CHARLESTON, W.Va. -- The Obama administration is continuing to delay action on several key mine safety and health rules, including one aimed at ending deadly black lung disease, according to a new regulatory agenda made public this week. Officials announced the moves in the Department of Labor's semiannual regulatory agenda, which was published online Wednesday. The department's Mine Safety and Health Administration said in its portion of the agenda that a rule aimed at lowering exposure to coal dust that causes black lung won't be finalized until at least September. MSHA's previously listed target date for the final rule was June. Agency officials did not state a reason for the delay, and a department spokesman did not respond to a request for comment. The delay comes as researchers continue to warn of a "sense of urgency" to take action because of a resurgence in black lung, especially in Appalachia and among younger miners, who have worked under current dust limits that were supposed to protect them from the disease. Black lung, or coal workers' pneumoconiosis, is an irreversible and potentially deadly disease caused by exposure to coal dust. Between 1996 and 2005, nearly 10,000 coal miners nationwide died of black lung, according to the National Institute for Occupational Safety and Health. West Virginia recorded the second-most black lung deaths of any state, with more than 1,800 during that period, according to NIOSH. That compares to 87 miners killed in on-the-job accidents during that same period, according to federal data. A year ago, in July 2012, a joint investigation by National Public Radio and The Center for Public Integrity, a Washington, D.C.-based nonprofit investigative journalism organization, reported on the resurgence of black lung and, with additional reporting by The Charleston Gazette, documented widespread cheating by mining companies on dust samples and inaction by federal regulators over the past quarter-century to address the problem. In October 2010, MSHA proposed new rules as part of what the agency touted as an aggressive plan to end the disease. Among other steps, the MSHA proposal would reduce the legal limit for dust in underground mines from 2 milligrams of dust per cubic meter of air to 1 milligram of dust per cubic meter of air. A Labor Department advisory commission recommended the change in 1996, and NIOSH has been urging since 1995 that the limit be tightened. Industry officials argue that recent increases in black lung rates are a regional problem and don't require a new nationwide rule. In August 2012, the federal Government Accountability Office issued a major report that supported MSHA's proposal to toughen coal dust limits to fight a resurgence of black lung. That GAO report's findings ended a block by congressional Republicans on the issuance of the final MSHA rule. Since the GAO report, though, MSHA has reported no significant actions on its proposed rule. A final version has not been recorded as being filed with the White House Office of Management and Budget -- where a review could take months -- and MSHA officials refuse to say much about the topic. The latest MSHA regulatory agenda also indicates that the agency is delaying a final rule to require underground mine operators to equip continuous-mining machines with devices meant to protect miners from being run over or crushed by those machines. That rule was to be finalized by May but has been delayed until August, the regulatory agenda says. A separate proposed rule to require these "proximity detection" devices on other underground equipment was delayed from July to November. The new MSHA regulatory agenda also says the agency plans a new initiative to seek comments on issues related to the April 2010 explosion that killed 29 miners at the Upper Big Branch Mine in Raleigh County. "The request for information will request data, comments, and information on issues related to rock dusting, ventilation, mine examinations, certified persons and MSHA-approved instructors," the regulatory agenda said. MSHA doesn't plan to publish the request for comments until October. Reach Ken Ward Jr. at firstname.lastname@example.org or at 304-348-1702.