299.
Borm, P.J.A. and Driscoll, K. 1996. Particles, inflammation and 
respiratory tract carcinogenesis. Toxicology Letters 88:109-113.
Brief and Scala, 1986. Occupational health aspects of unusual work 
schedules: A review of Exxon's experiences. Am. Ind. Hyg. Assoc. J. 
47 (4): 199-202.
Brown, T. 2009. Silica exposure, smoking, silicosis and lung 
cancer--complex interactions. Occupational Medicine. 59:89-95.
Brown, G.M., and Donaldson, K. 1996. Modulation of quartz toxicity 
by aluminum. In: Castranova V, V. Vallyathan, and W.E. Wallace, eds. 
Silica and Silica-Induced Lung Diseases. Boca Raton, FL: CRC Press, 
Inc. Pages 299-304.
Buchanan, D., Miller, B.G., and Soutar, C.A.. 2003. Quantitative 
relations between exposure to respirable quartz and risk of 
silicosis. Occupational and Environmental Medicine. 60:159-164.
Bureau of Labor Statistics (BLS), Quarterly Employment and Wages 
First Quarter 2022 (2022); Bureau of Economic Analysis, Personal 
Income by County, Metro, and Other Areas 2020 (2020); U.S. Census 
Bureau, ``Annual Estimates of the Resident Population for Counties: 
April 1, 2020 to July 1, 2021 (CO-EST2021-POP)''
Calvert, G., Rice, F. L., Boiano, J. M., Sheehy, J. W., Sanderson, 
W. T.. 2003. Occupational silica exposure and risk of various 
diseases: an analysis using death certificates from 27 states of the 
United States. Occupational and Environmental Medicine. 60:122-129.
Calvert, G.M., Steenland, K., and Palu, S. 1997. End-stage renal 
disease among silica-exposed gold miners: A new method for assessing 
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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 rulemaking. The Mine Safety and Health 
Administration (MSHA) collected these samples from metal/nonmetal 
(MNM) and coal mines and analyzed the data to support this 
rulemaking. Technical details are discussed in the following 
attachments.

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.\75\ 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'').
---------------------------------------------------------------------------

    \75\ 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.
---------------------------------------------------------------------------

    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 \76\ and are assigned by the MSHA Laboratory 
based on sample type and analysis results. The codes link 
information, such as contaminant description, permissible exposure 
limit (PEL), and the units of measure for each contaminant sampled.
---------------------------------------------------------------------------

    \76\ 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.
BILLING CODE 4520-43-P
[GRAPHIC] [TIFF OMITTED] TP13JY23.052

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). Those MNM respirable dust 
samples with a mass of at least 0.100 mg are analyzed and contained 
in MSIS. MSIS and MDRS differ from LIMS in that some of the fields 
associated with a sample can be modified or corrected by the 
inspector. These correctable fields include Mine ID, Location Code, 
and Job Code. Inspectors cannot access or modify the fields in the 
LIMS database.

[[Page 44971]]

    From the database, 55 samples \77\ were removed because they 
were erroneous, had an incorrect flow rate, had insufficient 
sampling time, or were duplicated. This resulted in a final dataset 
of 57,769 MNM samples that contained a mass of at least 0.100 mg of 
respirable dust. Datasets containing the analyzed samples that MSHA 
removed and retained can be found in the rulemaking docket MSHA-
2023-0001.
---------------------------------------------------------------------------

    \77\ 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 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 \78\ 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. Datasets containing the unanalyzed samples 
that MSHA removed and retained can be found in the rulemaking docket 
MSHA-2023-0001.
---------------------------------------------------------------------------

    \78\ 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 for 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.
[GRAPHIC] [TIFF OMITTED] TP13JY23.053

BILLING CODE 4520-43-C

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.\79\ For coal mines, the analysis is 
based on samples collected by inspectors beginning on August 1, 
2016, when Phase III of MSHA's 2014 respirable coal mine dust (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.
---------------------------------------------------------------------------

