The Mine Safety and Health Administration (MSHA) is proposing to cut in half the exposure limit for coal dust, the cause of black lung disease. MSHA estimates the new standard will prevent thousands of illnesses and hundreds of deaths over the lifetimes of miners.

“The proposed rule would lower the existing concentration limits for respirable coal mine dust from 2 milligrams of dust per cubic meter of air, or 2 mg/m³, to 1 mg/m³ over a 24-month phase-in period,” MSHA said yesterday. The 1mg/m3 standard is consistent with recommendations made by a Department of Labor advisory committee and by the National Institute for Occupational Safety and Health (NIOSH), both from the 1990s. MSHA is also proposing to change the way coal dust is monitored. According to former MSHA official and mine safety expert Celeste Monforton, the proposed rule would “change the way miners' exposure to coal dust is measured from an average over five shifts to a single, full-shift sample (consistent with standard industrial hygiene practice) and monitor of coal dust levels based on typical production levels in the mine.”

Prolonged exposure to coal dust can cause coal workers' pneumoconiosis (CWP), commonly referred to as black lung, which leads to serious pulmonary problems and, in the worst cases, death. Although long recognized as a serious but preventable risk, incidents of black lung are actually on the rise, according to NIOSH.

The preamble to the proposed rule says that the changes would prevent more than 2,800 cases of CWP, almost 800 cases of progressive massive fibrosis (a progressive form of CWP), almost 700 cases of severe emphysema, and 131 deaths from non-malignant respiratory disease, all over a 45-year work life.

MSHA has proposed new standards for black lung in the past but failed to finalize them. “During the Clinton and the GW Bush Administration, MSHA proposed rules addressing these same problems, but they were never issued as a final rules,” Monforton said. “I'm hopeful this third time will be the charm.”

MSHA is developing the standard as a part of its “End Black Lung – Act Now!” initiative, the goal of which is to eliminate black lung disease. MSHA will publish a notice of proposed rulemaking in the Federal Register on Oct. 19 (until then, it’s available here) and accept public comments on the standard until Dec. 18.