[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.
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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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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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Table I-1.--Compliance Cost for Underground Metal and Nonmetal Mine
Operators
(Dollars X 1,000)
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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
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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).
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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.
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[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
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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
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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.
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\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.
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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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[[Page 58182]]
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]]
[GRAPHIC] [TIFF OMITTED] TP29OC98.041
[[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