Yes, the Ohio train wreck is an environmental disaster. No, it’s not Chernobyl.

The images from East Palestine, Ohio, earlier this month are frightening. They show a giant tower of thick, black smoke rising from a train wreck and expanding into the horizon, as if a bomb went off.

The description of what happened isn’t much less worrying: A large train derailed that was carrying hazardous chemicals, and some of them leaked into the air, water, and soil. To avert an explosion, authorities purposefully detonated a chemical called vinyl chloride, which caused the dark plume.

It looks bad. It sounds bad. So, how bad...