    \79\ 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

[[Page 44972]]

were not. Respirable dust samples from coal mines contain the 
records 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 designated for sampling 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.
     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.\80\ From those 67,963 samples, 4,836 samples were removed as 
they were environmental samples, voided in MSIS, or had other 
errors.\81\ This resulted in a dataset of 63,127 samples from coal 
mines that were analyzed for respirable crystalline silica. Datasets 
containing the analyzed samples that MSHA removed and retained can 
be found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------

    \80\ 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 Mine ID, Location Code, and Job Code.
    \81\ 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.\82\ After removing 13,243 \83\ samples that were 
environmental samples, erroneous, or had voided controls, there were 
32,401 samples that were not analyzed for respirable crystalline 
silica. Datasets containing the unanalyzed samples that MSHA removed 
and retained can be found in the rulemaking docket MSHA-2023-0001.
---------------------------------------------------------------------------

    \82\ 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.
    \83\ 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 82). 
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.\84\ A breakdown 
of respirable dust samples from coal mines is included in Table A-3.
---------------------------------------------------------------------------

    \84\ 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.
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[GRAPHIC] [TIFF OMITTED] TP13JY23.054

Attachment 1. MNM Samples Analyzed for Cristobalite

    Cristobalite is one of the three polymorphs of respirable 
crystalline silica analyzed by MSHA's Laboratory upon request that 
is included in this proposed rule. At the request of the inspector, 
MNM \85\ 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.\86\
---------------------------------------------------------------------------

    \85\ See Attachment 2. Technical Background about Measuring 
Respirable Crystalline Silica, for more information.
    \86\ See Attachment 2. Technical Background about Measuring 
Respirable Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TP13JY23.055

    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.

[[Page 44974]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.056

    The distribution of the 359 samples by cristobalite mass can be 
seen in Table A1-3.\87\
---------------------------------------------------------------------------

    \87\ 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 [micro]g. As such these samples 
were assigned a value of 5 [micro]g of cristobalite, one half the 
LOD. See Attachment 2. Technical Background about Measuring 
Respirable Crystalline Silica, for more information.
[GRAPHIC] [TIFF OMITTED] TP13JY23.057

    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 [micro]g/m\3\ to 53 [micro]g/m\3\.\88\
---------------------------------------------------------------------------

    \88\ One sample had a cristobalite concentration of 53 [micro]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] TP13JY23.058


[[Page 44975]]


BILLING CODE 4520-43-C

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 mine 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 2020). 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 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 the method 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 2020). 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, if no quartz is detected by XRD 
analysis for an MNM sample, the method LOD is 5 [micro]g. If 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 a sample having respirable crystalline silica mass 
below the method LOD would be 6 [micro]g/m\3\ (= 5 [micro]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 [micro]g/m\3\ (= \1/2\ * 6 [micro]g/m\3\) 
in this example.
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[[Page 44976]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.059

    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 
in 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. Samples from Shop Welders (code 319) are never 
analyzed for quartz, as they instead are sent for welding fume 
analysis.
    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 [micro]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.\89\
---------------------------------------------------------------------------

    \89\ 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 [micro]g was not disputed in the [rulemaking] 
record.'' (OSHA, 2016).

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

[[Page 44977]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.060

    The reported value of respirable crystalline silica mass from an 
MNM or coal sample can fall under one of the 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 [mu]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 mg

    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 mg

    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 44978]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.061

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\ mass 
LOD 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. 2020. 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 rulemaking analysis, 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 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.

