[Federal Register Volume 63, Number 209 (Thursday, October 29, 1998)]
[Proposed Rules]
[Pages 58104-58270]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-28277]



[[Page 58103]]

_______________________________________________________________________

Part II





Department of Labor





_______________________________________________________________________



Mine Safety and Health Administration



_______________________________________________________________________



30 CFR Part 57



Diesel Particulate Matter Exposure of Underground Metal and Nonmetal 
Miners; Proposed Rule

  Federal Register / Vol. 63, No. 209 / Thursday, October 29, 1998 / 
Proposed Rules  

[[Page 58104]]



DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 57

RIN 1219-AB11


Diesel Particulate Matter Exposure of Underground Metal and 
Nonmetal Miners

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

ACTION: Proposed rule.

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

SUMMARY: This proposed rule would establish new health standards for 
underground metal and nonmetal mines that use equipment powered by 
diesel engines.
    The proposed rule is designed to reduce the risks to underground 
metal and nonmetal miners of serious health hazards that are associated 
with exposure to high concentrations of diesel particulate matter 
(dpm). DPM is a very small particle in diesel exhaust. Underground 
miners are exposed to far higher concentrations of this fine 
particulate than any other group of workers. The best available 
evidence indicates that such high exposures put these miners at excess 
risk of a variety of adverse health effects, including lung cancer.
    The proposed rule for underground metal and nonmetal mines would 
establish a concentration limit for dpm, and require mine operators to 
use engineering and work practice controls to reduce dpm to that limit. 
Underground metal and nonmetal mine operators would also be required to 
implement certain ``best practice'' work controls similar to those 
already required of underground coal mine operators under MSHA's 1996 
diesel equipment rule. These operators would also be required to train 
miners about the hazards of dpm exposure.
    MSHA has already proposed a rule to control dpm exposures in 
underground coal mines in a separate notice to the public published in 
the Federal Register on April 9, 1998 (62 FR 17492).

DATES: Comments must be received on or before February 26, 1999. Submit 
written comments on the information collection requirements by February 
26, 1999.

ADDRESSES: Comments on the proposed rule may be transmitted by 
electronic mail, fax, or mail, or dropped off in person at any MSHA 
office. Comments by electronic mail must be clearly identified as such 
and sent to this e-mail address: [email protected]. Comments by fax 
must be clearly identified as such and sent to: MSHA, Office of 
Standards, Regulations, and Variances, 703-235-5551. Send mail comments 
to: MSHA, Office of Standards, Regulations, and Variances, Room 631, 
4015 Wilson Boulevard, Arlington, VA 22203-1984, or any MSHA district 
or field office. The Agency will have copies of the proposal available 
for review by the mining community at each district and field office 
location, at the National Mine Health and Safety Health Academy, and at 
each technical support center. The document will also be available for 
loan to interested members of the public on an as needed basis. MSHA 
will also accept written comments from the mining community at the 
field and district offices, at the National Mine Health and Safety 
Academy, and at technical support centers. These comments will become a 
part of the official rulemaking record. Interested persons are 
encouraged to supplement written comments with computer files or disks; 
please contact the Agency with any questions about format.
    Written comments on the information collection requirements may be 
submitted directly to the Office of Information and Regulatory Affairs, 
New Executive Office Building, 725 17th Street, NW., Rm. 10235, 
Washington, D.C. 20503, Attn: Desk Officer for MSHA.

FOR FURTHER INFORMATION CONTACT: Carol J. Jones, Acting Director; 
Office of Standards, Regulations, and Variances; MSHA; (703)235-1910.

SUPPLEMENTARY INFORMATION:

I. Questions and Answers About This Proposed Rule

(A) General Information of Interest to the Entire Mining Community

(1) What Actions Are Being Proposed?
    MSHA has determined that action is essential to reduce the exposure 
of miners to a harmful substance emitted from diesel engines--and that 
regulations are needed for this purpose in underground mines. This 
notice proposes requirements for underground metal and nonmetal mines.
    The harmful substance is known as diesel particulate matter (dpm). 
As shown in Figure I-1, average concentrations of dpm observed in 
dieselized underground mines are up to 200 times as high as average 
environmental exposures in the most heavily polluted urban areas and up 
to 10 times as high as median exposures estimated for the most heavily 
exposed workers in other occupational groups. The best available 
evidence indicates that exposure to such high concentrations of dpm 
puts miners at significantly increased risk of incurring serious health 
problems, including lung cancer.
    The goal of the proposed rule is to reduce underground miner 
exposures to attain the highest degree of safety and health protection 
that is feasible.

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[GRAPHIC] [TIFF OMITTED] TP29OC98.018



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    On April 9, 1998, (62 FR 17492), MSHA proposed a rule to achieve 
this goal in underground coal mines. MSHA's proposal would require the 
installation of high-efficiency filters on diesel-powered equipment to 
trap diesel particles before they enter the mine atmosphere. Following 
18 months of education and technical assistance by MSHA after the rule 
is issued, filters would first have to be installed on permissible 
diesel-powered equipment. By the end of the following year (i.e., 30 
months after the rule is issued), such filters would also have to be 
installed on any heavy-duty outby equipment. No specific concentration 
limit would be established in this sector; the proposed rule would 
require that filters be installed and properly maintained. Miner 
awareness training on the hazards of dpm would also be required.
    With this notice, MSHA is proposing to adopt a different rule to 
achieve this goal in underground metal and nonmetal mines. MSHA is 
proposing that a limit on the concentration of dpm to which miners may 
be exposed would be established for underground metal and nonmetal 
mines. The limit would restrict dpm concentrations in underground metal 
and nonmetal mines to about 200 micrograms per cubic meter of air. 
Operators would be able to select whatever combination of engineering 
and work practice controls they want to keep the dpm concentration in 
the mine below this limit. The concentration limit would be implemented 
in two stages: an interim limit that would go into effect following 18 
months of education and technical assistance by MSHA, and a final limit 
after 5 years. MSHA sampling would be used to determine compliance. The 
proposal for this sector would also require that all underground metal 
and nonmetal mines using diesel-powered equipment observe a set of 
``best practices'' to reduce engine emissions--e.g., to use low-sulfur 
fuel. Similar practices are already in effect in underground coal mines 
as a result of MSHA's 1996 diesel equipment rule.
    MSHA is not at this time proposing a rule applicable to surface 
mines. As illustrated in Figure I-1, in certain situations the 
concentrations of dpm at surface mines may exceed those to which rail, 
trucking and dock workers are exposed. Problem areas identified in this 
sector include production areas where miners work in the open air in 
close proximity to loader-haulers and trucks powered by older, out-of-
tune diesel engines, or other confined spaces where diesel engines are 
running. The Agency believes, however, that these problems are 
currently limited and readily controlled through education and 
technical assistance. Using tailpipe exhaust extenders, or directing 
the exhaust across the engine fan, can dilute the high concentrations 
of dpm that might otherwise occur in areas immediately adjacent to 
mining equipment. Surface mine operators using or planning to switch to 
environmentally conditioned cabs to reduce noise exposure to equipment 
operators might also be able to incorporate filtration features that 
would protect these miners from high dpm concentrations as well. 
Completing already planned purchases of new trucks containing cleaner 
engines may also help reduce the isolated instances of high dpm 
concentrations at such mines.
    The Agency would like to emphasize, however, that surface miners 
are entitled to the same level of protection as other miners, and that 
the Agency's risk assessment indicates that even short-term exposures 
to concentrations of dpm like those observed may result in serious 
health problems. Accordingly, in addition to providing education and 
technical assistance to surface mines, the Agency will also continue to 
evaluate the hazards of diesel particulate exposure at surface mines 
and will take any necessary action, including regulatory action if 
warranted, to help the mining community minimize any hazards.
(2) How Is This Notice of Proposed Rulemaking Organized? What Portions 
Do I Need To Read If I have Already Reviewed MSHA's Notice of Proposed 
Rulemaking To Limit dpm in Underground Coal Mines?
    The proposed rule for underground metal and nonmetal mines can be 
found at the end of this Notice. The remainder of this preamble to the 
proposed rule (Supplementary Information) describes the Agency's 
rationale for what is being proposed.
    Part I consists of a series of ``Questions and Answers.'' The 
Agency hopes they will provide most of the information you will need to 
formulate your comments. The first ten of these Questions and Answers 
(Section A) provide a general overview of this rulemaking. This is 
followed (Section B) by twenty additional Questions and Answers that 
address specific provisions of the proposed rule.
    Part II provides some background information on nine topics that 
are relevant to this rulemaking. In order, the topics covered are: (1) 
The role of diesel-powered equipment in mining; (2) the composition of 
diesel exhaust and diesel particulate; (3) measurement of diesel 
particulate; (4) reducing soot at the source--EPA regulation of diesel 
engine design;(5) limiting the public's exposure to soot--EPA ambient 
air quality standards; (6) controlling diesel particulate emissions in 
mining--a toolbox; (7) existing mining standards that limit miner 
exposure to occupational diesel particulate emissions; (8) how other 
jurisdictions are restricting occupational exposure to diesel soot; and 
(9) MSHA's initiative to limit miner exposure to diesel particulate--
the history of this rulemaking and related actions. Part II of this 
preamble is virtually identical to its counterpart in the preamble to 
MSHA's proposed rule to limit dpm concentrations in underground coal 
mines; the only exception is that the very last paragraph here, on the 
history of dpm rulemaking, has been updated to reflect the issuance of 
the proposed rule on underground coal. Appended to the end of this 
document, is an MSHA publication, ``Practical Ways to Reduce Exposure 
to Diesel Exhaust in Mining--A Toolbox,'' includes additional 
information on methods for controlling dpm, and a glossary of terms.
    Part III is the Agency's risk assessment. The first section 
presents the Agency's data on current dpm exposure levels in each 
sector of the mining industry. The second section reviews the 
scientific evidence on the risks associated with exposure to dpm. The 
third section evaluates this evidence in light of the Mine Act's 
statutory criteria. Part III of this preamble is virtually identical to 
its counterpart in the preamble to MSHA's proposed rule to limit dpm 
concentrations in underground coal mines; the only exception is the 
language in Section III.3.c., reflecting the fact that the proposed 
rules are different for each sector, and hence had to be evaluated 
separately as to whether they satisfy the requirements of the law.
    Part IV is a detailed section-by-section explanation and discussion 
of the elements of the proposed rule.
    Part V is an analysis of whether the proposed rule meets the 
Agency's statutory obligation to attain the highest degree of safety or 
health protection for miners, with feasibility a consideration. This 
part begins with a review of the law and a profile of the industry's 
economic position. The next part explores the extent to which the 
proposed rule is expected to impact existing concentration levels, 
reviews significant alternatives that might provide more protection 
than the rule being proposed but which have not been adopted by the 
Agency due to feasibility concerns, and then discusses the

[[Page 58107]]

feasibility of the rule being proposed. Part V draws upon a computer 
simulation of how the proposed rule in underground metal and nonmetal 
mines is expected to impact dpm concentrations; accordingly, an 
Appendix to this discussion provides information about the simulation 
methodology. The simulation method, which can be performed using a 
standard spreadsheet program, can be used to model conditions and 
control impacts in any underground mine; copies of this model are 
available to the mining community from MSHA.
    Part VI reviews several impact analyses which the Agency is 
required to provide in connection with a proposed rulemaking. This 
information summarizes a more complete discussion that can be found in 
the Agency's Preliminary Regulatory Economic Analysis (PREA). Copies of 
this document are available from the Agency and will be posted on the 
MSHA Web site (http://www.msha.gov).
    Part VII is a complete list of publications referenced by the 
Agency in the preamble.
(3) What Evidence Does MSHA Have That Current Underground 
Concentrations of DPM Need To Be Controlled?
    The best available evidence MSHA has at this time is that miners 
subjected to an occupational lifetime of dpm exposure at concentrations 
we presently find in underground mines face a significant risk of 
material impairment to their health.
    It has been recognized for some time that miners working in close 
contact with diesel emissions can suffer acute reactions--e.g., eye, 
nose and throat irritations--but questions have persisted as to what 
component of the emissions was causing these problems, whether exposure 
increased the risk of other adverse health effects, and the level of 
exposure creating health consequences.
    In recent years, there has been growing evidence that it is the 
very small respirable particles in diesel exhaust (dpm) that trigger a 
variety of adverse health outcomes. These particles are generally less 
than one-millionth of a meter in diameter (submicron), and so can 
readily penetrate into the deepest recesses of the lung. They consist 
of a core of the element carbon, with up to 1,800 different organic 
compounds adsorbed onto the core, and some sulfates as well. (A diagram 
of dpm can be found in Part II of this preamble--see Figure II-3). The 
physiological mechanism by which dpm triggers particular health 
outcomes is not yet known. One or more of the organic substances 
adsorbed onto the surface of the core of the particles may be 
responsible for some health effects, since these include many known or 
suspected mutagens and carcinogens. But some or all of the health 
effects might also be triggered by the physical properties of these 
tiny particles, since some of the health effects are observed with high 
exposures to any ``fine particulate,'' whether the particle comes from 
diesel exhaust or another source.
    There is clear evidence that exposure to high concentrations of dpm 
can result in a variety of serious health effects. These health effects 
include: (i) Sensory irritations and respiratory symptoms serious 
enough to distract or disable miners; (ii) death from cardiovascular, 
cardiopulmonary, or respiratory causes; and (iii) lung cancer.
    By way of example of the non-cancer effects, there is evidence that 
workers exposed to diesel exhaust during a single shift suffer material 
impairment of lung capacity. A control group of unexposed workers 
showed no such impairment, and workers exposed to filtered diesel 
exhaust (i.e., exhaust from which much of the dpm has been removed) 
experienced, on average, only about half as much impairment. Moreover, 
there are a number of studies quantifying significant adverse health 
effects--as measured by lost work days, hospitalization and increased 
mortality rates--suffered by the general public when exposed to 
concentrations of fine particulate matter like dpm far lower than 
concentrations to which some miners are exposed. The evidence from 
these fine particulate studies was the basis for recent rulemaking by 
the Environmental Protection Agency to further restrict the exposure of 
the general public to fine particulates, and the evidence was given 
very widespread and close scrutiny before that action was made final. 
Of particular interest to the mining community is that these fine 
particulate studies indicate that those who have pre-existing pulmonary 
problems are particularly at risk. Many individual miners in fact have 
such pulmonary problems, and the mining population as a whole is known 
to have such conditions at a higher rate than the general public.
    Although no epidemiological study is flawless, numerous 
epidemiological studies have shown that long term exposure to diesel 
exhaust in a variety of occupational circumstances is associated with 
an increased risk of lung cancer. With only rare exceptions, involving 
relatively few workers and/or observation periods too short to reliably 
detect excess cancer risk, the human studies have consistently shown a 
greater risk of lung cancer among workers exposed to dpm than among 
comparable unexposed workers. When results from the human studies are 
combined, the risk is estimated to be 30-40 percent greater among 
exposed workers, if all other factors (such as smoking habits) are held 
constant. The consistency of the human study results, supported by 
experimental data establishing the plausibility of a causal connection, 
provides strong evidence that chronic dpm exposure at high levels 
significantly increases the risk of lung cancer in humans.
    Moreover, all of the human occupational studies indicating an 
increased frequency of lung cancer among workers exposed to dpm 
involved average exposure levels estimated to be far below the levels 
observed in underground mines--and even below the limits being 
proposed. As noted in Part III, MSHA views extrapolations from animal 
experiments as subordinate to results obtained from human studies. 
However, it is noteworthy that dpm exposure levels recorded in some 
underground mines have been within the exposure range that produced 
tumors in rats.
    Based on the scientific data available in 1988, the National 
Institute for Occupational Safety and Health (NIOSH) identified dpm as 
a probable or potential human carcinogen and recommended that it be 
controlled. Other organizations have made similar recommendations.
    MSHA carefully evaluated all the evidence available in light of the 
requirements of the Mine Act. Based on this evaluation, MSHA has 
reached several conclusions:
    (1) The best available evidence is that the health effects 
associated with exposure to dpm can materially impair miner health or 
functional capacity.
    (2) At levels of exposure currently observed in underground mining, 
many miners are presently at significant risk of incurring these 
material impairments over a working lifetime.
    (3) The reduction in dpm exposures that is expected to result from 
implementation of the proposed rule for underground metal and nonmetal 
mines would substantially reduce the significant risks currently faced 
by underground metal and nonmetal miners exposed to dpm.
    MSHA had its risk assessment independently peer reviewed. The risk 
assessment presented here incorporates revisions made in accordance 
with the reviewers' recommendations. The reviewers stated that:

    * * * principles for identifying evidence and characterizing 
risk are thoughtfully set

[[Page 58108]]

out. The scope of the document is carefully described, addressing 
potential concerns about the scope of coverage. Reference citations 
are adequate and up to date. The document is written in a balanced 
fashion, addressing uncertainties and asking for additional 
information and comments as appropriate. (Samet and Burke, Nov. 
1997.)

    The proposed rule would reduce the concentration of one type of 
fine particulate in underground metal and nonmetal mines--that from 
diesel emissions--but would not explicitly control miner exposure to 
other fine airborne particulates present underground. In light of the 
evidence presented in the Agency's risk assessment on the risks that 
fine particulates in general may pose to the mining population, MSHA 
would welcome comments as to whether the Agency should also consider 
restricting the exposure of underground metal and nonmetal miners to 
all fine particulates, regardless of the source.
(4) Aren't NIOSH and the NCI Working on a Study That Will Provide 
Critical Information? Why Proceed Before the Evidence Is Complete?
    NIOSH and the National Cancer Institute (NCI) are collaborating on 
a cancer mortality study that will provide additional information about 
the relationship between dpm exposure levels and disease outcomes, and 
about which components of dpm may be responsible for the observed 
health effects. The study is projected to take about seven years. The 
protocol for the study was recently finalized.
    The information the study is expected to generate will be a 
valuable addition to the scientific evidence on this topic. But given 
its conclusions about currently available evidence, MSHA believes the 
Agency needs to take action now to protect miners' health. Moreover, as 
noted by the Supreme Court in an important case on risk involving the 
Occupational Safety and Health Administration, the need to evaluate 
risk does not mean an agency is placed into a ``mathematical 
straightjacket.'' Industrial Union Department, AFL-CIO v. American 
Petroleum Institute, 448 U.S. 607, 100 S.Ct. 2844 (1980). The Court 
noted that when regulating on the edge of scientific knowledge, 
absolute scientific certainty may not be possible, and ``so long as 
they are supported by a body of reputable scientific thought, the 
Agency is free to use conservative assumptions in interpreting the data 
* * * risking error on the side of overprotection rather than 
underprotection.'' (Id. at 656.) This advice has special significance 
for the mining community, because a singular historical factor behind 
the enactment of the current Mine Act was the slowness in coming to 
grips with the harmful effects of other respirable dust (coal dust).
    It is worth noting that while the cohort selected for the NIOSH/NCI 
study consists of underground miners (specifically, underground metal 
and nonmetal miners), this choice is in no way linked to MSHA's 
regulatory framework or to miners in particular. This cohort was 
selected for the study because it provides the best population for 
scientists to study. For example, one part of the study would compare 
the health experiences of miners who have worked underground in mines 
with long histories of diesel use with the health experiences of 
similar miners who work in surface areas where exposure is 
significantly lower. Since the general health of these two groups is 
very similar, this will help researchers to quantify the impacts of 
diesel exposure. No other population is as easy to study for this 
purpose. But as with any such epidemiological study, the insights 
gained are not limited to the specific population used in the study. 
Rather, the study will provide information about the relationship 
between exposure and health effects that will be useful in assessing 
the risks to any group of workers in a dieselized industry.
(5) What Are the Impacts of the Proposed Rule?
    Costs. Table I-1 provides cost information. Some explanation is 
necessary.
    Costs consist of two components: ``initial'' costs (e.g., capital 
costs for equipment, or the one-time costs of developing a procedure), 
which are then amortized over a period of years in accordance with a 
standardized formula to provide an ``annualized'' cost; and ``annual'' 
costs that occur every year (e.g., maintenance or training costs). 
Adding together the ``annualized'' initial costs and the ``annual'' 
costs provides the per year costs for the rule.
    It should be noted that in amortizing the initial costs, a net 
present value factor was applied to certain costs: those associated 
with provisions where mine operators do not have to make capital 
expenditures until some period of time after the effective date. 
Detailed information on this point is contained in the Agency's 
Preliminary Regulatory Economic Analysis (PREA), as are the Agency's 
cost assumptions.
    The costs per year to the underground metal and nonmetal industry 
are about $19.2 million. These costs are higher than the costs for the 
proposed rule for underground coal mines, reflecting the much more 
intense use of diesel-powered equipment in this sector. The Agency 
spent considerable time developing its cost assumptions and estimates, 
which are spelled out in detail in the Agency's PREA. Assumptions are 
based upon information provided by MSHA technical personnel, who have 
had discussions with manufacturers of engines and mining equipment, and 
from journals and reports published by independent organizations that 
collect data about the mining industry. The Agency would encourage the 
mining community to provide detailed comments in this regard so as to 
ensure these cost assumptions and estimates are as accurate as 
possible. With respect to the largest cost item--the cost to meet the 
proposed concentration limit in underground metal and nonmetal mines--
MSHA assumed that engineering controls, such as low emission engines, 
ceramic filters, oxidation catalytic converters, and cabs would be 
needed on diesel powered equipment. Most of the engineering controls 
would be needed on diesel equipment used for production, while a small 
amount of diesel equipment that is used for support purposes would need 
engineering controls. In addition to these controls, MSHA assumed that 
some underground metal and nonmetal mines would need to make 
ventilation changes in order to meet the proposed concentration limits.

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[[Page 58109]]

Table I-1.--Compliance Cost for Underground Metal and Nonmetal Mine 
Operators

(Dollars X 1,000)
[GRAPHIC] [TIFF OMITTED] TP29OC98.019

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[[Page 58110]]

    As required by the Regulatory Flexibility Act, MSHA has performed a 
review of the effects of the proposed rule on ``small entities''. The 
results--including information about the average cost for mines in each 
sector with less than 500 employees and mines in each sector with less 
than 20 miners--are summarized in response to Question 7.
    Paperwork. Tables I-2 and I-3 show additional paperwork burden 
hours which the proposed rule would require. Only those existing or 
proposed regulatory requirements which would, as a result of this 
rulemaking, result in new burden hours, are noted. The costs for these 
paperwork burdens, a subset of the overall costs of the proposed rule, 
are specifically noted in Part VII of the Agency's PREA. Table I-2 
shows the burden hours for large and small mines--those with less than 
20 miners.

      Table I-2.--Underground Metal and Nonmetal Mine Burden Hours
------------------------------------------------------------------------
                    Detail                      Large    Small    Total
------------------------------------------------------------------------
57.5060......................................      306      123      429
57.5062......................................       49       11       60
57.5066......................................      207       76      283
57.5070......................................      136        6      142
57.5071......................................    2,600      213    2,813
57.5075......................................      131        7      138
                                              --------------------------
    Total....................................    3,429      436    3,865
------------------------------------------------------------------------

    Table I-3 shows the additional burden hours for diesel engine 
manufacturers. The compliance costs related to diesel equipment 
manufacturers are assumed to be passed through to underground metal and 
nonmetal operators as explained in the PREA. Thus, diesel equipment 
manufacturers are not estimated to incur any direct cost as a result of 
this rule.

          Table I-3.--Diesel Engine Manufacturers Burden Hours
------------------------------------------------------------------------
                             Detail                               Total
------------------------------------------------------------------------
Part 7, Subpart E..............................................       36
    Total......................................................       36
------------------------------------------------------------------------

    Benefits. The proposed rule would reduce the exposure of 
underground metal and nonmetal miners to dpm, thereby reducing the risk 
of adverse health effects and their concomitant effects.
    The risks being addressed by this rulemaking arise because some 
miners are exposed to high concentrations of the very small particles 
produced by engines that burn diesel fuel. As discussed in Part II of 
the preamble, diesel powered engines are used increasingly in 
underground mining operations because they permit the use of mobile 
equipment and provide a full range of power for both heavy-duty and 
light-duty operations (i.e., for production equipment and support 
equipment, respectively), while avoiding the explosive hazards 
associated with gasoline. But underground mines are confined spaces 
which, despite ventilation requirements, tend to accumulate significant 
concentrations of particles and gases--both those produced by the mine 
itself (e.g., methane gas and silica dust liberated by mining 
operations) and those produced by equipment used in the mine.
    As discussed in MSHA's risk assessment (Part III of this preamble), 
the concentrations of diesel particulates to which some underground 
miners are currently exposed are significantly higher than the 
concentrations reported for other occupations involving the use of 
dieselized equipment; and at such concentrations, exposure to dpm by 
underground miners over a working lifetime is associated with an excess 
risk of a variety of adverse health effects.

[[Page 58111]]

    The nature of the adverse health effects associated with such 
exposures suggests the nature of the savings to be derived from 
controlling exposure. Acute reactions can result in lost production 
time for the operator and lost pay (and perhaps medical expenses) for 
the worker. Hospital care for acute breathing crises or cancer 
treatment can be expensive, result in lost income for the worker, lost 
income for family members who need to provide care and lost 
productivity for their employers, and may well involve government 
payments (e.g., Social Security disability and Medicare). Serious 
illness and death lead to long term income losses for the families 
involved, with the potential for costs from both employers (e.g., 
workers' compensation payouts, pension payouts) and society as a whole 
(e.g., government assisted aid programs).
    The information available to the Agency suggests that as exposure 
is reduced, so are the adverse health consequences. For example, data 
collected on the effects of environmental exposure to fine particulates 
suggest that reducing occupational dpm exposures by as little as 75 
g/m3 (roughly corresponding to a reduction of 25 
g/m3 in 24-hour ambient atmospheric concentration) 
could lead to significant reductions in the risk of various acute 
responses, including mortality. And chronic occupational exposure has 
been linked to an estimated 30 to 40 percent increase in the risk of 
lung cancer. All the quantitative risk models reviewed by NIOSH suggest 
excess risks of lung cancer of more than one per thousand for miners 
who have long-term occupational exposures to dpm concentrations in 
excess of 1000 g/m3, and the epidemiologically-
based risk estimates suggest higher risks. The Agency's estimate is 
that implementation of the proposed rule would avoid 28 lung cancers 
per 1,000 affected miners, or approximately 7 lung cancer cases a year 
over an initial 65-year period.\2\ Note that because lung cancer 
associated with diesel particulate matter typically arises from 
cumulative exposure and after some latency period, these health 
benefits-in terms of the reduced incidence of lung cancer illness and 
subsequent death-will not materialize until some years after passage of 
the proposed rule.
---------------------------------------------------------------------------

    \2\ In the long run, the average approaches 46445=10 
lung cancers avoided per year as the number of years considered 
increases beyond 65.
---------------------------------------------------------------------------

    The yearly reduction in excess lung cancer deaths due to reduced 
exposure to diesel particulate matter may occur gradually, depending on 
the historical cumulative exposure to diesel particulate matter among 
the veteran workforce. Since the average latency period for lung cancer 
is 20 years, the full benefit associated with a concentration limit of 
200 g/m\3\ may not be seen before then.
    Despite these quantitative indications, quantification of the 
benefits is difficult. Although increased risk of lung cancer has been 
shown to be associated with dpm exposure among exposed workers, a 
conclusive dose-response relationship upon which to base quantification 
of benefits has not been demonstrated. The Agency nevertheless intends, 
to the extent it can, to develop an appropriate analysis quantifying 
benefits in connection with the final rule.
    The Agency does not have much experience in quantifying benefits in 
the case of a proposed health standard (other than its recent proposal 
on controlling mining noise, where years of compliance data and hearing 
loss studies provide a much more complete quantitative picture than 
with dpm). MSHA therefore welcomes suggestions for the appropriate 
approach to use to quantify the benefits likely to be derived from this 
rulemaking. Please identify scientific studies, models, and/or 
assumptions suitable for estimating risk at different exposure levels, 
and data on numbers of miners exposed to different levels of dpm.

[[Page 58112]]

(6) Did MSHA Actively Consider Alternatives to What Is Being Proposed?
    Yes. Once MSHA determined that the evidence of risk required a 
regulatory action, the Agency considered a number of alternative 
approaches, the most significant of which are reviewed in Part V of the 
preamble.
    The consideration of options proceeded in accordance with the 
requirements of Section 101(a)(6)(A) of the Federal Mine Safety and 
Health Act of 1977 (the ``Mine Act''). In promulgating standards 
addressing toxic materials or harmful physical agents, the Secretary 
must promulgate standards which most adequately assure, on the basis of 
the best available evidence, that no miner will suffer material 
impairment of health over his/her working lifetime. In addition, the 
Mine Act requires that the Secretary, when promulgating mandatory 
standards pertaining to toxic materials or harmful physical agents, 
consider other factors, such as the latest scientific data in the 
field, the feasibility of the standard and experience gained under the 
Mine Act and other health and safety laws. Thus, the Mine Act requires 
that the Secretary, in promulgating a standard, attain the highest 
degree of health and safety protection for the miner, based on the 
``best available evidence,'' with feasibility a consideration.
    As a result, MSHA seriously considered a number of alternatives 
that would, if adopted as part of the proposed rule, have provided 
increased protection--and would also have significantly increased 
costs. For example, the Agency considered proposing a more stringent 
concentration limit for dpm in underground metal and nonmetal mines, or 
shortening the time frame to achieve compliance with that limit. But as 
discussed in more detail in Part V, MSHA concluded, however, that such 
an approach may not be feasible for the underground sector at this 
time. Options considered by the Agency included: requiring the 
installation of a particulate filter on every new piece of diesel-
powered equipment added to the fleet of an underground metal or 
nonmetal mine regardless of the dpm concentration level, as an added 
layer of miner protection; establishing a fixed schedule for operator 
monitoring of the concentration of diesel particulate emissions; and 
requiring control plans be preapproved by MSHA before implementation to 
ensure their effectiveness had been verified. These approaches were not 
included in the proposal because MSHA concluded that less stringent 
alternatives could achieve the same level of protection with less 
adverse impact.
    MSHA also considered alternatives that would have led to a 
significantly lower-cost proposal, e.g., establishing a less stringent 
concentration limit in underground metal and nonmetal mines, or 
increasing the time for mine operators to come into compliance. 
However, based on the current record, MSHA has tentatively concluded 
that such approaches would not be as protective as those being 
proposed, and that the approach proposed is both economically and 
technologically feasible. As a result, the Agency has not proposed to 
adopt these alternatives.
    MSHA also explored whether to permit the use of administrative 
controls (e.g., rotation of personnel) and personal protective 
equipment (e.g., respirators) to reduce the diesel particulate exposure 
of miners. It is generally accepted industrial hygiene practice, 
however, to eliminate or minimize hazards at the source before 
resorting to personal protective equipment. Moreover, such a practice 
is generally not considered acceptable in the case of carcinogens since 
it merely places more workers at risk. Accordingly, the proposal 
explicitly prohibits the use of such approaches, except in those 
limited cases where MSHA approves, due to technological constraints, a 
2-year extension for an underground metal and nonmetal mine on the time 
to comply with the final concentration limit.
    MSHA did make a concerted effort to design the requirements of the 
proposal to minimize unnecessary burdens. Each element of the proposal 
was independently reviewed to ascertain whether it was really needed, 
as were all the paperwork requirements, and each was designed with 
cost-effectiveness in mind. Training and operator sampling 
requirements, for example, were specifically designed to be 
performance-oriented to minimize costs, while at the same time crafted 
to ensure that each operator's activities provide necessary 
protections.
    The Agency considered requiring the underground metal and nonmetal 
sector to use work practice and engine controls exactly like those 
already applicable in the underground coal sector as a result of MSHA's 
diesel equipment rule (62 FR 55412). Such an alternative would have 
required each metal and nonmetal operator: (a) to conduct weekly 
emissions tests of diesel-powered equipment in underground metal and 
nonmetal mines instead of just tagging suspect equipment for prompt 
inspection; (b) to establish training programs for maintenance 
personnel; and (c) to turn over the mine's diesel fleet within a few 
years so as to have only approved engines. The agency concluded, 
however, that the conditions which warrant such an approach in 
underground coal mines had not been established for metal and nonmetal 
mines; and that with respect to the risks created by dpm, the approach 
taken in the proposed rule could provide adequate protection in a cost-
effective manner.
    The agency hopes that comments and suggestions from the mining 
community on the proposed rule will help it identify further 
improvements in this regard.
(7) What Will the Impact Be on the Smallest Underground Metal and 
Nonmetal Mines? What Consideration Did MSHA Give to Alternatives for 
the Smallest Mines?
    The Regulatory Flexibility Act requires MSHA and other regulatory 
agencies to conduct a review of the effects of proposed rules on small 
entities. That review is summarized here; a copy of the full review is 
included in Part VI of this preamble, and in the Agency's PREA. The 
Agency encourages the mining community to provide comments on this 
analysis.
    The Small Business Administration generally considers a small 
mining entity to be one with less than 500 employees. MSHA has 
traditionally defined a small mine to be one with less than 20 miners, 
and has focused special attention on the problems experienced by such 
mines in implementing safety and health rules, e.g., the Small Mine 
Summit, held in 1996. Accordingly, MSHA has separately analyzed the 
impact of the proposed rule on mines with 500 employees or less, and 
those with less than 20 miners.
    Table I-4 summarizes MSHA's estimates of the average costs of the 
proposed rule to a small underground metal and nonmetal mine.

 Table I-4.--Average Cost per Small Underground Metal and Nonmetal Mine
------------------------------------------------------------------------
                    Size                      UG M/NM <500   UG M/NM <20
------------------------------------------------------------------------
Cost per mine...............................      $87,800       $56,100
------------------------------------------------------------------------

    Pursuant to the Regulatory Flexibility Act, MSHA must determine 
whether the costs of the proposed rule constitute a ``significant 
impact on a substantial number of small entities.'' Pursuant to the 
Regulatory Flexibility Act, if an Agency determines that a proposed 
rule

[[Page 58113]]

does not have such an impact, it must publish a ``certification'' to 
that effect. In such a case, no additional analysis is required (5 
U.S.C. Sec. 605).
    In evaluating whether certification is appropriate, MSHA utilized 
an impact analysis comparing the costs of the proposal to the revenues 
of the sector involved (only the revenues for underground metal and 
nonmetal mines are used in this calculation).
    The Agency has, as required by law (5 U.S.C. Sec. 603), developed 
an initial regulatory flexibility analysis which is set forth in Part 
VI of this preamble (and the Agency's PREA). In addition to a succinct 
statement of the objects of the proposed rule and other information 
required by the Regulatory Flexibility Act, the analysis reviews 
alternatives considered by the Agency with an eye toward the nature of 
small business entities. MSHA welcomes comment on this analysis, on 
possible impacts of the proposed rule on small mines, and suggestions 
to ameliorate those impacts.
    In promulgating standards, MSHA does not reduce protection for 
miners employed at small mines. But MSHA does consider the impact of 
its standards on even the smallest mines when it evaluates the 
feasibility of various alternatives. For example, a major reason why 
MSHA concluded it needed to stagger the effective dates of some of the 
requirements in the proposed rule is to ensure that it would be 
feasible for the smallest mines to have adequate time to come into 
compliance.
    Consistent with recent amendments to the Regulatory Flexibility Act 
under SBREFA (the Small Business Regulatory Enforcement Fairness Act), 
MSHA has already started considering actions it can take to minimize 
the anticipated compliance burdens of this proposed rule on smaller 
mines. For example, no limit on dpm concentration would be in effect in 
underground metal and nonmetal mines for 18 months--and during that 
time, the Agency plans to provide extensive compliance assistance to 
the mining community. The metal and nonmetal community would also have 
an additional three and a half years to comply with the final 
concentration limit, which in many cases means these mines may have a 
full five years of technical assistance before any engineering controls 
are required. MSHA would focus its efforts on smaller operators in 
particular--to training them in measuring dpm concentrations, and 
providing technical assistance on available controls. The Agency will 
also issue a compliance guide, and continue its current efforts to 
disseminate educational materials and software. Comment is invited on 
whether compliance workshops or other such approaches would be 
valuable.
(8) Why Would the Proposed Rule Require Special Training for 
Underground Miners Exposed to Diesel Exhaust? And Why Does the Proposed 
Rule not Address Medical Surveillance and Medical Removal Protection 
for Affected Miners?
    Training. Diesel particulate exposure has been linked to a number 
of serious health hazards, and the Agency's risk assessment indicates 
that the risks should be reduced as much as feasible. It has been the 
experience of the mining community that miners must be active and 
committed partners along with government and industry in successfully 
reducing these risks. Therefore, training miners as to workplace risks 
is a key component of mine safety and health programs. This rulemaking 
continues that approach.
    Specifically, pursuant to proposed Sec. 57.5070(a), any underground 
miner ``who can reasonably be expected to be exposed to diesel 
emissions'' would have to receive instruction in: (1) The health risks 
associated with dpm exposure; (2) in the methods used in the mine to 
control diesel particulate concentrations; (3) in identification of the 
personnel responsible for maintaining those controls; and (4) in 
actions miners must take to ensure the controls operate as intended. 
The training is to be provided annually in all mines using diesel-
powered equipment, and is to be provided without charge to the miner.
    MSHA does not expect this training to be a significant new burden 
for mine operators. The training required can be provided at minimal 
cost and with minimal disruption. The proposal would not require any 
special qualifications for instructors, nor would it specify the 
minimum hours of instruction. The purpose of the proposed requirement 
is miner awareness, and MSHA believes this can be accomplished by 
operators in a variety of ways. In mines that have regular safety 
meetings before the shift begins, devoting one of those meetings to the 
topic of diesel particulate would probably be a very easy way to convey 
the necessary information. Mines not having such a regular meeting can 
schedule a ``toolbox'' talk for this purpose. MSHA will be developing 
an outline of educational material that can be used in these settings. 
Simply providing miners with a copy of MSHA's toolbox, and reviewing 
how to use it, can cover several of the training requirements.
    Operators may choose to include required dpm training under Part 48 
training as an additional topic. Part 48 training plans, however, must 
be approved. There is no existing requirement that Part 48 training 
include a discussion of the hazards and control of diesel emissions. 
While mine operators are free to cover additional topics during the 
Part 48 training sessions, the topics that must be covered during the 
required time frame may make it impracticable to cover other matters 
within the prescribed time limits. Where the time is available in mines 
using diesel-powered equipment, operators should be free to include the 
dpm instruction in their proposed Part 48 training plans. The Agency 
does not believe special language in the proposed rule is needed to 
permit this action under Part 48, but welcomes comment in this regard.
    The proposal would not require the mine operator to separately 
certify the completion of the diesel particulate training, but some 
evidence that the training took place would have to be produced upon 
request. A serial log with the employee's signature is a perfectly 
acceptable practice in this regard.
    Medical surveillance. Another important source of information that 
miners and operators can use to protect health can come from medical 
surveillance programs. Such programs provide for medical evaluations or 
tests of miners exposed to particularly hazardous substances, at the 
operator's expense, so that a miner exhibiting symptoms or adverse test 
results can receive timely medical attention, ensure that personal 
exposure is reduced as appropriate and controls are reevaluated. 
Sometimes, to ensure that this source of information is effective, 
medical removal (transfer) protection must also be required. Medical 
transfer may address protection of a miner's employment, a miner's pay 
retention, a miner's compensation, and a miner's right to opt for 
medical removal.
    As a general rule, medical surveillance programs have been 
considered appropriate when the exposures are to potential carcinogens. 
MSHA has in fact been considering a generic requirement for medical 
surveillance as part of its air quality standards rulemaking. MSHA also 
recently proposed a medical surveillance program for hearing, as part 
of the Agency's proposed rule on noise exposure (61 FR 66348).
    MSHA is not proposing such a program for dpm at this time because 
it is still gathering information on this issue. The Agency, however, 
welcomes

[[Page 58114]]

comments regarding this issue and also, on medical removal.
    Specifically, the Agency would welcome comment on the following 
questions: (a) What kinds of examinations or tests would be appropriate 
to detect whether miners are suffering ill effects as a result of dpm 
exposure; (b) the qualifications of those who would have to perform 
such examinations or tests and their availability; (c) whether such 
examinations or tests need to be provided and how frequently once the 
provisions of the rule are in effect; and (d) whether medical removal 
protections should be a component of a medical surveillance program.
    (9) What Are the Major Issues on Which MSHA Wants Comments? What If 
I Already Submitted Comments on the Same Point on the Proposed Rule for 
the Underground Coal Sector?
    MSHA wants the benefit of your experience and expertise: whether as 
a miner or mine operator in any mining sector; a manufacturer of 
diesel-powered engines, equipment, or emission control devices; or as a 
scientist, doctor, engineer, or safety and health professional. MSHA 
intends to review and consider all comments submitted to the Agency.
    While MSHA will endeavor to consider relevant comments on the 
proposed rule for underground coal mines in evaluating what to do in 
the underground metal and nonmetal sector (e.g., comments on risk, the 
effectiveness of filtration devices, etc.), the record established for 
each rulemaking is separate. Accordingly, the Agency encourages those 
who are interested in both rulemakings to submit separate or duplicate 
comments for each.
    The following list identifies some topics on which the Agency would 
particularly like information; requests for information on other topics 
can be found throughout the preamble.
    (a) Assessment of Risk/Benefits of the Rule. Part III of this 
preamble reviews information that the Agency has been able to obtain to 
date on the risks of dpm exposure to miners. The Agency welcomes your 
comments on the significance of the material already in the record, and 
any information that can supplement the record. For example, additional 
information on existing and projected exposures to dpm and to other 
fine particulates in various mining environments would be useful in 
getting a more complete picture of the situation in various parts of 
the mining industry. Additional information on the health risks 
associated with exposure to dpm--especially observations by trained 
observers or studies of acute or chronic effects of exposure to known 
levels of dpm or fine particles in general, information about pre-
existing health conditions in individual miners or miners as a group 
that might affect their reactions to exposures to dpm or other fine 
particles, and information about how dpm affects human health--would 
help provide a more complete picture of the relationship between 
current exposures and the risk of health outcomes. Information on the 
costs to miners, their families and their employers of the various 
health problems linked to dpm exposure, and the prevalence thereof, 
would help provide a more complete picture of the benefits to be 
expected from reducing exposure. And as discussed in response to 
Question and Answer 5, the Agency would welcome advice about the 
assumptions and approach to use in quantifying the benefits to be 
derived from this rule.
    (b) Proposed rule. Part IV of this preamble reviews each provision 
of the proposed rule, Part V discusses the economic and technological 
feasibility of the proposed rule, and Part VI reviews the projected 
impacts of the proposed rule. MSHA would welcome comments on each of 
these topics.
    The Agency would like your thoughts on the specific alternative 
approaches discussed in Part V. The options discussed include: 
adjusting the concentration limit for dpm; adjusting the phase-in time 
for the concentration limit; and requiring that specific technology be 
used in lieu of establishing a concentration limit.
    The Agency would also like your thoughts on more specific changes 
to the proposed rule that should be considered. For example, for 
underground metal and nonmetal mines, MSHA is proposing to measure the 
amount of total carbon to measure dpm concentrations. MSHA welcomes 
information relevant to this proposal. The Agency is also interested in 
obtaining as many examples as possible as to the specific situation in 
individual mines: the composition of the diesel fleet, what controls 
cannot be utilized due to special conditions, and any studies of 
alternative controls using the computer spreadsheet described in the 
Appendix to Part V of this preamble. (See Adequacy of Protection and 
the Feasibility of the Proposed Rule). Information about the 
availability and costs of various control technologies that are being 
developed (e.g., high-efficiency ceramic filters), experience with the 
use of available controls, and information that will help the Agency 
evaluate alternative approaches for underground metal and nonmetal 
mines would be most welcome. Comments from the underground coal sector 
on the implementation to date of diesel work practices (like the rule 
limiting idling, and the training of those who provide maintenance) 
would be helpful in evaluating related proposals for the underground 
metal and nonmetal sector. The Agency would appreciate information 
about any unusual situations that might warrant the application of 
special provisions.
    (c) Compliance Guidance. The Agency welcomes comments on any topics 
on which initial guidance ought to be provided as well as any 
alternative practices which MSHA should accept for compliance before 
various provisions of the rule go into effect.
    (d) Minimizing Adverse Impact of the Proposed Rule. The Agency has 
set forth its assumptions about impacts (e.g., costs, paperwork, and 
impact on smaller mines in particular) in some detail in this preamble 
and in the PREA, and would welcome comments on the methodology. 
Information on current operator equipment replacement planning cycles, 
tax, State requirements, or other information that might be relevant to 
purchasing new engines or control technology would likewise be helpful. 
The Agency would also welcome comments on the financial situation of 
the underground metal and nonmetal sector, including information that 
may be relevant to only certain commodities.
(10) When Will the Rule Become Effective? Will MSHA Provide Adequate 
Guidance Before Implementing the Rule?
    Some requirements of the proposed rule would go into effect 60 days 
after the date of promulgation: the requirement to provide basic hazard 
training to miners who are exposed underground to dpm, the ``best 
practice'' requirements (e.g., the requirement to use only low-sulfur 
fuel), and some related recordkeeping requirements.
    The next requirements would go into effect 18 months after the date 
the rule is promulgated. Underground metal and nonmetal mines would 
have to comply with an interim dpm concentration limit.
    Finally, five years after the date the rule is promulgated, all 
underground metal and nonmetal mines would have to comply with a final 
dpm concentration limit.
    MSHA intends to provide considerable technical assistance and 
guidance to the mining community before the various requirements go 
into

[[Page 58115]]

effect, and be sure MSHA personnel are fully trained in the 
requirements of the rule. A number of actions have already been taken 
toward this end. The Agency held workshops on this topic in 1995 which 
provided the mining community an opportunity to share advice on how to 
control dpm concentrations. The Agency has published a ``toolbox'' of 
methods available to mining operators to achieve reductions in dpm 
concentration (appended to the end of this document is a copy of an 
MSHA publication, ``Practical Ways to Reduce Exposure to Diesel Exhaust 
in Mining--A Toolbox,'' which includes additional information on 
methods for controlling dpm, and a glossary of terms). In addition, 
MSHA has developed a computer spreadsheet template which allows an 
operator to model the application of alternative engineering controls 
to reduce dpm. The design of the model, and several specific mine 
profiles developed illustrating its use, are discussed in part V of the 
preamble.
    The Agency is committed to issuing a compliance guide for mine 
operators providing additional advice on implementing the rule. MSHA 
would welcome suggestions on matters that should be discussed in such a 
guide. MSHA would also welcome comments on other actions it could take 
to facilitate implementation, and in particular whether a series of 
additional workshops would be useful.

(B) Additional Information About the Proposed Rule for Underground 
Metal and Nonmetal Mines

(11) What Basic Changes Does the Proposal Make to Part 57, the Health 
Rules for Underground Metal and Nonmetal Mines?
    What follows is a general overview of the changes proposed to Part 
57. The remainder of this part is devoted to addressing the details of 
the proposed rule in this sector.
    The first thing the proposal would do is require underground metal 
and nonmetal mines to observe a set of ``best practices'' to reduce 
engine emissions of dpm underground. Only low-sulfur diesel fuel and 
EPA-approved fuel additives would be permitted to be used in diesel-
powered equipment in underground areas. Idling of such equipment that 
is not required for normal mining operations would be prohibited. In 
addition, diesel engines would have to be maintained in good order to 
ensure that deterioration does not lead to emissions increases--
approved engines would have to be maintained in approved condition; the 
emission related components of non-approved engines would have to be 
maintained in accordance with manufacturer specifications; and any 
installed emission device would have to be maintained in effective 
operating condition. Equipment operators in underground metal and 
nonmetal mines would be authorized to tag equipment with potential 
emissions-related problems, and tagged equipment would have to be 
``promptly'' referred for a maintenance check. As an additional 
safeguard in this regard, maintenance to ensure compliance with these 
requirements would have to be done by persons qualified by virtue of 
training or experience to perform the maintenance.
    The proposed rule would also require that, with the exception of 
diesel engines used in ambulances and fire-fighting equipment, any 
diesel engines added to the fleet of an underground metal or nonmetal 
mine after the rule's promulgation must be an engine approved by MSHA 
under Part 7 or Part 36. The composition of the existing fleet would 
not be impacted by this part of the proposed rule.
    While these proposed work practice controls are similar to existing 
rule in effect in underground coal mines, they are somewhat less 
stringent. For example, unlike in coal mines, the proposed maintenance 
rule in underground metal and nonmetal mines would not require 
operators to establish training programs that meet certain criteria. 
Nor would the proposed rule require weekly tailpipe emissions tests.
    The second thing the proposal would do is establish a limit on the 
concentration of dpm permitted in areas of an underground metal or 
nonmetal mine where miners work or travel.
    The proposed standard is intended to limit dpm concentrations to 
which miners are exposed to about 200 micrograms per cubic meter of 
air--expressed as 200DPM g/m\3\. However, in an 
effort to make things easier on a day-to-day basis for the mining 
community, the proposed concentration limit on dpm for this sector 
would be expressed in terms of the measurement method MSHA will use for 
compliance purposes to determine dpm concentrations. (That method, 
NIOSH Analytical Method 5040, is specified in proposed Sec. 57.5061, 
and is discussed in more detail in response to Question 12. MSHA is 
proposing to use it because of its accuracy). The method will analyze a 
dust sample to determine the amount of total carbon present. Total 
carbon comprises 80-85% of the dpm emitted by diesel engines. 
Accordingly, using the lower boundary of 80%, a concentration limit of 
200DPM g/m\3\ can be achieved by restricting total 
carbon to 160TC g/m\3\. This is the way the 
proposed standard is expressed:

    After [insert the date 5 years after the date of promulgation of 
this rule] any mine operator covered by this part shall limit the 
concentration of diesel particulate matter to which miners are 
exposed by restricting the average eight-hour equivalent full shift 
airborne concentration of total carbon, where miners normally work 
or travel, to 160 micrograms per cubic meter of air 
(160TC g/m\3\).

    All underground metal and nonmetal mines would be given a full five 
years to meet this limit, which is referred to in this preamble as the 
``final'' concentration limit. However, starting eighteen months after 
the rule is promulgated, underground metal and nonmetal mines would 
have to observe an ``interim'' dpm concentration limit--expressed as a 
restriction on the concentration of total carbon of 400 micrograms per 
cubic meter (400TC g/m\3\). The interim limit would 
bring the concentration of whole dpm in underground metal and nonmetal 
mines to which miners are exposed down to about 500 micrograms per 
cubic meter. No limit at all on the concentration of dpm would be 
applicable for the first eighteen months following promulgation. 
Instead, this period would be used to provide compliance assistance to 
the metal and nonmetal mining community to ensure it understands how to 
measure and control diesel particulate matter concentrations in 
individual operations (and to implement work practice controls).
    A mine operator would have to use engineering or work practice 
controls to keep dpm concentrations below the applicable limit. 
Administrative controls (e.g., the rotation of miners) and personal 
protective equipment (e.g., respirators) are explicitly barred as a 
means of compliance with the interim or final concentration limit. An 
operator could filter the emissions from diesel-powered equipment, 
install cleaner-burning engines, increase ventilation, improve fleet 
management, or use a variety of other readily available controls; the 
selection of controls would be left to the operator's discretion. MSHA 
has published a ``toolbox'' of approaches that can be used to reduce 
dpm; a copy of this useful publication is appended to the end of this 
document. The Agency has also developed a model that can be run on a 
standard spreadsheet program to compare the effects of alternative 
controls before purchase and implementation decisions are made. The 
model, and some examples of its

[[Page 58116]]

use, are presented in Part V of this preamble.
    The proposal would provide that, if an operator of a metal or 
nonmetal mine can demonstrate that there is no combination of controls 
that can, due to technological constraints, be implemented within the 5 
years permitted to reduce the concentration of dpm to the final 
concentration limit, MSHA may approve an application for an additional 
extension of time to comply with the dpm concentration limit. Such a 
special extension is available only once, and is limited to 2 years. To 
obtain a special extension, an operator must provide information in the 
application adequate for MSHA to ensure that the operator will: (a) 
maintain concentrations at the lowest limit which is technologically 
achievable; and (b) take appropriate actions to minimize miner exposure 
(e.g., provide suitable respiratory protection during the extension 
period).
    Measurements to determine noncompliance with the dpm concentration 
limit would be made directly by MSHA, rather than having the Agency 
rely upon operator samples. Under the rule, a single Agency sample, 
using the sampling and analytical method prescribed by the rule, would 
be adequate to establish a violation. MSHA would take measurement 
uncertainty into account before issuing a citation, as discussed in 
response to Question 12.
    The proposed rule would require that if an underground metal or 
nonmetal mine exceeds the applicable limit on the concentration of dpm, 
a diesel particulate matter compliance plan must be established and 
remain in effect for 3 years. The purpose of such plans is to ensure 
that the mine has instituted practices that will demonstrably control 
dpm levels thereafter. Reflecting current practices in this sector, the 
plan would not have to be preapproved by MSHA. The plan would include 
information about the diesel-powered equipment in the mine and 
applicable controls. The proposed rule would require operator sampling 
to verify that the plan is effective in bringing dpm levels down below 
the applicable limit, with the records kept at the mine site with the 
plan to facilitate review. Failure of an operator to comply with the 
requirements of the dpm control plan or to conduct adequate 
verification sampling would be a violation; MSHA would not be required 
to sample to establish such a violation.
    To enhance miner awareness of the hazards involved, mines using 
diesel-powered equipment must annually train miners exposed to dpm in 
the hazards associated with that exposure, and in the controls being 
used by the operator to limit dpm concentrations. An operator may 
propose to include this training in the Part 48 training plan.
    The proposed rule would also require all operators in this sector 
using diesel-powered equipment to sample as often as necessary to 
effectively evaluate dpm concentrations at the mine. The purpose of 
this requirement is to assure that operators are familiar with current 
dpm concentrations so as to be able to protect miners. Since mine 
conditions vary, MSHA is not proposing to establish a defined schedule 
for operator sampling; but rather, to propose a performance-oriented 
approach. The Agency would evaluate compliance with this sampling 
obligation by reviewing evidence of operator compliance with the 
concentration limit, as well as information retained by operators about 
their sampling.
    Consistent with the statute, the proposed rule would require that 
miners and their representatives have the right to observe any operator 
monitoring--including any sampling required to verify the effectiveness 
of a dpm control plan.
(12) How Is MSHA Proposing To Measure the Amount of dpm in Underground 
Metal and Nonmetal Mines?
    Techniques for measuring dpm concentrations are reviewed in detail 
in Part II of this preamble.
    For a method to be used for compliance purposes, it must be able to 
distinguish dpm from other particles present in various mines, be 
accurate at the concentrations to be measured, and consistently measure 
dpm regardless of the mix or condition of the equipment in the mine.
    The technique being proposed for compliance sampling in underground 
metal and nonmetal mines meets these requirements. It involves sampling 
with a quartz fiber filter mounted in an open face filter holder, and a 
chemical analysis of the filter to determine the amount of carbon 
collected. The entire process, NIOSH Analytical Method 5040, has been 
validated as meeting NIOSH's accuracy criterion--i.e., that 
measurements come within 25% of the true concentration at least 95% of 
the time. While there are other methods that can be used to provide 
accurate measurements of diesel particulate matter in some types of 
mines and under some circumstances, this technique appears to provide 
consistent and accurate results in all underground metal and nonmetal 
mining environments.
    Although the NIOSH method was validated using a regular respirable 
dust sampler, MSHA gave consideration to the use of a size selector 
impactor sampler, developed by the Bureau of Mines, that would not 
collect any dust over 1 micrometer (micron) in diameter. Canada is 
exploring the use of such an approach with an alternative analytical 
method. However, measurements by the Agency to date indicate that in 
some underground metal and nonmetal mines, as much as 30% of the dpm 
present may be larger than 1 micron in size. The Agency is continuing 
to evaluate such an approach, and welcomes comments on the implications 
to miners and mine operators of excluding from consideration this 
larger fraction of dpm.
    The method described in NIOSH Analytical Method 5040 provides a way 
to determine the amount of diesel particulate in the sample. Diesel 
particulate consists of a core of elemental carbon onto which are 
adsorbed various organic components and sulfates. The NIOSH Analytical 
Method separately analyzes the amount of elemental carbon and the 
amount of organic carbon present in the sample. These two amounts are 
then added together to get the amount of total carbon present in the 
sample. In the absence of any measurable quantity of any other organic 
carbon source, this method provides a way of reliably measuring dpm at 
concentrations at and below the proposed final concentration limit.
    MSHA has also evaluated other analytical approaches--the 
gravimetric method (simply weighing the sample), the respirable 
combustible dust (RCD) analysis used in Canada, and the elemental 
carbon approach. As discussed in detail in Part II, use of these 
methods to measure dpm for compliance purposes in underground metal and 
nonmetal mines present various questions that the Agency has not been 
able to satisfactorily address at point in the rulemaking process. For 
example, the gravimetric method has not been validated for use at lower 
concentration levels, the RCD method is not recommended for use in 
certain types of underground metal and nonmetal mines, and there 
appears to be some variability in the relationship between elemental 
carbon and whole diesel particulate.
    MSHA does not believe that either oil mists or cigarette smoke in 
underground metal or nonmetal mines will pose a problem in using this 
method. MSHA currently has no data as to the frequency of occurrence or 
the magnitude of any

[[Page 58117]]

potential interference from oil mist, but during its studies of 
measurement methods in underground mines, MSHA has not encountered 
situations where oil mist was found to be an interferant. Moreover, the 
Agency assumes that when operators implement the proposal's maintenance 
requirements, this will minimize any remaining potential for such 
interference. Cigarette smoking can be prohibited by an operator during 
any testing. MSHA welcomes comments as to the scope of any possible 
interferences with the proposed methods and measures for addressing 
them.
    Proposed Sec. 57.5061(a) would explicitly provide that MSHA use the 
validated NIOSH procedure for total carbon, or ``any method 
subsequently determined by NIOSH to provide equal or improved 
accuracy'' in underground metal and nonmetal mines. Measurement 
technology is always improving, and MSHA believes that providing for 
some flexibility in this regard can ultimately benefit the entire 
mining community.
    Proposed Sec. 57.5061(b) provides that a single sample using the 
prescribed method would provide an adequate basis for citing 
noncompliance. As with the sampling methodology, MSHA is proposing to 
specifically state this policy as a provision of the rule itself to 
ensure it is clearly understood. Single shift sampling is the normal 
practice for OSHA and MSHA. As is its practice with other compliance 
determinations based on measurement, MSHA would not issue a citation 
unless the measurement exceeds the compliance limit by a ``margin of 
error'' sufficient to demonstrate noncompliance at a 95% confidence 
level. While MSHA is still conducting research to determine exactly 
what margin of error would be appropriate to establish such a 
confidence level, the Agency expects it to be between 10 and 20% of the 
concentration limit. Thus, assuming for the sake of example that the 
margin of error is 15%, a citation would not be issued for exceeding 
the final concentration limit unless the measured total carbon is above 
184TC g/m\3\ (115% of 160TC g/
m\3\).
    Finally, it should be noted that the proposed limit is expressed in 
terms of the average airborne concentration during each full shift 
expressed as an 8-hour equivalent. Measuring during the full shift 
ensures that the entire exposure is monitored, and the limit is based 
on the average exposure. Using an 8-hour equivalent ensures that a 
miner who works extended shifts would not have a higher exposure burden 
than a miner who works an 8-hour shift.
(13) Would the Concentration Limit Apply in All Areas of an Underground 
Metal or Nonmetal Mine?
    The concentration limit would apply only in underground areas where 
miners normally work or travel. The purpose of this restriction is to 
ensure that mine operators do not have to monitor particulate 
concentrations in areas where miners do not normally work or travel--
e.g., abandoned areas of a mine.
    However, it should be noted that the proposed interim and final 
concentration limits would apply in any area of a mine where miners 
``normally'' work or travel--not just where miners might be present at 
the moment.
(14) Does the Rule Contemplate That MSHA Use Area Sampling To Determine 
Compliance?
    The limit on the concentration of diesel particulate to which 
miners are exposed is intended to be applicable to persons, occupations 
or areas. This means that the Agency may sample by attaching a sampler 
to an individual miner, locate the sampler on a piece of equipment 
where a miner may work, or locate the sampler at a fixed site where 
miners normally work or travel.
(15) What Is the Basis for the Concentration Limit Being Proposed in 
Underground Metal and Nonmetal Mines?
    The proposed rule would seek to reduce exposures to dpm in 
underground areas of underground metal and nonmetal mines to a level of 
around 200DPM g/m\3\. (As explained in response to 
Question 12, the concentration limit is being expressed in terms of the 
total carbon measurement system MSHA will use to determine the amount 
of dpm, 160TC
g/m\3\).
    Look again at Figure I-1, which compares the range of exposures of 
different groups of workers. You can see that capping dpm 
concentrations at 200DPM g/m\3\ (all the 
information on the figure is presented in terms of estimated whole 
diesel particulate) will eliminate the worst mining exposures. In fact, 
such a cap will bring miner exposures down to a level commensurate with 
those reported for other groups of workers who use diesel-powered 
equipment. The proposed rule would not bring concentrations down as far 
as the proposed ACGIH TLVR of 150DPM g/
m\3\. Nor does MSHA's risk assessment suggest that the proposed rule 
would eliminate the significant risks to miners of dpm exposure.
    As a result of the Agency's statutory obligation to attain the 
highest degree of safety and health protection for miners, the Agency 
explored the option, and implications, of requiring mines in this 
sector to comply with a lower concentration limit than that being 
proposed. The Agency looked at simulations of the controls some 
underground metal and nonmetal mines might use to lower dpm 
concentrations, including at least one control with a major cost 
component (aftertreatment filter or new engine). The results, discussed 
in Part V of this preamble, indicate that although the matter is not 
free from question, it may not be feasible at this time for the 
underground metal and nonmetal mining industry as a whole to comply 
with a significantly lower limit than that being proposed. More 
information on this issue, and comments of the information presented by 
the Agency in Part V, would be appreciated.
    The other side of this question--whether the rule that is proposed 
is feasible for the underground metal and nonmetal mining industry--is 
discussed in the next Question and Answer.
(16) Is It Feasible for the Metal and Nonmetal Industry as a Whole To 
Comply with the Proposed Concentration Limit?
    MSHA has evaluated the feasibility of the concentration limit in 
the underground metal and nonmetal sector. Approximately 78 percent, of 
the 261 underground metal and nonmetal mines use diesel powered 
equipment, and MSHA estimates this sector has approximately 4,100 
diesel engines. The engines can be of large size, and so tend to have 
high emissions. Moreover, unlike in the coal sector, there is no single 
control device that can be readily and widely applied to reduce dpm 
emissions in underground metal and nonmetal mines. The paper filter 
aftertreatment devices that can eliminate up to 95% of particulate 
matter emissions from permissible coal equipment are not available here 
without the addition of other controls. Permissible equipment requires 
the exhaust to be cooled to avoid explosive hazards; in turn, this 
permits paper afterfilters to be installed directly without burning. 
For most metal and nonmetal equipment, it is necessary to first install 
water scrubbers or other devices to cool the exhaust before using the 
paper filters. There are other types of filtering devices that could be 
directly applied to this equipment, but none to date that is quite as 
effective (although MSHA is seeking information as to whether creation 
of a market for filters could lead to prompt commercial development of 
ceramic filters with

