Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

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.

BILLING CODE 4510-43-P

[[Page 58105]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.018

BILLING CODE 4510-43-C

[[Page 58106]]

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.

BILLING CODE 4510-43-P

[[Page 58109]]

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

Operators

(Dollars X 1,000)

[GRAPHIC] [TIFF OMITTED] TP29OC98.019

BILLING CODE 4510-43-C

[[Page 58110]]

As required by the Regulatory Flexibility Act, MSHA has performed a

review of the effects of the proposed rule on ``small entities''. The

results--including information about the average cost for mines in each

sector with less than 500 employees and mines in each sector with less

than 20 miners--are summarized in response to Question 7.

Paperwork. Tables I-2 and I-3 show additional paperwork burden

hours which the proposed rule would require. Only those existing or

proposed regulatory requirements which would, as a result of this

rulemaking, result in new burden hours, are noted. The costs for these

paperwork burdens, a subset of the overall costs of the proposed rule,

are specifically noted in Part VII of the Agency's PREA. Table I-2

shows the burden hours for large and small mines--those with less than

20 miners.

Table I-2.--Underground Metal and Nonmetal Mine Burden Hours

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

Detail Large Small Total

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

57.5060...................................... 306 123 429

57.5062...................................... 49 11 60

57.5066...................................... 207 76 283

57.5070...................................... 136 6 142

57.5071...................................... 2,600 213 2,813

57.5075...................................... 131 7 138

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

Total.................................... 3,429 436 3,865

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

Table I-3 shows the additional burden hours for diesel engine

manufacturers. The compliance costs related to diesel equipment

manufacturers are assumed to be passed through to underground metal and

nonmetal operators as explained in the PREA. Thus, diesel equipment

manufacturers are not estimated to incur any direct cost as a result of

this rule.

Table I-3.--Diesel Engine Manufacturers Burden Hours

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

Detail Total

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

Part 7, Subpart E.............................................. 36

Total...................................................... 36

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

Benefits. The proposed rule would reduce the exposure of

underground metal and nonmetal miners to dpm, thereby reducing the risk

of adverse health effects and their concomitant effects.

The risks being addressed by this rulemaking arise because some

miners are exposed to high concentrations of the very small particles

produced by engines that burn diesel fuel. As discussed in Part II of

the preamble, diesel powered engines are used increasingly in

underground mining operations because they permit the use of mobile

equipment and provide a full range of power for both heavy-duty and

light-duty operations (i.e., for production equipment and support

equipment, respectively), while avoiding the explosive hazards

associated with gasoline. But underground mines are confined spaces

which, despite ventilation requirements, tend to accumulate significant

concentrations of particles and gases--both those produced by the mine

itself (e.g., methane gas and silica dust liberated by mining

operations) and those produced by equipment used in the mine.

As discussed in MSHA's risk assessment (Part III of this preamble),

the concentrations of diesel particulates to which some underground

miners are currently exposed are significantly higher than the

concentrations reported for other occupations involving the use of

dieselized equipment; and at such concentrations, exposure to dpm by

underground miners over a working lifetime is associated with an excess

risk of a variety of adverse health effects.

[[Page 58111]]

The nature of the adverse health effects associated with such

exposures suggests the nature of the savings to be derived from

controlling exposure. Acute reactions can result in lost production

time for the operator and lost pay (and perhaps medical expenses) for

the worker. Hospital care for acute breathing crises or cancer

treatment can be expensive, result in lost income for the worker, lost

income for family members who need to provide care and lost

productivity for their employers, and may well involve government

payments (e.g., Social Security disability and Medicare). Serious

illness and death lead to long term income losses for the families

involved, with the potential for costs from both employers (e.g.,

workers' compensation payouts, pension payouts) and society as a whole

(e.g., government assisted aid programs).

The information available to the Agency suggests that as exposure

is reduced, so are the adverse health consequences. For example, data

collected on the effects of environmental exposure to fine particulates

suggest that reducing occupational dpm exposures by as little as 75

g/m3 (roughly corresponding to a reduction of 25

g/m3 in 24-hour ambient atmospheric concentration)

could lead to significant reductions in the risk of various acute

responses, including mortality. And chronic occupational exposure has

been linked to an estimated 30 to 40 percent increase in the risk of

lung cancer. All the quantitative risk models reviewed by NIOSH suggest

excess risks of lung cancer of more than one per thousand for miners

who have long-term occupational exposures to dpm concentrations in

excess of 1000 g/m3, and the epidemiologically-

based risk estimates suggest higher risks. The Agency's estimate is

that implementation of the proposed rule would avoid 28 lung cancers

per 1,000 affected miners, or approximately 7 lung cancer cases a year

over an initial 65-year period.\2\ Note that because lung cancer

associated with diesel particulate matter typically arises from

cumulative exposure and after some latency period, these health

benefits-in terms of the reduced incidence of lung cancer illness and

subsequent death-will not materialize until some years after passage of

the proposed rule.

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

\2\ In the long run, the average approaches 46445=10

lung cancers avoided per year as the number of years considered

increases beyond 65.

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

The yearly reduction in excess lung cancer deaths due to reduced

exposure to diesel particulate matter may occur gradually, depending on

the historical cumulative exposure to diesel particulate matter among

the veteran workforce. Since the average latency period for lung cancer

is 20 years, the full benefit associated with a concentration limit of

200 g/m\3\ may not be seen before then.

Despite these quantitative indications, quantification of the

benefits is difficult. Although increased risk of lung cancer has been

shown to be associated with dpm exposure among exposed workers, a

conclusive dose-response relationship upon which to base quantification

of benefits has not been demonstrated. The Agency nevertheless intends,

to the extent it can, to develop an appropriate analysis quantifying

benefits in connection with the final rule.

The Agency does not have much experience in quantifying benefits in

the case of a proposed health standard (other than its recent proposal

on controlling mining noise, where years of compliance data and hearing

loss studies provide a much more complete quantitative picture than

with dpm). MSHA therefore welcomes suggestions for the appropriate

approach to use to quantify the benefits likely to be derived from this

rulemaking. Please identify scientific studies, models, and/or

assumptions suitable for estimating risk at different exposure levels,

and data on numbers of miners exposed to different levels of dpm.

[[Page 58112]]

(6) Did MSHA Actively Consider Alternatives to What Is Being Proposed?

Yes. Once MSHA determined that the evidence of risk required a

regulatory action, the Agency considered a number of alternative

approaches, the most significant of which are reviewed in Part V of the

preamble.

The consideration of options proceeded in accordance with the

requirements of Section 101(a)(6)(A) of the Federal Mine Safety and

Health Act of 1977 (the ``Mine Act''). In promulgating standards

addressing toxic materials or harmful physical agents, the Secretary

must promulgate standards which most adequately assure, on the basis of

the best available evidence, that no miner will suffer material

impairment of health over his/her working lifetime. In addition, the

Mine Act requires that the Secretary, when promulgating mandatory

standards pertaining to toxic materials or harmful physical agents,

consider other factors, such as the latest scientific data in the

field, the feasibility of the standard and experience gained under the

Mine Act and other health and safety laws. Thus, the Mine Act requires

that the Secretary, in promulgating a standard, attain the highest

degree of health and safety protection for the miner, based on the

``best available evidence,'' with feasibility a consideration.

As a result, MSHA seriously considered a number of alternatives

that would, if adopted as part of the proposed rule, have provided

increased protection--and would also have significantly increased

costs. For example, the Agency considered proposing a more stringent

concentration limit for dpm in underground metal and nonmetal mines, or

shortening the time frame to achieve compliance with that limit. But as

discussed in more detail in Part V, MSHA concluded, however, that such

an approach may not be feasible for the underground sector at this

time. Options considered by the Agency included: requiring the

installation of a particulate filter on every new piece of diesel-

powered equipment added to the fleet of an underground metal or

nonmetal mine regardless of the dpm concentration level, as an added

layer of miner protection; establishing a fixed schedule for operator

monitoring of the concentration of diesel particulate emissions; and

requiring control plans be preapproved by MSHA before implementation to

ensure their effectiveness had been verified. These approaches were not

included in the proposal because MSHA concluded that less stringent

alternatives could achieve the same level of protection with less

adverse impact.

MSHA also considered alternatives that would have led to a

significantly lower-cost proposal, e.g., establishing a less stringent

concentration limit in underground metal and nonmetal mines, or

increasing the time for mine operators to come into compliance.

However, based on the current record, MSHA has tentatively concluded

that such approaches would not be as protective as those being

proposed, and that the approach proposed is both economically and

technologically feasible. As a result, the Agency has not proposed to

adopt these alternatives.

MSHA also explored whether to permit the use of administrative

controls (e.g., rotation of personnel) and personal protective

equipment (e.g., respirators) to reduce the diesel particulate exposure

of miners. It is generally accepted industrial hygiene practice,

however, to eliminate or minimize hazards at the source before

resorting to personal protective equipment. Moreover, such a practice

is generally not considered acceptable in the case of carcinogens since

it merely places more workers at risk. Accordingly, the proposal

explicitly prohibits the use of such approaches, except in those

limited cases where MSHA approves, due to technological constraints, a

2-year extension for an underground metal and nonmetal mine on the time

to comply with the final concentration limit.

MSHA did make a concerted effort to design the requirements of the

proposal to minimize unnecessary burdens. Each element of the proposal

was independently reviewed to ascertain whether it was really needed,

as were all the paperwork requirements, and each was designed with

cost-effectiveness in mind. Training and operator sampling

requirements, for example, were specifically designed to be

performance-oriented to minimize costs, while at the same time crafted

to ensure that each operator's activities provide necessary

protections.

The Agency considered requiring the underground metal and nonmetal

sector to use work practice and engine controls exactly like those

already applicable in the underground coal sector as a result of MSHA's

diesel equipment rule (62 FR 55412). Such an alternative would have

required each metal and nonmetal operator: (a) to conduct weekly

emissions tests of diesel-powered equipment in underground metal and

nonmetal mines instead of just tagging suspect equipment for prompt

inspection; (b) to establish training programs for maintenance

personnel; and (c) to turn over the mine's diesel fleet within a few

years so as to have only approved engines. The agency concluded,

however, that the conditions which warrant such an approach in

underground coal mines had not been established for metal and nonmetal

mines; and that with respect to the risks created by dpm, the approach

taken in the proposed rule could provide adequate protection in a cost-

effective manner.

The agency hopes that comments and suggestions from the mining

community on the proposed rule will help it identify further

improvements in this regard.

(7) What Will the Impact Be on the Smallest Underground Metal and

Nonmetal Mines? What Consideration Did MSHA Give to Alternatives for

the Smallest Mines?

The Regulatory Flexibility Act requires MSHA and other regulatory

agencies to conduct a review of the effects of proposed rules on small

entities. That review is summarized here; a copy of the full review is

included in Part VI of this preamble, and in the Agency's PREA. The

Agency encourages the mining community to provide comments on this

analysis.

The Small Business Administration generally considers a small

mining entity to be one with less than 500 employees. MSHA has

traditionally defined a small mine to be one with less than 20 miners,

and has focused special attention on the problems experienced by such

mines in implementing safety and health rules, e.g., the Small Mine

Summit, held in 1996. Accordingly, MSHA has separately analyzed the

impact of the proposed rule on mines with 500 employees or less, and

those with less than 20 miners.

Table I-4 summarizes MSHA's estimates of the average costs of the

proposed rule to a small underground metal and nonmetal mine.

Table I-4.--Average Cost per Small Underground Metal and Nonmetal Mine

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

Size UG M/NM DPM g/m\3\. However, in an

effort to make things easier on a day-to-day basis for the mining

community, the proposed concentration limit on dpm for this sector

would be expressed in terms of the measurement method MSHA will use for

compliance purposes to determine dpm concentrations. (That method,

NIOSH Analytical Method 5040, is specified in proposed Sec. 57.5061,

and is discussed in more detail in response to Question 12. MSHA is

proposing to use it because of its accuracy). The method will analyze a

dust sample to determine the amount of total carbon present. Total

carbon comprises 80-85% of the dpm emitted by diesel engines.

Accordingly, using the lower boundary of 80%, a concentration limit of

200DPM g/m\3\ can be achieved by restricting total

carbon to 160TC g/m\3\. This is the way the

proposed standard is expressed:

After [insert the date 5 years after the date of promulgation of

this rule] any mine operator covered by this part shall limit the

concentration of diesel particulate matter to which miners are

exposed by restricting the average eight-hour equivalent full shift

airborne concentration of total carbon, where miners normally work

or travel, to 160 micrograms per cubic meter of air

(160TC g/m\3\).

All underground metal and nonmetal mines would be given a full five

years to meet this limit, which is referred to in this preamble as the

``final'' concentration limit. However, starting eighteen months after

the rule is promulgated, underground metal and nonmetal mines would

have to observe an ``interim'' dpm concentration limit--expressed as a

restriction on the concentration of total carbon of 400 micrograms per

cubic meter (400TC g/m\3\). The interim limit would

bring the concentration of whole dpm in underground metal and nonmetal

mines to which miners are exposed down to about 500 micrograms per

cubic meter. No limit at all on the concentration of dpm would be

applicable for the first eighteen months following promulgation.