[[Page 44979]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.062

[GRAPHIC] [TIFF OMITTED] TP13JY23.063

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 current rulemaking. MSHA has developed respirable 
crystalline silica exposure profile tables using its inspectors' 
sampling data and results. One set of exposure profile tables 
displays the analysis of 15 years of respirable crystalline silica 
sampling data from MNM mines (Attachment 1), and the other set 
displays the analysis of 5 years of respirable crystalline silica 
samples collected at coal mines (Attachment 2).\90\ 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.).
---------------------------------------------------------------------------

    \90\ 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.\91\ Following the 
sampling strategy outlined in the most recent

[[Page 44980]]

MSHA Health Inspection Procedures Handbook (December 2020; PH20-V-
4), the inspectors determine potential airborne hazards 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.
---------------------------------------------------------------------------

    \91\ 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 include 
the 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. For example, 
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. An example is 
presented below in Table C-1. 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.
[GRAPHIC] [TIFF OMITTED] TP13JY23.064

    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. In 2020, MSHA's 
Laboratory 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 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.\92\ 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:
---------------------------------------------------------------------------

    \92\ 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

[[Page 44981]]

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 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.''
[GRAPHIC] [TIFF OMITTED] TP13JY23.065

    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 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.

[[Page 44982]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.066

    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.\93\ 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.
---------------------------------------------------------------------------

    \93\ 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.
---------------------------------------------------------------------------

Attachment 1: Tables for MNM

[[Page 44983]]

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[[Page 44984]]


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[[Page 44985]]


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[[Page 44986]]


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[[Page 44987]]


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[[Page 44988]]


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[[Page 44989]]


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[[Page 44990]]


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[[Page 44991]]


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[[Page 44992]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.076


[[Page 44993]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.077

Attachment 2: Tables for Coal

[[Page 44994]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.078


[[Page 44995]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.079


[[Page 44996]]


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[[Page 44997]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.081


[[Page 44998]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.082


[[Page 44999]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.083


[[Page 45000]]



Attachment 3: Coal Job Codes

    The complete list of job codes that are found in IAS, as of 
March 11, 2022, are included below, with Table C3-1 listing job 
codes for coal miners. For coal, the first digit of the job code 
identifies where the work is taking place. For example, codes 
starting with 0 represent jobs that occur at the underground face of 
the mine. Job codes that start with 6 were added in 2020.

0--Underground Section Workers (Face)
1--General Underground (Non-Face)
2--Underground Transportation (Non-Face)
3--Surface
4--Supervisory and Staff
5--MSHA--State
6--Shaft and Slope Sinking
[GRAPHIC] [TIFF OMITTED] TP13JY23.084


[[Page 45001]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.085


[[Page 45002]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.086


[[Page 45003]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.087

Attachment 4: MNM Job Codes

    The complete list of job codes that are found in IAS, as of 
March 11, 2022, are included below with Table C4-1 outlining job 
codes for MNM miners.

[[Page 45004]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.088


[[Page 45005]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.089


[[Page 45006]]



Attachment 5. Examples of Job Code Pocket Cards

    Inspectors previously received pocket-sized job code cards for 
use in filling out forms with the correct job code. Now, a drop-down 
menu in IAS is used to select the codes. Table C5-1 contains 
Underground Coal Mining Occupation Codes from Coal Job Code Cards 
used by MESA between 1973 and 1977. Table C5-2 contains Surface 
Occupation Codes from Coal Job Codes used by MESA between 1973 and 
1977.
[GRAPHIC] [TIFF OMITTED] TP13JY23.090


[[Page 45007]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.091

[GRAPHIC] [TIFF OMITTED] TP13JY23.092


[[Page 45008]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.093

MNM Job Code Cards (1997)

    Table C5-3 includes MNM Job Codes from a MNM Job Code Card 
printed in 1997 by the GPO and which referenced a 1981 MSHA form 
(MSHA Form 4000-50, Sept. 1981).

[[Page 45009]]

[GRAPHIC] [TIFF OMITTED] TP13JY23.094


[[Page 45010]]


[GRAPHIC] [TIFF OMITTED] TP13JY23.095

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.

[[Page 45011]]

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 proposing to amend 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 paragraph (a) to read as follows:


Sec.  56.5001  Exposure limits for airborne contaminants.