[[Page 58118]]

high particulate removal efficiencies). Moreover, the ventilation 
systems common in this sector, and the variation of mine types, 
suggested that a careful feasibility review is warranted.
    Accordingly, MSHA undertook special analyses in which the Agency's 
staff experts simulated how various control methods could be used to 
meet the needs of some mines expected to have unusually difficult 
problems: an underground limestone mine, an underground (and 
underwater) salt mine, and an underground gold mine. The results of 
these analyses are discussed in Part V of the preamble, together with 
the methodology used in modeling the results. In each case, the 
analysis revealed that there are available controls that can bring dpm 
concentrations down to well below the final limit--even when the 
controls that needed to be purchased were not as extensive as those 
which the Agency is assuming will be needed in determining the costs of 
the proposed rule. As a result of these studies, the Agency has 
tentatively concluded that, in combination with the required ``best 
practices'', there are engineering and work practice controls available 
to bring dpm concentrations in all underground metal and nonmetal mines 
down to 400TC g/m\3\ within 18 months. Moreover, 
based on the mines it has examined to date, MSHA has tentatively 
concluded that controls are available to bring dpm concentrations in 
all underground metal and nonmetal mines down to 160TC 
g/m\3\ within 5 years.
    The Agency would welcome comments from the mining community on the 
methodology of the model used in these studies, and hopes the mining 
community will submit the actual results of its own studies using the 
model. More information on the model is contained in Part V of the 
preamble. It uses a spreadsheet template that can be run on standard 
programs, and MSHA would be pleased to make copies available and answer 
any questions about the use of the model.
    The best actions for an individual operator to take to come into 
compliance with the interim and final concentration limits will depend 
upon an analysis of the unique conditions at the mine. The proposed 
rule provides 18 months after it is promulgated for MSHA to provide 
technical assistance to individual mine operators. It also gives all 
mine operators in this sector an additional three and a half years to 
bring dpm concentrations down to the proposed final concentration 
limit--using an interim concentration limit during this time which the 
Agency is confident every mine in this sector can timely meet. And the 
rule provides an opportunity for a special extension for an additional 
two years for mines that have unique technological problems meeting the 
final concentration limit.
    As noted during 1995 workshops co-sponsored by MSHA on methods for 
controlling diesel particulate, many underground metal and nonmetal 
mine operators have already successfully determined how to reduce 
diesel particulate concentrations in their mines. MSHA has disseminated 
the ideas discussed at these workshops to the entire mining community 
in a publication, ``Practical Ways to Control Exposure to Diesel 
Exhaust in Mining--a Toolbox'' (a copy of this publication is appended 
to the end of this document). The control methods are divided into 
eight categories: use of low emission engines; use of low sulfur fuel; 
use of aftertreatment devices; use of ventilation; use of enclosed 
cabs; diesel engine maintenance; work practices and training; fleet 
management; and respiratory protective equipment. And as noted above, 
MSHA has designed a model in the form of a computer spreadsheet that 
can be used to simulate the effects of various controls on dpm 
concentrations. This model is discussed in Part V of the preamble, and 
several examples are provided. This makes it possible for individual 
underground mine operators to evaluate the impact on diesel particulate 
levels of various combinations of control methods, prior to making any 
investments, so each can select the most feasible approach for his or 
her mine.
(17) Suppose an Underground Metal or Nonmetal Mine Really Does Have a 
Unique Technological Problem That Precludes Timely Compliance? Will 
MSHA Utilize Qualified and Experienced Technical Personnel To Review 
Operator Applications for Special Extensions of Time To Comply With the 
Final Concentration Limit in Underground Metal and Nonmetal Mines?
    It is MSHA's intent that primary responsibility for analysis of the 
operator's application for a special extension will rest with MSHA's 
district managers. District managers are the most familiar with the 
conditions of mines in their districts, and have the best opportunity 
to consult with miners as well. At the same time, MSHA recognizes that 
district managers may need assistance with respect to the latest 
technologies and solutions being used in similar mines elsewhere in the 
country. Accordingly, the Agency intends to establish within its 
Technical Support directorate in Arlington, Va., a special panel to 
consult on these issues, to provide assistance to district managers, 
and to give final approval of any application for a special extension.
(18) If a Special Extension of Time To Comply With the Final dpm 
Concentration Limit Is Approved for an Underground Metal or Nonmetal 
Mine, What Operating Parameters Would Be Imposed on That Mine during 
the Duration of the Special Extension?
    Any parameters will be negotiated between the individual operator 
and MSHA.
    An operator will begin the process by filing an application for a 
special extension. The application must set forth what actions the 
operator commits to taking to maintain the lowest concentration of 
diesel particulate achievable. The application must also include 
adequate information for the Secretary to ascertain the lowest 
concentration of diesel particulate achievable, as demonstrated by data 
collected under conditions that are representative of mine conditions 
using the total carbon sampling method. In addition, the application 
must set forth what actions the operator will take to minimize the 
exposure of miners who will have to work or travel in areas which are 
going to be above the concentration limit by virtue of the extension. 
Since administrative controls and personal protective equipment can 
help reduce miner exposure, under these special circumstances operators 
may propose to include use of these approaches in their applications.
    In some cases, what may be involved is a small area with only 
limited miner access; in other cases, an entire working section may be 
involved. Rather than establish ``one-size-fits-all'' standards for 
such situations, the proposal leaves it to the operator to submit a 
suggested approach.
    The proposed rule requires a mine operator to comply with the terms 
of an approved extension application, and a copy would be posted at the 
mine site. Failure to comply with the specific commitments agreed to as 
part of the extension, and contained therein, would thus be citable.
(19) Why Do Underground Metal and Nonmetal Mine Operators Have To Have 
a Diesel Particulate Control Plan?
    Underground metal and nonmetal operators will not have to have a 
compliance plan if they are in compliance. Considerable time is 
provided under the proposed rule to come into compliance, and operators 
can thereafter monitor their mines to

[[Page 58119]]

ensure they stay below the required concentration limit.
    But some operators may decline to take the actions necessary to 
achieve compliance in a timely manner, and others may need to rethink 
their approaches from time to time as equipment changes increase dpm 
concentration levels. Providing for a control plan in the event of a 
violation of the concentration limit ensures that there is a 
deliberative effort as to how to solve the dpm concentration problem, 
and that everybody understands what is going to be done to eliminate 
it. Accordingly, proposed Sec. 57.5062 requires that in the event an 
operator is determined to have exceeded the applicable limit on diesel 
particulate concentration, the operator must establish a diesel 
particulate control plan if one is not already in effect, or modify the 
existing diesel particulate control plan.
(20) Must dpm Control Plans in Metal and Nonmetal Mines Be Pre-Approved 
by MSHA? How Long Would They Last?
    Operator control plans would NOT have to be approved by MSHA. This 
is consistent with the practice in this sector concerning ventilation 
plans (with which the dpm control plan may be combined). The Agency 
gave serious consideration to requiring approval of such plans to 
ensure there was agreement as to their effectiveness, or at least to 
approval of compliance plans for repeat violators; but in light of the 
resource demands this might impose on the agency, and the operator 
verification sampling built into the proposed rule, the Agency decided 
not to make such a proposal. Comment on this point is welcome.
    A control plan for a metal or nonmetal mine would not need to be 
retained and modified forever--as is the practice with plans for 
underground coal mines. Rather, under the proposal, a dpm control plan 
in a metal or nonmetal mine would stay in effect for 3 years, and 
during its lifetime, the plan is to be modified as appropriate to 
reflect changes in mining conditions.
    MSHA seriously considered requiring a longer lifetime for 
compliance plans. First, the Agency wants to provide a strong incentive 
to come into compliance in a timely fashion. Second, the Agency wants 
to be sure that where a plan is needed to clarify compliance 
obligations, it stay in place at a mine long enough to ensure that the 
obligations undertaken in the plan become a mine routine; the goal is 
to maintain a mine in compliance, not just have a temporary fix. The 
Agency also has to be realistic about conserving the resources of its 
health professionals; re-sampling mines whose control plans have 
expired takes resources away from other priorities. The Agency is 
aware, however, that operating under long-term control plans is not 
standard practice in metal and nonmetal mines. Moreover, it recognizes 
the need to re-sample all mines with some regularity due to changing 
mining conditions. Accordingly, the proposed rule seeks to strike a 
balance in this regard.
(21) What Must Be Included in a dpm Control Plan If One Is Required? 
And How Would Its Effectiveness Be Verified?
    The diesel particulate control plan would include three elements: 
the controls the operator will utilize to maintain the concentration of 
diesel particulate at the mine to the applicable limit; a list of 
diesel-powered units maintained by the mine operator; and information 
about any unit's emission control device and the parameters of any 
other method used to control dpm concentrations. Upon request, the plan 
(or amended plan) is to be submitted to the District Manager, with a 
copy to the authorized representative of miners--but no approval 
process would be required; a copy is to be maintained at the mine site. 
Documentation verifying the effectiveness of the plan in controlling 
diesel particulate to the required level would have to be maintained 
with the plan, and submitted to MSHA upon request.
    Proposed Sec. 57.5062(c) provides that to verify the effectiveness 
of a control plan or amended control plan, operators must have 
monitoring data, collected using the total carbon method which MSHA 
will be required to use for enforcement purposes, sufficient to confirm 
that the plan or amended plan will control the concentration of diesel 
particulate to the applicable limit under conditions that can be 
reasonably anticipated in the mine.
    Verification by operators is being proposed to ensure that primary 
responsibility for ensuring a dpm control plan is effective is not 
shifted to MSHA. The Agency has only limited resources to conduct 
sampling. Moreover, while a single sample can demonstrate that a mine 
is out of compliance under the conditions sampled, it takes multiple 
samples to demonstrate that miners are protected under the variety of 
conditions that can be reasonably anticipated in the mine (e.g., during 
production and seasonal changes). By clarifying operator 
responsibilities in this regard, the proposal ensures an appropriate 
balance of responsibilities.
    The proposed rule does not specify that any defined number of 
samples must be taken--the intent is that the sampling provide a 
representative picture of whether the plan or amended plan is working. 
The proposed rule does, however, specify that the total carbon method 
be used for verification sampling. This is an exception to the general 
rule that mine operators have discretion in the choice of what sampling 
technique to use in their own monitoring programs (see response to 
Question 29). The purpose of verification sampling is to verify the 
effectiveness of a plan established or modified in response to a 
violation through MSHA sampling; if operators used an alternative 
technique to sample, it would complicate the determination of whether 
the violation was being adequately addressed by the plan.
(22) Why Is the Agency Proposing That All Underground Metal and 
Nonmetal Mines Follow Certain ``Best Practices''--Regardless of the 
Concentration of Diesel Particulates at Such Mines?
    The Agency's risk assessment supports reduction of dpm to the 
lowest level possible. But as discussed in response to Question 16, 
feasibility considerations dictated proposing a concentration limit 
that does not eliminate the significant risks that dpm exposure poses 
to miners.
    One approach that can be used to bridge the gap between risk and 
feasibility is to establish an ``action level''. In the case of MSHA's 
noise proposal, for example, MSHA proposed a ``permissible exposure 
level'' of a time-weighted 8-hour average (TWA8) of 90 dBA 
(decibels, A-weighted), and an ``action level'' of half that amount--a 
TWA8 of 85 dBA. In that case, MSHA has determined that 
miners are at significant risk of material harm at a TWA8 of 
85 dBA, but technological and feasibility considerations may preclude 
the industry as a whole, at this time, from eliminating exposures below 
a TWA8 90 dBA. Accordingly, MSHA proposed that mine 
operators must take certain actions to limit miner exposure to noise 
above a TWA8 of 85 dBA that are feasible (e.g., provide 
hearing exams and hearing protectors).
    MSHA considered the establishment of a similar ``action level'' for 
dpm--probably at half the proposed concentration limit, or 
80TC g/m3. Under such an approach, mine 
operators whose dpm concentrations are above the ``action level'' would 
be required to implement a series of ``best practices''--e.g., limits 
on fuel types, idling, and engine maintenance. MSHA welcomes comments 
on whether it

[[Page 58120]]

should take such an approach with dpm.
    In lieu of this approach, the Agency decided instead to propose an 
approach that it believes will be simpler for the mining community to 
implement: requiring compliance with the ``best practices'' in all 
cases. There are several reasons why the agency has proposed this 
approach.
    First, sampling by both operators and MSHA would have to be much 
more frequent if a measurement trigger for additional actions were to 
be established. This is because many more areas of a mine would need to 
be checked regularly than if only a higher trigger is in place. In 
underground metal and nonmetal mines, most areas using diesel equipment 
would exceed a limit of 75TC g/m3 
anyway, so the sampling needed to confirm the situation would appear to 
be wasteful.
    Second, diesel equipment is often moving, meaning that maintenance 
and fleet requirements triggered by a single sample might switch on and 
off in ways that are hard to predict. Moreover, using an action level 
in an area of a mine to trigger maintenance requirements might put 
certain machines in the fleet under one set of maintenance rules and 
other machines under an alternative set, complicating mine 
administration.
    Third, underground coal mines which use diesel-powered equipment 
already observe a set of such requirements. While certain special 
safety hazards associated with the use of diesel-powered equipment in 
underground coal mines warrant certain work practices that may not be 
warranted in other sectors, the safety rationale for adopting some of 
these practices seems as valid in other sectors as in underground coal. 
Fourth, given the history of the mining industry with lung problems 
associated with this type of work, adopting a prudent approach seems a 
wise course when the costs of prevention are limited. This is standard 
health practice.
    Finally, a number of the work practices proposed appear to have 
significant benefits--improving the efficiency of mining operations by 
ensuring that diesel mining equipment is maintained in good working 
order to meet productivity demands.
    MSHA specifically solicits comments from the public on whether or 
not it should require ``best practices'' to lower the dpm 
concentration.
(23) Will the Proposed Restrictions on Fuel and Fuel Additives Increase 
Costs or Limit Engine Reliability?
    MSHA believes the answer to both questions is no.
    Under proposed Sec. 57.5065, mine operators would be able to use 
only low-sulfur diesel fuel. This requirement is identical to that for 
underground coal diesel equipment. Number 1 and number 2 diesel fuel 
would be permitted. MSHA has been advised that low-sulfur diesel fuel 
is now readily available in all areas of the country in order to meet 
EPA requirements; in many places, it is the only fuel available.
    Similarly, the proposal would extend to all mines the ban in 
underground coal mines on the use of diesel-fuel additives other than 
those approved by EPA. There is a long list of approved additives. 
Copies are available from EPA and the list is posted on its Web site, 
or you may link to them from MSHA's Web site (http://www.msha.gov/
s&hinfo/deslreg/1901(c).htm). Using only additives that have been 
approved ensures that diesel particulate concentrations are not 
inadvertently increased, while also protecting miners against the 
emission of other toxic substances.
(24) How Is MSHA Going To Distinguish Between Idling That Is Permitted 
and Idling That Isn't Permitted?
    Keeping idling to a minimum is a very important way to reduce 
pollution in mine atmospheres, and this would be required by proposed 
Sec. 57.5065(c). Idling engines can actually produce more pollutants 
than engines under load. Generally of more concern, however, is the 
impact idling engines can have on localized exposures. In underground 
operations, an engine idling in an area of minimal ventilation or a 
``dead air'' space could cause an excess exposure to the gaseous 
emissions, especially carbon monoxide, as well as to diesel 
particulate. Eliminating unnecessary idling can make a substantial 
contribution toward preventing localized exposure to high particulate 
concentrations.
    However, there are some circumstances in which idling is necessary. 
The proposal would permit idling in connection with ``normal mining 
operations''. In the proposal, MSHA does not attempt to define this 
term, and would intend this rule to be administered with reference to 
commonly understand practices of what is necessary idling. For example, 
idling while waiting for a load to be unhooked, or waiting in line to 
pick up a load, is normally part of the job; idling while eating lunch 
is normally not part of the job. But if the idling is necessary due to 
the very cold weather conditions, it should not be barred. On the other 
hand, idling should not be permitted in other weather conditions just 
to keep balky older engines running; in such cases, the correct 
approach is better maintenance. MSHA recognizes that to administer this 
provision in a common sense manner may require the provision of 
examples to both MSHA inspectors and to the mining community; 
accordingly, the Agency welcomes specific examples of circumstances 
where idling should and should not be permitted. The Agency recently 
implemented a similar provision for the underground coal mining sector, 
and MSHA will consider the experience gained under that rule in 
formulating a final diesel particulate rule and compliance guide.
(25) Will the Proposed Rule Require That Diesel Engines and 
Aftertreatment Devices Used in Underground Metal and Nonmetal Mines Be 
Maintained in Mint Condition?
    No. Sec. 57.5066(a) of the proposed rule would, however, require 
that the engines and aftertreatment devices not be permitted to 
deteriorate to the point they create needless pollution. The air intake 
system, the cooling system, lubrication system, fuel injection system 
and exhaust system of an engine must all be maintained on a regular 
schedule if the toxic contaminants in the engine exhaust are to be 
minimized. And there is little point in having an aftertreatment device 
to limit pollution if it is not maintained in working order; moreover, 
it can damage the engine. A good preventive maintenance program can not 
only keep down exhaust emissions, but help maximize vehicle 
productivity and engine life.
    It is difficult for a rule covering all types and ages of engines 
used in underground metal and nonmetal mines to define precisely the 
level of maintenance required for each engine. Further, MSHA does not 
believe that it is necessary: the mining community is fully cognizant 
of the general requirements for engine maintenance. Accordingly, 
proposed Sec. 57.5066(a) sets out in general terms the standard of care 
required for different types of engines.
    First, an ``approved'' engine is to be maintained in approved 
condition. MSHA approves engines under specific regulations set forth 
in Title 30. The approval of the engine is tied to certain parts and 
specifications. When these parts or specifications are changed (e.g., 
an incorrect part is used, or the wrong setting), then the engine is no 
longer considered in approved condition. The requirements in this 
regard are well defined. MSHA personnel at the Approval Certification 
Center are

[[Page 58121]]

available to the mining community to respond to questions and provide 
specific guidance. MSHA's diesel equipment rule already requires 
underground coal mine fleets to convert entirely to approved engines, 
but at this time only some of the engines used in underground metal and 
nonmetal mines are approved.
    Second, for any engine that is not an approved engine, the 
``emission related components'' of the engine are to be maintained to 
manufacturer specifications. By the term ``emission related 
components,'' MSHA means the parts of the engine that directly affect 
the emission characteristics of the raw exhaust. These are basically 
the same components which MSHA examines for ``approved'' engines. They 
are: the piston; intake and exhaust values; cylinder head; camshaft; 
injector; fuel injection pump; governor; injection timing and fuel pump 
calibration; and, if applicable, turbocharger and after cooler.
    Third, and finally, any emission or particulate control device 
installed on diesel-powered equipment is to be maintained in 
``effective operating condition.'' The maintenance of an emission or 
particulate control device in effective operating condition involves 
such basic tasks as regularly cleaning the filter using whatever 
methods are recommended by the manufacturer for that purpose or 
inserting appropriate replacement filters, checking for and repairing 
any leaks, and similar obvious actions.
    An MSHA inspector is not going to randomly order an engine to be 
taken out of service and torn down to check the condition of a piston 
against the shop manual. Rather, what will concern an inspector are the 
same kinds of signals that should concern a conscientious operator--for 
example, a history of complaints about the engine's reliability, an 
incomplete maintenance schedule, lack of required maintenance manuals 
or spare parts, the emission of black smoke under normal load, or a 
series of emission test results indicating a continuing engine problem. 
Evidence of such deficiencies is likely to lead to a closer 
examination. But a conscientious maintenance program is going to catch 
such problems before they occur.
    MSHA's toolbox includes an extensive discussion of maintenance. It 
reminds operators and diesel maintenance personnel of the basic systems 
on diesel engines that need to be maintained, and how to avoid various 
problems. It includes suggestions from others in the mining community, 
and information on their success or difficulties in this regard. MSHA 
will continue to provide technical assistance to the mining community 
in this critical area.
(26) What Are the Responsibilities of a Miner Who Operates Diesel-
Powered Equipment in an Underground Metal and Nonmetal Mine To Ensure 
it Is Not Polluting? And What Are The Responsibilities of Mine 
Management When Notified of a Potential Pollution Problem?
    The miner who operates diesel-powered equipment is often the first 
one to spot a problem with the engine or emissions system. The engine 
may balk, have trouble handling a load, make unusual noises, exhaust 
too much smoke, or otherwise suggest to the person familiar with the 
engine's capabilities that it needs to be checked. In some cases, the 
miner may have the knowledge, parts, equipment and authority to fix the 
problem on the spot. In many cases, however, the miner operating the 
equipment may not have all of these. If the problem is to be addressed 
promptly, it is essential the miner report it to mine management--and 
that the mine management act on that report in a timely manner. If 
these actions by miner and mine management are not taken, the 
concentrations of diesel particulate are likely to quickly increase 
without anyone being aware of the danger until the next environmental 
monitoring is performed. To avoid this problem, proposed Sec. 57.5066 
would require that all underground metal and nonmetal mines using 
diesel equipment underground implement a few basic procedures. The 
details of implementation in each mine would be at the discretion of 
the mine operator.
    Proposed Sec. 57.5066(b)(1) would require the mine operator to 
authorize the operator of diesel-powered equipment to affix a tag to 
the equipment at any time the equipment operator notes a potential 
problem. Tagging provides a simple mechanism for ensuring that all mine 
personnel are made quickly aware that a piece of equipment needs to be 
checked by qualified service personnel. The tag may be affixed because 
the equipment operator picks up a problem through a visual exam 
conducted before the equipment is started (e.g., an exam pursuant to 30 
CFR 57.14100), or because of a problem that comes to the attention of 
the equipment operator during mining operations--e.g., black smoke 
while the equipment is under normal load, rough idling, unusual noises, 
backfiring, etc.
    The proposal leaves the design of the tag to each mine operator, 
provided that the tag can be dated. Comments are welcome on whether 
some or all elements of the tag should be standardized to ensure its 
purpose is met.
    MSHA is not proposing that equipment tagged for such potential 
emission problems be automatically taken out of service. The proposal 
is not, therefore, directly comparable to a ``tag-out'' requirement 
like OSHA's requirement for automatically powered machinery, nor as 
stringent as MSHA's requirement to remove from service certain 
equipment ``when defects make continued operation hazardous to 
persons'' (see, e.g., 30 CFR 57.14100). While the emissions problem 
could pose a serious health hazard for miners directly exposed, there 
is no way to determine this with certainty until the equipment is 
tested. Moreover, the danger is not as immediate as, for example, an 
explosive hazard. Rather, proposed Sec. 57.5066(b)(2) would require 
that the equipment be ``promptly'' examined by a person authorized by 
the mine operator to maintain diesel equipment (the qualifications for 
those who maintain and service diesel engines discussed in response to 
the next question). The Agency has not tried to define the term 
``promptly'', but welcomes comment on whether it should do so--in 
terms, for example, of a limited number of shifts.
    The proposal would require that a single log be retained of all 
equipment tagged. The proposal would permit a tag to be removed after 
an examination has been completed and a record of the examination 
made--with the date, the name of the person making the examination, and 
the action taken as a result of the examination. The presence of a tag 
serves as a caution sign to miners working near the equipment, as well 
as a reminder to mine management, as the equipment moves from task to 
task throughout the mine. While the equipment is not barred from 
service, operators would be expected to use common sense in using it in 
locations in which diesel particulate concentrations are known to be 
high. The records of the tagging and servicing, although basic, provide 
mine operators, miners and MSHA a history that will help all of them 
evaluate whether a maintenance program is being effectively 
implemented.

[[Page 58122]]

(27) Must Miners or Others Who Examine or Repair Diesel Engines Used in 
Underground Metal and Nonmetal Mines Have Special Qualifications or 
Training? Must Operators Establish Programs or Criteria for This 
Purpose?
    The answer to the first question is a qualified ``yes'', and the 
answer to the second question is no.
    Proposed Sec. 57.5066(c) provides that: ``Persons authorized by a 
mine operator to maintain diesel equipment covered by paragraph (a) of 
this section must be qualified, by virtue of training or experience, to 
ensure that the maintenance standards of paragraph (a) of this section 
are observed.'' As discussed in response to Question 25, paragraph (a) 
of Sec. 57.5066 provides that approved engines be maintained in 
approved condition, the emission related components of non-approved 
engines be maintained to manufacturer specifications, and emission or 
particulate control devices installed on the equipment be maintained in 
effective condition.
    This means that regardless of who identifies a potential problem 
along these lines, the person who checks out the problem, and if 
necessary makes repairs, is someone who knows what he or she is doing. 
If examining and, if necessary, changing a filter or air cleaner is 
what is needed, a miner who has been shown how to do these tasks would 
be ``qualified by virtue of training or experience'' to do those tasks. 
For more sophisticated work, more sophisticated training or additional 
experience would be required. Training by a manufacturer's 
representative, completion of a general diesel engine maintenance 
course, or practical experience performing such repairs might be 
evidence of appropriate qualifications.
    In the underground coal sector, MSHA requires each operator to 
establish a program to ensure that persons who work on diesel engines 
are qualified. That is not being proposed for the underground metal and 
nonmetal sector. The unique conditions in underground coal mines 
require the use of specialized equipment. Accordingly, the 
qualifications of the persons who maintain this equipment generally 
must be more sophisticated than in other sectors.
    The proposed rule contemplates that if MSHA finds a situation where 
maintenance appears to be shoddy or where tampering has damaged engine 
approval status or emission control effectiveness, MSHA will ask the 
operator to provide evidence that the person who worked on the 
equipment was properly qualified by virtue of training or experience. 
Equipment sent off site for maintenance and repair is just as subject 
to this requirement as other equipment; it is the operator's obligation 
to ensure he has appropriate evidence of the qualifications of those 
who will work on the equipment.
(28) Can Underground Metal and Nonmetal Operators Continue To Use and 
Relocate Nonapproved Engines in Their Inventories?
    Pursuant to MSHA's diesel equipment rule, the entire fleet of 
underground coal engines must be ``approved'' engines by the year 
2000--even if operators must replace existing engines to comply. By 
contrast, proposed Sec. 57.5067 would only require that, with a few 
exceptions, all engines ``introduced'' into underground areas of 
underground metal and nonmetal mines after the effective date must be 
engines that have been through MSHA's approval process under Part 7 of 
Chapter 30. Operators who have significant investments in their 
existing fleets will accordingly be able to retain those engines, 
provided they are maintained in the manner specified in the proposal 
and that the concentration of diesel particulate can be controlled in 
another way (e.g. ventilation, particulate filters, etc.).
    However, after the rule's effective date, an operator would not be 
permitted to bring into underground areas of a mine an unapproved 
engine from the surface area of the same mine, an area of another mine, 
or from a non-mining operation. Since the safe level of diesel 
particulate is not known, promoting a gradual turnover of the existing 
fleet is an appropriate response to the health risk presented.
    Some engines currently used in metal and nonmetal mines may have no 
approval criteria; in such cases, MSHA will work with the manufacturers 
to develop approval criteria consistent with those MSHA uses for other 
diesel engines. Based upon preliminary analysis, MSHA has tentatively 
concluded that any diesel engine meeting current on-highway and non-
road EPA emission requirements would meet MSHA's engine approval 
standards of Part 7, subpart E, category B type engine. (See Section 4 
of Part II of this preamble for further information about these 
engines). Currently, the EPA nonroad test cycle and MSHA's test cycle 
are the same for determining the gaseous and particulate emissions. 
MSHA envisions being able to use the EPA test data ran on the non-road 
test cycle for determining the gaseous ventilation rate and particulate 
index. The engine manufacturer would continue to submit the proper 
paper work for a specific model diesel engine to receive the MSHA 
approval. However, engine data ran on the EPA on-highway transient test 
cycle would not as easily be usable to determine the gaseous 
ventilation and particulate index. Comments on how MSHA can facilitate 
review of engines not currently approved would be welcome.
    Engines in diesel-powered ambulances and fire-fighting equipment 
would be exempted from these requirements. This exemption is identical 
with that in the rule for diesel-powered equipment in underground coal 
mines.
(29) What Specifically Would Be the Obligations of an Underground Metal 
or Nonmetal Mine Operator To Monitor dpm Exposures and to Correct 
Overexposures?
    Proposed Sec. 57.5071 would require underground metal or nonmetal 
mine operators to monitor the concentration of diesel particulate, to 
initiate corrective action by the next work shift if the monitoring 
reveals that the concentration of diesel particulate exceeds the 
permitted limit, and to post sample results and the corrective action 
being taken.
    There is no prescribed frequency for monitoring. But proposed 
Sec. 57.5071(a) provides that sampling must be done as often as 
necessary to ``effectively evaluate,'' under conditions that can be 
reasonably anticipated in the mine:
    (1) whether the dpm concentration in any area of the mine where 
miners work or travel exceeds the applicable limit; and (2) the average 
full shift airborne concentration at any location or on any person 
designated by MSHA. The first condition clarifies that it is the 
responsibility of mine operators to be aware of the concentrations of 
diesel particulate in all areas of the mine where miners work or 
travel, so as to know whether action is needed to ensure that the 
concentration does not exceed the applicable limit. The second 
condition is to ensure special attention to locations or persons known 
to MSHA to have a significant potential for overexposure to diesel 
particulate.
    The proposed rule is performance oriented in that the regularity 
and methodology used to make this evaluation are not specified. MSHA's 
own measurements will assist the Agency in verifying the effectiveness 
of an operator's monitoring program. If an operator is ``effectively 
evaluating'' the concentration of dpm at designated locations, for 
example, MSHA would not expect to record concentrations above the limit 
when it samples at that

[[Page 58123]]

location. Some record of the sampling procedure and sample results will 
need to be retained by operators to establish that they have complied 
with the general obligations of this section.
    The proposed rule requires, consistent with Section 103(c) of the 
Mine Act, that miners and their representatives have an opportunity to 
observe such monitoring. In accordance with this legal requirement, the 
proposed rule requires a mine operator to provide affected miners and 
their representatives with an opportunity to observe exposure 
monitoring of dpm by operators. Mine operators must give prior notice 
to affected miners and their representatives of the date and time of 
intended monitoring. MSHA has proposed similar language in its proposed 
rule on noise.
    The proposed rule does not specify a required method for sampling. 
In the absence of a procedure to convert total carbon measurements into 
equivalents under other methods, methods other than NIOSH Method 5040 
would not provide exact information about compliance status, but they 
certainly would provide a general guide to dpm concentrations if used 
under proper circumstances. (More information on the proper 
circumstances in which various methods are appropriate can be found in 
Section 3 of Part II of this preamble).
    The proposed rule provides that an operator who has knowledge that 
a concentration limit has been exceeded must initiate corrective action 
by the next work shift and promptly complete such action. The hazards 
presented by overexposure to dpm may not as immediate as an explosive 
hazard, but are nevertheless serious. Accordingly, although MSHA is not 
proposing immediate withdrawal of miners nor even immediate completion 
of abatement action, the agency is proposing that mine operators begin 
abatement action by the next shift and promptly complete such action, 
not allowing it to drag out while miners are being overexposed. The 
Agency is also proposing to require posting of the corrective action to 
implement the statutory requirement that notice of corrective action be 
provided to miners. MSHA welcomes comment on how it might clarify its 
expectations with respect to the initiation of corrective action, 
including what specific guidance to provide to operators not using the 
total carbon method and as to when corrective action must begin when 
the analysis is performed on a delayed basis off-site. MSHA also 
welcomes comment as to whether personal notice of corrective action 
would be more appropriate than posting given the health risks involved.
    Proposed Sec. 57.5071(d) provides that monitoring results must be 
posted on the mine bulletin board, and a copy provided to the 
authorized representative of miners. As with the training requirements, 
posting ensures that miners are kept aware of the hazard so they can 
actively play their role in prevention.
(30) What Records Must be Kept by Metal and Nonmetal Operators? Where 
Must they be Kept, and Who Has Access to Them?
    Recordkeeping and retention requirements are noted in the text of 
each section of the proposed rule creating the requirement. For the 
sake of convenience, a table of record-keeping requirements is provided 
in proposed Sec. 57.5075(a). The table lists the records that would be 
required under the proposed changes to Part 57, notes the proposed 
section of Part 57 creating the recordkeeping requirement, and notes 
the type of record and retention time. MSHA would welcome comment on 
whether this presentation is useful.
    In some cases, the record required is expressed in general terms: 
e.g., ``evidence of competence to perform maintenance'', pursuant to 
proposed Sec. 57.5066(c). As long as each operator has some record that 
establishes this fact, it does not matter that the records of one 
operator are not the same as the records of another operator. While an 
MSHA inspector may well be willing to accept oral evidence on a 
particular point (e.g., who performed a repair), operators should 
retain written documentation adequate to demonstrate the facts involved 
(e.g., a logbook for each engine showing who worked on it, the date, 
the work performed, and any follow-up needs or plans). MSHA would 
welcome comments on whether the agency should be more specific as to 
the recordkeeping systems mine operators should utilize.
    The proposed rule generally provides that records required be 
retained at the mine site. These records need to be where an inspector 
can view them during the course of an inspection, as the information in 
the records may determine how the inspection proceeds. But if the mine 
site has an operative fax machine or computer terminal, this section 
would permit the records to be maintained elsewhere. MSHA's approach in 
this regard is consistent with Office of Management and Budget Circular 
A-1. Mine operators must promptly provide access to compliance records 
upon request from an authorized representative of the Secretary of 
Labor, the Secretary of Health and Human Services, or from the 
authorized representative of miners. Access to a miner's sample records 
must also be provided to a miner, former miner, or personal 
representative of a miner--the first copy at no cost, and any 
subsequent copies at reasonable cost.
    MSHA encourages mine operators who store records electronically to 
provide a mechanism which will allow the continued storage and 
retrieval of records in the year 2000.

II. Background Information.

    This part provides the context for this rulemaking. The nine topics 
covered are:
    (1) The role of diesel-powered equipment in mining;
    (2) Diesel exhaust and diesel particulate;
    (3) Methods available to measure dpm;
    (4) Reducing soot at the source--engine standards;
    (5) Limiting the public's exposure to soot--ambient air quality 
standards;
    (6) Controlling diesel particulate emissions in mining--a Toolbox;
    (7) Existing mining standards that limit miner exposure to 
occupational diesel particulate emissions;
    (8) How other jurisdictions are restricting occupational exposure 
to diesel soot; and
    (9) MSHA's initiative to limit miner exposure to diesel 
particulates--the history of this rulemaking and related actions.
    In addition, a recent MSHA publication, ``Practical Ways to Reduce 
Exposure to Diesel Exhaust in Mining--A Toolbox'', contains 
considerable information of interest in this rulemaking. The 
``Toolbox'' which includes additional information on methods for 
controlling dpm, and a glossary of terms, is appended to the end of 
this document.
    These topics will be of interest to the entire mining community, 
even though this rulemaking is specifically confined to the underground 
metal and nonmetal sector.
    (1) The Role of Diesel-Powered Equipment in Mining. Diesel engines 
now power a full range of mining equipment on the surface and 
underground, in both coal and in metal/nonmetal mining. Many in the 
mining industry believe that diesel-powered equipment has a number of 
productivity and safety advantages over electrically-powered equipment. 
Nevertheless, concern about miner safety and health has slowed the 
spread of this technology, and in certain states resulted in a complete 
ban on its use in

[[Page 58124]]

underground coal mines. As the industry has moved to realize the 
advantages this equipment may provide, the Agency has endeavored to 
address the miner safety and health issues presented.
    Historical Patterns of Use. The diesel engine was developed in 1892 
by the German engineer Rudolph Diesel. It was originally intended to 
burn coal dust with high thermodynamic efficiency. Later, the diesel 
engine was modified to burn middle distillate petroleum (diesel fuel). 
In diesel engines, liquid fuel droplets are injected into a prechamber 
or directly into the cylinder of the engine. Due to compression of air 
in the cylinder the temperature rises high enough in the cylinder to 
ignite the fuel.
    The first diesel engines were not suited for many tasks because 
they were too large and heavy (weighing 450 lbs. per horsepower). It 
was not until the 1920's that the diesel engine became an efficient 
lightweight power unit. Since diesel engines were built ruggedly and 
had few operational failures, they were used in the military, railway, 
farm, construction, trucking, and busing industries. The U.S. mining 
industry was slow, however, to begin using these engines. Thus, when in 
1935 the former U.S. Bureau of Mines published a comprehensive overview 
on metal mine ventilation (McElroy, 1935), it did not even mention 
ventilation requirements for diesel-powered equipment. By contrast, the 
European mining community began using these engines in significant 
numbers, and various reports on the subject were published during the 
1930's. According to a 1936 summary of these reports (Rice, 1936), the 
diesel engine had been introduced into German mines by 1927. By 1936, 
diesel engines were used extensively in coal mines in Germany, France, 
Belgium and Great Britain. Diesel engines were also used in potash, 
iron and other mines in Europe. Their primary use was in locomotives 
for hauling material.
    It was not until 1939 that the first diesel engine was used in the 
United States mining industry, when a diesel haulage truck was used in 
a limestone mine in Pennsylvania. In 1946 diesel engines were 
introduced in coal mines. Today, however, diesel engines are used to 
power a wide variety of equipment in all sectors of U.S. mining, such 
as: air compressors; ambulances; crane trucks; ditch diggers; foam 
machines; forklifts; generators; graders; haul trucks; load-haul-dump 
machines; longwall retrievers; locomotives; lube units; mine sealant 
machines; personnel cars; hydraulic pump machines; rock dusting 
machines; roof/floor drills; shuttle cars; tractors; utility trucks; 
water spray units and welders.
    Estimates of Current Use. Estimates of the current inventory of 
diesel engines in the mining industry are displayed in Table II-1. Not 
all of these engines are in actual use. Some may be retained rather 
than junked, and others are spares. MSHA has been careful to take this 
into account in developing cost estimates for this proposed rule; its 
assumptions in this regard are detailed in the Agency's PREA.

          Table II-1.--Diesel Equipment in Three Mining Sectors
------------------------------------------------------------------------
                                                 # Mines w/
            Mine type              # Mines \2\     diesel     # Engines
------------------------------------------------------------------------
Underground Coal.................          971      \3\ 173    \4\ 2,950
    Small \1\....................          426           15           50
    Large........................          545          158        2,900
Underground M/NM.................          261       203\5\    \6\ 4,100
    Small \1\....................          130           82          625
    Large........................          131          121        3,475
Surface Coal.....................        1,673    \7\ 1,673   \8\ 22,000
    Small \1\....................        1,175        1,175        7,000
    Large........................          498          498       15,000
Surface M/NM.....................       10,474   \9\ 10,474  \10\ 97,000
------------------------------------------------------------------------
Notes on Table II-1:
(1) A mine with less than 20 miners. MSHA traditionally regards mines
  with less than 20 miners as ``small'' mines, and those with 20 or more
  miners as ``large'' mines based on differences in operation. However,
  in examining the impact of the proposed regulations on the mining
  community, MSHA, consistent with the Small Business Administration
  definition for small mines, which refers to employers with 500
  employees or less, has analyzed impact for this size. This is
  discussed in the Agency's preliminary regulatory economic analysis for
  this proposed rule.
(2) Preliminary 1996 MSHA data.
(3) Data from MSHA approval and certification center, Oct. 95.
(4) Actual inventory, rounded to nearest 50.
(5) Estimates are based on a January 1998 count, by MSHA inspectors, of
  underground mines that use diesel powered equipment.
(6) The estimates are based on a January 1998 count, by MSHA inspectors,
  of diesel powered equipment normally in use.
(7) Based on assumption that all surface coal mines had some diesel
  powered equipment.
(8) Based on MSHA inventory of 25% of surface coal mines.
(9) MSHA assumes all surface M/NM mines use some diesel engines.
(10) Derived by applying ratios (engines per mine) from MSHA inventory
  of surface coal mines to M/NM mines.

    As noted in Table II-1, a majority of underground metal and 
nonmetal mines, and all surface mines, use diesel-powered equipment. 
This is not true in underground coal mines--in no small measure 
because, as discussed later in this part, several key underground coal 
states have for many years banned the use of diesel-powered equipment 
in such mines.
    Neither the diesel engines nor the diesel-powered equipment are 
identical from sector to sector. This relates to the equipment needs in 
each sector. This is important information because the type of engine, 
and the type of equipment in which it is installed, can have important 
consequences for particulate production and control.
    As the horsepower size of the engine increases, the mass of dpm 
emissions produced per hour increases. (A smaller engine may produce 
the same or higher levels of particulate emissions per volume of 
exhaust as a large engine, due to the airflow, but the mass of 
particulate matter increases with the engine size). Accordingly, as 
engine size increases, control of emissions may require additional 
efforts.
    Diesel engines in metal and nonmetal underground mines, and in 
surface coal mines, range up to 750 HP or greater; by contrast, in 
underground coal mines, the average engine size is less than 150 HP. 
The reason for this disparity is the nature of the equipment powered by 
diesel engines. In underground metal and nonmetal mines, and surface 
mines,

[[Page 58125]]

diesel engines are widely used in all types of equipment -- both the 
equipment used under the heavy stresses of production and the equipment 
used for support. By contrast, the great majority of the diesel usage 
in underground coal mines is in support equipment. For example, in 
underground metal and nonmetal mines, of the approximate 4,100 pieces 
of diesel equipment normally in use, about 1,800 units are for loading 
and hauling. By contrast, of the approximate 3,000 pieces of diesel 
equipment in underground coal, MSHA estimates that less than 50 pieces 
are for coal haulage. The largest diesel engines are used in surface 
operations; in underground metal and nonmetal mines, the size of the 
engine can be limited by the size of the shaft opening.
    The type of equipment in the sectors also varies in another way 
that can affect particulate control directly, as well as constrain 
engine size. In underground coal, equipment that is used in face 
(production) areas of the coal mine must be MSHA-approved Part 36 
permissible equipment. These locations are the areas where methane gas 
is likely to accumulate in higher concentrations. This includes the in-
by section starting at the tailpiece (coal dump point) and all returns. 
Part 36 permissible equipment for coal requires the use of flame 
arresters on the intake and exhaust systems and surface temperature 
control to below 302 deg.F. As discussed in more detail elsewhere in 
this notice, the cooler exhaust from these permissible pieces of 
equipment permits the direct installation of particulate filtration 
devices such as paper type filters that cannot be used directly on 
engines with hot exhaust. In addition, the permissibility requirements 
have had the effect of limiting engine size. This is because prior to 
MSHA's issuance of a diesel equipment rule in 1996, surface temperature 
control was done by water jacketing. This limited the horsepower range 
of the permissible engines because manufacturers have not expended 
resources to develop systems that could meet the 302 deg.F surface 
temperature limitation using a water jacketed turbocharger.
    In the future, larger engines may be used on permissible equipment, 
because the new diesel rule allows the use of new technologies in lieu 
of water jacketing. This new technology, plus the introduction of air-
charged aftercoolers on diesel engines, may lead to the application of 
larger size diesel engines for underground coal production units. 
Moreover, if manufacturers choose to develop this type of technology 
for underground coal production units, the number of diesel production 
machines may increase.
    There are also a few underground metal and nonmetal mines that are 
gassy, and these require the use of Part 36 permissible equipment. 
Permissible equipment in metal and nonmetal mines must be able to 
control surface temperatures to 400 deg.F. MSHA estimates that there 
are currently less than 15 metal and nonmetal mines classified as gassy 
and which, therefore, must use Part 36 permissible equipment if diesels 
are utilized in areas where permissible equipment is required. These 
gassy metal and nonmetal mines have been using the same permissible 
engines and power packages as those approved for underground coal 
mines. (MSHA has not certified a diesel engine exclusively for a Part 
36 permissible machine for the metal and nonmetal sector since 1985 and 
has certified only one permissible power package; however, that engine 
model has been retired and is no longer available as a new purchase to 
the industry). As a result, these mines are in a similar situation as 
underground coal mines: engine size (and thus dpm production of each 
engine) is more limited, and the exhaust is cool enough to add the 
paper type of filtration device directly to the equipment.
    In nongassy underground metal and nonmetal mines, and in all 
surface mines, mine operators can use conventional construction 
equipment in their production sections without the need for 
modifications to the machines. Two examples are haulage vehicles and 
dump trucks. Some construction vehicles may be redesigned and 
articulated for sharper turns in underground mines; however, the 
engines are still the industrial type construction engines. As a 
result, these mines can and do use engines with larger horsepower. At 
the same time, since the exhaust is not cooled, paper-type filters 
cannot be added directly to this equipment without first adding a water 
scrubber, heat exchanger or other cooling device. The same is true for 
the equipment used in outby areas of coal mines, where the methane 
levels do not require the use of permissible equipment.
    Future Demand and Emissions. MSHA expects there will be more 
diesel-powered equipment added to the Nation's mines. While other types 
of power sources for mining equipment are available, many in the mining 
industry believe that diesel power provides both safety and economic 
advantages over alternative power sources available today. Not many 
studies have been done recently on these contentions, and the studies 
which have been reviewed by MSHA do not clearly support this 
hypothesis; but as long as this view remains prevalent, continued 
growth is likely.
    There are additional factors that could increase growth. As noted 
above, permissible equipment can now be designed in such a way to 
permit the use of larger engines, and in turn more use of diesel-
powered production equipment in underground coal and other gassy mines. 
Moreover, state laws banning the use of diesel engines in the 
underground coal sector are under attack. As noted in section 8 of this 
part, until recently, three major underground coal states, 
Pennsylvania, West Virginia, and Ohio, have prohibited the use of 
diesel engines in underground coal mines. In late 1996, Pennsylvania 
passed legislation (PA Senate Bill No. 1643) permitting such use under 
conditions defined in the statute. West Virginia passed legislation 
lifting its ban as of May, 1997 (WV House Bill 2890), subject to 
regulations to be developed by a joint labor-industry commission. This 
makes the need to address safety and health concerns about the use of 
such engines very pressing.
    In the long term, the mining industry's diesel fleet will become 
cleaner, even if the size of the fleet expands. This is because the old 
engines will eventually be replaced by new engines that will emit fewer 
particulates than they do at present. As discussed in Section 4 of this 
part, EPA regulations limiting the emissions of particulates and 
various gasses from new diesel engines are already being implemented 
for some of the smaller engines used in mining. Under a defined 
schedule, these new standards will soon apply to other new engines, 
including the larger engines used in mining. Moreover, over time, the 
emission standards which new engines will have to pass will become more 
and more stringent. Under international accords, imported engines are 
also likely to be cleaner: European countries have already established 
more stringent emission requirements (Needham, 1993; Sauerteig, 1995).
    Based on the feasibility using the estimator, new engine 
technology, catalytic converters, and current ventilation should reduce 
dp levels down below the 400TCum3. However, to 
reduce to the 160TCum3 level, dp filters or cabs 
will still be needed on a certain number of equipment, based on mining 
conditions and diesel usage. The particulate index values listed for 
the MSHA approved engines provides information on the dp emissions and 
also can be used to help determine how low engine technology alone can 
lower

[[Page 58126]]

dp exposures. When filters are used, the cleaner engines allow the 
filters to last longer between change out or cleaning. The newer 
technology engines, especially the electronic models, also add the 
benefit of diagnostic control. The engines computer can inform the 
mechanic on the condition of the engine and warn the mechanic when an 
engine is in need of maintenance.
    But MSHA believes that turnover of the mining fleet to these new, 
cleaner engines will take a very long time because the mining industry 
tends to purchase for mining use older equipment that is being 
discarded by other industries. In the meantime, the particulate burden 
on miners as a group is expected to remain at current levels or even 
grow.
    (2) Diesel Exhaust and Diesel Particulate. The emissions from 
diesel engines are actually a complex mixture of compounds, containing 
gaseous and particulate fractions. The specific composition of the 
diesel exhaust in a mine will vary with the type of engines being used 
and how they are used. Factors such as type of fuel, load cycle, engine 
maintenance, tuning, and exhaust treatment will affect the composition 
of both the gaseous and particulate fractions of the exhaust. This 
complexity is compounded by the multitude of environmental settings in 
which diesel-powered equipment is operated. Elevation, for example, is 
a factor. Nevertheless, there are a few basic facts about diesel 
emissions that are of general applicability.
    The gaseous constituents of diesel exhaust include oxides of 
carbon, nitrogen and sulfur, alkanes and alkenes (e.g., butadiene), 
aldehydes (e.g., formaldehyde), monocyclic aromatics (e.g., benzene, 
toluene), and polycyclic aromatic hydrocarbons (e.g., phenanthrene, 
fluoranthene). The oxides of nitrogen (NOx) are worth 
particular mention because in the atmosphere they can precipitate into 
particulate matter. Thus, controlling the emissions of NOx 
is one way that engine manufacturers can control particulate production 
indirectly. (See Section 4 of this part.)
    The particulate fraction of diesel exhaust--what is known as soot--
is made up of very small individual particles. Each particle consists 
of an insoluble, elemental carbon core and an adsorbed, surface coating 
of relatively soluble organic carbon (hydrocarbon) compounds. There can 
be up to 1,800 different organic compounds adsorbed onto the elemental 
carbon core. A portion of this hydrocarbon material is the result of 
incomplete combustion of fuel; however, the majority is derived from 
the engine lube oil. In addition, the diesel particles contain a 
fraction of non-organic adsorbed materials.
    Diesel particles released to the atmosphere can be in the form of 
individual particles or chain aggregates (Vuk, Jones, and Johnson, 
1976). In underground coal mines, more than 90% of these particles and 
chain aggregates are submicrometer in size--i.e., less than 1 
micrometer (1 micron) in diameter. In underground metal and nonmetal 
mines, a greater portion of the aggregates may be larger than 1 micron 
in size because of the equipment used. Dust generated by mining and 
crushing of material--e.g., silica dust, coal dust, rock dust--is 
generally not submicrometer in size.
    Figure II-1 shows a typical size distribution of the particles 
found in the environment of a mine that uses equipment powered by 
diesel engines (Cantrell and Rubow, 1992). The vertical axis represents 
relative concentration, and the horizontal axis the particle diameter. 
As can be seen, the distribution is bimodal, with dpm generally being 
well less than 1 m in size and dust generated by the mining 
process being well greater than 1 m. Because of their small 
size, even when diesel particles are present in large quantities, the 
environment might not be perceived as ``dusty''. Rather, the perception 
might be primarily of a vaporous, dirty and smelly ``soot'' or 
``smoke''.
[GRAPHIC] [TIFF OMITTED] TP29OC98.020



[[Page 58127]]


    The particulate nature of diesel soot has special significance for 
the mining community, which has a history of significant health and 
safety problems associated with dusts in the mining atmosphere. As a 
result of this long experience, the mining community is familiar with 
the standard techniques to control particulate concentrations. It knows 
how to use ventilation systems, for example, to reduce dust levels in 
underground mines. It knows how to water down particulates capable of 
being impacted by that approach, and to divert particulates away from 
where miners are actively working. Moreover, the mining community has 
long experience in the sampling and measurement of particulates--and in 
all the problems associated therewith. Miners and mine operators are 
very familiar with sampling devices that are worn by miners during 
normal work activities or placed in specific locations to collect dust. 
They understand the significance of sample integrity, the validity of 
laboratory analysis, and the concept of statistical error in individual 
samples. They know that weather and mine conditions can affect 
particulate production, as can changes in mine operations in an area of 
the mine. MSHA and the former Bureau of Mines have conducted 
considerable research into these topics. While the mining community has 
often argued over these points, and continues to do so, the 
sophistication of the arguments reflects the thorough familiarity of 
the mining community with particulate sampling and analysis techniques.
    (3) Methods Available to Measure DPM. There are a number of methods 
which can measure dpm concentrations with reasonable accuracy when it 
is at high concentrations and when the purpose is exposure assessment. 
Measurements for the purpose of compliance determinations must be more 
accurate, especially if they are to measure compliance with a dpm 
concentration as low as 200 g/m3 or lower. It is 
with these considerations in mind that MSHA has carefully analyzed the 
available methods for measuring dpm.
    Comments. In its advanced notice of proposed rulemaking (ANPRM) in 
1992, MSHA sought information on whether there are methodologies 
available for assessing occupational exposures to diesel particulate.
    Some commenters argued that at that time there was no validated 
sampling method for diesel exhaust and there had been no valid 
analytical method developed to determine the concentration of diesel 
exhaust. According to the American Mining Congress, (AMC 1992), 
sampling methods commonly in use were prototypic in nature, were 
primarily being utilized by government agencies and were subject to 
interference. Commenters also stated that sampling instrumentation was 
not commercially available and that the analytical procedures could 
only be conducted in a limited number of laboratories. Several industry 
commenters submitted results of studies to support their position on 
problems with measuring diesel particulate in underground mines. A 
problem with sampler performance was noted in a study using prototype 
dichotomous sampling devices. Another commenter indicated that the 
prototype sampler developed by the former Bureau of Mines (discussed 
later in this section) for collecting the submicrometer respirable dust 
was difficult to assemble but easy to use, and that no problems were 
encountered. Problems associated with gravimetric analysis were also 
noted in assessing a short term exposure limit (STEL). Another 
commenter (Morton, 1992) indicated the cost of the sampling was 
prohibitive.
    Another issue addressed by commenters to the 1992 ANPRM was ``Are 
existing sampling and exposure monitoring methods sufficiently 
sensitive, accurate and reliable?'' If not, what methods would be more 
suitable? Some commenters indicated their views that sampling methods 
had not been validated at that time for compliance sampling. They 
asserted that, depending on the level of measurement, both the size 
selective and elemental carbon techniques have some utility. The 
measurement devices give a precise measurement; however, because of 
interferants, corrections may need to be made to obtain an accurate 
measurement. Commenters also expressed the view that all of the 
sampling devices are sophisticated and require some expertise to 
assemble and analyze the results, and that MSHA should rely on outside 
agencies to evaluate and validate the sampling methods. An on-board 
sampler being developed by Michigan Technological University was the 
only other emission measurement technology discussed in the comments. 
However, this device is still in the development stage. Another 
commenter indicated that the standard should be based on the hazard and 
that the standard would force the development of measurement 
technology.
    Submicrometer Sampling. The former Bureau of Mines (BOM) submitted 
information on the development of a prototype dichotomous impactor 
sampling device that separates and collects the submicrometer 
respirable particulate from the respirable dust sampled (See Figure II-
2).

[[Page 58128]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.021



    The sampling device was designed to help measure dpm in coal mine 
environments, where, as noted in the last section of this part, nearly 
all the dpm is submicrometer (less than 1 micron) in size. In its 
submission to MSHA, the former BOM noted it had redesigned a prototype 
and had verified the sampler's performance through laboratory and field 
tests.
    As used by the former BOM in its research, the submicrometer 
respirable particulate was collected on a pre-weighed filter. Post-
weighing of the filter provides a measure of the submicrometer 
respirable particulate. The relative insensitivity of the gravimetric 
method only allows for a lower limit of detection of approximately 200 
g/m\3\.
    Because submicrometer respirable particulate can contain 
particulate material other than diesel particulate, measurements can be 
subject to interference from other submicrometer particulate material.
    NIOSH Method 5040. In response to the ANPRM, NIOSH submitted 
information relative to the development of a sampling and analytical 
method to assess the diesel particulate concentration in an environment 
by measuring the amount of total carbon.
    As discussed earlier in this part, diesel particulate consists of a 
core of elemental carbon (EC), adsorbed organic carbon (OC) compounds, 
sulfates, vapor phase hydrocarbons and traces of other compounds. The 
method developed by NIOSH provides for the collection of a sample on a 
quartz fiber filter. The filter is mounted in an open face filter 
holder that allows for the sample to be uniformly deposited on the 
filter surface. After sampling, a section of the filter is analyzed 
using a thermal-optical technique (Birch and Cary, 1996). This 
technique allows the EC and OC species to be separately identified and 
quantified. Adding the EC and OC species together provides a measure of 
the total carbon concentration in the environment. This is indicated 
diagrammatically in Figure II-3.
    Studies have shown that the sum of the carbon (C) components 
(EC+OC) associated with dpm accounts for 80-85% of the total dpm 
concentration when low sulfur fuel is used (Birch and Cary, 1996). 
Since the TC:DPM relationship is consistent, it provides a method for 
determining the amount of dpm.
    The method can detect as little as 1  g/m3 of TC. 
Moreover, NIOSH has investigated the method and found it to meet 
NIOSH's accuracy criterion (NIOSH, 1995); i.e., that measurements come 
within 25 percent of the true TC concentration at least 95 percent of 
the time.

[[Page 58129]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.022



    NIOSH Method 5040 is directly applicable for the determination of 
diesel particulate levels in underground metal and nonmetal mines. The 
only potential sources of carbon in such mines would be organic carbon 
from oil mist and cigarette smoke. Oil mist may occur when diesel 
equipment malfunctions or is in need of maintenance.
    MSHA, currently, has no data as to the frequency of occurrence or 
the magnitude of the potential interference from oil mist. However, 
during studies conducted by MSHA to evaluate different methods used to 
measure diesel particulate concentrations in underground mines, MSHA 
has not encountered situations where oil mist was found to be an 
interferant. Moreover, the Agency assumes that full operator 
implementation of maintenance standards to minimize dpm emissions 
(which are part of MSHA's proposed rule) will minimize any remaining 
potential for such interference. MSHA welcomes comments or data 
relative to oil mist interference. Cigarette smoke is under the control 
of operators, during sampling times in particular, and hence should not 
be a consideration.
    While samples in underground metal and nonmetal mines could be 
taken with a submicrometer impactor, this could lead to underestimating 
the total amount of dpm present. This is because the fraction of dpm 
particles greater than 1 micron in size in the environment of noncoal 
mines can be as great as 20% (Vuk, Jones, and Johnson, 1976).
    When sampling diesel particulate in coal mines, the NIOSH method 
recommends that a specialized impactor with a submicrometer cut point, 
such as the one developed by the former BOM, be used. Use of the 
submicron impactor minimizes the collection of coal particles, which 
have an organic carbon content. However, if 10% of coal particles are 
submicron, this means that up to 200 micrograms of submicrometer coal 
dust could be collected in face areas under current coal dust 
standards. Accordingly, for samples collected in underground coal 
mines, an adjustment may have to be made for interference from 
submicrometer coal dust; however, outby areas where little coal mine 
dust is present may not need such an adjustment.
    NIOSH further recommends that in using its method in coal mines, 
the sample only be analyzed for the EC component. Measuring only the EC 
component ensures that only diesel particulate material is being 
measured in such cases. However, there are no established relationships 
between the concentration of EC and total dpm under various operating 
conditions. (The organic carbon component of dpm can vary with engine 
type and duty cycle; hence, the amount of whole dpm present for a 
measured amount of EC may vary). The Agency welcomes data and 
suggestions that would help it ascertain if and how measurements of 
submicrometer elemental carbon could realistically be used to measure 
dpm concentrations in underground coal mines.
    Although NIOSH Method 5040 requires no specialized equipment for 
collecting a dpm sample, the sample would most probably require 
analysis by a commercial laboratory. MSHA recognizes that the number of 
laboratories currently capable of analyzing samples using the thermal-
optical method is limited. However, there are numerous laboratories 
available that have the ability to perform a TC analysis without 
identifying the different species of carbon in the sample. Total carbon 
determinations using these laboratories would provide the mine with 
good information relative to the levels of dpm to which miners are 
potentially exposed. MSHA believes that once there is a need (e.g., as 
a result of the requirements of the proposed rule), more commercial 
laboratories will develop the capability to analyze dpm samples using 
the thermo-optical analytical method. Currently, the cost to analyze a 
submicrometer particulate sample for its TC content ranges from $30 to 
$50. This cost is consistent with costs associated with similar 
analysis of minerals such as quartz.
    RCD Method. Another method, referred to as the Respirable 
Combustible Dust Method (RCD), has been developed in Canada for 
measuring dpm concentrations in noncoal mines. Respirable dust is 
collected with a respirable dust sampler consisting of a 10 millimeter 
nylon cyclone and a filter capsule containing a preweighed, 
preconditioned silver membrane filter. Samples are collected at a flow 
rate of 1.7 liters per minute. The respirable sample collected includes 
both combustible and noncombustible particulate matter.