Instead, this period would be used to provide compliance assistance to

the metal and nonmetal mining community to ensure it understands how to

measure and control diesel particulate matter concentrations in

individual operations (and to implement work practice controls).

A mine operator would have to use engineering or work practice

controls to keep dpm concentrations below the applicable limit.

Administrative controls (e.g., the rotation of miners) and personal

protective equipment (e.g., respirators) are explicitly barred as a

means of compliance with the interim or final concentration limit. An

operator could filter the emissions from diesel-powered equipment,

install cleaner-burning engines, increase ventilation, improve fleet

management, or use a variety of other readily available controls; the

selection of controls would be left to the operator's discretion. MSHA

has published a ``toolbox'' of approaches that can be used to reduce

dpm; a copy of this useful publication is appended to the end of this

document. The Agency has also developed a model that can be run on a

standard spreadsheet program to compare the effects of alternative

controls before purchase and implementation decisions are made. The

model, and some examples of its

[[Page 58116]]

use, are presented in Part V of this preamble.

The proposal would provide that, if an operator of a metal or

nonmetal mine can demonstrate that there is no combination of controls

that can, due to technological constraints, be implemented within the 5

years permitted to reduce the concentration of dpm to the final

concentration limit, MSHA may approve an application for an additional

extension of time to comply with the dpm concentration limit. Such a

special extension is available only once, and is limited to 2 years. To

obtain a special extension, an operator must provide information in the

application adequate for MSHA to ensure that the operator will: (a)

maintain concentrations at the lowest limit which is technologically

achievable; and (b) take appropriate actions to minimize miner exposure

(e.g., provide suitable respiratory protection during the extension

period).

Measurements to determine noncompliance with the dpm concentration

limit would be made directly by MSHA, rather than having the Agency

rely upon operator samples. Under the rule, a single Agency sample,

using the sampling and analytical method prescribed by the rule, would

be adequate to establish a violation. MSHA would take measurement

uncertainty into account before issuing a citation, as discussed in

response to Question 12.

The proposed rule would require that if an underground metal or

nonmetal mine exceeds the applicable limit on the concentration of dpm,

a diesel particulate matter compliance plan must be established and

remain in effect for 3 years. The purpose of such plans is to ensure

that the mine has instituted practices that will demonstrably control

dpm levels thereafter. Reflecting current practices in this sector, the

plan would not have to be preapproved by MSHA. The plan would include

information about the diesel-powered equipment in the mine and

applicable controls. The proposed rule would require operator sampling

to verify that the plan is effective in bringing dpm levels down below

the applicable limit, with the records kept at the mine site with the

plan to facilitate review. Failure of an operator to comply with the

requirements of the dpm control plan or to conduct adequate

verification sampling would be a violation; MSHA would not be required

to sample to establish such a violation.

To enhance miner awareness of the hazards involved, mines using

diesel-powered equipment must annually train miners exposed to dpm in

the hazards associated with that exposure, and in the controls being

used by the operator to limit dpm concentrations. An operator may

propose to include this training in the Part 48 training plan.

The proposed rule would also require all operators in this sector

using diesel-powered equipment to sample as often as necessary to

effectively evaluate dpm concentrations at the mine. The purpose of

this requirement is to assure that operators are familiar with current

dpm concentrations so as to be able to protect miners. Since mine

conditions vary, MSHA is not proposing to establish a defined schedule

for operator sampling; but rather, to propose a performance-oriented

approach. The Agency would evaluate compliance with this sampling

obligation by reviewing evidence of operator compliance with the

concentration limit, as well as information retained by operators about

their sampling.

Consistent with the statute, the proposed rule would require that

miners and their representatives have the right to observe any operator

monitoring--including any sampling required to verify the effectiveness

of a dpm control plan.

(12) How Is MSHA Proposing To Measure the Amount of dpm in Underground

Metal and Nonmetal Mines?

Techniques for measuring dpm concentrations are reviewed in detail

in Part II of this preamble.

For a method to be used for compliance purposes, it must be able to

distinguish dpm from other particles present in various mines, be

accurate at the concentrations to be measured, and consistently measure

dpm regardless of the mix or condition of the equipment in the mine.

The technique being proposed for compliance sampling in underground

metal and nonmetal mines meets these requirements. It involves sampling

with a quartz fiber filter mounted in an open face filter holder, and a

chemical analysis of the filter to determine the amount of carbon

collected. The entire process, NIOSH Analytical Method 5040, has been

validated as meeting NIOSH's accuracy criterion--i.e., that

measurements come within 25% of the true concentration at least 95% of

the time. While there are other methods that can be used to provide

accurate measurements of diesel particulate matter in some types of

mines and under some circumstances, this technique appears to provide

consistent and accurate results in all underground metal and nonmetal

mining environments.

Although the NIOSH method was validated using a regular respirable

dust sampler, MSHA gave consideration to the use of a size selector

impactor sampler, developed by the Bureau of Mines, that would not

collect any dust over 1 micrometer (micron) in diameter. Canada is

exploring the use of such an approach with an alternative analytical

method. However, measurements by the Agency to date indicate that in

some underground metal and nonmetal mines, as much as 30% of the dpm

present may be larger than 1 micron in size. The Agency is continuing

to evaluate such an approach, and welcomes comments on the implications

to miners and mine operators of excluding from consideration this

larger fraction of dpm.

The method described in NIOSH Analytical Method 5040 provides a way

to determine the amount of diesel particulate in the sample. Diesel

particulate consists of a core of elemental carbon onto which are

adsorbed various organic components and sulfates. The NIOSH Analytical

Method separately analyzes the amount of elemental carbon and the

amount of organic carbon present in the sample. These two amounts are

then added together to get the amount of total carbon present in the

sample. In the absence of any measurable quantity of any other organic

carbon source, this method provides a way of reliably measuring dpm at

concentrations at and below the proposed final concentration limit.

MSHA has also evaluated other analytical approaches--the

gravimetric method (simply weighing the sample), the respirable

combustible dust (RCD) analysis used in Canada, and the elemental

carbon approach. As discussed in detail in Part II, use of these

methods to measure dpm for compliance purposes in underground metal and

nonmetal mines present various questions that the Agency has not been

able to satisfactorily address at point in the rulemaking process. For

example, the gravimetric method has not been validated for use at lower

concentration levels, the RCD method is not recommended for use in

certain types of underground metal and nonmetal mines, and there

appears to be some variability in the relationship between elemental

carbon and whole diesel particulate.

MSHA does not believe that either oil mists or cigarette smoke in

underground metal or nonmetal mines will pose a problem in using this

method. MSHA currently has no data as to the frequency of occurrence or

the magnitude of any

[[Page 58117]]

potential interference from oil mist, but during its studies of

measurement methods in underground mines, MSHA has not encountered

situations where oil mist was found to be an interferant. Moreover, the

Agency assumes that when operators implement the proposal's maintenance

requirements, this will minimize any remaining potential for such

interference. Cigarette smoking can be prohibited by an operator during

any testing. MSHA welcomes comments as to the scope of any possible

interferences with the proposed methods and measures for addressing

them.

Proposed Sec. 57.5061(a) would explicitly provide that MSHA use the

validated NIOSH procedure for total carbon, or ``any method

subsequently determined by NIOSH to provide equal or improved

accuracy'' in underground metal and nonmetal mines. Measurement

technology is always improving, and MSHA believes that providing for

some flexibility in this regard can ultimately benefit the entire

mining community.

Proposed Sec. 57.5061(b) provides that a single sample using the

prescribed method would provide an adequate basis for citing

noncompliance. As with the sampling methodology, MSHA is proposing to

specifically state this policy as a provision of the rule itself to

ensure it is clearly understood. Single shift sampling is the normal

practice for OSHA and MSHA. As is its practice with other compliance

determinations based on measurement, MSHA would not issue a citation

unless the measurement exceeds the compliance limit by a ``margin of

error'' sufficient to demonstrate noncompliance at a 95% confidence

level. While MSHA is still conducting research to determine exactly

what margin of error would be appropriate to establish such a

confidence level, the Agency expects it to be between 10 and 20% of the

concentration limit. Thus, assuming for the sake of example that the

margin of error is 15%, a citation would not be issued for exceeding

the final concentration limit unless the measured total carbon is above

184TC g/m\3\ (115% of 160TC g/

m\3\).

Finally, it should be noted that the proposed limit is expressed in

terms of the average airborne concentration during each full shift

expressed as an 8-hour equivalent. Measuring during the full shift

ensures that the entire exposure is monitored, and the limit is based

on the average exposure. Using an 8-hour equivalent ensures that a

miner who works extended shifts would not have a higher exposure burden

than a miner who works an 8-hour shift.

(13) Would the Concentration Limit Apply in All Areas of an Underground

Metal or Nonmetal Mine?

The concentration limit would apply only in underground areas where

miners normally work or travel. The purpose of this restriction is to

ensure that mine operators do not have to monitor particulate

concentrations in areas where miners do not normally work or travel--

e.g., abandoned areas of a mine.

However, it should be noted that the proposed interim and final

concentration limits would apply in any area of a mine where miners

``normally'' work or travel--not just where miners might be present at

the moment.

(14) Does the Rule Contemplate That MSHA Use Area Sampling To Determine

Compliance?

The limit on the concentration of diesel particulate to which

miners are exposed is intended to be applicable to persons, occupations

or areas. This means that the Agency may sample by attaching a sampler

to an individual miner, locate the sampler on a piece of equipment

where a miner may work, or locate the sampler at a fixed site where

miners normally work or travel.

(15) What Is the Basis for the Concentration Limit Being Proposed in

Underground Metal and Nonmetal Mines?

The proposed rule would seek to reduce exposures to dpm in

underground areas of underground metal and nonmetal mines to a level of

around 200DPM g/m\3\. (As explained in response to

Question 12, the concentration limit is being expressed in terms of the

total carbon measurement system MSHA will use to determine the amount

of dpm, 160TC

g/m\3\).

Look again at Figure I-1, which compares the range of exposures of

different groups of workers. You can see that capping dpm

concentrations at 200DPM g/m\3\ (all the

information on the figure is presented in terms of estimated whole

diesel particulate) will eliminate the worst mining exposures. In fact,

such a cap will bring miner exposures down to a level commensurate with

those reported for other groups of workers who use diesel-powered

equipment. The proposed rule would not bring concentrations down as far

as the proposed ACGIH TLVR of 150DPM g/

m\3\. Nor does MSHA's risk assessment suggest that the proposed rule

would eliminate the significant risks to miners of dpm exposure.

As a result of the Agency's statutory obligation to attain the

highest degree of safety and health protection for miners, the Agency

explored the option, and implications, of requiring mines in this

sector to comply with a lower concentration limit than that being

proposed. The Agency looked at simulations of the controls some

underground metal and nonmetal mines might use to lower dpm

concentrations, including at least one control with a major cost

component (aftertreatment filter or new engine). The results, discussed

in Part V of this preamble, indicate that although the matter is not

free from question, it may not be feasible at this time for the

underground metal and nonmetal mining industry as a whole to comply

with a significantly lower limit than that being proposed. More

information on this issue, and comments of the information presented by

the Agency in Part V, would be appreciated.

The other side of this question--whether the rule that is proposed

is feasible for the underground metal and nonmetal mining industry--is

discussed in the next Question and Answer.

(16) Is It Feasible for the Metal and Nonmetal Industry as a Whole To

Comply with the Proposed Concentration Limit?

MSHA has evaluated the feasibility of the concentration limit in

the underground metal and nonmetal sector. Approximately 78 percent, of

the 261 underground metal and nonmetal mines use diesel powered

equipment, and MSHA estimates this sector has approximately 4,100

diesel engines. The engines can be of large size, and so tend to have

high emissions. Moreover, unlike in the coal sector, there is no single

control device that can be readily and widely applied to reduce dpm

emissions in underground metal and nonmetal mines. The paper filter

aftertreatment devices that can eliminate up to 95% of particulate

matter emissions from permissible coal equipment are not available here

without the addition of other controls. Permissible equipment requires

the exhaust to be cooled to avoid explosive hazards; in turn, this

permits paper afterfilters to be installed directly without burning.

For most metal and nonmetal equipment, it is necessary to first install

water scrubbers or other devices to cool the exhaust before using the

paper filters. There are other types of filtering devices that could be

directly applied to this equipment, but none to date that is quite as

effective (although MSHA is seeking information as to whether creation

of a market for filters could lead to prompt commercial development of

ceramic filters with

[[Page 58118]]

high particulate removal efficiencies). Moreover, the ventilation

systems common in this sector, and the variation of mine types,

suggested that a careful feasibility review is warranted.

Accordingly, MSHA undertook special analyses in which the Agency's

staff experts simulated how various control methods could be used to

meet the needs of some mines expected to have unusually difficult

problems: an underground limestone mine, an underground (and

underwater) salt mine, and an underground gold mine. The results of

these analyses are discussed in Part V of the preamble, together with

the methodology used in modeling the results. In each case, the

analysis revealed that there are available controls that can bring dpm

concentrations down to well below the final limit--even when the

controls that needed to be purchased were not as extensive as those

which the Agency is assuming will be needed in determining the costs of

the proposed rule. As a result of these studies, the Agency has

tentatively concluded that, in combination with the required ``best

practices'', there are engineering and work practice controls available

to bring dpm concentrations in all underground metal and nonmetal mines

down to 400TC g/m\3\ within 18 months. Moreover,

based on the mines it has examined to date, MSHA has tentatively

concluded that controls are available to bring dpm concentrations in

all underground metal and nonmetal mines down to 160TC

g/m\3\ within 5 years.

