Donald L. Rasmussen, a physician who examined thousands of patients with black lung disease, died July 23, 2015, at 87. (Craig Cunningham /Charleston Gazette-Mail)

Donald L. Rasmussen, a physician who helped lead a successful national campaign to win health benefits and safer working conditions for his patients, the thousands of Appalachian coal miners afflicted or threatened by black lung disease, died July 23 at a hospital in Beckley, W.Va. He was 87.

The cause was complications from a fall in May, said his wife, Carmen Rasmussen.

Dr. Rasmussen, a former Army doctor who settled in West Virginia in 1962, was described as an Albert Schweitzer of Appalachia. He devoted nearly his entire adult life to the coal miners of that region and elsewhere who suffered from the preventable, incurable occupational hazard called pneumoconiosis, or black lung disease.

The illness has contributed to more than 76,000 deaths since 1968, according to government data.

Dr. Rasmussen said that during a medical practice that lasted half a century, he examined 40,000 miners who, while extracting coal from the earth or preparing it for human use, risked inhaling the toxic dust that can cause debilitating and ultimately fatal damage to the lungs.

Black lung disease has been compared to torture, an affliction in which victims may experience the sensation of suffocating. Lung tissue, normally pink, turns black. Dr. Rasmussen observed once-strapping miners who, lacking an adequate supply of oxygen, developed shortness of breath so severe that they could no longer work.

Beyond the clinic, he provided the medical gravitas in a movement to obtain compensation for workers with black lung disease and to improve mine conditions so that the illness might be prevented. He expanded diagnostic techniques, appeared before lawmakers and confronted union leaders whom he considered excessively interested in workers’ wages and insufficiently attentive to their health needs.

Amid internecine union warfare, Dr. Rasmussen received death threats, The Washington Post once reported, and for a period he carried a sawed-off shotgun.

Widespread attention was directed to mine safety, or the lack thereof, when an explosion at a mine in Farmington, W.Va., killed 78 people in 1968. The next year, after a weeks-long strike by more than 40,000 miners, Gov. Arch A. Moore Jr. of West Virginia signed legislation recognizing black lung disease as an occupational hazard and making its victims eligible for workers’ compensation.

Days later, Dr. Rasmussen appeared with two like-minded physicians on Capitol Hill. One of them, Isadore Buff, told U.S. senators that “these miners with black lung have a constantly tightened string around their necks. If I had my choice I would rather have lung cancer — it’s quicker.”

Dr. Rasmussen conveyed the scale of the problem.

“Of 202 consecutive miners I autopsied after deaths from all causes,” he said, “I found pneumoconiosis in 80 percent.”

Dr. Rasmussen contended that black lung was more prevalent than was widely recognized, and he was credited with developing blood and exercise tests that revealed its incidence even when the disease did not appear on X-rays.

“The theory that X-ray pictures told the whole story about a miner’s functional capacity was believed so devoutly that no one ever bothered to see if it was true or not,” he told The Post in 1973.

When a scan did not reflect the severity of a patient’s illness, he said, the person was often deemed neurotic. He recalled one miner who was sent to a psychiatrist and died “while taking that same kind of therapy designed to convince him nothing was wrong with him.”

Dr. Rasmussen said he found no pattern of malingering among his patients, a fear among some critics of the compensation programs. Miners commonly enter the profession by force of family tradition and because they have few other opportunities for gainful employment.

“These guys, they don’t know how to give you a sad tale,” said Dr. Rasmussen. “If they tried, you could spot it easy as could be. All you have to do is sit down and talk to them, and you know darn good and well that they’ve got problems.”

In 1969, President Richard M. Nixon signed the Federal Coal Mine Health and Safety Act, landmark legislation promoted by U.S. Rep. Ken Hechler (D-W.Va.) that established limits for permissible dust levels in mines and provided benefits for disabled victims of black lung disease.

The incidence of the condition gradually decreased, but in recent years, investigations by news media have revealed signs of resurgence, perhaps fueled by the greater power of modern machines to dig into layers of rock, releasing more coal dust and other harmful substances.

In 2014, Chris Hamby of the Washington-based Center for Public Integrity received a Pulitzer Prize for a series of investigative reports on how some doctors and lawyers had improperly denied benefits to miners suffering from black lung disease.

“In 1969, I publicly proclaimed that the disease would go away before we learned more about it,” Dr. Rasmussen told the Charleston, W.Va., Gazette in 2012. “I was dead wrong.”

Donald Lloyd Rasmussen was born in Manassa, Colo., on Feb. 24, 1928. The son of a veterinarian, he graduated from the University of Utah medical school in 1952 and joined the Army as a physician.

He came to West Virginia, he said in a 2012 oral history, after seeing a notice in the Journal of the American Medical Association advertising the need for doctors at what was then called Miners Memorial Hospital in Beckley. He later conducted his work with the Public Health Service and in 1969 received a presidential citation from the American Public Health Association.

Dr. Rasmussen was married several times. Besides his wife of 29 years, the former Carmen Stone, survivors include several children and stepchildren; a brother; two sisters; and numerous grandchildren and great-grandchildren.

“I never felt I was leading a charge,” Dr. Rasmussen once told the Beckley Register-Herald. “I never saw myself as a crusader or advocate. I saw the coal miners who needed help, and I just told what I had learned while working with them. It was all in the scope of my job. I was just a physician performing my duty.”