[[Page 58130]]

    Samples collected in accordance with the RCD method require 
analysis by a commercial laboratory. Total respirable dust is 
determined gravimetrically by weighing the filter after the sample is 
collected. After the sample has been subjected to a controlled 
combustion process at 400  deg.C for two hours, the remainder of the 
sample is weighed, and the amount of the particulate burned off 
determined by subtraction. This is the RCD. The combustible particulate 
matter consists of the soluble organic fraction, the EC core of the 
dpm, and any other combustible material collected. Thus, only a portion 
of the RCD is attributable to dpm. Oil mist and other combustible 
matter collected on the filter are interferants that can affect the 
accuracy of dpm concentration determination using this method. Because 
the mass of RCD is determined by weighing, the relative insensitivity 
of this method is similar to that obtained with the size selective 
gravimetric method (approximately 200 g/m\3\).
    One commenter (Inco Limited) indicated experience with this method 
for identifying diesel particulate in their mining operations and 
suggested that this technique may be appropriate for determining eight 
hour exposures. Although this method was commonly used by the commenter 
for assessing dpm levels, concerns for the efficiency of the cyclones 
used to sample the respirable fraction of the particulate along with 
interference from oil mist were expressed.
    Canada is now experimenting with the use of a submicron impactor 
with the RCD method.
    Sampler Availability. The components for conducting sampling 
according to the submicrometer and the RCD methods are commercially 
available, as are those for NIOSH Method 5040, without a submicrometer 
particulate separator (impactor).
    A reusable impactor can be manufactured by machine shops following 
the design specifications developed by the former U.S. Bureau of Mines 
(BOM IC 9324, 1992). The use of the size-selective samplers requires 
some training and laboratory time to prepare the impaction plate and 
assemble the unit. The cost to manufacture the size-selective units is 
approximately $35.
    In addition, MSHA has requested NIOSH to develop and provide a 
commercially available disposable submicrometer particulate separator 
that would be used with existing personal respirable dust sampling 
equipment. The commercially available separator will be manufactured 
according to design criteria specified by NIOSH. It is anticipated that 
other sampling instrument manufacturers will develop commercial units 
once there is an established need for such a sampling device.
    Use of Alternative Surrogates to Assess DPM Concentrations. A 
number of commenters on the ANPRM indicated that a number of surrogates 
were available to monitor diesel particulate. Of the surrogates 
suggested, the most desirable to use would be carbon dioxide because of 
its ease of measurement. In 1992 the former Bureau of Mines (BOM IC 
9324, 1992) reported on research being conducted to investigate the use 
of CO2 as a surrogate to assess mine air quality where 
diesel equipment is utilized. However, because the relationship between 
CO2 and other exhaust components depends on the number, type 
and duty cycle of the engines in operation, no acceptable measurement 
method based on the use of CO2 has been developed.
    (4) Reducing Soot at the Source--Engine Standards. One way to limit 
diesel particulate emissions is to redesign diesel engines so they 
produce fewer pollutants. Engine manufacturers around the world are 
being pressed to do this pursuant to environmental regulations. These 
cleaner engine requirements are sometimes referred to as tailpipe 
standards because compliance is measured by checking for pollutants as 
the exhaust emerges from the engine's tailpipe--before any 
aftertreatment devices. This section reviews developments in this area, 
and explains the relationship between the environmental standards on 
new engines and MSHA engine ``approval'' requirements.
    The Clean Air Act and Mobile Sources. The Clean Air Act authorized 
the Federal Environmental Protection Agency (EPA) to establish 
nationwide standards for new mobile vehicles, including those powered 
by diesel engines. These standards are designed, over time, to reduce 
the volume of certain harmful atmospheric pollutants emanating from 
mobile sources: particulate matter, nitrogen oxides (which as 
previously noted, can result in the generation of particulates in the 
atmosphere), hydrocarbons and carbon monoxide.
    California has its own standards. New engines destined for use in 
California must meet standards under the law of that State. The 
standards are issued and administered by the California Air Resources 
Board (CARB). In recent years, EPA and CARB have worked together with 
industry in establishing their respective standards, so most of them 
are identical.
    Regulatory responsibility for implementation of the Clean Air Act 
is vested in the Office of Mobile Sources (OMS), part of the Office of 
Air and Radiation of the EPA. Some of the discussion which follows was 
derived from materials which can be accessed from the OMS home page on 
the World Wide Web at (http://www.epa.gov/docs/omswww/omshome.htm). 
Information about the CARB standards may be found at the home page of 
that agency at (http://www.arbis.arb.ca.gov/homepage.htm).
    Engines are generally divided into three broad categories for 
purposes of environmental emissions standards, in accordance with the 
primary use for which the type of engine is designed: (1) cars and 
light duty trucks (i.e., to power passenger transport); (2) heavy duty 
trucks (i.e., to power over-the-road hauling); and (3) nonroad vehicles 
(i.e., to power small equipment, construction equipment, locomotives 
and other non-highway uses). Engines used in mining equipment are not 
regulated as a separate category in this regard, but engines in all 
three categories are engaged in mining work, from generator sets to 
pickup trucks to huge earth movers and haulers.
    New vs. Used. The environmental tailpipe requirements are 
applicable only to new engines. In the mining industry, used engines 
are often purchased; and, of course, the existing fleet consists of 
engines that are not new. Thus, although these tailpipe requirements 
will bring about gradual reduction in the overall contribution of 
diesel pollution to the atmosphere, the beneficial effects on mining 
atmospheres may require a longer timeframe, absent actions to 
accelerate the turnover of mining fleets to the cleaner engines.
    In underground coal mining, MSHA has already taken actions which 
will have such an effect on the fleet. The diesel equipment rule issued 
in late 1996 requires that by November 25, 1999, all diesel equipment 
used in underground coal mines use an approved engine and maintain that 
engine in approved condition (30 CFR 75.1907). MSHA expects this will 
result in the replacement of about 47 percent of the diesel engines now 
in the underground coal mine inventory with engines that emit fewer 
pollutants. The timeframe permitted for the turnover was based upon 
MSHA's estimates of the useful life in an underground mining 
environment of the ``outby'' equipment involved.
    Technology-Forcing Schedule. As noted above, the exact 
environmental tailpipe requirements which a new

[[Page 58131]]

diesel engine must meet varies with the date of manufacture. The Clean 
Air Act, which was most recently amended in 1990, establishes a 
schedule for the reduction of particular pollutants from mobile 
sources. EPA and CARB, working closely with the diesel engine industry, 
have endeavored to turn this into a regulatory schedule that forces 
technology while taking into account certain technological realities 
(e.g., actions taken to reduce particulate emissions may increase 
NOX emissions, and vice versa). Existing EPA regulations for 
on-highway engines (both for light duty vehicles and heavy duty trucks) 
and non-road engines schedule the tailpipe standards that must be met 
for the rest of this century. Agreements between EPA, CARB and the 
engine industry are now leading to proposed rules for engine standards 
to be met during the early part of the next century. These standards 
will be stricter and will lower the levels of diesel emissions.
    Light-Duty Engines. The current regulations on light duty vehicle 
engines (cars and passenger trucks) were set in 1991 (56 FR 25724). EPA 
is currently considering proposing new standards for this category. 
Pursuant to a specific requirement in the Clean Air Act Amendments of 
1990, EPA is to study and report to Congress on whether further 
reductions in this category should be pursued. A public workshop was 
held in the Spring of 1997. EPA plans provide for a draft report to be 
available for public comment by Spring of 1998, and a final report 
completed by July 1998, although a notice of citizen suit has been 
filed to speed the process. Up-to-date information about the progress 
of this initiative can be found at the home page for the study (http://
www.epa.gov/omswww/tr2home.htm).
    On-highway Heavy Duty Truck Engines. The first phase of the on-
highway standards for heavy duty diesel engines was applicable to 
engines manufactured in 1985 (40 CFR 86.085-11). For the first time, 
separate standards for nitrogen oxide (NOX) and hydrocarbons 
(HC) were established. The nitrogen oxides and hydrocarbons are 
precursors of ground level ozone, a major component of smog. A number 
of hydrocarbons are also toxic, while nitrogen oxides contribute to the 
formation of acid rain and can, as previously noted, precipitate into 
particulate matter. In 1988, a specific standard limiting particulate 
matter emitted from the heavy duty on-highway diesel engines went into 
effect (40 CFR 86.088-11). The Clean Air Act Amendments and the 
regulations provided for phasing in even tighter controls on 
NOX and particulate matter through 1998. Reductions in 
NOX took place in 1990 and 1991 and are to occur again in 
1998, and reductions in PM took place in 1991 and 1994. Certain types 
of trucks in particularly polluted urban areas must reach even tighter 
requirements.
    On October 21, 1997, EPA issued a new rule for on-highway engines 
that will take effect for engine model years starting in 2004 (62 FR 
54693). The rule establishes a combined requirement for NOX 
and HC. The combined standard is set at 2.5gm/bhp-hr, which includes a 
cap of 0.5gm/bhp-hr for HC. Prior to the rule, the EPA, CARB, and the 
engine manufacturers signed a Statement of Principles (SOP) that agreed 
on harmonization of the emission standards and the feasible levels that 
could be achieved. The rule allows manufacturers a choice of two 
combinations of NOX and HC, with a net expected reduction in 
NOX emissions of 50%. The rule does not require further 
reductions in tailpipe emissions of PM.
    Non-road Engines. Of particular interest to the mining community is 
the EPA's regulatory work on the standards that will be applicable to 
non-road engines, for these include the engines used in the heaviest 
mining equipment.
    The 1990 Clean Air Act Amendments specifically directed EPA to 
study the contribution of nonroad engines to air pollution, and 
regulate them if warranted. In 1991, EPA released a study that 
documented higher than expected emission levels across a broad spectrum 
of nonroad engines and equipment (EPA Fact Sheet, EPA420-F-96-009, 
1996). In response, EPA initiated several regulatory programs. One of 
these set emission standards for land-based nonroad engines greater 
than 50 horsepower (other than for rail use). Limits are established 
for tailpipe emissions of hydrocarbons, carbon monoxide, 
NOX, and dpm. The limits are phased in from 1996 to 2000: 
starting in 1996 with nonroad engines from 175 to 750 hp, then smaller 
engines, and by 2000 the larger nonroad engines. Moreover, in February 
1997, restrictions on nonroad engines for locomotives were proposed (62 
FR 6366).
    In September 1996, EPA announced another Statement of Principles 
(SOP) with the engine industry and CARB on new rounds of restrictions 
for non-road engines to begin to take place in this century. This led 
in September 1997 to a proposed rule setting standards for almost all 
types of engines in this category manufactured after 1999-2006 (the 
actual year depends on the category) (62 FR 50151). The applicable 
standards for an engine category would be gradually tightened through 
three tiers. They would set a cap on the combined NOX and HC 
(similar to the on-highway), set CO standards, and lower standards on 
PM. The implementation of the final tier of the proposed reductions is 
subject to a technology review in 2001 to ensure that the 
appropriateness of the levels to be set is feasible.
    Will the Diesel Engine Industry Meet Mining Industry Requirements? 
Concern has been expressed from time to time that the diesel industry 
might not be able to meet the ever tightening standards on tailpipe 
emissions, and might, therefore, stop producing certain engines needed 
by the mining community or other industries (Gushee, 1995). To date, 
however, such concerns have not been realized. The fact that the most 
recent regulations have been developed through a consensus process with 
the engine industry, and that the non-road plan includes a scheduled 
technology review to ensure the proposed emission standards can really 
be achieved, suggests that although the EPA standards are technology 
forcing, diesel engines will continue to be available to meet the needs 
of the mining community for the foreseeable future. In addition, the 
nonroad engine agreement with the industry calls for development of a 
separate research agreement involving stakeholders in the exploration 
of technologies that can achieve very low emission levels of 
NOX and PM ``while preserving performance, reliability, 
durability, safety, efficiency, and compatibility with nonroad 
equipment'' (EPA420-F-96-015, September 1996). Also, Vice President 
Gore has recently noted that the Administration is committed to 
emissions research that would clean up both the diesels currently on 
the road, as well as enabling these engines an opportunity to compete 
as a new generation of vehicles is developed that are far more 
efficient than today's vehicles (White House Press Release, July 23, 
1997). It is always possible, of course, that some new technological 
problems could emerge that could impact diesel engine availability--
e.g., confirmation that some of the newer engines produce high levels 
of ``nanoparticles'' particulates and that such emissions pose some 
sort of a health problem. Research of nanoparticles and their health 
effects is currently a topic of investigation (Bagley et al., 1996).
    A related question has been whether the costs of the ``high-tech'' 
diesel engines will make them unaffordable in practice to the mining 
community.

[[Page 58132]]

MSHA believes the new engines will be affordable. The fact that the 
engine industry has agreed to the new standards, and has some assurance 
of what the applicable standards will be for the foreseeable future, 
should help keep costs in check.
    In theory, underground mines can control costs by purchasing 
certain types of new engines that do not have to meet the new EPA 
standards. The rules on heavy duty on-highway truck engines were not 
applied to engines intended to be used in underground coal mines (59 FR 
31336), and the new proposed rules on nonroad vehicles would likewise 
not be mandatory for engines intended for any underground mining use. 
In practice, however, it is not likely that engine manufacturers will 
produce special engines once they switch over their production lines to 
meet the new EPA standards, because there are few types and sizes of 
engines in production for which the mining community is the major 
market. Moreover, the larger engines (above 750 hp) are specifically 
covered by the EPA nonroad rules (Engine Manufacturers Assn. v. EPA, 88 
F.3d 1075, 319 U.S. App.D.C. 12 (1996).
    MSHA Approved Engines. Acting under its own authority to protect 
miner safety and health, MSHA requires that diesel engines used in 
certain types of mining operations be ``approved'' as meeting certain 
tailpipe standards.
    In some ways, the standards are akin to those of EPA and CARB. For 
example, MSHA, CARB and EPA generally use the same tests to check 
emissions. MSHA uses a steady state, 8-mode test cycle, the same as EPA 
and CARB use to test engines designed for use in off-road equipment; 
however, EPA uses a different, transient test for on-highway engines.
    But to be approved by MSHA, an engine does not have to be as clean 
as the newer diesel engines, every generation of which must meet ever 
tighter EPA and CARB tailpipe standards. Approval of an engine by MSHA 
merely ensures that the tailpipe emissions from that engine meet 
certain basic standards of cleanliness--cleaner than the engines which 
many mines continue to use.
    The MSHA approval rules were revised in 1996 (as part of the 1996 
rule on the use of diesel equipment in underground coal mines) to 
provide the mining community with additional information about the 
cleanliness of the emissions emerging from the tailpipe of various 
engines. Specifically, the agency now requires that a particulate index 
(PI) be reported as part of MSHA's engine approval. This index permits 
operators to evaluate the contribution of a proposed new addition to 
the fleet to the mine's particulate concentrations.
    There is no requirement that approved engines meet a particular PI; 
rather, the requirement is for information purposes only. In its 1996 
rulemaking addressing diesel equipment in underground coal mines, MSHA 
explicitly deferred until this rulemaking the question of whether to 
require engines used in mining environments to meet a particular PI (61 
FR 55420-21, 55437). The Agency has decided not to take that approach, 
for the reasons discussed in Part V of this preamble.
    (5) Limiting the Public's Exposure to Soot--Ambient Air Quality 
Standards. Pursuant to the Clean Air Act, EPA is responsible for 
setting air pollution standards to protect the public from toxic air 
contaminants. These include standards to limit exposure to particulate 
matter. The pressures to comply with these limits have an impact upon 
the mining industry, which contributes various types of particulate 
matter into the environment during mining operations, and a special 
impact on the coal mining industry whose product is used extensively in 
emission-generating power facilities. But those standards hold interest 
for the mining community in other ways as well, for underlying some of 
them is a large body of evidence on the harmful effects of airborne 
particulate matter on human health. Increasingly, that evidence has 
pointed toward the risks of the smallest particulates--including the 
particles generated by diesel engines.
    This section provides an overview of EPA rulemaking on particulate 
matter. For more detailed information, commenters are referred to ``The 
Plain English Guide to the Clean Air Act,'' EPA 400-K-93-001, 1993, to 
the ``Review of the National Ambient Air Quality Standards for 
Particulate Matter: Policy Assessment of Scientific and Technical 
Information'', EPA-452/R-96-013, 1996; and, on the latest rule, to EPA 
Fact Sheets, July 17, 1997. These and other documents are available 
from EPA's Web site.
    Background. Air quality standards involve a two-step process: 
standard setting by EPA, and implementation by each State.
    Under the law, EPA is specifically responsible for reviewing the 
scientific literature concerning air pollutants, and establishing and 
revising National Ambient Air Quality Standards (NAAQS) to minimize the 
risks to health and the environment associated with such pollutants. It 
is supposed to do a review every five years. Feasibility of compliance 
by pollution sources is not supposed to be a factor in establishing 
NAAQS. Rather, EPA is required to set the level that provides ``an 
adequate margin of safety'' in protecting the health of the public.
    Implementation of each national standard is the responsibility of 
the states. Each must develop a state implementation plan that ensures 
air quality in the state consistent with the ambient air quality 
standard. Thus, each state has a great deal of flexibility in targeting 
particular modes of emission (e.g., mobile or stationary, specific 
industry or all, public sources of emissions vs. private-sector 
sources), and in what requirements to impose on polluters. However, EPA 
must approve the state plans pursuant to criteria it establishes, and 
then take pollution measurements to determine whether all counties 
within the state are meeting each ambient air quality standard. An area 
not meeting an NAAQS is known as a ``nonattainment area''.
    TSP. Particulate matter originates from all types of stationary, 
mobile and natural sources, and can also be created from the 
transformation of a variety of gaseous emissions from such sources. In 
the context of a global atmosphere, all these particles are mixed 
together, and both people and the environment are exposed to a 
``particulate soup'' the chemical and physical properties of which vary 
greatly with time, region, meteorology, and source category. The first 
ambient air quality standards dealing with particulate matter did not 
distinguish among these particles. Rather, the EPA established a single 
NAAQS for ``total suspended particulates'', known as ``TSP.'' Under 
this approach, the states could come into compliance with the ambient 
air requirement by controlling any type or size of TSP. As long as the 
total TSP was under the NAAQS--which was established based on the 
science available in the 1970s--the state met the requirement.
    PM10. When the EPA completed a new review of the 
scientific evidence in the mid-eighties, its conclusions led it to 
revise the particulate NAAQS to focus more narrowly on those 
particulates less than 10 microns in diameter, or PM10. The 
standard issued in 1987 contained two components: an annual average 
limit of 150 g/m3, and a 24-hour limit of 50 
g/m3. This new standard required the states to 
reevaluate their situations and, if they had areas that exceeded the 
new PM10 limit, to refocus their compliance plans on 
reducing those particulates smaller than 10 microns in size. Sources of 
PM10 include power plants, iron and steel production, 
chemical and wood products

[[Page 58133]]

manufacturing, wind-blown and roadway fugitive dust, secondary aerosols 
and many natural sources.
    Some state implementation plans required surface mines to take 
actions to help the state meet the PM10 standard. In 
particular, some surface mines in Western states were required to 
control the coarser particles--e.g., by spraying water on roadways to 
limit dust. The mining industry has objected to such controls, arguing 
that the coarser particles do not adversely impact health, and has 
sought to have them excluded from the EPA ambient air standards (Shea, 
1995; comments of Newmont Gold Company, March 11, 1997, EPA docket 
number A-95-54, IV-D-2346).
    PM2.5. The next scientific review was completed in 1996, 
following suit by the American Lung Association and others. A proposed 
rule was published in November of 1996, and, after public hearings and 
review by the Office of the President, a final rule was promulgated on 
July 18, 1997 (62 FR 38651).
    The new rule further modifies the standard for particulate matter. 
Under the new rule, the existing national ambient air quality standard 
for PM10 remains basically the same--an annual average limit 
of 150 g/m3 (with some adjustment as to how this is 
measured for compliance purposes), and a 24-hour ceiling of 50 
g/m3. In addition, however, a new NAAQS has now 
been established for ``fine particulate matter'' that is less than 2.5 
microns in size. The PM2.5 annual limit is set at 15 
g/m3, with a 24-hour ceiling of 65 g/
m3.
    The basis for the PM2.5 NAAQS is a new body of 
scientific data suggesting that particles in this size range are the 
ones responsible for the most serious health effects associated with 
particulate matter. The evidence was thoroughly reviewed by a number of 
scientific panels through an extended process. (A chart of the 
scientific review process is available on EPA's web site--http://
ttnwww.rtpnc.epa.gov/naaqspro/pmnaaqs.gif). The proposed rule resulted 
in considerable press attention, and hearings by Congress, in which 
this scientific evidence was further discussed. Following a careful 
review, President Clinton announced his concurrence with the rulemaking 
in light of the scientific evidence of risk. However, the 
implementation schedule for the rule is long enough so that the next 
review of the science is scheduled to be completed before the states 
are required to meet the new NAAQS for PM2.5--hence, 
adjustment of the standard is still possible before implementation.
    Implications for the Mining Community. As noted earlier in this 
part, diesel particulate matter is mostly less than 1.0 micron in size. 
It is, therefore, a fine particulate. The body of evidence of human 
health risk from environmental exposure to fine particulates must, 
therefore, be considered in assessing the risk of harm to miners of 
occupational exposure to one type of fine particulate--diesel 
particulate. MSHA has accordingly done so in its risk assessment (see 
Part III of this preamble).
    (6) Controlling Diesel Particulate Emissions in Mining--a Toolbox. 
Efforts to control diesel particulate emissions have been under review 
for some time within the mining community, and accordingly, there is 
considerable practical information available about controls--both in 
general terms, and with respect to specific mining situations.
    Workshops. In 1995, MSHA sponsored three workshops ``to bring 
together in a forum format the U.S. organizations who have a stake in 
limiting the exposure of miners to diesel particulate (including) mine 
operators, labor unions, trade organizations, engine manufacturers, 
fuel producers, exhaust aftertreatment manufacturers, and academia.'' 
(McAteer, 1995). The sessions provided an overview of the literature 
and of diesel particulate exposures in the mining industry, state-of-
the-art technologies available for reducing diesel particulate levels, 
presentations on engineering technologies toward that end, and 
identification of possible strategies whereby miners' exposure to 
diesel particulate matter can be limited both practically and 
effectively. One workshop was held in Beckley, West Virginia on 
September 12 and 13, and the other two were held on October 6, and 
October 12 and 13, 1995, in Mt Vernon, Illinois and Salt Lake City, 
Utah, respectively. A transcript was made. During a speech early the 
next year, the Deputy Assistant Secretary for MSHA characterized what 
took place at these workshops:

    The biggest debate at the workshops was whether or not diesel 
exhaust causes lung cancer and whether MSHA should move to regulate 
exposures. Despite this debate, what emerged at the workshops was a 
general recognition and agreement that a health problem seems to 
exist with the current high levels of diesel exhaust exposure in the 
mines. One could observe that while all the debate about the studies 
and the level of risk was going on, something else interesting was 
happening at the workshops: one by one miners, mining companies, and 
manufacturers began describing efforts already underway to reduce 
exposures. Many are actively trying to solve what they clearly 
recognize is a problem. Some mine operators had switched to low 
sulfur fuel that reduces particulate levels. Some had increased mine 
ventilation. One company had tried a soy-based fuel and found it 
lowered particulate levels. Several were instituting better 
maintenance techniques for equipment. Another had hired extra diesel 
mechanics. Several companies had purchased electronically 
controlled, cleaner, engines. Another was testing a prototype of a 
new filter system. Yet another was using disposable diesel exhaust 
filters. These were not all flawless attempts, nor were they all 
inexpensive. But one presenter after another described examples of 
serious efforts currently underway to reduce diesel emissions. 
(Hricko, 1996).

    Toolbox. In March of 1997, MSHA issued, in draft form, a 
publication entitled ``Practical Ways to Control Exposure to Diesel 
Exhaust in Mining--a Toolbox''. The draft publication was disseminated 
by MSHA to all underground mines known to use diesel equipment and 
posted on MSHA's Web site. Following comment, the Toolbox was finalized 
in the Fall of 1997 and disseminated. For the convenience of the mining 
community, a copy is appended to the end of this document.
    The material on controls is organized as a ``Toolbox'' so that mine 
operators have the option of choosing the control technology that is 
most applicable to their mining operation for reducing exposures to 
dpm. The Toolbox provides information about nine types of controls that 
can reduce dpm emissions or exposures: low emission engines; fuels; 
aftertreatment devices; ventilation; enclosed cabs; engine maintenance; 
work practices and training; fleet management; and respiratory 
protective equipment.
    The Estimator. MSHA has developed a model that can help mine 
operators evaluate the effect of alternative controls on dpm 
concentrations. The model is in the form of a template that can be used 
on standard computer spreadsheet programs; as information about a new 
combination of controls is entered, the results are promptly displayed. 
A complete description of this model, referred to as ``the Estimator,'' 
and several examples, are presented in Part V of this preamble. MSHA 
intends to make this model widely available to the mining community, 
and hopes to receive comments in connection with this rulemaking based 
on the results of estimates conducted with this model.
    History of diesel aftertreatment devices in mining. For many years, 
the majority of the experience has been with the use of oxidation 
catalytic converters (OCCs), but in more recent years both

[[Page 58134]]

ceramic and paper filtration systems have also been used more widely.
    OCCs began to be used in underground mines in the 1960's to control 
carbon monoxide, hydrocarbons and odor (Haney, Saseen, Waytulonis, 
1997). That use has been widespread. It has been estimated that more 
than 10,000 OCCs have been put into the mining industry over the years 
(McKinnon, dpm Workshop, Beckley, WV, 1995).
    When such catalysts are used in conjunction with low sulfur fuel, 
there is a reduction of up to 90 percent of carbon monoxide, 
hydrocarbons and aldehyde emissions, and nitric oxide can be 
transformed to nitrogen dioxide. Moreover, there is also an 
approximately 20 percent reduction in diesel particulate mass. The 
diesel particulate reduction comes from the elimination of the soluble 
organic compounds that, when condensed through the cooling phase in the 
exhaust, will attach to the elemental carbon cores of diesel 
particulate. Unfortunately, this effect is lost if the fuel contains 
more than 0.05 percent sulfur. In such cases, sulfates can be produced 
which ``poison'' the catalyst, severely reducing its life. With the use 
of low sulfur fuel, some engine manufacturers have certified diesel 
engines with catalytic converter systems to meet EPA requirements for 
lower particulate levels (see Section 4 of this part).
    The particulate trapping capabilities of some OCCs are even higher. 
In 1995, the EPA implemented standards requiring older buses in urban 
areas to reduce the dpm emissions from rebuilt bus engines (40 CFR 
85.1403). Aftertreatment manufacturers developed catalytic converter 
systems capable of reducing dpm by 25%. Such systems are available for 
larger diesel engines common in the underground metal and nonmetal 
sector.
    Other types of aftertreatment devices capable of more significant 
reductions in particulate levels began to be developed for commercial 
applications following EPA rules in 1985 limiting diesel particulate 
emissions from heavy duty diesel engines. The wall flow type ceramic 
honeycomb diesel particulate filter system was initially the most 
promising approach (SAE, SP-735, 1988). However, due to the extensive 
work performed by the engine manufacturers on new technological designs 
of the diesel engine's combustion system, and the use of low sulfur 
fuel, particulate traps turned out to be unnecessary to comply with the 
EPA standards of the time.
    While this work was underway, efforts were also being made to 
transfer this aftertreatment technology to the mining industry. The 
former Bureau of Mines investigated the use of catalyzed diesel 
particulate filters in underground mines in the United States (BOM, RI-
9478, 1993). The investigation demonstrated that filters could work, 
but that there were problems associated with their use on individual 
unit installations, and the Bureau made recommendations for 
installation of ceramic filters on mining vehicles. But as noted by one 
commenter at one of the MSHA workshops in 1995, ``while ceramic filters 
give good results early in their life cycle, they have a relatively 
short life, are very expensive and unreliable.'' (Ellington, dpm 
Workshop, Salt Lake City, UT, 1995).
    Canadian mines also began to experiment with ceramic traps in the 
1980's with similar results (BOM, IC 9324, 1992). Work in Canada today 
continues under the auspices of the Diesel Emission Evaluation Program 
(DEEP), established by the Canadian Centre for Mineral and Energy 
Technology in 1996 (DEEP Plenary Proceedings, November 1996). The goals 
of DEEP are to: (1) evaluate aerosol sampling and analytical methods 
for dpm; and (2) evaluate the in-mine performance and costs of various 
diesel exhaust control strategies.
    Work with ceramic filters in the last few years has led to the 
development of the ceramic fiber wound filter cartridge (SAE, SP-1073, 
1995). The ceramic fiber has been reported by the manufacturer to have 
dpm reduction efficiencies up to 80 percent. This system has been used 
on vehicles to comply with German requirements that all diesel engines 
used in confined areas be filtered. Other manufacturers have made the 
wall flow type ceramic honeycomb dpm filter system commercially 
available to meet the German standard. In the case of some engines, a 
choice of the two types is available; but depending upon horsepower, 
this may not always be the case.
    In the early 1990's, MSHA worked with the former Bureau of Mines 
and a filter manufacturer to successfully develop and test a pleated 
paper filter for wet water scrubber systems of permissible diesel 
powered equipment. The dpm reduction from these filters has been 
determined in the field by the former BOM to be up to 95% (BOM, IC 
9324). The same type of filter has been used in recently developed dry 
systems for permissible machines, with reported laboratory reductions 
in dpm of 98% (Paas, dpm Workshop, Beckley WV, 1995).
    ANPRM Comments. The ANPRM requested information about several kinds 
of work practices that might be useful in reducing dpm concentrations. 
These comments were provided well before the workshops mentioned above, 
and before MSHA issued its diesel equipment standard for underground 
coal mines, and are thus somewhat dated. But, solely to illustrate the 
range of comments received, the following sections review the comments 
concerning certain work practices--fuel type, fuel additives, and 
maintenance practices.
    Type of Diesel Fuel Required. It has been well established that the 
quality of diesel fuel influences emissions. Sulfur content, cetane 
number, aromatic content, density, viscosity, and volatility are 
interrelated fuel properties which can influence emissions. Sulfur 
content can have a significant effect on diesel emissions.
    Use of low sulfur diesel fuel reduces the sulfate fraction of dpm 
matter emissions, reduces objectionable odors associated with diesel 
exhaust and allows oxidation catalysts to perform properly. The use of 
low sulfur fuel also reduces engine wear and maintenance costs. Fuel 
sulfur content is a particularly important parameter when the fuel is 
used in low emission diesel engines. Low sulfur diesel fuel is 
available nationwide due to EPA regulations (40 CFR Parts 80 and 86). 
In MSHA's ANPRM, information was requested on what reduction in 
concentration of diesel particulate can be achieved through the use of 
low sulfur fuel. Information was also solicited as to whether the use 
of low sulfur fuel reduces the hazard associated with diesel emissions.
    Responses from commenters stated that there would be a positive 
reduction in particulate with the use of low sulfur fuel. One commenter 
stated that the brake specific exhaust emissions (grams/brake 
horsepower-hour) of particulate would decrease by about 0.06 g/bhp-hr 
for a fuel sulfur reduction of 0.25 weight percent sulfur. The 
particulate reduction effect is proportional to the change in sulfur 
content. Another commenter stated that a typical No. 2 diesel fuel 
containing 0.25 percent weight sulfur will include 1 to 1.6 grams of 
sulfate particulate per gallon of fuel consumed. A fuel containing 0.05 
percent weight sulfur will reduce sulfate particulate to 0.2-0.3 grams 
per gallon of fuel consumed, an 80 percent reduction.
    In responding to the question on whether reducing the sulfur 
content of the fuel will reduce the health hazard associated with 
diesel emissions,

[[Page 58135]]

several commenters stated that they knew of no evidence that sulfur 
reduction reduces the hazard of the particulate. MSHA also is not aware 
of any data supporting the proposition that reducing the sulfur content 
of the fuel will reduce the health hazard associated with diesel 
emissions. However, in the preamble to the final rule for the EPA 
requirement for the use of low sulfur fuel, EPA stated that there were 
a number of benefits which could be attributed to lowering the sulfur 
content of diesel fuel. The first area was in exhaust aftertreatment 
technology. Reductions in fuel sulfur content will result in small 
reductions in sulfur compounds being emitted. This will cause the whole 
particulate concentration from the engine to be reduced. However, the 
number of carbon particles are is not reduced, therefore, the total 
carbon concentration would be the same.
    The major benefit of using low sulfur fuel is that the reduction of 
sulfur allows for the use of some aftertreatment devices such as 
catalytic converters, and catalyzed particulate traps which were 
prohibited with fuels of high sulfur content (greater than 0.05 percent 
sulfur). The high sulfur content led to sulfate particulate that when 
passed through the catalytic converter or catalyzed traps was changed 
to sulfuric acid when the sulfates came in contact with water vapor. 
Using low sulfur fuel permits these devices to be used.
    The second area of benefits that the EPA noted was that of reduced 
engine wear with the use of low sulfur fuel. Reducing engine wear will 
help maintain engines in their near manufactured condition that would 
help limit increases in particulate matter due to lack of maintenance 
or age of the engine.
    Other questions posed in the ANPRM requested information concerning 
the differences in No. 1 and No. 2 diesel fuel regarding particulate 
formation; the current sulfur content of diesel fuel used in mines; and 
when would 0.05 percent sulfur fuel be available to the mining 
industry.
    In response to those questions, commenters stated that a difference 
in No. 1 and No. 2 fuel regarding particulate formation would be that 
No. 1 fuel typically has less sulfur than No. 2 fuel and would 
therefore be expected to produce less particulate. Also, the No. 1 fuel 
has a lower density, boiling range and aromatic content and a higher 
cetane number. All of these fuel property differences tend to cause 
lower particulate emissions.
    Commenters also stated that the sulfur content of fuels 
commercially available for diesel-powered equipment can vary from 
nearly zero to 1 percent. The national average sulfur content for 
commercial No. 2 diesel fuel is approximately 0.25 percent. One 
commenter stated that sulfur content varied from region to region and 
the National Institute of Petroleum and Energy Research survey could be 
used to get the answers for specific regions.
    Commenters noted that low sulfur fuel, less than 0.05 percent 
sulfur, would be available for on-highway use as mandated by the EPA by 
October 1993. Also, California requires the statewide availability of 
0.05 percent sulfur fuel for all diesel engine applications by the same 
date. Although the EPA mandate ensures that low sulfur fuel will be 
available throughout the nation, commenters indicated the availability 
for off-road and mining application was uncertain at that time.
    The ANPRM also requested information on the differences in the per 
gallon costs among No. 1, No. 2 and 0.05 percent sulfur fuel; how much 
fuel is used annually in the mining industry; and what would be the 
economic impact on mining of using 0.05 percent sulfur fuel. In 
response, commenters stated that No. 1 fuel typically costs the user 10 
to 20 percent more than does No. 2 fuel. They also stated that the 
price of 0.05 percent sulfur fuel will eventually be set by the 
competitive market conditions. No information was submitted for 
accurately estimating fuel usage costs to the industry. The economic 
impact on the mining industry of using 0.05 percent fuel will vary 
greatly from mine to mine. Factors influencing that cost are a mine's 
dependence on diesel powered equipment, the location of the mine and 
existing regulation. Mines relying heavily on diesel equipment will be 
most impacted.
    Another commenter stated that the price for 0.05 percent fuel is 
forecast to average about 2 cents per gallon higher than the price for 
typical current No. 2 fuel. Kerosene and No. 1 distillate are forecast 
as 2 to 4 cents per gallon above 0.05 percent fuel and 4 to 6 cents 
above current No. 2 fuel. A recent census of mining and manufacturing 
dated 1987 showed mining industry energy consumption from all sources 
to total 1968.4 trillion BTU per year. Coal mining alone used 9.96 
million barrels annually of distillate, at a cost of 258.1 million 
dollars. Included in these quantities was diesel fuel for surface 
equipment and vehicles at or around the mine site. The commenter also 
stated that applying a cost increase of 2 cents per gallon to the total 
industry distillate consumption would increase annual fuel costs by 
$24.3 million. For coal mining only, the cost increase would be $8.4 
million annually.
    While MSHA does not have an opinion on the accuracy of the 
information received in this regard, it is in any event dated. Since 
the time that the ANPRM was open, the availability of low sulfur fuel 
has become more common. Comments received at MSHA's Diesel Workshops 
indicate that low sulfur fuel is readily available and that all that is 
needed to obtain it is to specify the desired fuel quality on the 
purchase order. The differences in the fuel properties of No. 1 and No. 
2 fuel are consistent with specifications provided by ASTM and other 
literature information concerning fuel properties.
    Fuel Additives. Information relative to fuel additives was 
requested in MSHA's ANPRM. The ANPRM requested information on the 
availability of fuel additives that can reduce dpm or additives being 
developed; what diesel emissions reduction can be expected through the 
use of these fuel additives; the cost of additives and advantages to 
their use; and will these fuel additives introduce other health 
hazards. One commenter stated that cetane improvers and detergent 
additives can reduce dpm from 0 to 10 percent. The data, however, does 
not indicate consistent benefits as in the case with sulfur reduction. 
Oxygenate additives can give larger benefits, as with methanol, but 
then the oxygenate is not so much an additive as a fuel blend. Another 
commenter stated the cost depended on the price and concentration of 
the additive. This commenter estimated the cost to be between three and 
seven cents per gallon of fuel.
    Another commenter stated that some additives are used for reducing 
injector tip fouling, other alternative additives also are offered 
specifically for the purpose of reducing smoke or dpm such as 
organometallic compounds, i.e., copper, barium, calcium, iron or 
platinum; oxygenate supplements containing alcohols or peroxides; and 
other proprietary hydrocarbons. The commenter did not quantify the 
expected reductions in dpm.
    The former Bureau of Mines commented on an investigation of barium-
based, manganese based, and ferrocene fuel additives. Details of the 
investigation are found in the literature (BOM, IC 9238, 1990). In 
general, fuel additives are not widely used by the mining industry to 
reduce dpm or to reduce regeneration temperatures in ceramic 
particulate filters. Research has shown aerosol reductions of about 30 
percent without significant adverse impacts although new pollutants

[[Page 58136]]

derived from the fuel additive remain a question.
    One commenter stated that a cetane improver and detergent additives 
should not exceed 1 cent per gallon at the treat rates likely to be 
used. The use of oxygenates depends on which one and how much but would 
be perhaps an order of magnitude higher than the use of a cetane 
improver. One commenter also added that any fuel economy advantages 
would be very small.
    In response to the creation of a health hazard when using 
additives, one commenter stated that excessive exposure to cetane 
improver (alkyl nitrates), which is hazardous to humans, requires 
special handling because of poor thermal stability. Detergent additives 
are similar to those used in gasoline and probably have similar safety 
and health issues. Except at low load operation, additives are not 
likely to result in any significant quantity in the exhaust. Another 
commenter stated that the effect on human health of new chemical 
exhaust species that may result from the use of some of these additives 
has not been determined. Engine manufacturers also are concerned about 
the use of such products because their effectiveness has not always 
been adequately demonstrated and, in many cases, the effect on engine 
durability has not been well-documented for different designs and 
operating conditions.
    MSHA agrees with the commenters that fuel additives can affect 
engine performance and exhaust emissions. MSHA's experience with 
additives has shown that they can enhance fuel quality by increasing 
the cetane number, depressing the cloud point, or in the case of a 
barium based additive, affect the combustion process resulting in a 
reduction of particulate output. MSHA's experience also has shown that 
in most cases the effects of an additive on engine performance or 
emissions cannot be adequately determined without extensive research. 
The additives listed on EPA's list of ``registered additives'' meet the 
requirements of EPA's standards in 40 CFR Part 79.
    MSHA is concerned about the use of untested fuel additives. A large 
number of additives are currently being marketed to reduce emissions. 
These additives include cetane improvers that increase the cetane 
number of the fuel, which may reduce emissions and improve starting; 
detergents that are used primarily to keep the fuel injectors clean; 
dispersants or surfactants that prevent the formation of thicker 
compounds that can form deposits on the fuel injectors or plug filters. 
While the use of many of these additives will result in reduced 
particulate emission, some have been found to introduce harmful agents 
into the environment. For this reason, it is a good idea to limit the 
use of additives to those that have been registered by the EPA.
    Maintenance Practices. The ANPRM requested information concerning 
what maintenance procedures are effective in reducing diesel 
particulate emissions from existing diesel-powered equipment, and what 
additional maintenance procedures would be required in conjunction with 
anticipated developments of new diesel particulate reduction 
technology. Information was also requested about the amount of time to 
perform the maintenance procedures and if any, loss of production time.
    Commenters stated that some maintenance procedures have a very 
dramatic impact on particulate emissions, while other procedures that 
are equally important for other reasons have little or no impact at all 
on particulates. Another commenter stated that maintenance procedures 
are intended to ensure that the engine operates and will continue to 
operate as intended. Such procedures will not reduce diesel particulate 
below that of the new, original equipment. A commenter stated that the 
diesel engine industry experience has demonstrated that emissions 
deterioration over the useful life of an engine is minimal.
    Commenters stated that depending on the implied technology, the 
need for additional maintenance will be based on complexity of the 
control devices. Also, time for maintenance will be dependent on 
complexity of the control device. Some production loss will occur due 
to increased maintenance procedures.
    MSHA agrees with the commenters' view that maintenance does affect 
engine emissions, some more dramatically than others. Research has 
clearly shown that without engine maintenance, all engine emissions 
will increase greatly. For example, the former Bureau of Mines, in 
conjunction with Southwest Research, conducted extensive research on 
the effects of maintenance on diesel engines which indicated this 
result (BOM contract H-0292009, 1979). MSHA agrees that emissions 
increase is minimal over the useful life of the engine only when proper 
maintenance is performed daily. However, MSHA believes that with the 
awareness of the increased maintenance, production may not be lost due 
to the increased time that the machines are able to operate without 
unwanted down time due to poor maintenance practices.
    MSHA's diesel ``Toolbox'' includes an extensive discussion on the 
importance of maintenance. It reminds operators and diesel maintenance 
personnel of the basic systems on diesel engines that need to be 
maintained, and how to avoid various problems. It includes suggestions 
from others in the mining community, and information on their success 
or difficulties in this regard.
    (7) Existing Mining Standards that Limit Miner Exposure to 
Occupational Diesel Particulate Emissions. MSHA already has in place 
various requirements that help to control miner exposure to diesel 
emissions in underground mines--including exposure to diesel 
particulate. These include ventilation requirements, engine approval 
requirements, and explicit restrictions on the concentration of various 
gases in the mine environment.
    In addition, in 1996, MSHA promulgated a rule governing the use of 
diesel-powered equipment in underground coal mines (61 FR 55412). While 
the primary focus of the rulemaking was to promote the safe use of 
diesel engines in the hazardous environment of underground coal mines, 
various parts of the rule will help to control exposure to harmful 
diesel emissions in those mines. The new rule revised and updated 
MSHA's diesel engine approval requirements and the ventilation 
requirements for underground coal mines using diesel equipment, and 
established requirements concerning diesel fuel sulfur content and the 
idling, maintenance and emissions testing of diesel engines in 
underground coal mines.
    Background. Beginning in the 1940s, mining regulations were 
promulgated to promote the safe and healthful use of diesel engines in 
underground mines. In 1944, Part 31 established procedures for limiting 
the gaseous emissions and establishing the recommended dilution air 
quantity for mine locomotives that use diesel fuel. In 1949, Part 32 
established procedures for testing of mobile diesel-powered equipment 
for non-coal mines. In 1961, Part 36 was added to provide requirements 
for the use of diesel equipment in gassy noncoal mines, in which 
engines must be temperature controlled to prevent explosive hazards. 
These rules responded to research conducted by the former Bureau of 
Mines.
    Continued research by the former Bureau of Mines in the 1950s and 
1960s led to refinements of its ventilation recommendations, 
particularly when multiple engines are in use. An airflow of 100 to 250 
cfm/bhp was

[[Page 58137]]

recommended for engines that have a properly adjusted fuel to air ratio 
(Holtz, 1960). An additive ventilation requirement was recommended for 
operation of multiple diesel units, which could be relaxed based on the 
mine operating procedures. This approach was subsequently refined to 
become a 100-75-50 percent guideline (MSHA Policy Memorandum 81-19MM, 
1981). Under this guideline, when multiple pieces of diesel equipment 
are operated, the required airflow on a split of air would be the sum 
of: (a) 100 percent of the nameplate quantity for the vehicle with the 
highest nameplate air quantity requirement; (b) 75 percent of the 
nameplate air quantity requirement of the vehicle with the next highest 
nameplate air quantity requirement; and (c) 50 percent of the nameplate 
airflow for each additional piece of diesel equipment.
    Diesel Equipment Rule. On October 6, 1987, MSHA published in the 
Federal Register (52 FR 37381) a notice establishing a committee to 
advise the Secretary of Labor on health and safety standards related to 
the use of diesel-powered equipment in underground coal mines. The 
``Mine Safety and Health Advisory Committee on Standards and 
Regulations for Diesel-Powered Equipment in Underground Coal Mines'' 
(the Advisory Committee) addressed three areas of concern: the approval 
of diesel-powered equipment, the safe use of diesel equipment in 
underground coal mines, and the protection of miners' health. The 
Advisory Committee submitted its recommendations in July 1988.
    With respect to the approval of diesel-powered equipment, the 
Advisory Committee recommended that all diesel equipment except for a 
limited class, be approved for use in underground coal mines. This 
approval would involve both safety (e.g., fire suppression systems) and 
health factors (e.g., maximum exhaust emissions).
    With respect to the safe use of diesel equipment in underground 
coal mines, the Advisory Committee recommended that standards be 
developed to address the safety aspects of the use of diesel equipment, 
including such concerns as equipment maintenance, training of 
mechanics, and the storage and transport of diesel fuel.
    The Advisory Committee also made recommendations concerning miner 
health, discussed later in this section.
    As a result of the Advisory Committee's recommendations on approval 
and safe use, MSHA developed and, on October 25, 1996, promulgated as a 
final rule, standards for the ``Approval, Exhaust Gas Monitoring, and 
Safety Requirements for the Use of Diesel-Powered Equipment in 
Underground Coal Mines'' (61 FR 55412).
    The October 25, 1996 final rule on diesels focuses on the safe use 
of diesels in underground coal mines. Integrated requirements are 
established for the safe storage, handling, and transport of diesel 
fuel underground, training of mine personnel, minimum ventilating air 
quantities for diesel powered equipment, maintenance requirements, fire 
suppression, and design features for nonpermissible machines. While the 
focus was on safety, certain rules related to emissions are included in 
the final rule. For example, the final rule requires maintenance on 
diesel powered equipment. Regular maintenance on diesel powered 
equipment should keep the diesel engine and vehicle operation at its 
original or baseline condition. However, as a check that the 
maintenance is being performed, MSHA wrote a standard for checking the 
gaseous CO emission levels on permissible and heavy duty outby machines 
to determine the need for maintenance. The CO check requires that a 
regular repeatable loaded engine condition be run on a weekly basis and 
the CO measured. Carbon monoxide is a good indicator of engine 
condition. If the CO measurement increases to a higher concentration 
than what was normally measured during the past weekly checks, then a 
maintenance person would know that either the regular maintenance was 
missed or a problem has developed that is more significant than could 
be identified by a general daily maintenance program.
    Consistent with the Advisory Committee's recommendation, the final 
rule, among other things, requires that virtually all diesel-powered 
engines used in underground coal mines be approved by MSHA (30 CFR Part 
7 (approval requirements), Part 36 (permissible machines defined), and 
Part 75 (use of such equipment in underground coal mines). The approval 
requirements, among other things, are designed to require clean-burning 
engines in diesel-powered equipment (61 FR 55417). In promulgating the 
final rule, MSHA recognized that clean-burning engines are ``critically 
important'' to reducing toxic gasses to levels that can be controlled 
through ventilation. (Id.). To achieve the objective of clean-burning 
engines, the rule sets performance standards which must be met for 
virtually all diesel-powered equipment in underground coal mines (30 
CFR Part 7).
    Consistent with the recommendation of the Advisory Committee, the 
technical requirements for approved diesel engines include undiluted 
exhaust limits for carbon monoxide and oxides of nitrogen (61 FR 
55419). As recommended by the Advisory Committee, the limits for these 
gasses are derived from existing 30 CFR Part 36 (61 FR 55419). Also, 
consistent with the recommendation of the Advisory Committee, the final 
rule requires that as part of the approval process, ventilating air 
quantities necessary to maintain the gaseous emissions of diesel 
engines within existing required ambient limits be set (61 FR 55420). 
As recommended by the Advisory Committee, the ventilating air 
quantities are required to appear on the engine's approval plate (61 FR 
55421).
    The final rule also implements the Advisory Committee's 
recommendation that a particulate index be set for diesel engines (61 
FR 55421). Although, as discussed below, there is not yet a specific 
standard limiting miners' exposure to diesel particulate, the 
particulate index is nonetheless useful in providing information to the 
mining community so that operators can compare the particulate levels 
generated by different engines (61 FR 55421).
    Also consistent with the recommendation of the Advisory Committee, 
the final rule addresses the monitoring and control of gaseous diesel 
exhaust emissions (30 CFR part 70; 61 FR 55413). In this regard, the 
final rule requires that mine operators take samples of carbon monoxide 
and nitrogen dioxide (61 FR 55413, 55430-55431). Samples exceeding an 
action level of 50 percent of the threshold limits set forth in 30 CFR 
75.322, trigger corrective action by the mine operator (30 CFR part 70, 
61 FR 55413). Also consistent with the Advisory Committee's 
recommendation, the final rule requires that diesel-powered equipment 
be adequately maintained (30 CFR 75.1914; 61 FR 55414). Among other 
things, as recommended by the Advisory Committee, the rule requires the 
weekly examination of diesel-powered equipment, including testing of 
undiluted exhaust emissions for certain types of equipment (30 CFR 
75.1914(g)). In addition, consistent with the Advisory Committee's 
recommendation, operators are required to establish programs to ensure 
that those performing maintenance on diesel equipment are qualified (61 
FR 55414). As explained in the preamble, maintenance requirements were 
included because of MSHA's recognition that inadequate equipment 
maintenance can, among other things, result in increased levels of 
harmful gaseous and particulate components

[[Page 58138]]

from diesel exhaust (61 FR 55413-55414).
    Consistent with the Advisory Committee's recommendation, the final 
rule also requires that underground coal mine operators use low sulfur 
diesel fuel (30 CFR 75.1901; 61 FR 55413). The use of low sulfur fuel 
lowers not only the amount of gaseous emissions, but also the amount of 
diesel particulate emissions. (Id.). To further reduce miners' exposure 
to diesel exhaust, the final rule prohibits operators from 
unnecessarily idling diesel-powered equipment (30 CFR 75.1916(d)).
    Also consistent with the recommendation of the Advisory Committee, 
the final rule establishes minimum air quantity requirements in areas 
of underground coal mines where diesel-powered equipment is operated 
(30 CFR 75.325). As set forth in the preamble, MSHA believes that 
effective mine ventilation is a key component in the control of miners' 
exposure to gasses and particulate emissions generated by diesel 
equipment (61 FR 55433). The final rule also requires generally that 
mine operators maintain the approval plate quantity minimum airflow in 
areas of underground coal mines where diesel-powered equipment is 
operated (30 CFR 75.325 \3\).
---------------------------------------------------------------------------

    \3\ On December 23, 1997, the National Mining Association and 
Energy West Mining Company filed petitions for review of the final 
rule. National Mining Association v. Secretary of Labor, Nos. 96-
1489 and 96-1490. These cases were consolidated and held in abeyance 
pending discussions between the mining industry and the Secretary. 
On March 19, 1998, petitioners filed an Unopposed Joint Motion for 
Voluntary Dismissal. In April 1998, the Court granted the Motion for 
Dismissal.
---------------------------------------------------------------------------

    The diesel equipment rule will help the mining community use 
diesel-powered equipment more safely in underground coal mines. As 
discussed throughout this preamble, the diesel equipment rule has many 
features which, though it was not their primary purpose, will 
incidently reduce harmful diesel emissions in underground coal mines--
including the particulate component of these emissions. (The 
requirements of the diesel equipment rule are highlighted with a 
special typeface in MSHA's publication, ``Practical Ways to Control 
Exposure to Diesel Exhaust in Mining--a Toolbox''). An example is the 
requirement in the diesel equipment rule that all engines used in 
underground coal mines be approved engines, and be maintained in 
approved condition--thus reducing emissions at the source.
    In developing this safety rule, however, MSHA did not explicitly 
consider the risks to miners of a working lifetime of dpm exposure at 
very high levels, nor the actions that could be taken to specifically 
reduce those exposure levels in underground coal mines. Moreover, the 
rule does not apply to the remainder of the mining industry, where the 
use of diesel machinery is much more intense than in underground coal.
    Gas limits. Various organizations have established or recommended 
limits for many of the gasses occurring in diesel exhaust. Some of 
these are listed in Table II-2, together with information about the 
limits currently enforced by MSHA. MSHA requires mine operators to 
comply with gas specific threshold limit values (TLV(TM)s) recommended 
by the American Conference of Governmental Industrial Hygienists 
(ACGIH) in 1972 (for coal mines) and in 1973 (for metal and nonmetal 
mines).

BILLING CODE 4510-43-P

[[Page 58139]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.023



BILLING CODE 4510-43-C

[[Page 58140]]

    In 1989, MSHA proposed changing some of these limits in the context 
of a proposed rule on air quality standards (54 FR 35760). Following 
opportunity for comment and hearings, a portion of that proposed rule, 
concerning control of drill dust, has been promulgated, but the other 
components are still under review. To change a limit at this point in 
time requires a regulatory action; the rule does not provide for their 
automatic updating.
(8) How Other Jurisdictions Are Restricting Occupational Exposure to 
Diesel Soot.
    On April 9, 1998, MSHA published a proposed rule to limit the 
exposure of underground coal miners to dpm. With this proposed rule, 
MSHA's rulemaking is the first effort by the Federal government to deal 
with the special risks faced by workers exposed to diesel exhaust on 
the job--because, as described in detail in the Part III of this 
preamble, miner exposures are an order of magnitude above those of any 
other group of workers. But others have been looking at the problem of 
exposure to diesel soot.
    MSHA's Final Rule for Underground Coal Mines. In 1996, MSHA 
published a final rule on addressing the safe use of diesels in 
underground coal mines. Integrated requirements are established for the 
safe storage, handling, and transport of diesel fuel underground, 
training of mine personnel, minimum ventilating air quantities for 
diesel powered equipment, maintenance requirements, fire suppression, 
and design features for nonpermissible machines.
    States. As noted in the first section of this part, few underground 
coal mines now use diesel engines. Several states have had bans on the 
use of such equipment: Pennsylvania, West Virginia, and Ohio.
    Recently, Pennsylvania has replaced its ban with a special law that 
permits the use of diesel-powered equipment in deep coal mines under 
certain circumstances. The Pennsylvania statute goes beyond MSHA's new 
regulation on the use of diesel-powered equipment in underground coal 
mines. Of particular interest is that it specifically addresses diesel 
particulate. The State did not set a limit on the exposure of miners to 
dpm, nor did it establish a limit on the concentration of dpm in deep 
coal mines. Rather, it approached the issue by imposing controls that 
will limit dpm emissions at the source.
    First, all diesel engines used in underground deep coal mines in 
Pennsylvania must be MSHA-approved engines with an ``exhaust emissions 
control and conditioning system'' that meets certain tests. (Article 
II-A, Section 203-A, Exhaust Emission Controls). Among these are dpm 
emissions from each engine no greater than ``an average concentration 
of 0.12 mg/m3 diluted by fifty percent of the MSHA approval 
plate ventilation for that diesel engine.'' In addition, any exhaust 
emissions control and conditioning system must include a ``Diesel 
Particulate Matter (DPM) filter capable of an average of ninety-five 
percent or greater reduction of dpm emissions.'' It also requires the 
use of an oxidation catalytic converter. Thus, the Pennsylvania statute 
requires the use of low-emitting engines, and then the use of 
aftertreatment devices that significantly reduce what particulates are 
emitted from these engines.
    The Pennsylvania law also has a number of other requirements for 
the safe use of diesel-powered equipment in the particularly hazardous 
environments of underground coal mines. Many of these parallel the 
requirements in MSHA's rule. Like MSHA's requirements, they too can 
result in reducing miner exposure to diesel particulate--e.g., regular 
maintenance of diesel engines by qualified personnel and equipment 
operator examinations. The requirements in the Pennsylvania law take 
into account the need to maintain the aftertreatment devices required 
to control diesel particulate (see, e.g., Section 217-A (b)(6)).
    West Virginia has also lifted its ban, subject to rules to be 
developed by a joint labor-management commission. MSHA understands that 
pursuant to the West Virginia law lifting the ban, the Commission has 
only a limited time to determine the applicable rules, or the matter is 
to be referred to an arbitrator for resolution.
    Other Countries. Concerns about air pollution have been a major 
impetus for most countries' standards on vehicle emissions, including 
diesel particulate. Most industrialized nations recognize the 
fundamental principle that their citizens should be protected against 
recognized health risks from air pollution and that this requires the 
control of particulate such as diesel exhaust. In November of 1995, for 
example, the government of the United Kingdom recommended a limit on 
PM10, and noted it would be taking further actions to limit airborne 
particulate matter (including a special study of dust from surface 
minerals workings).
    Concerns about international trade have been another impetus. 
Diesel engines are sold to an international market to power many types 
of industrial and nonindustrial machinery and equipment. The European 
Union manufacturers exported more than 50 percent of their products, 
mainly to South Korea, Taiwan, China, Australia, New Zealand and the 
United States. Germany and the United Kingdom, two major producers, 
have pushed for harmonized world standards to level the playing field 
among the various countries' engine producers and to simplify the 
acceptance of their products by other countries (Financial Times, 
1996). This includes products that must be designed to meet pollution 
standards. The European Union (EU) is now considering a proposal to set 
an EU-wide standard for the control of the emission of pollutants from 
non-road mobile machinery (Official Journal of European Communities, 
1995). The proposal would largely track that of the U.S. Environmental 
Protection Agency's final rule on the Control of Air Pollution 
Determination of Significance for Nonroad Sources and Emission 
Standards for New Nonroad Compression-Ignition Engines at or above 37 
kilowatts (50 HP)p (discussed in Section 3 of this part of the 
preamble).
    A third impetus to action has been the studies of the health 
effects of worker exposure to diesel exhaust--many of which have been 
epidemiological studies concerning workers in other countries. As noted 
in Part III of this preamble, the studies include cohorts of Swedish 
dock workers and bus garage workers, Canadian railway workers and 
miners, French workers, London transport workers, and Danish chimney 
sweeps.
    Below, the agency summarizes some information obtained on exposure 
limits of other countries. Due to differences in regulatory schemes 
among nations considering the effects of diesel exhaust, countries 
which have addressed the issue are more likely to have issued 
recommendations rather than a mandatory maximum exposure limit. Some of 
these may have issued mandatory design features for diesel equipment to 
assist in achieving the recommended exposure level. Measurement systems 
also vary.
    Germany. German legislation on dangerous substances classifies 
diesel engine emissions as carcinogenic. Therefore, diesel engines must 
be designed and operated using the latest technology to cut emissions. 
This always requires an examination to determine whether the respective 
operations and activities may be carried out using other types of less 
polluting equipment. If, as a result of the

[[Page 58141]]

examination, it is decided that the use of diesel engines is necessary, 
measures must be instituted to reduce emissions. Such measures can 
include low-polluting diesel engines, low sulphur fuels, regular 
maintenance, and, where technology permits, the use of particulate 
traps. To reduce exposure levels further, diesel engine emissions may 
be regulated directly at the source; ventilation systems may be 
required to be installed.
    The use of diesel vehicles in a fully or partly enclosed working 
space--such as in an underground mine--may be restricted by the 
government, depending on the necessary engine power or load capacity 
and on whether the relevant operation could be accomplished using a 
non-polluting vehicle, e.g. an electrically powered vehicle. When 
determining whether alternate equipment is to be used, the burden to 
the operator to use such equipment is also considered.
    In April of 1997, the following permissible exposure limits 
(TRK\4\) for diesel engine emissions were instituted for workplaces in 
mining.

    \4\ TRK is the technical exposure limit of a hazardous material 
that defines the concentration of gas, vapour or airborne 
particulates which is the minimum possible with current technology 
and which serves as a guide for necessary protective measures and 
monitoring in the workplace.
---------------------------------------------------------------------------

(1) non-coal underground mining and construction work: TRK = 0.3 mg/
m3 of colloid dust\5\
---------------------------------------------------------------------------

    \5\ Colloid dust is defined as that part of total respirable 
dust in a workplace that passes the alveolar ducts of the worker.
---------------------------------------------------------------------------

(2) other: TRK = 0.1 mg/m3 of colloid dust
(3) The average concentration of diesel engine emissions within a 
period of 15 minutes should never be higher than four times the TRK 
value.

    The TRK is ascertained by determining the fraction of elemental 
carbon in the colloid (fine) dust by coulometric analysis. Determining 
the fraction of elemental carbon always involves the determination of 
total organic carbon in the course of analysis. If the workplace 
analysis shows that the fraction of elemental carbon in total carbon 
(elemental carbon plus organic carbon) is lower than 50%, or is subject 
to major fluctuations, then the TRK limits total carbon in such 
workplaces to 0.15 mg/m3.
    Irrespective of the TRK levels, the following additional measures 
are considered necessary once the concentration reaches 0.1 mg/
m3 colloid dust:

(1) Informing employees concerned;
(2) Limited working hours for certain staff categories;
(3) Special working hours; and
(4) Medical checkups.

    If concentrations continue to fail to meet the TRK level, the 
employer must:
    (1) Provide appropriate, effective, hygienic breathing apparatus, 
and
    (2) Ensure that workers are not kept at the workplace for longer 
than absolutely necessary and that health regulations are observed.
    Workers must use the breathing apparatus if the TRK levels for 
diesel engine emissions at the work place are exceeded. Due to the 
interference of recognized analysis techniques in coal mining, it is 
currently impossible to ascertain exposure levels in the air in coal 
mines. As a consequence, the coal mining authorities require the use of 
special low-polluting engines in underground mining and impose special 
requirements on the supply of fresh air to the workplace.
    European Standards. On April 21, 1997, the draft of a European 
directive that applied to emissions from non-road mobile machinery was 
prepared. The directive proposed technical measures that would result 
in a reduction in emissions from internal-combustion engines (gasoline 
and diesel) installed in non-road mobile machinery, and type-approval 
procedures that would provide uniformity among the member nations for 
the approval of these engines.
    The directive proposed a two-stage process. Stage 1, proposed to 
begin December 31, 1997, was for three different engine categories:

--A: 130 kW <= P <= 560 kW,
--B: 75 kW <= P < 130 kW,
--C: 37 kW <= P < 75 kW.

    Stage 2, proposed to begin December 31, 1999, consisted of four 
engine categories being phased-in over a four-year period:

--D: after December 31,1999 for engines of a power output of 18 kW <= P 
< 37 kW,
--E: after December 31, 2000 for engines of a power output of 130 kW <= 
P <= 560 kW,
--F: after December 31, 2001 for engines of a power output of 75 kW <= 
P < 130 kW,
--G: after December 31, 2002 for engines of a power output of 37 kW <= 
P <= 75 kW.
    The emissions shown in the following table for carbon monoxide, 
hydrocarbons, oxides of nitrogen and particulates are to be met for the 
respective engine categories described for stage I.

----------------------------------------------------------------------------------------------------------------
                                                               Carbon                   Oxides of
                                                              Monoxide   Hydrocarbons    Nitrogen   Particulates
                   Net power  (P)  (kW)                       (P)  (g/     (HC)  (g/    (NoX)  (g/    (PT)  (g/
                                                                kWh)         kWh)          kWh)         kWh)
----------------------------------------------------------------------------------------------------------------
130  P < 560...................................          5.0           1.3          9.2          0.54
75  P < 130....................................          5.0           1.3          9.2          0.70
37  P < 75.....................................          6.5           1.3          9.2          0.85
----------------------------------------------------------------------------------------------------------------

    The engine emission limits that have to be achieved for stage II 
are shown in the following table. The emissions limits shown are 
engine-out limits and are to be achieved before any aftertreatment 
device is used.

----------------------------------------------------------------------------------------------------------------
                                                               Carbon                   Oxides of
                                                              Monoxide   Hydrocarbons    Nitrogen   Particulates
                   Net power  (P)  (kW)                       (P)  (g/     (HC)  (g/    (NoX)  (g/    (PT)  (g/
                                                                kWh)         kWh)          kWh)         kWh)
----------------------------------------------------------------------------------------------------------------
130  P < 560...................................          3.5           1.0          6.0           0.2
75  P < 130....................................          5.0           1.0          6.0           0.3
37  P < 75.....................................          5.0           1.3          7.0           0.4
18  P < 37.....................................          5.5           1.5          8.0           0.8
----------------------------------------------------------------------------------------------------------------


[[Page 58142]]

    Canada (Related developments in Canada). The Mining and Minerals 
Research Laboratories (MMRL) of the Canada Centre for Mineral and 
Energy Technology (CANMET), an arm of the Federal Department of Natural 
Resources Canada (NRCAN), began work in the early 1970s to develop 
measurement tools and control technologies for diesel particulate 
matter (dpm). In 1978, I.W. French and Dr. Anne Mildon produced a 
CANMET-sponsored contract study entitled: ``Health Implications of 
Exposure of Underground Mine Workers to Diesel Exhaust Emissions.'' In 
this document, an Air Quality Index (AQI) was developed involving 
several major diesel contaminants (CO, NO, NO2, SO2 and RCD--respirable 
combustible dust which is mostly dpm). These concentrations were 
divided by their then current permissible exposure limits, and the sum 
of the several ratios indicates the level of pollution in the mine 
atmosphere. The maximum value for this Index was fixed at 3.0. This 
criterion was determined by the known health hazard associated with 
small particle inhalation, and the known chemical composition of dpm, 
among other matters.
    Subsequently, in 1986, the Canadian Ad hoc Diesel Committee was 
formed from all segments of the mining industry, including: mine 
operators, the labor force, equipment manufacturers, research agencies 
including CANMET, and Canadian regulatory bodies. The objective was the 
identification of major problems for research and development 
attention, the undertaking of the indicated studies, and the 
application of the results to reduce the impact of diesel machines on 
the health of underground miners.
    In 1990-91, CANMET developed an RCD mine sampling protocol on 
behalf of the Ad hoc Committee. Then current underground sampling 
studies indicated an average ratio of RCD to dpm of 1.5. This factor 
accounted for the presence of other airborne combustible liquids 
including fuel, lubrication and particularly drilling oils, in addition 
to the dpm.
    The original 1978 French-Mildon study was updated under a CANMET 
contract in 1990. It recommended that the dpm levels be reduced to 0.5 
mg/m\3\ (suggesting a corresponding RCD level of 0.75 mg/m\3\).
    However, in 1991, the AD HOC Committee decided to set an interim 
recommended RCD level of 1.5 mg/m\3\ (the equivalent 1.0 mg/m\3\). This 
value matched the then recommended, but not promulgated, MSHA 
`Ventilation Index' value for dpm of 1.0 mg/m\3\. Consequently, all of 
the North American mining industry then seemed to be accepting the same 
maximum levels of dpm.
    It should be noted that for coal mine environments or other 
environments where a non-diesel carbonaceous aerosol is present, RCD 
analysis is not an appropriate measure of dpm levels.
    Neither CANMET nor the Ad hoc Committee is a regulatory body. In 
Canada, mining is regulated by the individual provinces and 
territories. However, the federal laboratories provide: research and 
development facilities, advice based on research and development, and 
engine/machine certification services, in order to assist the provinces 
in their diesel-related mining regulatory functions.
    Prior to the 1991 recommendation of the Ad hoc Committee, Quebec 
enacted regulations requiring: ventilation, a maximum of 0.25% sulfur 
content in diesel fuel; a prohibition on black smoke; exhaust cooling 
to a maximum temperature of 85 deg.C; and the setting of maximum 
contaminant levels. Since 1997, new regulations add the CSA Standard 
for engine certification, a maximum RCD level of 1.5 mg/m\3\, and the 
application of an exhaust treatment system.
    Further, after the Ad hoc Committee recommendation was published in 
1991 (RCDmax = 1.5 mg/m\3\), various provinces took the following 
actions:
    (1) Five provinces--British Columbia, Ontario, Quebec, New 
Brunswick, and Nova Scotia, and the Northwest Territories, adopted an 
RCD limit of 1.5 mg/m\3\.
    (2) Two others, Manitoba and Newfoundland/Labrador, have been 
adopting the ACGIH TLVs.
    (3) Two provinces, Alberta and Saskatchewan, and the Yukon 
Territory, continue to have no dpm limit.
    Most Canadian Inspectorates accept the CSA Standard for diesel 
machine/engine certification. This Standard specifies the undiluted 
Exhaust Quality Index (EQI) criterion for calculation of the 
ventilation in cfm, required for each diesel engine/machine. Fuel 
sulfur content, type of aftertreatment device and rated engine load 
factor are on-site, variable factors which may alter the ventilation 
ultimately required. Diesel fuel may not exceed 0.50% sulfur, and must 
have a minimum flash point of 52 deg.C. However, most mines in Canada 
now use fuel containing less than 0.05% sulfur by weight.
    In addition to limiting the RCD concentration, Ontario, established 
rules in 1994 that required diesel equipment to meet the Canadian 
Standards Association ``Non-Rail-Bound Diesel-Powered Machines for use 
in Non-Gassy Underground Mines'' (CSA M424.2-M90) Standard, excepting 
the ventilation assessment clauses. As far as fuel sulfur and 
flashpoint are concerned, Ontario is intending to change to: Smax = 
0.05% from 0.25%, and maximum fuel flash point = 38 deg.C from 
52 deg.C.
    New Brunswick, in addition to limiting the RCD concentration, 
requires mine operators to submit an ambient air quality monitoring 
plan. Diesel engines above 100 horsepower must be certified, and there 
is a minimum ventilation requirement of 105 cfm/bhp.
    Since 1996, the Ad hoc organization and the industry consortium 
called the Diesel Emissions Evaluation Program (DEEP) have been 
cooperating in a research and development program designed to reduce 
dpm levels in mines.
    World Health Organization (WHO). Environmental Health Criteria 171 
on ``Diesel Fuel and Exhaust Emissions'' is a 1996 monograph published 
under joint sponsorship of the United Nations Environment Programme, 
the International Labour Organisation, and the World Health 
Organization. The monograph provides a comprehensive review of the 
literature and evaluates the risks for human health and the environment 
from exposure to diesel fuel and exhaust emissions.
    The following tables compiled in the monograph show diesel engine 
exhaust limits for various exhaust components and illustrate that there 
is international concern about the amount of diesel exhaust being 
released into the environment.