The Agency would welcome comments from the mining community on the

methodology of the model used in these studies, and hopes the mining

community will submit the actual results of its own studies using the

model. More information on the model is contained in Part V of the

preamble. It uses a spreadsheet template that can be run on standard

programs, and MSHA would be pleased to make copies available and answer

any questions about the use of the model.

The best actions for an individual operator to take to come into

compliance with the interim and final concentration limits will depend

upon an analysis of the unique conditions at the mine. The proposed

rule provides 18 months after it is promulgated for MSHA to provide

technical assistance to individual mine operators. It also gives all

mine operators in this sector an additional three and a half years to

bring dpm concentrations down to the proposed final concentration

limit--using an interim concentration limit during this time which the

Agency is confident every mine in this sector can timely meet. And the

rule provides an opportunity for a special extension for an additional

two years for mines that have unique technological problems meeting the

final concentration limit.

As noted during 1995 workshops co-sponsored by MSHA on methods for

controlling diesel particulate, many underground metal and nonmetal

mine operators have already successfully determined how to reduce

diesel particulate concentrations in their mines. MSHA has disseminated

the ideas discussed at these workshops to the entire mining community

in a publication, ``Practical Ways to Control Exposure to Diesel

Exhaust in Mining--a Toolbox'' (a copy of this publication is appended

to the end of this document). The control methods are divided into

eight categories: use of low emission engines; use of low sulfur fuel;

use of aftertreatment devices; use of ventilation; use of enclosed

cabs; diesel engine maintenance; work practices and training; fleet

management; and respiratory protective equipment. And as noted above,

MSHA has designed a model in the form of a computer spreadsheet that

can be used to simulate the effects of various controls on dpm

concentrations. This model is discussed in Part V of the preamble, and

several examples are provided. This makes it possible for individual

underground mine operators to evaluate the impact on diesel particulate

levels of various combinations of control methods, prior to making any

investments, so each can select the most feasible approach for his or

her mine.

(17) Suppose an Underground Metal or Nonmetal Mine Really Does Have a

Unique Technological Problem That Precludes Timely Compliance? Will

MSHA Utilize Qualified and Experienced Technical Personnel To Review

Operator Applications for Special Extensions of Time To Comply With the

Final Concentration Limit in Underground Metal and Nonmetal Mines?

It is MSHA's intent that primary responsibility for analysis of the

operator's application for a special extension will rest with MSHA's

district managers. District managers are the most familiar with the

conditions of mines in their districts, and have the best opportunity

to consult with miners as well. At the same time, MSHA recognizes that

district managers may need assistance with respect to the latest

technologies and solutions being used in similar mines elsewhere in the

country. Accordingly, the Agency intends to establish within its

Technical Support directorate in Arlington, Va., a special panel to

consult on these issues, to provide assistance to district managers,

and to give final approval of any application for a special extension.

(18) If a Special Extension of Time To Comply With the Final dpm

Concentration Limit Is Approved for an Underground Metal or Nonmetal

Mine, What Operating Parameters Would Be Imposed on That Mine during

the Duration of the Special Extension?

Any parameters will be negotiated between the individual operator

and MSHA.

An operator will begin the process by filing an application for a

special extension. The application must set forth what actions the

operator commits to taking to maintain the lowest concentration of

diesel particulate achievable. The application must also include

adequate information for the Secretary to ascertain the lowest

concentration of diesel particulate achievable, as demonstrated by data

collected under conditions that are representative of mine conditions

using the total carbon sampling method. In addition, the application

must set forth what actions the operator will take to minimize the

exposure of miners who will have to work or travel in areas which are

going to be above the concentration limit by virtue of the extension.

Since administrative controls and personal protective equipment can

help reduce miner exposure, under these special circumstances operators

may propose to include use of these approaches in their applications.

In some cases, what may be involved is a small area with only

limited miner access; in other cases, an entire working section may be

involved. Rather than establish ``one-size-fits-all'' standards for

such situations, the proposal leaves it to the operator to submit a

suggested approach.

The proposed rule requires a mine operator to comply with the terms

of an approved extension application, and a copy would be posted at the

mine site. Failure to comply with the specific commitments agreed to as

part of the extension, and contained therein, would thus be citable.

(19) Why Do Underground Metal and Nonmetal Mine Operators Have To Have

a Diesel Particulate Control Plan?

Underground metal and nonmetal operators will not have to have a

compliance plan if they are in compliance. Considerable time is

provided under the proposed rule to come into compliance, and operators

can thereafter monitor their mines to

[[Page 58119]]

ensure they stay below the required concentration limit.

But some operators may decline to take the actions necessary to

achieve compliance in a timely manner, and others may need to rethink

their approaches from time to time as equipment changes increase dpm

concentration levels. Providing for a control plan in the event of a

violation of the concentration limit ensures that there is a

deliberative effort as to how to solve the dpm concentration problem,

and that everybody understands what is going to be done to eliminate

it. Accordingly, proposed Sec. 57.5062 requires that in the event an

operator is determined to have exceeded the applicable limit on diesel

particulate concentration, the operator must establish a diesel

particulate control plan if one is not already in effect, or modify the

existing diesel particulate control plan.

(20) Must dpm Control Plans in Metal and Nonmetal Mines Be Pre-Approved

by MSHA? How Long Would They Last?

Operator control plans would NOT have to be approved by MSHA. This

is consistent with the practice in this sector concerning ventilation

plans (with which the dpm control plan may be combined). The Agency

gave serious consideration to requiring approval of such plans to

ensure there was agreement as to their effectiveness, or at least to

approval of compliance plans for repeat violators; but in light of the

resource demands this might impose on the agency, and the operator

verification sampling built into the proposed rule, the Agency decided

not to make such a proposal. Comment on this point is welcome.

A control plan for a metal or nonmetal mine would not need to be

retained and modified forever--as is the practice with plans for

underground coal mines. Rather, under the proposal, a dpm control plan

in a metal or nonmetal mine would stay in effect for 3 years, and

during its lifetime, the plan is to be modified as appropriate to

reflect changes in mining conditions.

MSHA seriously considered requiring a longer lifetime for

compliance plans. First, the Agency wants to provide a strong incentive

to come into compliance in a timely fashion. Second, the Agency wants

to be sure that where a plan is needed to clarify compliance

obligations, it stay in place at a mine long enough to ensure that the

obligations undertaken in the plan become a mine routine; the goal is

to maintain a mine in compliance, not just have a temporary fix. The

Agency also has to be realistic about conserving the resources of its

health professionals; re-sampling mines whose control plans have

expired takes resources away from other priorities. The Agency is

aware, however, that operating under long-term control plans is not

standard practice in metal and nonmetal mines. Moreover, it recognizes

the need to re-sample all mines with some regularity due to changing

mining conditions. Accordingly, the proposed rule seeks to strike a

balance in this regard.

(21) What Must Be Included in a dpm Control Plan If One Is Required?

And How Would Its Effectiveness Be Verified?

The diesel particulate control plan would include three elements:

the controls the operator will utilize to maintain the concentration of

diesel particulate at the mine to the applicable limit; a list of

diesel-powered units maintained by the mine operator; and information

about any unit's emission control device and the parameters of any

other method used to control dpm concentrations. Upon request, the plan

(or amended plan) is to be submitted to the District Manager, with a

copy to the authorized representative of miners--but no approval

process would be required; a copy is to be maintained at the mine site.

Documentation verifying the effectiveness of the plan in controlling

diesel particulate to the required level would have to be maintained

with the plan, and submitted to MSHA upon request.

Proposed Sec. 57.5062(c) provides that to verify the effectiveness

of a control plan or amended control plan, operators must have

monitoring data, collected using the total carbon method which MSHA

will be required to use for enforcement purposes, sufficient to confirm

that the plan or amended plan will control the concentration of diesel

particulate to the applicable limit under conditions that can be

reasonably anticipated in the mine.

Verification by operators is being proposed to ensure that primary

responsibility for ensuring a dpm control plan is effective is not

shifted to MSHA. The Agency has only limited resources to conduct

sampling. Moreover, while a single sample can demonstrate that a mine

is out of compliance under the conditions sampled, it takes multiple

samples to demonstrate that miners are protected under the variety of

conditions that can be reasonably anticipated in the mine (e.g., during

production and seasonal changes). By clarifying operator

responsibilities in this regard, the proposal ensures an appropriate

balance of responsibilities.

The proposed rule does not specify that any defined number of

samples must be taken--the intent is that the sampling provide a

representative picture of whether the plan or amended plan is working.

The proposed rule does, however, specify that the total carbon method

be used for verification sampling. This is an exception to the general

rule that mine operators have discretion in the choice of what sampling

technique to use in their own monitoring programs (see response to

Question 29). The purpose of verification sampling is to verify the

effectiveness of a plan established or modified in response to a

violation through MSHA sampling; if operators used an alternative

technique to sample, it would complicate the determination of whether

the violation was being adequately addressed by the plan.

(22) Why Is the Agency Proposing That All Underground Metal and

Nonmetal Mines Follow Certain ``Best Practices''--Regardless of the

Concentration of Diesel Particulates at Such Mines?

The Agency's risk assessment supports reduction of dpm to the

lowest level possible. But as discussed in response to Question 16,

feasibility considerations dictated proposing a concentration limit

that does not eliminate the significant risks that dpm exposure poses

to miners.

One approach that can be used to bridge the gap between risk and

feasibility is to establish an ``action level''. In the case of MSHA's

noise proposal, for example, MSHA proposed a ``permissible exposure

level'' of a time-weighted 8-hour average (TWA8) of 90 dBA

(decibels, A-weighted), and an ``action level'' of half that amount--a

TWA8 of 85 dBA. In that case, MSHA has determined that

miners are at significant risk of material harm at a TWA8 of

85 dBA, but technological and feasibility considerations may preclude

the industry as a whole, at this time, from eliminating exposures below

a TWA8 90 dBA. Accordingly, MSHA proposed that mine

operators must take certain actions to limit miner exposure to noise

above a TWA8 of 85 dBA that are feasible (e.g., provide

hearing exams and hearing protectors).

MSHA considered the establishment of a similar ``action level'' for

dpm--probably at half the proposed concentration limit, or

80TC g/m3. Under such an approach, mine

operators whose dpm concentrations are above the ``action level'' would

be required to implement a series of ``best practices''--e.g., limits

on fuel types, idling, and engine maintenance. MSHA welcomes comments

on whether it

[[Page 58120]]

should take such an approach with dpm.

In lieu of this approach, the Agency decided instead to propose an

approach that it believes will be simpler for the mining community to

implement: requiring compliance with the ``best practices'' in all

cases. There are several reasons why the agency has proposed this

approach.

First, sampling by both operators and MSHA would have to be much

more frequent if a measurement trigger for additional actions were to

be established. This is because many more areas of a mine would need to

be checked regularly than if only a higher trigger is in place. In

underground metal and nonmetal mines, most areas using diesel equipment

would exceed a limit of 75TC g/m3

anyway, so the sampling needed to confirm the situation would appear to

be wasteful.

Second, diesel equipment is often moving, meaning that maintenance

and fleet requirements triggered by a single sample might switch on and

off in ways that are hard to predict. Moreover, using an action level

in an area of a mine to trigger maintenance requirements might put

certain machines in the fleet under one set of maintenance rules and

other machines under an alternative set, complicating mine

administration.

Third, underground coal mines which use diesel-powered equipment

already observe a set of such requirements. While certain special

safety hazards associated with the use of diesel-powered equipment in

underground coal mines warrant certain work practices that may not be

warranted in other sectors, the safety rationale for adopting some of

these practices seems as valid in other sectors as in underground coal.

Fourth, given the history of the mining industry with lung problems

associated with this type of work, adopting a prudent approach seems a

wise course when the costs of prevention are limited. This is standard

health practice.

Finally, a number of the work practices proposed appear to have

significant benefits--improving the efficiency of mining operations by

ensuring that diesel mining equipment is maintained in good working

order to meet productivity demands.

MSHA specifically solicits comments from the public on whether or

not it should require ``best practices'' to lower the dpm

concentration.

(23) Will the Proposed Restrictions on Fuel and Fuel Additives Increase

Costs or Limit Engine Reliability?

MSHA believes the answer to both questions is no.

Under proposed Sec. 57.5065, mine operators would be able to use

only low-sulfur diesel fuel. This requirement is identical to that for

underground coal diesel equipment. Number 1 and number 2 diesel fuel

would be permitted. MSHA has been advised that low-sulfur diesel fuel

is now readily available in all areas of the country in order to meet

EPA requirements; in many places, it is the only fuel available.

Similarly, the proposal would extend to all mines the ban in

underground coal mines on the use of diesel-fuel additives other than

those approved by EPA. There is a long list of approved additives.

