Ecological disaster in Donora, Pennsylvania.

The 1948 Donora smog, also called the Donora death fog, was an air pollution disaster that occurred in Donora, Pennsylvania, beginning on October 27, 1948 and lasting several days. It was caused by hydrogen fluoride and sulfur dioxide emissions from U.S. Steel's Donora Zinc Works and its American Steel & Wire plant during an atmospheric temperature inversion. It killed 20 people and caused respiratory problems for 6,000 of the 14,000 people living, a mill town on the Monongahela River 24 miles (39 km) southeast of Pittsburgh. The event is commemorated by the Donora Smog Museum.

Donora is a borough in Washington County, Pennsylvania, United States, approximately 20 miles (32 km) south of Pittsburgh along the Monongahela River. The population was 4,558 as of the 2020 census.

October 28 is the 301st day of the year in the Gregorian calendar; 64 days remain until the end of the year.