* * * * *
    (a) 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 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 MSHA 
Metal and Nonmetal Mine Safety and Health District Office. For 
information on the availability of this material at NARA, visit 
www.archives.gov/federal-register/cfr/ibr-locations.html 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.
* * * * *
0
3. Amend Sec.  56.5005 by revising the introductory text and paragraphs 
(b) and (c) to read as follows:


Sec.  56.5005  Control of exposure to airborne contaminants.

    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:
* * * * *
    (b) Approved respirators shall be selected, fitted, cleaned, used, 
and maintained in accordance with the requirements, as applicable, 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 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.html 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.

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

0
4. 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
5. Amend Sec.  57.5001 by revising paragraph (a) to read as follows:


Sec.  57.5001  Exposure limits for airborne contaminants.

* * * * *
    (a) 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. Excursions above the listed thresholds shall not be of a 
greater magnitude than is characterized as permissible by the 
Conference. 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 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 MSHA Metal 
and Nonmetal Mine Safety and Health District Office. For information on 
the availability of this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email 
[email protected]. The material may be obtained from American 
Conference of Governmental Industrial Hygienists by writing to 1330 
Kemper Meadow Drive, Attn: Customer Service, Cincinnati, OH 45240; 
www.acgih.org.
* * * * *
0
6. Amend Sec.  57.5005 by revising the introductory text and paragraphs 
(b) and (c) to read as follows:


Sec.  57.5005  Control of exposure to airborne contaminants.

    Control of employee exposure to harmful airborne contaminants shall 
be, insofar as feasible, by prevention of contamination, removal by 
exhaust

[[Page 45012]]

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:
* * * * *
    (b) Approved respirators shall be selected, fitted, cleaned, used, 
and maintained in accordance with the requirements, as applicable, 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 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.html 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.

Subchapter M-Uniform Mine Health Regulations

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

PART 60-RESPIRABLE CRYSTALLINE SILICA

Sec.
60.1 Scope; effective date.
60.2 Definitions.
60.10 Permissible exposure limit (PEL).
60.11 Methods of compliance.
60.12 Exposure monitoring.
60.13 Corrective actions.
60.14 Respiratory protection.
60.15 Medical surveillance for metal and nonmetal miners.
60.16 Recordkeeping requirements.
60.17 Severability.

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


Sec.  60.1  Scope; effective date.

    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 miners are also included. 
The provisions of this part are effective [date 120 days after 
publication of the final rule].


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).
    Objective data means 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.
    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) Baseline sampling. (1) The mine operator shall perform baseline 
sampling within the first 180 days after [date 120 days after 
publication of the final rule] 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) The mine operator is not required to conduct periodic sampling 
under paragraph (b) of this section if the baseline sampling indicates 
that miner exposures are below the action level and if the conditions 
in either paragraph (a)(2)(i) or (ii) of this section are met:
    (i) One of the following sources from within the preceding 12 
months of baseline sampling indicates that miner exposures are below 
the action level:
    (A) Sampling conducted by the Secretary; or
    (B) Mine operator sampling conducted in accordance with paragraphs 
(f) and (g) of this section; or
    (C) Objective data.
    (ii) Subsequent sampling that is conducted within 3 months after 
the baseline sampling indicates that miner exposures are below the 
action level.
    (b) Periodic sampling. 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 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.
    (c) Corrective actions sampling. Where the most recent sampling 
indicates that miner exposures are above the PEL, the mine operator 
shall sample after corrective actions taken pursuant to Sec.  60.13 
until the sampling indicates that miner exposures are at or below the 
PEL.
    (d) Semi-annual evaluation. At least every 6 months after [date one 
year after the effective date of the final rule], mine operators shall 
evaluate any changes in

