Between August 1, 2014, when the new final rule took effect, through December 31 — the timeline that represented the outlines’ first phase — more than 23,600 dust samples were collected and about 99% of them were in compliance.

Of the total respirable dust samples collected in the five-month period, 17,949 were taken from 319 underground mines; 252 of those samples (or 1.4%) exceeded compliance levels used to determine if a violation is warranted.

The final rule, Lowering Miners’ Exposure to Respirable Coal Mine Dust, Including Continuous Personal Dust Monitors, significantly increased operator sampling for respirable coal mine dust and also now requires operators to take immediate corrective action when an operator’s sample shows excessive concentrations.

Additionally, MSHA now has authorization to cite operators based on single MSHA samples showing excessive dust, rather than on an average of samples.

“These results show that the new dust rule is working, and miners should be breathing cleaner air at coal mines,” said Assistant Secretary of Labor for Mine Safety and Health Joseph Main. “Despite concerns from some in the mining industry, most of the valid samples collected have met compliance levels. That’s good news for the health of all coal miners and our efforts to end black lung disease.”