14 April 1998

On 9 April 1998, the US Mine Safety and Health Administration (MSHA) proposed a rule that would establish new health standards for underground coal mines that use equipment powered by diesel engines. The proposal is designed to reduce the risks to underground coal miners of serious health hazards that are associated with exposure to high concentrations of diesel particulate matter (DPM). Underground miners are exposed to far higher concentrations of DPM than any other group of workers. According to MSHA, evidence indicates that such high exposures put these miners at excess risk of a variety of adverse health effects, including lung cancer.

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.

Under the proposal, light-duty diesel-powered equipment would not be required to use diesel filters. However, MSHA asked for comment as to whether there are some types of light-duty equipment whose DPM emissions should, and could feasibly, be controlled.

MSHA considered an alternative approach of simply proposing a concentration limit for DPM in underground coal mines, instead of requiring that all engines be equipped with a high-efficiency filter. Such an approach would provide underground coal mine operators with flexibility to elect any combination of engineering controls they wish as long as the concentration of DPM in the mine remained below a set level. However, MSHA was not confident that there is a measurement method for DPM that would provide accurate, consistent and verifiable results at lower concentration levels in underground coal mines. The problem arised because coal dust contains organic compounds that might be mistaken for DPM in the methods otherwise validated for use at lower DPM concentrations. MSHA indicated it will be continuing to explore questions about the measurement of DPM in underground coal mines in consultation with NIOSH.

In the near future, MSHA intends to propose a separate rule to reduce DPM exposures in underground metal and nonmetal mines.

Comments on the proposed rule must be received on or before 7 August 1998.

Contact: Patricia W. Silvey, Director; Office of Standards, Regulations, and Variances, MSHA, 703-235-1910.

MSHA Information Paper
MSHA News Release
Proposed rule - 733k PDF