Diesel Particulate Matter Exposure of Underground Metal and Nonmetal Miners

This final rule revises MSHA's existing standards addressing diesel particulate matter (DPM) exposure in underground metal and nonmetal (M/NM) mines. In this final rule, MSHA changes the interim concentration limit measured by total carbon (TC) to a comparable permissible exposure limit (PEL) measured by elemental carbon (EC), which renders a more accurate DPM exposure measurement. Also, this final rule increases flexibility of compliance for mine operators by requiring MSHA's longstanding hierarchy of controls for its other exposure-based health standards at M/NM mines, but retains the prohibition on rotation of miners for compliance. Furthermore, this final rule: Requires MSHA to consider economic as well as technological feasibility in determining if operators qualify for an extension of time in which to meet the final DPM limit; deletes the requirement for a control plan; and makes conforming changes to existing provisions concerning compliance determinations, environmental monitoring and recordkeeping.