[[Page 45013]]

production, processes, engineering or administrative controls, or other 
factors that 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 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.
    (e) Post-evaluation sampling. If the mine operator determines as a 
result of the semi-annual evaluation under paragraph (d) 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.
    (f) Sampling requirements. (1) Sampling shall be performed for the 
duration of a miner's regular full shift and during typical mining 
activities.
    (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) or (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 to determine compliance with the 
PEL. ISO 7708:1995, Air Quality--Particle Size Fraction Definitions for 
Health-Related Sampling, Edition 1, 1995-04, 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 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.html or email 
[email protected]. The material may be obtained from the 
International Organization for 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.
    (g) 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).
    (h) 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;
    (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.
    (4) Once corrective actions have been taken, the mine operator 
shall:
    (i) Conduct sampling pursuant to Sec.  60.12(c); and
    (ii) Take additional or new corrective actions until sampling 
indicates miner exposures are at or below the PEL.
    (b) 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 non-routine use of respirators. The mine operator 
shall use respiratory protection as a temporary measure in accordance 
with paragraph (c) of this section. Miners must use respirators when 
working 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.
    (b) Miners unable to wear respirators. 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 non-routine use of 
respirators under paragraph (a) of this section is no longer required.
    (c) Respiratory protection requirements. (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) Approved respirators shall be selected, fitted, used, and 
maintained in accordance with the requirements, as applicable, 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 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

[[Page 45014]]

this material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from ASTM International, 100 Barr Harbor Drive, PO Box C700, 
West Conshohocken, PA 19428-2959; www.astm.org/.


Sec.  60.15  Medical surveillance for metal and nonmetal miners.

    (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.
    (b) Voluntary medical examinations. Each mine operator shall 
provide the opportunity to have the medical examinations specified in 
paragraph (a) of this section at least every 5 years to all miners 
employed at the mine. 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 30 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. The results of medical 
examinations or tests made pursuant to this section shall be provided 
only to the miner, and at the request of the miner, to the miner's 
designated physician.
    (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(d) shall be retained 
for at least 2 years from the date of each evaluation.
    (2) Sampling records made under Sec.  60.12(h) shall be retained 
for at least 2 years from the sample date.
    (3) Corrective action records made under Sec.  60.13(b) shall be 
retained for at least 2 years from the date of each corrective action. 
These records must be stored with the records of related sampling under 
Sec.  60.12(h).
    (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
------------------------------------------------------------------------
             Record               Section references   Retention period
------------------------------------------------------------------------
1. Evaluation records...........  Sec.   60.12(d)...  At least 2 years
                                                       from date of each
                                                       evaluation.
2. Sampling records.............  Sec.   60.12(h)...  At least 2 years
                                                       from sample date.
3. Corrective action records....  Sec.   60.13(b)...  At least 2 years
                                                       from date of each
                                                       corrective
                                                       action.
4. Written determination records  Sec.   60.14(b)...  Duration of
 received from a PLHCP.                                miner's
                                                       employment plus 6
                                                       months.
5. Written medical opinion        Sec.   60.15(f)...  Duration of
 records received from a PLHCP                         miner's
 or specialist.                                        employment plus 6
                                                       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

[[Page 45015]]

sections and shall not affect the remainder thereof.

Subchapter O--Coal Mine Safety and Health

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

0
8. 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
9. Amend Sec.  70.2 by removing the definition of ``Quartz''.

Subpart B--Dust Standards


Sec.  70.101  [Removed and Reserved]

0
10. Remove and reserve Sec.  70.101.

Subpart C--Sampling Procedures

0
11. Amend Sec.  70.205 by revising paragraph (c) to read as follows:


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

* * * * *
    (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.  70.206  [Removed and Reserved]

0
12. Remove and reserve Sec.  70.206.


Sec.  70.207  [Removed and Reserved]

0
13. Remove and reserve Sec.  70.207.
0
14. Amend Sec.  70.208 by:
0
a. Removing and reserving paragraph (c);
0
b. Revising paragraphs (d), (e) introductory text, (e)(2), (f), (g), 
(h) introductory text, (h)(2), (i) introductory text, and (i)(1); and
0
c. Adding table 1.
    The revisions and addition read as follows:


Sec.  70.208  Quarterly sampling; mechanized mining units.

