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MSHA Proposes Rule to Phase in Lower PEL for Diesel Particulate Matter

The Mine Safety and Health Administration (MSHA) has issued a proposed rule to phase in, over a 5-year period, a lower permissible exposure limit to diesel particulate matter (DPM) in underground metal and nonmetal mines.

A final rule MSHA issued in June converted the unit of measure for the interim permissible exposure limit (PEL) to DPM from 400 micrograms (µg) of total carbon to what the agency says is a more accurate measure of 308 µg of elemental carbon.

The proposed rule published Sept. 7 in the Federal Register would phase in the lower final PEL of 160 µg of total carbon over a 5-year period. A separate rulemaking would convert the final PEL to an equivalent measure of elemental carbon. Extensions could be granted to mines if compliance is not technologically or economically feasible.

The proposed rule also seeks comment on a number of questions, including whether miners should be transferred to an existing job if it is determined that they are medically unable to wear a respirator.

Written comments on this proposed rulemaking should be submitted by Oct. 14 to the MSHA Office of Standards, Regulations and Variances, 1100 Wilson Blvd., Room 2350, Arlington, Va. 22209-3939; fax 202-693-9441.

Comments may be submitted at, or by e-mail to [email protected], inserting RIN: 1219-AB29 in the subject line. Public hearings are scheduled for Sept. 26, 28 and 30.

MSHA's Web site at has a hearing schedule and a link to the proposed rule.

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