Copies are available from EPA and the list is posted on its Web site,

or you may link to them from MSHA's Web site (http://www.msha.gov/

s&hinfo/deslreg/1901(c).htm). Using only additives that have been

approved ensures that diesel particulate concentrations are not

inadvertently increased, while also protecting miners against the

emission of other toxic substances.

(24) How Is MSHA Going To Distinguish Between Idling That Is Permitted

and Idling That Isn't Permitted?

Keeping idling to a minimum is a very important way to reduce

pollution in mine atmospheres, and this would be required by proposed

Sec. 57.5065(c). Idling engines can actually produce more pollutants

than engines under load. Generally of more concern, however, is the

impact idling engines can have on localized exposures. In underground

operations, an engine idling in an area of minimal ventilation or a

``dead air'' space could cause an excess exposure to the gaseous

emissions, especially carbon monoxide, as well as to diesel

particulate. Eliminating unnecessary idling can make a substantial

contribution toward preventing localized exposure to high particulate

concentrations.

However, there are some circumstances in which idling is necessary.

The proposal would permit idling in connection with ``normal mining

operations''. In the proposal, MSHA does not attempt to define this

term, and would intend this rule to be administered with reference to

commonly understand practices of what is necessary idling. For example,

idling while waiting for a load to be unhooked, or waiting in line to

pick up a load, is normally part of the job; idling while eating lunch

is normally not part of the job. But if the idling is necessary due to

the very cold weather conditions, it should not be barred. On the other

hand, idling should not be permitted in other weather conditions just

to keep balky older engines running; in such cases, the correct

approach is better maintenance. MSHA recognizes that to administer this

provision in a common sense manner may require the provision of

examples to both MSHA inspectors and to the mining community;

accordingly, the Agency welcomes specific examples of circumstances

where idling should and should not be permitted. The Agency recently

implemented a similar provision for the underground coal mining sector,

and MSHA will consider the experience gained under that rule in

formulating a final diesel particulate rule and compliance guide.

(25) Will the Proposed Rule Require That Diesel Engines and

Aftertreatment Devices Used in Underground Metal and Nonmetal Mines Be

Maintained in Mint Condition?

No. Sec. 57.5066(a) of the proposed rule would, however, require

that the engines and aftertreatment devices not be permitted to

deteriorate to the point they create needless pollution. The air intake

system, the cooling system, lubrication system, fuel injection system

and exhaust system of an engine must all be maintained on a regular

schedule if the toxic contaminants in the engine exhaust are to be

minimized. And there is little point in having an aftertreatment device

to limit pollution if it is not maintained in working order; moreover,

it can damage the engine. A good preventive maintenance program can not

only keep down exhaust emissions, but help maximize vehicle

productivity and engine life.

It is difficult for a rule covering all types and ages of engines

used in underground metal and nonmetal mines to define precisely the

level of maintenance required for each engine. Further, MSHA does not

believe that it is necessary: the mining community is fully cognizant

of the general requirements for engine maintenance. Accordingly,

proposed Sec. 57.5066(a) sets out in general terms the standard of care

required for different types of engines.

First, an ``approved'' engine is to be maintained in approved

condition. MSHA approves engines under specific regulations set forth

in Title 30. The approval of the engine is tied to certain parts and

specifications. When these parts or specifications are changed (e.g.,

an incorrect part is used, or the wrong setting), then the engine is no

longer considered in approved condition. The requirements in this

regard are well defined. MSHA personnel at the Approval Certification

Center are

[[Page 58121]]

available to the mining community to respond to questions and provide

specific guidance. MSHA's diesel equipment rule already requires

underground coal mine fleets to convert entirely to approved engines,

but at this time only some of the engines used in underground metal and

nonmetal mines are approved.

Second, for any engine that is not an approved engine, the

``emission related components'' of the engine are to be maintained to

manufacturer specifications. By the term ``emission related

components,'' MSHA means the parts of the engine that directly affect

the emission characteristics of the raw exhaust. These are basically

the same components which MSHA examines for ``approved'' engines. They

are: the piston; intake and exhaust values; cylinder head; camshaft;

injector; fuel injection pump; governor; injection timing and fuel pump

calibration; and, if applicable, turbocharger and after cooler.

Third, and finally, any emission or particulate control device

installed on diesel-powered equipment is to be maintained in

``effective operating condition.'' The maintenance of an emission or

particulate control device in effective operating condition involves

such basic tasks as regularly cleaning the filter using whatever

methods are recommended by the manufacturer for that purpose or

inserting appropriate replacement filters, checking for and repairing

any leaks, and similar obvious actions.

An MSHA inspector is not going to randomly order an engine to be

taken out of service and torn down to check the condition of a piston

against the shop manual. Rather, what will concern an inspector are the

same kinds of signals that should concern a conscientious operator--for

example, a history of complaints about the engine's reliability, an

incomplete maintenance schedule, lack of required maintenance manuals

or spare parts, the emission of black smoke under normal load, or a

series of emission test results indicating a continuing engine problem.

Evidence of such deficiencies is likely to lead to a closer

examination. But a conscientious maintenance program is going to catch

such problems before they occur.

MSHA's toolbox includes an extensive discussion of maintenance. It

reminds operators and diesel maintenance personnel of the basic systems

on diesel engines that need to be maintained, and how to avoid various

problems. It includes suggestions from others in the mining community,

and information on their success or difficulties in this regard. MSHA

will continue to provide technical assistance to the mining community

in this critical area.

(26) What Are the Responsibilities of a Miner Who Operates Diesel-

Powered Equipment in an Underground Metal and Nonmetal Mine To Ensure

it Is Not Polluting? And What Are The Responsibilities of Mine

Management When Notified of a Potential Pollution Problem?

The miner who operates diesel-powered equipment is often the first

one to spot a problem with the engine or emissions system. The engine

may balk, have trouble handling a load, make unusual noises, exhaust

too much smoke, or otherwise suggest to the person familiar with the

engine's capabilities that it needs to be checked. In some cases, the

miner may have the knowledge, parts, equipment and authority to fix the

problem on the spot. In many cases, however, the miner operating the

equipment may not have all of these. If the problem is to be addressed

promptly, it is essential the miner report it to mine management--and

that the mine management act on that report in a timely manner. If

these actions by miner and mine management are not taken, the

concentrations of diesel particulate are likely to quickly increase

without anyone being aware of the danger until the next environmental

monitoring is performed. To avoid this problem, proposed Sec. 57.5066

would require that all underground metal and nonmetal mines using

diesel equipment underground implement a few basic procedures. The

details of implementation in each mine would be at the discretion of

the mine operator.

Proposed Sec. 57.5066(b)(1) would require the mine operator to

authorize the operator of diesel-powered equipment to affix a tag to

the equipment at any time the equipment operator notes a potential

problem. Tagging provides a simple mechanism for ensuring that all mine

personnel are made quickly aware that a piece of equipment needs to be

checked by qualified service personnel. The tag may be affixed because

the equipment operator picks up a problem through a visual exam

conducted before the equipment is started (e.g., an exam pursuant to 30

CFR 57.14100), or because of a problem that comes to the attention of

the equipment operator during mining operations--e.g., black smoke

while the equipment is under normal load, rough idling, unusual noises,

backfiring, etc.

The proposal leaves the design of the tag to each mine operator,

provided that the tag can be dated. Comments are welcome on whether

some or all elements of the tag should be standardized to ensure its

purpose is met.

MSHA is not proposing that equipment tagged for such potential

emission problems be automatically taken out of service. The proposal

is not, therefore, directly comparable to a ``tag-out'' requirement

like OSHA's requirement for automatically powered machinery, nor as

stringent as MSHA's requirement to remove from service certain

equipment ``when defects make continued operation hazardous to

persons'' (see, e.g., 30 CFR 57.14100). While the emissions problem

could pose a serious health hazard for miners directly exposed, there

is no way to determine this with certainty until the equipment is

tested. Moreover, the danger is not as immediate as, for example, an

explosive hazard. Rather, proposed Sec. 57.5066(b)(2) would require

that the equipment be ``promptly'' examined by a person authorized by

the mine operator to maintain diesel equipment (the qualifications for

those who maintain and service diesel engines discussed in response to

the next question). The Agency has not tried to define the term

``promptly'', but welcomes comment on whether it should do so--in

terms, for example, of a limited number of shifts.

The proposal would require that a single log be retained of all

equipment tagged. The proposal would permit a tag to be removed after

an examination has been completed and a record of the examination

made--with the date, the name of the person making the examination, and

the action taken as a result of the examination. The presence of a tag

serves as a caution sign to miners working near the equipment, as well

as a reminder to mine management, as the equipment moves from task to

task throughout the mine. While the equipment is not barred from

service, operators would be expected to use common sense in using it in

locations in which diesel particulate concentrations are known to be

high. The records of the tagging and servicing, although basic, provide

mine operators, miners and MSHA a history that will help all of them

evaluate whether a maintenance program is being effectively

implemented.

[[Page 58122]]

(27) Must Miners or Others Who Examine or Repair Diesel Engines Used in

Underground Metal and Nonmetal Mines Have Special Qualifications or

Training? Must Operators Establish Programs or Criteria for This

Purpose?

The answer to the first question is a qualified ``yes'', and the

answer to the second question is no.

Proposed Sec. 57.5066(c) provides that: ``Persons authorized by a

mine operator to maintain diesel equipment covered by paragraph (a) of

this section must be qualified, by virtue of training or experience, to

ensure that the maintenance standards of paragraph (a) of this section

are observed.'' As discussed in response to Question 25, paragraph (a)

of Sec. 57.5066 provides that approved engines be maintained in

approved condition, the emission related components of non-approved

engines be maintained to manufacturer specifications, and emission or

particulate control devices installed on the equipment be maintained in

effective condition.

This means that regardless of who identifies a potential problem

along these lines, the person who checks out the problem, and if

necessary makes repairs, is someone who knows what he or she is doing.

If examining and, if necessary, changing a filter or air cleaner is

what is needed, a miner who has been shown how to do these tasks would

be ``qualified by virtue of training or experience'' to do those tasks.

For more sophisticated work, more sophisticated training or additional

experience would be required. Training by a manufacturer's

representative, completion of a general diesel engine maintenance

course, or practical experience performing such repairs might be

evidence of appropriate qualifications.

In the underground coal sector, MSHA requires each operator to

establish a program to ensure that persons who work on diesel engines

are qualified. That is not being proposed for the underground metal and

nonmetal sector. The unique conditions in underground coal mines

require the use of specialized equipment. Accordingly, the

qualifications of the persons who maintain this equipment generally

must be more sophisticated than in other sectors.

The proposed rule contemplates that if MSHA finds a situation where

maintenance appears to be shoddy or where tampering has damaged engine

approval status or emission control effectiveness, MSHA will ask the

operator to provide evidence that the person who worked on the

equipment was properly qualified by virtue of training or experience.

Equipment sent off site for maintenance and repair is just as subject

to this requirement as other equipment; it is the operator's obligation

to ensure he has appropriate evidence of the qualifications of those

who will work on the equipment.

(28) Can Underground Metal and Nonmetal Operators Continue To Use and

Relocate Nonapproved Engines in Their Inventories?

Pursuant to MSHA's diesel equipment rule, the entire fleet of

underground coal engines must be ``approved'' engines by the year

2000--even if operators must replace existing engines to comply. By

contrast, proposed Sec. 57.5067 would only require that, with a few

exceptions, all engines ``introduced'' into underground areas of

underground metal and nonmetal mines after the effective date must be

engines that have been through MSHA's approval process under Part 7 of

Chapter 30. Operators who have significant investments in their

existing fleets will accordingly be able to retain those engines,

provided they are maintained in the manner specified in the proposal

and that the concentration of diesel particulate can be controlled in

another way (e.g. ventilation, particulate filters, etc.).

However, after the rule's effective date, an operator would not be

permitted to bring into underground areas of a mine an unapproved

engine from the surface area of the same mine, an area of another mine,

or from a non-mining operation. Since the safe level of diesel

particulate is not known, promoting a gradual turnover of the existing

fleet is an appropriate response to the health risk presented.

Some engines currently used in metal and nonmetal mines may have no

approval criteria; in such cases, MSHA will work with the manufacturers

to develop approval criteria consistent with those MSHA uses for other

diesel engines. Based upon preliminary analysis, MSHA has tentatively

concluded that any diesel engine meeting current on-highway and non-

road EPA emission requirements would meet MSHA's engine approval

standards of Part 7, subpart E, category B type engine. (See Section 4

of Part II of this preamble for further information about these

engines). Currently, the EPA nonroad test cycle and MSHA's test cycle

are the same for determining the gaseous and particulate emissions.

MSHA envisions being able to use the EPA test data ran on the non-road

test cycle for determining the gaseous ventilation rate and particulate

index. The engine manufacturer would continue to submit the proper

paper work for a specific model diesel engine to receive the MSHA

approval. However, engine data ran on the EPA on-highway transient test

cycle would not as easily be usable to determine the gaseous

ventilation and particulate index. Comments on how MSHA can facilitate

review of engines not currently approved would be welcome.

Engines in diesel-powered ambulances and fire-fighting equipment

would be exempted from these requirements. This exemption is identical

with that in the rule for diesel-powered equipment in underground coal

mines.