* * * * *
    (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 occupation.
    (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:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to at or below the respirable dust standard; and
* * * * *
    (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 (h) and (i) of 
this section.
    (h) Upon issuance of a citation for violation of the standard, the 
operator shall take the following actions sequentially:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
* * * * *
    (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
* * * * *

 Table 1 to Sec.   70.208--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).................................  70.100(a)--Single sample...........            1.79            1.70
                                             70.100(b)--Single sample...........            0.74            0.57
70.208(f)(1)...............................  70.100(a)--3 or more samples.......            1.79            1.70
                                             70.100(b)--3 or more samples.......            0.74            0.57
70.208(f)(2)...............................  70.100(a)--5 sample average........            1.63            1.59
                                             70.100(b)--5 sample average........            0.61            0.53
70.208(f)(2)...............................  70.100(a)--15 sample average.......            1.58            1.56
                                             70.100(b)--15 sample average.......            0.57            0.52
70.208(i)(1)...............................  70.100(a)--Each of 5 samples.......            1.79            1.70
                                             70.100(b)--Each of 5 samples.......            0.74            0.57
----------------------------------------------------------------------------------------------------------------

0
15. Amend Sec.  70.209 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f) 
introductory text, (f)(2), (g) introductory text, and (g)(1); and
0
c. Adding table 1.
    The revisions and addition read as follows:

[[Page 45016]]

Sec.  70.209  Quarterly sampling; designated areas.

* * * * *
    (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:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to at or below the respirable dust standard; and
* * * * *
    (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 DA until the violation is 
abated and the citation is terminated in accordance with paragraphs (f) 
and (g) of this section.
    (f) Upon issuance of a citation for a violation of the standard, 
the operator shall take the following actions sequentially:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
* * * * *
    (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
* * * * *

  Table 1 to Sec.   70.209--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
----------------------------------------------------------------------------------------------------------------

Table 70--1 to Subpart C of Part 70 [Removed]

0
16. Remove table 70-1 to subpart C of part 70.

Table 70--2 to Subpart C of Part 70 [Removed]

0
17. Remove table 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
18. 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
19. Amend Sec.  71.2 by removing the definition of ``Quartz''.

Subpart B--Dust Standards


Sec.  71.101  [Removed and Reserved]

0
20. Remove and reserve Sec.  71.101.

Subpart C--Sampling Procedures

0
21. Amend Sec.  71.205 by revising paragraph (c) to read as follows:


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

* * * * *
    (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.
0
22. Amend Sec.  71.206 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (e), (g), (h) introductory text, (h)(2), (i), 
(j), (k) introductory text, (k)(2), and (l);
0
c. Removing tables 71-1 and 71-2;
0
d. Revising paragraphs (m) and (n); and
0
e. Adding table 1.
    The revisions and addition read as follows:


Sec.  71.206  Quarterly sampling; designated work positions.

* * * * *
    (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.
* * * * *
    (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

[[Page 45017]]

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:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
* * * * *
    (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 (k) 
and (l) of this section.
    (k) Upon issuance of a citation for violation of the standard, the 
operator shall take the following actions sequentially:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to at or below the standard; and
* * * * *
    (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.   71.206--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
----------------------------------------------------------------------------------------------------------------

Subpart D--Respirable Dust Control Plans

0
23. Amend Sec.  71.300 by revising paragraph (a) introductory text to 
read as follows:


Sec.  71.300  Respirable dust control plan; filing requirements.

