Three signal flares went up for the American coal industry recently, all illuminating an inescapable conclusion: Despite President Trump’s campaign promise, coal-fired power is in trouble and in all likelihood won’t be reasserting itself in the United States. Nor should it.

The first signal, from the medical community, should give champions of “beautiful, clean coal” like Mr. Trump and his energy secretary, Rick Perry, pause. A research letter published in the Journal of the American Medical Association on Feb. 6 said that health professionals in Appalachian coal country were now finding the highest levels of black lung disease in coal miners ever reported.

The Coal Workers’ Health Surveillance Program, administered by the National Institute for Occupational Safety and Health, or Niosh, has offered regular chest radiographs for coal miners since 1970. By the late 1990s, black lung disease was “rarely identified” among miners participating in the program, researchers wrote. But a spike in cases in 2014, first reported by National Public Radio, prompted the federal agency to take a closer look at patients at three federally funded black lung clinics in southwest Virginia.

The agency was stunned by what it found. Black lung cases in Appalachia coal miners in those three clinics had skyrocketed. The disease was more severe. And coal miners were dying much younger than they had been two decades ago.