                           Table II-3.--International Limit Values for Components of Diesel Exhaust Lightduty Vehicles (g/km)
--------------------------------------------------------------------------------------------------------------------------------------------------------
              Region                 Carbon monoxide        Nitrogen oxides            Hydrocarbons              Particulates              Comments
--------------------------------------------------------------------------------------------------------------------------------------------------------
Austria..........................  2.1...............  0.62....................  0.25....................  0.124...................  3.5t;
                                                                                                                                      since 1991; from
                                                                                                                                      1995, adoption of
                                                                                                                                      European Union
                                                                                                                                      standards planned.

[[Page 58143]]

Canada...........................  2.1...............  0.62....................  0.25....................  0.12....................  Since 1987.
European Union...................  2.72..............  0.97 (with hydrocarbons)  ........................  0.14....................  Since 1992.
                                   1.0...............  0.7.....................  ........................  0.08....................  From 1996.
Finland..........................  ..................  ........................  ........................  ........................  Since 1993.
Japan............................  2.1...............  0.7.....................  0.62....................  None....................  Since 1986.
                                   2.1...............  0.5.....................  0.4.....................  0.2.....................  Since 1994.
Sweden, Norway...................  2.1...............  0.62 (city).............  0.25....................  0.124...................  3.5t;
                                                                                                                                      from motor year
                                                                                                                                      1992.
                                   ..................  0.76 (highway)..........  ........................  ........................  ...................
Switzerland......................  2.1...............  0.62 (city).............  0.25....................  0.124...................  3.5t;
                                                                                                                                      since 1988; from
                                                                                                                                      1995, adoption of
                                                                                                                                      European Union
                                                                                                                                      standard planned.
USA (California).................  2.1-5.2...........  0.2-0.6.................  0.2-0.3 (except methane)  0.05 (up to 31 000 km)..  Depending on
                                                                                                                                      mileage.
US Environmental Protection        2.1-2.6...........  0.6-0.8.................  0.2.....................  0.05-0.12...............  Depending on
 Agency.                                                                                                                              mileage.
--------------------------------------------------------------------------------------------------------------------------------------------------------


      Table II-4.--International Limit Values for Components of Diesel Exhaust Heavy-duty Vehicles (g/kWh)
----------------------------------------------------------------------------------------------------------------
                                        Carbon      Nitrogen      Hydro-
               Region                  monoxide      oxides       carbons    Particulates         Comments
----------------------------------------------------------------------------------------------------------------
Austria............................          4.9          9.0          1.23          0.4   .....................
Canada.............................         15.5          5.0          1.3           0.25  g/bhp-h.
                                            15.5          5.0          1.3           0.1   g/bhp-h; from 1995-
                                                                                            97.
European Union.....................          4.5          8.0          1.1           0.36  Since 1992.
                                             4.0          7.0          1.1           0.15  From 1995-96.
Japan..............................          7.4          5.0          2.9           0.7   Indirect injection
                                                                                            engines.
                                             7.4          6.0          2.9           0.7   Direct injection
                                                                                            engines.
Sweden.............................          4.9          9.0          1.23          0.4   .....................
USA................................         15.5          5.0          1.3           0.07  g/bhp-h; bus.
                                            15.5          4.0          1.3           0.1   g/bhp-h; truck.
                                            15.5          5.0          1.3           0.05  g/bhp-h; bus; from
                                                                                            1998
                                            15.5          4.0          1.3           0.1   g/bhp-h; truck; from
                                                                                            1998.
----------------------------------------------------------------------------------------------------------------
Adapted from Mercedes-Benz AG (1994b).

    With respect to the protection of human health, the monograph 
states that the data reviewed supports the conclusion that inhalation 
of diesel exhaust is of concern with respect to both neoplastic and 
non-neoplastic diseases. The monograph found that diesel exhaust ``is 
probably carcinogenic to humans.'' It also states that the particulate 
phase appears to have the greatest effect on health, and both the 
particle core and the associated organic materials have biological 
activity, although the gas-phase components cannot be disregarded. The 
monograph recommends the following actions for the protection of human 
health:
    (1) Diesel exhaust emissions should be controlled as part of the 
overall control of atmospheric pollution, particularly in urban 
environments.
    (2) Emissions should be controlled strictly by regulatory 
inspections and prompt remedial actions.
    (3) Urgent efforts should be made to reduce emissions, specifically 
of particulates, by changing exhaust train techniques, engine design, 
and fuel consumption.
    (4) In the occupational environment, good work practices should be 
encouraged, and adequate ventilation must be provided to prevent 
excessive exposure.
The monograph made no recommendations as to what constitutes excessive 
exposure.

International Agency for Research on Cancer (IARC)

    The carcinogenic risks for human beings were evaluated by a working 
group convened by the International Agency for Research on Cancer in 
1988 (International Agency for Research on Cancer, 1989b). The 
conclusions were:
    (1) There is sufficient evidence for the carcinogenicity in 
experimental animals of the whole diesel engine exhaust.
    (2) There is inadequate evidence for the carcinogenicity in animals 
of gas-phase diesel engine exhaust (with particles removed).
    (3) There is sufficient evidence for the carcinogenicity in 
experimental animals of extracts of diesel engine exhaust particles.
    (4) There is limited evidence for the carcinogenicity in humans of 
engine exhausts (unspecified as from diesel or gasoline engines).

Overall IARC Evaluation

    Diesel engine exhaust is probably carcinogenic to humans (Group 
2A).
(9) MSHA's Initiative To Limit Miner Exposure to Diesel Particulate--a 
Brief History of This Rulemaking and Related Actions
    As discussed in part III of this preamble, by the early 1980's, the 
evidence indicating that exposure to diesel exhaust might be harmful to 
miners, particularly in underground mines, had started to grow. As a 
result, formal agency actions were initiated to investigate this 
possibility and to determine what, if any, actions might be 
appropriate. These actions are

[[Page 58144]]

summarized here in chronological sequence, without comment as to the 
basis of any action or conclusion.
    In 1984, in accordance with the Sec. 102(b) of the Mine Act, NIOSH 
established a standing Mine Health Research Advisory Committee to 
advise it on matters involving or related to mine health research. In 
turn, that group established a subgroup to determine if:

    * * * there is a scientific basis for developing a 
recommendation on the use of diesel equipment in underground mining 
operations and defining the limits of current knowledge, and 
recommending areas of research for NIOSH, if any, taking into 
account other investigators' ongoing and planned research. (49 FR 
37174).

    In 1985, MSHA established an Interagency Task Group with the 
National Institute for Occupational Safety and Health (NIOSH) and the 
former Bureau of Mines (BOM) to assess the health and safety 
implications of the use of diesel-powered equipment in underground coal 
mines. In part, as a result of the recommendation of the Task Group, 
MSHA, in April 1986, began drafting proposed regulations on the 
approval and use of diesel-powered equipment in underground coal mines. 
Also in 1986, the subgroup of the NIOSH advisory committee studying 
this issue summarized the evidence available at that time as follows:

    It is our opinion that although there are some data suggesting a 
small excess risk of adverse health effects associated with exposure 
to diesel exhaust, these data are not compelling enough to exclude 
diesels from underground mines. In cases where diesel equipment is 
used in mines, controls should be employed to minimize exposure to 
diesel exhaust. (Interagency Task Group Report, 1986).

    As noted previously in Section 7 of this part, in discussing MSHA's 
diesel equipment rule, on October 6, 1987, pursuant to Section 102(c) 
of the Mine Act, 30 U.S.C. 812(c), MSHA appointed an advisory committee 
``to provide advice on the complex issues concerning the use of diesel-
powered equipment in underground coal mines.'' (52 FR 37381). MSHA 
appointed nine members to the Advisory Committee. As required by 
Section 101(a)(1), MSHA provided the Advisory Committee with draft 
regulations on the approval and use of diesel-powered equipment in 
underground coal mines. The draft regulations did not include standards 
setting specific limitations on diesel particulate, nor had MSHA at 
that time determined that such standards should be promulgated.
    In July 1988, the Advisory Committee completed its work with the 
issuance of a report entitled ``Report of the Mine Safety and Health 
Administration Advisory Committee on Standards and Regulations for 
Diesel-Powered Equipment in Underground Coal Mines.'' The Advisory 
Committee recommended that MSHA promulgate standards governing the 
approval and use of diesel-powered equipment in underground coal mines. 
The Advisory Committee recommended that MSHA promulgate standards 
limiting underground coal miners' exposure to diesel exhaust.
    With respect to diesel particulate, the Advisory Committee 
recommended that MSHA ``set in motion a mechanism whereby a diesel 
particulate standard can be set.'' (MSHA, 1988). In this regard, the 
Advisory Committee determined that because of inadequacies in the data 
on the health effects of diesel particulate matter and inadequacies in 
the technology for monitoring the amount of diesel particulate matter 
at that time, it could not recommend that MSHA promulgate a standard 
specifically limiting the level of diesel particulate matter. (Id. 64-
65). Instead, the Advisory Committee recommended that MSHA request 
NIOSH and the former BOM to prioritize research in the development of 
sampling methods and devices for diesel particulate. The Advisory 
Committee also recommended that MSHA request a study on the chronic and 
acute effects of diesel emissions (Id). In addition, the Advisory 
Committee recommended that the control of diesel particulate ``be 
accomplished through a combination of measures including fuel 
requirements, equipment design, and in-mine controls such as the 
ventilation system and equipment maintenance in conjunction with 
undiluted exhaust measurements.'' The Advisory Committee further 
recommended that particulate emissions ``be evaluated in the equipment 
approval process and a particulate emission index reported.'' (Id. at 
9).
    In addition, the Advisory Committee recommended that ``the total 
respirable particulate, including diesel particulate, should not exceed 
the existing two milligrams per cubic meter respirable dust standard.'' 
(Id. at 9). Section 202(b)(2) of the Mine Act requires that coal mine 
operators maintain the average concentration of respirable dust at 
their mines at or below two milligrams per cubic meter which 
effectively prohibits diesel particulate matter in excess of two 
milligrams per cubic meter, 30 U.S.C. 842(b)(2).
    Also in 1988, NIOSH issued a Current Intelligence Bulletin 
recommending that whole diesel exhaust be regarded as a potential 
carcinogen and controlled to the lowest feasible exposure level (NIOSH, 
1988). In its bulletin, NIOSH concluded that although the excess risk 
of cancer in diesel exhaust exposed workers has not been quantitatively 
estimated, it is logical to assume that reductions in exposure to 
diesel exhaust in the workplace would reduce the excess risk. NIOSH 
stated that ``[g]iven what we currently know there is an urgent need 
for efforts to be made to reduce occupational exposures to DEP [dpm] in 
mines.''
    Consistent with the Advisory Committee's research recommendations, 
MSHA, in September 1988, formally requested NIOSH to perform a risk 
assessment for exposure to diesel particulate (57 FR 500). MSHA also 
requested assistance from NIOSH and the former BOM in developing 
sampling and analytical methodologies for assessing exposure to diesel 
particulate in mining operations. (Id.). In part, as a result of the 
Advisory Committee's recommendation, MSHA also participated in studies 
on diesel particulate sampling methodologies and determination of 
underground occupational exposure to diesel particulate. A list of the 
studies requested and reports thereof is set forth in 57 FR 500-501.
    On October 4, 1989, MSHA published a Notice of Proposed Rulemaking 
on approval requirements, exposure monitoring, and safety requirements 
for the use of diesel-powered equipment in underground coal mines (54 
FR 40950). The proposed rule, among other things, addressed, and in 
fact followed, the Advisory Committee's recommendation that MSHA 
promulgate regulations requiring the approval of diesel engines (54 FR 
40951); limiting gaseous pollutants from diesel equipment, (Id.); 
establishing ventilation requirements based on approval plate dilution 
air quantities (54 FR 40990); requiring equipment maintenance (54 FR 
40958); requiring that trained personnel work on diesel-powered 
equipment; (54 FR 40995), establishing fuel requirements, (Id.); 
establishing gaseous contaminant monitoring (54 FR 40989); and 
requiring that a particulate index indicating the quantity of air 
needed to dilute particulate emissions from diesel engines be 
established (54 FR 40953).
    On January 6, 1992, MSHA published an Advance Notice of Proposed 
Rulemaking (ANPRM) indicating that it was in the early stages of 
developing a rule specifically addressing miners' exposure to diesel 
particulate (57 FR 500). In the ANPRM, MSHA, among other things, sought 
comment on specific reports on diesel particulate prepared by NIOSH and 
the former BOM. (Id.). MSHA also sought comment

[[Page 58145]]

on reports on diesel particulate which were prepared by or in 
conjunction with MSHA (57 FR 501). The ANPRM also sought comments on 
the health effects, technological and economic feasibility, and 
provisions which should be considered for inclusion in a diesel 
particulate rule (57 FR 501). The notice also identified five specific 
areas where the agency was particularly interested in comments, and 
about which it asked a number of detailed questions: (1) exposure 
limits, including the basis therefore; (2) the validity of the NIOSH 
risk assessment model and the validity of various types of studies; (3) 
information about non-cancer risks, non-lung routes of entry, and the 
confounding effects of tobacco smoking; (4) the availability, accuracy 
and proper use of sampling and monitoring methods for diesel 
particulate; and (5) the technological and economic feasibility of 
various types of controls, including ventilation, diesel fuel, engine 
design, aftertreatment devices, and maintenance by mechanics with 
specialized training. The notice also solicited specific information 
from the mining community on ``the need for a medical surveillance or 
screening program and on the use of respiratory equipment.'' (57 FR 
500). The comment period on the ANPRM closed on July 10, 1992.
    While MSHA was completing a ``comprehensive analysis of the 
comments and any other information received'' in response to the ANPRM 
(57 FR 501), it took several actions to encourage the mining community 
to begin to deal with this problem, and to provide the knowledge and 
equipment needed for this task. As described earlier in this part, the 
Agency held several workshops in 1995, published a ``Toolbox'' of 
controls, and developed a spreadsheet template that allows mine 
operators to compare the impacts of various controls on dpm 
concentrations in individual mines.
    On October 25, 1996, MSHA published a final rule addressing 
approval, exhaust monitoring, and safety requirements for the use of 
diesel-powered equipment in underground coal mines (61 FR 55412). The 
final rule addresses and in large part is consistent with the specific 
recommendations made by the Advisory Committee for limiting underground 
coal miners' exposure to diesel exhaust. (A further summary of this 
rule is contained in Section 7 of this part).
    On February 26, 1997, the United Mine Workers of America petitioned 
the U.S. Court of Appeals for the D.C. Circuit to issue a writ of 
mandamus ordering the Secretary of Labor to promulgate a rule on diesel 
particulate. In Re: International Union, United Mine Workers of America 
, D.C. Cir. Ct. Appeals, No. 97-1109. The matter was scheduled for oral 
argument on September 12, 1997. On September 11, 1997, the Court 
granted the parties' joint motion to continue oral argument and hold 
the proceedings in abeyance. The Court directed the parties to file 
status reports or motions to govern future proceedings at 90-day 
intervals. On April 9, 1998, (63 FR 17492), MSHA published a proposed 
rule to limit the exposure of underground coal miners to dpm. On April 
30, 1998, the Secretary filed a Motion To Dismiss based on the issuance 
of the notice of proposed rulemaking to limit the exposure of 
underground coal miners to dpm. On June 26, 1998, the Court dismissed 
the petition for Writ of Mandamus insofar as it sought regulations 
addressing diesel particulate.

III. Risk Assessment

Table of Contents

Introduction

1. Exposures of U.S. Miners
    a. Underground Coal Mines
    b. Underground Metal and Nonmetal Mines
    c. Surface Mines
    d. Comparison of Miner Exposures to Exposures of Other Groups
2. Health Effects Associated with DPM Exposures
    a. Relevancy Considerations
    i. Relevance of Health Effects Observed in Animals
    ii. Relevance of Health Effects that are Reversible
    iii. Relevance of Health Effects Associated with Fine 
Particulate Matter in Ambient Air
    b. Acute Health Effects
    i. Symptoms Reported by Exposed Miners
    ii. Studies Based on Exposures to Diesel Emissions
    iii. Studies Based on Exposures to Particulate Matter in Ambient 
Air
    c. Chronic Health Effects
    i. Studies Based on Exposures to Diesel Emissions
    A. Chronic Effects Other than Cancer
    B. Cancer
    i. Lung Cancer
    ii. Bladder Cancer
    ii. Studies Based on Exposures to Fine Particulate in Ambient 
Air
    d. Mechanisms of Toxicity
    i. Effects Other than Cancer
    ii. Lung Cancer
    A. Genotoxicological Evidence
    B. Evidence from Animal Studies
3. Characterization of Risk
    a. Material Impairments to Miner Health or Functional Capacity
    i. Sensory Irritations and Respiratory Symptoms
    ii. Excess Risk of Death from Cardiovascular, Cardiopulmonary, 
or Respiratory Causes
    iii. Lung Cancer
    b. Significance of the Risk of Material Impairment to Miners
    i. Definition of a Significant Risk
    ii. Evidence of Significant Risk at Current Exposure Levels
    c. Substantial Reduction of Risk by Proposed Rule

Conclusions

    Introduction. MSHA has reviewed the scientific literature to 
evaluate the potential health effects of diesel particulate at 
occupational exposures encountered in the mining industry. Based on its 
review of the currently available information, this part of the 
preamble assesses the risks associated with those exposures. Additional 
material submitted for the record will be considered by MSHA before 
final determinations are made.
    Agencies sometimes place risk assessments in the rulemaking record 
and provide only a summary in the preamble for a proposed rule. MSHA 
has decided that, in this case, it is important to disseminate a 
discussion of risk widely throughout the mining community. Therefore, 
the full assessment is being included as part of the preamble.
    The risk assessment begins with a discussion of dpm exposure levels 
observed in the mining industry. This is followed by a review of 
information available to MSHA on health effects that have been 
associated with diesel particulate exposure. Finally, in the section 
entitled ``Characterization of Risk,'' the Agency considers three 
questions that must be addressed for rulemaking under the Mine Act, and 
relates the available information about risks of dpm exposure at 
current levels to the regulatory requirements.
    A risk assessment must be technical enough to present the evidence 
and describe the main controversies surrounding it. At the same time, 
an overly technical presentation could cause stakeholders to lose sight 
of the main points. MSHA is guided by the first principle the National 
Research Council established for risk characterization: that the 
approach be--

    [a] decision driven activity, directed toward informing choices 
and solving problems*** Oversimplifying the science or skewing the 
results through selectivity can lead to the inappropriate use of 
scientific information in risk management decisions, but providing 
full information, if it does not address key concerns of the 
intended audience, can undermine that audience's trust in the risk 
analysis.

    MSHA intends this risk assessment to further the rulemaking 
process. The purpose of a proposed rulemaking is to notify the 
regulated community of what

[[Page 58146]]

information the agency is evaluating, how the agency believes it should 
evaluate that information, and what tentative conclusions the agency 
has drawn. Comments, supporting data, and guidance from all interested 
members of the public are encouraged. The risk assessment presented 
here is meant to facilitate public comment, thus helping to ensure that 
final rulemaking is based on as complete a record as possible--on both 
the evidence itself and the manner in which it is to be evaluated by 
the Agency. Those who want additional detail are welcome to examine the 
materials cited in this part, copies of which are included in MSHA's 
rulemaking record.
    While this rulemaking covers only the underground metal and 
nonmetal sector, the risk assessment was prepared so as to enable MSHA 
to assess the risks throughout the mining industry. Accordingly, this 
information will be of interest to the entire mining community. With 
the exception of the discussion in Sec. III.3.c quantifying by how much 
the proposed rule may be expected to reduce current risks, this risk 
assessment is substantially the same as that published with MSHA's 
proposed rule to reduce dpm concentrations in underground coal mines 
(63 FR 17521).
    MSHA had this risk assessment independently peer reviewed. The risk 
assessment presented here incorporates revisions made in accordance 
with the reviewers' recommendations. The reviewers stated that:

    * * * principles for identifying evidence and characterizing 
risk are thoughtfully set out. The scope of the document is 
carefully described, addressing potential concerns about the scope 
of coverage. Reference citations are adequate and up to date. The 
document is written in a balanced fashion, addressing uncertainties 
and asking for additional information and comments as appropriate. 
(Samet and Burke, Nov. 1997).

III.1. Exposures of U.S. Miners

    Information about U.S. miner exposures comes from published studies 
and from additional mine inventories conducted by MSHA since 1993.\6\ 
Previously published studies of U.S. miner exposure to dpm are: Watts 
(1989, 1992), Cantrell (1992, 1993), Haney (1992), and Tomb and Haney 
(1995). MSHA has also conducted inventories subsequent to the period 
covered in Tomb and Haney (1995), and the previously unpublished data 
are included here. The period covered on which this section is based, 
is late 1988 through mid 1997.
---------------------------------------------------------------------------

    \6\ MSHA has only limited information about miner exposures in 
other countries. Based on 223 personal and area samples, average 
exposures at 21 Canadian noncoal mines were reported to range from 
170 to 1300 g/m3 (respirable combustible dust), 
with maximum measurements ranging from 1020 to 3100 g/
m3 (Gangel and Dainty, 1993). Among 622 full shift 
measurements collected since 1989 in German underground noncoal 
mines, 91 (15%) exceeded 400 g/m3 (total carbon) 
(Dahmann et al., 1996). As explained in Part II of this preamble, 
400 g/m3 (total carbon) corresponds to 
approximately 500 g/m3 dpm.
---------------------------------------------------------------------------

    MSHA's field studies involved measuring dpm concentrations at a 
total of 48 mines: 25 underground metal and nonmetal (M/NM) mines, 12 
underground coal mines, and 11 surface mining operations (both coal and 
M/NM). At all surface mines and all underground coal mines, dpm 
measurements were made using the size-selective method, based on 
gravimetric determination of the amount of submicrometer dust collected 
with an impactor. With two exceptions, dpm measurements at underground 
M/NM mines were made using the RCD method (with no submicrometer 
impactor). Measurements at the two remaining underground M/NM mines 
were made using the size-selective method, as in coal and surface 
mines. The various methods of measuring dpm are explained in Part II of 
this preamble. Weighing errors inherent in the gravimetric analysis 
required for both size-selective and RCD methods become statistically 
insignificant at the relatively high dpm concentrations observed. Mines 
were selected from sites known to have diesel exposures. They do not 
constitute a random sample of mines, and care was taken in the text not 
to represent results as applying to the industry as a whole.
    Each underground study typically included personal dpm exposure 
measurements for approximately five production workers. Also, area 
samples were collected in return airways of underground mines to 
determine diesel particulate emission rates. Operational information 
such as the amount and type of equipment, airflow rates, fuel, and 
maintenance was also recorded. In general, MSHA's studies focused on 
face production areas of mines, where the highest concentrations of dpm 
could be expected; but, since some miners do not spend their time in 
face areas, studies were performed in other areas as well, to get a 
more complete picture of miner exposure. Because of potential 
interferences from tobacco smoke in underground M/NM mines, samples 
were not collected on or near smokers.
    Table III-1 summarizes key results from MSHA's studies. The higher 
concentrations in underground mines were typically found in the 
haulageways and face areas where numerous pieces of equipment were 
operating, or where insufficient air was available to ventilate the 
operation. In production areas and haulageways of underground mines 
where diesel powered equipment is used, the mean dpm concentration 
observed was 755 g/m3. By contrast, in travelways 
of underground mines where diesel powered equipment is used, the mean 
dpm concentration (based on 107 samples not included in Table III-1) 
was 307 g/m3. In surface mines, the higher 
concentrations were generally associated with truck drivers and front-
end loader operators. The mean dpm concentration observed was less than 
200 g/m3 at all 11 of the surface mines in which 
measurements were made. More information about the dpm concentrations 
observed in each sector is presented in the material that follows.

    Table III-1.--Full Shift Diesel Particulate Matter Concentrations
   Observed in Production Areas and Haulageways of 48 Dieselized U.S.
           Mines. Intake and Return Area Samples are Excluded.
------------------------------------------------------------------------
                                                    Mean       Exposure
                                    Number of     exposure      range
            Mine type                samples    g/  g/
                                                    m 3          m 3
------------------------------------------------------------------------
Surface..........................           45           88       9-380
Underground Coal.................          226          644     0-3,650
Underground Metal and Nonmetal...          331          830    10-5,570
------------------------------------------------------------------------


[[Page 58147]]

III.1.a. Underground Coal Mines

    Approximately 170 out of the 971 existing underground coal mines 
currently utilize diesel powered equipment. Of these 170 mines, fewer 
than 20 currently use diesel equipment for face coal haulage. The 
remaining mines use diesel equipment for transportation, materials 
handling and other support operations. MSHA focused its efforts in 
measuring dpm concentrations in coal mines on mines that use diesel 
powered equipment for face coal haulage. Twelve mines using diesel-
powered face haulage were sampled. Mines with diesel powered face 
haulage were selected because the face is an area with a high 
concentration of vehicles operating at a heavy duty cycle at the 
furthest end of the mine's ventilation system.
    Diesel particulate levels in underground mines depend on: (1) the 
amount, size, and workload of diesel equipment; (2) the rate of 
ventilation; and, (3) the effectiveness of whatever diesel particulate 
control technology may be in place. In the dieselized mines studied by 
MSHA, the sections used either two or three diesel coal haulage 
vehicles. In eastern mines the haulage vehicles were equipped with a 
nominal 100 horsepower engine. In western mines the haulage vehicles 
were equipped with a nominal 150 horsepower engine. Ventilation rates 
ranged from the nameplate requirement, based on the 100-75-50 percent 
rule (Holtz, 1960), to ten times the nameplate requirement. In most 
cases, the section airflow was approximately twice the name plate 
requirement. Control technology involved aftertreatment filters and 
fuel. Two types of aftertreatment filters were used. These filters 
included a disposable diesel emission filter (DDEF) and a Wire Mesh 
Filter (WMF). The DDEF is a commercially available product; the WMF was 
developed by and only used at one mine. Both low sulfur and high sulfur 
fuels were used.
    Figure III-1 displays the range of exposure measurements obtained 
by MSHA in the field studies it conducted in underground coal mines. A 
study normally consisted of collecting samples on the continuous miner 
operator and ramcar operators for two to three shifts, along with area 
samples in the haulageways. A total of 142 personal samples and 84 area 
samples were collected. No statistically significant difference was 
observed in mean dpm concentration between the personal and area 
samples.
[GRAPHIC] [TIFF OMITTED] TP29OC98.024



[[Page 58148]]


    In six mines, measurements were taken both with and without 
employment of disposable after treatment filters, so that a total of 
eighteen studies, carried out in twelve mines, are displayed.
    Without employment of after treatment filters, average observed dpm 
concentrations exceeded 500 g/m3 in eight of the 
twelve mines and exceeded 1000 g/m3 in four. \7\
---------------------------------------------------------------------------

    \7\ In coal mine E, the average as expressed by the mean 
exceeded 1000 g/m3, but the median did not.
---------------------------------------------------------------------------

    The highest dpm concentrations observed at coal mines were 
collected at Mine ``G.'' Eight of these samples were collected during 
employment of DDEF's, and eight were collected while filters were not 
being employed. Without filters, the mean dpm concentration observed at 
Mine ``G'' was 2052 g/m3 (median = 2100 g/
m3). With disposable filters, the mean dropped to 1241 
g/m3 (median = 1235 g/m3).
    Filters were employed in three of the four studies showing median 
dpm concentration at or below 200 g/m3. After 
adjusting for outby sources of dpm, exposures were found to be reduced 
by up to 95 percent in mines using the DDEF and by up to 50 percent in 
the mine using the WMF.
    The higher dpm concentrations observed at the mine using the WMF 
are attributable partly to the lower section airflow. The only study 
without filters showing a median concentration at or below 200 
g/m3 was conducted in a mine (Mine ``A'') which had 
section airflow approximately ten times the nameplate requirement. The 
section airflow at the mine using the WMF was approximately the 
nameplate requirement.

III.1.b. Underground Metal and Nonmetal Mines

    Currently there are approximately 260 underground M/NM mines in the 
United States. Nearly all of these mines utilize diesel powered 
equipment, and twenty-five of those doing so were sampled by MSHA for 
dpm.\8\ The M/NM studies typically included measurements of dpm 
exposure for dieselized production equipment operators (such as truck 
drivers, roof bolters, haulage vehicles) on two to three shifts. A 
number of area samples were also collected. None of the M/NM mines 
studied were using diesel particulate afterfilters.
---------------------------------------------------------------------------

    \8\ MSHA will provide copies of these studies upon request.
---------------------------------------------------------------------------

    Figure III-2 displays the range of dpm concentrations measured by 
MSHA in the twenty-five underground M/NM mines studied. A total of 254 
personal samples and 77 area samples were collected. No statistically 
significant difference was observed in mean dpm concentration between 
the personal and area samples. Personal exposures observed ranged from 
less than 100 g/m3 to more than 3500 g/
m3. With the exception of Mine ``V'', personal exposures 
were for face workers. Mine ``V'' did not use dieselized face 
equipment.
    Average observed dpm concentrations exceeded 500 g/
m3 in 17 of the 25 M/NM mines and exceeded 1000 g/
m3 in 12.\9\ The highest dpm concentrations observed at M/NM 
mines were collected at Mine ``E''. Based on 16 samples, the mean dpm 
concentration observed at Mine ``E'' was 2008 g/m3 
(median = 1835 g/m3). Twenty-five percent of the 
dpm measurements at this mine exceeded 2400 g/m3. 
All four of these were based on personal samples.
---------------------------------------------------------------------------

    \9\ At M/NM mines C, I, J, and P, the average as expressed by 
the mean exceeded 1000 g/m3 but the median did 
not. At M/NM mines H and S, the median exceeded 1000 g/
m3 but the mean did not. At M/NM mine K, the mean 
exceeded 500 g/m3, but the median did not.

[[Page 58149]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.025



    As with underground coal mines, dpm levels in underground M/NM 
mines are related to the amount and size of equipment, to the 
ventilation rate, and to the effectiveness of the diesel particulate 
control technology employed. In the dieselized M/NM mines studied by 
MSHA, front-end-loaders were used either to load ore onto trucks or to 
haul and load ore onto belts. Additional pieces of diesel powered 
support equipment, such as bolters and mantrips, were also used at the 
mines. The typical piece of production equipment was rated at 150 to 
350 horsepower.
    Ventilation rates in the M/NM mines studied mostly ranged from 100 
to 200 cfm per horsepower of equipment. In only a few of the mines 
inventoried did ventilation exceed 200 cfm/hp. For single-level mines, 
working areas were ventilated in series, i.e., the exhaust air from one 
area became the intake for the next working area. For multi-level 
mines, each level typically had a separate fresh air supply. One or two 
working areas could be on a level. Control technology used to reduce 
diesel particulate emissions in mines inventoried included oxidation 
catalytic converters and engine maintenance programs. Both low sulfur 
and high sulfur fuel were used; some mines used aviation grade low 
sulfur fuel.

III.1.c. Surface Mines

    Currently, there are approximately 12,200 surface mining operations 
in the United States. The total consists of approximately 1,700 coal 
mines and 10,500 M/NM mines. Virtually all of these mines utilize 
diesel powered equipment.
    MSHA conducted diesel particulate studies at eleven surface mining 
operations: eight coal mines and three M/NM mines. To help select those 
surface facilities likely to have significant dpm concentrations, MSHA 
first made a visual examination (based on blackness of the filter) of 
surface mine respirable dust samples collected during a November 1994 
study of surface coal mines. This preliminary screening of samples 
indicated that higher exposures to diesel particulate are typically 
associated with front-end-loader operators and haulage-truck operators; 
accordingly, sampling focused on these operations. A total of 45 
samples were collected.
    Figure III-3 displays the range of dpm concentrations measured at 
the eleven surface mines. The average dpm concentration observed was 
less than 200 g/m\3\ at all mines sampled. The maximum dpm 
concentration observed was less than or equal to 200 g/m\3\ in 
8 of the 11 mines (73%). The surface mine studies indicate that even 
when sampling is performed at the areas of surface mines believed most 
likely to have high exposures, dpm concentrations are generally less 
than 200 g/m\3\.

[[Page 58150]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.026



III.1.d. Comparison of Miner Exposures to Exposures of Other Groups

    Occupational exposure to diesel particulate primarily originates 
from industrial operations employing equipment powered with diesel 
engines. Diesel engines are used to power ships, locomotives, heavy 
duty trucks, heavy machinery, as well as a small number of light-duty 
passenger cars and trucks. NIOSH estimates that approximately 1.35 
million workers are occupationally exposed to the combustion products 
of diesel fuel in approximately 80,000 workplaces in the United States. 
Workers who are likely to be exposed to diesel emissions include: mine 
workers; bridge and tunnel workers; railroad workers; loading dock 
workers; truck drivers; fork-lift drivers; farm workers; and, auto, 
truck, and bus maintenance garage workers (NIOSH, 1988). Besides 
miners, groups for which occupational exposures have been reported and 
health effects have been studied include dock workers, truck drivers, 
and railroad workers.
    As estimated by the geometric mean, median occupational exposures 
reported for dock workers either operating or otherwise exposed to 
diesel fork lift trucks have ranged from 23 to 55 g/m\3\, as 
measured by submicrometer elemental carbon (NIOSH, 1990; Zaebst et al., 
1991). Watts (1995) states that ``elemental carbon generally accounts 
for about 40% to 60% of diesel particulate mass.'' Assuming that, on 
average, the submicrometer elemental carbon constituted approximately 
50% by mass of the whole diesel particulate, this would correspond to a 
range of 46 to 110 g/m\3\ in median dpm concentrations at 
various docks.
    In a study of dpm exposures in the trucking industry, Zaebst et al. 
(1991) reported geometric mean concentrations of submicrometer carbon 
ranging from 2 to 7 g/m\3\ for drivers to 5 to 28 g/
m\3\ for mechanics, depending on weather conditions. Again assuming 
that, on average, the mass concentration of whole diesel particulate is 
about twice that of submicrometer elemental carbon, the corresponding 
range of median dpm concentrations would be 4 to 56 g/m\3\.
    Exposures of railroad workers to dpm were estimated by Woskie et 
al. (1988) and Schenker et al. (1990). As measured by total respirable 
particulate matter other than cigarette smoke, Woskie et al. reported 
geometric mean concentrations for various occupational categories of 
exposed railroad workers ranging from 49 to 191 g/m\3\.
    Figure III-4 shows the range of median dpm concentrations observed 
for mine workers at different mines compared to the range of median 
concentrations estimated for dock workers (including forklift drivers 
at loading docks), truck drivers and mechanics, railroad workers, and 
urban ambient air.\10\ The range for ambient air, 1 to 10 g/
m\3\, was obtained from Cass and Gray (1995). For dock workers, truck 
drivers, and railroad workers, the estimated range of median exposures 
is respectively 46 to 110 g/m\3\, 4 to 56 g/m\3\, and 
49 to 191 g/m\3\. The range of medians observed at different 
underground coal mines is 55 to 2100 g/m\3\, with filters 
employed at mines showing the lower concentrations. For underground M/
NM mines, the corresponding range is 68 to 1835

[[Page 58151]]

g/m\3\, and for surface mines it is 19 to 160 g/m\3\.
---------------------------------------------------------------------------

    \10\ In the studies reviewed, investigators have used various 
statistical parameters, such as mean, median, or geometric mean, to 
summarize the dpm concentrations observed. Since the raw data are 
not available, MSHA was not able to summarize the data in exactly 
the same way for each category depicted in Figure III-4.
[GRAPHIC] [TIFF OMITTED] TP29OC98.027


    As shown in Figure III-4, some miners are exposed to far higher 
concentrations of dpm than are any other populations for higher 
concerntrations of dpm than are any other populations for which data 
have been collected. Indeed, median dpm concentrations observed in some 
underground mines are up to 200 times as high as average environmental 
exposures in the most heavily polluted urban areas, and up to 10 times 
as high as median exposures estimated for the most heavily exposed 
workers in other occupational groups.

III.2. Health Effects Associated With DPM Exposures

    This section reviews all the various health effects (of which MSHA 
is aware) that may be associated with exposure to diesel particulate. 
The review is divided into three main sections: acute effects, such as 
diminished pulmonary function and eye irritation; chronic effects, such 
as lung cancer; and mechanisms of toxicity. Prior to that review, 
however, the relevance of certain types of information will be 
considered. This discussion will address the relevance of health 
effects observed in animals, health effects that are reversible, and 
health effects associated with fine particulate matter in the ambient 
air.

III.2.a. Relevancy Considerations

III.2.a.i. Relevance of Health Effects Observed in Animals

    Since the lungs of different species may react differently to 
particle inhalation, it is necessary to treat the results of animal 
studies with some caution. Evidence from animal studies can 
nevertheless be valuable, and those respondents to MSHA's ANPRM who 
addressed this question urged consideration of all animal studies 
related to the health effects of diesel exhaust.
    Unlike humans, laboratory animals are bred to be homogeneous and 
can be randomly selected for either non-exposure or exposure to varying 
levels of a potentially toxic agent. This permits setting up 
experimental and control groups of animals that do not differ 
biologically prior to exposure. The consequences of exposure can then 
be determined by comparing responses in the experimental and control 
groups. After a prescribed duration of deliberate exposure, laboratory 
animals can also be sacrificed, dissected, and examined. This can 
contribute to an understanding of mechanisms by which inhaled

[[Page 58152]]

particles may exert their effects on health. For this reason, 
discussion of the animal evidence is placed in the section entitled 
``Mechanisms of Toxicity'' below.
    Animal evidence also can help isolate the cause of adverse health 
effects observed among humans exposed to a variety of potentially 
hazardous substances. If, for example, the epidemiological data are 
unable to distinguish between several possible causes of increased risk 
of disease in a certain population, then controlled animal studies may 
provide evidence useful in suggesting the most likely explanation--and 
provide that information years in advance of definitive evidence from 
human observations.
    Furthermore, results from animal studies may also serve as a check 
on the credibility of observations from epidemiological studies of 
human populations. If a particular health effect is observed in animals 
under controlled laboratory conditions, this tends to corroborate 
observations of similar effects in humans.
    Accordingly, MSHA believes that judicious use of evidence from 
animal studies is appropriate. The extent to which MSHA relies upon 
such evidence to draw specific conclusions will be discussed below in 
connection with those conclusions.

III.2.a.ii. Relevance of Health Effects That are Reversible

    Some reported health effects associated with dpm are apparently 
reversible--i.e., if the worker is moved away from the source for a few 
days, the health problem goes away. A good example is eye irritation.
    In response to the ANPRM, questions were raised as to whether so-
called ``reversible'' effects can constitute a ``material'' impairment. 
For example, one commenter argued that ``it is totally inappropriate 
for the agency to set permissible exposure limits based on temporary, 
reversible sensory irritation'' because such effects cannot be a 
``material'' impairment of health or functional capacity within the 
definition of the Mine Act (American Mining Congress, 87-0-21, 
Executive Summary, p. 1, and Appendix A).
    MSHA does not agree with this categorical view. Although the 
legislative history of the Mine Act is silent concerning the meaning of 
the term ``material impairment of health or functional capacity,'' and 
the issue has not been litigated within the context of the Mine Act, 
the statutory language about risk in the Mine Act is similar to that 
under the OSH Act. A similar argument was dispositively resolved in 
favor of the Occupational Safety and Health Administration (OSHA) by 
the 11th Circuit Court of Appeals in AFL-CIO v. OSHA, 965 F.2d 962, 974 
(1992) (popularly known as the ``PEL's'' decision).
    In that case, OSHA proposed new limits on 428 diverse substances. 
It grouped these into 18 categories based upon the primary health 
effects of those substances: e.g., neuropathic effects, sensory 
irritation, and cancer. (54 FR 2402). Challenges to this rule included 
the assertion that a ``sensory irritation'' was not a ``material 
impairment of health or functional capacity'' which could be regulated 
under the OSH Act. Industry petitioners argued that since irritant 
effects are transient in nature, they did not constitute a ``material 
impairment.'' The Court of Appeals decisively rejected this argument.
    The court noted OSHA's position that effects such as stinging, 
itching and burning of the eyes, tearing, wheezing, and other types of 
sensory irritation can cause severe discomfort and be seriously 
disabling in some cases. Moreover, there was evidence that workers 
exposed to these sensory irritants could be distracted as a result of 
their symptoms, thereby endangering other workers and increasing the 
risk of accidents. (Id. at 974). This evidence included information 
from NIOSH about the general consequences of sensory irritants on job 
performance, as well as testimony by commenters on the proposed rule 
supporting the view that such health effects should be regarded as 
material health impairments. While acknowledging that ``irritation'' 
covers a spectrum of effects, some of which can be trivial, OSHA had 
concluded that the health effects associated with exposure to these 
substances warranted action--to ensure timely medical treatment, reduce 
the risks from increased absorption, and avoid a decreased resistance 
to infection (Id at 975). Finding OSHA's evaluation adequate, the Court 
of Appeals rejected petitioners' argument and stated the following:

    We interpret this explanation as indicating that OSHA finds that 
although minor irritation may not be a material impairment, there is 
a level at which such irritation becomes so severe that employee 
health and job performance are seriously threatened, even though 
those effects may be transitory. We find this explanation adequate. 
OSHA is not required to state with scientific certainty or precision 
the exact point at which each type of sensory or physical irritation 
becomes a material impairment. Moreover, section 6(b)(5) of the Act 
charges OSHA with addressing all forms of ``material impairment of 
health or functional capacity,'' and not exclusively ``death or 
serious physical harm'' or ``grave danger'' from exposure to toxic 
substances. See 29 U.S.C. 654(a)(1), 655(c). [Id. at 974].

III.2.a.iii. Relevance of Health Effects Associated with Fine 
Particulate Matter in Ambient Air

    There have been many studies in recent years designed to determine 
whether the mix of particulate matter in ambient air is harmful to 
health. The evidence linking particulates in air pollution to health 
problems has long been compelling enough to warrant direction from the 
Congress to limit the concentration of such particulates (see part II, 
section 5 of this preamble). In recent years, the evidence of harmful 
effects due to airborne particulates has increased, and, moreover, has 
suggested that ``fine'' particulates (i.e., particles less than 2.5 
m in diameter) are more strongly associated than ``coarse'' 
particulates (i.e., respirable particles greater than 2.5 m in 
diameter) with the adverse health effects observed (EPA, 1996).
    MSHA recognizes that there are two difficulties involved in 
utilizing the evidence from such studies in assessing risks to miners 
from occupational dpm exposures. First, although dpm is a fine 
particulate, ambient air also contains fine particulates other than 
dpm. Therefore, health effects associated with exposures to fine 
particulate matter in air pollution studies are not associated 
specifically with exposures to dpm or any other one kind of fine 
particulate matter. Second, observations of adverse health effects in 
segments of the general population do not necessarily apply to the 
population of miners. Since, due to age and selection factors, the 
health of miners differs from that of the public as a whole, it is 
possible that fine particles might not affect miners, as a group, to 
the same extent as the general population.
    Nevertheless, there are compelling reasons to consider this body of 
evidence. Since dpm is a type of respirable particle, information about 
health effects associated with exposures to respirable particles in 
general, and especially to fine particulate matter, is certainly 
relevant, even if difficult to apply directly to dpm exposures. Adverse 
health effects in the general population have been observed at ambient 
atmospheric particulate concentrations well below those studied in 
occupational settings. Furthermore, there is extensive literature 
showing that occupational dust exposures contribute to Chronic 
Obstructive Pulmonary Diseases (COPD), thereby compromising the 
pulmonary reserve of

[[Page 58153]]

some miners, and that miners experience COPD at a significantly higher 
rate than the general population (Becklake 1989, 1992; Oxman 1993; 
NIOSH 1995). This would appear to place affected miners in a 
subpopulation specifically identified as susceptible to the adverse 
health effects of respirable particle pollution (EPA, 1996). The Mine 
Act requires that standards ``* * * most adequately assure on the basis 
of the best available evidence that no miner suffer material impairment 
of health or functional capacity * * *'' (Section 101(a)(6), emphasis 
added).
    In sum, MSHA believes it would be a serious omission to ignore the 
body of evidence from air pollution studies and the Agency is, 
therefore, taking that evidence into account. The Agency would, 
however, welcome additional scientific information and analysis on ways 
of applying this body of evidence to miners experiencing acute and/or 
chronic dpm exposures. MSHA is especially interested in receiving 
information on whether the elevated prevalence of COPD among miners 
makes them, as a group, highly susceptible to the harmful effects of 
fine particulate air pollution, including dpm.

III.2.b. Acute Health Effects

    Information relating to the acute health effects of dpm includes 
anecdotal reports of symptoms experienced by exposed miners, studies 
based on exposures to diesel emissions, and studies based on exposures 
to particulate matter in the ambient air. These will be discussed in 
turn.

III.2.b.i. Symptoms Reported by Exposed Miners

    Miners working in mines with diesel equipment have long reported 
adverse effects after exposure to diesel exhaust. For example, at the 
workshops on dpm conducted in 1995, a miner reported headaches and 
nausea among several operators after short periods of exposure (dpm 
Workshop; Mt. Vernon, IL, 1995). Another miner reported that the smoke 
from equipment using improper fuel or not well maintained is an 
irritant to nose and throat and impairs vision. ``We've had people sick 
time and time again * * * at times we've had to use oxygen for people 
to get them to come back around to where they can feel normal again.'' 
(dpm Workshop; Beckley, WV, 1995). Other miners (dpm Workshops; 
Beckley, WV, 1995; Salt Lake City, UT, 1995), reported similar symptoms 
in the various mines where they worked.
    Kahn et al. (1988) conducted a study of the prevalence and 
seriousness of such complaints, based on United Mine Workers of America 
records and subsequent interviews with the miners involved. The review 
involved reports at five underground coal mines in Utah and Colorado 
between 1974 and 1985. Of the 13 miners reporting symptoms: 12 reported 
mucous membrane irritation, headache and light-headiness; eight 
reported nausea; four reported heartburn; three reported vomiting and 
weakness, numbness, and tingling in extremities; two reported chest 
tightness; and two reported wheezing (although one of these complained 
of recurrent wheezing without exposure). All of these incidents were 
severe enough to result in lost work time due to the symptoms (which 
subsided within 24 to 48 hours).
    MSHA welcomes additional information about such effects including 
information from medical personnel who have treated miners and 
information on work time lost, together with information about the 
exposures of miners for whom such effects have been observed. The 
Agency would be especially interested in comparisons of effects 
observed in workers subjected to filtered exhaust as compared to those 
subjected to unfiltered exhaust.

III.2.b.ii. Studies Based on Exposures to Diesel Emissions

    Several scientific studies have been conducted to investigate acute 
effects of exposure to diesel emissions.
    In a clinical study (Battigelli, 1965), volunteers were exposed to 
different levels of diesel exhaust and then the degree of eye 
irritation was measured. Exposure for ten minutes to diesel exhaust 
produced ``intolerable'' irritation in some subjects while the average 
irritation score was midway between ``some'' irritation and a 
``conspicuous but tolerable'' irritation level. Cutting the exposure by 
50% significantly reduced the irritation.
    In a study of underground iron ore miners exposed to diesel 
emissions, Jorgensen and Svensson (1970), found no difference in 
spirometry measurements taken before and after a work shift. Similarly, 
Ames et al. (1982), in a study of coal miners exposed to diesel 
emissions, detected no statistically significant relationship between 
exposure and pulmonary function. However, the authors noted that the 
lack of a positive result might be due to the low concentrations of 
diesel emissions involved.
    Gamble et al. (1978) did observe decreases in pulmonary function 
over a single shift in salt miners exposed to diesel emissions. 
Pulmonary function appeared to deteriorate in relation to the 
concentration of diesel exhaust, as indicated by NO2; but 
this effect was confounded by the presence of NO2 due to the 
use of explosives.
    Gamble et al. (1987a) assessed response to diesel exposure among 
232 bus garage workers by means of a questionnaire and before- and 
after-shift spirometry. No significant relationship was detected 
between diesel exposure and change in pulmonary function. However, 
after adjusting for age and smoking status, a significantly elevated 
prevalence of reported symptoms was found in the high-exposure group. 
The strongest associations with exposure were found for eye irritation, 
labored breathing, chest tightness, and wheeze. The questionnaire was 
also used to compare various acute symptoms reported by the garage 
workers and a similar population of workers at a lead acid battery 
plant who were not exposed to diesel fumes. The prevalence of work-
related eye irritations, headaches, difficult or labored breathing, 
nausea, and wheeze was significantly higher in the diesel bus garage 
workers, but the prevalence of work-related sneezing was significantly 
lower.
    Ulfvarson et al. (1987) studied effects over a single shift on 47 
stevedores exposed to dpm at particle concentrations ranging from 130 
g/m3 to 1000 g/m3. A 
statistically significant loss of pulmonary function was observed, with 
recovery after 3 days of no occupational exposure.
    To investigate whether removal of the particles from diesel exhaust 
might reduce the ``acute irritative effect on the lungs'' observed in 
their earlier study, Ulfvarson and Alexandersson (1990) compared 
pulmonary effects in a group of 24 stevedores exposed to unfiltered 
diesel exhaust to a group of 18 stevedores exposed to filtered exhaust, 
and to a control group of 17 occupationally unexposed workers. Workers 
in all three groups were nonsmokers and had normal spirometry values, 
adjusted for sex, age, and height, prior to the experimental workshift.
    In addition to confirming the earlier observation of significantly 
reduced pulmonary function after a single shift of occupational 
exposure, the study found that the stevedores in the group exposed only 
to filtered exhaust had 50-60% less of a decline in forced vital 
capacity (FVC) than did those stevedores who worked with unfiltered 
equipment. Similar results were observed for a subgroup of six 
stevedores who were exposed to filtered exhaust on one shift and 
unfiltered exhaust on another. No loss of pulmonary function was 
observed for the unexposed control group. The

[[Page 58154]]

authors suggested that these results ``support the idea that the 
irritative effects of diesel exhausts to the lungs [sic] is the result 
of an interaction between particles and gaseous components and not of 
the gaseous components alone.'' They concluded that ``* * * it should 
be a useful practice to filter off particles from diesel exhausts in 
work places even if potentially irritant gases remain in the 
emissions.''
    Rudell et al., (1996) carried out a series of double-blind 
experiments on 12 healthy, non-smoking subjects to investigate whether 
a particle trap on the tailpipe of an idling diesel engine would reduce 
acute effects of diesel exhaust, compared with exposure to unfiltered 
exhaust. Symptoms associated with exposure included headache, 
dizziness, nausea, tiredness, tightness of chest, coughing, and 
difficulty in breathing, but the most prominent were found to be 
irritation of the eyes and nose, and a sensation of unpleasant smell. 
Among the various pulmonary function tests performed, exposure was 
found to result in significant changes only as measured by increased 
airway resistance and specific airway resistance. The ceramic wall flow 
particle trap reduced the number of particles by 46 percent, but 
resulted in no significant attenuation of symptoms or lung function 
effects. The authors concluded that diluted diesel exhaust caused 
increased symptoms of the eyes and nose, unpleasant smell, and 
bronchoconstriction, but that the 46 percent reduction in median 
particle number concentration observed was not sufficient to protect 
against these effects in the populations studied.
    Wade and Newman (1993) documented three cases in which railroad 
workers developed persistent asthma following exposure to diesel 
emissions while riding immediately behind the lead engines of trains 
having no caboose. None of these workers were smokers or had any prior 
history of asthma or other respiratory disease. Although this is the 
only published report MSHA knows of directly relating exposure to 
diesel emissions with the development of asthma, there have been a 
number of recent studies indicating that dpm exposure can induce 
bronchial inflammation and respiratory immunological allergic responses 
in humans. These are reviewed in Peterson and Saxon (1996) and Diaz-
Sanchez (1997).

III.2.b.iii. Studies Based on Exposures to Particulate Matter in 
Ambient Air

    As early as the 1930's, as a result of an incident in Belgium's 
industrial Meuse Valley, it was known that large increases in 
particulate air pollution, created by winter weather inversions, could 
be associated with large simultaneous increases in mortality and 
morbidity. More than 60 persons died from this incident, and several 
hundred suffered respiratory problems. The mortality rate during the 
episode was more than ten times higher than normal, and it was 
estimated that over 3,000 sudden deaths would occur if a similar 
incident occurred in London. Although no measurements of pollutants in 
the ambient air during the episode are available, high PM levels were 
obviously present (EPA, 1996).
    A significant elevation in particulate matter (along with 
SO2 and its oxidation products) was measured during a 1948 
incident in Donora, PA. Of the Donora population, 42.7 percent 
experienced some adverse health effect, mainly due to irritation of the 
respiratory tract. Twelve percent of the population reported difficulty 
in breathing, with a steep rise in frequency as age progressed to 55 
years (Schrenk, 1949).
    Approximately as projected by Firket (1931), an estimated 4,000 
deaths occurred in response to a 1952 episode of extreme air pollution 
in London. The nature of these deaths is unknown, but there is clear 
evidence that bronchial irritation, dyspnea, bronchospasm, and, in some 
cases, cyanosis occurred with unusual prevalence (Martin, 1964).
    These three episodes ``left little doubt about causality in regard 
to the induction of serious health effects by very high concentrations 
of particle-laden air pollutant mixtures'' and stimulated additional 
research to characterize exposure-response relationships (EPA, 1996). 
Based on several analyses of the 1952 London data, along with several 
additional acute exposure mortality analyses of London data covering 
later time periods, the U.S. Environmental Protection Agency (EPA) 
concluded that increased risk of mortality is associated with exposure 
to particulate and SO2 levels in the range of 500-1000 
g/m3. The EPA also concluded that relatively small, 
but statistically significant increases in mortality risk exist at 
particulate levels below 500 g/m3, with no 
indications of any specific threshold level yet indicated at lower 
concentrations (EPA, 1986).
    Subsequently, between 1986 and 1996, increasingly sophisticated 
particulate measurements and statistical techniques have enabled 
investigators to address these questions more quantitatively. The 
studies on acute effects carried out since 1986 are reviewed in the 
1996 EPA Air Quality Criteria for Particulate Matter, which forms the 
basis for the discussion below (EPA, 1996).
    At least 21 studies have been conducted that evaluate associations 
between acute mortality and morbidity effects and various measures of 
fine particulate levels in the ambient air. These studies are 
identified in Tables III-2 and III-3. Table III-2 lists 11 studies that 
measured primarily fine particulate matter using filter-based optical 
techniques and, therefore, provide mainly qualitative support for 
associating observed effects with fine particles. Table III-3 lists 
quantitative results from 10 studies that reported gravimetric 
measurements of either the fine particulate fraction or of components, 
such as sulfates, that serve as indicators.
    A total of 38 studies examining relationships between short-term 
particulate levels and increased mortality, including nine with fine 
particulate measurements, were published between 1988 and 1996 (EPA, 
1996). Most of these found statistically significant positive 
associations. Daily or several-day elevations of particulate 
concentrations, at average levels as low as 18-58 g/
m3, were associated with increased mortality, with stronger 
relationships observed in those with preexisting respiratory and 
cardiovascular disease. Overall, these studies suggest that an increase 
of 50 g/m3 in the 24-hour average of 
PM10 is associated with a 2.5 to 5-percent increase in the 
risk of mortality in the general population. Based on Schwartz et al. 
(1996), the relative risk of mortality in the general population 
increases by about 2.6 to 5.5 percent per 25 g/m3 
of fine particulate (PM2.5) (EPA, 1996).
    A total of 22 studies were published on associations between short-
term particulate levels and hospital admissions, outpatient visits, and 
emergency room visits for respiratory disease, Chronic Obstructive 
Pulmonary Disease (COPD), pneumonia, and heart disease (EPA, 1996). 
Fifteen of these studies were focussed on the elderly. Of the seven 
that dealt with all ages (or in one case, persons less than 65 years 
old), all showed positive results. All of the five studies relating 
fine particulate measurements to increased hospitalization, listed in 
Tables III-2 and III-3, dealt with general age populations and showed 
statistically significant associations. The estimated increase in risk 
ranges from 3 to 16 percent per 25 g/m3 of fine 
particulate. Overall, these studies are indicative of acute morbidity 
effects being related to fine particulate matter and support the 
mortality findings.

[[Page 58155]]

    Most of the 14 published quantitative studies on ambient 
particulate exposures and acute respiratory symptoms were restricted to 
children (EPA, 1996). Although they generally showed positive 
associations, and may be of considerable biological relevance, evidence 
of toxicity in children is not necessarily applicable to adults. The 
few studies on adults have not produced statistically significant 
evidence of a relationship.
    Fourteen studies since 1982 have investigated associations between 
ambient particulate levels and loss of pulmonary function (EPA, 1996). 
In general, these studies suggest a short term effect, especially in 
symptomatic groups such as asthmatics, but most were carried out on 
children only. In a study of adults with mild COPD, Pope and Kanner 
(1993) found a 2910 ml decrease in 1-second Forced 
Expiratory Volume (FEV1) per 50 g/m3 
increase in PM10, which is similar in magnitude to the 
change generally observed in the studies on children. In another study 
of adults, with PM10 ranging from 4 to 137 g/
m3, Dusseldorp et al. (1995) found 45 and 77 ml/sec 
decreases, respectively, for evening and morning Peak Expiratory Flow 
Rate (PEFR) per 50 g/m3 increase in PM10 
(EPA, 1996). In the only study carried out on adults that specifically 
measured fine particulate (PM2.5), Perry et al. (1983) did 
not detect any association of exposure with loss of pulmonary function. 
This study, however, was conducted on only 24 adults (all asthmatics) 
exposed at relatively low concentrations of PM2.5 and, 
therefore, had very little power to detect any such association.

III.2.c. Chronic Health Effects

    During the 1995 dpm workshops, miners reported observable adverse 
health effects among those who have worked a long time in dieselized 
mines. For example, a miner (dpm Workshop; Salt Lake City, UT, 1995), 
stated that miners who work with diesel ``have spit up black stuff 
every night, big black--what they call black (expletive) * * * [they] 
have the congestion every night * * * the 60-year-old man working there 
40 years.'' Scientific investigation of the chronic health effects of 
dpm exposure includes studies based specifically on exposures to diesel 
emissions and studies based more generally on exposures to fine 
particulate matter in the ambient air. Only the evidence from human 
studies will be addressed in this section. Data from genotoxicology 
studies and studies on laboratory animals will be discussed later, in 
the section on potential mechanisms of toxicity.

III.2.c.i. Studies Based on Exposures to Diesel Emissions

    The discussion will summarize the epidemiological literature on 
chronic effects other than cancer, and then concentrate on the 
epidemiology of cancer in workers exposed to dpm.

III.2.c.i.A. Chronic Effects Other Than Cancer

    There have been a number of epidemiological studies that 
investigated relationships between diesel exposure and the risk of 
developing persistent respiratory symptoms (i.e., chronic cough, 
chronic phlegm, and breathlessness) or measurable loss in lung 
function. Three studies involved coal miners (Reger et al., 1982; Ames 
et al., 1984; Jacobson et al., 1988); four studies involved metal and 
nonmetal miners (Jorgenson & Svensson, 1970; Attfield, 1979; Attfield 
et al., 1982; Gamble et al., 1983). Three studies involved other groups 
of workers--railroad workers (Battigelli et al., 1964), bus garage 
workers (Gamble et al., 1987), and stevedores (Purdham et al., 1987).
    Reger et al. (1982) examined the prevalence of respiratory symptoms 
and the level of pulmonary function among more than 1,600 underground 
and surface coal miners, comparing results for workers (matched for 
smoking status, age, height, and years worked underground) at diesel 
and non-diesel mines. Those working at underground dieselized mines 
showed some increased respiratory symptoms and reduced lung function, 
but a similar pattern was found in surface miners who presumably would 
have experienced less diesel exposure. Miners in the dieselized mines, 
however, had worked underground for less than 5 years on average.
    In a study of 1,118 coal miners, Ames et al. (1984) did not detect 
any pattern of chronic respiratory effects associated with exposure to 
diesel emissions. The analysis, however, took no account of baseline 
differences in lung function or symptom prevalence, and the authors 
noted a low level of exposure to diesel-exhaust contaminants in the 
exposed population.
    In a cohort of 19,901 coal miners investigated over a 5-year 
period, Jacobsen et al. (1988) found increased work absence due to 
self-reported chest illness in underground workers exposed to diesel 
exhaust, as compared to surface workers, but found no correlation with 
their estimated level of exposure.
    Jorgenson & Svensson (1970) found higher rates of chronic 
productive bronchitis, for both smokers and nonsmokers, among 
underground iron ore miners exposed to diesel exhaust as compared to 
surface workers at the same mine. No significant difference was found 
in spirometry results.
    Using questionnaires collected from 4,924 miners at 21 metal and 
nonmetal mines, Attfield (1979) evaluated the effects of exposure to 
silica dust and diesel exhaust and obtained inconclusive results with 
respect to diesel exposure. For both smokers and non-smokers, miners 
occupationally exposed to diesel for five or more years showed an 
elevated prevalence of persistent cough, persistent phlegm, and 
shortness of breath, as compared to miners exposed for less than five 
years, but the differences were not statistically significant. Four 
quantitative indicators of diesel use failed to show consistent trends 
with symptoms and lung function.
    Attfield et al. (1982) reported on a medical surveillance study of 
630 white male miners at 6 potash mines. No relationships were found 
between measures of diesel use or exposure and various health indices, 
based on self-reported respiratory symptoms, chest radiographs, and 
spirometry.
    In a study of salt miners, Gamble and Jones (1983) observed some 
elevation in cough, phlegm, and dyspnea associated with mines ranked 
according to level of diesel exhaust exposure. No association between 
respiratory symptoms and estimated cumulative diesel exposure was found 
after adjusting for differences among mines. However, since the mines 
varied widely with respect to diesel exposure levels, this adjustment 
may have masked a relationship.
    Battigelli et al. (1964) compared pulmonary function and complaints 
of respiratory symptoms in 210 railroad repair shop employees, exposed 
to diesel for an average of 10 years, to a control group of 154 
unexposed railroad workers. Respiratory symptoms were less prevalent in 
the exposed group, and there was no difference in pulmonary function; 
but no adjustment was made for differences in smoking habits.
    In a study of workers at four diesel bus garages in two cities, 
Gamble et al. (1987b) investigated relationships between tenure (as a 
surrogate for cumulative exposure) and respiratory symptoms, chest 
radiographs, and pulmonary function. The study population was also 
compared to an unexposed control group of workers with similar 
socioeconomic background. After indirect adjustment for age, race, and 
smoking, the exposed workers showed an increased prevalence of cough, 
phlegm, and wheezing, but no

[[Page 58156]]

association was found with tenure. Age-and height-adjusted pulmonary 
function was found to decline with duration of exposure, but was 
elevated on average, as compared to the control group. The number of 
positive radiographs was too small to support any conclusions. The 
authors concluded that the exposed workers may have experienced some 
chronic respiratory effects.
    Purdham et al. (1987) compared baseline pulmonary function and 
respiratory symptoms in 17 exposed stevedores to a control group of 11 
port office workers. After adjustment for smoking, there was no 
statistically significant difference in self-reported respiratory 
symptoms between the two groups. However, after adjustment for smoking, 
age, and height, exposed workers showed lower baseline pulmonary 
function, consistent with an obstructive ventilatory defect, as 
compared to both the control group and the general metropolitan 
population.
    In a recent review of these studies, Cohen and Higgins (1995) 
concluded that they did not provide strong or consistent evidence for 
chronic, nonmalignant respiratory effects associated with occupational 
exposure to diesel exhaust. These reviewers stated, however, that 
``several studies are suggestive of such effects * * * particularly 
when viewed in the context of possible biases in study design and 
analysis.'' MSHA agrees that the studies are inconclusive but 
suggestive of possible effects.

III.2.c.i.B. Cancer

    Because diesel exhaust has long been known to contain carcinogenic 
compounds (e.g., benzene in the gaseous fraction and benzopyrene and 
nitropyrene in the dpm fraction), a great deal of research has been 
conducted to determine if occupational exposure to diesel exhaust 
actually results in an increased risk of cancer. Evidence that exposure 
to dpm increases the risk of developing cancer comes from three kinds 
of studies: human studies, genotoxicity studies, and animal studies. 
MSHA places the most weight on evidence from the human epidemiological 
studies and views the genotoxicological and animal studies as lending 
support to the epidemiological evidence.
    In the epidemiological studies, it is generally impossible to 
disassociate exposure to dpm from exposure to the gasses and vapors 
that form the remainder of whole diesel exhaust. However, the animal 
evidence shows no significant increase in the risk of lung cancer from 
exposure to the gaseous fraction alone (Heinrich et al., 1986; Iwai et 
al., 1986; Brightwell et al., 1986). Therefore, dpm, rather than the 
gaseous fraction of diesel exhaust, is assumed be the agent associated 
with an excess risk of lung cancer.

