Congress intended to eradicate the disease known as black lung with a landmark 1969 law that limited underground coal miners' exposure to dust.
Roger Cook can tell you that didn't happen -- but only if he pauses mid-sentence to take a labored breath.
Mr. Cook, 57, has black lung even though he started his 32 years as an underground miner in 1978, well after the new standards were put in place. He is among a growing number of eastern Kentucky miners afflicted with black lung, reversing a decades-long decline of the torturous, incurable disease.
The Letcher County, Ky., man had to quit the mining job he loved in April 2010 when he was diagnosed with black lung, which scars the lungs, impairs breathing and often leads to premature death. He now relies on an oxygen tank to help him breathe 24 hours a day, and he still gets short of breath even while sitting.
Breathing coal and rock dust at coal mines can cause various lung ailments, including black lung -- the common term for coal workers' pneumoconiosis -- and silicosis.
Black lung has been the underlying or contributing cause of death of more than 76,000 miners since 1968, according to figures from the National Institute for Occupational Safety and Health. That total does not include deaths from silicosis, which is caused by breathing dust from rocks such as sandstone.
Before the 1969 mine safety act, more than 40 percent of longtime miners in some regions of the United States got black lung, according to NIOSH data.
Overall, 11.2 percent of underground coal miners screened for black lung from 1970 to 1974 had the disease.
Prevalence of black lung declined steadily for several decades, dropping to 2 percent in screenings conducted from 1995 to 1999, NIOSH said in a May 2011 report. Then, mysteriously, it rebounded. Screenings in 2005 and 2006 found the disease in 3.3 percent of surveyed miners.
In addition, NIOSH has documented that miners are developing advanced cases of lung disease at younger ages, and that there has been a bigger surge of black lung among miners in central Appalachia than elsewhere.
In eastern Kentucky, 9 percent of the miners screened in one NIOSH program between 2005 and 2009 had black lung. It was the highest prevalence of any state.
NIOSH has identified a number of possible reasons for the black lung resurgence, including routine work shifts of 10 to 12 hours for miners; increased mining of thinner coal seams in central Appalachia, which requires cutting through more rock; inadequate dust-control rules; and failure by coal companies to comply with the rules.
Safety advocates and miners also lay blame on companies that cheat on the dust samples they are required to submit to federal regulators, although they say that problem was worse in the past.
In 1991, the U.S. Mine Safety and Health Administration, or MSHA, cited more than 840 coal companies for alleged cheating on dust sampling during a widespread investigation.
That didn't stop the problem, according to former miners and attorneys who handle miners' black-lung claims. They tell stories of companies recording fraudulent dust levels by hanging monitors in the clean-air intake, covering monitors with cloth, and even putting them inside lunch buckets.
In its May 2011 study, NIOSH used data from coal companies' dust samples to predict the prevalence of black lung, then compared the predictions to the X-rays of more than 12,000 miners.
The prevalence of black lung was four times higher than predicted in eastern Kentucky, the report said. Other regions of the country did not show a similar gap.
The National Mining Association is not aware of cheating by coal operators, and it should not be happening, senior vice president Bruce Watzman said.
The association's position is simple, he said: "Operators are expected to comply with the law and the regulations."
In the 12 months ending March 1, MSHA issued 146 citations for excessive dust in underground mines, and 339 for failing to submit ventilation plans.
"As a whole in the industry, ventilation is a joke in underground mines," said lawyer Timothy C. Bailey of Charleston, W.Va., who represents miners in black-lung cases.
MSHA chief Joseph A. Main has said current rules are not adequate to protect miners. For instance, miners wear dust monitors for only eight hours, even though they might work longer shifts; companies can slow production to generate less dust when dust samples are taken; and MSHA uses an average of five samples to gauge compliance.
The agency has proposed a number of changes, including lowering the limit on miners' exposure to coal and silica dust; requiring miners to wear personal monitors to provide real-time dust readings; using a single, full-shift sample to measure compliance; and keeping production closer to normal levels while sampling.
The coal industry opposes the changes.
The National Mining Association argues that the spike in coal miners' lung disease is limited to central Appalachia and doesn't justify an industry-wide rule change. The association argues that the real culprit is increased exposure to higher levels of silica from sandstone and other rocks, and that MSHA should focus on fixing that problem at the regional level.