The number of coal miners diagnosed with severe black lung disease in central Appalachia has increased to levels not recorded since the 1970s, according to a new report.



The report released by the National Institute for Occupational Safety and Health, a division of the Centers for Disease Control and Prevention, says cases of black lung have surged in the region faster than previously thought.



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The study comes as the coal industry is fighting the Obama administration over more stringent coal-dust rules.Severe black lung cases reached 3.2 percent in West Virginia, Virginia and Kentucky in 2012, according to the study published Monday in the American Journal of Respiratory and Critical Care Medicine.That's up from .4 percent in 1998. In 1974, black lung among miners was at 3.3 percent for the same states. The federal government began regulating coal dust 40 years ago, placing today's levels equal to those before rules were enacted.Researchers note that stronger machines used to grind coal into finer particles could cause the increase, as well as a change in the composition of the dust.