Federal investigators this month identified the largest cluster of advanced black lung cases ever officially recorded.

More than 400 coal miners frequenting three clinics in southwestern Virginia between 2013 and 2017 were found to have complicated black lung disease, an extreme form characterized by dense masses of scar tissue in the lungs.

Healthy lung Simple black lung disease Complicated black lung disease Simple black lung disease Complicated black lung disease Healthy lung Simple black lung disease Complicated black lung disease Healthy lung Healthy lung Simple black lung disease Complicated black lung disease National Institute for Occupational Safety and Health

The cluster, identified following an investigation by National Public Radio, adds to a growing body of evidence that a new black lung epidemic is emerging in central Appalachia, even as the Trump administration begins to review Obama-era coal dust limits.

The severity of the disease among miners at the Virginia clinics “knocked us back on our heels,” said David J. Blackley, an epidemiologist at the National Institute for Occupational Safety and Health, who led the research published in the Journal of the American Medical Association. It was equally troubling, he said, that nearly a quarter of the miners with complicated black lung disease had been on the job fewer than 20 years.

Across the coal belt in Kentucky, West Virginia, and Virginia, “there’s an unacceptably large number of younger miners who have end-stage disease and the only choice is to get a lung transplant or wait it out and die,” Dr. Blackley said.

Scientists have linked the new wave of lung disease to miners breathing in more silica dust, the likely result of a decades-long shift toward mining thinner coal seams that require cutting into the surrounding rock. Silica dust from pulverized rock can damage lungs faster than coal dust alone.

Modern machinery, insufficient training for workers, and longer work hours may also contribute to increased dust exposure, experts say.

A Sharp Rise in Complicated Black Lung Disease

Black lung, a chronic disease caused by breathing in coal mine dust, declined precipitously between the early 1970s and late 1990s, following new health and safety rules put in place by the 1969 Coal Act. The legislation for the first time established airborne dust limits in coal mines and set up a health monitoring program for working miners, offering free chest x-rays every five years.

But by 2000, black lung was on the rise again. An advanced form of the disease, rarely seen in the mid-1990s, made an especially dramatic comeback.

Complicated Black Lung DiseasePer 1,000 working coal miners in Kentucky, Virginia and West Virginia Rate of complicated black lung among working coal miners in Kentucky, Virginia and West Virginia 50 cases per 1,000 miners 48.5 40 30 20 10 3.7 1975 1980 1985 1990 1995 2000 2005 2010 2015 50 cases per 1,000 miners 48.5 40 30 20 10 3.7 1975 1985 1995 2005 2015 51.4 48.5 32.7 25.3 19.1 19.1 13.0 3.7 cases per 1,000 miners 1975 1980 1985 1990 1995 2000 2005 2010 2015 Data represents a five-year moving average among underground miners with at least 25 years on the job who participate in the Coal Workers’ Health Surveillance Program. Source: National Institute for Occupational Safety and Health

The upward trend in severe black lung disease has been clear for some time, but “what we’re really learning now is the magnitude of the problem,” said Carl Werntz, an associate professor of occupational medicine at West Virginia University, who treats miners in Morgantown.

In addition to the Virginia cluster, Dr. Blackley’s team previously found 60 miners with complicated black lung at a single clinic in eastern Kentucky. Overall, investigators have confirmed nearly 500 cases in just four clinics over the past four years. NPR, which began a wider survey of clinics in 2016, has unofficially recorded nearly 2,000 cases over a similar time period.

Those figures are far higher than the federal government’s voluntary screening program for working miners, which recorded fewer than 100 cases of complicated black lung disease nationwide between 2011 and 2016. Researchers note that the true extent of black lung disease among current and former coal miners remains unclear.

New Rules for Coal Dust Under Review

To combat black lung disease, the Obama administration in 2014 issued a new coal dust rule. It lowered dust exposure limits for the first time in four decades, increased sampling frequency and required the use of real-time personal dust monitoring devices.

The rule was challenged by coal industry groups as costly and overly burdensome. A federal appeals court upheld it in 2016.

Last December, the Trump administration announced a retrospective review of the four-year-old regulation as part of a broader rule-cutting agenda, a move that alarmed mine safety advocates and medical experts.

“In light of these trends showing more debilitating disease, we need more protection, not less,” said Judith Graber, an assistant professor at the Rutgers School of Public Health.

A Mine Safety and Health Administration spokesperson said that the agency’s review was required and “will be used to determine if the 2014 rule is achieving its desired result.” David Zatezalo, a former miner and coal industry executive who now leads the agency, told Congress on Feb. 6 that he has no current plans to roll back the updated dust limits.