On October 27th, 1948, the residents of Donora, PA, awoke to a thick blanket of yellow smog. That was not unusual for this mill town, but this time, the stinging air didn’t lift. It burned people’s eyes and throats and darkened the valley for five straight days.

Before it dissipated, 27 people had died from the toxic air. Many more had life-long repercussions. Dr. Devra Davis, environmental health expert, Donora native, and author of When Smoke Ran Like Water, tells us how Donora slowly awakened America’s need for the Clean Air Act, and why we need it just as much today.