(29) What Specifically Would Be the Obligations of an Underground Metal

or Nonmetal Mine Operator To Monitor dpm Exposures and to Correct

Overexposures?

Proposed Sec. 57.5071 would require underground metal or nonmetal

mine operators to monitor the concentration of diesel particulate, to

initiate corrective action by the next work shift if the monitoring

reveals that the concentration of diesel particulate exceeds the

permitted limit, and to post sample results and the corrective action

being taken.

There is no prescribed frequency for monitoring. But proposed

Sec. 57.5071(a) provides that sampling must be done as often as

necessary to ``effectively evaluate,'' under conditions that can be

reasonably anticipated in the mine:

(1) whether the dpm concentration in any area of the mine where

miners work or travel exceeds the applicable limit; and (2) the average

full shift airborne concentration at any location or on any person

designated by MSHA. The first condition clarifies that it is the

responsibility of mine operators to be aware of the concentrations of

diesel particulate in all areas of the mine where miners work or

travel, so as to know whether action is needed to ensure that the

concentration does not exceed the applicable limit. The second

condition is to ensure special attention to locations or persons known

to MSHA to have a significant potential for overexposure to diesel

particulate.

The proposed rule is performance oriented in that the regularity

and methodology used to make this evaluation are not specified. MSHA's

own measurements will assist the Agency in verifying the effectiveness

of an operator's monitoring program. If an operator is ``effectively

evaluating'' the concentration of dpm at designated locations, for

example, MSHA would not expect to record concentrations above the limit

when it samples at that

[[Page 58123]]

location. Some record of the sampling procedure and sample results will

need to be retained by operators to establish that they have complied

with the general obligations of this section.

The proposed rule requires, consistent with Section 103(c) of the

Mine Act, that miners and their representatives have an opportunity to

observe such monitoring. In accordance with this legal requirement, the

proposed rule requires a mine operator to provide affected miners and

their representatives with an opportunity to observe exposure

monitoring of dpm by operators. Mine operators must give prior notice

to affected miners and their representatives of the date and time of

intended monitoring. MSHA has proposed similar language in its proposed

rule on noise.

The proposed rule does not specify a required method for sampling.

In the absence of a procedure to convert total carbon measurements into

equivalents under other methods, methods other than NIOSH Method 5040

would not provide exact information about compliance status, but they

certainly would provide a general guide to dpm concentrations if used

under proper circumstances. (More information on the proper

circumstances in which various methods are appropriate can be found in

Section 3 of Part II of this preamble).

The proposed rule provides that an operator who has knowledge that

a concentration limit has been exceeded must initiate corrective action

by the next work shift and promptly complete such action. The hazards

presented by overexposure to dpm may not as immediate as an explosive

hazard, but are nevertheless serious. Accordingly, although MSHA is not

proposing immediate withdrawal of miners nor even immediate completion

of abatement action, the agency is proposing that mine operators begin

abatement action by the next shift and promptly complete such action,

not allowing it to drag out while miners are being overexposed. The

Agency is also proposing to require posting of the corrective action to

implement the statutory requirement that notice of corrective action be

provided to miners. MSHA welcomes comment on how it might clarify its

expectations with respect to the initiation of corrective action,

including what specific guidance to provide to operators not using the

total carbon method and as to when corrective action must begin when

the analysis is performed on a delayed basis off-site. MSHA also

welcomes comment as to whether personal notice of corrective action

would be more appropriate than posting given the health risks involved.

Proposed Sec. 57.5071(d) provides that monitoring results must be

posted on the mine bulletin board, and a copy provided to the

authorized representative of miners. As with the training requirements,

posting ensures that miners are kept aware of the hazard so they can

actively play their role in prevention.

(30) What Records Must be Kept by Metal and Nonmetal Operators? Where

Must they be Kept, and Who Has Access to Them?

Recordkeeping and retention requirements are noted in the text of

each section of the proposed rule creating the requirement. For the

sake of convenience, a table of record-keeping requirements is provided

in proposed Sec. 57.5075(a). The table lists the records that would be

required under the proposed changes to Part 57, notes the proposed

section of Part 57 creating the recordkeeping requirement, and notes

the type of record and retention time. MSHA would welcome comment on

whether this presentation is useful.

In some cases, the record required is expressed in general terms:

e.g., ``evidence of competence to perform maintenance'', pursuant to

proposed Sec. 57.5066(c). As long as each operator has some record that

establishes this fact, it does not matter that the records of one

operator are not the same as the records of another operator. While an

MSHA inspector may well be willing to accept oral evidence on a

particular point (e.g., who performed a repair), operators should

retain written documentation adequate to demonstrate the facts involved

(e.g., a logbook for each engine showing who worked on it, the date,

the work performed, and any follow-up needs or plans). MSHA would

welcome comments on whether the agency should be more specific as to

the recordkeeping systems mine operators should utilize.

The proposed rule generally provides that records required be

retained at the mine site. These records need to be where an inspector

can view them during the course of an inspection, as the information in

the records may determine how the inspection proceeds. But if the mine

site has an operative fax machine or computer terminal, this section

would permit the records to be maintained elsewhere. MSHA's approach in

this regard is consistent with Office of Management and Budget Circular

A-1. Mine operators must promptly provide access to compliance records

upon request from an authorized representative of the Secretary of

Labor, the Secretary of Health and Human Services, or from the

authorized representative of miners. Access to a miner's sample records

must also be provided to a miner, former miner, or personal

representative of a miner--the first copy at no cost, and any

subsequent copies at reasonable cost.

MSHA encourages mine operators who store records electronically to

provide a mechanism which will allow the continued storage and

retrieval of records in the year 2000.

II. Background Information.

This part provides the context for this rulemaking. The nine topics

covered are:

(1) The role of diesel-powered equipment in mining;

(2) Diesel exhaust and diesel particulate;

(3) Methods available to measure dpm;

(4) Reducing soot at the source--engine standards;

(5) Limiting the public's exposure to soot--ambient air quality

standards;

(6) Controlling diesel particulate emissions in mining--a Toolbox;

(7) Existing mining standards that limit miner exposure to

occupational diesel particulate emissions;

(8) How other jurisdictions are restricting occupational exposure

to diesel soot; and

(9) MSHA's initiative to limit miner exposure to diesel

particulates--the history of this rulemaking and related actions.

In addition, a recent MSHA publication, ``Practical Ways to Reduce

Exposure to Diesel Exhaust in Mining--A Toolbox'', contains

considerable information of interest in this rulemaking. The

``Toolbox'' which includes additional information on methods for

controlling dpm, and a glossary of terms, is appended to the end of

this document.

These topics will be of interest to the entire mining community,

even though this rulemaking is specifically confined to the underground

metal and nonmetal sector.

(1) The Role of Diesel-Powered Equipment in Mining. Diesel engines

now power a full range of mining equipment on the surface and

underground, in both coal and in metal/nonmetal mining. Many in the

mining industry believe that diesel-powered equipment has a number of

productivity and safety advantages over electrically-powered equipment.

Nevertheless, concern about miner safety and health has slowed the

spread of this technology, and in certain states resulted in a complete

ban on its use in

[[Page 58124]]

underground coal mines. As the industry has moved to realize the

advantages this equipment may provide, the Agency has endeavored to

address the miner safety and health issues presented.

Historical Patterns of Use. The diesel engine was developed in 1892

by the German engineer Rudolph Diesel. It was originally intended to

burn coal dust with high thermodynamic efficiency. Later, the diesel

engine was modified to burn middle distillate petroleum (diesel fuel).

In diesel engines, liquid fuel droplets are injected into a prechamber

or directly into the cylinder of the engine. Due to compression of air

in the cylinder the temperature rises high enough in the cylinder to

ignite the fuel.

The first diesel engines were not suited for many tasks because

they were too large and heavy (weighing 450 lbs. per horsepower). It

was not until the 1920's that the diesel engine became an efficient

lightweight power unit. Since diesel engines were built ruggedly and

had few operational failures, they were used in the military, railway,

farm, construction, trucking, and busing industries. The U.S. mining

industry was slow, however, to begin using these engines. Thus, when in

1935 the former U.S. Bureau of Mines published a comprehensive overview

on metal mine ventilation (McElroy, 1935), it did not even mention

ventilation requirements for diesel-powered equipment. By contrast, the

European mining community began using these engines in significant

numbers, and various reports on the subject were published during the

1930's. According to a 1936 summary of these reports (Rice, 1936), the

diesel engine had been introduced into German mines by 1927. By 1936,

diesel engines were used extensively in coal mines in Germany, France,

Belgium and Great Britain. Diesel engines were also used in potash,

iron and other mines in Europe. Their primary use was in locomotives

for hauling material.

It was not until 1939 that the first diesel engine was used in the

United States mining industry, when a diesel haulage truck was used in

a limestone mine in Pennsylvania. In 1946 diesel engines were

introduced in coal mines. Today, however, diesel engines are used to

power a wide variety of equipment in all sectors of U.S. mining, such

as: air compressors; ambulances; crane trucks; ditch diggers; foam

machines; forklifts; generators; graders; haul trucks; load-haul-dump

machines; longwall retrievers; locomotives; lube units; mine sealant

machines; personnel cars; hydraulic pump machines; rock dusting

machines; roof/floor drills; shuttle cars; tractors; utility trucks;

water spray units and welders.

Estimates of Current Use. Estimates of the current inventory of

diesel engines in the mining industry are displayed in Table II-1. Not

all of these engines are in actual use. Some may be retained rather

than junked, and others are spares. MSHA has been careful to take this

into account in developing cost estimates for this proposed rule; its

assumptions in this regard are detailed in the Agency's PREA.

Table II-1.--Diesel Equipment in Three Mining Sectors

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

# Mines w/

Mine type # Mines \2\ diesel # Engines

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

Underground Coal................. 971 \3\ 173 \4\ 2,950

Small \1\.................... 426 15 50

Large........................ 545 158 2,900

Underground M/NM................. 261 203\5\ \6\ 4,100

Small \1\.................... 130 82 625

Large........................ 131 121 3,475

Surface Coal..................... 1,673 \7\ 1,673 \8\ 22,000

Small \1\.................... 1,175 1,175 7,000

Large........................ 498 498 15,000

Surface M/NM..................... 10,474 \9\ 10,474 \10\ 97,000

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

Notes on Table II-1:

(1) A mine with less than 20 miners. MSHA traditionally regards mines

with less than 20 miners as ``small'' mines, and those with 20 or more

miners as ``large'' mines based on differences in operation. However,

in examining the impact of the proposed regulations on the mining

community, MSHA, consistent with the Small Business Administration

definition for small mines, which refers to employers with 500

employees or less, has analyzed impact for this size. This is

discussed in the Agency's preliminary regulatory economic analysis for

this proposed rule.

(2) Preliminary 1996 MSHA data.

(3) Data from MSHA approval and certification center, Oct. 95.

(4) Actual inventory, rounded to nearest 50.

(5) Estimates are based on a January 1998 count, by MSHA inspectors, of

underground mines that use diesel powered equipment.

(6) The estimates are based on a January 1998 count, by MSHA inspectors,

of diesel powered equipment normally in use.

(7) Based on assumption that all surface coal mines had some diesel

powered equipment.

(8) Based on MSHA inventory of 25% of surface coal mines.

(9) MSHA assumes all surface M/NM mines use some diesel engines.

(10) Derived by applying ratios (engines per mine) from MSHA inventory

of surface coal mines to M/NM mines.

As noted in Table II-1, a majority of underground metal and

nonmetal mines, and all surface mines, use diesel-powered equipment.

This is not true in underground coal mines--in no small measure

because, as discussed later in this part, several key underground coal

states have for many years banned the use of diesel-powered equipment

in such mines.

Neither the diesel engines nor the diesel-powered equipment are

identical from sector to sector. This relates to the equipment needs in

each sector. This is important information because the type of engine,

and the type of equipment in which it is installed, can have important

consequences for particulate production and control.

As the horsepower size of the engine increases, the mass of dpm

emissions produced per hour increases. (A smaller engine may produce

the same or higher levels of particulate emissions per volume of

exhaust as a large engine, due to the airflow, but the mass of

particulate matter increases with the engine size). Accordingly, as

engine size increases, control of emissions may require additional

efforts.

Diesel engines in metal and nonmetal underground mines, and in

surface coal mines, range up to 750 HP or greater; by contrast, in

underground coal mines, the average engine size is less than 150 HP.

The reason for this disparity is the nature of the equipment powered by

diesel engines. In underground metal and nonmetal mines, and surface

mines,

[[Page 58125]]

diesel engines are widely used in all types of equipment -- both the

equipment used under the heavy stresses of production and the equipment

used for support. By contrast, the great majority of the diesel usage

in underground coal mines is in support equipment. For example, in

underground metal and nonmetal mines, of the approximate 4,100 pieces

of diesel equipment normally in use, about 1,800 units are for loading

and hauling. By contrast, of the approximate 3,000 pieces of diesel

equipment in underground coal, MSHA estimates that less than 50 pieces

are for coal haulage. The largest diesel engines are used in surface

operations; in underground metal and nonmetal mines, the size of the

engine can be limited by the size of the shaft opening.

