The group, led by Cook County Health and Hospitals System lead researcher Dr Robert Cohen, released its report after a presentation at the American Thoracic Society annual conference on the weekend.

Families for seven of those killed allowed lung tissue to be obtained from autopsies. The team said six of those samples indicated black lung.

“Our pathology – where we actually see the lung tissue, we actually see the scars, we see the dust – confirms we’re seeing a problem,” Cohen said, noting that one of the six showed a fairly advanced form of the disease.

In its description of those studied, the researcher said that one had worked for less than five years underground. Several had worked about a decade in the industry.

The tissue samples were from miners ranging in age from 30 to 60.

Cohen said the young age of some of the miners as well as their limited exposure to the underground environment “means that there were probably some intense exposures and excessive exposures over a short period of time … [and] that raises some concerns”

The team, which did not release the identities of those tested due to confidentiality agreements with the families, said in the report that the level of pneumoconiosis was first discovered in the group just after the blast, when a state medical examiner told investigators that, of the 24 with sufficient amounts of tissue to test, 71% had black lung.

The rate is 10% higher than average for the southern West Virginia region.

Cohen and his team were commissioned for the study by industry mine safety veteran Davitt McAteer, a former federal mine safety chief.

He said at the time that he found the autopsy results shocking because of “the number of miners who showed evidence of black lung, particularly among younger miners and miners who you would not have expected to have black lung”

Cohen acknowledged that the sample size for the group’s testing was limited.

“It’s a small number of miners,” he said.

“But the miners who were referred to the study were a random sample – people who just happened to be working in that mine that day who were killed in the disaster.”

The researchers also noted the findings of several investigations of UBB, some of which said that then-mine owner Massey Energy had permitted dangerous accumulations of coal dust in the mine.

“Mines that tend to have accidents do tend to be less clean than mines that don’t have accidents,” Cohen said.

“[UBB] may be representative of a number of mines in the United States today.”