    (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.
* * * * *
0
24. Amend Sec.  71.301 by revising paragraph (a)(1) to read as follows:


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

    (a) * * *
    (1) The respirable dust control measures would be likely to 
maintain concentrations of respirable coal mine dust at or below the 
standard; and
* * * * *

PART 72--HEALTH STANDARDS FOR COAL MINES

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

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

Subpart E--Miscellaneous

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


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

    Approved respirators shall be selected, fitted, used, and 
maintained in accordance with the provisions of a respiratory 
protection program consistent with the requirements, as applicable, 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 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.html 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/.
0
27. 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. Noncompliance 
with the respirable dust standard, in accordance with this subchapter, 
is demonstrated when a single, full-shift measurement taken by

[[Page 45018]]

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.

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

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

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

Subpart D--Ventilation

0
29. Amend Sec.  75.350 by:
0
a. Revising paragraph (b)(3)(i);
0
b. Removing paragraph (b)(3)(ii); and
0
c. Redesignating (b)(3)(iii) as (b)(3)(ii).
    The revision reads as follows:


Sec.  75.350  Belt air course ventilation.

* * * * *
    (b) * * *
    (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\).
* * * * *

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

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

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

Subpart A--General

0
31. Amend Sec.  90.2 by revising the definition of ``Part 90 miner'' 
and removing the definition of ``Quartz''.
    The revision reads as follows:


Sec.  90.2  Definitions.

* * * * *
    Part 90 miner. A miner employed at a coal mine who has exercised 
the option under the old section 203(b) program (36 FR 20601 preview 
citation details, October 27, 1971), 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.
* * * * *
0
32. Amend Sec.  90.3 by revising paragraph (a) to read as follows:


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

    (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.
* * * * *

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


Sec.  90.101  [Removed and Reserved]

0
33. Remove and reserve Sec.  90.101.
0
34. Amend Sec.  90.102 by revising paragraph (a) to read as follows:


Sec.  90.102  Transfer; notice.

    (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.
* * * * *
0
35. Amend Sec.  90.104 by revising paragraph (a)(2) to read as follows:


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

    (a) * * *
    (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
* * * * *

Subpart C--Sampling Procedures

0
36. Amend Sec.  90.205 by revising paragraph (c) to read as follows:


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

* * * * *
    (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.
0
37. Amend Sec.  90.206 by revising paragraphs (b) and (c) to read as 
follows:


Sec.  90.206  Exercise of option or transfer sampling.

* * * * *
    (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).
0
38. Amend Sec.  90.207 by:
0
a. Removing and reserving paragraph (b);
0
b. Revising paragraphs (c) introductory text, (c)(2), (d), (e), (f) 
introductory text, (f)(2) introductory text, (f)(2)(ii), and (g);
0
c. Removing tables 90-1 and 90-2; and
0
d. Adding table 1.
    The revisions and addition read as follows:


Sec.  90.207  Quarterly sampling.

* * * * *
    (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:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable coal mine dust to below the standard; and
* * * * *
    (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

[[Page 45019]]

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 (f) and (g) of this section.
    (f) Upon issuance of a citation for a violation of the standard, 
the operator shall take the following actions sequentially:
* * * * *
    (2) Immediately take corrective action to lower the concentration 
of respirable dust to below the standard. If the corrective action 
involves:
* * * * *
    (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).
* * * * *
    (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.   90.207--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
----------------------------------------------------------------------------------------------------------------

Subpart D--Respirable Dust Control Plans

0
39. Amend Sec.  90.300 by revising paragraphs (a) and (b)(3) to read as 
follows:


Sec.  90.300  Respirable dust control plan; filing requirements.

    (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) * * *
    (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
* * * * *
0
40. Amend Sec.  90.301 by revising paragraphs (a)(1) and (b) to read as 
follows:


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

    (a) * * *
    (1) The respirable dust control measures would be likely to 
maintain concentrations of respirable coal mine dust below the 
standard; and
* * * * *
    (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.
* * * * *
[FR Doc. 2023-14199 Filed 7-6-23; 11:15 am]
BILLING CODE 4520-43-P