The type of equipment in the sectors also varies in another way

that can affect particulate control directly, as well as constrain

engine size. In underground coal, equipment that is used in face

(production) areas of the coal mine must be MSHA-approved Part 36

permissible equipment. These locations are the areas where methane gas

is likely to accumulate in higher concentrations. This includes the in-

by section starting at the tailpiece (coal dump point) and all returns.

Part 36 permissible equipment for coal requires the use of flame

arresters on the intake and exhaust systems and surface temperature

control to below 302 deg.F. As discussed in more detail elsewhere in

this notice, the cooler exhaust from these permissible pieces of

equipment permits the direct installation of particulate filtration

devices such as paper type filters that cannot be used directly on

engines with hot exhaust. In addition, the permissibility requirements

have had the effect of limiting engine size. This is because prior to

MSHA's issuance of a diesel equipment rule in 1996, surface temperature

control was done by water jacketing. This limited the horsepower range

of the permissible engines because manufacturers have not expended

resources to develop systems that could meet the 302 deg.F surface

temperature limitation using a water jacketed turbocharger.

In the future, larger engines may be used on permissible equipment,

because the new diesel rule allows the use of new technologies in lieu

of water jacketing. This new technology, plus the introduction of air-

charged aftercoolers on diesel engines, may lead to the application of

larger size diesel engines for underground coal production units.

Moreover, if manufacturers choose to develop this type of technology

for underground coal production units, the number of diesel production

machines may increase.

There are also a few underground metal and nonmetal mines that are

gassy, and these require the use of Part 36 permissible equipment.

Permissible equipment in metal and nonmetal mines must be able to

control surface temperatures to 400 deg.F. MSHA estimates that there

are currently less than 15 metal and nonmetal mines classified as gassy

and which, therefore, must use Part 36 permissible equipment if diesels

are utilized in areas where permissible equipment is required. These

gassy metal and nonmetal mines have been using the same permissible

engines and power packages as those approved for underground coal

mines. (MSHA has not certified a diesel engine exclusively for a Part

36 permissible machine for the metal and nonmetal sector since 1985 and

has certified only one permissible power package; however, that engine

model has been retired and is no longer available as a new purchase to

the industry). As a result, these mines are in a similar situation as

underground coal mines: engine size (and thus dpm production of each

engine) is more limited, and the exhaust is cool enough to add the

paper type of filtration device directly to the equipment.

In nongassy underground metal and nonmetal mines, and in all

surface mines, mine operators can use conventional construction

equipment in their production sections without the need for

modifications to the machines. Two examples are haulage vehicles and

dump trucks. Some construction vehicles may be redesigned and

articulated for sharper turns in underground mines; however, the

engines are still the industrial type construction engines. As a

result, these mines can and do use engines with larger horsepower. At

the same time, since the exhaust is not cooled, paper-type filters

cannot be added directly to this equipment without first adding a water

scrubber, heat exchanger or other cooling device. The same is true for

the equipment used in outby areas of coal mines, where the methane

levels do not require the use of permissible equipment.

Future Demand and Emissions. MSHA expects there will be more

diesel-powered equipment added to the Nation's mines. While other types

of power sources for mining equipment are available, many in the mining

industry believe that diesel power provides both safety and economic

advantages over alternative power sources available today. Not many

studies have been done recently on these contentions, and the studies

which have been reviewed by MSHA do not clearly support this

hypothesis; but as long as this view remains prevalent, continued

growth is likely.

There are additional factors that could increase growth. As noted

above, permissible equipment can now be designed in such a way to

permit the use of larger engines, and in turn more use of diesel-

powered production equipment in underground coal and other gassy mines.

Moreover, state laws banning the use of diesel engines in the

underground coal sector are under attack. As noted in section 8 of this

part, until recently, three major underground coal states,

Pennsylvania, West Virginia, and Ohio, have prohibited the use of

diesel engines in underground coal mines. In late 1996, Pennsylvania

passed legislation (PA Senate Bill No. 1643) permitting such use under

conditions defined in the statute. West Virginia passed legislation

lifting its ban as of May, 1997 (WV House Bill 2890), subject to

regulations to be developed by a joint labor-industry commission. This

makes the need to address safety and health concerns about the use of

such engines very pressing.

In the long term, the mining industry's diesel fleet will become

cleaner, even if the size of the fleet expands. This is because the old

engines will eventually be replaced by new engines that will emit fewer

particulates than they do at present. As discussed in Section 4 of this

part, EPA regulations limiting the emissions of particulates and

various gasses from new diesel engines are already being implemented

for some of the smaller engines used in mining. Under a defined

schedule, these new standards will soon apply to other new engines,

including the larger engines used in mining. Moreover, over time, the

emission standards which new engines will have to pass will become more

and more stringent. Under international accords, imported engines are

also likely to be cleaner: European countries have already established

more stringent emission requirements (Needham, 1993; Sauerteig, 1995).

Based on the feasibility using the estimator, new engine

technology, catalytic converters, and current ventilation should reduce

dp levels down below the 400TCum3. However, to

reduce to the 160TCum3 level, dp filters or cabs

will still be needed on a certain number of equipment, based on mining

conditions and diesel usage. The particulate index values listed for

the MSHA approved engines provides information on the dp emissions and

also can be used to help determine how low engine technology alone can

lower

[[Page 58126]]

dp exposures. When filters are used, the cleaner engines allow the

filters to last longer between change out or cleaning. The newer

technology engines, especially the electronic models, also add the

benefit of diagnostic control. The engines computer can inform the

mechanic on the condition of the engine and warn the mechanic when an

engine is in need of maintenance.

But MSHA believes that turnover of the mining fleet to these new,

cleaner engines will take a very long time because the mining industry

tends to purchase for mining use older equipment that is being

discarded by other industries. In the meantime, the particulate burden

on miners as a group is expected to remain at current levels or even

grow.

(2) Diesel Exhaust and Diesel Particulate. The emissions from

diesel engines are actually a complex mixture of compounds, containing

gaseous and particulate fractions. The specific composition of the

diesel exhaust in a mine will vary with the type of engines being used

and how they are used. Factors such as type of fuel, load cycle, engine

maintenance, tuning, and exhaust treatment will affect the composition

of both the gaseous and particulate fractions of the exhaust. This

complexity is compounded by the multitude of environmental settings in

which diesel-powered equipment is operated. Elevation, for example, is

a factor. Nevertheless, there are a few basic facts about diesel

emissions that are of general applicability.

The gaseous constituents of diesel exhaust include oxides of

carbon, nitrogen and sulfur, alkanes and alkenes (e.g., butadiene),

aldehydes (e.g., formaldehyde), monocyclic aromatics (e.g., benzene,

toluene), and polycyclic aromatic hydrocarbons (e.g., phenanthrene,

fluoranthene). The oxides of nitrogen (NOx) are worth

particular mention because in the atmosphere they can precipitate into

particulate matter. Thus, controlling the emissions of NOx

is one way that engine manufacturers can control particulate production

indirectly. (See Section 4 of this part.)

The particulate fraction of diesel exhaust--what is known as soot--

is made up of very small individual particles. Each particle consists

of an insoluble, elemental carbon core and an adsorbed, surface coating

of relatively soluble organic carbon (hydrocarbon) compounds. There can

be up to 1,800 different organic compounds adsorbed onto the elemental

carbon core. A portion of this hydrocarbon material is the result of

incomplete combustion of fuel; however, the majority is derived from

the engine lube oil. In addition, the diesel particles contain a

fraction of non-organic adsorbed materials.

Diesel particles released to the atmosphere can be in the form of

individual particles or chain aggregates (Vuk, Jones, and Johnson,

1976). In underground coal mines, more than 90% of these particles and

chain aggregates are submicrometer in size--i.e., less than 1

micrometer (1 micron) in diameter. In underground metal and nonmetal

mines, a greater portion of the aggregates may be larger than 1 micron

in size because of the equipment used. Dust generated by mining and

crushing of material--e.g., silica dust, coal dust, rock dust--is

generally not submicrometer in size.

Figure II-1 shows a typical size distribution of the particles

found in the environment of a mine that uses equipment powered by

diesel engines (Cantrell and Rubow, 1992). The vertical axis represents

relative concentration, and the horizontal axis the particle diameter.

As can be seen, the distribution is bimodal, with dpm generally being

well less than 1 m in size and dust generated by the mining

process being well greater than 1 m. Because of their small

size, even when diesel particles are present in large quantities, the

environment might not be perceived as ``dusty''. Rather, the perception

might be primarily of a vaporous, dirty and smelly ``soot'' or

``smoke''.

[GRAPHIC] [TIFF OMITTED] TP29OC98.020

[[Page 58127]]

The particulate nature of diesel soot has special significance for

the mining community, which has a history of significant health and

safety problems associated with dusts in the mining atmosphere. As a

result of this long experience, the mining community is familiar with

the standard techniques to control particulate concentrations. It knows

how to use ventilation systems, for example, to reduce dust levels in

underground mines. It knows how to water down particulates capable of

being impacted by that approach, and to divert particulates away from

where miners are actively working. Moreover, the mining community has

long experience in the sampling and measurement of particulates--and in

all the problems associated therewith. Miners and mine operators are

very familiar with sampling devices that are worn by miners during

normal work activities or placed in specific locations to collect dust.

They understand the significance of sample integrity, the validity of

laboratory analysis, and the concept of statistical error in individual

samples. They know that weather and mine conditions can affect

particulate production, as can changes in mine operations in an area of

the mine. MSHA and the former Bureau of Mines have conducted

considerable research into these topics. While the mining community has

often argued over these points, and continues to do so, the

sophistication of the arguments reflects the thorough familiarity of

the mining community with particulate sampling and analysis techniques.

(3) Methods Available to Measure DPM. There are a number of methods

which can measure dpm concentrations with reasonable accuracy when it

is at high concentrations and when the purpose is exposure assessment.

Measurements for the purpose of compliance determinations must be more

accurate, especially if they are to measure compliance with a dpm

concentration as low as 200 g/m3 or lower. It is

with these considerations in mind that MSHA has carefully analyzed the

available methods for measuring dpm.

Comments. In its advanced notice of proposed rulemaking (ANPRM) in

1992, MSHA sought information on whether there are methodologies

available for assessing occupational exposures to diesel particulate.

Some commenters argued that at that time there was no validated

sampling method for diesel exhaust and there had been no valid

analytical method developed to determine the concentration of diesel

exhaust. According to the American Mining Congress, (AMC 1992),

sampling methods commonly in use were prototypic in nature, were

primarily being utilized by government agencies and were subject to

interference. Commenters also stated that sampling instrumentation was

not commercially available and that the analytical procedures could

only be conducted in a limited number of laboratories. Several industry

commenters submitted results of studies to support their position on

problems with measuring diesel particulate in underground mines. A

problem with sampler performance was noted in a study using prototype

dichotomous sampling devices. Another commenter indicated that the

prototype sampler developed by the former Bureau of Mines (discussed

later in this section) for collecting the submicrometer respirable dust

was difficult to assemble but easy to use, and that no problems were

encountered. Problems associated with gravimetric analysis were also

noted in assessing a short term exposure limit (STEL). Another

commenter (Morton, 1992) indicated the cost of the sampling was

prohibitive.

Another issue addressed by commenters to the 1992 ANPRM was ``Are

existing sampling and exposure monitoring methods sufficiently

sensitive, accurate and reliable?'' If not, what methods would be more

suitable? Some commenters indicated their views that sampling methods

had not been validated at that time for compliance sampling. They

asserted that, depending on the level of measurement, both the size

selective and elemental carbon techniques have some utility. The

measurement devices give a precise measurement; however, because of

interferants, corrections may need to be made to obtain an accurate

measurement. Commenters also expressed the view that all of the

sampling devices are sophisticated and require some expertise to

assemble and analyze the results, and that MSHA should rely on outside

agencies to evaluate and validate the sampling methods. An on-board

sampler being developed by Michigan Technological University was the

only other emission measurement technology discussed in the comments.

However, this device is still in the development stage. Another

commenter indicated that the standard should be based on the hazard and

that the standard would force the development of measurement

technology.

Submicrometer Sampling. The former Bureau of Mines (BOM) submitted

information on the development of a prototype dichotomous impactor

sampling device that separates and collects the submicrometer

respirable particulate from the respirable dust sampled (See Figure II-

2).

[[Page 58128]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.021

The sampling device was designed to help measure dpm in coal mine

environments, where, as noted in the last section of this part, nearly

all the dpm is submicrometer (less than 1 micron) in size. In its

submission to MSHA, the former BOM noted it had redesigned a prototype

and had verified the sampler's performance through laboratory and field

tests.

As used by the former BOM in its research, the submicrometer

respirable particulate was collected on a pre-weighed filter. Post-

weighing of the filter provides a measure of the submicrometer

respirable particulate. The relative insensitivity of the gravimetric

method only allows for a lower limit of detection of approximately 200

g/m\3\.

Because submicrometer respirable particulate can contain

particulate material other than diesel particulate, measurements can be

subject to interference from other submicrometer particulate material.

NIOSH Method 5040. In response to the ANPRM, NIOSH submitted

information relative to the development of a sampling and analytical

method to assess the diesel particulate concentration in an environment

by measuring the amount of total carbon.

