MSHA this week issued a final rule strengthening protections for miners exposed to diesel particulate matter (DPM) from diesel exhaust in underground metal and non-metal mines.

The rule revises the interim DPM concentration limit measured in total carbon to a comparable, but according to MSHA a more accurate, permissible exposure limit measured in elemental carbon.

The former interim level was 400 micrograms of total carbon per cubic metre of air. The new interim level is 308 micrograms of elemental carbon per cubic metre of air.

MSHA said changing the unit of measurement for DPM exposure would allow MSHA to enforce protections more effectively for exposed miners.