Potassium iodide pills are often given out during nuclear emergencies, actual or imminent. In late August, for example, the European Union pledged to preemptively donate more than five million anti-radiation tablets to Ukraine, amid fears of a Chernobyl-level catastrophe at the Russian-occupied, embattled Zaporizhzhia nuclear power plant.

But for Claudia Peterson, 67, and her peers growing up near Cedar City, Utah, iodide pills were part of their routine—like recess, or homework, or reciting the pledge of allegiance. The ones given to students at her elementary school were big and orange, she recalls.

Another part of the routine: the men in suits who showed up at the school toting Geiger counters. “They would come up to our faces and run this machine over