III.2.c.i.B.i. Lung Cancer

    Beginning in 1957, at least 43 epidemiological studies have been 
published examining relationships between diesel exhaust exposure and 
the prevalence of lung cancer. The most recent published reviews of 
these studies are by Mauderly (1992), Cohen and Higgins (1995), Stober 
and Abel (1996), Morgan et al. (1997), and Dawson et al. (1998). In 
addition, in response to the ANPRM, several commenters provided MSHA 
with their own reviews. Two comprehensive statistical ``meta-analyses'' 
of the epidemiological literature are also available: Lipsett and 
Alexeeff (1998) and Bhatia et al. (1998). These meta-analyses, which 
analyze and combine results from the various epidemiological studies, 
both suggest a statistically significant increase of 30 to 40 percent 
in the risk of lung cancer, attributable to occupational dpm exposure. 
The studies themselves, along with MSHA's comments on each study, are 
summarized in Tables III-4 (24 cohort studies) and III-5 (19 case-
control studies).\11\ Presence or absence of an adjustment for smoking 
habits is highlighted, and adjustments for other potentially 
confounding factors are indicated when applicable.
---------------------------------------------------------------------------

    \11\ For simplicity, the epidemiological studies considered here 
are placed into two broad categories. A cohort study compares the 
health of persons having different exposures, diets, etc. A case-
control study starts with two defined groups that differ in terms of 
their health and compares their exposure characteristics.
---------------------------------------------------------------------------

    Some degree of association between occupational dpm exposure and an 
excess risk of lung cancer was observed in 38 of the 43 studies 
reviewed by MSHA: 18 of the 19 case-control studies and 20 of the 24 
cohort studies. However, the 38 studies reporting a positive 
association vary considerably in the strength of evidence they present. 
As shown in Tables III-4 and III-5, statistically significant results 
were reported in 24 of the 43 studies: 10 of the 18 positive case-
control studies and 14 of the 20 positive cohort studies.\12\ In six of 
the 20 cohort studies and nine of the 18 case-control studies showing a 
positive association, the association observed was not statistically 
significant.
---------------------------------------------------------------------------

    \12\ A statistically significant result is a result unlikely to 
have arisen by chance in the group, or statistical sample, of 
persons being studied. An association arising by chance would have 
no predictive value for workers outside the sample. Failure to 
achieve statistical significance in an individual study can arise 
because of inherent limitations in the study, such as a small number 
of subjects in the sample or a short period of observation. 
Therefore, the lack of statistical significance in an individual 
study does not demonstrate that the results of that study were due 
merely to chance--only that the study (viewed in isolation) is 
inconclusive.
---------------------------------------------------------------------------

    Because workers tend to be healthier than non-workers, the 
incidence of disease found among workers exposed to a toxic substance 
may be lower than the rate prevailing in the general population, but 
higher than the rate occurring in an unexposed population of workers. 
This phenomenon, called the ``healthy worker effect,'' also applies 
when the rate observed among exposed workers is greater than that found 
in the general population. In this case, assuming a study is unbiased 
with respect to other factors such as smoking, comparison with the 
general population will tend to underestimate the excess risk of 
disease attributable to the substance being investigated. Several 
studies drew comparisons against the general population, including both 
workers and nonworkers, with no compensating adjustment for the healthy 
worker effect. Therefore, in these studies, the excess risk of lung 
cancer attributable to dpm exposure is likely to have been 
underestimated, thereby making it more difficult to obtain a 
statistically significant result.
    Five of the 43 studies listed in Tables III-4 and III-5 are 
negative--i.e., a lower rate of lung cancer was found among exposed 
workers than in the control population used for comparison. None of 
these five results, however, were statistically significant. Four of 
the five were cohort studies that drew comparisons against the general 
population and did not take the healthy worker effect into account. The 
remaining negative study was a case-control study in which vehicle 
drivers and locomotive engineers were compared to clerical workers.
    Two cohort studies (Waxweiler et al., 1973; Ahlman et al., 1991) 
were performed specifically on groups of miners, and one (Boffetta et 
al., 1988) addressed miners as a subgroup of a larger population. 
Although an elevated prevalence of lung cancer was found among miners 
in both the 1973 and 1991 studies, the results were not statistically 
significant. The 1988 study found, after adjusting for smoking patterns 
and other occupational exposures, an 18-percent increase in the lung 
cancer rate among all workers occupationally exposed to diesel exhaust 
and a 167-percent increase

[[Page 58157]]

among miners (relative risk = 2.67). The latter result is statistically 
significant.
    In addition, four case-control studies, all of which adjusted for 
smoking, found elevated rates of lung cancer associated with mining. 
The results for miners in three of these studies (Benhamou et al., 
1988; Morabia et al., 1992; Siemiatycki et al., 1988) are given little 
weight because of potential confounding by occupational exposures to 
other carcinogens. The other study (Lerchen et al., 1987) showed a 
marginally significant result for underground non-uranium miners, but 
this was based on very few cases and the extent of diesel exposure 
among these miners was not reported. Although they do not pertain 
specifically to mining environments, other studies showing 
statistically significant results (most notably those by Garshick et 
al., 1987 and 1988) are based on far more data, contain better diesel 
exposure information, and are less susceptible to confounding by 
extraneous risk factors.
    Since none of the existing human studies is perfect and many 
contain major deficiencies, it is not surprising that reported results 
differ in magnitude and statistical significance. Shortcomings 
identified in both positive and negative studies include: possible 
misclassification with respect to exposure; incomplete or questionable 
characterization of the exposed population; unknown or uncertain 
quantification of diesel exhaust exposure; incomplete, uncertain, or 
unavailable history of exposure to tobacco smoke and other carcinogens; 
and insufficient sample size, dpm exposure, or latency period (i.e., 
time since exposure) to detect a carcinogenic effect if one exists. 
Indeed, in their review of these studies, Stober and Abel (1996) 
conclude that ``In this field * * * epidemiology faces its limits 
(Taubes, 1995) * * * Many of these studies were doomed to failure from 
the very beginning.''
    Such problems, however, are not unique to epidemiological studies 
involving diesel exhaust but are common sources of uncertainty in 
virtually all epidemiological research involving cancer. Indeed, 
deficiencies such as exposure misclassification, small sample size, and 
short latency make it difficult to detect a relationship even when one 
exists. Therefore, the fact that 38 out of 43 studies showed any excess 
risk of lung cancer associated with dpm exposure may itself be a 
significant result, even if the evidence in most of those 38 studies is 
relatively weak.\13\ The sheer number of studies showing such an 
association readily distinguishes this body of evidence from those 
criticized by Taubes (1995), where weak evidence is available from only 
a single study.
---------------------------------------------------------------------------

    \13\ The high proportion of positive studies is statistically 
significant according to the 2-tailed sign test, which rejects, at a 
high confidence level, the null hypothesis that each study is 
equally likely to be positive or negative. Assuming that the studies 
are independent, and that there is no systematic bias in one 
direction or the other, the probability of 38 or more out of 43 
studies being either positive or negative is less than one per 
million under the null hypothesis.
---------------------------------------------------------------------------

    At the same time, MSHA recognizes that simply tabulating outcomes 
can sometimes be misleading, since there are generally a variety of 
outcomes that could render a study positive or negative and some 
studies use related data sets. Therefore, rather than limiting its 
assessment to such a tabulation, MSHA is basing its evaluation with 
respect to lung cancer largely on the two comprehensive meta-analyses 
(Lipsett and Alexeeff, 1998; Bhatia et al., 1998) described later, in 
the ``material impairments'' section of this risk assessment. In 
addition to restricting themselves to independent studies meeting 
certain minimal requirements, both meta-analyses investigated and 
rejected publication bias as an explanation for the generally positive 
results reported.
    All of the studies showing negative or statistically insignificant 
positive associations were either based on relatively short observation 
or follow-up periods, lacked good information about dpm exposure, 
involved low duration or intensity of dpm exposure, or, because of 
inadequate sample size, lacked the statistical power to detect effects 
of the magnitude found in the ``positive'' studies. As stated by 
Boffetta et al. (1988, p. 404), studies failing to show a statistically 
significant association--

    * * * often had low power to detect any association, had 
insufficient latency periods, or compared incidence or mortality 
rates among workers to national rates only, resulting in possible 
biases caused by the ``healthy worker effect.''

    Some respondents to the ANPRM argued that such methodological 
weaknesses may explain why not all of the studies showed a 
statistically significant association between dpm exposure and an 
increased prevalence of lung cancer. According to these commenters, if 
an epidemiological study shows a statistically significant result, this 
often occurs in spite of methodological weaknesses rather than because 
of them. Limitations such as potential exposure misclassification, 
inadequate latency, inadequate sample size, and insufficient duration 
of exposure all make it more difficult to obtain a statistically 
significant result when a real relationship exists.
    On the other hand, Stober and Abel (1996) argue, along with Morgan 
et al. (1997) and some commenters, that even in those epidemiological 
studies showing a statistically significant association, the magnitude 
of relative or excess risk observed is too small to demonstrate any 
causal link between dpm exposure and cancer. Their reasoning is that in 
these studies, errors in the collection or interpretation of smoking 
data can create a bias in the results larger than any potential 
contribution attributable to diesel particulate. They propose that 
studies failing to account for smoking habits should be disqualified 
from consideration, and that evidence of an association from the 
remaining studies should be discounted because of potential confounding 
due to erroneous, incomplete, or otherwise inadequate characterization 
of smoking histories.
    MSHA concurs with Cohen and Higgins (1995), Lipsett and Alexeeff 
(1998), and Bhatia et al. (1998) in not accepting this view. MSHA does 
recognize that unknown exposures to tobacco smoke or other human 
carcinogens, such as asbestos, can distort the results of some lung 
cancer studies. MSHA also agrees that significant differences in the 
distribution of confounding factors, such as smoking history, between 
study and control groups can lead to misleading results. MSHA also 
recognizes, however, that it is not possible to design a human 
epidemiological study that perfectly controls for all potentially 
confounding factors. Some degree of informed subjective judgement is 
always required in evaluating the potential significance of unknown or 
uncontrolled factors.
    Sixteen of the published epidemiological studies involving lung 
cancer did, in fact, control or adjust for exposure to tobacco smoke, 
and some of these also controlled or adjusted for exposure to asbestos 
and other carcinogenic substances (e.g., Garshick et al., 1987; 
Steenland et al., 1990; Boffetta et al., 1988). All but one of these 16 
epidemiological studies reported some degree of excess risk associated 
with exposure to diesel particulate, with statistically significant 
results reported in seven. These results are less likely to be 
confounded than results from studies with no adjustment. In addition, 
several of the other studies drew comparisons against internal control 
groups or control groups likely

[[Page 58158]]

to have similar smoking habits as the exposed groups (e.g., Garshick et 
al., 1988; Gustavsson et al., 1990; and Hansen, 1993). MSHA places more 
weight on these studies than on studies drawing comparisons against 
dissimilar groups with no controls or adjustments.
    According to Stober and Abel, the potential confounding effects of 
smoking are so strong that they could explain even statistically 
significant results observed in studies where smoking was explicitly 
taken into account. MSHA agrees that variable exposures to non-diesel 
lung carcinogens, including relatively small errors in smoking 
classification, could bias individual studies. However, the potential 
confounding effect of tobacco smoke and other carcinogens can cut in 
either direction. Spurious positive associations of dpm exposure with 
lung cancer would arise only if the group exposed to dpm had a greater 
exposure to these confounders than the unexposed control group used for 
comparison. If, on the contrary, the control group happened to be more 
exposed to confounders, then this would tend to make the association 
between dpm exposure and lung cancer appear negative. Therefore, 
although smoking effects could potentially distort the results of any 
single study, this effect could reasonably be expected to make only 
about half the studies that were explicitly adjusted for smoking come 
out positive. Smoking is unlikely to have been responsible for finding 
an excess prevalence of lung cancer in 15 out of 16 studies in which a 
smoking adjustment was applied. Based on a 2-tailed sign test, this 
possibility can be rejected at a confidence level greater than 99.9 
percent.
    Even in the 27 studies involving lung cancer for which no smoking 
adjustment was made, tobacco smoke and other carcinogens are important 
confounders only to the extent that the populations exposed and 
unexposed to diesel exhaust differed systematically with respect to 
these other exposures. Twenty-three of these studies, however, reported 
some degree of excess lung cancer risk associated with diesel exposure. 
This result could be attributed to non-diesel exposures only in the 
unlikely event that, in nearly all of these studies, diesel-exposed 
workers happened to be more highly exposed to these other carcinogens 
than the control groups of workers unexposed to diesel. All five 
studies not showing any association (Kaplan, 1959; DeCoufle, 1977; 
Waller, 1981; Edling, 1987; and Bender, 1989) may have failed to detect 
such a relationship because of too small a study group, lack of 
accurate exposure information, low duration or intensity of exposure, 
and/or insufficient latency or follow-up time.
    It is also significant that the two most comprehensive, complete, 
and well-controlled studies available (Garshick et al., 1987 and 1988) 
both point in the direction of an association between dpm exposure and 
an excess risk of lung cancer. These studies took care to address 
potential confounding by tobacco smoke and asbestos exposures. In 
response to the ANPRM, a consultant to the National Coal Association 
who was critical of all other available studies acknowledged that these 
two:

    * * * have successfully controlled for severally [sic] 
potentially important confounding factors * * * Smoking represents 
so strong a potential confounding variable that its control must be 
nearly perfect if an observed association between cancer and diesel 
exhaust is * * * [inferred to be causal]. In this regard, two 
observations are relevant. First, both case-control [Garshick et 
al., 1987] and cohort [Garshick et al., 1988] study designs revealed 
consistent results. Second, an examination of smoking related causes 
of death other than lung cancer seemed to account for only a 
fraction of the association observed between diesel exposure and 
lung cancer. A high degree of success was apparently achieved in 
controlling for smoking as a potentially confounding variable. 
[Submission 87-0-10, Robert A. Michaels, RAM TRAC Corporation, 
prepared for National Coal Association].

    Potential biases due to extraneous risk factors are unlikely to 
account for a significant part of the excess risk in all studies 
showing an association. Excess rates of lung cancer were associated 
with dpm exposure in all epidemiologic studies of sufficient size and 
scope to detect such an excess. Although it is possible, in any 
individual study, that the potentially confounding effects of 
differential exposure to tobacco smoke or other carcinogens could 
account for the observed elevation in risk otherwise attributable to 
diesel exposure, it is unlikely that such effects would give rise to 
positive associations in 38 out of 43 studies. As stated by Cohen and 
Higgins (1995):

    * * * elevations [of lung cancer] do not appear to be fully 
explicable by confounding due to cigarette smoking or other sources 
of bias. Therefore, at present, exposure to diesel exhaust provides 
the most reasonable explanation for these elevations. The 
association is most apparent in studies of occupational cohorts, in 
which assessment of exposure is better and more detailed analyses 
have been performed. The largest relative risks are often seen in 
the categories of most probable, most intense, or longest duration 
of exposure. In general population studies, in which exposure 
prevalence is low and misclassification of exposure poses a 
particularly serious potential bias in the direction of observing no 
effect of exposure, most studies indicate increased risk, albeit 
with considerable imprecision. [Cohen and Higgins (1995), p. 269].

    MSHA solicits comment on the issue of the potential for biases in 
these studies.

III.2.c.i.B.ii. Bladder Cancer

    With respect to cancers other than lung cancer, MSHA's review of 
the literature identified only bladder cancer as a possible candidate 
for a causal link to dpm. Cohen and Higgins (1995) identified and 
reviewed 14 epidemiological case-control studies containing information 
related to dpm exposure and bladder cancer. All but one of these 
studies found elevated risks of bladder cancer among workers in jobs 
frequently associated with dpm exposure. Findings were statistically 
significant in at least four of the studies (statistical significance 
was not evaluated in three).
    These studies point quite consistently toward an excess risk of 
bladder cancer among truck or bus drivers, railroad workers, and 
vehicle mechanics. However, the four available cohort studies do not 
support a conclusion that exposure to dpm is responsible for the excess 
risk of bladder cancer associated with these occupations. Furthermore, 
most of the case-control studies did not distinguish between exposure 
to diesel-powered equipment and exposure to gasoline-powered equipment 
for workers having the same occupation. When such a distinction was 
drawn, there was no evidence that the prevalence of bladder cancer was 
higher for workers exposed to the diesel-powered equipment.
    This, along with the lack of corroboration from existing cohort 
studies, suggests that the excessive rates of bladder cancer observed 
may be a consequence of factors other than dpm exposure that are also 
associated with these occupations. For example, truck and bus drivers 
are subjected to vibrations while driving and may tend to have 
different dietary and sleeping habits than the general population. For 
these reasons, MSHA does not find that convincing evidence currently 
exists for a causal relationship between dpm exposure and bladder 
cancer.

III.2.c.ii. Studies Based on Exposures to Fine Particulate in 
Ambient Air

    Longitudinal studies examine responses at given locations to 
changes in conditions over time, whereas cross-sectional studies 
compare results from locations with different conditions at a given 
point in time. Prior to 1990, cross sectional studies were generally 
used to

[[Page 58159]]

evaluate the relationship between mortality and long-term exposure to 
particulate matter, but unaddressed spatial confounders and other 
methodological problems inherent in such studies limited their 
usefulness (EPA, 1996).
    Two recent prospective cohort studies provide better evidence of a 
link between excess mortality rates and exposure to fine particulate, 
although the uncertainties here are greater than with the short-term 
exposure studies conducted in single communities. The two studies are 
known as the Six Cities study (Dockery et al., 1993), and the American 
Cancer Society (ACS) study (Pope et al., 1995).\14\ The first study 
followed about 8,000 adults in six U.S. cities over 14 years; the 
second looked at survival data for half a million adults in 151 U.S. 
cities for 7 years. After adjusting for potential confounders, 
including smoking habits, the studies considered differences in 
mortality rates between the most polluted and least polluted cities.
---------------------------------------------------------------------------

    \14\ A third such study only looked at TSP, rather than fine 
particulate. It did not find a significant association between total 
mortality and TSP. It is known as the California Seventh Day 
Adventist study (Abbey et al., 1991).
---------------------------------------------------------------------------

    Both the Six Cities Study and the ACS study found a significant 
association between increased concentration of PM2.5 and 
total mortality.\15\ The authors of the Six Cities Study concluded that 
the results suggest that exposures to fine particulate air pollution 
``contributes to excess mortality in certain U.S. cities.'' The ACS 
study, which not only controlled for smoking habits and various 
occupational exposures, but also, to some extent, for passive exposure 
to tobacco smoke, found results qualitatively consistent with those of 
the Six Cities Study.\16\ In the ACS study, however, the estimated 
increase in mortality associated with a given increase in fine 
particulate exposure was lower, though still statistically significant. 
In both studies, the largest increase observed was for cardiopulmonary 
mortality. Both studies also showed an increased risk of lung cancer 
associated with increased exposure to fine particulate, but these 
results were not statistically significant.
---------------------------------------------------------------------------

    \15\ The Six Cities study also found such relationships at 
elevated levels of PM15/10 and sulfates. The ACS study 
was designed to follow up on the fine particle result of the Six 
Cities Study, but also looked at sulfates.
    \16\ The Six Cities study did not find a statistically 
significant increase in risk among non-smokers, suggesting that this 
group might not be as sensitive to adverse health effects from 
exposure to fine particulate; however, the ACS study, with more 
statistical power, did find an association even for non-smokers.
---------------------------------------------------------------------------

    The few studies on associations between chronic PM2.5 
exposure and morbidity in adults show effects that are difficult to 
separate from measures of PM10 and measures of acid 
aerosols. The available studies, however, do show positive associations 
between particulate air pollution and adverse health effects for those 
with pre-existing respiratory or cardiovascular disease; and as 
mentioned earlier, there is a large body of evidence showing that 
respiratory diseases classified as COPD are significantly more 
prevalent among miners than in the general population. It also appears 
that PM exposure may exacerbate existing respiratory infections and 
asthma, increasing the risk of severe outcomes in individuals who have 
such conditions (EPA, 1996).

III.2.d. Mechanisms of Toxicity

    As described in Part II, the particulate fraction of diesel exhaust 
is made up of aggregated soot particles. Each soot particle consists of 
an insoluble, elemental carbon core and an adsorbed, surface coating of 
relatively soluble organic compounds, such as polycyclic aromatic 
hydrocarbons (PAH's). When released into an atmosphere, the soot 
particles formed during combustion tend to aggregate into larger 
particles.
    The literature on deposition of fine particles in the respiratory 
tract is reviewed in Green and Watson (1995) and U.S. EPA (1996). The 
mechanisms responsible for the broad range of potential particle-
related health effects will vary depending on the site of deposition. 
Once deposited, the particles may be cleared from the lung, 
translocated into the interstitium, sequestered in the lymph nodes, 
metabolized, or be otherwise transformed by various mechanisms.
    As suggested by Figure II-1 of this preamble, most of the 
aggregated particles making up dpm never get any larger than one 
micrometer in diameter. Particles this small are able to penetrate into 
the deepest regions of the lungs, called alveoli. In the alveoli, the 
particles can mix with and be dispersed by a substance called 
surfactant, which is secreted by cells lining the alveolar surfaces.
    MSHA would welcome any additional information, not already covered 
cited above, on fine particle deposition in the respiratory tract, 
especially as it might pertain to lung loading in miners exposed to a 
combination of diesel particulate and other dusts. Any such additional 
information will be placed into the public record and considered by 
MSHA before a final rule is adopted.

III.2.d.i. Effects Other than Cancer

    A number of controlled animal studies have been undertaken to 
ascertain the toxic effects of exposure to diesel exhaust and its 
components. Watson and Green (1995) reviewed approximately 50 reports 
describing noncancerous effects in animals resulting from the 
inhalation of diesel exhaust. While most of the studies were conducted 
with rats or hamsters, some information was also available from studies 
conducted using cats, guinea pigs, and monkeys. The authors also 
correlated reported effects with different descriptors of dose. From 
their review of these studies, Watson and Green concluded that:

    (a) Animals exposed to diesel exhaust exhibit a number of 
noncancerous pulmonary effects, including chronic inflammation, 
epithelial cell hyperplasia, metaplasia, alterations in connective 
tissue, pulmonary fibrosis, and compromised pulmonary function.
    (b) Cumulative weekly exposure to diesel exhaust of 70 to 80 
mghr/m3 or greater are associated with the 
presence of chronic inflammation, epithelial cell proliferation, and 
depressed alveolar clearance in chronically exposed rats.
    (c) The extrapolation of responses in animals to noncancer 
endpoints in humans is uncertain. Rats were the most sensitive 
animal species studied.

    Subsequent to the review by Watson and Green, there have been a 
number of animal studies on allergic immune responses to dpm. Takano et 
al. (1997) investigated the effects of dpm injected into mice through 
an intratracheal tube and found manifestations of allergic asthma, 
including enhanced antigen- induced airway inflammation, increased 
local expression of cytokine proteins, and increased production of 
antigen-specific immunoglobulins. The authors concluded that the study 
demonstrated dpm's enhancing effects on allergic asthma and that the 
results suggest that dpm is ``implicated in the increasing prevalence 
of allergic asthma in recent years.'' Similarly, Ichinose et al. (1997) 
found that five different strains of mice injected intratracheally with 
dpm exhibited manifestations of allergic asthma, as expressed by 
enhanced airway inflammation, which were correlated with an increased 
production of antigen-specific immunoglobulin due to the dpm. The 
authors concluded that dpm enhances manifestations of allergic airway 
inflammation and that ``* * * the cause of individual differences in 
humans at the onset of allergic asthma may be related to differences in 
antigen-induced immune responses * * *.''
    Several laboratory animal studies have been performed to ascertain

[[Page 58160]]

whether the effects of diesel exhaust are attributable specifically to 
the particulate fraction. (Heinrich et al., 1986; Iwai et al., 1986; 
Brightwell et al., 1986). These studies compare the effects of chronic 
exposure to whole diesel exhaust with the effects of filtered exhaust 
containing no particles.
    The studies demonstrate that when the exhaust is sufficiently 
diluted to nullify the effects of gaseous irritants (NO2 and 
SO2), irritant vapors (aldehydes), CO, and other systemic 
toxicants, diesel particles are the prime etiologic agents of noncancer 
health effects. Exposure to dpm produced changes in the lung that were 
much more prominent than those evoked by the gaseous fraction alone. 
Marked differences in the effects of whole and filtered diesel exhaust 
were also evident from general toxicological indices, such as body 
weight, lung weight, and pulmonary histopathology. This provides strong 
evidence that the toxic component in diesel emissions producing the 
effects noted in other animal studies is due to the particulate 
fraction.
    The mechanisms that may lead to adverse health effects in humans 
from inhaling fine particulates are not fully understood, but potential 
mechanisms that have been hypothesized for non-cancerous outcomes are 
summarized in Table III-6. A comprehensive review of the toxicity 
literature is provided in U.S. EPA (1996).
    Deposition of particulates in the human respiratory tract could 
initiate events leading to increased airflow obstruction, impaired 
clearance, impaired host defenses, or increased epithelial 
permeability. Airflow obstruction could result from laryngeal 
constriction or bronchoconstriction secondary to stimulation of 
receptors in extrathoracic or intrathoracic airways. In addition to 
reflex airway narrowing, reflex or local stimulation of mucus secretion 
could lead to mucus hypersecretion and could eventually lead to mucus 
plugging in small airways.
    Pulmonary changes that contribute to cardiovascular responses 
include a variety of mechanisms that can lead to hypoxemia, including 
bronchoconstriction, apnea, impaired diffusion, and production of 
inflammatory mediators. Hypoxia can lead to cardiac arrhythmias and 
other cardiac electrophysiologic responses that, in turn, may lead to 
ventricular fibrillation and ultimately cardiac arrest. Furthermore, 
many respiratory receptors have direct cardiovascular effects. For 
example, stimulation of C-fibers leads to bradycardia and hypertension, 
and stimulation of laryngeal receptors can result in hypertension, 
cardiac arrhythmia, bradycardia, apnea, and even cardiac arrest. Nasal 
receptor or pulmonary J-receptor stimulation can lead to vagally 
mediated bradycardia and hypertension (Widdicombe, 1988).
    In addition to possible acute toxicity of particles in the 
respiratory tract, chronic exposure to particles that deposit in the 
lung may induce inflammation. Inflammatory responses can lead to 
increased permeability and possibly diffusion abnormality. Furthermore, 
mediators released during an inflammatory response could cause release 
of factors in the clotting cascade that may lead to an increased risk 
of thrombus formation in the vascular system (Seaton, 1995). Persistent 
inflammation, or repeated cycles of acute lung injury and healing, can 
induce chronic lung injury. Retention of the particles may be 
associated with the initiation and/or progression of COPD.

III.2.d.ii. Lung Cancer

III.2.d.ii.A. Genotoxicological Evidence

    Many studies have shown that diesel soot, or its organic component, 
can increase the likelihood of genetic mutations during the biological 
process of cell division and replication. A survey of the applicable 
scientific literature is provided in Shirname-More (1995). What makes 
this body of research relevant to the risk of cancer is that mutations 
in critical genes can sometimes initiate, promote, or advance a process 
of carcinogenesis.
    The determination of genotoxicity has frequently been made by 
treating diesel soot with organic solvents such as dichloromethane and 
dimethyl sulfoxide. The solvent removes the organic compounds from the 
carbon core. After the solvent evaporates, the mutagenic potential of 
the extracted organic material is tested by applying it to bacterial, 
mammalian, or human cells propagated in a laboratory culture. In 
general, the results of these studies have shown that various 
components of the organic material can induce mutations and chromosomal 
aberrations.
    A critical issue is whether whole diesel particulate is mutagenic 
when dispersed by substances present in the lung. Since the laboratory 
procedure for extracting organic material with solvents bears little 
resemblance to the physiological environment of the lung, it is 
important to establish whether dpm as a whole is genotoxic, without 
solvent extraction. Early research indicated that this was not the case 
and, therefore, that the active genotoxic materials adhering to the 
carbon core of diesel particles might not be biologically damaging or 
even available to cells in the lung (Brooks et al., 1980; King et al., 
1981; Siak et al., 1981). A number of more recent research papers, 
however, have shown that dpm, without solvent extraction, can cause DNA 
damage when the soot is dispersed in the pulmonary surfactant that 
coats the surface of the alveoli (Wallace et al., 1987; Keane et al., 
1991; Gu et al., 1991; Gu et al., 1992). From these studies, NIOSH has 
concluded:

    * * * the solvent extract of diesel soot and the surfactant 
dispersion of diesel soot particles were found to be active in 
procaryotic cell and eukaryotic cell in vitro genotoxicity assays. 
The cited data indicate that respired diesel soot particles on the 
surface of the lung alveoli and respiratory bronchioles can be 
dispersed in the surfactant-rich aqueous phase lining the surfaces, 
and that genotoxic material associated with such dispersed soot 
particles is biologically available and genotoxically active. 
Therefore, this research demonstrates the biological availability of 
active genotoxic materials without organic solvent interaction. 
[Cover letter to NIOSH response to ANPRM].

From this conclusion, it follows that dpm itself, and not only its 
organic extract, can cause genetic mutations when dispersed by a 
substance present in the lung.
    The biological availability of the genotoxic components is also 
supported directly by studies showing genotoxic effects of exposure to 
whole dpm. The formation of DNA adducts is an important indicator of 
genotoxicity and potential carcinogenicity. If DNA adducts are not 
repaired, then a mutation or chromosomal aberration can occur during 
normal mitosis (i.e., cell replication). Hemminki et al. (1994) found 
that DNA adducts were significantly elevated in nonsmoking bus 
maintenance and truck terminal workers, as compared to a control group 
of hospital mechanics, with the highest adduct levels found among 
garage and forklift workers. Similarly, Nielsen et al. (1996) found 
that DNA adducts were significantly increased in bus garage workers and 
mechanics exposed to dpm as compared to a control group.

III.2.d.ii.B. Evidence From Animal Studies

    Bond et al. (1990) investigated differences in peripheral lung DNA 
adduct formation among rats, hamsters, mice, and monkeys exposed to dpm 
at a concentration of 8100 g/m \3\ for 12 weeks. Mice and 
hamsters showed no increase of DNA adducts in their peripheral lung 
tissue, whereas rats and monkeys showed a 60 to 80% increase. The 
increased prevalence of lung DNA adducts in monkeys suggests that, with

[[Page 58161]]

respect to DNA adduct formation, the human lungs' response to dpm 
inhalation may more closely resemble that of the rat than that of the 
hamster or mouse.
    Mauderly (1992) and Busby and Newberne (1995) provide reviews of 
the scientific literature relating to excess lung cancers observed 
among laboratory animals chronically exposed to filtered and unfiltered 
diesel exhaust. The experimental data demonstrate that chronic exposure 
to whole diesel exhaust increases the risk of lung cancer in rats and 
that dpm is the causative agent. This carcinogenic effect has been 
confirmed in two strains of rats and in at least five laboratories. 
Experimental results for animal species other than the rat, however, 
are either inconclusive or, in the case of Syrian hamsters, suggestive 
of no carcinogenic effect. This is consistent with the observation, 
mentioned above, that lung DNA adduct formation is increased among 
exposed rats but not among exposed hamsters or mice.
    The conflicting results for rats and hamsters indicate that the 
carcinogenic effects of dpm exposure may be species-dependent. Indeed, 
monkey lungs have been reported to respond quite differently than rat 
lungs to both diesel exhaust and coal dust (Nikula, 1997). Therefore, 
the results from rat experiments do not, by themselves, establish that 
there is any excess risk due to dpm exposure for humans. The human 
epidemiological data, however, indicate that humans comprise a species 
that, like rats and unlike hamsters, do suffer a carcinogenic response 
to dpm exposure. Therefore, MSHA considers the rat studies at least 
relevant to an evaluation of the risk for humans.
    When dpm is inhaled, a number of adverse effects that may 
contribute to carcinogenesis are discernable by microscopic and 
biochemical analysis. For a comprehensive review of these effects, see 
Watson and Green (1995). In brief, these effects begin with 
phagocytosis, which is essentially an attack on the diesel particles by 
cells called alveolar macrophages. The macrophages engulf and ingest 
the diesel particles, subjecting them to detoxifying enzymes. Although 
this is a normal physiological response to the inhalation of foreign 
substances, the process can produce various chemical byproducts 
injurious to normal cells. In attacking the diesel particles, the 
activated macrophages release chemical agents that attract neutrophils 
(a type of white blood cell that destroys microorganisms) and 
additional alveolar macrophages. As the lung burden of diesel particles 
increases, aggregations of particle-laden macrophages form in alveoli 
adjacent to terminal bronchioles, the number of Type II cells lining 
particle-laden alveoli increases, and particles lodge within alveolar 
and peribronchial tissues and associated lymph nodes. The neutrophils 
and macrophages release mediators of inflammation and oxygen radicals, 
which have been implicated in causing various forms of chromosomal 
damage, genetic mutations, and malignant transformation of cells 
(Weitzman and Gordon, 1990). Eventually, the particle-laden macrophages 
are functionally altered, resulting in decreased viability and impaired 
phagocytosis and clearance of particles. This series of events may 
result in pulmonary inflammatory, fibrotic, or emphysematous lesions 
that can ultimately develop into cancerous tumors.
    Such reactions have also been observed in rats exposed to high 
concentrations of fine particles with no organic component (Mauderly et 
al., 1994; Heinrich et al., 1994 and 1995; Nikula et al., 1995). Rats 
exposed to titanium dioxide or pure carbon (''carbon-black'') 
particles, which are not considered to be genotoxic, developed lung 
cancers at about the same rate as rats exposed to whole diesel exhaust. 
Therefore, it appears that the toxicity of dpm, at least in some 
species, may result largely from a biochemical response to the particle 
itself rather than from specific effects of the adsorbed organic 
compounds.
    Some researchers have interpreted the carbon-black and titanium 
dioxide studies as also suggesting that (1) the carcinogenic mechanism 
in rats depends on massive overloading of the lung and (2) that this 
may provide a mechanism of carcinogenesis specific to rats which does 
not occur in other rodents or in humans (Oberdorster, 1994; Watson and 
Valberg, 1996). Some commenters on the ANPRM cited the lack of any link 
between lung cancer and coal dust or carbon black exposure as evidence 
that carbon particles, by themselves, are not carcinogenic in humans. 
Coal mine dust, however, consists almost entirely of particles larger 
than those forming the carbon core of dpm or used in the carbon-black 
and titanium dioxide rat studies. Furthermore, although there have been 
nine studies reporting no excess risk of lung cancer among coal miners 
(Liddell, 1973; Costello et al., 1974; Armstrong et al., 1979; Rooke et 
al., 1979; Ames et al., 1983; Atuhaire et al., 1985; Miller and 
Jacobsen, 1985; Kuempel et al., 1995; Christie et al., 1995), five 
studies have reported an elevated risk of lung cancer for those exposed 
to coal dust (Enterline, 1972; Rockette, 1977; Correa et al., 1984; 
Levin et al., 1988; Morfeld et al., 1997). The positive results in two 
of these studies (Enterline, 1972; Rockette, 1977) were statistically 
significant. Furthermore, excess lung cancers have been reported among 
carbon black production workers (Hodgson and Jones, 1985; Siemiatycki, 
1991; Parent et al., 1996). MSHA is not aware of any evidence that a 
mechanism of carcinogenesis due to fine particle overload is 
inapplicable to humans. Studies carried out on rodents certainly do not 
provide such evidence.
    The carbon-black and titanium dioxide studies indicate that lung 
cancers in rats exposed to dpm may be induced by a mechanism that does 
not require the bioavailability of genotoxic organic compounds adsorbed 
on the elemental carbon particles. These studies do not, however, prove 
that the only significant agent of carcinogenesis in rats exposed to 
diesel particulate is the non-soluble carbon core. Nor do the carbon-
black studies prove that the only significant mechanism of 
carcinogenesis due to diesel particulate is lung overload. Due to the 
relatively high doses administered in the rat studies, it is 
conceivable that an overload phenomenon masks or parallels other 
potential routes to cancer. It may be that effects of the genotoxic 
organic compounds are merely masked or displaced by overloading in the 
rat studies. Gallagher et al. (1994) exposed different groups of rats 
to diesel exhaust, carbon black, or titanium dioxide and detected 
species of lung DNA adducts in the rats exposed to dpm that were not 
found in the controls or rats exposed to carbon black or titanium 
dioxide.
    Particle overload may provide the dominant route to lung cancer at 
very high concentrations of fine particulate, while genotoxic 
mechanisms may provide the primary route under lower-level exposure 
conditions. In humans exposed over a working lifetime to doses 
insufficient to cause overload, carcinogenic mechanisms unrelated to 
overload may dominate, as indicated by the human epidemiological 
studies and the data on human DNA adducts cited above. Therefore, the 
carbon black results observed in the rat studies do not preclude the 
possibility that the organic component of dpm has important genotoxic 
effects in humans (Nauss et al., 1995).
    Even if the genotoxic organic compounds in dpm were biologically 
unavailable and played no role in human carcinogenesis, this would not 
rule out the possibility of a genotoxic

[[Page 58162]]

route to lung cancer (even for rats) due to the presence of dpm 
particles themselves. For example, as a byproduct of the biochemical 
response to the presence of dpm in the alveoli, free oxidant radicals 
may be released as macrophages attempt to digest the particles. There 
is evidence that dpm can both induce production of active oxygen agents 
and also depress the activity of naturally occurring antioxidant 
enzymes (Mori, 1996; Sagai, 1993). Oxidants can induce carcinogenesis 
either by reacting directly with DNA, or by stimulating cell 
replication, or both (Weitzman and Gordon, 1990). This would provide a 
mutagenic route to lung cancer with no threshold. Therefore, the carbon 
black and titanium dioxide studies cited above do not prove that dpm 
exposure has no incremental, genotoxic effects or that there is a 
threshold below which dpm exposure poses no risk of causing lung 
cancer.
    It is noteworthy, however, that dpm exposure levels recorded in 
some mines have been almost as high as laboratory exposures 
administered to rats showing a clearly positive response. Intermittent, 
occupational exposure levels greater than about 500 g/
m3 dpm may overwhelm the human lung clearance mechanism 
(Nauss et al., 1 995). Therefore, concentrations at levels currently 
observed in some mines could be expected to cause overload in some 
humans, possibly inducing lung cancer by a mechanism similar to what 
occurs in rats. MSHA would like to receive additional scientific 
information on this issue, especially as it relates to lung loading in 
miners exposed to a combination of diesel particulate and other dusts.
    As suggested above, such a mechanism would not necessarily be the 
only route to carcinogenesis in humans and, therefore, would not imply 
that dpm concentrations too low to cause overload are safe for humans. 
Furthermore, a proportion of exposed individuals can always be expected 
to be more susceptible than normal. Therefore, at lower dpm 
concentrations, particle overload may still provide a route to lung 
cancer in susceptible humans. At even lower concentrations, other 
routes to carcinogenesis in humans may predominate, possibly involving 
genotoxic effects.

III.3. Characterization of Risk.

    Having reviewed the evidence of health effects associated with 
exposure to dpm, MSHA has evaluated that evidence to ascertain whether 
exposure levels currently existing in mines warrant regulatory action 
pursuant to the Mine Act. The criteria for this evaluation are 
established by the Mine Act and related court decisions. Section 
101(a)(6)(A) provides that:

    The Secretary, in promulgating mandatory standards dealing with 
toxic materials or harmful physical agents under this subsection, 
shall set standards which most adequately assure on the basis of the 
best available evidence that no miner will suffer material 
impairment of health or functional capacity even if such miner has 
regular exposure to the hazards dealt with by such standard for the 
period of his working life.

Based on court interpretations of similar language under the 
Occupational Safety and Health Act, there are three questions that need 
to be addressed: (1) Whether health effects associated with dpm 
exposure constitute a ``material impairment'' to miner health or 
functional capacity; (2) whether exposed miners are at significant 
excess risk of incurring any of these material impairments; and (3) 
whether the proposed rule will substantially reduce such risks.
    The criteria for evaluating the health effects evidence do not 
require scientific certainty. As noted by Justice Stevens in an 
important case on risk involving the Occupational Safety and Health 
Administration, the need to evaluate risk does not mean an agency is 
placed into a ``mathematical straightjacket.'' [Industrial Union 
Department, AFL-CIO v. American Petroleum Institute, 448 U.S. 607, 100 
S.Ct. 2844 (1980), hereinafter designated the ``Benzene'' case]. When 
regulating on the edge of scientific knowledge, certainty may not be 
possible; and--

    so long as they are supported by a body of reputable scientific 
thought, the Agency is free to use conservative assumptions in 
interpreting the data * * * risking error on the side of 
overprotection rather than underprotection. [Id. at 656].

The statutory criteria for evaluating the health evidence do not 
require MSHA to wait for absolute precision. In fact, MSHA is required 
to use the ``best available evidence.'' (Emphasis added).

III.3.a. Material Impairments to Miner Health or Functional 
Capacity

    From its review of the literature cited in Part III.2, MSHA has 
tentatively concluded that underground miners exposed to current levels 
of dpm are at excess risk of incurring the following three kinds of 
material impairment: (i) sensory irritations and respiratory symptoms; 
(ii) death from cardiovascular, cardiopulmonary, or respiratory causes; 
and (iii) lung cancer. The basis for linking these with dpm exposure is 
summarized in the following three subsections.

III.3.a.i. Sensory Irritations and Respiratory Symptoms

    Kahn et al. (1988), Battigelli (1965), Gamble et al. (1987a) and 
Rudell et al. (1996) identified a number of debilitating acute 
responses to diesel exhaust exposure: irritation of the eyes, nose and 
throat; headaches, nausea, and vomiting; chest tightness and wheeze. 
These symptoms were also reported by miners at the 1995 workshops. In 
addition, Ulfvarson et al. (1987, 1990) found evidence of reduced lung 
function in workers exposed to dpm for a single shift.
    Although there is evidence that such symptoms subside within one to 
three days of no occupational exposure, a miner who must be exposed to 
dpm day after day in order to earn a living may not have time to 
recover from such effects. Hence, the opportunity for a so-called 
``reversible'' health effect to reverse itself may not be present for 
many miners. Furthermore, effects such as stinging, itching and burning 
of the eyes, tearing, wheezing, and other types of sensory irritation 
can cause severe discomfort and can, in some cases, be seriously 
disabling. Also, workers experiencing sufficiently severe sensory 
irritations can be distracted as a result of their symptoms, thereby 
endangering other workers and increasing the risk of accidents. For 
these reasons, MSHA considers such irritations to constitute ``material 
impairments'' of health or functional capacity within the meaning of 
the Act, regardless of whether or not they are reversible. Further 
discussion of why MSHA believes reversible effects can constitute 
material impairments can be found earlier in this risk assessment, in 
the section entitled ``Relevance of Health Effects that are 
Reversible.''
    The best available evidence also points to more severe respiratory 
consequences of exposure to dpm. Significant associations have been 
detected between acute environmental exposures to fine particulates and 
debilitating respiratory impairments in adults, as measured by lost 
work days, hospital admissions, and emergency room visits. Short-term 
exposures to fine particulates, or particulate air pollution in 
general, have been associated with significant increases in the risk of 
hospitalization for both pneumonia and COPD (EPA, 1996).
    The risk of severe respiratory effects is exemplified by specific 
cases of persistent asthma linked to diesel exposure (Wade and Newman, 
1993). There is considerable evidence for a causal connection between 
dpm exposure and increased manifestations of allergic asthma and other 
allergic

[[Page 58163]]

respiratory diseases, coming from recent experiments on animals and 
human cells (Peterson and Saxon, 1996; Diaz-Sanchez, 1997; Takano et 
al., 1997; Ichinose et al., 1997). Such health outcomes are clearly 
``material impairments'' of health or functional capacity within the 
meaning of the Act.

III.3.a.ii. Excess Risk of Death from Cardiovascular, 
Cardiopulmonary, or Respiratory Causes

    The evidence from air pollution studies identifies death, largely 
from cardiovascular or respiratory causes, as an endpoint significantly 
associated with acute exposures to fine particulates. The weight of 
epidemiological evidence indicates that short-term ambient exposure to 
particulate air pollution contributes to an increased risk of daily 
mortality. Time-series analyses strongly suggest a positive effect on 
daily mortality across the entire range of ambient particulate 
pollution levels. Relative risk estimates for daily mortality in 
relation to daily ambient particulate concentration are consistently 
positive and statistically significant across a variety of statistical 
modeling approaches and methods of adjustment for effects of relevant 
covariates such as season, weather, and co-pollutants. After thoroughly 
reviewing this body of evidence, the U.S. Environmental Protection 
Agency (EPA) concluded:

    It is extremely unlikely that study designs not yet employed, 
covariates not yet identified, or statistical techniques not yet 
developed could wholly negate the large and consistent body of 
epidemiological evidence * * *.

    There is also substantial evidence of a relationship between 
chronic exposure to fine particulates and an excess (age-adjusted) risk 
of mortality, especially from cardiopulmonary diseases. The Six Cities 
and ACS studies of ambient air particulates both found a significant 
association between chronic exposure to fine particles and excess 
mortality. In both studies, after adjusting for smoking habits, a 
statistically significant excess risk of cardiopulmonary mortality was 
found in the city with the highest average concentration of fine 
particulate (i.e., PM2.5) as compared to the city with the 
lowest. Both studies also found excess deaths due to lung cancer in the 
cities with the higher average level of PM2.5, but these 
results were not statistically significant (EPA, 1996). The EPA 
concluded that--

    * * * the chronic exposure studies, taken together, suggest 
there may be increases in mortality in disease categories that are 
consistent with long-term exposure to airborne particles and that at 
least some fraction of these deaths reflect cumulative PM impacts 
above and beyond those exerted by acute exposure events * * * There 
tends to be an increasing correlation of long-term mortality with PM 
indicators as they become more reflective of fine particle levels 
(EPA, 1996).

    Whether associated with acute or chronic exposures, the excess risk 
of death that has been linked to pollution of the air with fine 
particles like dpm is clearly a ``material impairment'' of health or 
functional capacity within the meaning of the Act.

III.3.a.iii. Lung Cancer

    It is clear that lung cancer constitutes a ``material impairment'' 
of health or functional capacity within the meaning of the Act. 
Questions have been raised however, as to whether the evidence linking 
dpm exposure with an excess risk of lung cancer demonstrates a causal 
connection (Stober and Abel, 1996; Watson and Valberg, 1996; Cox, 1997; 
Morgan et al., 1997; Silverman, 1998).
    MSHA recognizes that no single one of the existing epidemiological 
studies, viewed in isolation, provides conclusive evidence of a causal 
connection between dpm exposure and an elevated risk of lung cancer in 
humans. Consistency and coherency of results, however, do provide such 
evidence. Although no epidemiological study is flawless, studies of 
both cohort and case-control design have quite consistently shown that 
chronic exposure to diesel exhaust, in a variety of occupational 
circumstances, is associated with an increased risk of lung cancer. 
With only rare exceptions, involving too few workers and/or observation 
periods too short to have a good chance of detecting excess cancer 
risk, the human studies have shown a greater risk of lung cancer among 
exposed workers than among comparable unexposed workers.
    Lipsett and Alexeeff (1998) performed a comprehensive statistical 
meta-analysis of the epidemiological literature on lung cancer and dpm 
exposure. This analysis systematically combined the results of the 
studies summarized in Tables III-4 and III-5. Some studies were 
eliminated because they did not allow for a period of at least 10 years 
for the development of clinically detectable lung cancer. Others were 
eliminated because of bias resulting from incomplete ascertainment of 
lung cancer cases in cohort studies or because they examined the same 
cohort population as another study. One study was excluded because 
standard errors could not be calculated from the data presented. The 
remaining 30 studies were analyzed using both a fixed-effects and a 
random-effect analysis of variance (ANOVA) model. Sources of 
heterogeneity in results were investigated by subset analysis; using 
categorical variables to characterize each study's design; target 
population (general or industry-specific); occupational group; source 
of control or reference population; latency; duration of exposure; 
method of ascertaining occupation; location (North America or Europe); 
covariate adjustments (age, smoking, and/or asbestos exposure); and 
absence or presence of a clear healthy worker effect (as manifested by 
lower than expected all-cause mortality in the occupational population 
under study).
    Sensitivity analyses were conducted to evaluate the sensitivity of 
results to inclusion criteria and to various assumptions used in the 
analysis. This included substitution of excluded ``redundant'' studies 
of same cohort population for the included studies and exclusion of 
studies involving questionable exposure to dpm. An influence analysis 
was also conducted to examine the effect of dropping one study at a 
time, to determine if any individual study had a disproportionate 
effect on the ANOVA. Potential effects of publication bias were also 
investigated. The authors concluded:

    The results of this meta-analysis indicate a consistent positive 
association between occupations involving diesel exhaust exposure 
and the development of lung cancer. Although substantial 
heterogeneity existed in the initial pooled analysis, stratification 
on several factors identified a relationship that persisted 
throughout various influence and sensitivity analyses* * *.
    This meta-analysis provides evidence consistent with the 
hypothesis that exposure to diesel exhaust is associated with an 
increased risk of lung cancer. The pooled estimates clearly reflect 
the existence of a positive relationship between diesel exhaust and 
lung cancer in a variety of diesel-exposed occupations, which is 
supported when the most important confounder, cigarette smoking, is 
measured and controlled. There is suggestive evidence of an 
exposure-response relationship in the smoking adjusted studies as 
well. Many of the subset analyses indicated the presence of 
substantial heterogeneity among the pooled estimates. Much of the 
heterogeneity observed, however, is due to the presence or absence 
of adjustment for smoking in the individual study risk estimates, to 
occupation-specific influences on exposure, to potential selection 
biases, and other aspects of study design.

    A second, independent meta-analysis of epidemiological studies 
published in peer-reviewed journals was conducted

[[Page 58164]]

by Bhatia et al. (1998).\17\ In this analysis, studies were excluded if 
actual work with diesel equipment ``could not be confirmed or reliably 
inferred'' or if an inadequate latency period was allowed for cancer to 
develop, as indicated by less than 10 years from time of first exposure 
to end of follow-up. Studies of miners were also excluded, because of 
potential exposure to radon and silica. Likewise, studies were excluded 
if they exhibited selection bias or examined the same cohort population 
as a study published later. A total of 29 independent studies from 23 
published sources were identified as meeting the inclusion criteria. 
After assigning each of these 29 studies a weight proportional to its 
estimated precision, pooled relative risks were calculated based on the 
following groups of studies: all 29 studies; all case-control studies; 
all cohort studies; cohort studies using internal reference 
populations; cohort studies making external comparisons; studies 
adjusted for smoking; studies not adjusted for smoking; and studies 
grouped by occupation (railroad workers, equipment operators, truck 
drivers, and bus workers). Elevated risks were shown for exposed 
workers overall and within every individual group of studies analyzed. 
A positive duration-response relationship was observed in those studies 
presenting results according to employment duration. The weighted, 
pooled estimates of relative risk were identical for case-control and 
cohort studies and nearly identical for studies with or without smoking 
adjustments. Based on their stratified analysis, the authors argued 
that--

    \17\ To address potential publication bias, the authors 
identified several unpublished studies on truck drivers and noted 
that elevated risks for exposed workers observed in these studies 
were similar to those in the published studies utilized. Based on 
this and a ``funnel plot'' for the included studies, the authors 
concluded that there was no indication of publication bias.
---------------------------------------------------------------------------

    the heterogeneity in observed relative risk estimates may be 
explained by differences between studies in methods, in populations 
studied and comparison groups used, in latency intervals, in 
intensity and duration of exposure, and in the chemical and physical 
characteristics of diesel exhaust.

They concluded that the elevated risk of lung cancer observed among 
exposed workers was unlikely to be due to chance, that confounding from 
smoking is unlikely to explain all of the excess risk, and that ``this 
meta-analysis supports a causal association between increased risks for 
lung cancer and exposure to diesel exhaust.''
    As discussed earlier in the section entitled ``Mechanisms of 
Toxicity,'' animal studies have confirmed that diesel exhaust can 
increase the risk of lung cancer in some species and shown that dpm 
(rather than the gaseous fraction of diesel exhaust) is the causal 
agent. MSHA, however, views results from animal studies as subordinate 
to the results obtained from human studies. Since the human studies 
show increased risk of lung cancer at dpm levels lower than what might 
be expected to cause overload, they provide evidence that overload may 
not be the only mechanism at work among humans. The fact that dpm has 
been proven to cause lung cancer in laboratory rats is of interest 
primarily in supporting the plausibility of a causal interpretation for 
relationships observed in the human studies.
    Similarly, the genotoxicological evidence provides additional 
support for a causal interpretation of associations observed in the 
epidemiological studies. This evidence shows that dpm dispersed by 
alveolar surfactant can have mutagenic effects, thereby providing a 
genotoxic route to carcinogenesis independent of overloading the lung 
with particles. Chemical byproducts of phagocytosis may provide another 
genotoxic route. Inhalation of diesel emissions has been shown to cause 
DNA adduct formation in peripheral lung cells of rats and monkeys, and 
increased levels of human DNA adducts have been found in association 
with occupational exposures. Therefore, there is little basis for 
postulating that a threshold exists, demarcating overload, below which 
dpm would not be expected to induce lung cancers in humans.
    Results from the epidemiological studies, the animal studies, and 
the genotoxicological studies are coherent and mutually reinforcing. 
After considering all these results, MSHA has concluded that the 
epidemiological studies, supported by the experimental data 
establishing the plausibility of a causal connection, provide strong 
evidence that chronic occupational dpm exposure increases the risk of 
lung cancer in humans.

III.3.b. Significance of the Risk of Material Impairment to Miners

    The fact that there is substantial evidence that dpm exposure can 
materially impair miner health in several ways does not imply that 
miners will necessarily suffer such impairments at a significant rate. 
This section will consider the significance of the risk faced by miners 
exposed to dpm.

III.3.b.i. Definition of a Significant Risk

    The benzene case, referred to earlier in this section, provides the 
starting point for MSHA's analysis of this issue. Soon after its 
enactment in 1970, OSHA adopted a ``consensus'' standard on exposure to 
benzene, as required and authorized by the OSH Act. The basic part of 
the standard was an average exposure limit of 10 parts per million over 
an 8-hour workday. The consensus standard had been established over 
time to deal with concerns about poisoning from this substance (448 
U.S. 607, 617). Several years later, NIOSH recommended that OSHA alter 
the standard to take into account evidence suggesting that benzene was 
also a carcinogen. (Id. at 619 et seq.). Although the ``evidence in the 
administrative record of adverse effects of benzene exposure at 10 ppm 
is sketchy at best,'' OSHA was operating under a policy that there was 
no safe exposure level to a carcinogen. (Id., at 631). Once the 
evidence was adequate to reach a conclusion that a substance was a 
carcinogen, the policy required the agency to set the limit at the 
lowest level feasible for the industry. (Id. at 613). Accordingly, the 
Agency proposed lowering the permissible exposure limit to 1 ppm.
    The Supreme Court rejected this approach. Noting that the OSH Act 
requires ``safe or healthful employment,'' the court stated that--

    * * *`safe' is not the equivalent of `risk-free'* * *a workplace 
can hardly be considered `unsafe' unless it threatens the workers 
with a significant risk of harm. Therefore, before he can promulgate 
any permanent health or safety standard, the Secretary is required 
to make a threshold finding that a place of employment is unsafe--in 
the sense that significant risks are present and can be eliminated 
or lessened by a change in practices. [Id., at 642, italics in 
original].

The court went on to explain that it is the Agency that determines how 
to make such a threshold finding:

    First, the requirement that a `significant' risk be identified 
is not a mathematical straitjacket. It is the Agency's 
responsibility to determine, in the first instance, what it 
considered to be a `significant' risk. Some risks are plainly 
acceptable and others are plainly unacceptable. If, for example, the 
odds are one in a billion that a person will die from cancer by 
taking a drink of chlorinated water, the risk clearly could not be 
considered significant. On the other hand, if the odds are one in a 
thousand that regular inhalation of gasoline vapors that are 2% 
benzene will be fatal, a reasonable person might well consider the 
risk significant and take appropriate steps to decrease or eliminate 
it. Although the Agency has no duty to calculate the exact 
probability of

[[Page 58165]]

harm, it does have an obligation to find that a significant risk is 
present before it can characterize a place of employment as 
`unsafe.' [Id., at 655].

The court noted that the Agency's ``*** determination that a particular 
level of risk is `significant' will be based largely on policy 
considerations.'' (Id., note 62).
    III.3.b.ii. Evidence of Significant Risk at Current Exposure 
Levels. In evaluating the significance of the risks to miners, a key 
factor is the very high concentrations of diesel particulate to which a 
number of those miners are currently exposed--compared to ambient 
atmospheric levels in even the most polluted urban environments, and to 
workers in diesel-related occupations for which positive 
epidemiological results have been observed. Figure III-4 compared the 
range of median dpm exposures measured for mine workers at various 
mines to the range of geometric means (i.e., estimated medians) 
reported for other occupations, as well as to ambient environmental 
levels. Figure III-5 presents a similar comparison, based on the 
highest mean dpm level observed at any individual mine, the highest 
mean level reported for any occupational group other than mining, and 
the highest monthly mean concentration of dpm estimated for ambient air 
at any site in the Los Angeles basin.\18\ As shown in Figure III-5, 
underground miners are currently exposed at mean levels up to 10 times 
higher than the highest mean exposure reported for other occupations, 
and up to 100 times higher than comparable environmental levels of 
diesel particulate.
---------------------------------------------------------------------------

    \18\ For comparability with occupational lifetime exposure 
levels, the environmental ambient air concentration has been 
multiplied by a factor of approximately 4.7. This factor reflects a 
45-year occupational lifetime with 240 working days per year, as 
opposed to a 70-year environmental lifetime with 365-days per year, 
and assumes that air inhaled during a work shift comprises half the 
total air inhaled during a 24-hour day.
[GRAPHIC] [TIFF OMITTED] TP29OC98.028


    Given the significantly increased mortality and other acute, 
adverse health effects associated with increments of 25 g/
m3 in fine particulate concentration (Table III-3), the 
relative risk for some miners, especially those already suffering 
respiratory problems, appears to be extremely high. Acute responses to 
dpm

[[Page 58166]]

exposures have been detected in studies of stevedores, whose exposure 
was likely to have been less than one tenth the exposure of some miners 
on the job.
    Both existing meta-analyses of human studies relating dpm exposure 
and lung cancer suggest that, on average, occupational exposure is 
responsible for a 30 to 40-percent increase in lung cancer risk across 
all industries studied (Lipsett and Alexeeff, 1998; Bhatia et al., 
1998). Moreover, the epidemiological studies providing the evidence of 
this increased risk involved average exposure levels estimated to be 
far below levels to which some underground miners are currently 
exposed. Specifically, the elevated risk of lung cancer observed in the 
two most extensively studied industries--trucking (including dock 
workers) and railroads--was associated with average exposure levels 
estimated to be far below levels observed in underground mines. The 
highest average concentration of dpm reported for dock workers--the 
most highly exposed occupational group within the trucking industry--is 
about 55 g/m3 total elemental carbon at an 
individual dock (NIOSH, 1990). This translates, on average, to no more 
than about 110 g/m3 of dpm. Published measurements 
of dpm for railworkers have generally been less than 140 g/
m3 (measured as respirable particulate matter other than 
cigarette smoke). The reported mean of 224 g/m3 for 
hostlers displayed in Figure III-5 represents only the worst case 
occupational subgroup (Woskie et al., 1988). Indeed, although MSHA 
views extrapolations from animal studies as subordinate to results 
obtained from human studies, it is noteworthy that dpm exposure levels 
recorded in some underground mines (Figures III-1 and III-2) have been 
well within the exposure range that produced tumors in rats (Nauss et 
al., 1995).
    The significance of the lung cancer risk to exposed underground 
miners is also supported by a recent NIOSH report (Stayner et al., 
1998), which summarizes a number of published quantitative risk 
assessments. These assessments are broadly divided into those based on 
human studies and those based on animal studies. Depending on the 
particular studies, assumptions, and methods of assessment used, 
estimates of the exact degree of risk vary widely even within each 
broad category. MSHA recognizes that a conclusive assessment of the 
quantitative relationship between lung cancer risk and specific 
exposure levels is not possible at this time, given the limitations in 
currently available epidemiological data and questions about the 
applicability to humans of responses observed in rats. However, all of 
the very different approaches and methods published so far, as 
described in Stayner et al. 1998, have produced results indicating that 
levels of dpm exposure measured at some underground mines present an 
unacceptably high risk of lung cancer for miners--a risk significantly 
greater than the risk they would experience without the dpm exposure.
    Quantitative risk estimates based on the human studies were 
generally higher than those based on analyses of the rat inhalation 
studies. As indicated by Tables 3 and 4 of Stayner et al. 1998, a 
working lifetime of exposure to dpm at 500 g/m3 
yields estimates of excess lung cancer risk ranging from about 1 to 200 
excess cases of lung cancer per thousand workers based on the rat 
inhalation studies and from about 50 to 800 per 1000 based on the 
epidemiological assessments. Even the lowest of these estimates 
indicates a risk that is clearly significant under the quantitative 
rule of thumb established in the benzene case. [Industrial Union v. 
American Petroleum; 448 U.S. 607, 100 S.Ct. 2844 (1980)].
    Stayner et al. 1998 concluded their report by stating:

    The risk estimates derived from these different models vary by 
approximately three orders of magnitude, and there are substantial 
uncertainties surrounding each of these approaches. Nonetheless, the 
results from applying these methods are consistent in predicting 
relatively large risks of lung cancer for miners who have long-term 
exposures to high concentrations of DEP [i.e., dpm]. This is not 
surprising given the fact that miners may be exposed to DEP [dpm] 
concentrations that are similar to those that induced lung cancer in 
rats and mice, and substantially higher than the exposure 
concentrations in the positive epidemiologic studies of other worker 
populations.

    The Agency is also aware that a number of other governmental and 
nongovernmental bodies have concluded that the risks of dpm are of 
sufficient significance that exposure should be limited:

    (1) In 1988, after a thorough review of the literature, the 
National Institute for Occupational Safety and Health (NIOSH) 
recommended that whole diesel exhaust be regarded as a potential 
occupational carcinogen and controlled to the lowest feasible 
exposure level. The document did not contain a recommended exposure 
limit.
    (2) In 1995, the American Conference of Governmental Industrial 
Hygienists placed on the Notice of Intended Changes in their 
Threshold Limit Values (TLV's) for Chemical Substances and Physical 
Agents and Biological Exposure Indices Handbook a recommended TLV of 
150 g/m3 for exposure to whole diesel 
particulate.
    (3) The Federal Republic of Germany has determined that diesel 
exhaust has proven to be carcinogenic in animals and classified it 
as an A2 in their carcinogenic classification scheme. An A2 
classification is assigned to those substances shown to be clearly 
carcinogenic only in animals but under conditions indicative of 
carcinogenic potential at the workplace. Based on that 
classification, technical exposure limits for dpm have been 
established, as described in part II of this preamble. These are the 
minimum limits thought to be feasible in Germany with current 
technology and serve as a guide for providing protective measures at 
the workplace.
    (4) The Canada Centre for Mineral and Energy Technology (CANMET) 
currently has an interim recommendation of 1000 g/
m3 respirable combustible dust. The recommendation was 
made by an Ad hoc committee made up of mine operators, equipment 
manufacturers, mining inspectorates and research agencies. As 
discussed in part II of this preamble, the committee has presently 
established a goal of 500 g/m3 as the 
recommended limit.
    (5) Already noted in this preamble is the U.S. Environmental 
Protection Agency's recently enacted regulation of fine particulate 
matter, in light of the significantly increased health risks 
associated with environmental exposure to such particulates. In some 
of the areas studied, fine particulate is composed primarily of dpm; 
and significant mortality and morbidity effects were also noted in 
those areas.
    (6) The California Environmental Protection Agency (CALEPA) has 
identified dpm as a toxic air contaminant, as defined in their 
Health and Safety Code, Section 39655. According to that section, a 
toxic air contaminant is an air pollutant which may cause or 
contribute to an increase in mortality or in serious illness, or 
which may pose a present or potential hazard to human health. This 
conclusion, unanimously adopted by the California Air Resources 
Board and its Scientific Review Panel on Toxic Air Contaminants, 
initiates a process of evaluating strategies for reducing dpm 
concentrations in California's ambient air.
    (7) The International Programme on Chemical Safety (IPCS), which 
is a joint venture of the World Health Organization, the 
International Labour Organisation, and the United Nations 
Environment Programme, has issued a health criteria document on 
diesel fuel and exhaust emissions (IPCS, 1996). This document states 
that the data support a conclusion that inhalation of diesel exhaust 
is of concern with respect to both neoplastic and non-neoplastic 
diseases. It also states that the particulate phase appears to have 
the greatest effect on health, and both the particle core and the 
associated organic materials have biological activity, although the 
gas-phase components cannot be disregarded.
    Based on both the epidemiological and toxicological evidence, 
the IPCS criteria document concluded that diesel exhaust is 
``probably carcinogenic to humans'' and recommended that ``in the 
occupational environment, good work practices should be encouraged, 
and adequate ventilation must

[[Page 58167]]

be provided to prevent excessive exposure.'' Quantitative 
relationships between human lung cancer risk and dpm exposure were 
derived using a dosimetric model that accounted for differences 
between experimental animals and humans, lung deposition efficiency, 
lung particle clearance rates, lung surface area, ventilation, and 
elution rates of organic chemicals from the particle surface.

