The study adds to the arguments by the Obama administration in favor of its proposal to toughen the legal limits for coal dust allowed in underground mines, according to one of the lead authors.

"This is no longer something we can just sit on our hands about," said Dr. Edward L. Petsonk<co >, a WVU physician and black lung expert who wrote the new study with Dr. W. Alex Wade, a pulmonary fellow at the WVU School of Medicine.

The study is being published in Chest, the peer-reviewed journal of the American College of Chest Physicians. A summary is available online and Petsonk discussed the paper in a presentation last week at Wheeling Jesuit University's fourth annual International Mining Health and Safety Symposium.

"This report points out the continuing toll in severe disease and death caused by exposure to coal mine dust and highlights the urgency of acting to end black lung," said Dr. Greg Wagner, deputy assistant secretary for policy at the U.S. Mine Safety and Health Administration.

The study examined progressive lung disease in 138 West Virginia coal miners whose benefit claims were approved by the state Occupational Pneumoconiosis Board between January 2000 and December 2009.

It found the disease progressed in an average of 12 years from normal chest X-rays until progressive massive fibrosis, or PMF, was detected. The board confirmed 21 deaths among the group, the study said.

"Contemporary occupational dust exposures have resulted over the last decade in rapidly progressive pneumoconiosis and massive fibrosis in relatively young West Virginia coal miners, leading to important dysfunctional and premature death," according to the study summary.

Black lung, or coal workers' pneumoconiosis, is actually a collection of debilitating and potentially fatal ailments caused by breathing coal dust.

In 1969, Congress made eliminating black lung a national goal, with a law that required mine operators to take steps to limit exposure. The law greatly reduced black lung among the nation's coal miners. But still, nearly 10,000 coal miners nationwide have died in the last decade from black lung.

And more recently, scientists have found that black lung is on the rise again. Researchers have warned of a doubling of black lung rates since 1997, and of alarming incidents of the disease among younger miners whose entire careers took place under the 1969 law's dust limits.

Last October, MSHA proposed to toughen limits on coal dust exposure as part of a broad plan Obama administration officials hope will eliminate black lung.

MSHA chief Joe Main also proposed to require more advanced continuous monitoring and more accurate sampling methods to better estimate exposure and protect miners from the disease.

But coal industry officials and some of their political allies have criticized the Obama proposal. Sen. Rand Paul, R-Ky., has said there's no need for the tougher rules because the industry has already done "a pretty good job" of dealing with black lung.

UMW President Cecil Roberts said Paul is wrong about the black lung rules, but that he wasn't surprised to hear his statements about the matter.

"He doesn't believe in any law or any regulation that inhibits business in any way," Roberts said Friday. "He's just wrong on that."

Richard Whiting, president of Patriot Coal, said the industry doesn't oppose MSHA's entire proposal, but wants the agency to allow coal operators to supplement improved mine ventilation and dust-suppressing water sprays with respirator helmets.

Reach Ken Ward Jr. at kw...@wvgazette.com or 304-348-1702.