The mining industry faces a conundrum over the Mine Safety and Health Administration’s Request for Information (RFI) for industry data and experiences accumulated by underground mine operators over the past 15 years. MSHA’s diesel particulate matter (DPM) rules require operators to maintain the information.

MSHA has regulated DPM in underground coal and metal/non-metal (M/NM) mines since 2001. In issuing its June 8 RFI in the Federal Register, the agency is interested in learning of enhanced controls that might improve protections for miners from DPM and diesel exhaust.

Currently, MSHA administers two separate DPM regulations. In underground M/NM mines, the agency has set an exposure limit of 160 micrograms per cubic meter of total carbon (TC) averaged over eight hours. TC serves as a surrogate for DPM. Unlike in M/NM, the underground coal regulation does not include a worker exposure limit because MSHA concluded there were too many confounding factors for TC to be an effective surrogate. Instead, the coal rule includes emissions limits for different types of equipment. Permissible and non-permissible heavy-duty equipment must not emit more than 2.5 grams per hour of DPM. For non-permissible light-duty vehicles, the maximum emission is five grams per hour. The M/NM exposure limits and coal emissions limits can be found at 30 CFR 57.5060 and 30 CFR 72.500, respectively. The agency has not ruled out extending its DPM rules to surface operations.

MSHA is basing its information-collection initiative on a government study that found a strong correlation between diesel exhaust and lung cancer in miners working around diesel equipment underground. In 2012, the International Agency for Research on Cancer concluded that diesel exhaust causes cancer in humans. MSHA said it was reopening the record due to the lung cancer risk and “to prevent material impairment of miners’ health.”

The agency will hold four public meetings on the RFI. They are being held in conjunction with meetings on the agency’s proposed M/NM workplace examination rule. (See our article, Mine Agency Focuses Attention on Workplace Exams, Diesel Exhaust Exposure.) The DPM meetings will begin immediately following the conclusion of testimony on the examination proposal. The diesel RFI comment period closes on September 6, 2016.