As discussed earlier in this part, diesel particulate consists of a

core of elemental carbon (EC), adsorbed organic carbon (OC) compounds,

sulfates, vapor phase hydrocarbons and traces of other compounds. The

method developed by NIOSH provides for the collection of a sample on a

quartz fiber filter. The filter is mounted in an open face filter

holder that allows for the sample to be uniformly deposited on the

filter surface. After sampling, a section of the filter is analyzed

using a thermal-optical technique (Birch and Cary, 1996). This

technique allows the EC and OC species to be separately identified and

quantified. Adding the EC and OC species together provides a measure of

the total carbon concentration in the environment. This is indicated

diagrammatically in Figure II-3.

Studies have shown that the sum of the carbon (C) components

(EC+OC) associated with dpm accounts for 80-85% of the total dpm

concentration when low sulfur fuel is used (Birch and Cary, 1996).

Since the TC:DPM relationship is consistent, it provides a method for

determining the amount of dpm.

The method can detect as little as 1 g/m3 of TC.

Moreover, NIOSH has investigated the method and found it to meet

NIOSH's accuracy criterion (NIOSH, 1995); i.e., that measurements come

within 25 percent of the true TC concentration at least 95 percent of

the time.

[[Page 58129]]

[GRAPHIC] [TIFF OMITTED] TP29OC98.022

NIOSH Method 5040 is directly applicable for the determination of

diesel particulate levels in underground metal and nonmetal mines. The

only potential sources of carbon in such mines would be organic carbon

from oil mist and cigarette smoke. Oil mist may occur when diesel

equipment malfunctions or is in need of maintenance.

MSHA, currently, has no data as to the frequency of occurrence or

the magnitude of the potential interference from oil mist. However,

during studies conducted by MSHA to evaluate different methods used to

measure diesel particulate concentrations in underground mines, MSHA

has not encountered situations where oil mist was found to be an

interferant. Moreover, the Agency assumes that full operator

implementation of maintenance standards to minimize dpm emissions

(which are part of MSHA's proposed rule) will minimize any remaining

potential for such interference. MSHA welcomes comments or data

relative to oil mist interference. Cigarette smoke is under the control

of operators, during sampling times in particular, and hence should not

be a consideration.

While samples in underground metal and nonmetal mines could be

taken with a submicrometer impactor, this could lead to underestimating

the total amount of dpm present. This is because the fraction of dpm

particles greater than 1 micron in size in the environment of noncoal

mines can be as great as 20% (Vuk, Jones, and Johnson, 1976).

When sampling diesel particulate in coal mines, the NIOSH method

recommends that a specialized impactor with a submicrometer cut point,

such as the one developed by the former BOM, be used. Use of the

submicron impactor minimizes the collection of coal particles, which

have an organic carbon content. However, if 10% of coal particles are

submicron, this means that up to 200 micrograms of submicrometer coal

dust could be collected in face areas under current coal dust

standards. Accordingly, for samples collected in underground coal

mines, an adjustment may have to be made for interference from

submicrometer coal dust; however, outby areas where little coal mine

dust is present may not need such an adjustment.

NIOSH further recommends that in using its method in coal mines,

the sample only be analyzed for the EC component. Measuring only the EC

component ensures that only diesel particulate material is being

measured in such cases. However, there are no established relationships

between the concentration of EC and total dpm under various operating

conditions. (The organic carbon component of dpm can vary with engine

type and duty cycle; hence, the amount of whole dpm present for a

measured amount of EC may vary). The Agency welcomes data and

suggestions that would help it ascertain if and how measurements of

submicrometer elemental carbon could realistically be used to measure

dpm concentrations in underground coal mines.

Although NIOSH Method 5040 requires no specialized equipment for

collecting a dpm sample, the sample would most probably require

analysis by a commercial laboratory. MSHA recognizes that the number of

laboratories currently capable of analyzing samples using the thermal-

optical method is limited. However, there are numerous laboratories

available that have the ability to perform a TC analysis without

identifying the different species of carbon in the sample. Total carbon

determinations using these laboratories would provide the mine with

good information relative to the levels of dpm to which miners are

potentially exposed. MSHA believes that once there is a need (e.g., as

a result of the requirements of the proposed rule), more commercial

laboratories will develop the capability to analyze dpm samples using

the thermo-optical analytical method. Currently, the cost to analyze a

submicrometer particulate sample for its TC content ranges from $30 to

$50. This cost is consistent with costs associated with similar

analysis of minerals such as quartz.

RCD Method. Another method, referred to as the Respirable

Combustible Dust Method (RCD), has been developed in Canada for

measuring dpm concentrations in noncoal mines. Respirable dust is

collected with a respirable dust sampler consisting of a 10 millimeter

nylon cyclone and a filter capsule containing a preweighed,

preconditioned silver membrane filter. Samples are collected at a flow

rate of 1.7 liters per minute. The respirable sample collected includes

both combustible and noncombustible particulate matter.

[[Page 58130]]

Samples collected in accordance with the RCD method require

analysis by a commercial laboratory. Total respirable dust is

determined gravimetrically by weighing the filter after the sample is

collected. After the sample has been subjected to a controlled

combustion process at 400 deg.C for two hours, the remainder of the

sample is weighed, and the amount of the particulate burned off

determined by subtraction. This is the RCD. The combustible particulate

matter consists of the soluble organic fraction, the EC core of the

dpm, and any other combustible material collected. Thus, only a portion

of the RCD is attributable to dpm. Oil mist and other combustible

matter collected on the filter are interferants that can affect the

accuracy of dpm concentration determination using this method. Because

the mass of RCD is determined by weighing, the relative insensitivity

of this method is similar to that obtained with the size selective

gravimetric method (approximately 200 g/m\3\).

One commenter (Inco Limited) indicated experience with this method

for identifying diesel particulate in their mining operations and

suggested that this technique may be appropriate for determining eight

hour exposures. Although this method was commonly used by the commenter

for assessing dpm levels, concerns for the efficiency of the cyclones

used to sample the respirable fraction of the particulate along with

interference from oil mist were expressed.

Canada is now experimenting with the use of a submicron impactor

with the RCD method.

Sampler Availability. The components for conducting sampling

according to the submicrometer and the RCD methods are commercially

available, as are those for NIOSH Method 5040, without a submicrometer

particulate separator (impactor).

A reusable impactor can be manufactured by machine shops following

the design specifications developed by the former U.S. Bureau of Mines

(BOM IC 9324, 1992). The use of the size-selective samplers requires

some training and laboratory time to prepare the impaction plate and

assemble the unit. The cost to manufacture the size-selective units is

approximately $35.

In addition, MSHA has requested NIOSH to develop and provide a

commercially available disposable submicrometer particulate separator

that would be used with existing personal respirable dust sampling

equipment. The commercially available separator will be manufactured

according to design criteria specified by NIOSH. It is anticipated that

other sampling instrument manufacturers will develop commercial units

once there is an established need for such a sampling device.

Use of Alternative Surrogates to Assess DPM Concentrations. A

number of commenters on the ANPRM indicated that a number of surrogates

were available to monitor diesel particulate. Of the surrogates

suggested, the most desirable to use would be carbon dioxide because of

its ease of measurement. In 1992 the former Bureau of Mines (BOM IC

9324, 1992) reported on research being conducted to investigate the use

of CO2 as a surrogate to assess mine air quality where

diesel equipment is utilized. However, because the relationship between

CO2 and other exhaust components depends on the number, type

and duty cycle of the engines in operation, no acceptable measurement

method based on the use of CO2 has been developed.

(4) Reducing Soot at the Source--Engine Standards. One way to limit

diesel particulate emissions is to redesign diesel engines so they

produce fewer pollutants. Engine manufacturers around the world are

being pressed to do this pursuant to environmental regulations. These

cleaner engine requirements are sometimes referred to as tailpipe

standards because compliance is measured by checking for pollutants as

the exhaust emerges from the engine's tailpipe--before any

aftertreatment devices. This section reviews developments in this area,

and explains the relationship between the environmental standards on

new engines and MSHA engine ``approval'' requirements.

The Clean Air Act and Mobile Sources. The Clean Air Act authorized

the Federal Environmental Protection Agency (EPA) to establish

nationwide standards for new mobile vehicles, including those powered

by diesel engines. These standards are designed, over time, to reduce

the volume of certain harmful atmospheric pollutants emanating from

mobile sources: particulate matter, nitrogen oxides (which as

previously noted, can result in the generation of particulates in the

atmosphere), hydrocarbons and carbon monoxide.

California has its own standards. New engines destined for use in

California must meet standards under the law of that State. The

standards are issued and administered by the California Air Resources

Board (CARB). In recent years, EPA and CARB have worked together with

industry in establishing their respective standards, so most of them

are identical.

Regulatory responsibility for implementation of the Clean Air Act

is vested in the Office of Mobile Sources (OMS), part of the Office of

Air and Radiation of the EPA. Some of the discussion which follows was

derived from materials which can be accessed from the OMS home page on

the World Wide Web at (http://www.epa.gov/docs/omswww/omshome.htm).

Information about the CARB standards may be found at the home page of

that agency at (http://www.arbis.arb.ca.gov/homepage.htm).

Engines are generally divided into three broad categories for

purposes of environmental emissions standards, in accordance with the

primary use for which the type of engine is designed: (1) cars and

light duty trucks (i.e., to power passenger transport); (2) heavy duty

trucks (i.e., to power over-the-road hauling); and (3) nonroad vehicles

(i.e., to power small equipment, construction equipment, locomotives

and other non-highway uses). Engines used in mining equipment are not

regulated as a separate category in this regard, but engines in all

three categories are engaged in mining work, from generator sets to

pickup trucks to huge earth movers and haulers.

New vs. Used. The environmental tailpipe requirements are

applicable only to new engines. In the mining industry, used engines

are often purchased; and, of course, the existing fleet consists of

engines that are not new. Thus, although these tailpipe requirements

will bring about gradual reduction in the overall contribution of

diesel pollution to the atmosphere, the beneficial effects on mining

atmospheres may require a longer timeframe, absent actions to

accelerate the turnover of mining fleets to the cleaner engines.

In underground coal mining, MSHA has already taken actions which

will have such an effect on the fleet. The diesel equipment rule issued

in late 1996 requires that by November 25, 1999, all diesel equipment

used in underground coal mines use an approved engine and maintain that

engine in approved condition (30 CFR 75.1907). MSHA expects this will

result in the replacement of about 47 percent of the diesel engines now

in the underground coal mine inventory with engines that emit fewer

pollutants. The timeframe permitted for the turnover was based upon

MSHA's estimates of the useful life in an underground mining

environment of the ``outby'' equipment involved.

Technology-Forcing Schedule. As noted above, the exact

environmental tailpipe requirements which a new

[[Page 58131]]

diesel engine must meet varies with the date of manufacture. The Clean

Air Act, which was most recently amended in 1990, establishes a

schedule for the reduction of particular pollutants from mobile

sources. EPA and CARB, working closely with the diesel engine industry,

have endeavored to turn this into a regulatory schedule that forces

technology while taking into account certain technological realities

(e.g., actions taken to reduce particulate emissions may increase

NOX emissions, and vice versa). Existing EPA regulations for

on-highway engines (both for light duty vehicles and heavy duty trucks)

and non-road engines schedule the tailpipe standards that must be met

for the rest of this century. Agreements between EPA, CARB and the

engine industry are now leading to proposed rules for engine standards

to be met during the early part of the next century. These standards

will be stricter and will lower the levels of diesel emissions.

Light-Duty Engines. The current regulations on light duty vehicle

engines (cars and passenger trucks) were set in 1991 (56 FR 25724). EPA

is currently considering proposing new standards for this category.

Pursuant to a specific requirement in the Clean Air Act Amendments of

1990, EPA is to study and report to Congress on whether further

reductions in this category should be pursued. A public workshop was

held in the Spring of 1997. EPA plans provide for a draft report to be

available for public comment by Spring of 1998, and a final report

completed by July 1998, although a notice of citizen suit has been

filed to speed the process. Up-to-date information about the progress

of this initiative can be found at the home page for the study (http://

www.epa.gov/omswww/tr2home.htm).

On-highway Heavy Duty Truck Engines. The first phase of the on-

highway standards for heavy duty diesel engines was applicable to

engines manufactured in 1985 (40 CFR 86.085-11). For the first time,

separate standards for nitrogen oxide (NOX) and hydrocarbons

(HC) were established. The nitrogen oxides and hydrocarbons are

precursors of ground level ozone, a major component of smog. A number

of hydrocarbons are also toxic, while nitrogen oxides contribute to the

formation of acid rain and can, as previously noted, precipitate into

particulate matter. In 1988, a specific standard limiting particulate

matter emitted from the heavy duty on-highway diesel engines went into

effect (40 CFR 86.088-11). The Clean Air Act Amendments and the

regulations provided for phasing in even tighter controls on

NOX and particulate matter through 1998. Reductions in

NOX took place in 1990 and 1991 and are to occur again in

1998, and reductions in PM took place in 1991 and 1994. Certain types

of trucks in particularly polluted urban areas must reach even tighter

requirements.

