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Proposed Rule to Protect Underground Coal Miners
from Diesel Particulate Matter

U.S. Department of Labor
Mine Safety and Health Administration
April 1998

What is diesel particulate matter?

Diesel particulate matter (DPM) is composed of very small particles -- usually less than a micron (one millionth of a meter) in size -- which are emitted from diesel engines.

Are many underground coal miners exposed to diesel particulate matter?

MSHA estimates that about 13,000 underground coal miners are exposed to diesel emissions. Moreover, because of the working conditions in underground mines, DPM concentrations can be very high. In fact, some underground miners are exposed to concentrations of DPM that are more than 10 times as high as the average workplace exposures recorded in any other industry, and more than 200 times as high as the concentrations of DPM in the air of the most polluted urban areas in this country.

How do such exposures affect a miner's health?

When exposures to DPM are as high as those now being measured in some underground mines, the health consequences can be significant. Based upon a review of the scientific literature, MSHA has concluded that miners who are exposed to such high levels of DPM face a significantly higher risk of dying from such diseases as lung cancer, heart failure and other cardiopulmonary problems than do miners who are not so exposed. MSHA has also concluded that miners exposed to such levels of DPM face a significantly greater risk of incurring a variety of other health problems (e.g., coughs, headaches) which could result in lost work time and could impact job safety. Independent scientific experts reviewed MSHA's assessment of the risks to ensure its assessment is balanced and thorough.

Why is a regulation necessary, and what will it accomplish?

MSHA is required to act under the law when it determines that miners face a significant risk of material impairment of their health over a working lifetime. MSHA has determined that the high levels of DPM found in underground mines place the miners in those mines at just such a risk.

The proposed regulations will significantly reduce the exposure of underground miners to DPM.

Since miners in all underground dieselized mines are at risk, why is this action limited to underground coal mines?

The problem is just as serious for underground metal and nonmetal miners as underground coal miners. The type of equipment and conditions in underground metal and nonmetal mines differ, however, from those found in coal mines, and MSHA believes they require different approaches. MSHA will soon be proposing a separate regulation to protect underground metal and nonmetal miners.

What is MSHA proposing for surface coal mines?

DPM exposure levels are much lower at surface coal mines than at underground mines. Nonetheless, groups of miners working immediately around diesel-powered equipment where the exhaust is not adequately vented can be exposed to significant levels of DPM. MSHA will soon begin educational and outreach efforts to help control DPM exposures at surface operations.

What is MSHA proposing for underground coal mines?

The MSHA proposal for underground coal mines would require two things:

  1. the installation and proper maintenance of high-efficiency particulate filters on the most polluting types of diesel engines found in underground coal mines; and,

  2. the training of miners.

Why isn't MSHA proposing a permissible exposure limit (PEL) for DPM?

MSHA considered proposing a PEL; however, coal mine dust itself can complicate the task of accurately measuring the amount of DPM in underground coal mines. Therefore, the use of high-efficiency, easy-to-maintain particulate filtration systems is being proposed at this time. Use of these systems will significantly reduce miners' exposures to DPM without requiring mine operators to monitor regularly the mine atmosphere.

What are the provisions concerning filters on equipment?

  1. Within 18 months after the final rule is published, permissible diesel-powered equipment must be equipped with a system that removes 95 percent of the particulate material emitted from the engine.

  2. Within 30 months after the final rule is published, non-permissible heavy duty diesel-powered equipment must have a system that removes 95 percent of the particulate material emitted from the engine.

  3. MSHA proposes that the efficiency of a diesel particulate removal system be determined by performance in a laboratory test, using a specified MSHA approved test cycle.

  4. MSHA proposes that diesel particulate removal systems must be maintained in accordance with the equipment manufacturers' specifications.

  5. MSHA is asking for public comments on other approaches that could offer equivalent protection to underground coal miners.

How does MSHA define heavy duty equipment in the proposed regulation?

    (a) Equipment that cuts or moves rock or coal;
    (b) Equipment that performs drilling or bolting functions;
    (c) Equipment that moves longwall components;
    (d) Self-propelled diesel fuel transportation units and self-propelled lube units; or
    (e) Machines used to transport portable diesel fuel transportation units or portable lube units.

How does the proposed rule address light-duty equipment, such as pickup trucks?

In the proposal, MSHA is seeking comments from the public on whether there are categories of light-duty equipment that contribute significantly to miner exposures to DPM that could feasibly be controlled as part of this rulemaking.

What are the provisions concerning training of miners?

MSHA proposes that all miners who are expected to be exposed to diesel exhaust emissions be trained annually in:

  1. health risks associated with exposure to diesel particulate matter;
  2. methods used to control diesel particulate matter concentrations;
  3. identification of personnel responsible for maintaining those controls; and
  4. actions miners must take to ensure the controls operate as intended.

Instructor qualifications and training time are not specified; the goal is to heighten miner awareness.

What are the estimated costs of the proposed rule?

The cost of the proposed rule for the underground coal mine industry is estimated to be about $10 million a year. For a mine with less than 20 miners, MSHA estimates the costs to be about $8,000 a year. For large mines, MSHA estimates the costs to be about $58,000 a year.

What actions will MSHA take to help the industry implement the proposed rules?

The Agency will provide both general and mine-specific advice. The delayed effective dates in the proposed rule are designed to ensure that all mines have the information they need to implement the rule well in advance of implementation. MSHA has already issued a "Toolbox" that summarizes a wealth of information about controlling diesel emissions gathered from those in the industry who have experimented with various controls. Also, the Agency has developed a computer simulation program which can help individual mines ascertain the impact on DPM levels of implementing various controls. When the Agency issues a final rule, it will also issue a compliance guide.

How can the public provide comments on this matter?

Comments on the proposed rule will be accepted during the next 120 days and may be transmittedby electronic mail, fax, or mail, or dropped off in person at any MSHA office. The electronic mail address is The fax number is (703) 235-5551. The mailing address is MSHA, Office of Standards, Regulations, and Variances, Room 631, 4015 Wilson Boulevard, Arlington, VA. 22203-1984.

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