The MSHA proposal, which now faces public review and comment, would phase in the 1.0-milligram dust limit over a two-year period. Mine operators would have to begin using "continuous personal dust monitors" to more accurately measure actual dust exposure for individual miners.
MSHA also proposes to redefine the sampling rules to more accurately represent longer hours miners work today, and to stop averaging of samples from multiple shifts -- a technique that critics say could mask over-exposures.
The MSHA plan, initially announced in December 2009, also includes more education and training for miners and mine operators, as well as tougher enforcement of dust-control standards.
"I think it's terribly important to ramp up enforcement as it relates to coal dust," said Davitt McAteer, who ran MSHA during the Clinton administration. "There is ample evidence that this has been a problem for years."
The National Mining Association reacted more cautiously, repeating its support for continuous dust monitors, but not yet backing the idea of tightening the dust limits.
"Our initial view is this is an aggressive approach that will require a comprehensive suite of technologies," the association said in a statement. "In addition, operators will need to employ an equally broad range of workplace practices."
MSHA estimated that the compliance costs for industry at between $72.4 million and $93.2 million the first year and between $40 million and $44.5 million each year after that.
Agency officials put the annual benefits -- from thousands of reduced illnesses and deaths -- far higher: between $99 million and $197 million per year, depending on how the figure is calculated.
But in its regulatory proposal, MSHA noted, "it is difficult to gauge the timing of reductions in chronic diseases that may not develop until years after initial exposure, and whose progression may not be instantly stopped even if exposure were completed eliminated."
"We aren't going to be able to end black lung with this rule overnight," said Dr. Greg Wagner, deputy assistant labor secretary for MSHA. "It's going to be a gradual process."
Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.