People in the mining camps of the Appalachian coal fields know the perils of the industry upon which, for generations, their fragile communities have depended.
The evidence cannot be ignored. It is around them in those mountain hamlets every day of their lives.
They hear it in the rasping coughs of gray-faced men, driven from the pits with lungs lacerated by years of breathing coal dust.
They see it in the shuffling gait of neighbors broken, disabled - often missing limbs - the victims of roof falls and mechanical mishaps.
They share the grieving of widows and fatherless children.
And always - all their days - they wait to hear the rumble and feel the shudder of the earth, which tells that somewhere, deep in its heart, the mountain has shifted and swallowed their husbands, their brothers and their sons.
I say this from firsthand observation. Nearly 40 years ago I lived a month with a miner and his wife in one of a little cluster of former company houses, overlooked by the slag mountain of a long-closed mine.
The name of the place was Lookout, Ky., and it was situated in Poor Bottom Hollow beside a foul little creek choked with rusted bedsprings, car parts and the corpses of discarded refrigerators.
I spent days with some of the older miners of the neighborhood. I saw the hideous damage to the landscape that mining had done. But worse by far was the human damage.
The alliance between local politicians and the coal industry was a devil's bargain that had impoverished and left powerless the residents of Poor Bottom and the neighboring valleys.
I thought of them when I read of the probable methane gas explosion last Monday in a mine in West Virginia that left 29 dead and two injured. Odorless, invisible and highly combustible, methane is one of the particular hazards in the deep mining of coal.
The mine where the calamity occurred had a dismal record of citations for safety violations. And though recent decades have seen efforts at better regulation and sterner enforcement, mining coal remains among the most dangerous of U.S. occupations.
Chinese miners face even greater risks. That country's safety record is one of the world's worst. And it was there, a week before the West Virginia explosion, that more than 150 were trapped in a flooded mine, although at this writing all but 38 had been pulled to safety.
Those two disasters in so short a time, along with the memories from my weeks in that Kentucky country of damaged men, caused me to consider the real cost of coal.
One hears it endlessly celebrated as our most abundant energy resource. Without coal power generation, it's claimed, offices would go dark, houses cold and factories silent.
Not only is it plentiful, we're told, it's wonderfully cheap.
But cheap is a matter of definition.
When I remember those days in Poor Bottom Hollow and the friends I made there, or when I imagine the anguish of those families waiting for terrible news at the West Virginia pithead, it alters the calculation.
A serious proportion of the power that furnishes the light over the desk where I'm writing this, the energy that will turn the press to print it, and the light under which perhaps you'll read it is generated by burning coal.
But that only partly describes the process. For when coal is burned, we're also burning lives.
In the future, with determination and American resourcefulness, surely we will find a better way.