    As the Supreme Court pointed out in the benzene case, the 
appropriate definition of significance also depends on policy 
considerations of the Agency involved. In the case of MSHA, those 
policy considerations include special attention to the history of the 
Mine Act. That history is intertwined with the toll to the mining 
community due to silicosis and coal miners' pneumoconiosis (``black 
lung''), along with billions of dollars in Federal expenditures.
    At one of the 1995 workshops on diesel particulate co-sponsored by 
MSHA, a miner noted:

    People, they get complacent with things like this. They begin to 
believe, well, the government has got so many regulations on so many 
things. If this stuff was really hurting us, they wouldn't allow it 
in our coal mines * * * (dpm Workshop; Beckley, WV, 1995).

Referring to some commenters' position that further scientific study 
was necessary before a limit on dpm exposure could be justified, 
another miner said:

    * * * if I understand the Mine Act, it requires MSHA to set the 
rules based on the best set of available evidence, not possible 
evidence * * * Is it going to take us 10 more years before we kill 
out, or are we going to do something now * * * ? (dpm Workshop; 
Beckley, WV, 1995).

Concern with the risk of waiting for additional scientific evidence to 
support regulation of dpm was also expressed by another miner who 
testified:

    What are the consequences that the threshold limit values are 
too high and it's loss of human lives, sickness, whatever, compared 
to what are the consequences that the values are too low? I mean, 
you don't lose nothing if they're too low, maybe a little money. But 
*** I got the indication that the diesel studies in rats could no 
way be compared to humans because their lungs are not the same * * * 
But * * * if we don't set the limits, if you remember probably last 
year when these reports come out how the government used human 
guinea pigs for radiation, shots, and all this, and aren't we doing 
the same thing by using coal miners as guinea pigs to set the value? 
(dpm Workshop; Beckley, WV, 1995).

III.3.c. Substantial Reduction of Risk by Proposed Rule

    A review of the best available evidence indicates that reducing the 
very high exposures currently existing in underground mines can 
substantially reduce health risks to miners--and that greater 
reductions in exposure would result in even lower levels of risk. 
Although there are substantial uncertainties involved in converting 24-
hour environmental exposures to 8-hour occupational exposures, Table 
III-3 suggests that reducing occupational dpm concentrations by as 
little as 75 g/m3 (corresponding to a reduction of 
25 g/m3 in 24-hour ambient atmospheric 
concentration) could lead to significant reductions in the risk of 
various adverse acute responses, ranging from respiratory irritations 
to mortality.
    Schwartz et al. (1996) found an increase of 1.5 percent in daily 
mortality associated with each increment of 10 g/m3 
in the concentration of fine particulates. Somewhat higher increases 
were reported specifically for ischemic heart disease (IHD: 2.1 
percent) and chronic obstructive pulmonary disease (COPD: 3.3 percent). 
Within the range of dust concentrations studied, the response appeared 
to be linear, with no threshold. Nor did Schwartz et al. find an 
association between increased mortality and the atmospheric 
concentration of larger particles.
    If the 24-hour average concentrations measured by Schwartz et al. 
are assumed equivalent, in their acute effects, to eight-hour average 
concentrations that are three times as high, then (assuming the mining 
and general populations respond in similar ways) each increment of 30 
g/m3 would, in an 8-hour shift occupational 
setting, be associated with a 1.5-percent increase in daily mortality. 
Since COPD and IHD were the diseases most clearly identified with acute 
diesel exposures, a conservative approach would be to limit 
consideration of any reduction in daily mortality risk under the 
proposed rule to deaths from IHD and COPD. IHD and COPD accounted for 
about one-third of the overall mortality. Thus, for purposes of 
estimating potential benefits, each reduction of 30 g/
m3 in 8-hour average dpm concentration may be assumed to 
correspond to a 0.5-percent reduction (i.e., one-third of 1.5 percent) 
in daily mortality. This estimate is somewhat conservative, insofar as 
the reported effects on IHD and COPD mortality were both greater than 
the effects on overall mortality.
    There are, however, additional problems in applying this 
incremental risk factor to underground M/NM miners. First, the levels 
of fine particulate concentration studied averaged around 20 
g/m3, which is only about 10 percent of the final 
dpm concentration limit proposed and an even smaller fraction of 
average dpm concentrations measured at some underground M/NM mines. It 
is unclear whether the same incremental effects on mortality risks 
would apply at these much higher exposure levels. Second, Schwartz et 
al. studied fine particulate concentrations, which, though generally 
related to combustion products, include but are not limited to dpm. It 
is unclear how closely these results would match the effects of fine 
particulate dust made up exclusively of dpm. Third, and also discussed 
elsewhere in MSHA's risk assessment, is the question of whether 
underground M/NM mine workers comprise a population less, equally, or 
more susceptible than the general population to acute mortality effects 
of fine particulates. It is unclear how similar an exposure-response 
relationship for miners would be to the relationship observed for the 
general population. For these reasons, benefits of the proposed rule, 
as it impacts deaths related to IHD and/or COPD among M/NM miners, 
cannot be quantified with a high degree of confidence. Subject to these 
caveats, however, applying the findings of Schwartz et al. (adjusted as 
discussed above) would suggest that, for miners currently exposed to 
dpm at an average concentration of 830 g/m3 (i.e., 
the average of measurements made by MSHA at underground M/NM mines), 
the proposed rule would reduce the acute risk of IHD/COPD mortality by 
about 10 percent [(830 - 200) g/m3  x  (0.5% 
 30 g/m3)].
    Quantitative assessments of the relationship between human dpm 
exposures and lung cancer, which would show just how many cases of lung 
cancer a given reduction in exposure could be expected to prevent, have 
produced varying results and are subject to considerable uncertainty 
(Stayner et al., 1998; US-EPA, 1998). None of the human-based dose-
response relationships has been widely accepted in the scientific 
community, most likely due to a lack of precisely quantified dpm 
exposures in the available epidemiological studies. Although future 
studies may provide a better foundation for quantitative risk 
assessment, the Agency believes it would not be prudent to postpone 
protection of miners exposed to extremely high dpm levels until a 
conclusive dose-response relationship becomes available. In the 
meantime, the published, human-based quantitative risk assessments 
reviewed by Stayner et al. (1998) provide the best available means of 
estimating the reduction in lung cancer risk to underground M/NM miners 
that may be expected from reducing dpm exposures.
    Among the human-based assessments reviewed, even the lowest 
estimate of

[[Page 58168]]

unit risk of developing lung cancer is 10-4 per each 
g/m3 of dpm exposure over a 45-year occupational 
lifetime at 8 hours of exposure per workday. It should be noted that 
this risk estimate was derived from exposures estimated to be generally 
below the proposed final limit. As Stayner et al. point out, there are 
some questions raised by extrapolating estimated risks to exposure 
levels up to 10 times as high, but doing so is unavoidable in order to 
estimate benefits based on existing data. On the other hand, the issue 
of whether a threshold exists is of little or no concern when assessing 
risk at these higher exposure levels. MSHA specifically requests 
information regarding any studies on miner mortality at high dpm 
exposures and the accuracy of the assumption of linearity.
    Assuming this dose-response relationship, it is possible to 
estimate the reduction in lung cancers that could be expected as a 
result of implementing the proposed rule. To form such an estimate, 
however, measures of both current and proposed levels of dpm exposure 
are also required.
    Table III-7 presents three estimates of current dpm exposure 
levels:

      Table III-7.--Measures of DPM Exposure in Production Areas and Haulageways of Underground M/NM Mines
----------------------------------------------------------------------------------------------------------------
                                                                      Employment size of mine
                                                 ---------------------------------------------------------------
                                                                                                   All Affected
                                                        <20          20 to 500         >500            Mines
----------------------------------------------------------------------------------------------------------------
Number of Affected Mines........................              82             114               7             203
Number of Affected Miners.......................             460           3,770           3,270           7,500
----------------------------------------------------------------------------------------------------------------
                          Dpm Concentration Estimated from Diesel Equipment Inventory
----------------------------------------------------------------------------------------------------------------
Based on Test Data (g/m3)..............           2,766           1,880           1,232           1,863
Adjusted for Observed Duty Cycle (g/m3)           1,951           1,331             877           1,319
----------------------------------------------------------------------------------------------------------------
Mean dpm Concentration Level Observed in Underground M/NM Mines (g/m3)                              830
----------------------------------------------------------------------------------------------------------------

    In its inventory of underground M/NM mines, MSHA collected data on 
diesel powered equipment, ventilation throughput, and the volume of the 
work areas. MSHA then estimated dpm concentration levels in the mines 
by combining these data with emissions data for the diesel engines 
obtained during testing in accordance with MSHA's engine approval 
process. The estimate of mean dpm concentration obtained by this method 
is 1,863 g/m3.
    MSHA then compared the duty cycles for the diesel powered equipment 
used in the tests to the duty cycles observed in the mines. 
Recalibrating the results for the observed duty cycles lowered the 
estimated dpm concentrations by approximately 30 percent. The adjusted 
estimate of mean dpm concentration is 1,319 g/m3.
    The third estimate of current mean dpm concentration shown in Table 
III-7 is the mean dpm concentration measured during MSHA's field 
studies, as shown in Table III-1 of this preamble. MSHA's dpm 
measurements averaged 830 g/m3 at underground M/NM 
mines.
    Applying the 10-4 estimate of unit risk to these three 
dpm concentration levels produces estimates of excess risk, for a 45-
year period of exposure, of 186 cancers per 1,000 miners, 132 cancers 
per 1,000 miners, and 83 cancers per 1,000 miners, respectively. These 
estimates assume that the 45-year period of occupational exposure 
begins at age 20 and that the excess risk of dying from lung cancer is 
accumulated from age 20 through age 85-a span of 65 years.
    Approximately 9,400 miners work in underground areas of M/NM mines 
that use diesel powered equipment, and MSHA estimates that about 80 
percent (i.e., 7,500) of these work in production or development areas 
including haulageways. Therefore, if the 7,500 affected miners were all 
exposed for a full 45 years, this dose-response relationship would 
yield, over the 65-year period from time of first occupational 
exposure, 1,395 excess cancers, 990 excess cancers, or 622 excess 
cancers, corresponding to the three estimates of current mean exposure. 
For purposes of projecting benefits of the proposed rule, MSHA is 
restricting its attention to the lowest of these estimates, since it is 
based on actual measurements of dpm concentration.
    Although many individual miners may work in underground M/NM mines 
for a full 45 years (and the Mine Act requires MSHA to set standards 
that protect workers exposed for a full working lifetime), MSHA 
believes that it may also be appropriate to estimate benefits of the 
proposed rule based on the mean duration of exposure. If the mean 
exposure time is actually 20 years, then the estimated excess risk of 
lung cancer could be reduced by roughly a factor of 20/45, from 83 per 
thousand miners to about 37 per thousand miners. However, since the 
total number of miners exposed during a given 45-year period will now 
be increased by a factor of 45/20, the total number of excess lung 
cancers expected at current exposure levels remains the same: 622, or 
an average of 9.6 per year, spread over an initial 65-year period.
    After final implementation of the proposed rule, dpm concentrations 
in underground M/NM mines would be limited to a maximum of 
approximately 200 g/m3 on each and every shift. 
Therefore, since concentrations would be expected to generally fall 
below their maximum value, it would be reasonable to assume that the 
average concentration would fall below 200 g/m3. 
(MSHA's sampling found concentrations under controlled conditions as 
low as 55 g/m3). So as not to overstate benefits, 
MSHA has projected residual risk under the proposed rule assuming the 
concentration limit of 200 g/m3 is exactly met on 
all shifts at all mines.
    From Table IV of Stayner et al. (1998), the lowest human-based risk 
estimate among workers occupationally exposed to 200 
g/m3 for 45 years is 21 excess lung 
cancers per 1000 exposed miners. For the population of 7,500 
underground M/NM mine workers, this would amount to 158 excess lung 
cancers over an initial 65-year period, or an average of 2.4 excess 
lung cancers per year. If, as before, a 20-year average is assumed for 
occupational exposure, this reduces an individual miner's risk to a 
hypothetical 9.3 excess lung cancers per thousand exposed miners under 
the proposed rule, but the total number of

[[Page 58169]]

excess lung cancers expected over the initial 65-year period remains 
the same. Thus, under the assumptions stated, the benefit of the 
proposed rule in reducing incidents of lung cancer can be expressed as:
     622 - 158 = 464 lung cancers avoided over an initial 65-
year period; \19\ or
---------------------------------------------------------------------------

    \19\ In the long run, the average approaches 464  45 = 
10 lung cancers avoided per year as the number of years considered 
increases beyond 65.
---------------------------------------------------------------------------

     464  65 = approximately 7 lung cancers avoided per 
year over an initial 65-year period; or
     83 - 21 = 62 lung cancers avoided per 1,000 miners 
occupationally exposed for 45 years; or
     37 - 9.3 = 28 lung cancers avoided per 1,000 miners 
occupationally exposed for 20 years.
    The Agency recognizes that a conclusive, quantitative dose-response 
relationship has not been established between dpm and lung cancer in 
humans. However, the epidemiological studies relating dpm exposure to 
excess lung cancer were conducted on populations whose average exposure 
is estimated to be less than 200 g/m3 and less than 
one tenth of average exposures observed in some underground mines. 
Therefore, the best available evidence indicates that lifetime 
occupational exposure at levels currently existing in some underground 
mines presents a significant excess risk of lung cancer.
    In the case of underground M/NM mines, the proposed rule limits dpm 
concentration to 200 g/m3 by limiting the measured 
concentration of total carbon to 160 g/m3. The 
Agency recognizes that although health risks would be substantially 
reduced, the best available evidence indicates a significant risk of 
adverse health effects would remain at these levels. However, as 
explained in Part V of this preamble, MSHA has concluded that, because 
of both technology and cost considerations, the underground M/NM mining 
sector as a whole cannot feasibly reduce dpm concentrations further at 
this time.
    Conclusions. MSHA has reviewed a considerable body of evidence to 
ascertain whether and to what level dpm should be controlled. It has 
evaluated the information in light of the legal requirements governing 
regulatory action under the Mine Act. Particular attention was paid to 
issues and questions raised by the mining community in response to the 
Agency's Advance Notice of Proposed Rulemaking and at workshops on dpm 
held in 1995. Based on its review of the record as a whole to date, the 
agency has tentatively determined that the best available evidence 
warrants the following conclusions:

    1. The health effects associated with exposure to dpm can 
materially impair miner health or functional capacity.
    These material impairments include sensory irritations and 
respiratory symptoms; death from cardiovascular, cardiopulmonary, or 
respiratory causes; and lung cancer.
    2. At exposure levels currently observed in underground M/NM 
mines, many miners are presently at significant risk of incurring 
these material impairments over a working lifetime.
    3. The proposed rule for underground M/NM mines is justified 
because the reduction in dpm exposure levels that would result from 
implementation of the proposed rule would substantially reduce the 
significant health risks currently faced by underground M/NM miners 
exposed to dpm.

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 Table III-3.--Studies of Acute Health Effects Using Gravimetric Indicators of Fine Particles in the Ambient Air
----------------------------------------------------------------------------------------------------------------
                                                              RR( CI)/
                                          Indicator           25g/m \3\ PM       Mean PM levels (min/
                                                                    increase                  max)
----------------------------------------------------------------------------------------------------------------
                                                 Acute Mortality
----------------------------------------------------------------------------------------------------------------
Six Cities A
    Portage, WI...................  PM2.5................  1.030 (0.993,1.071).......  11.2 (7.8)
    Topeka, KS....................  PM2.5................  1.020 (0.951,1.092).......  12.2 (7.4)
    Boston, MA....................  PM2.5................  1.056 (1.038,1.0711)......  15.7 (9.2)
    St. Louis, MO.................  PM2.5................  1.028 (1.010,1.043).......  18.7 (10.5)
    Kingston/Knoxville, TN........  PM2.5................  1.035 (1.005,1.066).......  20.8 (9.6)
    Steubenville, OH..............  PM2.5................  1.025 (0.998,1.053).......  29.6 (21.9)
----------------------------------------------------------------------------------------------------------------
                                           Increased Hospitalization
----------------------------------------------------------------------------------------------------------------
Ontario, CAN B....................  SO4=.................  1.03 (1.02, 1.04).........  Min/Max = 3.1-8.2
Ontario, CAN C....................  SO4=.................  1.03 (1.02, 1.04).........  Min/Max = 2.0-7.7
                                    O3...................  1.03 (1.02, 1.05)
NYC/Buffalo, NY D.................  SO4=.................  1.05 (1.01, 1.10).........  NR
Toronto, CAN D....................  H+ (Nmo1/m \3\)......  1.16 (1.03, 1.30) *.......  28.8 (NR/391)
                                    SO4=.................  1.12 (1.00, 1.24).........  7.6 (NR, 48.7)
                                    PM2.5................  1.15 (1.02, 1.78).........  18.6 (NR, 66.0)
----------------------------------------------------------------------------------------------------------------
                                         Increased Respiratory Symptoms
----------------------------------------------------------------------------------------------------------------
Southern California F.............  SO4=.................  1.48 (1.14, 1.91).........  R = 2-37
Six Cities G (Cough)..............  PM2.5................  1.19 (1.01, 1.42)**.......  18.0 (7.2, 37)***
                                    PM2.5 Sulfur.........  1.23 (0.95, 1.59)**.......  2.5 (3.1, 61)***
                                    H+...................  1.06 (0.87, 1.29)**.......  18.1 (0.8, 5.9)***
Six Cities G (Lower Resp. Symp.)..  PM2.5................  1.44 (1.15-1.82)**........  18.0 (7.2, 37)***
                                    PM2.5 Sulfur.........  1.82 (1.28-2.59)**........  2.5 (0.8, 5.9)***
                                    H+...................  1.05 (0.25-1.30)**........  18.1 (3.1, 61)***
Denver, CO P (Cough, adult          PM2.5................  0.0012 (0.0043)***........  0.41-73
 asthmatics).                       SO4=.................  0.0042 (0.00035)***.......  0.12-12
                                    H+...................  0.0076 (0.0038)***........  2.0-41
----------------------------------------------------------------------------------------------------------------
                                            Decreased Lung Function
----------------------------------------------------------------------------------------------------------------
Uniontown, PA E...................  PM2.5................  PEFR 23.1 (-0.3, 36.9)      25/88 (NR/88)
                                                            (per 25 g/m \3\).
Seattle, WA Q Asthmatics..........  bext.................  FEV1 42 ml (12, 73).......  5/45
                                    calibrated by PM2.5..  FVC 45 ml (20, 70)
----------------------------------------------------------------------------------------------------------------
(EPA, 1996).
A Schwartz et al. (1996a).
B Burnett et al. (1994).
C Burnett et al. (1995) O3.
D Thurston et al. (1992, 1994).
E Neas et al. (1995).
F Ostro et al. (1993).
G Schwartz et al. (1994).
Q Koenig et al. (1993).
P Ostro et al. (1991).
 Min/Max 24-h PM indicator level shown in parentheses unless otherwise noted as (S.D), 10
  and 90 percentile (10, 90).
* Change per 100 nmoles/m \3\.
** Change per 20 g/m \3\ for PM2.5; per 5 g/m \3\ for PM2.5; sulfur; per 25 nmoles/m \3\ for
  H+.
*** 50th percentile value (10, 90 percentile).
**** Coefficient and SE in parenthesis.


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IV. Discussion of Proposed Rule

    This part of the preamble explains, section-by-section, the 
provisions of the proposed rule. As appropriate, this part references 
discussions in other parts of this preamble: in particular, the 
background discussions on measurement methods and controls in Part II, 
and the feasibility discussions in Part V.
    The proposed rule would add nine new sections to 30 CFR Part 57 
immediately following Sec. 57.5015. It would not amend any existing 
sections of that part.

Section 57.5060  Limit on Concentration of Diesel Particulate Matter

    This section of the proposed rule limits the concentration of dpm 
in underground metal and nonmetal mines. It has four subsections.
    Paragraph (a) of Sec. 57.5060 provides that 18 months after the 
date of promulgation, dpm concentrations to which miners are exposed 
would be limited by restricting total carbon to 400 micrograms per 
cubic meter of air. As proposed by the rule, this limit would apply 
only for a period of 36 months; accordingly, it is sometimes referred 
to in this preamble as the ``interim'' concentration limit.
    Paragraph (b) of Sec. 57.5060 provides that after five years the 
proposed concentration limit would be reduced, restricting total carbon 
to 160 micrograms per cubic meter of air. This is sometimes referred to 
in this preamble as the ``final'' concentration limit.
    Paragraph (c) of Sec. 57.5060 provides for a special extension of 
up to two additional years in order for a mine to comply with the final 
concentration limit. This special extension is only available when the 
mine operator can establish that the final concentration limit cannot 
be met within the five years allotted due to technological constraints. 
The proposed rule establishes the details that must be provided in the 
application process, and conditions that must be observed during the 
special extension period. Paragraph (c) of the proposed rule refers to 
this extension as ``special'' because the proposed rule would also 
provide all mines in this sector with up to five years to meet the 
final concentration limit.
    Paragraph (d) of Sec. 57.5060 provides that an operator shall not 
utilize personal protective equipment to comply with either the interim 
or final concentration limit. Moreover, it provides that an operator 
shall not utilize administrative controls to comply with either the 
interim or final concentration limit. These restrictions do not 
explicitly apply to an operator who has been provided with a special 
extension of time to comply with the final concentration limit pursuant 
to paragraph (c).
    Choice of Controls. With the exceptions specified in paragraph (d), 
the proposed rule contemplates that an operator of an underground metal 
or nonmetal mine have complete discretion over the controls utilized to 
meet the interim and final concentration limits. No specific controls 
would be required for any type of diesel engine, for any type of diesel 
equipment, or for any type of mine in this sector. An operator could 
filter the emissions from diesel-powered equipment, install cleaner-
burning engines, increase ventilation, improve fleet management, or use 
a variety of other available controls.
    Because information on available controls has been described in 
Part II of this preamble, including the ``Toolbox'' (appended to the 
end of this document is a copy of an MSHA publication, ``Practical Ways 
to Reduce Exposure to Diesel Exhaust in Mining--A Toolbox''), further 
discussion is not provided here. Reviewers are also referred to the 
extensive discussion of available controls in Part V of this preamble 
concerning the technological and economic feasibility of this rule for 
the underground metal and nonmetal mining sector.
    To help mine operators decide among various alternative 
combinations of engineering and ventilation controls, MSHA has 
developed a model that it believes will assist an operator to 
determine, for a production area of a mine, the effect of any 
combination of controls on existing dpm concentrations in that area. 
This model, known as the ``Estimator'', is in the form of a spreadsheet 
template; this permits instant display of outcomes as inputs are 
altered. The model is described in detail in Part V of this preamble, 
and some examples illustrating its potential utility are described 
there. MSHA welcomes comments from the mining community concerning this 
model, and encourages mine operators to submit their results as part of 
their comments.
    Expression of Limits. The interim and final concentration limits on 
diesel particulate matter are expressed in terms of a restriction on 
the amount of total carbon present. The purpose of the interim and 
final concentration limits is to limit the amount of diesel particulate 
matter to which miners are exposed; but the limit is being expressed in 
terms of the measurement method that MSHA intends to utilize to 
determine the concentration of dpm. The idea is to enable miners, mine 
operators and inspectors to directly compare a measurement result with 
the applicable limit.
    As discussed in connection with proposed Sec. 57.5061(a), MSHA 
intends to use a sampling and analytical method developed by NIOSH 
(NIOSH Analytical Method 5040) to measure dpm concentrations for 
compliance purposes. NIOSH's Analytical Method 5040 accurately 
determines the amount of total carbon (TC) contained in a dpm sample 
from any underground metal and nonmetal mine.
    As explained in detail in Part II of this preamble, whole diesel 
particulate matter can be measured in a variety of ways. But to date, a 
method that measures whole dpm directly has not been validated as 
providing accurate measurements at lower concentration levels with the 
consistency desirable for compliance purposes. However, MSHA believes 
that for underground metal and nonmetal mines, there is a surrogate 
method with the requisite accuracy. The surrogate is a method that 
determines the amount of certain component parts of whole dpm. Whole 
dpm basically consists of: the elemental carbon (EC) making up the core 
of the dpm particle; the organic carbon (OC) contained in adsorbed 
hydrocarbons; and some sulfates. (See Figure II-3 for a graphic 
representation of a dpm particle). The total carbon (TC) consists of 
the EC and the OC. NIOSH Method 5040 has been shown to measure TC with 
adequate accuracy. As discussed in Part II, MSHA is not aware at this 
time of any interferents that would in practice preclude MSHA from 
using this method to obtain consistent results in underground metal and 
nonmetal mines; hence, the Agency is proposing to use this method for 
compliance.
    TC represents approximately 80-85 percent of the total mass of dpm 
emitted in the exhaust of a diesel engine (the remaining 15-20 percent 
consists of sulfates and the various elements bound up with the organic 
carbon to form the adsorbed hydrocarbons). Using the lower boundary of 
this range, limiting the concentration of total carbon to 400 
micrograms per cubic meter (400TC g/m3) 
limits the concentration of whole diesel particulate to about 
500DPM g/m3. Similarly, limiting the 
concentration of total carbon to 160TC g/
m3 limits the concentration of whole diesel particulate to 
about 200DPM g/m3.
    By way of comparison, MSHA has measured dpm average concentrations 
in underground metal and nonmetal mines from about 68DPM 
g/m3 to 1,835DPM g/
m3. MSHA has recorded

[[Page 58183]]

some concentrations as high as 5,570DPM g/
m3. Complete information about these measurements, and the 
methods used in measuring them, are discussed in Part III of this 
preamble.
    Where the Concentration Limit Applies. The concentration limits--
both interim and final--would apply only in areas where miners normally 
work or travel. The purpose of this restriction is to ensure that mine 
operators do not have to monitor particulate concentrations in areas 
where miners do not normally work or travel -- e.g., abandoned areas of 
a mine. However, the appropriate concentration limit would need to be 
maintained in any area of a mine where miners normally work or travel 
even if miners might not be present at any particular time. (For a 
discussion of MSHA's proposed sampling strategy, see the discussion of 
proposed Sec. 57.5061(a)).
    Full-shift, 8-hour Equivalent. The proposed interim and final 
concentration limits are expressed in terms of the average airborne 
concentration during each full shift expressed as an 8-hour equivalent. 
Measuring over a full shift ensures that average exposure is monitored 
over the same period to which the limit applies. Using an 8-hour 
equivalent dose ensures that a miner who works extended shifts--and 
many do--would not be exposed to more dpm than a miner who works a 
normal shift. The Agency welcomes comment on whether a more explicit 
definition is required in this regard.
    Concentration Limit: Time to Meet. As noted, the dpm limitation 
being proposed would require metal and nonmetal mines to reduce dpm 
concentrations in areas where miners normally work or travel to about 
200 micrograms per cubic meter of air (specifically, total carbon would 
have to be restricted to 160 micrograms per cubic meter of air). 
Proposed Sec. 57.5060 provides an extension of time for underground 
metal and nonmetal mines to meet the concentration limit. Mines would 
not have to meet any limit within 18 months of the rule's promulgation. 
This period would be used to provide compliance assistance to the metal 
and nonmetal mining community to ensure it understands how to measure 
and control diesel particulate matter concentrations in individual 
operations. Moreover, the proposed rule would provide all mines in this 
sector three and a half additional years to meet the final 
concentration limit established by proposed Sec. 57.5060(b). During 
this time, however, all mines would have to bring dpm concentrations 
down to 500 micrograms per cubic meter by complying with a restriction 
on the concentration of submicrometer total carbon of 400 micrograms 
per cubic meter.
    MSHA established these requirements after carefully reviewing 
questions presented by the mining community regarding economic and 
technological feasibility of requiring all mines in this sector to meet 
the proposed concentration limit with available controls. This review 
is presented in Part V of this preamble. MSHA has studied a number of 
metal and nonmetal mines in which it believed dpm might be particularly 
difficult to control. The Agency has tentatively concluded that in 
combination with the ``best practices'' required under other provisions 
of the proposed rule (Secs. 57.5065, 57.5066 and 57.5067), engineering 
and work practice controls are available that can bring dpm 
concentrations in all underground metal and nonmetal mines down to or 
below 400TC g/m3 within 18 months. 
Moreover, based on the mines it has examined to date, the Agency has 
tentatively concluded that controls are available to bring dpm 
concentrations in underground metal and nonmetal mines down to or below 
160TC g/m3 within 5 years.
    The Agency has tentatively concluded that it may not be feasible to 
require this sector, as a whole, to lower dpm concentrations further, 
or to implement the required controls more swiftly. Nevertheless, as 
noted in Part V, the Agency is seeking information, examples and 
comment that will assist it in making a final determination on these 
points.
    Special Extension. An operator may request more than five years to 
comply with the final concentration limit only in the case of 
technological constraints that preclude compliance. MSHA has determined 
that it is economically feasible for the mining industry as a whole to 
comply with the proposed concentration limit within five years. In 
light of the risks to miners posed by dpm, the Agency does not believe 
the economic constraints of a particular operator should provide an 
adequate basis for a further extension of time for that operator, and 
the proposal would not provide for any extension grounded on economic 
concerns. Moreover, if it is technologically feasible for an operator 
to reduce dpm concentrations to the final limit in time through any 
approach, no extension would be permitted even if a more cost effective 
solution might be available in the future for that operator.
    However, the Agency believes that if an operator can actually 
demonstrate that there is no technological solution that could reduce 
the concentration of dpm within five years, a special extension would 
be warranted. As a practical matter, MSHA believes that very few, if 
any, underground metal and nonmetal mining operations should need a 
special extension. MSHA bases this belief on information discussed in 
Part V of this preamble with respect to the feasibility of the proposed 
standard, and comments on that information are specifically solicited. 
Despite this information, and just in case a few mines experience 
technical problems that cannot be foreseen at this time, the proposed 
rule would make provision for a special extension to allow up to an 
additional two years to comply with the final concentration limit.
    Extension Application. Proposed Sec. 57.5060(c)(1) provides that if 
an operator of an underground metal or nonmetal mine can demonstrate 
that there is no combination of controls that can, due to technological 
constraints, be implemented within five years to reduce the 
concentration of dpm to the limit, MSHA may approve an application for 
an additional extension of time to comply with the dpm concentration 
limit. Under the proposal, such a special extension is available only 
once, and is limited to 2 years. To obtain a special extension, an 
operator must show that diesel powered equipment was used in the mine 
prior to publication of the rule, demonstrate that there is no off-the-
shelf technology available to reduce dpm to the limit specified in 
Sec. 57.5060, and establish the lowest achievable concentration of dpm 
attainable. The proposed rule further requires that to establish the 
lowest achievable concentration, the operator is to provide sampling 
data obtained using NIOSH Method 5040 (the method MSHA will use when 
determining concentrations for compliance purposes). The sampling 
method is further discussed in connection with proposed 
Sec. 57.5061(a).
    The application would also require the mine operator to specify the 
actions that are to be taken to ``maintain the lowest concentration of 
diesel particulate achievable'' (such as strict adherence to an 
established control plan) and to minimize miner exposure to dpm (e.g., 
provide suitable respirators). MSHA's intent is to ensure that personal 
protective equipment and administrative controls are permitted only as 
a last and temporary resort to bridge the gap between what can be 
accomplished with engineering and work practice controls and the 
concentration limit. It is not the Agency's intent that personal 
protective equipment or administrative controls be

[[Page 58184]]

permitted during the extension period as a substitute for engineering 
and work practice controls that can be implemented immediately. The 
Agency would welcome comments on whether more explicit clarification of 
this point in the proposed rule is required.
    Filing, Posting and Approval of Extension Application. The proposed 
rule would require that an application for an extension be filed (after 
being posted for 30 days at the mine site) no later than 6 months (180 
days) in advance of the date of the final concentration limit (160tc 
g/m3). The proposed rule would also require that a 
copy of the approved extension be posted at the mine site for the 
duration of the extension period. In addition, a copy of the 
application would also have to be provided to the authorized 
representative of the miners.
    The application would be required to be approved by MSHA before it 
becomes effective. While pre-approval of plans is not the norm in this 
sector, an exception to the final concentration limit cannot be 
provided without careful scrutiny. Moreover, in some cases, the 
examination of the application may enable MSHA to point out to the 
operator the availability of solutions not considered to date.
    While the proposed rule is not explicit on the point, it is MSHA's 
intent that primary responsibility for approval of the operator's 
application for an extension will rest with MSHA's district managers. 
This ensures familiarity with the mine conditions, and provides an 
opportunity to consult with miners as well. At the same time, MSHA 
recognizes that district managers may not have the expertise required 
to keep fully abreast of the latest technologies and of solutions being 
used in similar mines elsewhere in the country. Accordingly, the Agency 
intends to establish, within its Technical Support directorate in 
Washington, D.C., a special panel to consult on these issues and to 
provide assistance to its district managers. MSHA would welcome 
comments on this matter, and as to whether it should incorporate 
further specifics in this regard into the final rule.
    Personal Protective Equipment and Administrative Controls. 
Paragraph (d) provides that an operator shall not utilize personal 
protective equipment (e.g., respirators) or administrative controls 
(e.g., rotation of miners) to comply with either the interim or final 
concentration limit. Moreover, it provides that an operator shall not 
utilize administrative controls (e.g., the rotation of miners) to 
comply with either the interim or final concentration limit.
    Limiting individual miner exposure through rotation or through the 
use of respirators would not reduce the airborne concentrations of 
particulate matter. It is accepted industrial hygiene practice to 
eliminate or minimize hazards at the source by using engineering or 
work practices, before resorting to alternative controls. Moreover, 
administrative controls are not considered acceptable in the case of 
potential carcinogens, since they result in placing more workers at 
risk.
    MSHA intends that the normal meaning be given to the terms personal 
protective equipment and administrative controls, and welcomes comments 
as to whether more specificity would be useful. For example, the Agency 
assumes the mining community understands that an environmentally 
controlled cab for a piece of equipment is not a piece of personal 
protective equipment; indeed, the cost estimates for the proposed rule 
assume that such cabs will be a commonly used control to meet the 
proposed limits in those situations in which the only miners present in 
an area are equipment operators (see Part V of this preamble and the 
Agency's PREA).

Section 57.5061  Compliance Determinations

    Under the proposed rule, compliance sampling would be performed by 
MSHA directly, and a single sample would be adequate to establish a 
violation.
    The proposed rule further provides that MSHA will collect and 
analyze dpm samples for total carbon (TC) content using NIOSH Method 
5040 (or by using any method subsequently determined by NIOSH to 
provide equal or improved accuracy in mines subject to this part). 
NIOSH Method 5040 provides for sample collection using a dust sampler 
pump and an open face filter. The filters are analyzed for elemental 
carbon (EC) and organic carbon (OC) content using the thermo-optical 
technique; the EC and OC concentration determinations are then added 
together to obtain the TC concentration of the sample.
    Measurement Method for Compliance. Section 3 of Part II of this 
preamble discusses alternative methods for measuring dpm 
concentrations. As noted in that discussion, after considering the 
comments received in response to MSHA's ANPRM, reviewing the available 
technical information submitted in response to the ANPRM and reviewing 
the status of current technology, MSHA believes that NIOSH Method 5040 
provides an accurate method of determining the total carbon content of 
a sample collected in any underground metal or nonmetal mine when using 
the sampling procedures specified in Method 5040. At the present time, 
Method 5040 is the only method that meets NIOSH's accuracy criterion 
for determinations of both EC and OC down to concentrations as low as 
those that will need to be measured to determine compliance with the 
final concentration limit being proposed. Accordingly, MSHA proposes to 
use this method for determining TC concentrations for compliance 
purposes.
    Margin of Error. Before issuing a citation, MSHA intends to take 
into consideration uncertainty associated with the sampling and 
analytical process, as it does in other cases. While the measurement 
uncertainty has not been established for samples collected in mines, 
NIOSH has established the variability associated with Method 5040 to be 
approximately 6% (one relative standard deviation). If MSHA used the 
variability value established by NIOSH and allowed for a confidence 
level of 95%, MSHA would not issue a citation until the measured value 
was greater than 1.10 times the levels established in Sec. 57.5060. For 
example, if the variability established by NIOSH is used, during the 
interim period when the limit is 400TC g/
m3 a noncompliance determination would not be made unless 
the TC measurement exceeded 440 g/m3.
    MSHA recognizes that the measurement uncertainty may be higher for 
samples collected in mines, and intends to establish as the ``margin of 
error'' required to achieve a 95% confidence level for all 
noncompliance determinations based on samples collected in mines. The 
Agency anticipates that the margin of error will end up being somewhere 
between 10% and 20%, but will be governed by the actual data on this 
point.
    Sampling Strategy. Proposed Sec. 57.5060 would establish a 
concentration limit for areas of a mine where miners normally work or 
travel to limit miner exposure to dpm. In using this language, MSHA 
intends that the limits on the concentration of dpm would apply to 
persons, occupations or areas, as with coal dust. Accordingly, MSHA 
intends that inspectors have the flexibility to determine, on a mine by 
mine basis, the most appropriate method to assess the level of hazard 
that exists. The Agency may sample by attaching a sampler to an 
individual miner, or by locating the sampler on a piece of equipment 
where a miner may

[[Page 58185]]

work, or at a fixed site where miners normally work or travel.
    Sampling strategy was discussed by commenters who responded to the 
ANPRM. Several commenters indicated that the sampling strategy should 
ensure that samples taken are representative of actual exposure. Other 
commenters stated that the sampling strategy would be dictated by the 
measurement method, and that several strategies could be used to 
determine the hazard. They stated that the strategy should not be 
defined so narrowly as to exclude development of new sampling methods.
    A related issue addressed by the commenters was whether personal or 
area sampling would be more appropriate. Most commenters indicated that 
personal sampling was the most reliable indicator of worker exposure. 
Some noted that in underground mines which use mobile diesel equipment, 
the positions of diesel-powered vehicles with respect to intake and 
return air streams vary from hour to hour. Therefore, it is virtually 
impossible to obtain meaningful information from stationary 
instruments. Several commenters stated that area sampling was 
appropriate to define action levels that may trigger personal sampling 
or to evaluate effectiveness of controls. Some additional concerns were 
raised concerning the accuracy of the sampling device when worn by a 
miner.
    MSHA agrees that there may be circumstances when either area or 
personal sampling may be appropriate. Considering the mobility of the 
equipment it may not always be feasible to sample individual workers; 
for example, if work practice would include rotation of workers into an 
area. In this case, area sampling would be more appropriate to 
establish a hazard. MSHA does recognize that the diesel particulate is 
ultimately transported to return entries or exhaust openings of a mine.
    The purpose of these entries is to provide a means to transport 
contaminated air away from the active workings. MSHA does not intend to 
conduct area sampling in these areas; however, personal sampling of 
workers who enter these areas could be conducted. These circumstances 
would be evaluated on a mine-by-mine basis during mine inspections. 
Accordingly, MSHA will utilize either area or personal (within 36'' of 
a miners breathing zone) sampling to determine whether corrective 
actions must be taken by a mine operator. In return entries, 
measurements made in the immediate area where diesel equipment is being 
operated will be collected at locations that are no closer than five 
feet from any piece of operating diesel equipment.

Section 57.5062  Diesel Particulate Matter Control Plan

    A determination of noncompliance with either the interim or final 
concentration limit prescribed by Sec. 57.5060 would trigger a 
requirement that: first, the operator establish a diesel particulate 
matter control plan (dpm control plan)-- or modify the plan if one is 
already in effect; and second, the operator demonstrate that the new or 
modified plan is effective in controlling the concentration of dpm to 
the applicable concentration limit.
    No Advance Approval Required. The agency proposes to continue to 
observe the metal and nonmetal mine plan tradition by not requiring a 
formal plan approval process. That is, the plan would not require 
advance approval of the MSHA District Manager. A dpm control plan 
would, however, have to meet certain requirements set forth in the 
proposed rule, and it would be a violation of Sec. 57.5062 if MSHA 
determines the operator has failed to include the necessary 
particulars.
    Elements of Plan. Under proposed Sec. 57.5062(b), a dpm control 
plan must describe the controls the operator will utilize to maintain 
the concentration of diesel particulate matter to the applicable limit 
specified by Sec. 57.5060. The plan must also include a list of diesel-
powered units used by the mine operator, together with information 
about any unit's emission control device, and the parameters of any 
other methods used to control the concentration of diesel particulate 
matter.
    Relationship to Ventilation Plan. At the discretion of the 
operator, the dpm control plan may be consolidated with the ventilation 
plan required by Sec. 57.8520.
    Demonstration of Plan Effectiveness. The proposed rule would 
require monitoring to verify that the dpm control plans are actually 
effective in reducing dpm concentrations in the mine to the applicable 
concentration limit. Because the dpm control plan was initiated as a 
result of a compliance action, the proposed rule would require the use 
of the same measurement method used by MSHA in compliance 
determinations--total carbon using NIOSH Method 5040--to conduct 
verification sampling.
    Effectiveness must be demonstrated by ``sufficient'' monitoring to 
confirm that the plan or amended plan will control the concentration of 
diesel particulate to the applicable limit under conditions that can be 
``reasonably anticipated'' in the mine. The proposed rule does not 
specify that any defined number of samples must be taken--the intent is 
that the sampling provide a fair picture of whether the plan or amended 
plan is working. MSHA will determine compliance with this obligation 
based on a review of the situation involved. While an MSHA compliance 
sample may be an indicator that the operator has not fulfilled their 
obligation under this section to undertake monitoring ``sufficient'' to 
verify plan effectiveness, it would be inconclusive on that point. The 
Agency welcomes comment on this point.
    Similarly, the Agency welcomes comment on whether, and how, it 
should define the term ``reasonably anticipated.'' With respect to coal 
dust, the Dust Advisory Committee recommended that ``MSHA should define 
the range of production values which must be maintained during sampling 
to verify the plan. This value should be sufficiently close to maximum 
anticipated production'' (MSHA, 1996). For dpm, the equivalent approach 
might be based on worst-case operating conditions of the diesel 
equipment--e.g., all equipment is being operated simultaneously with 
the least ventilation.
    Recordkeeping Retention and Access. Pursuant to Sec. 57.5062(b), a 
copy of the current dpm control plan is to be maintained at the mine 
site during the duration of the plan and for one year thereafter. 
Proposed Sec. 57.5062(c) would require that verification sample results 
be retained for 5 years. Proposed Sec. 57.5062(d) provides that both 
the control plan and sampling records verifying effectiveness be made 
available for review, upon request, by the authorized representative of 
the Secretary, the Secretary of Health and Human Services, and/or the 
authorized representative of miners. Upon request of the District 
Manager or the authorized representative of miners, a copy of these 
records is to be provided by the operator.

Duration. The proposal would require the dpm control plan to remain 
in effect for three years from the date of the violation resulting 
in the establishment/modification of the plan. As discussed in Part 
I of this preamble (Question and Answer 18), MSHA believes 
operators have sufficient time under the proposed rule to come into 
compliance with the concentration limits. If a problem exists, 
maintaining a plan in effect long enough to ensure that daily mine 
practices really change, is an important safeguard.

    Modification During Plan Lifetime. A violation of Sec. 57.5060 
would require the

[[Page 58186]]

mine operator to modify the dpm control plan to reflect changes in 
mining equipment and/or the mine environment and the operator would be 
required to demonstrate to MSHA the effectiveness of the modified plan.
    Also, proposed Sec. 57.5062(e)(2) would require the mine operator 
to modify the dpm control plan to reflect changes in mining equipment 
and/or the mine environment and the operator would be required to 
demonstrate to MSHA the effectiveness of the modified plan.
    Compliance with Plan Requirements. Once an underground metal or 
nonmetal mine operator adopts a dpm control plan, it will be considered 
regulation for the mine. Proposed 57.5062(f) specifically provides that 
MSHA would not need to establish (by sampling) that an operator is 
currently in violation of the applicable concentration limit under 
Sec. 57.5060 in order to determine by observation that an operator has 
failed to comply with any requirement of the mine's dpm control plan.

Section 57.5065  Fueling and idling practices

    Fueling Practices. Part II of this preamble contains some 
background information on fueling practices, together with information 
about the rules currently applicable in underground coal mines.
    Proposed Sec. 57.5065(a) would require underground metal and 
nonmetal mine operators to use only low-sulfur fuel having a sulfur 
content of no greater than 0.05 percent. This requirement is identical 
to that currently required for diesel equipment used in underground 
coal mines [30 CFR 75.1901(a)]. Both number 1 and number 2 diesel fuel 
meet the requirement of this proposal.
    Sulfur content can have a significant effect on diesel emissions. 
Use of low sulfur diesel fuel reduces the sulfate fraction of dpm 
emissions, reduces objectionable odors associated with diesel exhaust, 
and allows oxidation catalysts to perform properly. A major benefit of 
using low sulfur fuel is that the reduction of sulfur allows for the 
use of some aftertreatment devices such as catalytic converters and 
catalyzed particulate traps which were prohibited with fuels of high 
sulfur content (greater than 0.05 percent sulfur). MSHA believes the 
use of these aftertreatment devices is important to the mining industry 
because they will be necessary to meet the levels specified. The 
requirement to use low sulfur fuel will allow these devices to be used 
without additional adverse effects caused by the high sulfur fuel. As 
noted in Part IV of the PREA, MSHA does not believe such a requirement 
will add additional cost.
    Proposed paragraph (b) of this section would require mine operators 
to use only diesel fuel additives that have been registered by the 
Environmental Protection Agency (40 CFR Part 79). Again, this proposed 
rule is consistent with that currently required for diesel equipment 
used in underground coal mines [30 CFR 75.1901(c)]. The restricted use 
of additives would ensure that diesel particulate concentrations would 
not be inadvertently increased, while also protecting miners against 
the emission of other toxic contaminants. MSHA issued Program 
Information Bulletin No. P97-10, on May 5, 1997, that discusses the 
fuel additives list. The requirements of this paragraph do not place an 
undue burden on mine operators because operators need only verify with 
their fuel suppliers or distributors that the additive purchased is 
included on the EPA registration list.
    Idling Practices. Proposed Sec. 57.5065(c) would prohibit idling of 
mobile-powered diesel equipment, except as required for normal mining 
operations. The idling requirements being proposed for underground 
metal and nonmetal mines are consistent with the idling requirements 
currently required for underground coal mines (Sec. 75.1916(d)).
    MSHA believes that keeping idling to a minimum is very important to 
reduce pollution in mine atmospheres. Engines operating without a load 
during idling can produce significant levels of both gaseous and 
particulate emissions. Even though the concentration emitted from a 
single idling engine might have little effect on the overall mine 
environment, a localized, increased exposure of the gaseous and 
particulate concentrations would occur. In underground operations, an 
engine idling in an area of minimal ventilation or a ``dead air'' space 
could cause an excess exposure to the gaseous emissions, especially 
carbon monoxide, as well as to dpm. Eliminating unnecessary idling 
would reduce localized exposure to high particulate concentrations.
    While the proposed rule is intended to prevent idling except as 
required for normal mining operations, it does not define normal mining 
operations. MSHA envisions ``normal mining operations'' to be 
activities such as idling while waiting for a load to be unhooked, or 
waiting in line to pick up a load. These types of activities would be 
permitted. Idling while eating lunch is normally not part of the job 
and operators would be in violation of the standard. Idling necessary 
due to very cold weather conditions would be permitted. On the other 
hand, idling in other weather conditions just to keep balky, older 
engines running would not be permitted; in such cases, the correct 
approach is better maintenance. MSHA welcomes comments on whether a 
more specific definition is necessary, particularly in light of any 
experience to date under the parallel rule for diesel equipment in 
underground coal mines.

Section 57.5066  Maintenance Standards

    Proposed Sec. 57.5066(a) would place emphasis on the fact that 
diesel engine emissions are lower from an engine that is properly 
maintained than from an engine that is not. Part II of the preamble 
provides more information on this point.
    Approved Engines. Proposed Sec. 57.5066(a)(1) would require that 
mine operators maintain any approved diesel engine in ``approved'' 
condition. Under MSHA's approval requirements, engine approval is tied 
to the use of certain parts and engine specifications. When these parts 
or specifications are changed (i.e., an incorrect part is used, or the 
engine timing is incorrectly set), the engine is no longer considered 
by MSHA to be in approved condition.
    Often, engine exhaust emissions will deteriorate when this occurs. 
Maintaining approved engines in their approved condition will ensure 
near-original performance of an engine, and maximize vehicle 
productivity and engine life, while keeping exhaust emissions at 
approved levels. The proposed maintenance requirements for approved 
engines in this rule are already applicable to underground coal mines, 
where only approved engines may be utilized (30 CFR 75.1914).
    Thus in practice, with respect to approved engines, mine 
maintenance personnel will have to maintain the following engine 
systems in near original condition: air intake, cooling, lubrication, 
fuel injection and exhaust. These systems must be maintained on a 
regularly scheduled basis to keep the system in its ``approved'' 
condition and thus, operating at its expected efficiency.
    One of the best ways to ensure these standards are observed is to 
implement a proper maintenance program in the mine--but the proposed 
rule would not require operators to do this. A good program should 
include compliance with manufacturers' recommended maintenance 
schedules, maintenance of accurate records and the use of proper 
maintenance procedures. MSHA's diesel toolbox provides more information 
about the practices that should be

[[Page 58187]]

followed in maintaining diesel engines in mines.
    Non-approved Engines. For any non-approved diesel engine, proposed 
paragraph (a)(2) would require mine operators to maintain the emissions 
related components to manufacturer specifications.
    The term ``emission related components,'' refers to the parts of 
the engine that directly affect the emission characteristics of the raw 
exhaust. These are basically the same components which MSHA examines 
for ``approved'' engines. They are the piston, intake and exhaust 
valves, cylinder head, injector, fuel injection pump, governor, 
turbocharger, after cooler, injection timing, and fuel pump calibrator.
    It is not MSHA's intent that engines be torn down and the engine 
components be compared against the specifications in manufacturer 
maintenance manuals. Primarily, the Agency is interested in ensuring 
that engines are maintained in accordance with the schedule recommended 
by the manufacturer. However, if it becomes evident that the engines 
are not being maintained to the correct specifications or are being 
rebuilt in a configuration not in line with manufacturers' 
specifications or approval requirements, an inspector may ask to see 
the manuals to confirm that the right manuals are being used, or call 
in MSHA experts to examine an engine to confirm whether basic 
specifications are being properly observed. MSHA welcomes comment on 
alternative ways to phrase this requirement so Agency has a basis for 
ensuring compliance while minimizing the opportunity for over-
prescriptiveness.
    Emission or Particulate Control Device. Proposed paragraph (a)(3) 
would require that any emission or particulate control device installed 
on diesel-powered equipment be maintained in effective operating 
condition. Depending on the type of devices installed on an engine, 
this would involve having trained personnel perform such basic tasks as 
regularly cleaning aftertreatment filters, using methods recommended by 
the manufacturer for that purpose, or inserting appropriate replacement 
filters when required, checking for and repairing any exhaust system 
leaks, and other appropriate actions.
    Tagging of Equipment for Noncompliance. Proposed Sec. 57.5066(b)(1) 
would require underground metal and nonmetal mine operators to 
authorize and require miners operating diesel powered equipment to 
affix a visible and dated tag to the equipment at any time the 
equipment operator detects an emission-related problem.
    MSHA believes tagging will provide an effective and efficient 
method of alerting all mine personnel that a piece of equipment needs 
to be checked by qualified service personnel. The tag may be affixed 
because the equipment operator detects a problem through a visual exam 
conducted before the equipment is started, or because of a problem that 
comes to the attention of the equipment operator during mining 
operations, (i.e., black smoke while the equipment is under normal 
load, rough idling, unusual noises, backfiring, etc.)
    MSHA is not proposing that equipment tagged for potential emission 
problems be automatically taken out of service. The proposal is not, 
therefore, directly comparable to a ``tag-out'' requirement like OSHA's 
requirement for automatic powered machinery, nor is it as stringent as 
MSHA's requirement to remove from service certain equipment ``when 
defects make continued operation hazardous to persons'' (see 30 CFR 
57.14100). The proposed rule is not as stringent as these requirements 
because, although exposure to dpm emissions does pose a serious health 
hazard for miners, the existence or scope of an equipment problem 
cannot be determined until the equipment is examined or tested by a 
person competent to assess the situation. Moreover, the danger is not 
as immediate as, for example, an explosive hazard.
    Proposed Sec. 57.5066(b)(2) would require that the equipment be 
``promptly'' examined by a person authorized by the mine operator to 
maintain diesel equipment. (The qualifications for those who maintain 
and service diesel engines are discussed below). The Agency has not 
tried to define the term ``promptly,'' but welcomes comment on whether 
it should do so--in terms, for example, of a limited number of shifts. 
The presence of a tag serves as a caution sign to miners working on or 
near the equipment, as well as a reminder to mine management, as the 
equipment moves from task to task throughout the mine. While the 
equipment is not barred from service, operators would be expected to 
use common sense and not use it in locations in which diesel 
particulate concentrations are known to be high.
    Proposed paragraph (b)(2) would permit a tag to be removed after 
the defective equipment has been examined.
    The design of the tag is left to the discretion of the mine 
operator, with the exception that the tag must be able to be marked 
with a date. Comments are welcome on whether some or all elements of 
the tag should be standardized to ensure its purpose is met.
    Tagged Equipment Log. Proposed Sec. 57.5066(b)(3) would require a 
log to be retained of all equipment tagged. Moreover, the log must 
include the date the equipment is tagged, the date the tagged equipment 
is examined, the name of the person making the examination, and the 
action taken as a result of the examination. Records in the log about a 
particular incident must be retained for at least a year after the 
equipment is tagged.
    MSHA does not expect the log to be burdensome to the mine operator 
or mechanic examining or testing the engine. Based on MSHA's 
experience, it is common practice to maintain a log when equipment is 
serviced or repaired, consistent with any good maintenance program. The 
records of the tagging and servicing, although basic, provide mine 
operators, miners and MSHA with a history that will help in determining 
whether a maintenance program is being effectively implemented.
    Qualified Person. Proposed paragraph (c) would require that persons 
who maintain diesel equipment in underground metal and nonmetal mines 
be ``qualified,'' by virtue of training and experience, to ensure the 
maintenance standards of proposed Sec. 57.5066(a) are observed. 
Paragraph (c) also requires that an operator retain appropriate 
evidence of ``the competence of any person to perform specific 
maintenance tasks'' in compliance with the requirement's maintenance 
standards for one year.
    The ANPRM requested information concerning specialized training for 
those persons working on equipment that uses particulate reduction 
technology and the costs associated with the training. Commenters 
stated that any equipment modifications will require additional 
training. The extent and costs would vary widely depending on the type 
of devices used. MSHA agrees that training should be given when new 
devices or modifications to machines are made. The training cost will 
be dependent on the complexity of the control device.
    Operators of underground coal mines where diesel-powered equipment 
is used are required, as of November 25, 1997, to establish programs to 
ensure that persons who perform maintenance, tests, examinations and 
repairs on diesel-powered equipment are qualified (30 CFR 75.1915). The 
unique conditions in underground coal mines require the use of 
specialized

[[Page 58188]]

equipment. Accordingly, the qualifications of the persons who maintain 
this equipment generally must be appropriately sophisticated.
    If repairs and adjustments to diesel engines used in underground 
metal and nonmetal mines are to be done properly, personnel performing 
such tasks must be properly trained. MSHA does not believe, however, 
that the qualifications required to perform this work in underground 
metal and nonmetal mines necessarily require the same level of training 
as for similar work in underground coal mines. Under the proposed rule, 
the training required would be that which is commensurate with the 
maintenance task involved. If examining and, if necessary, changing a 
filter or air cleaner is all that is required, a miner who has been 
shown how to do these tasks would be qualified by virtue of training or 
experience to do those tasks. For more detailed work, specialized 
training or additional experience would be required. Training by a 
manufacturer's representative, completion of a general diesel engine 
maintenance course, or practical experience performing such repairs 
could also serve as evidence of having the qualifications to perform 
the service.
    In practice, the results will soon be revealed by performance. If 
MSHA finds a situation where maintenance appears to be shoddy, where 
the log indicates an engine has been in for repair with more frequency 
than should be required, or where repairs have damaged engine approval 
status or emission control effectiveness, MSHA would ask the operator 
to provide evidence that the person(s) who worked on the equipment was 
properly qualified by virtue of training or experience.
    It is MSHA's intent that equipment sent off-site for maintenance 
and repair is also subject to the requirement that the personnel 
performing the repair be qualified by virtue of training or experience 
for the task involved. It is not MSHA's intent that a mine operator 
have to examine the training and experience record of off-site 
mechanics, but a mine operator will be expected to observe the same 
kind of caution as one would observe with a personal vehicle--e.g., 
selecting the proper kind of shop for the nature of the work involved, 
and considering prior direct experience with the quality of the shop's 
work.

Section 57.5067  Engines

    The proposed rule would require that, with the exception of diesel 
engines used in ambulances and fire-fighting equipment, any diesel 
engines added to the fleet of an underground metal or nonmetal mine in 
the future must be an engine approved by MSHA under Part 7 or Part 36. 
This requirement would take effect 60 days after the date the rule is 
promulgated.
    The composition of the existing fleet would not be impacted by this 
part of the proposed rule. However, after the rule's effective date, an 
operator would not be permitted to bring into underground areas of a 
mine an unapproved engine from the surface area of the same mine, an 
area of another mine, or from a non-mining operation. Promoting a 
gradual turnover of the existing fleet to better engines is an 
appropriate response to the health risk presented by dpm.
    Approval is not something that has to be done by individual mine 
operators. Approved engines carry an approval plate so they are easy to 
distinguish. Approval is a process that is handled by engine 
manufacturers, involving tests by independent laboratories.
    MSHA is assuming in the PREA accompanying this proposed rule that 
this additional requirement will require manufacturers to obtain 
approval on one additional diesel engine model per year. Some engines 
currently used in metal and nonmetal mines may have no approval 
criteria; in such cases, MSHA will work with the manufacturers to 
develop approval criteria consistent with those MSHA uses for other 
diesel engines. Based upon preliminary analysis, MSHA has tentatively 
concluded that any diesel engine meeting current on-highway and non-
road EPA emission requirements would meet MSHA's engine approval 
standards of Part 7, subpart E, category B type engine. (See section 4 
of Part II of this preamble for further information about these 
engines.)
    Currently, the EPA non-road test cycle and MSHA's test cycle are 
the same for determining the gaseous and particulate emissions. MSHA 
envisions being able to use the EPA test data for engines run on the 
non-road test cycle for determining the gaseous ventilation rate and 
particulate index. The engine manufacturer would continue to submit the 
proper paper work for a specific model diesel engine to receive the 
MSHA approval. However, engine data run on the EPA on-highway transient 
test cycle would not as easily be usable to determine the gaseous 
ventilation and particulate index. Comments on how MSHA can facilitate 
review of engines not currently approved would be welcome.
    Engines in diesel-powered ambulances and fire-fighting equipment 
would be exempted from these requirements. This exemption is identical 
with that in the rule for diesel-powered equipment in underground coal 
mines.

Section 57.5070  Miner Training

    Proposed Sec. 57.5070 would require any miner ``who can reasonably 
be expected to be exposed to diesel emissions'' be trained annually in: 
(a) The health risks associated with dpm exposure; (b) the methods used 
in the mine to control dpm concentrations; (c) identification of the 
personnel responsible for maintaining those controls; and (d) actions 
miners must take to ensure the controls operate as intended.
    The purpose of the proposed requirement is to promote miner 
awareness. Exposure to diesel particulate is associated with a number 
of harmful effects as discussed in Part III of this preamble, and the 
safe level is unknown. Miners who work in mines where they are exposed 
to this risk ought to be reminded of the hazard often enough to make 
them active and committed partners in implementing actions that will 
reduce that risk.
    The training need only be provided to miners who can reasonably be 
expected to be exposed at the mine. The training is to be provided by 
operators; hence, it is to be without fee to the miner.
    The rule places no constraints on the operator as to how to 
accomplish this training. MSHA believes that the required training can 
be provided at minimal cost and minimal disruption. The proposal would 
not require any special qualifications for instructors, nor would it 
specify the hours of instruction.
    Instruction could take place at safety meetings before the shift 
begins. Devoting one of those meetings to the topic of dpm would be a 
very easy way to convey the necessary information. Simply providing 
miners with a copy of MSHA's ``Toolbox'' and, a copy of the plan, if a 
control plan is in effect for the mine, and reviewing these documents, 
can cover several of the training requirements. One-on-one discussions 
that cover the required topics are another approach that can be used.
    Operators could also choose to include a discussion on diesel 
emissions in their Part 48 training, provided the plan is approved by 
MSHA. There is no existing requirement that Part 48 training include a 
discussion of the hazards and control of diesel emissions. While mine 
operators are free to cover additional topics during the Part 48 
training sessions, the topics that must be covered during the required 
time frame may make it impracticable to cover other matters within the 
prescribed time limits.

[[Page 58189]]

Where the time is available in mines using diesel-powered equipment, 
operators would be free to include the dpm instruction in their Part 48 
training plans. The Agency does not believe special language in the 
proposed rule is required to permit this action under Part 48, but 
welcomes comment in this regard.
    The proposal does not require the mine operator to separately 
certify the completion of the dpm training, but some evidence that the 
training took place would have to be produced upon request. A serial 
log with the employee's signature is an acceptable practice.
    To assist mine operators with the proposed training requirement, it 
is MSHA's intent to develop an instruction outline that mine operators 
can use as a guide for training personnel. Instruction materials will 
be provided with the outline.

Section 57.5071  Environmental Monitoring

    Operator's Monitoring Responsibility. Proposed Sec. 57.5071(a) 
would require that mine operators sample their mine environments to 
evaluate environmental conditions to which miners are exposed. It is 
proposed that sampling be performed as often as necessary to 
``effectively evaluate''--under conditions that can be reasonably 
anticipated in the mine--(1) Whether the dpm concentration in any area 
of the mine where miners normally work or travel exceeds the applicable 
limit; and (2) the average full shift airborne concentration at any 
position or on any person designated by the Secretary.
    There are two important aspects of this proposed operator 
monitoring requirement. First, it would clarify that it is the 
responsibility of mine operators to be aware of the concentrations of 
dpm in all areas of the mine where miners normally work or travel, so 
as to know whether action is needed to ensure that the concentration is 
kept below the applicable limit. Secondly, this requirement would 
ensure special attention to locations or persons known to MSHA to have 
a significant potential for overexposure to dpm.
    The obligation of operators to ``effectively evaluate'' 
concentrations in a mine is a separate obligation from that to keep dpm 
levels below the established limit, and can be the basis of a separate 
citation from MSHA. The proposed rule is performance-oriented in that 
the regularity and methodology used to make this evaluation are not 
specified. However, MSHA expects mine operators to sample with such 
frequency that they and the miners working at the mine site are aware 
of dpm levels in their work environment. In this regard, MSHA's own 
measurements will assist the Agency in verifying the effectiveness of 
an operator's monitoring program. If an operator is ``effectively 
evaluating'' the concentration of dpm at designated positions, for 
example, MSHA would not expect to regularly record concentrations above 
the limit when it samples at that location. If MSHA does find such a 
problem, it will investigate to determine how frequently an operator is 
sampling, where the operator is sampling, and what methodology is being 
used, so as to determine whether the obligation in this section is 
being fulfilled.
    MSHA proposed a performance-oriented operator sampling requirement 
in its recent proposed rule on noise, and is seeking some consistency 
of approach in this regard for uniform health standards.
    Operator Monitoring Methods. The proposed rule requires that full-
shift diesel particulate concentrations be determined during periods of 
normal production or normal work activity, in areas where miners work 
or travel. The proposed rule does not specify a particular monitoring 
method or frequency; rather, the proposal is performance-oriented. 
Operators may, at their discretion, conduct their monitoring using the 
same sampling and analytical method as MSHA, or they may use any other 
method that enables that mine to ``effectively evaluate'' the 
concentrations of dpm. Monitoring performed to verify the effectiveness 
of a diesel particulate control plan would probably meet the obligation 
under proposed Sec. 57.5071 if it is done with enough sufficiency to 
meet the obligation under proposed Sec. 7.5062(c).
    As discussed in connection with proposed Sec. 57.5061, MSHA intends 
to use NIOSH Method 5040, the sampling and analytical method that NIOSH 
has developed for accurately determining the concentration of total 
carbon. Operators are also required to use the TC method for verifying 
the effectiveness of dpm control plans, as discussed in connection with 
proposed Sec. 57.5062. But the method may not be necessary to 
effectively evaluate dpm in some mines. For example, dpm measurements 
in limestone, potash and salt mines could be determined using the RCD 
method, since there are no large carbonaceous particles present that 
would interfere with the analysis. Such estimates can be useful in 
determining the effectiveness of controls and where more refined 
measurements may be required.
    Of course, mine operators using the RCD, or size-selective methods, 
to monitor their diesel particulate concentrations would have to 
convert the results to a TC equivalent to ascertain their exact 
compliance status. At the present time, MSHA has no conversion tables 
for this purpose. In most cases, the other methods will provide a good 
indication of whether controls are working and whether further action 
is required.
    Part II of this preamble provides information on monitoring methods 
and their constraints, and on laboratory and sampler availability.
    Observation of Monitoring. Section 103(c) of the Mine Act requires 
that:

    The Secretary, in cooperation with the Secretary of Health, 
Education, and Welfare, shall issue regulations requiring operators 
to maintain accurate records of employee exposures to potentially 
toxic materials or harmful physical agents which are required to be 
monitored or measured under any applicable mandatory health or 
safety standard promulgated under this Act. Such regulations shall 
provide miners or their representatives with an opportunity to 
observe such monitoring or measuring, and to have access to the 
records thereof.

