Black lung disease, known formally as coal workers’ pneumoconiosis, is making a comeback, according to a study linked to the federal Centers for Disease Control and Prevention. That is — or should be — unacceptable.

Too many West Virginia and Ohio families are all too familiar with black lung, caused by inhaling coal dust. It is a debilitating disease that can kill after causing years of suffering.

For years, it was thought improved methods of controlling dust levels in mines had made a big dent in black lung. Common sense would indicate that must have helped.

But a study published in the American Journal of Public Health concludes black lung has made a resurrgence, at least in West Virginia, Kentucky and Virginia. Researchers found that about 20 percent of miners with 25 or more years of experience in those states have contracted the disease — and it has progressed to the point of massive fibrosis in the lungs.

Among veteran miners in the three states, then, one in five has serious black lung problems.

One clue as to what is going on may be provided by statistics from elsewhere. Nationally, the average of black lung among experienced miners is 10 percent. That still is an unacceptable level, but at half the rate in the three states cited, it is much better.

Three researchers with the National Institute for Occupational Safety and Health, part of the CDC, conducted the study. Lending credence to their work is the fact it is not the first evidence of a new black lung challenge. A 2014 NIOSH study showed that after hitting a low in 2000, the rate of black lung cases seems to be on the upswing.

The obvious question is why. What is it that, despite intensive efforts to curb the disease, has permitted it to come roaring back?

Jumping to conclusions about that could be dangerous. Taking preventive action based on flawed assumptions could divert attention and resources from the real culprit(s).

Federally backed studies of the incidence of black lung have been made. Now, it is time to move on to finding out what is behind the scourge.