During the night of October 26, 1948, a warm air mass from the west drifted toward the Monongahela River in southwest Pennsylvania, stalling at a loop in the river and resting on the town of Donora. People woke up on the morning of the 27th to a heavy yellow smog – so heavy that lights had to be kept on all day.
Donora was a small mill town of about 14,000, most of whom worked for the American Steel and Wire plant or the Donora Zinc works. Because it sits in a shallow depression near the river and was subject to temperature inversions, residents were used to smog days in the spring and fall, but there had never been anything quite like this.
This smog was not only especially heavy and reluctant to move, but it smelled rank. Some residents asked the zinc factory to shut down, but the company refused.
By the third day, Friday, hundreds of people were sick. The second floor of the little hotel had become a hospital and the basement had become a morgue. By Saturday, 20 people had died.
On Sunday, it rained, and the smog was gone. But what had happened in Donora had made headlines. People started thinking about clean air, about ways to eliminate contaminants and how to regulate heavy industry.
The US Department of Public Health came in and studied Donora for nearly a year. They confirmed that an additional 50 people had died from the smog after it had lifted and that about half the population had suffered permanent health effects ranging from moderate to severe.
And the report pointed out that while it had gone unnoticed in the past, Donoran mortality rates had always doubled in months with smog days.
For years, residents of Donora had refused to talk about the Killer Smog of 1948 – best forgotten, apparently. But a few years ago, on the 60th anniversary of the smog, the town opened the Donora Smog Museum. People think maybe the smog event was a catalyst for the Clean Air Act, and certainly it became part of the growing body of evidence that contaminated air wasn’t good for living things.
For a long time, sulphur dioxide was thought to be the main cause of death for the residents, but scientists are reevaluating autopsy evidence – fluoride levels were as much as 20 times normal, making it likely that it was the fluoride gas from the zinc plant that was really lethal.