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On October 24, 1948, 18 people died within 12 hours due to a temperature inversion that trapped the emissions of Donora's steel mills. rather than dispersing high into the atmosphere as normal, the pollution generated from the town's zinc works and blast furnaces stayed near the ground level, creating a thick fog that contained lethal amounts of sulfuric acid, nitrogen dioxide, fluorine, and other poisonous gases. In addition to a historic marker, there is a small local history museum at this location that preserves and shares the history of Donora and the tragedy that trapped residents in a deadly smog. The museum tells both the story of the 21 people who died within the first three days of the incident, but also the heroic response of first responders, medical personnel, and neighbors. The museum also presents the history of other industrial disasters and their consequences.

  • The Donora Smog Museum opened in 2008, the sixty-year anniversary of the 1948 tragedy.
  • This historic marker was dedicated in 1995, the culmination of a revival of interest and awareness of the incident that began with the work of a local high school student. The monument is located at Meldon Avenue and Fifth Street.
  • This historic photo shows the town of Donora near the time of the tragic temperature inversion that trapped industrial pollutants in 1948.
  • To learn more about the 1948, read Killer Smog: The World's Worst Air Pollution Disaster by William Wise. Click the link below to learn more about this book.
As the week of October 24, 1948 began, the nearly 14,000 people of Donora paid little attention to the dense heavy fog covering the town. The cool to cold autumn nights combined with warm water from the Monongahela river and smoke from the local steel mill, namely the zinc works, blast furnace and open hearth, as well as thousands of coal furnaces in local homes, would typically limit visibility until afternoon (see photo above). But as the week wore on, residents began to realize this fog was anything but typical. By Thursday, October 28, street lights were on during mid-day (see photo below) and people walking the streets were struggling to find their way. Soon, many elderly people began to complain of breathing difficulty, thousands were ill, and house plants began to shrivel. Then, people began to die.

Donora physicians worked around the clock, treating victims as best they could against a mysterious pathogen. The Donora Board of Health set up an emergency aid station and temporary morgue in the basement of the Community Center. Volunteer firemen felt their way door to door, administering oxygen and attempting to get people help. Management at the mill refused to believe or admit that the waste they were emitting caused the problem; after all, it was the same thing they had been doing for over thirty years.

In less than three days, hundreds of people fell sick, twenty-one people were dead, along with dozens of animals. Who knows how many more followed in the weeks, months and years to come. On October 31, rains finally dispersed the killer fog, but leaving the nation in shock. The dead and sick were not only from Donora but also from the neighboring communities of Webster and Sunnyside that were down wind and across the river.

The Federal, State and Local governments, along with numerous universities and scientists, conducted an investigation. Sulfur dioxide emissions from U.S. Steel's Donora Zinc Works and its American Steel & Wire plant were frequent occurrences in Donora. What made the 1948 event more severe was a temperature inversion, in which a mass of warm, stagnant air was trapped in the valley. The pollutants in the air mixed with fog to form a thick, yellowish, acrid smog that inhibited the normal process where the sun would burn off the fog. This smog hung over Donora for five days. The sulfuric acid, nitrogen dioxide, fluorine and other poisonous gases that usually dispersed into the atmosphere were caught in the inversion and continued to accumulate until rain ended the weather pattern.

The killer fog introduced America to a new term: "smog" - a combination of naturally occurring fog and industrial pollution. The 1948 Donora Smog made the world aware of the dangers of unchecked pollution. The tragic and heroic events of that October weekend helped shape the environmental movement that was to follow.
Donora Historical Society: Erin Peterman, A Cloud With a Silver Lining: The Killer Smog in Donora, 1948, The Atlantic, Spring 2009.