On Monday, the U.S. Mine Safety and Health Administration is dropping the allowable respirable dust level from 2 milligrams per cubic meter to 1.5 milligrams per cubic meter of air.
The agency says almost 99 percent of recent coal dust samples are already meeting the new standard.
The coal industry had challenged the new limits, arguing that the monitors had a high failure rate. Federal mine safety officials said the results show the new rules are effective.
The National Institute for Occupational Safety and Health estimates black lung caused or contributed to deaths of more than 76,000 miners.