By changing the unit of measure for DPM exposure to a more accurate one, this rule allows MSHA to enforce protections more effectively for exposed miners, the agency says.
The rule revises the interim DPM concentration limit measured in total carbon to a comparable, but more accurate, permissible exposure limit measured in elemental carbon, according to the agency. This will help ensure that individual miners are not exposed to unacceptable levels of DPM, the agency says.
The former interim level was 400 micrograms of total carbon per cubic meter of air (400TC µg/m3). The new interim level is 308 micrograms of elemental carbon per cubic meter of air (308EC µg/m3).
The rule also gives mine operators additional tools to bring their operations into compliance by employing the "hierarchy of controls" that is used in MSHA's other exposure-based health standards for metal and nonmetal mines, MSHA says. However, the rule retains the prohibition on rotation of miners to achieve compliance.
To view the full text of the final rule, visit MSHA's Web site at http://www.msha.gov.