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President Donald Trump has promised to return the U.S. coal sector to its glory days.

Experts say that isn't likely to happen, given the nation's shift toward natural gas and renewable energy. But if the coal sector does rebound, it'd be a boon for thousands of laid-off miners and struggling coal towns.

Yet those jobs won't come without certain risks for workers — not to mention a boost in carbon emissions and toxic air pollutants.

Blood on the Mountain, a documentary now available on iTunes and DVD, highlights a litany of health problems that coal miners face, particularly when their employers slack on safety measures.

In the clip shown here, West Virginia miners discuss their battle with "black lung," a disease that develops from long-term exposure to coal dust.

An Ohio coal miner shakes hands with U.S. President Donald Trump on Feb. 16, 2017. Trump signed a bill disapproving the Stream Protection Rule to reduce environmental damage from surface coal mining. Image: Ron Sachs-Pool/Getty Images



The documentary, out soon on Netflix, relies mostly on archival footage for this segment. But the disease remains a problem for modern coal miners.

So far this decade, 962 cases of black lung were recorded at 11 clinics in Virginia, West Virginia, Pennsylvania and Ohio, NPR reported last December. Their investigation found that cases are 10 times more prevalent than federal regulators had previously reported.

Blood on the Mountain had a limited theatrical release in 2016, to somewhat mixed reviews.

A New York Times critic called it "one-sided" and a "clumsily made attack on the coal industry," but acknowledged that the film serves as a "reminder that the 'coal equals jobs' equation is a serious oversimplification." A more positive review in the Los Angeles Times said the documentary is "practically a textbook about how ravenous corporations and feckless government can strip-mine the souls of workers."