    In accordance with this legal requirement, proposed Sec. 57.5071(b) 
requires a mining operator to provide affected miners and their 
representatives with an opportunity to observe exposure monitoring 
required by this section. Mine operators must give prior notice to 
affected miners and their representatives of the date and time of 
intended monitoring.
    MSHA has proposed identical language in a supplement to its 
proposed rule on noise (62 FR 68468).
    Corrective Action if Concentration is Exceeded. Proposed 
Sec. 57.5071(c) provides that if any monitoring performed under this 
section indicates that the applicable dpm concentration limit has been 
exceeded, an operator shall initiate corrective action by the next work 
shift, promptly post a notice of the corrective action being taken and 
promptly complete such corrective action.
    MSHA welcomes comments as to what guidance to provide with respect 
to the obligations in this regard where an operator is not using the 
total carbon method. MSHA also welcomes comment as to whether personal 
notice of corrective action would be more appropriate than posting, 
given the health risks involved.
    The Agency wishes to emphasize that operator monitoring of dpm 
concentrations would not take the place of MSHA sampling for compliance 
purposes; rather, this requirement is

[[Page 58190]]

designed to ensure the operator checks dpm concentrations on a more 
regular basis than it is possible for MSHA to do.
    Proposed paragraph (c) provides that if sampling results indicate 
the concentration limit has been exceeded in an area of a mine, an 
operator would initiate corrective action by the next work shift and 
promptly complete such action.
    In certain types of cases (e.g., 30 CFR 75.323), MSHA has required 
that when monitoring detects a hazardous level of a substance, miners 
must be immediately withdrawn from an area until abatement action has 
been completed. Although MSHA has not proposed such action in this 
case, MSHA would like advice from the mining community on whether such 
a practice should be required in light of the evidence presented on the 
various risks posed by exposure to diesel particulate. There is good 
evidence, for example, that acute short-term increases in exposure can 
pose significant risks to miner health.
    The Agency welcomes comment on whether clarification of this 
proposed requirement is necessary in light of the fact that operators 
using more complex analytical procedures (e.g., the total carbon 
method) may not receive the results for some time period after the 
sampling has taken place.
    Posting of Sample Results. Proposed Sec. 57.5071(d)(1) would 
require that monitoring results be posted on the mine bulletin board 
within 15 days of receipt, and remain posted for 30 days. A copy of the 
results would be provided to the authorized miners' representative. 
Posting of the results would ensure that miners are kept aware of the 
hazard so they can actively participate in efforts to control dpm.
    Retention of Sample Results. Proposed Sec. 57.5071(d)(2) would 
require that records of the sampling method and the sample results 
themselves be retained by operators for five years. This is because the 
results from a monitoring program can provide insight as to the 
effectiveness of controls over time and provide a history of 
occupational exposures at the mine. MSHA would welcome comment on the 
sample retention period appropriate for the risks involved.

 Section 57.5075  Diesel Particulate Records

    Various recordkeeping requirements are set forth in provisions of 
the proposed rule. For the convenience of the mining community, these 
requirements are also listed in a table entitled ``Diesel Particulate 
Recordkeeping Requirements,'' which can be found in proposed 
Sec. 57.5075(a). Each row involves a record that must be kept. The 
section requiring the record be kept is noted, along with the retention 
time. MSHA would welcome input from the mining community as to whether 
it likes this approach or finds it duplicative or confusing.
    Location of Records. Proposed Sec. 57.5075(b)(1) would provide that 
any record which is required to be retained at the mine site may be 
retained elsewhere if it is immediately accessible from the mine site 
by electronic transmission. Compliance records need to be where an 
inspector can view them during the course of an inspection, as the 
information in the records may determine how the inspection proceeds. 
If the mine site has a fax machine or computer terminal, there is no 
reason why the records cannot be maintained elsewhere. MSHA's approach 
in this regard is consistent with Office of Management and Budget 
Circular A-130.
    MSHA encourages mine operators who store records electronically to 
provide a mechanism which will allow the continued storage and 
retrieval of records in the year 2000.
    Records Access. Proposed Sec. 57.5075(b) also covers records 
access. Consistent with the statute, upon request from an authorized 
representative of the Secretary of Labor, the Secretary of Health and 
Human Services, or from the authorized representative of miners, mine 
operators are to promptly provide access to any record listed in the 
table in this section. A miner, former miner, or, with the miner's or 
former miner's written consent, a personal representative of a miner, 
is to have access to any exposure record required to be maintained 
pursuant to Sec. 57.5071 to the extent the information pertains to the 
miner or former miner. Upon request, the operator must provide the 
first copy of such record at no cost. Whenever an operator ceases to do 
business, that operator would be required to transfer all records 
required to be maintained by this part to any successor operator.
    General Effective Date. The proposed rule provides that unless 
otherwise specified, its provisions take effect 60 days after the date 
of promulgation of the final rule. Thus, for example, the requirements 
to implement certain work practice controls (e.g., fuel type) would go 
into effect 60 days after the final rule is published.
    A number of provisions of the proposed rules contain separate 
effective dates that provide more time for technical support. For 
example, the initial concentration limit for underground metal and 
nonmetal mines would be delayed for 18 months.
    A general outline of effective dates is contained in Question and 
Answer 10 in Part I of this preamble.

V. Adequacy of Protection and Feasibility of Proposed Rule

    The Mine Act requires that in promulgating a standard, the 
Secretary, based on the best available evidence, shall attain the 
highest degree of health and safety protection for the miner with 
feasibility a consideration.

Overview

    This part begins with a summary of the pertinent legal 
requirements, followed by a general profile of the economic health and 
prospects of the metal and nonmetal mining industry.
    The discussion then turns to the proposed rule for underground 
metal and nonmetal mines. MSHA is proposing to establish a 
concentration limit for dpm, supplemented by monitoring and training 
requirements. An operator in the metal and nonmetal sector would have 
the flexibility to choose any type or combination of engineering 
controls to keep dpm levels at or below the concentration limit. In 
addition, the proposed rule would require this sector to implement 
certain work practices that help reduce dpm concentrations--practices 
similar to those already required in the underground coal mining 
industry. Miner hazard awareness training would also be required.
    This part evaluates the proposed rule for underground metal and 
nonmetal mines to ascertain if, as required by the statute, it achieves 
the highest degree of protection for underground metal and nonmetal 
miners that is feasible, both technologically and economically, for 
underground metal and nonmetal mine operators to provide. Some 
significant alternatives to the proposed rule were also reviewed in 
this regard--for example, reducing the concentration limit or the time 
permitted to come into compliance with the limit. Based on the best 
evidence available to MSHA at this time, the Agency has tentatively 
concluded that the proposed rule for the underground metal and nonmetal 
sector meets the statutory requirements. The Agency has also 
tentatively concluded that the alternatives considered are not feasible 
for underground metal and nonmetal mine operators as a whole--for 
technological reasons, economic reasons, or both.
    An Appendix to this part provides additional information about an 
approach to simulating the dpm reduction in mines that can be achieved

[[Page 58191]]

with various types of controls. Some simulations using this model were 
among the facts considered by MSHA in reaching its tentative 
conclusions about the feasible concentration limit in underground metal 
and nonmetal mines.

Pertinent Legal Requirements

    Section 101(a)(6)(A) of the Federal Mine Safety and Health Act of 
1977 (Mine Act) states that MSHA's promulgation of health standards 
must:

    * * * [A]dequately assure, on the basis of the best available 
evidence, that no miner will suffer material impairment of health or 
functional capacity even if such miner has regular exposure to the 
hazards dealt with by such standard for the period of his working 
life.

    The Mine Act also specifies that the Secretary of Labor 
(Secretary), in promulgating mandatory standards pertaining to toxic 
materials or harmful physical agents, base such standards upon:

    * * * [R]esearch, demonstrations, experiments, and such other 
information as may be appropriate. In addition to the attainment of 
the highest degree of health and safety protection for the miner, 
other considerations shall be the latest available scientific data 
in the field, the feasibility of the standards, and experience 
gained under this and other health and safety laws. Whenever 
practicable, the mandatory health or safety standard promulgated 
shall be expressed in terms of objective criteria and of the 
performance desired. [Section 101(a)(6)(A)].

    Thus, the Mine Act requires that the Secretary, in promulgating a 
standard, based on the best available evidence, attain the highest 
degree of health and safety protection for the miner with feasibility a 
consideration.
    In relation to feasibility, the legislative history of the Mine Act 
states that:

    * * * This section further provides that ``other 
considerations'' in the setting of health standards are ``the latest 
available scientific data in the field, the feasibility of the 
standards, and experience gained under this and other health and 
safety laws.'' While feasibility of the standard may be taken into 
consideration with respect to engineering controls, this factor 
should have a substantially less significant role. Thus, the 
Secretary may appropriately consider the state of the engineering 
art in industry at the time the standard is promulgated. However, as 
the circuit courts of appeal have recognized, occupational safety 
and health statutes should be viewed as ``technology-forcing'' 
legislation, and a proposed health standard should not be rejected 
as infeasible when the necessary technology looms in today's 
horizon. AFL-CIO v. Brennan, 530 F.2d 109 (1975); Society of the 
Plastics Industry v. OSHA, 509 F.2d 1301, cert. denied, 427 U.S. 992 
(1975).
    Similarly, information on the economic impact of a health 
standard which is provided to the Secretary of Labor at a hearing or 
during the public comment period, may be given weight by the 
Secretary. In adopting the language of [this section], the Committee 
wishes to emphasize that it rejects the view that cost benefit 
ratios alone may be the basis for depriving miners of the health 
protection which the law was intended to insure. S. Rep. No. 95-181, 
95th Cong., 1st Sess. 21 (1977).

    Court decisions have clarified the meaning of feasibility. The 
Supreme Court, in American Textile Manufacturers' Institute v. Donovan 
(OSHA Cotton Dust), 452 U.S. 490, 101 S. Ct. 2478 (1981), defined the 
word ``feasible'' as ``capable of being done, executed, or effected.'' 
The Court stated that a standard would not be considered economically 
feasible if an entire industry's competitive structure was threatened. 
According to the Court, the appropriate inquiry into a standard's 
economic feasibility is whether the standard is capable of being 
achieved.
    Courts do not expect hard and precise predictions from agencies 
regarding feasibility. Congress intended for the ``arbitrary and 
capricious standard'' to be applied in judicial review of MSHA 
rulemaking (S.Rep. No. 95-181, at 21.) Under this standard, MSHA need 
only base its predictions on reasonable inferences drawn from the 
existing facts. MSHA is required to produce reasonable assessment of 
the likely range of costs that a new standard will have on an industry. 
The agency must also show that a reasonable probability exists that the 
typical firm in an industry will be able to develop and install 
controls that will meet the standard. See, Citizens to Preserve Overton 
Park v. Volpe, 401 U.S. 402, 91 S. Ct. 814 (1971); Baltimore Gas & 
Electric Co. v. NRDC, 462 U.S. 87 103 S. Ct. 2246, (1983); Motor 
Vehicle Manufacturers Assn. v. State Farm Mutual Automobile Insurance 
Co., 463 U.S. 29, 103 S. Ct. 2856 (1983); International Ladies' Garment 
Workers' Union v. Donovan, 722 F.2d 795, 232 U.S. App. D.C. 309 (1983), 
cert. denied, 469 U.S. 820 (1984); Bowen v. American Hospital Assn., 
476 U.S. 610, 106 S. Ct. 2101 (1986).
    In developing a health standard, MSHA must show that modern 
technology has at least conceived some industrial strategies or devices 
that are likely to be capable of meeting the standard, and which 
industry is generally capable of adopting. United Steelworkers of 
America v. Marshall, 647 F.2d 1189, (D.C. Cir. 1980) at 1272. If only 
the most technologically advanced companies in an industry are capable 
of meeting the standard, then that would be sufficient demonstration of 
feasibility (this would be true even if only some of the operations met 
the standard for some of the time). American Iron and Steel Institute 
v. OSHA, 577 F. 2d 825, (3d Cir. 1978); see also, Industrial Union 
Department, AFL-CIO v. Hodgson, 499 F. 2d 467 (1974).
    Industry profile. The industry profile provides background 
information describing the structure and economic characteristics of 
the metal and nonmetal mining industry. This information was considered 
by MSHA as appropriate in reaching tentative conclusions about the 
economic feasibility of various regulatory alternatives. MSHA welcomes 
the submission of additional economic information about the metal and 
nonmetal mining industry, and about underground mining in particular, 
that will help it make final determinations about the economic 
feasibility of the proposed rule.
    This profile provides data on the number of mines, their size, the 
number of employees in each segment, as well as selected market 
characteristics. It does not provide information about the use of 
diesel engines in the industry; information in that regard was provided 
in the first section of part II of this preamble.
    Overall mining industry. MSHA divides the mining industry into two 
major segments based on commodity: The coal industry and the metal and 
nonmetal (M/NM) mining industry. These major industry segments are 
further divided based on type of operations (underground mines, surface 
mines, and independent mills, plants, shops, and yards). MSHA maintains 
its own data on mine type, size, and employment. MSHA also collects 
data on the number of contractors and contractor employees.
    MSHA categorizes mines as to size based on employment. Over the 
past 20 years, for rulemaking purposes, MSHA has consistently defined 
small mines to be those having fewer than 20 employees and large mines 
to be those having at least 20 employees. For this Preliminary 
Regulatory Economic Analysis and Initial Regulatory Flexibility 
Analysis, MSHA will continue to use this small mine definition. 
However, for the purposes of the Small Business Regulatory Enforcement 
Fairness Act (SBREFA) amendments to the Regulatory Flexibility Act 
(RFA), MSHA has also included SBA's definition of small (500 or fewer 
employees) in the evaluation of impacts.

[[Page 58192]]

    Table V-1 presents the number of small and large M/NM mines and the 
corresponding number of miners, excluding contractors, by major 
industry segment and mine type. Table V-1 uses three size classes: Less 
than 20 employees (MSHA's definition of small), 20 to 500 employees 
(also small by SBA's definition, but not by MSHA's), and over 500 
employees. Table V-2 presents similar MSHA data on the numbers of 
independent contractors and the corresponding numbers of employees by 
the size of the operation, based on employment. Table V-3 shows numbers 
of M/NM mines and workers by class of commodity produced.

BILLING CODE 4510-43-P

[[Page 58193]]

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[[Page 58194]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.042



[[Page 58195]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.043



Billing Code 4510-43-C

Underground M/NM Mines That Use Diesel Powered Equipment

    Impacted Mines by Size. A January 1998 count of diesel powered 
equipment performed by MSHA's Metal and Nonmetal inspectors shows that 
203 of the 261 underground M/NM mines (about 78 percent) regularly use 
diesel powered equipment. Table V-4 shows the 203 underground M/NM 
mines that use diesel powered equipment, by size and subsector.
    Based on MSHA's traditional definition of a small mine (fewer than 
20 employees), Table V-4 shows that of the 203 underground M/NM mines, 
82 mines (40 percent) are small mines and 121 mines (60 percent) are 
large mines. Small mines employ about 4 percent of the workforce (849 
employees), while large mines employ about 96 percent of the workforce 
(18,073 employees).
    Based on SBA's definition of a small mine (500 or fewer employees), 
196 mines (97 percent) are considered small and 7 mines (3 percent) are 
large. Under this definition, small mines employ 65 percent of the 
workforce (12,391 employees), while large mines employ 35 percent of 
the workforce (6,531 employees).
    Impacted Mines by Commodity. The M/NM mining industry consists of 
about 70 different commodities that can be classified into four 
commodity categories: Metals, nonmetals, stone, and sand and gravel. 
Some examples of metals mines are gold, silver, and copper, while some 
examples of nonmetals mines are potash, salt, and trona. Examples of 
stone mines are limestone, marble, and granite. Table V-4 also presents 
the numbers of underground mines operators by these four categories.

[[Page 58196]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.044



    There are no underground mine operators using diesel powered 
equipment that are classified as sand or gravel. A substantial portion 
of such small underground mine operators, however, are classified as 
stone, using either MSHA's definition or SBA's definition of a small 
mine. Large underground mine operators that use diesel powered 
equipment are predominantly classified as metal or nonmetal. By MSHA's 
definition of a large mine (those that employ 20 or more), two thirds 
(66 percent) of large mines are classified as metal or nonmetal. With 
respect to SBA's definition of a large mine (those that employ over 
500), all large underground mine operators that use diesel powered 
equipment are classified as either metal or nonmetal.

Structure of Underground M/NM Mining Subsectors

    Metal mining. Metal mining in the U.S. consists of about 25 
different commodities. Most metal commodities include only one or two 
mining operations. As is shown in Table V-3, metal mining operations 
represent 3 percent of the M/NM mines; employ 24 percent of the M/NM 
miners; and account for 33 percent of the value of M/NM mineral 
produced in the U.S. (U.S. Geological Survey, 1997, p. 6). By MSHA's 
definition, 48 percent of the metal mining operations are small. Among 
underground M/NM mines using diesel powered equipment, Table V-4 shows 
that metal mining operations represent 31 percent of mines and 39 
percent of miners, and (by MSHA's definition) 24 percent are small.
    Underground metal mining uses a few basic mining methods, such as 
stope, room and pillar, and block caving. Larger underground metal 
mines use more hydraulic drills and track-mounted haulage, whereas 
smaller underground metal mines use more hand-held pneumatic drills.
    Nonmetal Mining (Excluding Stone, Sand and Gravel). For enforcement 
and statistical purposes, MSHA separates stone mining and sand and 
gravel mining from other nonmetal mining. There are about 35 different 
nonmetal commodities, not including stone or sand and gravel. Overall 
(Table V-3), nonmetal mining operations represent 7 percent of the M/NM 
mines; employ 15 percent of the M/NM miners; and account for 35 percent 
of the value of M/NM mineral produced in the U.S. (Ibid., p. 160, 162). 
By MSHA's definition, 70 percent of the nonmetal mining operations are 
small. Among underground M/NM mines using diesel powered equipment, 
Table V-4 shows that nonmetal mining operations represent 23 percent of 
mines and 46 percent of miners, and (by MSHA's definition) 32 percent 
are small.
    Nonmetal mining uses a wide variety of underground mining methods. 
For example, potash mines use continuous miners similar to coal mining; 
oil shale uses in-situ retorting; and gilsonite uses hand-held 
pneumatic chippers. Some nonmetal commodities use kilns and dryers in 
ore processing. Others use crushers and mills similar to metal mining. 
Underground nonmetal mining operations generally use more block caving, 
room and pillar, and retreat mining methods; less hand-held equipment; 
and more electrical equipment than metal mining operations.
    Stone Mining. There are basically only 8 different stone 
commodities, of which 7 are further classified as either dimension 
stone or crushed and broken

[[Page 58197]]

stone. Overall, stone mining operations represent 33 percent of all M/
NM mines; employ 39 percent of the M/NM miners; and account for 19 
percent of the value of M/NM mineral produced in the U.S. By MSHA's 
definition, 75 percent of the stone mining operations are small. Among 
underground M/NM mines using diesel powered equipment, stone mining 
operations represent 46 percent of mines and 15 percent of miners, and 
(by MSHA's definition) 56 percent are small.
    Sand and Gravel Mining. Although 57 percent of all M/NM mines are 
sand and gravel operations, these are all surface mines. No sand and 
gravel mines will be affected by this regulation.

Economic Characteristics of the M/NM Mining Industry

    Overview. The 1996 value of all M/NM mining output was $38 billion 
(Ibid., p. 6). Metal mining, which includes metals such as aluminum, 
copper, gold, and iron, contributed $12.5 billion to this total. 
Nonmetal mining, which includes commodities such as clay, phosphate 
rock, salt, and soda ash, was valued at $13.3 million. Stone mining 
contributed $7.4 billion, and sand and gravel contributed $4.8 billion 
to this total.
    The entire M/NM mining industry is markedly diverse, not only in 
terms of the breadth of minerals but also in terms of each commodity's 
usage. For example, metals such as iron and aluminum are used to 
produce vehicles and other heavy duty equipment, as well as consumer 
goods such as household equipment and beverage cans. Other metals, such 
as uranium and titanium, have limited uses. Nonmetals like cement are 
used in construction, while salt is used in a variety of ways, 
including as a food additive and highway deicing. Soda ash, phosphate 
rock, and potash also have various commercial uses. Stone and sand and 
gravel are used in numerous industries including the construction of 
roads and buildings.
    A detailed financial picture of the M/NM mining industry is 
difficult to develop because most mines either are privately held 
corporations or sole proprietorships or they are subsidiaries of 
publicly owned companies. Privately held corporations and sole 
proprietorships do not make their financial data available to the 
public; parent companies are not required to separate financial data 
for subsidiaries in their reports to the Securities and Exchange 
Commission. As a result, financial data are available for only a few M/
NM companies, and these data are not representative of the entire 
industry. Each commodity has a unique market demand structure. The 
following discussion focuses on market forces on a few specific 
commodities of the M/NM industry.
    Metal Mining. Historically, the value of metals production has 
exhibited considerable instability. In the early 1980's, excess 
capacity, large inventories, and weak demand depressed the 
international market for metals, while the strong dollar placed U.S. 
producers at a competitive disadvantage with foreign producers. 
Reacting to this, many metal mining companies reduced work forces, 
eliminated marginal facilities, sold non-core businesses, and 
restructured. At the same time, new mining technologies were developed, 
and wage increases were restrained. As a result, the metal mining firms 
now operating are more efficient and have lower break-even prices than 
those that operated in the 1970's.
    Variations in the prices for iron and alloying metals, such as 
nickel, aluminum, molybdenum, vanadium, platinum, and lead, coincide 
closely with fluctuations in the market for durable goods, such as 
vehicles and heavy duty equipment. As a result, the market for these 
metals is cyclical in nature and is impacted directly by changes in 
aggregate demand and the economy in general. Both nickel and aluminum 
have experienced strong price fluctuations over the past few years. 
With the U.S. and world economies improving, however, demand for such 
alloys is improving, and prices have begun to recover. It must be noted 
that primary production of aluminum will continue to be impacted by the 
push to recycle.
    The U.S. market for copper and precious metals, such as gold and 
silver, is uncertain, which makes consistent production growth in such 
areas difficult. U.S. gold production in 1996 was estimated at slightly 
above 1995 levels, which maintains the U.S. position as the world's 
second largest gold producing nation, after South Africa. U.S. silver 
production in 1996 increased slightly from 1995 levels to equal the 
highest production since 1992. U.S. copper production in 1996 continued 
its modest upward trend, rising to 1.9 million metric tons (Ibid, p. 
52).
    Overall, the 1996 production from all metal mining is estimated to 
decrease by about 10 percent from 1995 levels; 1996 estimates put 
capacity utilization at 84 percent (Ibid., p. 6). MSHA expects that the 
net result for the metal mining industry may be reduced demand but 
sustained prices.
    Nonmetal Mining. Major commodities in the nonmetal category include 
salt, clay, phosphate rock, and soda ash. Market demand for these 
products tends not to vary greatly with fluctuations in aggregate 
demand. Stone is the leading revenue generator. The U.S. is the largest 
producer of soda ash and salt. In 1996, the U.S. produced 10.1 million 
metric tons of soda ash, valued at $778 million, and 40.1 million 
metric tons of salt, valued at $930 million (Ibid., p. 143). Soda ash 
is used in the production of glass, soap, detergents, paper, and food. 
Salt is used in highway deicing, food production, feedstock, and the 
chemical industry. Phosphate rock is used primarily to manufacture 
fertilizer. Approximately 42.5 million metric tons of phosphate rock, 
valued at $900 million, was produced in the U.S. in 1996 (Ibid., p. 
124). The remaining nonmetal commodities, which include boron 
fluorspar, oil shale, and other minerals, are typically produced by a 
small number of mining operations.
    Stone production includes granite, limestone, marble, slate, and 
other forms of crushed and broken or dimension stone. Sand and gravel 
products and stone products, including cement, have a cyclical demand 
structure. As a recession intensifies, demand for these products 
sharply decreases. Demand for stone, particularly cement, is expected 
to grow by as much as 3.0 percent, and demand for sand and gravel is 
expected to grow by as much as 1.2 percent (Ibid., p. 145).
    Overall, the 1996 production from nonmetal mining was estimated to 
increase by 4.5 percent from 1995 levels; 1996 estimates put capacity 
utilization for stone and earth minerals at about 91 percent (Ibid., p. 
6). The net result for the nonmetal mining industry may be higher 
demand for stone and various other commodities, as well as increased 
prices.
    Adequacy of Miner Protection Provided by Proposed Rule in 
Underground Metal and Nonmetal Mines. In evaluating the proposed rule, 
it should be remembered that MSHA has measured dpm concentrations in 
this sector as high as 5,570DPM g/m3--a 
mean of 830DPM g/m3. See Table III-1 and 
Figure III-2 in part III of the preamble. As discussed in detail in 
part III of the preamble, these concentrations place underground metal 
and nonmetal miners at significant risk of material impairment of their 
health, and it does not appear there is any lower boundary to the risk. 
Accordingly, in accordance with the statute, the Agency has to set a 
standard which reduces these concentrations as much as is both

[[Page 58198]]

technologically and economically feasible for this sector as a whole.
    In this sector, the Agency is proposing a concentration limit on 
dpm. The proposed concentration limit would be expressed in terms of a 
restriction on the amount of total carbon because of the measurement 
system which MSHA proposes to utilize. The proposed limit is 
160TC g/m3--the equivalent of 
200DPM g/m3. This permits concentrations 
of diesel particulate matter in this sector above those which MSHA 
hopes to achieve in the underground coal sector with the use of 95% 
particulate filter technology, as described earlier in this part.
    Accordingly, the Agency has explored some significant alternatives 
to the proposal to ascertain if additional protection can feasibly be 
provided in this sector.
    (1) Establish a lower concentration limit for underground metal/
nonmetal mines. Based on the Agency's risk assessment, a lower 
concentration limit would provide more miner protection. The Agency has 
tentatively concluded, however, that at this time it may not be 
feasible for the underground metal and nonmetal sector to reach a 
concentration limit below that proposed. The evidence on this point is 
somewhat mixed, and comments and specific examples to illustrate them 
would be most welcome.
    Technological feasibility of lower limit. In evaluating whether a 
lower concentration limit is feasible for this sector, MSHA has 
considered some examples of real-world situations. As described in more 
detail in the Appendix to this part, MSHA has developed a simulator or 
model to estimate the ambient dpm that would remain in a mine section 
after the application of a particular combination of control 
technologies. The model uses a spreadsheet template into which data can 
be entered; the formulae in the spreadsheet (described in the Appendix) 
instantly make the calculations and display the results. This model is 
hereinafter referred to as ``The Estimator''.
    The examples presented here are based on data from several 
underground metal and nonmetal mines. The first three have been written 
up in detail and placed into MSHA's record, with actual mine 
identifiers removed; the fourth is based on information supplied by 
inspectors, and all available data is presented here. MSHA had picked 
these mines because the Agency originally thought the conditions there 
were such that these mines would have great difficulty in controlling 
dpm concentrations, but this turned out to not always be the case.

           Figure V-1.--Work Place Emissions Control Estimator
                [Mine Name: Underground Nonmetal Mine A]
------------------------------------------------------------------------
                                                        Column A
------------------------------------------------------------------------
1. MEASURED OR ESTIMATED IN MINE DP EXPOSURE   760 g/m3
 (g/m3).
2. VEHICLE EMISSION DATA
    EMISSIONS OUTPUT (gm/hp-hr)
        VEHICLE 1  INDIRECT INJECTION 0.3-0.5  0.3 gm/hp-hr
         gm/hp-hr  FEL.
        VEHICLE 2  OLD DIRECT INJECTION 0.5-   0.3 gm/hp-hr
         0.9 gm/hp-hr  SCALER.
        VEHICLE 3  NEW DIRECT INJECTION 0.1-   0.3 gm/hp-hr
         0.4 gm/hp-hr  DRILL.
        VEHICLE 4  BOLTER....................  0.7 gm/hp-hr
    VEHICLE OPERATING TIME (hours)
        VEHICLE 1  FEL.......................  6 hours
        VEHICLE 2  SCALER....................  6 hours
        VEHICLE 3  DRILL.....................  6 hours
        VEHICLE 4  BOLTER....................  6 hours
    VEHICLE HORSEPOWER (hp)
        VEHICLE 1  3 @ 480  FEL..............  1440 hp
        VEHICLE 2  2 @ 250  SCALER...........  500 hp
        VEHICLE 3  2 @ 250  DRILL............  500 hp
        VEHICLE 4  2 @ 82  BOLTER............  164 hp
    SHIFT DURATION (hours)...................  8 hours
    AVERAGE TOTAL SHIFT PARTICULATE OUTPUT     0.13 gm/hp-hr
     (gm).
3. MINE VENTILATION DATA
        FULL SHIFT INTAKE DIESEL PARTICULATE   50 g/m3
         CONCENTRATION.
        SECTION AIR QUANTITY.................  209000 cfm
        AIRFLOW PER HORSEPOWER...............  80 cfm/hp
4. CALCULATED SWA DP CONCENTRATION WITHOUT
 CONTROLS
5. ADJUSTMENTS FOR EMISSION CONTROL
 TECHNOLOGY
        ADJUSTED SECTION AIR QUANTITY........  330000 cfm
        VENTILATION FACTOR (INITIAL CFM/FINAL  0.63
         CFM).
        AIRFLOW PER HORSEPOWER...............  127 cfm/hp
    OXIDATION CATALYTIC CONVERTER REDUCTION
     (%)
        VEHICLE 1............................  0%
        VEHICLE 2  IF USED ENTER 0-20%.......  0%
        VEHICLE 3............................  0%
        VEHICLE 4............................  0%
    NEW ENGINE EMISSION RATE (gm/hp-hr)
        VEHICLE 1............................  0.1 gm/hp-hr
        VEHICLE 2  ENTER NEW ENGINE EMISSION   0.1 gm/hp-hr
         (gm/hp-hr).
        VEHICLE 3............................  0.1 gm/hp-hr
        VEHICLE 4............................  0.1 gm/hp-hr
    AFTERFILTER OR CAB EFFICIENCY (%)
        VEHICLE 1............................  0%
        VEHICLE 2  USE 65-95% FOR              0%
         AFTERFILTERS.
        VEHICLE 3  USE 50-80% FOR CABS.......  0%
        VEHICLE 4............................  0%

[[Page 58199]]

6. ESTIMATED FULL SHIFT DP CONCENTRATION.....  194 g/m3
------------------------------------------------------------------------

    The mining community is encouraged to obtain a copy of the 
Estimator from MSHA and run simulations of its own in individual mines. 
MSHA would welcome having such examples submitted for the record as 
part of comments submitted on this proposed rulemaking.
    The first example, summarized in Figure V-1, involves a section of 
an underground salt mine. This section has 9 diesel engines, most of 
them very heavy duty: three front end loaders of 480 hp each, 2 scalers 
and 2 drills at 250hp each, and an 82 hp bolter.
    Entered in section 1 of the figure is the measured level of dpm, 
760DPM g/m3. This measurement reflects 
the fact that the equipment was all equipped with oxidation catalytic 
converters; otherwise, the measurement would have been on the order of 
20% higher.
    Entered in sections 2 and 3 is information about the engines, 
operating cycle, horsepower, shift duration, intake dpm concentration, 
and ventilation currently used in the mine. The entries for engines of 
a similar type and horsepower were combined. The intake concentration 
is dpm coming from outside the section, and in the case of these 
examples has been estimated to be about 50DPM g/
m3. This information is retained by the Estimator as a 
baseline against which to compare a particular combination of proposed 
controls.
    Sections 2 and 3 of the Estimator also calculate two ratios -- the 
average total shift particulate output, and the airflow per 
horsepower--that provide useful insights into what controls might be 
available. For example, in this case, an airflow of 80 cfm/hp is below 
recommended levels, suggesting that a ventilation increase should be 
part of the solution to the high dpm concentrations.
    The controls to be modeled are entered into section 5 of the 
Estimator. In this example, the ventilation is increased enough to 
increase the airflow per horsepower to 127 cfm/hp. Oxidation catalytic 
converters are already on the equipment, so nothing can be added in 
that regard. In the example, all 9 engines (grouped into 4 lines by 
combining those with similar horsepower, as originally entered) would 
be replaced by newer engines with lower emission rates. No filters or 
cabs would be used. The calculated result is an ambient dpm 
concentration of 194DPM g/m3.
    This mine section could actually lower its dpm concentrations more 
using different combinations of controls. For example, using 80% 
filters on the three front-end loaders instead of new engines would, 
according to the Estimator, result in an ambient dpm level of 
161DPM g/m3. If both the 80% filters and 
new engines were used, the ambient dpm level would be 128DPM 
g/m3. Keep in mind that of the amount that remains, 
50DPM g/m3 comes from the intake to the 
section. The next two studies are of an underground limestone mine that 
operates in two shifts: one for production, and one for support.

           Figure V-2.--Work Place Emissions Control Estimator
        [Mine Name: Underground Nonmetal Mine B Production Shift]
------------------------------------------------------------------------
                                                          Column A
------------------------------------------------------------------------
1. MEASURED OR ESTIMATED IN MINE DP EXPOSURE       330 g/m3
 (g/m3.
2. VEHICLE EMISSION DATA
    EMISSIONS OUTPUT (gm/hp-hr)
        VEHICLE 1  INDIRECT INJECTION 0.3-0.5 gm/  0.1 gm/hp-hr
         hp-hr  FEL.
        VEHICLE 2  OLD DIRECT INJECTION 0.5-0.9    0.2 gm/hp-hr
         gm/hp-hr  Truck 1.
        VEHICLE 3  NEW DIRECT INJECTION 0.1-0.4    0.1 gm/hp-hr
         gm/hp-hr  Truck 2.
        VEHICLE 4  ..............................  0.0 gm/hp-hr
    VEHICLE OPERATING TIME (hours)
        VEHICLE 1  FEL...........................  9 hours
        VEHICLE 2  Truck 1.......................  9 hours
        VEHICLE 3  Truck 2.......................  9 hours
        VEHICLE 4  ..............................  0 hours
    VEHICLE HORSEPOWER (hp)
        VEHICLE 1  FEL...........................  315 hp
        VEHICLE 2  Truck 1.......................  250 hp
        VEHICLE 3  Truck 2.......................  330 hp
        VEHICLE 4  ..............................  0 hp
    SHIFT DURATION (hours).......................  10 hours
    AVERAGE TOTAL SHIFT PARTICULATE OUTPUT (gm)..  0.09 gm/hp-hr
3. MINE VENTILATION DATA
        FULL SHIFT INTAKE DIESEL PARTICULATE       50 g/m3
         CONCENTRATION.
        SECTION AIR QUANTITY.....................  155000 cfm
        AIRFLOW PER HORSEPOWER...................  173 cfm/hp
4. CALCULATED SWA DP CONCENTRATION WITHOUT
 CONTROLS
5. ADJUSTMENTS FOR EMISSION CONTROL TECHNOLOGY

[[Page 58200]]

        ADJUSTED SECTION AIR QUANTITY............  155000 cfm
        VENTILATION FACTOR (INITIAL CFM/FINAL      1.00
         CFM).
        AIRFLOW PER HORSEPOWER...................  173 cfm/hp
    OXIDATION CATALYTIC CONVERTER REDUCTION (%)
        VEHICLE 1  ..............................  0%
        VEHICLE 2  IF USED ENTER 0-20%...........  0%
        VEHICLE 3  ..............................  0%
        VEHICLE 4  ..............................  0%
    NEW ENGINE EMISSION RATE (gm/hp-hr)
        VEHICLE 1  ..............................  0.1 gm/hp-hr
        VEHICLE 2  ENTER NEW ENGINE EMISSION (gm/  0.2 gm/hp-hr
         hp-hr).
        VEHICLE 3  ..............................  0.1 gm/hp-hr
        VEHICLE 4  ..............................  0.0 gm/hp-hr
    AFTERFILTER OR CAB EFFICIENCY (%)
        VEHICLE 1  CABS..........................  70%
        VEHICLE 2  USE 65-95% FOR AFTERFILTERS...  70%
        VEHICLE 3  USE 50-80% FOR CABS...........  70%
        VEHICLE 4  ..............................  0%
6. ESTIMATED FULL SHIFT DP CONCENTRATION.........  134 g/m3
------------------------------------------------------------------------


           Figure V-3.--Work Place Emissions Control Estimator
         [Mine Name: Underground Nonmetal Mine B Support Shift]
------------------------------------------------------------------------
                                                        Column A
------------------------------------------------------------------------
1. MEASURED OR ESTIMATED IN MINE DP EXPOSURE   600 g/m3
 (g/m3).
2. VEHICLE EMISSION DATA
    EMISSIONS OUTPUT (gm/hp-hr)
        VEHICLE 1  INDIRECT INJECTION 0.3-0.5  0.3 gm/hp-hr
         gm/hp-hr  Drill.
        VEHICLE 2  OLD DIRECT INJECTION 0.5-   0.6 gm/hp-hr
         0.9 gm/hp-hr  Bolter.
        VEHICLE 3  NEW DIRECT INJECTION 0.1-   0.7 gm/hp-hr
         0.4 gm/hp-hr  Scaler.
        VEHICLE 4  Anfo......................  0.7 gm/hp-hr
    VEHICLE OPERATING TIME (hours)
        VEHICLE 1  Drill.....................  8 hours
        VEHICLE 2  Bolter....................  4 hours
        VEHICLE 3  Scaler....................  8 hours
        VEHICLE 4  Anfo......................  4 hours
    VEHICLE HORSEPOWER (hp)
        VEHICLE 1  Drill.....................  116 hp
        VEHICLE 2  Bolter....................  193 hp
        VEHICLE 3  Scaler....................  119 hp
        VEHICLE 4  Anfo......................  86 hp
    SHIFT DURATION (hours)...................  8 hours
    AVERAGE TOTAL SHIFT PARTICULATE OUTPUT     0.39 gm/hp-hr
     (gm).
3. MINE VENTILATION DATA
        FULL SHIFT INTAKE DIESEL PARTICULATE   50 g/m3
         CONCENTRATION.
        SECTION AIR QUANTITY.................  155000 cfm
        AIRFLOW PER HORSEPOWER...............  302 cfm/hp
4. CALCULATED SWA DP CONCENTRATION WITHOUT
 CONTROLS
5. ADJUSTMENTS FOR EMISSION CONTROL
 TECHNOLOGY
        ADJUSTED SECTION AIR QUANTITY........  155000 cfm
        VENTILATION FACTOR (INITIAL CFM/FINAL  1.00
         CFM).
        AIRFLOW PER HORSEPOWER...............  302 cfm/hp
    OXIDATION CATALYTIC CONVERTER REDUCTION
     (%)
        VEHICLE 1  ..........................  0%
        VEHICLE 2  IF USED ENTER 0-20%.......  0%
        VEHICLE 3  ..........................  0%
        VEHICLE 4  ..........................  0%
    NEW ENGINE EMISSION RATE (gm/hp-hr)
        VEHICLE 1  ..........................  0.3 gm/hp-hr
        VEHICLE 2  ENTER NEW ENGINE EMISSION   0.6 gm/hp-hr
         (gm/hp-hr).
        VEHICLE 3  ..........................  0.7 gm/hp-hr
        VEHICLE 4  ..........................  0.7 gm/hp-hr
    AFTERFILTER OR CAB EFFICIENCY (%)
        VEHICLE 1  ..........................  80%

[[Page 58201]]

        VEHICLE 2  USE 65-95% FOR              80%
         AFTERFILTERS.
        VEHICLE 3  USE 50-80% FOR CABS.......  80%
        VEHICLE 4  ..........................  80%
6. ESTIMATED FULL SHIFT DP CONCENTRATION.....  160 g/m3
------------------------------------------------------------------------

    The two shifts use completely different types of diesel-powered 
equipment.
    Figure V-2 summarizes the study of the production shift, and Figure 
V-3 summarizes the study of the support shift.
    The production shift already has low-emission engines on the three 
pieces of equipment present--a front-end loader and two trucks, as well 
as oxidation catalytic converters on each engine.
    Its ventilation provides 173 cfm/hp. Accordingly, the measured dpm 
for this shift is only about 330DPM g/m3 
With the addition of a cab on each unit providing roughly 70% 
effectiveness (see part II of this preamble on cab effectiveness), the 
ambient concentration (to which the equipment operator would be 
exposed) can be reduced to 134DPM g/m3.
    In the case of the support shift, the engines do emit particulate 
at a high rate; but they all are low horsepower engines, and all have 
oxidation catalytic converters. The ventilation is the same as on the 
production shift. Hence the measured dpm is on the order of 
600DPM g/m3. In the example shown, 80% 
filtration of each piece of equipment would bring the concentration 
down to 160TC g/m3. If 95% filters were 
used, the Estimator indicates this concentration could be reduced to 
77DPM g/m3. Since 50DPM 
g/m3 of this is the estimated intake into the 
section, the filters and controls already in place appear to be capable 
of eliminating almost all dpm generated within the section itself.

          FIGURE V-4.--WORK PLACE EMISSIONS CONTROLS ESTIMATOR
                   [Mine Name: Underground Gold Mine]
------------------------------------------------------------------------
                                                   Column A
------------------------------------------------------------------------
1. MEASURED OR ESTIMATED IN MINE DP
 EXPOSURE (ug/m3)...................                          1000 us/m3
2. VEHICLE EMISSION DATA
    EMISSIONS OUTPUT (gm/hp-hr)
        VEHICLE 1  INDIRECT
         INJECTION 0.3-0.5..........
          gm/hp-hr    FEL...........                        0.7 gm/hp-hr
        VEHICLE 2  OLD DIRECT
         INJECTION 0.5-0.9..........
          gm/hp-hr    Scaler........                        0.7 gm/hp-hr
        VEHICLE 3  NEW DIRECT
         INJECTION..................
          0.1-0.4 gm/hp-hr    Drill.                        0.7 gm/hp-hr
        VEHICLE 4...................                        0.0 gm/hp-hr
    VEHICLE OPERATING TIME (hours)
        VEHICLE 1     FEL...........                             6 hours
        VEHICLE 2     Scaler........                             6 hours
        VEHICLE 3     Drill.........                             6 hours
        VEHICLE 4...................                             0 hours
    VEHICLE HORSEPOWER (hp)
        VEHICLE 1     FEL...........                              315 hp
        VEHICLE 2     Scaler........                              250 hp
        VEHICLE 3     Drill.........                              330 hp
        VEHICLE 4...................                                0 hp
    SHIFT DURATION (hours)..........                             8 hours
    AVERAGE TOTAL SHIFT PARTICULATE
     OUTPUT (gm)....................                       0.44 gm/hr-hr
3. MINE VENTILATION DATA
        FULL SHIFT INTAKE DIESEL
         PARTICULATE CONCENTRATION..                            50 ug/m3
        SECTION AIR QUALITY.........                          185000 cfm
        AIRFLOW PER HORSEPOWER......                          207 cfm/hp
4. CALCULATED SWA DP CONCENTRATION
 WITH-
  OUT CONTROLS
5. ADJUSTMENTS FOR EMISSION CONTROL
 TECHNOLOGY
        ADJUSTED SECTION AIR
         QUANTITY...................                          185000 cfm
        VENTILATION FACTOR (INITIAL
         CFM/FINAL CFM).............                                1.00
        AIRFLOW PER HORSEPOWER......                          207 cfm/hp
    OXIDATION CATALYTIC CONVERTER
     REDUCTION (%)
        VEHICLE 1  .................                                 20%
        VEHICLE 2     IF USED ENTER
         0-20%......................                                 20%
        VEHICLE 3  .................                                 20%
        VEHICLE 4  .................                                  0%
    NEW ENGINE EMISSION RATE (gm/hp-
     hr)
        VEHICLE 1...................                        0.7 gm/hp-hr
        VEHICLE 2  ENTER NEW ENGINE
         EMISSION (gm/hp-hr)........                        0.1 gm/hp-hr
        VEHICLE 3...................                        0.1 gm/hp-hr
        VEHICLE 4...................                        0.0 gm/hp-hr

[[Page 58202]]

    AFTERFILTER OR CAB EFFICIENCY
     (%)
        VEHICLE 1  FILTER...........                                 95%
        VEHICLE 2  USE 65-95% FOR...
          AFTERFILTERS..............                                  0%
        VEHICLE 3  USE 50-80% FOR
         CABS.......................                                  0%
        VEHICLE 4...................                                  0%
6. ESTIMATED FULL SHIFT DP
 CONCENTRATION......................                           134 ug/m3
------------------------------------------------------------------------

    The final study, summarized in Figure V-4, involves a multi-level 
underground gold mine. Each level had one production unit on a separate 
split of ventilation air. The three engines are large and have a high 
emission rate, and have no oxidation catalytic converters. The 
ventilation produces over 200 cfm/hp. In this case, no initial 
measurement was taken; instead, an initial concentration of 
1000DPM g/m3 was estimated by taking a 
percentage of the respirable dust concentration (a method discussed in 
the Appendix).
    By replacing all of the current engines with low-emission engines 
equipped with catalytic converters, the Estimator calculates that the 
ambient concentration can be reduced to 159DPM g/
m3, of which 50DPM g/m3 again 
constitutes the estimated intake to the section. Further reductions 
could be achieved by adding a filter to the front-end loader and/or 
drill.
    These studies seem to suggest that using a combination of available 
technologies, even mine sections with significant ambient intake and 
standard ventilation parameters can reduce dpm concentrations well 
below the proposed concentration limit.
    Economic feasibility of lower concentration limit. MSHA's cost 
estimates for the proposed concentration limit of 200DPM 
g/m3 for underground metal and nonmetal mines comes 
to about $19.2 million a year. (See Table I-1, in the response to 
Question 5 in part I of the preamble). For an average underground metal 
and nonmetal dieselized mine that uses diesel powered equipment, this 
amounts to about $94,600 per year to comply with the proposed 
concentration limits.
    The assumptions used in preparing the cost estimates are discussed 
in detail in the Agency's PREA, and are based on a January 1998 count 
of diesel powered equipment that regularly operates in the underground 
metal and nonmetal mines. The count was performed by MSHA's metal and 
nonmetal inspectors. The assumptions can be summarized as follows: 
engineering controls, such as low emission engines, ceramic filters, 
oxidation catalytic converters, and cabs would be needed on certain 
diesel powered equipment. Most of the engineering controls would be 
needed on diesel powered equipment used for production, while a small 
amount of diesel powered equipment that is used for support purposes 
would need engineering controls. In addition to these controls, MSHA 
assumed that some underground metal and nonmetal mines would need to 
make ventilation changes in order to meet the proposed concentration 
limits.
    While the four studies presented here suggest it might be 
economically feasible for some mines in this sector to reduce dpm 
concentrations below the concentration level proposed, the Agency is 
reluctant to conclude on the basis of the examples that most 
underground metal and nonmetal operators would find it economically 
feasible to reduce concentrations below the proposed limit of 
160TC g/m3 (200DPM 
g/m3). The Agency welcomes additional examples and 
information it can use to make a better assessment of the costs 
operators would incur to reduce dpm to various concentration limits, as 
well as other considerations relevant to economic feasibility.
    (2) Shorten the phase-in time to reach the final concentration 
limit in underground metal/nonmetal mines. Under the proposed rule, 
there is a phase-in period for a dpm concentration limit (see proposed 
Sec. 57.5060). Operators would have 18 months to reduce dpm 
concentrations in areas of the mine where miners work or travel to 
400TC g/m3 (500DPM 
g/m3), and up to 60 months in all to reduce dpm 
concentrations in those areas to 160TC g/
m3 (200DPM g/m3). MSHA 
established this phase-in period because it has tentatively concluded 
that it would be infeasible for the underground metal and nonmetal 
mining industry as a whole to implement the requirements sooner.
    With respect to technological feasibility, MSHA notes that many of 
these mines face unique difficulties in using ventilation to lower dpm 
concentrations; and high efficiency particulate filters may not yet be 
commercially available for certain types or sizes of engines and 
equipment used in this sector. The proposed rule includes a provision 
for a special time extension to deal with unique situations. Shortening 
the normal time frame available to this sector could create a situation 
where special exemptions would become the norm.
    The costs of the proposed rule would also increase significantly 
were the final concentration limit to become effective sooner. As 
explained in the Agency's PREA, a substantial portion of the costs to 
implement these provisions were calculated using a 5-year discounting 
process to reflect the phase-in schedule. Speeding implementation would 
significantly impact costs.
    Accordingly, MSHA has tentatively concluded that, for the 
underground metal and nonmetal sector as a whole, an accelerated 
approach may not be feasible.
    (3) In lieu of a concentration limit, require high efficiency 
filters on certain types of equipment. In the underground coal sector, 
MSHA has proposed requiring high efficiency filters on all but light-
duty equipment. This appears to be a very effective and feasible way of 
reducing dpm concentrations in that sector. Accordingly, MSHA 
considered requiring a similar approach in underground metal and 
nonmetal mines.
    MSHA estimates that to require 95% efficient filters on all diesel 
engines in underground metal and nonmetal mines after 30 months would 
cost about $41 million a year. On the other hand, to require that only 
heavy duty equipment use 95% filters after 30 months would cost about 
$20 million a year. (``Heavy duty'' equipment here means equipment that 
moves rock or ore; for costing purposes, MSHA assumed this included 
production equipment and about five percent of support equipment, which 
is about 46% of the diesel equipment in underground metal and nonmetal 
mines).

[[Page 58203]]

    The estimated costs of complying with the proposed concentration 
limits and the other provisions of the proposed rule are about $19.2 
million a year.
    This option is not the equivalent of what is being proposed for 
underground coal mines. The underground metal and nonmetal equipment 
that would be left unfiltered pursuant to this option may in some 
cases, have larger horsepower engines than the equipment that would be 
left unfiltered pursuant to the proposed rule for underground coal--and 
there are more pieces of equipment per mine in the underground metal 
and nonmetal sector (see Table II-1 in part II of this preamble).
    Moreover, under the statute, MSHA must take the approach that 
provides miners with the greatest protection feasible. This option 
would be less protective than a concentration limit in this sector. 
Under the option, the only control in underground metal and nonmetal 
mines would be filters on heavy-duty equipment; by contrast, the 
controls MSHA has estimated will be necessary to meet the proposed 
concentration limit are more stringent--all production equipment will 
need an oxidation catalytic convertor for example, and 85% of 
production equipment will also need a new engine.
    Moreover, the distribution of equipment and miners in underground 
metal and nonmetal mine areas means that the protection received under 
this approach--in which only 46% (i.e., the heavy duty equipment) of 
the equipment is filtered, and no other controls required--would likely 
be very uneven. Some miners might be reasonably well protected, but 
many others would not.
    There are two other factors that mitigate against such an approach 
in underground metal and nonmetal mines.
    First, it is not clear this approach is technologically feasible. 
The only filters that are currently available that can produce 95% 
efficiency in removing particulates are paper filters. Some of the 
heavy-duty engines are very large, and it may take some time before 
commercially available designs for filtration of this efficiency will 
be available to fit all types and sizes of heavy duty equipment--and 
work effectively without hampering equipment performance. That is why 
in determining the role filtration might play in this sector, the 
Agency assumed that replaceable ceramic filters would be used. At this 
time, such filters are capable of 60-85% efficiency. It is possible, of 
course, that once a market develops, the manufacturers of such filters 
might be able to produce a more efficient filter. MSHA solicits 
information about any such pending developments.
    Second, it would appear that in many cases, a new engine and/or cab 
might be a more effective solution to a localized dpm concentration in 
an underground metal and nonmetal mine than a filter--and perhaps less 
expensive for equipment of this size. One of the advantages of a 
concentration limit is the flexibility it provides.
    MSHA has not yet given detailed consideration to requiring all 
underground metal and nonmetal operators to utilize an oxidation 
catalytic converter (OCC)--in combination with a concentration limit--
but intends to do so. The studies discussed above, and information from 
MSHA's workshops, suggests that OCCs are already widely utilized in 
this sector, and can reduce dpm emissions as much as 20%. MSHA assumes 
that this is the first control to which most operators would turn if a 
concentration limit were established. Accordingly, the Agency welcomes 
comment on whether it would be feasible and appropriate to simply 
require underground metal and nonmetal mining companies to install and 
maintain OCCs on all diesel engines.
    Feasibility of proposed rule for underground metal and nonmetal 
mining sector. The Agency has carefully considered both the 
technological and economic feasibility of the proposed rule for the 
underground metal and nonmetal mining sector as a whole.
    There are two separate issues with respect to technological 
feasibility--(a) the existence of technology that can accurately and 
reliably measure dpm concentration levels in all types of underground 
metal and nonmetal mines; and (b) the existence of control mechanisms 
that can bring dpm concentrations down to the proposed limit in all 
types of underground metal and nonmetal mines.
    Measurement technology. Part II of this preamble contains a 
detailed discussion of the measurement method which MSHA is proposing 
to use in this sector, including the evidence MSHA examined in making 
its determination that this approach provides an accurate and reliable 
way to measure dpm concentration levels in all types of underground 
metal and nonmetal mines. Briefly, the method involves the use of a 
respirable dust sampler to collect particles on a filter, which is then 
analyzed using a method to detect total carbon validated by the 
National Institute for Occupational Safety and Health for that purpose. 
MSHA has concluded that total carbon, is a valid surrogate for dpm in 
this sector. In fact, to make the concentration limit on dpm easier to 
use in practice, MSHA is proposing to express that limit in terms of 
total carbon so that the measurement results can be directly compared 
with the standard's requirements.
    As further explained in part IV, MSHA recognizes that any 
measurement system has an inherent level of uncertainty. As is its 
practice with other compliance determinations based on measurement, 
MSHA would not issue a citation that an underground metal or nonmetal 
mine has violated the concentration limit unless the measurement 
exceeds the limit (interim or final) by an amount adequate to ensure a 
95% confidence level. While MSHA has not at this time reached a 
determination of the amount that it deems appropriate to add to the 
measured concentration to establish such a confidence level, it could 
be on the order of 11-20% (see part II discussion of measurement for 
details).
    Control technology. The availability of control technology to 
enable operators to reduce their existing dpm concentrations to the 
proposed concentration level was discussed earlier in this part [See 
(1) Establish a lower concentration limit for underground metal/
nonmetal mines'']. In fact, these studies suggest it is technologically 
feasible for operators in this sector to reduce their dpm 
concentrations to an even lower concentration limit. MSHA's publication 
``Practical Ways to Reduce Exposure to Diesel Exhaust in Mining--a 
Toolbox'' summarizes information about the mining community's 
experience to date with various controls. A copy of this publication is 
appended at the end of this document.
    Although the agency has reached this conclusion, and moreover knows 
of no mine that cannot accomplish the required reductions in the 
permitted time, it has nevertheless proposed that any underground metal 
or nonmetal mine may have up to an additional two years to install the 
required controls should it find that there are unforseen technological 
barriers to timely completion. A detailed discussion of the 
requirements for obtaining approval for such an extension of time to 
comply is provided in part IV of the preamble. The Agency would 
particularly welcome comments illustrating situations which warrant 
further attention in this regard.
    Economic Feasibility. MSHA estimates that the proposed rule would 
cost the underground metal and nonmetal sector about $19.2 million a 
year even with the extended phase-in time. The costs per underground

[[Page 58204]]

dieselized metal or nonmetal mine are estimated to be about $94,600 
annually.
    As explained in the PREA, most ($19.2 million) of the anticipated 
yearly costs would be investments in equipment to meet the interim and 
final concentration limits. While operators have complete flexibility 
as to what controls to use to meet the concentration limits, the Agency 
based its cost estimates on the assumption that operators will 
ultimately need the following to get to the final concentration limit: 
(a) all production equipment will need an oxidation catalytic 
converter; (b) about 38% of all equipment (production and support) will 
need a new engine; (c) about 8% of all equipment will need an 
environmentally conditioned cab; (d) about 34% of all equipment will 
need a 60-90% replaceable ceramic filter; and (e) 61% of all mines will 
need some ventilation improvement (16% fan and motor, 45% just motor). 
The assumptions are based on a January 1998 count of diesel powered 
equipment that regularly operates in the underground metal and nonmetal 
mines. The count was performed by MSHA's metal and nonmetal inspectors. 
This is a conservative estimate; as noted in discussing the possibility 
of having a lower concentration limit, it does not reflect the 
possibility that some mines may now be already cleaning up their fleet 
as they turn over their existing inventory. The cost estimates do 
reflect some facts noted in part II of this preamble: (a) unlike the 
coal sector, a large portion of underground metal and nonmetal mines 
are dieselized; (b) each mine has on average more diesel engines than 
in the coal sector; and (c) the engines used in these mines are more 
varied and heavier on average than those used in the coal sector. In 
addition to the costs to comply with the proposed concentration limit, 
the costs estimated for this sector include costs for implementing work 
practice controls that are similar to those already in effect in the 
underground coal sector.
    The Agency is taking a number of steps to mitigate the impact of 
the rule for the underground metal and nonmetal sector, particularly on 
the smallest mines in this sector. These are described in detail in the 
Agency's Initial Regulatory Flexibility Analysis, which the Agency is 
required to prepare under the Regulatory Flexibility Act in connection 
with the impact of the rule on small entities. (The regulatory 
flexibility analysis can be found in part VI of this preamble, or 
packaged with the Agency's PREA.)
    After a careful review of the information about this sector 
available from the industry economic profile, and the other obligations 
of this sector under the Mine Act, MSHA has tentatively concluded that 
a reasonable probability exists that the typical firm in this sector 
will be able at this time to afford the controls that will be necessary 
to meet the proposed standard. The Agency endeavored to gather 
information on examples of how these compliance costs would impact 
particular companies, and to establish whether existing order plans 
(e.g. for newer engines) might already contemplate costs which this 
rule would require, but was unable to find any significant information 
in this regard. The Agency welcomes information that will provide 
additional evidence on this important question.
    Conclusion: metal and nonmetal mining sector. Based on the best 
evidence available at this time, the Agency has concluded that the 
proposed rule for the underground metal and nonmetal sector meets the 
statutory requirement that the Secretary attain the highest degree of 
health and safety protection for the miners in that sector, with 
feasibility a consideration.

Appendix to Part V: Diesel Emission Control Estimator

    As noted in the text of this part, MSHA has developed a model 
that can help it estimate the impact on dpm concentrations of 
various control variables. The model also permits the estimation of 
actual dpm concentrations based upon equipment specifications. This 
model, or simulator, is called the ``Diesel Emission Control 
Estimator'' (or the ``Estimator'').
    The model is capable only of simulating conditions in production 
or other confined areas of an underground mine. Air flow 
distribution makes modeling of larger areas more complex. The 
Estimator can be used in any type of underground mine.
    While the calculations involved in this model can be done by 
hand, use of a computer spreadsheet system facilitates prompt 
comparison of the results of alternative combinations of controls. 
Changing a particular entry instantly changes all dependent outputs. 
Accordingly, MSHA developed the Estimator as a spreadsheet format. 
It can be used in any standard spreadsheet program.
    A paper discussing this model has been presented and published 
as an SME Preprint (98-146) in March 1998 at the Society for Mining 
and Exploration Annual Meeting. It was demonstrated at a workshop at 
the Sixth International Mine Ventilation Congress, Pittsburgh, Pa., 
in June 1997. The Agency is making available to the mining community 
the software and instructions necessary to enable it to perform 
simulations for specific mining situations. Copies may be obtained 
by contacting: Dust Division, MSHA, Pittsburgh Safety and Health 
Technology Center, Cochrans Mill Road, P.O. Box 18233, Pittsburgh, 
Pa., 15236. The Agency welcomes comments on the proposed rule that 
include information obtained by using the Estimator. The Agency also 
welcomes comments on the model itself, and suggestions for 
improvements.
    Determining the Current DPM Concentration. The Estimator was 
designed to provide an indication of what dpm concentration will 
remain in a production area once a particular combination of 
controls is applied. Its baseline is the current dpm concentration, 
which of course reflects actual equipment and work practices.
    If the actual ambient dpm concentration is known, this 
information provides the best baseline for determining the outcome 
from applying control technologies. Any method that can reliably 
determine ambient dpm concentrations under the conditions involved 
can be utilized. A description of various methods available to the 
mining community is described in part II of this preamble.
    If the exact dpm concentration is not known, estimates can be 
obtained in several ways. One way is to take a percentage of the 
respirable dust concentration in the area. Studies have shown that 
dpm can range from 50-90% of the respirable dust concentration, 
depending on the specific operation, the size distribution of the 
dust and the level of controls in place. Another method is simply to 
choose a value of 644 for an underground coal mine, or 830 for an 
underground metal or nonmetal mine. These values correspond to the 
average mean concentration which MSHA sampling to date has measured 
in such underground mines. Or, depending upon mine conditions, some 
other value from the range of mean mine concentrations displayed in 
part III of this preamble might be an appropriate baseline -- for 
example, an average similar to that of mine sections like the one 
for which controls are required.
    The Estimator has been designed to automatically compute another 
estimate of current ambient dpm concentration, and to provide 
outputs using this estimate even when the actual ambient dpm 
concentration is available and used in the model. This is done by 
using emissions data for the engines involved--specific manufacturer 
emissions data where available, or an average using the known range 
of emissions for each type of engine being used.
    As with other estimates of current ambient dpm concentration, 
using engine data to derive this baseline measure does not produce 
the same results as actual dpm measurements. The Agency's experience 
is that the use of published engine emissions rates provides a good 
estimate of dpm exposures when the engines involved are used under 
heavy duty cycle conditions; for light duty cycle equipment, the 
published emission rates will generally overestimate the ambient 
particulate exposures. Also, such an approach assumes that the 
average ambient concentration derived is representative of the 
workplace where miners actually work or travel.
    Columns. An example of a full spreadsheet from the Estimator is 
displayed as Figure V-5. The example here involves the application 
of various controls in an underground metal and nonmetal mine. As 
illustrated in the discussion in this part, the Estimator can be 
used equally well to ascertain what happens

[[Page 58205]]

to dpm concentrations in an underground coal mine when the high-
efficiency filters required by the proposed rule are used under 
various ventilation and section dpm intake conditions. Underground 
coal mine operators who are interested in ascertaining what impact 
it might have on dpm concentrations in their mines if the proposed 
rule permitted the use of alternative controls, or required the use 
of additional controls (e.g. filters on light duty equipment), can 
use the Estimator for this purpose as well.

