Killer Smog Marker

Donora, Pennsylvania

In October 1948, the Donora Valley was the site of a deadly smog, the result of a temperature inversion on a lot of dirty air -- specifically fluorine gas -- produced by the Donora Zinc mill. People began dying on October 27, but it wasn't until October 31 that the mill owners shut down the plant. It rained that night, clearing the air, and the next day the mill was back in operation.

Twenty people died in a span of five days, and another 50 died within the following month.

Fifteen years later, the memory of the Donora Smog was credited with helping to pass federal legislation known as the Clean Air Act. Three years later the zinc mill was shut down, and on the 50th anniversary of the Killer Smog a historical marker was erected in Donora, outside the town library.