“For the first time, coal miners will know in real time how much coal mine dust they are breathing during their shift, so that immediate corrective actions can be taken,” said Joseph A. Main, assistant secretary of labor for mine safety and health. “This marks the next step in our efforts to end black lung disease once and for all.”

Under the second phase of the rule, CPDMs must be used to monitor underground coal mine occupations exposed to the highest respirable dust concentrations, as well as all miners with evidence of black lung. For high-exposure occupations, 15 valid samples must be obtained every quarter, instead of the five samples previously collected every two months, followed by sampling of 15 shifts for other occupations. Finally, operators must post results of CPDM sampling within 12 hours of the sampled shift, and miners with evidence of black lung must be given a copy of the sample data within the first hour of the miner’s next work shift.

Since the final rule went into effect on August 1, 2014, 87,534 dust samples have been collected from 1,363 surface and underground coal mines by MSHA and mine operators. According to MSHA, nearly 99% of those samples met compliance levels.

MSHA said there has been a dramatic decrease in coal miners’ exposure to respirable crystalline silica dust, with rates dropping to nearly half of those that were recorded in 2009, which was the year MSHA launched its “End Black Lung – Act Now” campaign. Respirable coal mine dust levels followed a similar trend, dropping each year since 2009, MSHA added.

“This strategically crafted rule was designed to be feasible and to achieve lower exposures to coal mine dust,” said Main. “It is already delivering positive results.”

The implementation comes after a January 25 U.S. Court of Appeals decision to deny a legal challenge by the National Mining Association and operators seeking to delay it on the grounds that the federal regulator overstepped its authority in issuing the rules. The 11th Circuit Court in Atlanta court rejected the claim and ruled with MSHA.

NMA spokesman Luke Popovich said the decision was disappointing to the group for several reasons.

“First, the court deferred to MSHA’s definition of the problem — something we disagree with. As we have said, this rule was a solution in search of a problem and the court, rather than addressing this, chose to accept MSHA’s definition of the problem,” he said.

“Additionally, the court believes that the consultation process that took place between NIOSH (the National Institute for Occupational Safety and Health) and MSHA is an adequate substitute for the statutory requirements for joint action,” he added. “This is unfortunate, as it diminishes NIOSH’s role in regulatory matters impacting miners’ health and removes one of the checks envisioned by the Mine Act on MSHA’s regulatory powers.”

The third and final phase becomes effective in August. It will lower the dust concentration limit for the dustiest areas of coal mines from 2 to 1.5 milligrams per cubic meter of air.