There are no "externalities," of course; the world is round. That said, from Reuters:

The United States' reliance on coal to generate almost half of its electricity, costs the economy about $345 billion a year in hidden expenses not borne by miners or utilities, including health problems in mining communities and pollution around power plants, a study found.

Those costs would effectively triple the price of electricity produced by coal-fired plants, which are prevalent in part due to the their low cost of operation, the study led by a Harvard University researcher found.

"This is not borne by the coal industry, this is borne by us, in our taxes," said Paul Epstein, a Harvard Medical School instructor and the associate director of its Center for Health and the Global Environment, the study's lead author.

"The public cost is far greater than the cost of the coal itself. The impacts of this industry go way beyond just lighting our lights."

 Yep!