  Figure V-5.--Example of Estimator Spreadsheet Results for a Section of an Underground Metal and Nonmetal Mine
           [Work Place Diesel Emissions Control Estimator; Mine Name: Underground Metal and Nonmetal]
----------------------------------------------------------------------------------------------------------------
                                                               Column A                       Column B
----------------------------------------------------------------------------------------------------------------
1. MEASURED OR ESTIMATED IN MINE DP EXPOSURE        330 g/m3
 (g/m3).
2. VEHICLE EMISSION DATA
    EMISSIONS OUTPUT (gm/hp-hr)
        VEHICLE 1  INDIRECT INJECTION 0.3-0.5 gm/   0.1 gm/hp-hr                   0.1 gm/hp-hr
         hp-hr  FEL.
        VEHICLE 2  OLD DIRECT INJECTION 0.5-0.9 gm/ 0.2 gm/hp-hr                   0.2 gm/hp-hr
         hp-hr  Truck 1.
        VEHICLE 3  NEW DIRECT INJECTION 0.1-0.4 gm/ 0.1 gm/hp-hr                   0.1 gm/hp-hr
         hp-hr  Truck 2.
        VEHICLE 4.................................  0.0                            0.0 gm/hp-hr
    VEHICLE OPERATING TIME (hours)
        VEHICLE 1   FEL...........................  9 hours                        9 hours
        VEHICLE 2   Truck 1.......................  9 hours                        9 hours
        VEHICLE 3   Truck 2.......................  9 hours                        9 hours
        VEHICLE 4   ..............................  0                              0 hours
    VEHICLE HORSEPOWER (hp)
        VEHICLE 1  FEL............................  315 hp                         315 hp
        VEHICLE 2  Truck 1........................  250 hp                         250 hp
        VEHICLE 3  Truck 2........................  330 hp                         330 hp
        VEHICLE 4.................................  0 hp                           0 hp
    SHIFT DURATION (hours)........................  10 hours                       10 hours
    AVERAGE TOTAL SHIFT PARTICULATE OUTPUT (gm)...  0.09 gm/hp-hr                  0.12 gm/hp-hr
3. MINE VENTILATION DATA
        FULL SHIFT INTAKE DIESEL PARTICULATE        50 g/m3               50 g/m3
         CONCENTRATION.
        SECTION AIR QUANTITY......................  155000 cfm                     155000 cfm
        AIRFLOW PER HORSEPOWER....................  173 cfm/hp                     73 cfm/hp
4. CALCULATED SWA DP CONCENTRATION WITHOUT          .............................  551 g/m3
 CONTROLS.
5. ADJUSTMENTS FOR EMISSION CONTROL TECHNOLOGY
        ADJUSTED SECTION AIR QUANTITY.............  155000 cfm                     155000 cfm
        VENTILATION FACTOR (INITIAL CFM/FINAL CFM)  1.00                           1.00
        AIRFLOW PER HORSEPOWER....................  173 cfm/hp                     173 cfm/hp
    OXIDATION CATALYTIC CONVERTER REDUCTION (%)
        VEHICLE 1.................................  0%                             20%
        VEHICLE 2  IF USED ENTER 0-20%............  0%                             20%
        VEHICLE 3.................................  0%                             0%
        VEHICLE 4.................................  0%                             0%
    NEW ENGINE EMISSION RATE (gm/hp-hr)
        VEHICLE 1.................................  0.1 gm/hp-hr                   0.1 gm/hp-hr
        VEHICLE 2  ENTER NEW ENGINE EMISSION (gm/   0.2 gm/hp-hr                   0.2 gm/hp-hr
         hp-hr)..
        VEHICLE 3.................................  0.1 gm/hp-hr                   0.1 gm/hp-hr
        VEHICLE 4.................................  0.0 gm/hp-hr                   0.0 gm/hp-hr
    AFTER FILTER OR CAB EFFICIENCY (%)
        VEHICLE 1  Cabs...........................  60%                            60%
        VEHICLE 2  USE 65-95% FOR AFTERFILTERS....  60%                            60%
        VEHICLE 3  USE 50-80% FOR CABS............  60%                            60%
        VEHICLE 4.................................  0%                             0%
6. ESTIMATED FULL SHIFT DP CONCENTRATION..........  162 g/m3              184 g/m3
----------------------------------------------------------------------------------------------------------------
*Note: Use of the Estimator does not free operators from the requirements of the rule. It is intended to serve
  as a guide.

    A full spreadsheet from the Estimator has two columns, labeled A 
and B. Column A displays information on computations where the 
baseline is the measured ambient dpm concentration, or whose 
baselines are estimated as a percentage of respirable dust or by 
using the mean concentration for the sector. Column B displays 
information on computations in which the baseline itself was derived 
from engine emission information entered into the Estimator.
    Sections. The Estimator spreadsheet is divided into 6 sections. 
Sections 1 through 4 contain information on the baseline situation 
in the mine section. Section 5 contains information on proposed new 
controls, and Section 6 displays the dpm concentration expected to 
remain after the application of those new controls. Table V-4 
summarizes the information in each section of the Estimator.

  Table V-4.--Information needed for or provided by each section of the
                             Estimator model
------------------------------------------------------------------------
      Speadsheet section           Input/output       Mine information
------------------------------------------------------------------------
Section 1.....................  Input............  Measured DP Level,
                                                    g/m3.

[[Page 58206]]

Section 2.....................  Input............  Engine Emissions, gm/
                                                    hp-hr.
                                                   Engine Horsepower,
                                                    hp.
                                                   Operation Times, hr.
                                                   Shift Duration, hr.
Section 3.....................  Input............  Section Airflow, cfm
                                                   Intake DP Level,
                                                    g/m3.
Section 4.....................  Output...........  Current DP Level,
                                                    g/m3.
Section 5.....................  Input............  DP Controls: Airflow,
                                                    cfm.
                                                   Oxid. Cat. Converter,
                                                    percent.
                                                   Engine Emissions, gm/
                                                    hp-hr.
                                                   after-filters,
                                                    percent.
                                                   Cabs, percent.
Section 6.....................  Output...........  Projected DP Level,
                                                    g/m3.
------------------------------------------------------------------------

    Section 1. This is the place to enter data on baseline dpm 
concentrations if obtained by actual measurement, estimate based on 
respirable dust concentration, or mean concentration in the mining 
sector. Measurements should be entered in terms of whole diesel 
particulate matter for consistency with engine information. 
Information need not be entered in this section, in which case only 
engine-emission derived estimates will be produced by the Estimator 
(in Column B).
    Sections 2 and 3. Section 2 is the place to enter data about the 
existing engines and engine use, and section 3 is the place to enter 
data about current ventilation practices. This information is used 
in two ways. First, the Estimator uses this information to derive an 
estimated baseline dpm concentration (for column B). Second, by 
comparing this information with that in section 5 on proposed 
controls that would change engines, engine use, or ventilation 
practices, the Estimator calculates the improvement in dpm that 
would result.
    The first information entered in section 2 is the dpm emission 
rate (in gm/hp-hr) for each vehicle. The Estimator in its current 
form provides room to enter appropriate identification information 
for up to four vehicles. However, when multiple engines of the same 
type are used, the spreadsheet can be simplified and the number of 
entries conserved by combining the horsepower of these engines. For 
example, two 97 hp, 0.5 gm/hp-hr engines can be entered as a single 
194 hp, 0.5 gm/hp-hr engine. However, if the estimate is to involve 
the use of different controls for each engine, the data for each 
engine must be entered separately. In order to account for the duty 
cycle, the engine operating time for each piece of equipment must 
then be entered in section 2, along with the length of the shift.
    The last item in section 2, the ``average total shift 
particulate output'' in grams, is calculated by the Estimator based 
on the measured concentration entered in section 1 (for column A, or 
the engine emission rates for column B), the intake concentration, 
engine horsepower, engine operating time, and airflow. For column A, 
the average total shift diesel particulate output is calculated from 
the formula:

E(a) = (DPM(m) -I) x (Q(I)/35200)/[Sum (Hp(I) x To(I))]

Where:

E(a) = Average engine output, gm/hp-hr
DPM(m) = Measured concentration of diesel particulate, g/
m3
Q(I) = Initial section ventilation, cfm
I = Intake concentration, g/m3
Hp(I) = Individual engine Horsepower, hp
To(I) = Individual engine operating times, hours

    For column B, the average total shift diesel particulate output 
is calculated from the formula:

E(a) = [Sum (E(I) x Hp(I) x To(I))]/[Sum (Hp(I))]/Ts
Where:

E(a) = Average engine output, gm/hp-hr
E(I) = Individual engine emission rates, gm/hp-hr
Hp(I) = Individual engine Horsepower, hp
To(I) = Individual engine operating times, hours
Ts = Shift length, hours

    The ``average total shift particulate'' provides useful 
information in determining what types of controls would be most 
useful. If the average output is less than 0.3, controls such as 
cabs and afterfilters would have a large impact on dpm. If the 
average output is greater than 0.3, new engines would have a large 
impact on dpm.
    There are two data elements concerning existing ventilation in 
the section that must be entered into section 3 of the Estimator: 
the full shift intake dpm concentration, and the section air 
quantity. The former can be measured, or an estimate can be used. 
Based upon MSHA measurements to date, an estimate of between 25 and 
100 micrograms of dpm per cubic meter would account for the dpm 
contribution coming into the section from the rest of the mine.
    The last item in section 3, the airflow per horsepower, is 
calculated by the Estimator from the information entered on these 
two items in sections 2 and 3, as an indication of ventilation 
system performance. If the value is less than 125 cfm/hp, 
consideration should be given to increasing the airflow. If the 
value is greater than 200 cfm/hp, primary consideration would focus 
on controls other than increased airflow.
    Section 4. Section 4 only displays information in Column B. 
Using the individual engine emissions, horsepower, operating time, 
section airflow , intake DPM and shift length, the Estimator 
calculates a presumed dpm concentration. The presumed dpm 
concentration is calculated by the formula:

DPM(a) = {[[Sum (E(I) x  Hp(I)  x  To(I))]  x  35,300/
Q(I)]+I} x [Ts/8]

Where:

35,300 is a metric conversion factor
DPM(a) = Shift weighted average concentration of diesel particulate, 
g/m3
E(I) = Individual engine emission rates, gm/hp-hr
Hp(I) = Individual engine Horsepower, hp
To(I) = Operating time hours
Ts = Shift length, hours
Q(I) = Initial section ventilation, cfm
I = Intake concentration, g/m3

    Section 5. Information about any combination of controls likely 
to be used to reduce dpm emissions in underground mines--changes in 
airflow, the addition of oxygen catalytic converters, the use of an 
engine that has a lower dpm emission rate, and the addition of 
either a cab or aftertreatment filter--is entered into Section 5. 
Information is entered here, however, only if it involves a change 
to the baseline conditions entered into Sections 2 and 3. Entries 
are cumulative.
    The first possible control would be to increase the system air 
quantity. The minimum airflow should either be the summation of the 
Particulate Index (PI) for all heavy duty engines in the area of the 
mine, or 200 cfm/hp. The spreadsheet displays the ratio between the 
air quantity in section 5 and that in section 3, and the airflow per 
horsepower.
    The second possible control would be to add an oxidation 
catalytic converter to one or more engines if not initially present. 
When such converters are used, a dpm reduction of up to 20 percent 
can be obtained (as noted in MSHA's Toolbox). The third possible 
control would be to change one or more engines to newer models to 
reduce emissions. As noted in part II of this preamble, clean engine 
technology has emissions as low as 0.1 and 0.2 gm/hp-hr.
    Finally, each piece of equipment could be equipped with either a 
cab and an

[[Page 58207]]

aftertreatment filter. Since MSHA considers it unlikely an operator 
would use both controls, the Estimator is designed to assume that no 
more than one of these two possible controls would be used on a 
particular engine. Ceramic aftertreatment filters that can reduce 
emissions by 65-80% are currently on the market; MSHA is soliciting 
information about the potential for future improvements in ceramic 
filtration efficiency. Paper filters can remove up to 95% or more of 
dpm, but these can only be used on equipment whose exhaust is 
appropriately cooled to avoid igniting the paper (i.e., permissible 
coal equipment, or other equipment equipped with a water scrubber or 
other cooling device). Air conditioned cabs can reduce the exposure 
of the equipment operator by anywhere from 50-80%. (See part II, 
section 6, for information on filters and cabs). But while the 
Estimator will produce an estimate of the full shift dpm 
concentration that includes the effects of using such cabs, it 
should be remembered that such an estimate is only directly relevant 
to equipment operators. Thus, cabs are a viable control for sections 
where the miners are all equipment operators, but they will not 
impact the dpm concentrations to which other miners are exposed.
    Section 6. The Estimator displays in this section an estimated 
full shift dpm concentration. If a measured baseline dpm 
concentration was entered in section 1, this information will be 
displayed in column A. Column B displays an estimate based on the 
engine emissions data.
    Here is how the computations are performed.
    The effect of control application is calculated in Section 6, 
Column A from the following formula:

DPM(c) = {Sum [(To(I) / Ts)  x  1000  x  [(E(a) / 60)  x  Hp(I)  x  
(35300 /Q(I))  x  (Q(I) / Q(f))  x  (1-R(o))  x  (1-R(f))  x  (1-
R(e))]} + I

Where:

DPM(c) = Diesel particulate concentration after control application/
g/m3,
E(a) = Average engine emission rate, gm/hp-hr,
Hp(I) = Individual engine Horsepower, hp.
To(I) = Operating time hours,
I = Intake DPM concentration, g/m3,
Q(I) = Initial section ventilation, cfm,
Q(f) = Final section ventilation, cfm,
R(o) = Efficiency of oxidation catalytic converter, decimal
R(f) = Efficiency of after filters or cab, decimal,
R(e) = Reduction for new engine technology, decimal, and
R(e) = (Ei--Ef) / Ei

Where:

R(e) = Reduction for new engine technology, decimal,
E(i) = Initial engine emission rates, gm/hp-hr,
E(f) = New engine emission rates, gm/hp-hr,

    The effect of control application is calculated in Section 6, 
Column B from the following formula:

DPM(c) = {Sum[(E(I)  x  Hp(I)  x  To(I))  x  (35,300 / Q(I))  x  (1-
R(o))  x  (1-R(f))  x  (1-R(e))]  x  [Q(I) / Q(f)]}+I

Where:

DPM(c) = Diesel particulate concentration after control application/
g/m3,
E(I) = Individual engine emission rates, gm/hp-hr,
Hp(I) = Individual engine Horsepower, hp,
To(I) = Operating time hours,
I = Intake DPM concentration, g/m3,
Q(I) = Initial section ventilation, cfm,
Q(f ) = Final section ventilation, cfm,
R(o) = Efficiency of oxidation catalytic converter, decimal,
R(f) = Efficiency of after filters or cab, decimal,
R(e) = Reduction for new engine technology, decimal, and
R(e) = (Ei--Ef) / Ei

Where:

R(e) = Reduction for new engine technology, decimal,
E(i) = Initial engine emission rates, gm/hp-hr,
E(f) = New engine emission rates, gm/hp-hr.

VI. Impact Analyses

    This part of the preamble reviews several impact analyses which the 
Agency is required to provide in connection with proposed rulemaking. 
The full text of these analyses can be found in the Agency's PREA.

(A) Costs and Benefits: Executive Order 12866

    In accordance with Executive Order 12866, MSHA has prepared a 
Preliminary Regulatory Economic Analysis (PREA) of the estimated costs 
and benefits associated with the proposed rule for the underground 
metal and nonmetal sector.
    The key conclusions of the PREA are summarized, together with cost 
tables, in part I of this preamble (see Question and Answer 5). In 
addition, a summary of the assumptions made by MSHA about the largest 
cost component of the proposed rule--the costs for equipment that the 
underground metal and nonmetal sector will need to comply with the 
proposed concentration limit--can be found in part V of this preamble, 
in the discussion of the feasibility of the proposed rule for that 
sector. The complete PREA is part of the record of this rulemaking, and 
is available from MSHA.
    The Agency considers this rulemaking ``significant'' under section 
3(f) of Executive Order 12866, and has so designated the rule in its 
semiannual regulatory agenda (RIN 1219-AB11). However, based upon the 
PREA, MSHA has determined that the proposed rule does not constitute an 
``economically significant'' regulatory action pursuant to section 
3(f)(1) of Executive Order 12866.

(B) Regulatory Flexibility Certification and Initial Regulatory 
Flexibility Analysis (IRFA)

    Introduction. Pursuant to the Regulatory Flexibility Act of 1980, 
MSHA has analyzed the impact of this rule upon small businesses. MSHA 
specifically solicits comments on the cost data and assumptions 
concerning the initial regulatory flexibility analysis for underground 
metal and nonmetal mine operators.
    To facilitate public participation in the rulemaking process, MSHA 
will mail a copy of the proposed rule and this preamble to every 
underground metal and nonmetal mine operator. In addition, the entire 
IRFA is reprinted here.
    Definition of Small Mine. Under SBREFA, in analyzing the impact of 
a proposed rule on small entities, MSHA must use the SBA definition for 
a small entity or, after consultation with the SBA Office of Advocacy, 
establish an alternative definition for the mining industry by 
publishing that definition in the Federal Register for notice and 
comment. MSHA has not taken such an action, and hence is required to 
use the SBA definition.
    The SBA defines a small mining entity as an establishment with 500 
employees or less (13 CFR 121.201). MSHA's use of the 500 or less 
employees includes all employees (miners and office workers). Almost 
all mines (including underground coal mines) fall into this category 
and hence, can be viewed as sharing the special regulatory concerns 
which the RFA was designed to address. That is why MSHA has, for 
example, committed to providing to all underground metal and nonmetal 
mine operators a copy of a compliance guide explaining provisions of 
this rule.
    The Agency is concerned, however, that looking only at the impacts 
of the proposed rule on all the mines in this sector does not provide 
the Agency with a very complete picture on which to make decisions. 
Traditionally, the Agency has also looked at the impacts of its 
proposed rules on what the mining community refers to as ``small 
mines''--those with fewer than 20 miners. The way these small mines 
perform mining operations is generally recognized as being different 
from the way other mines operate which has led to special attention by 
the Agency and the mining community.
    This analysis complies with the legal requirements of the RFA for 
an analysis of the impacts on ``small entities'' while continuing 
MSHA's traditional look at ``small mines''.

[[Page 58208]]

    Underground Metal and Nonmetal Mines: Initial Regulatory 
Flexibility Analysis. Since MSHA has not recently prepared an initial 
regulatory flexibility analysis in connection with a proposed rule, the 
mining community has not had an opportunity to review such an analysis. 
Accordingly, some background may be helpful.
    The requirements for an initial RFA should describe the impact of 
the proposed rule on small entities. Each initial RFA analysis shall 
contain:
    ``(1) A description of the reasons why action by the Agency is 
being considered;
    (2) A succinct statement of the objectives of, and legal basis for, 
the proposed rule;
    (3) A description of and, where feasible, an estimate of the number 
of small entities to which the proposed rule will apply;
    (4) A description of the projected reporting, recordkeeping and 
other compliance requirements of the proposed rule, including an 
estimate of the classes of small entities which will be subject to the 
requirement and the type of professional skills necessary for 
preparation of the report or record;
    (5) An identification, to the extent practicable, of all relevant 
Federal rule which may duplicate, overlap or conflict with the proposed 
rule.''
    In addition, ``Each initial regulatory flexibility analysis shall 
also contain a description of any significant alternatives to the 
proposed rule which accomplish the stated objectives of applicable 
statutes and which minimize any significant economic impact of the 
proposed rule on small entities. Consistent with the stated objective 
of applicable statutes, the analysis shall discuss significant 
alternatives such as:
    (1) The establishment of differing compliance or reporting 
requirements or timetables that take into account the resources 
available to small entities;
    (2) The clarification, consolidation, or simplification of 
compliance and reporting requirements under the rule for such small 
entities;
    (3) The use of performance rather than design standards;
    (4) and an exemption from coverage of the rule, or any part 
thereof, for such entities.''
    MSHA would encourage the mining community to structure its comments 
on these points in a similar manner so that the Agency will be able to 
clearly respond to them in its final analysis.
    MSHA hopes the presentation that follows will provide reviewers 
enough information to readily grasp the implications of the rule for 
small entities in particular, but it strongly encourages reviewers to 
also pursue the referenced discussions of risk, feasibility, historical 
and other information in the preamble accompanying the proposed rule.
    Reasons Why Agency Action is Being Considered. A rule is needed for 
underground metal and nonmetal mines to assure that a significant risk 
of material impairment to the health of miners working in these mines 
is reduced to the extent economically and technologically feasible for 
this sector as a whole. The risk is created by the presence of diesel 
engines in the closed environment of underground metal and nonmetal 
mines which generate in their emissions very high concentrations of 
particulate matter. These very small particles penetrate to the deepest 
regions of the lung. As explained in detail in Part III of the preamble 
accompanying the proposed rule, exposure to high concentrations of 
diesel particulate matter puts miners at significant risk of material 
impairment to their health. These elevated risks include, but are not 
limited to, an increased risk of lung cancer. At the present time, many 
underground miners, including many miners in underground metal and 
nonmetal mines, are exposed to levels of diesel particulate matter that 
far exceed the exposures of any other group of workers in the United 
States. The reductions in exposure to diesel particulate required in 
this sector will necessitate changes in mine equipment and practices 
that are too significant to bring about without regulatory action.
    Objectives of the Rule; Legal Basis. MSHA has two related 
objectives it hopes to accomplish through the rulemaking for 
underground metal and nonmetal mines. For miners in this sector, it is 
MSHA's objective that they will no longer be exposed to diesel 
particulate matter in far greater concentrations than any other group 
of workers in this country. For mine operators in this sector, it is 
MSHA's objective to provide each with flexibility as to the controls 
they may implement to reduce the concentration of diesel particulate 
matter to the prescribed limit.
    The proposed rule won't eliminate the risk of harm, nor even reduce 
exposures to the level which industry experts are considering 
establishing as a Threshold Limit Value, but it would reduce miner 
exposures to levels comparable to those faced by workers in other 
industries who work around diesel powered equipment. While MSHA has 
tentatively concluded that there may remain a significant risk to miner 
health even with this proposed rule, the Agency has also tentatively 
concluded that: (a) the proposed rule would provide substantial health 
benefits; and (b) additional controls beyond those provided for in the 
proposed rule may not be feasible for the underground metal and 
nonmetal sectors at this time.
    Initially, MSHA had an additional objective in this rulemaking: to 
establish a uniform rule for all mining sectors because uniformity 
tends to be the most effective solution for worker's health and for 
industry compliance. After exploring the implications of such an 
approach, however, the Agency concluded that a uniform approach does 
not appear to be feasible at this time. MSHA has tentatively concluded 
that while there is a technological fix available for underground coal 
mine operators, the best solution for underground metal and nonmetal 
mine operators will vary considerably. Moreover, while the Agency has 
confidence that there is a validated method for measuring diesel 
particulate matter concentrations in underground metal and nonmetal 
mines, it believes some further work is necessary before recommending 
that such an approach be used in underground coal mines due to the 
possibility of contamination of the samples by coal dust. The Agency 
will reconsider this approach in light of the record in this proceeding 
before finalizing a rule, but at this point has concluded that it 
cannot justify proposing a uniform approach to this problem at this 
time.
    MSHA has an obligation under Sec. 101(a)(6)(A) of the Federal
    Mine Safety and Health Act of 1977 (the ``Mine Act'') which 
requires the Secretary to set standards which most adequately assure, 
on the basis of the best available evidence, that no miner will suffer 
material impairment of health over the miner's working lifetime. The 
Mine Act makes no distinction between the obligations of operators 
based on size.

Number and Description of Small Entities Affected. Number and 
Description of Small Entities Affected

    Underground metal and nonmetal mine operators have used diesel-
powered equipment for a long time, and they are highly dependent upon 
such equipment for production. As discussed in detail in part II of the 
preamble accompanying the proposed rule, a major role of such equipment 
involves haulage. For example, front-end loaders or load-haul-dump 
machines remove the metal or mineral deposits from where it was blasted 
or cut in the mine. However, other types of diesel machinery can also 
be found in

[[Page 58209]]

underground metal and nonmetal mines. Examples of some of these other 
types of diesel powered machines are: roof bolters, jumbo drills, 
scalers, water trucks, and transport or maintenance vehicles. MSHA's 
January 1998 count of the number of diesel powered equipment in 
underground metal and nonmetal mines, shows that of the 261 underground 
metal and nonmetal mines, there are 203 mines that use diesel powered 
equipment on a regular basis.
    Under MSHA's traditional definition of a small mine (those that 
employ less than 20), about 40 percent of the 203 underground metal and 
nonmetal mines that use diesel powered equipment (82 mines) would be 
considered small underground mines. Approximately 69 percent of these 
small underground mines (57 mines  mines) are involved in the 
production of limestone (47 mines) or gold (10 mines). The largest 
number of small underground mines that are involved in the production 
of the same commodity are limestone mines. Underground limestone mines 
account for 57 percent of small mines (47 mines  mines). These 
82 small underground mine operators employ approximately 5 percent of 
all underground metal and nonmetal mine employment, and account for 
about 15 percent of the diesel powered equipment found in underground 
metal and nonmetal mines. On average, about 7.5 diesel powered machines 
are in a small mine, when MSHA's definition of a small mine is used.
    Under the SBA definition of a small mine (those that employ 500 or 
less), about 97 percent of the 203 underground metal and nonmetal mines 
that use diesel powered equipment (196 mines) would be considered small 
underground mines. Approximately 68 percent of these small underground 
mines (134 mines  196 mines) are involved in the production of: 
limestone (85 mines), gold (27 mines), Salt (12 mines), and Zinc (10 
mines). Again, the largest number of small underground mines that are 
involved in the production of the same commodity are limestone mines. 
Underground limestone mines account for 43 percent of small mines (85 
mines  196 mines). These 196 small underground mine operators 
employ approximately 70 percent of all underground metal and nonmetal 
mine employment, and account for about 83 percent of the diesel powered 
equipment found in underground metal and nonmetal mines. On average, 
about 17 diesel powered machines are in a small mine, when SBA's 
definition of a small mine is used.
    The industry profile in part II of this document provides some 
further information concerning the characteristics of underground metal 
and nonmetal mines.
    Proposed Rule Requirements. The compliance requirements of the 
proposed rule for underground metal and nonmetal mine operators are 
described in detail in the preamble to the rule. The compliance costs 
to mine operators are described in detail in the PREA. The material 
following briefly summarizes key elements of the proposed rule.
    The proposed rule would require that underground metal and nonmetal 
mine operators, including small mine operators, observe a set of ``best 
practices'' underground to reduce engine emissions of diesel 
particulate matter. (Similar practices are already in effect in 
underground coal mines as a result of MSHA's diesel equipment rule).
    Only low-sulfur diesel fuel and EPA-approved fuel additives would 
be permitted to be used in diesel-powered equipment in underground 
areas. Idling of such equipment that is not required for normal mining 
operations would be prohibited. In addition, diesel engines would have 
to be maintained in good condition to ensure that deterioration does 
not lead to emissions increases--approved engines would have to be 
maintained in approved condition; the emission related components of 
non-approved engines would have to be maintained in accordance with 
manufacturer specifications; and any installed emission device would 
have to be maintained in effective condition. Equipment operators in 
underground metal and nonmetal mines would be authorized to tag 
equipment with potential pollution problems, and tagged equipment would 
have to be ``promptly'' referred for a maintenance check. As an 
additional safeguard in this regard, maintenance of this equipment 
would have to be done by persons qualified by virtue of training or 
experience to perform the maintenance.
    The proposed rule would also require that, with the exception of 
diesel engines used in ambulances and fire-fighting equipment, any 
diesel engines added to the fleet of an underground metal or nonmetal 
mine, 60 days after the date the rule is promulgated, must be an engine 
approved by MSHA under Part 7 or Part 36. The composition of the 
existing fleet would not be impacted by this part of the proposed rule.
    In addition, the proposed rule would establish a limit on the 
concentration of diesel particulate matter permitted in areas of an 
underground metal or nonmetal mine where miners normally work or 
travel.
    All underground metal and nonmetal mine operators would be given a 
full five years to meet this limit. However, starting eighteen months 
after the rule is published, underground metal and nonmetal mine 
operators would have to observe an interim limit. No limit at all on 
the concentration of diesel particulate matter would be applicable for 
the first eighteen months following promulgation. Instead, this period 
would be used to provide compliance assistance to the underground metal 
and nonmetal mining community to ensure it understands how to measure 
and control diesel particulate matter concentrations in individual 
operations.
    An underground metal and nonmetal mine operator would have to use 
engineering or work practice controls to keep diesel particulate matter 
concentrations below the applicable limit. Administrative controls 
(e.g., the rotation of miners) and personal protective equipment (e.g., 
respirators) do not reduce the concentration of diesel particulate, and 
so are not permitted as a means of permanent compliance with this 
standard. When a mine operator is granted an extension to come into 
compliance with the concentration limit under the narrow range of 
circumstances permitted in the rule, MSHA may require the mine operator 
to utilize personal protective equipment or administrative controls 
during the duration of the extension period. An underground operator 
could filter the emissions from diesel-powered equipment, install 
cleaner-burning engines, increase ventilation, improve fleet 
management, or use a variety of other readily available controls; the 
selection of controls would be left to the operator's discretion. MSHA 
has published a ``toolbox'' of approaches that can be used to reduce 
diesel particulate matter. MSHA will make available an ``Estimator'' 
that operators can plug into a standard spreadsheet program to enable 
them to evaluate the effects of alternative controls in an area of a 
mine before purchasing and implementation decisions are made.
    MSHA has studied a number of metal and nonmetal mines, as described 
in part V of the preamble accompanying the proposed rule, which the 
Agency had reason to think might have particular difficulty in 
controlling diesel particulate matter concentrations. As a result of 
these studies, the Agency believes that in combination with the 
required ``best practices,'' engineering and work practice controls are 
available that can bring diesel particulate matter concentrations in 
all underground metal

[[Page 58210]]

and nonmetal mines down to the interim and final concentration limits 
in a timely manner. Nevertheless, the proposed rule would provide that 
if an operator of an underground metal or nonmetal mine can demonstrate 
that there is no combination of controls that can, due to technological 
constraints, be implemented within that time to reduce the 
concentration of diesel particulate matter to the limit, MSHA may 
approve an application for an extension of time to comply with the 
diesel particulate matter concentration limit. Such a special extension 
is available only once, and is limited to 2 years.
    Sampling to determine compliance with the diesel particulate matter 
concentration limit would be performed directly by MSHA, rather than 
relying upon underground metal and nonmetal mine operator samples; 
however, the proposed rule would also require all underground metal and 
nonmetal mine operators using diesel-powered equipment to sample as 
often as necessary to effectively evaluate diesel particulate matter 
concentrations at the mine.
    The proposed rule would require that if an underground metal or 
nonmetal mine operator is in violation of the applicable limit on the 
concentration of diesel particulate matter, a diesel particulate matter 
compliance plan must be established and remain in effect for 3 years. 
Reflecting practices in this sector, the plan would not have to be 
preapproved by MSHA, but must be retained at the mine site. The plan 
would include information about the diesel-powered equipment in the 
mine and applicable controls. The proposed rule would require operator 
sampling to verify that the plan is effective in bringing diesel 
particulate matter levels at or below the applicable limit, with the 
records kept at the mine site with the plan to facilitate review.
    To enhance miner awareness of the hazards involved, underground 
mine operators using diesel-powered equipment must annually train 
miners exposed to diesel particulate matter on the hazards associated 
with that exposure, and in the controls being used by the operator to 
limit diesel particulate matter concentrations. Underground mine 
operators may propose to include this training in their existing Part 
48 training plans.
    Table VI-1 summarizes the compliance costs of the proposed rule, 
including paperwork costs, to underground metal and nonmetal mine 
operators. As can be seen in the table, of the approximately $19.2 
million per year estimate of total compliance cost for all underground 
metal and nonmetal mine operators, mines with 19 or fewer miners are 
estimated to incur approximately $4.6 million per year (an average cost 
of about $56,100 per year per small mine). When the definition of a 
small mine operator is 500 or less employees, then nearly all 
underground metal and nonmetal mine operators would be included (under 
such a definition, MSHA estimates that approximately $17.2 million of 
the total $19.2 million would be incurred by small mine entities (an 
average cost of about $87,800 per year per small mine). A discussion of 
the benefits of the proposed rule can be found in part I of this 
preamble (see response to Question 5).

[[Page 58211]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.045



    With respect to underground metal and nonmetal mine operators the 
paperwork requirements include paperwork associated with training for 
persons maintaining diesel powered equipment, annual training for those 
miners affected by the hazards of diesel particulate matter, sampling 
for diesel particulate matter, observation of sampling, and tagging 
equipment with pollution problems. In addition, there are paperwork 
requirements for a small portion of underground metal and nonmetal 
mines that pertain to writing applications to extend the period to 
comply with the proposed concentration limits, and for writing a diesel 
particulate control plan.
    With a few exceptions, MSHA estimates that all recordkeeping and 
recording related compliance costs, and all of the other requirements 
of the standard, will require no special professional background beyond 
that currently found in the managers of the underground mines in this 
sector. Based on a small mine definition of less than 20 employees, all 
small underground metal and nonmetal mine operators, as well as half of 
the large mines, are assumed to have sampling performed by an 
independent contractor, because this would be cheaper than setting up 
their own sampling program and purchasing the required sampling 
equipment. Also, regardless of what definition is used to define small 
mines, all underground metal and nonmetal mine operators would have the 
sample analysis performed by an independent contractor, since the 
underground mines do not have the expertises or equipment to analyze 
for diesel particulate matter. Again, no matter what definition is used 
to define small mines, underground metal and nonmetal mine operators 
would need to go outside of the mine expertise to receive a portion of 
their maintenance training.
    Based on a small mine definition of less than 20 miners, the total 
number of annual burden hours to the 82 small underground metal and 
nonmetal mine operators would be 436. When the definition of a small 
mine is 500 or less employees, the total number of annual burden hours 
to 196 small underground metal and nonmetal mine operators would be 
3,472.
    Impact of Other Federal Rules. There are no other Federal (or for 
that matter State) rules of which MSHA is aware that would duplicate, 
overlap or conflict with the proposed rule for underground metal and 
nonmetal mines.
    Significant Alternatives Considered. The Agency considered, and 
adopted as part of the proposed rule, features designed to minimize the 
impacts on

[[Page 58212]]

small entities, and the smallest metal and nonmetal mines in 
particular, consistent with the stated objectives of the Mine Act. It 
is important to note in this regard that in implementing the Mine Act's 
requirement that the Secretary attain the highest degree of safety and 
health protection, consistent with feasibility, the Agency based its 
decisions on the technological and economic feasibility of the proposed 
rule on detailed information about the impacts on mines with 500 or 
fewer employees and, separately, that segment of these mines with less 
than 20 employees. Part V of the preamble accompanying the proposed 
rule reviews the decisions made by the Agency with respect to this 
statutory obligation.
    Under the proposed rule no limit on diesel particulate 
concentration would be in effect for 18 months, during which time the 
Agency would provide extensive compliance assistance to the mining 
community. During this time, MSHA would be working with small 
underground metal and nonmetal mine operators to provide help 
concerning the measuring of diesel particulate concentrations. In 
addition, MSHA would use this time to provide technical assistance 
about control methods to small mine operators.
    In fact, this individualized compliance assistance would supplement 
general guidance the Agency has already started to provide to the 
mining industry, and to small mines in particular. In 1995, the Agency 
held three workshops in various areas of the country to enable the 
mining community to share ideas on practical ways to control diesel 
emissions, and made transcripts of these workshops widely available. 
Subsequently, the Agency published a ``toolbox'' to disseminate this 
information in a format designed to facilitate use by small mines in 
particular (appended to the end of this document is a copy of an MSHA 
publication, ``Practical Ways to Reduce Exposure to Diesel Exhaust in 
Mining--A Toolbox). Moreover, before the rule goes into effect, the 
Agency will also develop and distribute a compliance guide, as required 
by SBREFA, and will provide information to small mines through such 
other formats as may be suggested by the mining community. For example, 
MSHA is also considering creating a one page fact sheet or card that 
can be used by the mining industry to complement training requirements 
concerning notification of affected miners of the hazards associated 
with diesel particulate. This can be of particular help to small mine 
operators who have training resources that may not be as extensive as 
those found in large mining operations. MSHA will also mail a copy of 
the proposed rule to every underground mine operator which primarily 
benefits small operators.
    Beyond the initial 18 months the proposed rule would provide for 
compliance assistance. Also, the proposed rule reflects a preliminary 
decision by the agency to delay for a full 5 years after promulgation 
of a final rule the effective date of the requirement which will have 
the most significant impact on small underground metal and nonmetal 
mines--the concentration limit for diesel particulate. An interim 
concentration limit would apply until that date--a limit that should 
not be at all difficult for small mines to reach, particularly after 
all of the compliance assistance that precedes it. This extended time 
for full implementation of the proposed rule ensures that technological 
issues can be timely resolved prior to the final rule's effective date. 
It also recognizes that this rule is a significant one for the 
underground metal and nonmetal sector, that almost all mines in this 
sector are considered small entities under SBA's definition, and that 
having adequate time to come into full compliance is of particular 
importance to the smallest mines in this sector.
    Finally, MSHA is including a one-time two-year extension for mines 
that require additional time to adopt to the final concentration 
limits.
    Other features of the proposed rule also reflect MSHA's recognition 
of the size distribution of the entities which have to implement any 
requirements. Special attention was paid to making the rule's 
requirements comprehensible to the mining community, including the 
provision of a chart summarizing recordkeeping requirements, and 
comments in that regard are being solicited. Training and operator 
sampling requirements were specifically designed to be performance 
oriented to minimize costs, while at the same time ensure that the 
important protections that flow from such approaches are included in 
every mine operator's approach to this health problem.
    MSHA did consider a regulatory approach that would have focused on 
limiting worker exposure rather than limiting particulate 
concentration. Under such an approach, operators would have been able 
to use administrative controls (e.g., rotation of personnel) and 
respiratory protection equipment to reduce diesel particulate exposure. 
It is generally accepted industrial hygiene practice, however, to 
eliminate or minimize hazards before resorting to personal protective 
equipment. Moreover, while rotation of workers may be a perfectly 
acceptable practice for a hazard like noise (where reducing exposure 
can allow the ear to recover, thus avoiding any harm), such a practice 
is generally not considered acceptable in the case of carcinogens since 
it merely places more workers at risk. Also, allowing use of these 
practices would not necessarily help the smallest mines, not all small 
mines can efficiently rotate workers. Accordingly, the agency declined 
to propose such an approach for this serious health hazard, although it 
welcomes comments in this regard.
    MSHA is proposing dpm concentration limits as the core of the rule. 
Although the Agency has developed costs in terms of assumptions about 
the numbers of engineering controls that will be required to meet the 
standard, design standards are not the point of the regulation. Rather, 
the Agency has suggested as broad a menu of compliance techniques as is 
practicable, so that individual mines can select specific techniques 
that best fit their circumstances.
    The Agency has also declined to propose alternatives involving 
design standards or specific frequency requirements, which it believes 
would have had a more significant impact on small entities in the 
underground metal and nonmetal mining sector--although it will 
certainly take another look at these if the rulemaking record so 
warrants. Section 101(a)(6)(A) of the Mine Act requires the Secretary 
when promulgating standards dealing with toxic substances or harmful 
physical agents to base such mandatory standards on the best available 
evidence, to most adequately assure that no miner will suffer material 
impairment of health over his working lifetime. The Act also requires 
that when promulgating such standards, other factors such as the latest 
scientific data in the field, the feasibility of the standard and 
experience gained under the Act and other health and safety laws be 
considered. Thus, the Mine Act requires that the Secretary, in 
promulgating a standard, attain the highest degree of health and safety 
protection for the miner, based on the ``best available evidence'', 
with feasibility as a consideration.
    As a result of this requirement, MSHA seriously considered 
alternatives that would have significantly increased costs for both 
large and small mine operators. For example, in light of the health 
risks involved, and the existing environmental restrictions on 
particulate matter, the Agency considered proposing for underground

[[Page 58213]]

metal and nonmetal mine operators a lower limit on the concentration of 
diesel particulate, and shortening the time frame to get to a final 
limit. The Agency has tentatively concluded, however, that such 
approaches would not be feasible for this sector as a whole. The Agency 
also considered requiring more stringent work practice and engine 
controls in this sector than those ultimately proposed--i.e., practices 
exactly like those applicable in the underground coal sector. Such an 
alternative would have required: (a) weekly emissions tests of diesel 
powered equipment in underground metal and nonmetal mines instead of 
just tagging suspect equipment for prompt inspection; (b) requiring 
these mines to establish training programs for maintenance personnel; 
and (c) requiring the metal and nonmetal diesel powered fleet to be 
turned over completely within a few years so as to have only approved 
engines. The Agency concluded, however, that the concerns which 
warranted such an approach in underground coal mines had not been 
established in underground metal and nonmetal mines; and that with 
respect to the risks created by diesel particulate matter, the approach 
taken in the proposed rule could provide adequate protection in a cost 
effective manner.
    MSHA also considered other rigorous requirements such as: requiring 
the installation of a particulate filter on every new piece of diesel 
powered equipment added to the underground metal and nonmetal diesel 
powered fleet regardless of the diesel particulate matter concentration 
level as an added layer of miner protection, establishing a fixed 
schedule for operator monitoring of the concentration of diesel 
particulate emissions, and requiring that diesel particulate control 
plans be preapproved by MSHA before implementation to ensure that their 
effectiveness had been verified. These approaches were not included in 
the proposed rule because MSHA concluded that less stringent 
alternatives could achieve the same level of protection with less 
adverse impact on underground mining operations, especially small 
underground mining operations.
    MSHA welcomes comments on whether there are significant 
alternatives it should consider that would accomplish the previously 
stated purpose and objectives of this rulemaking while reducing the 
impact on small entities. In this regard, the Agency would also welcome 
suggestions for alternatives that focus on addressing special concerns 
on the very smallest mines in this sector--those with less than 20 
miners. It is important to remember, however, that under the Mine Act, 
smaller mines must provide the same level of protection to their 
workers as larger mines.
    As required under the law, MSHA will be consulting with the Chief 
Counsel for Advocacy on the initial regulatory flexibility analysis for 
the underground metal and nonmetal mining sector. Consistent with 
agency practice, notes of any meetings with the Chief Counsel's office 
on this rule, or any written communications, will be placed in the 
rulemaking record. The Agency will continue to consult with the Chief 
Counsel's office as the rulemaking process proceeds.

(C) Unfunded Mandates Reform Act of 1995

    MSHA has determined that, for purposes of Sec. 202 of the Unfunded 
Mandates Reform Act of 1995, this proposed rule does not include any 
Federal mandate that may result in increased expenditures by State, 
local, or tribal governments in the aggregate of more than $100 
million, or increased expenditures by the private sector of more than 
$100 million. Moreover, the Agency has determined that for purposes of 
Sec. 203 of that Act, this proposed rule does not significantly or 
uniquely affect small governments.
    The Unfunded Mandates Reform Act was enacted in 1995. While much of 
the Act is designed to assist the Congress in determining whether its 
actions will impose costly new mandates on State, local, and tribal 
governments, the Act also includes requirements to assist Federal 
agencies to make this same determination with respect to regulatory 
actions.
    Based on the analysis in the Agency's preliminary Regulatory 
Economic Statement, the compliance costs of this proposed rule for the 
underground metal and nonmetal mining industry are about $19.2 million 
per year. Accordingly, there is no need for further analysis under 
Sec. 202 of the Unfunded Mandates Reform Act.
    MSHA has concluded that small governmental entities are not 
significantly or uniquely impacted by the proposed regulation. The 
proposed rule affects only underground metal and nonmetal mines, and 
MSHA is not aware of any state, local or tribal government ownership 
interest in underground mines. MSHA seeks comments of any state, local, 
and tribal government which believes that they may be affected by this 
rulemaking.

(D) Paperwork Reduction Act of 1995 (PRA)

    This proposed rule contains information collections which are 
subject to review by the Office of Management and Budget (OMB) under 
the Paperwork Reduction Act of 1995 (PRA95). Tables VI-2 and VI-3 show 
the estimated annual reporting burden hours associated with each 
proposed information collection requirement. These burden hour 
estimates are an approximation of the average time expected to be 
necessary for a collection of information, and are based on the 
information currently available to MSHA. Included in these estimates 
are the time for reviewing instructions, gathering and maintaining the 
data needed, and completing and reviewing the collection of 
information.
    MSHA invites comments on: (1) Whether any proposed collection of 
information presented here (and further detailed in the Agency's PREA) 
is necessary for proper performance of MSHA's functions, including 
whether the information will have practical utility; (2) the accuracy 
of MSHA's estimate of the burden of the proposed collection of 
information, including the validity of the methodology and assumptions 
used; (3) ways to enhance the quality, utility, and clarity of 
information to be collected; and (4) ways to minimize the burden of the 
collection of information on respondents, including through the use of 
automated collection techniques, when appropriate, and other forms of 
information technology.
    Submission. The Agency has submitted a copy of this proposed rule 
to OMB for its review and approval of these information collections. 
Interested persons are requested to send comments regarding this 
information collection, including suggestions for reducing this burden, 
to the Office of Information and Regulatory Affairs, OMB New Executive 
Office Bldg., 725 17th St. NW., Rm. 10235, Washington, DC 20503, Attn: 
Desk Officer for MSHA. Submit written comments on the information 
collection not later than December 28, 1998.
    The Agency's complete paperwork submission is contained in the 
PREA/IRFA, and includes the estimated costs and assumptions for each 
proposed paperwork requirement (these costs are also included in the 
Agency's cost and benefit analyses for the proposed rule). A copy of 
the PREA/IRFA is available from the Agency. These paperwork 
requirements have been submitted to the Office of Management and Budget 
for review under section 3504(h) of the Paperwork Reduction Act of 
1995.

[[Page 58214]]

Respondents are not required to respond to any collection of 
information unless it displays a current valid OMB control number.
    Description of Respondents. Those required to provide the 
information are underground metal and nonmetal mine operators and 
diesel engine manufacturers.
    Description. The proposed rule contains information collection 
requirements for: underground metal and nonmetal mine operators in 
Secs. 57.5060, 57.5062, 57.5066, 57.5070, 57.5071 and 57.5075; and for 
diesel engine manufacturers in Part 7, subpart E. Annual burden hours 
are 3,865 for underground metal and nonmetal mines. There are 36 burden 
hours related to manufacturers of diesel powered engines which would 
recur annually.
    Tables VI-2 and VI-3 summarize the burden hours for mine operators 
and manufacturers by section.

     Table VI-2.--Underground Metal and Nonmetal Mines Burden Hours
------------------------------------------------------------------------
                    Detail                      Large    Small    Total
------------------------------------------------------------------------
57.5060......................................      306      123      429
57.5062......................................       49       11       60
57.5066......................................      207       76      283
57.5070......................................      136        6      142
57.5071......................................    2,600      213    2,813
57.5075......................................      131        7      138
                                              --------------------------
    Total....................................    3,429      436    3,865
------------------------------------------------------------------------


          Table VI-3.--Diesel Engine Manufacturers Burden Hours
------------------------------------------------------------------------
                            Detail                                Total
------------------------------------------------------------------------
Part 7, Subpart E.............................................       36
                                                               ---------
    Total.....................................................       36
------------------------------------------------------------------------

(E) National Environmental Protection Act

    The National Environmental Policy Act (NEPA) of 1969 requires each 
Federal agency to consider the environmental effects of proposed 
actions and to prepare an Environmental Impact Statement on major 
actions significantly affecting the quality of the human environment. 
MSHA has reviewed the proposed standard in accordance with the 
requirements of the NEPA (42 U.S.C. 4321 et seq.), the regulation 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 preliminarily determined that this proposed 
standard will have no significant environmental impact.
    Commenters are encouraged to submit their comments on this 
determination.

(F) Executive Order 13045

    In accordance with Executive Order 13045, protection of children 
from environmental health risks and safety risks, MSHA has evaluated 
the environmental health or safety effects of the proposed rule on 
children. The Agency has determined that this proposal would not have 
an adverse impact on children.

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Supplementary References:
Below is a list of supplemental references that MSHA reviewed and 
considered in the development of the proposed rule. These documents 
are not specifically cited in the preamble discussion, but are 
applicable to MSHA's findings:
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Isoforms,'' Journal of Clinical Investigation, 94(4):1417-1425, 
1994.
Enya, Takeji, et al., ``3 Nitrobenzanthrone, a Powerful Bacterial 
Mutagen and Suspected Human Carcinogen Found in Diesel Exhaust and 
Airborne Particulates,'' Environmental Science and Technology, 
31:2772-2776, 1997.
Fischer, Torkel, and Bolli Bjarnason, ``Sensitizing and Irritant 
Properties of 3 Environmental Classes of Diesel Oil and Their 
Indicator Dyes,'' Contact Dermatitis, 34:309-315, 1996.
Frew, A.J., and S.S. Salvi, ``Diesel Exhaust Particles and 
Respiratory Allergy,'' Clinical and Experimental Allergy, 27:237-
239, 1997.
Fujimaki, Hidekazu, et al., ``Intranasal Instillation of Diesel 
Exhaust Particles and Antigen in Mice Modulated Cytokine Productions 
in Cervical Lymph Node Cells,'' International Archives of Allergy 
and Immunology, 108:268-273, 1995.
Fujimaki, Hidekazu, et al., ``IL-4 Production in Mediastinal Lymph 
Node Cells in Mice Intratracheally Instilled with Diesel Exhaust 
Particles and Antigen,'' Toxicology, 92:261-268, 1994.

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Fujimaki, Hidekazu, et al., ``Inhalation of Diesel Exhaust Enhances 
Antigen-Specific IgE Antibody Production in Mice,'' Toxicology, 
116:227-233, 1997.
Ikeda, Masahiko, et al., ``Impairment of Endothelium-Dependent 
Relaxation by Diesel Exhaust Particles in Rat Thoracic Aorta,'' 
Japanese Journal of Pharmacology, 68:183-189, 1995.
Lovik, Martinus, et al., ``Diesel Exhaust Particles and Carbon Black 
Have Adjuvant Activity on the Local Lymph Node Response and Systemic 
IgE Production to Ovalbumin,'' Toxicology, 121:165-178, 1997.
Muranaka, Masaharu, et al., ``Adjuvant Activity of Diesel-Exhaust 
Particles for the Production of IgE Antibody in Mice,'' J Allergy 
Clin Immunology, 77:616-623, 1986.
Takafuji, Shigeru, et al., ``Diesel-Exhaust Particulates Inoculated 
by the Intranasal Route Have an Adjuvant Activity for IgE Production 
in Mice,'' J Allergy Clin Immunol, 79:639-645, 1987.
Takenaka, Hiroshi, et al., ``Enhanced Human IgE Production Results 
from Exposure to the Aromatic Hydrocarbons from Diesel Exhaust: 
Direct Effects on B-Cell IgE Production,'' J Allergy Clin Immunol, 
95-103-115, 1995.
Terada, Nobushisa, et al., ``Diesel Exhaust Particulates Enhance 
Eosinophil Adhesion to Nasal Epithelial Cells and Cause 
Degranulation,'' International Archives of Allergy and Immunology, 
114:167-174, 1997.
Tsien, Albert, et al., ``The Organic Component of Diesel Exhaust 
Particles and Phenanthrene, a Major Polyaromatic Hydrocarbon 
Constituent, Enhances IgE Production by IgE-Secreting EBV-
Transformed Human B Cells in Vitro,'' Toxicology and Applied 
Pharmacology, 142:256-263, 1997.
Yang, Hui-Min, et al., ``Effects of Diesel Exhaust Particles on the 
Release of Interleukin-1 and Tumor Necrosis Factor-Alpha from Rat 
Alveolar Macrophages,'' Experimental Lung Research, 23:269-284, 
1997.

List of Subjects in 30 CFR Part 57

    Diesel particulate matter, Metal and nonmetal, Mine safety and 
health, Underground mines.

    Dated: October 16, 1998.
J. Davitt McAteer,
Assistant Secretary for Mine Safety and Health.

    It is proposed to amend Chapter I of Title 30 of the Code of 
Federal Regulations as follows:

PART 57--[AMENDED]

    1. The authority citation for Part 57 continues to read as follows:

    Authority: 30 U.S.C. 811, 957, 961.

    2. The heading of Subpart D of Part 57 is revised to read as 
follows: ``Subpart D--Air Quality, Radiation, Physical Agents, and 
Diesel Particulate Matter''
    3. Sections 57.5060 through 57.5075, and in undersigned center 
heading, are added to Subpart D to read as follows:

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

Diesel Particulate Matter--Underground Only


Sec. 57.5060  Limit on concentration of diesel particulate matter.

    (a) After [the date 18 months after the date of publication of the 
final rule] and until [the date 5 years after the date of publication 
of the final rule], any mine operator covered by this part shall limit 
the concentration of diesel particulate matter to which miners are 
exposed by restricting the average eight-hour equivalent full shift 
airborne concentration of total carbon, where miners normally work or 
travel, to 400 micrograms per cubic meter of air (400TC 
g/m3).
    (b) After [the date 5 years after the date of publication of the 
final rule], any mine operator covered by this part shall limit the 
concentration of diesel particulate matter to which miners are exposed 
in underground areas of a mine by restricting the average eight-hour 
equivalent full shift airborne concentration of total carbon, where 
miners normally work or travel, to 160 micrograms per cubic meter of 
air (160TC g/m3).
    (c)(1) If, as a result of technological constraints, a mine 
requires additional time to come into compliance with the limit 
specified in paragraph (b) of this section, the operator of the mine 
may file an application with the Secretary for a special extension.
    (2) No mine may be granted more than one special extension, nor may 
the time otherwise available under this section to a mine to comply 
with the limit specified in paragraph (b) of this section be extended 
by more than two years.
    (3) The application for a special extension may be approved, and 
the additional time authorized, only if the application includes 
information adequate for the Secretary to ascertain:
    (i) That diesel-powered equipment was used in the mine prior to 
October 29, 1998;
    (ii) That there is no combination of controls that can, due to 
technological constraints, bring the mine into full compliance with the 
limit specified in paragraph (b) of this section within the time 
otherwise specified in this section;
    (iii) The lowest achievable concentration of diesel particulate, as 
demonstrated by data collected under conditions that are representative 
of mine conditions using the method specified in Sec. 57.5061(b); and
    (iv) The actions the operator will take during the duration of the 
extension to:
    (A) Maintain the lowest concentration of diesel particulate; and
    (B) Minimize the exposure of miners to diesel particulate.
    (4) An application for a special extension may be approved only if:
    (i) The application is filed at least 180 days prior to the date 
the mine is required by this section to be in full compliance with the 
limit established by paragraph (b) of this section; and
    (ii) The application certifies that one copy of the application has 
been posted at the mine site for 30 days prior to the date of 
application, and another copy has been provided to the authorized 
representative of miners.
    (5) A mine operator shall comply with the terms of any approved 
application for a special extension. A copy of an approved application 
for a special extension shall be posted at the mine site for the 
duration of the special extension period.
    (d) An operator shall not utilize personal protective equipment, 
nor shall an operator utilize administrative controls, to comply with 
the requirements of either paragraph (a) or paragraph (b) of this 
section.


Sec. 57.5061  Compliance determinations.

    (a) A single sample collected and analyzed by the Secretary in 
accordance with the procedure set forth in paragraph (b) of this 
section shall be an adequate basis for a determination of noncompliance 
with an applicable limit on the concentration of diesel particulate 
matter pursuant to Sec. 57.5060.
    (b) The Secretary will collect and analyze samples of diesel 
particulate matter by using the method described in NIOSH Analytical 
Method 5040 and determining the amount of total carbon, or by using any 
method subsequently determined by NIOSH to provide equal or improved 
accuracy in mines subject to this part.


Sec. 57.5062  Diesel particulate matter control plan.

    (a) In the event of a violation by the operator of an underground 
metal or nonmetal mine of the applicable concentration limit 
established by Sec. 57.5060, the operator, in accordance with the 
requirements of this section, must--
    (1) Establish a diesel particulate matter control plan for the mine 
if one is not already in effect, or modify the existing diesel 
particulate matter control plan, and
    (2) Demonstrate that the new or modified diesel particulate matter

[[Page 58221]]

control plan is effective for controlling the concentration of diesel 
particulate matter to the applicable concentration limit specified in 
Sec. 57.5060.
    (b) A diesel particulate control plan shall describe the controls 
the operator will utilize to maintain the concentration of diesel 
particulate matter to the applicable limit specified by Sec. 57.5060. 
The plan shall also include a list of diesel-powered units maintained 
by the mine operator, together with information about any unit's 
emission control device and the parameters of any other methods used to 
control the concentration of diesel particulate matter. The plan may be 
consolidated with the ventilation plan required by Sec. 57.8520. A copy 
of the current diesel particulate matter control plan shall be retained 
at the mine site during its duration and for one year thereafter.
    (c) An operator shall demonstrate plan effectiveness by monitoring, 
using the measurement method specified by Sec. 57.5061(b), sufficient 
to verify that the plan will control the concentration of diesel 
particulate matter to the applicable limit under conditions that can be 
reasonably anticipated in the mine. A copy of each verification sample 
result shall be retained at the mine site for five years. Such operator 
monitoring shall be in addition to, and not in lieu of, any sampling by 
the Secretary pursuant to Sec. 57.5061.
    (d) The records required by paragraphs (b) and (c) of this section 
shall be available for review upon request by the authorized 
representative of the Secretary, the authorized representative of the 
Secretary of Health and Human Services, or the authorized 
representative of miners. In addition, upon request by the District 
Manager or the authorized representative of miners for a copy of any 
records required to be maintained pursuant to paragraph (b) or (c) of 
this section, the operator shall provide such copy.
    (e)(1) A control plan established as a result of this section shall 
remain in effect for 3 years from the date of the violation which 
caused it to be established, except as provided in paragraph (e)(3) of 
this section.
    (2) A control plan modified as a result of this section shall 
remain in effect, as so modified, for 3 years from the date of the 
violation which caused the plan to be modified, except as provided in 
paragraph (e)(3) of this section.
    (3) An operator shall modify a diesel particulate matter control 
plan during its duration as required to reflect changes in mining 
equipment or circumstances, and shall, upon request from the Secretary, 
demonstrate the effectiveness of the modified plan by monitoring, using 
the measurement method specified by Sec. 57.5061(b), sufficient to 
verify that the plan will control the concentration of diesel 
particulate matter to the applicable limit under conditions that can be 
reasonably anticipated in the mine.
    (f) Failure of an operator to comply with the provisions of the 
diesel particulate matter control plan in effect at a mine or to 
conduct required verification sampling shall be a violation of this 
part without regard for the concentration of diesel particulate matter 
that may be present at any time.


Sec. 57.5065  Fueling and idling practices.

    (a) Diesel fuel used to power equipment in underground areas shall 
not have a sulfur content greater than 0.05 percent. The operator shall 
retain purchase records evidencing compliance with this requirement for 
one year after the date of purchase.
    (b) Only fuel additives registered by the U.S. Environmental 
Protection Agency shall be used in diesel powered equipment operated in 
underground areas.
    (c) Idling of mobile diesel-powered equipment in underground areas 
is prohibited except as required for normal mining operations.


Sec. 57.5066  Maintenance standards.

    (a) Any diesel powered equipment operated at any time in 
underground areas shall meet the following maintenance standards:
    (1) Any approved engine shall be maintained in approved condition;
    (2) The emission related components of any non-approved engine 
shall be maintained to manufacturer specifications; and
    (3) Any emission or particulate control device installed on the 
equipment shall be maintained in effective operating condition.
    (b)(1) A mine operator shall authorize and require each miner 
operating diesel powered equipment covered by paragraph (a) of this 
section to affix a visible and dated tag to such equipment at any time 
the miner notes any evidence that the equipment may require maintenance 
in order to comply with the maintenance standards of paragraph (a) of 
this section.
    (2) A mine operator shall ensure that any equipment tagged pursuant 
to this section is promptly examined by a person authorized by the mine 
operator to maintain diesel equipment, and the affixed tag shall not be 
removed until such examination has been completed.
    (3) A mine operator shall retain a log of any equipment tagged 
pursuant to this section. The log shall include the date the equipment 
is tagged, the date an examination was made of such equipment, the name 
of the person making such examination, and any action taken as a result 
of such examination. The information in the log with respect to any 
piece of equipment examined as a result of this section shall be 
retained for one year after the date of examination.
    (c) Persons authorized by a mine operator to maintain diesel 
equipment covered by paragraph (a) of this section must be qualified, 
by virtue of training or experience, to ensure that the maintenance 
standards of paragraph (a) of this section are observed. An operator 
shall retain appropriate evidence of the competence of any person to 
perform specific maintenance tasks in compliance with those standards 
for one year after the date of any maintenance, and shall upon request 
provide such documentation to the authorized representative of the 
Secretary.


Sec. 57.5067  Engines.

    Any diesel engine introduced into an underground area of a mine 
covered by this part after [date 60 days after date publication of the 
final rule], other than an engine in an ambulance or fire fighting 
equipment which is utilized in accordance with mine fire fighting and 
evacuation plans, must have affixed a plate evidencing approval of the 
engine pursuant to subpart E of Part 7 of this title or pursuant to 
Part 36 of this title.


Sec. 57.5070  Miner training.

    (a) All miners at a mine covered by this part who can reasonably be 
expected to be exposed to diesel emissions on that property shall be 
trained annually in--
    (1) The health risks associated with exposure to diesel particulate 
matter;
    (2) The methods used in the mine to control diesel particulate 
matter concentrations;
    (3) Identification of the personnel responsible for maintaining 
those controls; and
    (4) Actions miners must take to ensure the controls operate as 
intended.
    (b) An operator shall retain at the mine site a record that the 
training required by this section has been provided for one year after 
completion of the training.


Sec. 57.5071  Environmental monitoring.

    (a) Mine operators shall monitor as often as necessary to 
effectively evaluate, under conditions that can be reasonably 
anticipated in the mine--
    (1) Whether the concentration of diesel particulate matter in any 
area of

[[Page 58222]]

the mine where miners normally work or travel exceeds the applicable 
limit specified in Sec. 57.5060; and
    (2) The average full shift airborne concentration of diesel 
particulate matter at any position or on any person designated by the 
Secretary.
    (b) The mine operator shall provide affected miners and their 
representatives with an opportunity to observe exposure monitoring 
required by this section. Mine operators must give prior notice to 
affected miners and their representatives of the date and time of 
intended monitoring.
    (c) If any monitoring performed under this section indicates that 
the applicable concentration limit established by Sec. 57.5060 has been 
exceeded, an operator shall promptly post notice of the corrective 
action being taken, initiate corrective action by the next work shift, 
and promptly complete such corrective action.
    (d)(1) The results of monitoring for diesel particulate matter, 
including any results received by a mine operator from sampling 
performed by the Secretary, shall be posted on the mine bulletin board 
within 15 days of receipt and shall remain posted for 30 days, and a 
copy shall be provided to the authorized representative of miners.
    (2) The results of any samples collected by a mine operator as a 
result of monitoring under this section, and information about the 
sampling method used for obtaining such samples, shall be retained for 
five years from the date of the sample.


Sec. 57.5075  Diesel particulate records.

    (a) The table entitled ``Diesel Particulate Recordkeeping 
Requirements'' lists the records which must be retained by operators 
pursuant to Secs. 57.5060 through 57.5071, and the duration for which 
particular records need to be retained.

                                  Diesel Particulate Recordkeeping Requirements
----------------------------------------------------------------------------------------------------------------
                 Record                        Section reference                     Retention time
----------------------------------------------------------------------------------------------------------------
Approved application for extension of    Sec.  57.5060(c)               1 year beyond duration of extension.
 time to comply with final
 concentration limit.
Control plan...........................  Sec.  57.5062(b)               1 year beyond duration of plan.
Compliance plan verification sample      Sec.  57.5062(c)               5 years from sample date.
 results.
Purchase records noting sulfur content   Sec.  57.5065(a)               1 year beyond date of purchase.
 of diesel fuel.
Maintenance log........................  Sec.  57.5066(b)               1 year after date any equipment is
                                                                         tagged.
Evidence of competence to perform        Sec.  57.5066(c)               1 year after date maintenance performed.
 maintenance.
Annual training provided to potentially  Sec.  57.5070(b)               1 year beyond date training completed.
 exposed miners.
Sampling method used to effectively      Sec.  57.5071                  5 years from sample date.
 evaluate mine particulate
 concentration, and sample results.
----------------------------------------------------------------------------------------------------------------

    (b)(1) Any record listed in this section which is required to be 
retained at the mine site may, notwithstanding such requirement, be 
retained elsewhere if the record is immediately accessible from the 
mine site by electronic transmission.
    (2) Upon request from an authorized representative of the Secretary 
of Labor, the Secretary of Health and Human Services, or from the 
authorized representative of miners, mine operators shall promptly 
provide access to any record listed in the table in this section.
    (3) A miner, former miner, or, with the miner's or former miner's 
written consent, a personal representative of a miner, shall have 
access to any record required to be maintained pursuant to Sec. 57.5071 
to the extent the information pertains to the miner or former miner. 
Upon request by such person, the operator shall provide the first copy 
of such record requested by a person at no cost to that person, and any 
additional copies requested by that person at reasonable cost.
    (c) Whenever an operator ceases to do business, that operator shall 
transfer all records required to be maintained by this part, or a copy 
thereof, to any successor operator who shall receive these records and 
maintain them for the required period.

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Appendix to Preamble--Background Discussion--MSHA's Toolbox

    Note: This Appendix will not appear in the Code of Federal 
Regulations. It is provided here as a guide.
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[FR Doc. 98-28277 Filed 10-28-98; 8:45 am]
BILLING CODE 4510-43-C