On October 21, 1997, EPA issued a new rule for on-highway engines

that will take effect for engine model years starting in 2004 (62 FR

54693). The rule establishes a combined requirement for NOX

and HC. The combined standard is set at 2.5gm/bhp-hr, which includes a

cap of 0.5gm/bhp-hr for HC. Prior to the rule, the EPA, CARB, and the

engine manufacturers signed a Statement of Principles (SOP) that agreed

on harmonization of the emission standards and the feasible levels that

could be achieved. The rule allows manufacturers a choice of two

combinations of NOX and HC, with a net expected reduction in

NOX emissions of 50%. The rule does not require further

reductions in tailpipe emissions of PM.

Non-road Engines. Of particular interest to the mining community is

the EPA's regulatory work on the standards that will be applicable to

non-road engines, for these include the engines used in the heaviest

mining equipment.

The 1990 Clean Air Act Amendments specifically directed EPA to

study the contribution of nonroad engines to air pollution, and

regulate them if warranted. In 1991, EPA released a study that

documented higher than expected emission levels across a broad spectrum

of nonroad engines and equipment (EPA Fact Sheet, EPA420-F-96-009,

1996). In response, EPA initiated several regulatory programs. One of

these set emission standards for land-based nonroad engines greater

than 50 horsepower (other than for rail use). Limits are established

for tailpipe emissions of hydrocarbons, carbon monoxide,

NOX, and dpm. The limits are phased in from 1996 to 2000:

starting in 1996 with nonroad engines from 175 to 750 hp, then smaller

engines, and by 2000 the larger nonroad engines. Moreover, in February

1997, restrictions on nonroad engines for locomotives were proposed (62

FR 6366).

In September 1996, EPA announced another Statement of Principles

(SOP) with the engine industry and CARB on new rounds of restrictions

for non-road engines to begin to take place in this century. This led

in September 1997 to a proposed rule setting standards for almost all

types of engines in this category manufactured after 1999-2006 (the

actual year depends on the category) (62 FR 50151). The applicable

standards for an engine category would be gradually tightened through

three tiers. They would set a cap on the combined NOX and HC

(similar to the on-highway), set CO standards, and lower standards on

PM. The implementation of the final tier of the proposed reductions is

subject to a technology review in 2001 to ensure that the

appropriateness of the levels to be set is feasible.

Will the Diesel Engine Industry Meet Mining Industry Requirements?

Concern has been expressed from time to time that the diesel industry

might not be able to meet the ever tightening standards on tailpipe

emissions, and might, therefore, stop producing certain engines needed

by the mining community or other industries (Gushee, 1995). To date,

however, such concerns have not been realized. The fact that the most

recent regulations have been developed through a consensus process with

the engine industry, and that the non-road plan includes a scheduled

technology review to ensure the proposed emission standards can really

be achieved, suggests that although the EPA standards are technology

forcing, diesel engines will continue to be available to meet the needs

of the mining community for the foreseeable future. In addition, the

nonroad engine agreement with the industry calls for development of a

separate research agreement involving stakeholders in the exploration

of technologies that can achieve very low emission levels of

NOX and PM ``while preserving performance, reliability,

durability, safety, efficiency, and compatibility with nonroad

equipment'' (EPA420-F-96-015, September 1996). Also, Vice President

Gore has recently noted that the Administration is committed to

emissions research that would clean up both the diesels currently on

the road, as well as enabling these engines an opportunity to compete

as a new generation of vehicles is developed that are far more

efficient than today's vehicles (White House Press Release, July 23,

1997). It is always possible, of course, that some new technological

problems could emerge that could impact diesel engine availability--

e.g., confirmation that some of the newer engines produce high levels

of ``nanoparticles'' particulates and that such emissions pose some

sort of a health problem. Research of nanoparticles and their health

effects is currently a topic of investigation (Bagley et al., 1996).

A related question has been whether the costs of the ``high-tech''

diesel engines will make them unaffordable in practice to the mining

community.

[[Page 58132]]

MSHA believes the new engines will be affordable. The fact that the

engine industry has agreed to the new standards, and has some assurance

of what the applicable standards will be for the foreseeable future,

should help keep costs in check.

In theory, underground mines can control costs by purchasing

certain types of new engines that do not have to meet the new EPA

standards. The rules on heavy duty on-highway truck engines were not

applied to engines intended to be used in underground coal mines (59 FR

31336), and the new proposed rules on nonroad vehicles would likewise

not be mandatory for engines intended for any underground mining use.

In practice, however, it is not likely that engine manufacturers will

produce special engines once they switch over their production lines to

meet the new EPA standards, because there are few types and sizes of

engines in production for which the mining community is the major

market. Moreover, the larger engines (above 750 hp) are specifically

covered by the EPA nonroad rules (Engine Manufacturers Assn. v. EPA, 88

F.3d 1075, 319 U.S. App.D.C. 12 (1996).

MSHA Approved Engines. Acting under its own authority to protect

miner safety and health, MSHA requires that diesel engines used in

certain types of mining operations be ``approved'' as meeting certain

tailpipe standards.

In some ways, the standards are akin to those of EPA and CARB. For

example, MSHA, CARB and EPA generally use the same tests to check

emissions. MSHA uses a steady state, 8-mode test cycle, the same as EPA

and CARB use to test engines designed for use in off-road equipment;

however, EPA uses a different, transient test for on-highway engines.

But to be approved by MSHA, an engine does not have to be as clean

as the newer diesel engines, every generation of which must meet ever

tighter EPA and CARB tailpipe standards. Approval of an engine by MSHA

merely ensures that the tailpipe emissions from that engine meet

certain basic standards of cleanliness--cleaner than the engines which

many mines continue to use.

The MSHA approval rules were revised in 1996 (as part of the 1996

rule on the use of diesel equipment in underground coal mines) to

provide the mining community with additional information about the

cleanliness of the emissions emerging from the tailpipe of various

engines. Specifically, the agency now requires that a particulate index

(PI) be reported as part of MSHA's engine approval. This index permits

operators to evaluate the contribution of a proposed new addition to

the fleet to the mine's particulate concentrations.

There is no requirement that approved engines meet a particular PI;

rather, the requirement is for information purposes only. In its 1996

rulemaking addressing diesel equipment in underground coal mines, MSHA

explicitly deferred until this rulemaking the question of whether to

require engines used in mining environments to meet a particular PI (61

FR 55420-21, 55437). The Agency has decided not to take that approach,

for the reasons discussed in Part V of this preamble.

(5) Limiting the Public's Exposure to Soot--Ambient Air Quality

Standards. Pursuant to the Clean Air Act, EPA is responsible for

setting air pollution standards to protect the public from toxic air

contaminants. These include standards to limit exposure to particulate

matter. The pressures to comply with these limits have an impact upon

the mining industry, which contributes various types of particulate

matter into the environment during mining operations, and a special

impact on the coal mining industry whose product is used extensively in

emission-generating power facilities. But those standards hold interest

for the mining community in other ways as well, for underlying some of

them is a large body of evidence on the harmful effects of airborne

particulate matter on human health. Increasingly, that evidence has

pointed toward the risks of the smallest particulates--including the

particles generated by diesel engines.

This section provides an overview of EPA rulemaking on particulate

matter. For more detailed information, commenters are referred to ``The

Plain English Guide to the Clean Air Act,'' EPA 400-K-93-001, 1993, to

the ``Review of the National Ambient Air Quality Standards for

Particulate Matter: Policy Assessment of Scientific and Technical

Information'', EPA-452/R-96-013, 1996; and, on the latest rule, to EPA

Fact Sheets, July 17, 1997. These and other documents are available

from EPA's Web site.

Background. Air quality standards involve a two-step process:

standard setting by EPA, and implementation by each State.

Under the law, EPA is specifically responsible for reviewing the

scientific literature concerning air pollutants, and establishing and

revising National Ambient Air Quality Standards (NAAQS) to minimize the

risks to health and the environment associated with such pollutants. It

is supposed to do a review every five years. Feasibility of compliance

by pollution sources is not supposed to be a factor in establishing

NAAQS. Rather, EPA is required to set the level that provides ``an

adequate margin of safety'' in protecting the health of the public.

Implementation of each national standard is the responsibility of

the states. Each must develop a state implementation plan that ensures

air quality in the state consistent with the ambient air quality

standard. Thus, each state has a great deal of flexibility in targeting

particular modes of emission (e.g., mobile or stationary, specific

industry or all, public sources of emissions vs. private-sector

sources), and in what requirements to impose on polluters. However, EPA

must approve the state plans pursuant to criteria it establishes, and

then take pollution measurements to determine whether all counties

within the state are meeting each ambient air quality standard. An area

not meeting an NAAQS is known as a ``nonattainment area''.

TSP. Particulate matter originates from all types of stationary,

mobile and natural sources, and can also be created from the

transformation of a variety of gaseous emissions from such sources. In

the context of a global atmosphere, all these particles are mixed

together, and both people and the environment are exposed to a

``particulate soup'' the chemical and physical properties of which vary

greatly with time, region, meteorology, and source category. The first

ambient air quality standards dealing with particulate matter did not

distinguish among these particles. Rather, the EPA established a single

NAAQS for ``total suspended particulates'', known as ``TSP.'' Under

this approach, the states could come into compliance with the ambient

air requirement by controlling any type or size of TSP. As long as the

total TSP was under the NAAQS--which was established based on the

science available in the 1970s--the state met the requirement.

PM10. When the EPA completed a new review of the

scientific evidence in the mid-eighties, its conclusions led it to

revise the particulate NAAQS to focus more narrowly on those

particulates less than 10 microns in diameter, or PM10. The

standard issued in 1987 contained two components: an annual average

limit of 150 g/m3, and a 24-hour limit of 50

g/m3. This new standard required the states to

reevaluate their situations and, if they had areas that exceeded the

new PM10 limit, to refocus their compliance plans on

reducing those particulates smaller than 10 microns in size. Sources of

PM10 include power plants, iron and steel production,

chemical and wood products

[[Page 58133]]

manufacturing, wind-blown and roadway fugitive dust, secondary aerosols

and many natural sources.

Some state implementation plans required surface mines to take

actions to help the state meet the PM10 standard. In

particular, some surface mines in Western states were required to

control the coarser particles--e.g., by spraying water on roadways to

limit dust. The mining industry has objected to such controls, arguing

that the coarser particles do not adversely impact health, and has

sought to have them excluded from the EPA ambient air standards (Shea,

1995; comments of Newmont Gold Company, March 11, 1997, EPA docket

number A-95-54, IV-D-2346).

PM2.5. The next scientific review was completed in 1996,

following suit by the American Lung Association and others. A proposed

rule was published in November of 1996, and, after public hearings and

review by the Office of the President, a final rule was promulgated on

July 18, 1997 (62 FR 38651).

The new rule further modifies the standard for particulate matter.

Under the new rule, the existing national ambient air quality standard

for PM10 remains basically the same--an annual average limit

of 150 g/m3 (with some adjustment as to how this is

measured for compliance purposes), and a 24-hour ceiling of 50

g/m3. In addition, however, a new NAAQS has now

been established for ``fine particulate matter'' that is less than 2.5

microns in size. The PM2.5 annual limit is set at 15

g/m3, with a 24-hour ceiling of 65 g/

m3.

The basis for the PM2.5 NAAQS is a new body of

scientific data suggesting that particles in this size range are the

ones responsible for the most serious health effects associated with

particulate matter. The evidence was thoroughly reviewed by a number of

scientific panels through an extended process. (A chart of the

scientific review process is available on EPA's web site--http://

ttnwww.rtpnc.epa.gov/naaqspro/pmnaaqs.gif). The proposed rule resulted

in considerable press attention, and hearings by Congress, in which

this scientific evidence was further discussed. Following a careful

review, President Clinton announced his concurrence with the rulemaking

in light of the scientific evidence of risk. However, the

implementation schedule for the rule is long enough so that the next

review of the science is scheduled to be completed before the states

are required to meet the new NAAQS for PM2.5--hence,

adjustment of the standard is still possible before implementation.

Implications for the Mining Community. As noted earlier in this

part, diesel particulate matter is mostly less than 1.0 micron in size.

It is, therefore, a fine particulate. The body of evidence of human

health risk from environmental exposure to fine particulates must,

therefore, be considered in assessing the risk of harm to miners of

occupational exposure to one type of fine particulate--diesel

particulate. MSHA has accordingly done so in its risk assessment (see

Part III of this preamble).

(6) Controlling Diesel Particulate Emissions in Mining--a Toolbox.

Efforts to control diesel particulate emissions have been under review

for some time within the mining community, and accordingly, there is

considerable practical information available about controls--both in

general terms, and with respect to specific mining situations.

Workshops. In 1995, MSHA sponsored three workshops ``to bring

together in a forum format the U.S. organizations who have a stake in

limiting the exposure of miners to diesel particulate (including) mine

operators, labor unions, trade organizations, engine manufacturers,

fuel producers, exhaust aftertreatment manufacturers, and academia.''

(McAteer, 1995). The sessions provided an overview of the literature

and of diesel particulate exposures in the mining industry, state-of-

the-art technologies av

This text is long and has been trimmed here. Open the source document for the complete record.