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The Donora Smog

When I was on a toxicology elective as a resident, the fellow and I disagreed over the topic of the presentation I had to give. I wanted to cover a drug commonly prescribed to complex care patients, she wanted something “more interesting,” like an exotic compound that she would only see once in her career if she were lucky (and the patient very unlucky). We compromised on a historical topic of local relevance, the Donora Smog of 1948.

Donora, Pa., named for William Donner and Nora Mellon – lies in a bend of the Monongahela River on the eastern edge of Washington County, 25 miles south of Pittsburgh. It was incorporated in 1901 as a mill town dominated by two U.S. Steel factories, the Donora Zinc Works and the American Steel and Wire plant. A whole neighborhood of poured-in-place concrete houses for their workers was constructed according to Thomas Edison’s designs during World War I. By the 1940s, Donora’s 13,000 residents lived a smoky existence, much like Pittsburghers did. But nothing compared to the experience of five fateful days.

On Wednesday, Oct. 27, 1948, the autumn sun did not warm the cool, low-lying air enough to rise out of the Mon Valley. A layer of warmer air above that acted as a lid, trapping emissions from the factories, motor vehicles and coal-burning furnaces. Called a “thermal inversion,” this weather phenomenon continues to cause “winter smog,” as opposed to the “summer smog” created by the reaction of ultraviolet light with hydrocarbons generated in fossil fuel combustion. With a thick yellow haze blanketing everything, Donora’s eight doctors and two firefighters were soon busy, crisscrossing the town until the head of the local American Red Cross set up a centralized call center in the town hall.

Respiratory complaints were the most common, and patients were treated in oxygen tents. At least 20 died immediately, and another 50 succumbed over the next month. The harmful components of smog include primary pollutants such as carbon monoxide (CO), nitric oxide (NO), sulfur dioxide (SO2), volatile organic compounds (VOCs) and particulate matter. Secondary pollutants created by chemical reactions in the air include nitrogen dioxide (N2O), sulfur trioxide (SO3), ozone (O3), and the components of acid rain, nitric acid (HNO3) and sulfuric acid (H2SO4). In addition to irritating delicate mucous membranes, these compounds endanger living tissues via oxidative damage and/or inhibiting the electron transport chain. The Donora Smog is thought to have been particularly deadly because of the presence of fluorine gas from the zinc works.

Finally, on Sunday, Oct. 31, the factory owners agreed to suspend production until the air cleared. Thankfully, it also rained that day. The incident was reported in newspapers across the country, and you can find a contemporary British newsreel about it on YouTube (LINK). The Donora Smog is remembered today not because it was such an anomaly, but because it catalyzed the birth of the environmental movement. Concerned Mon Valley citizens founded the Society for Better Living, whose motto was “Fresh Air – Green Grass.” Such grassroots efforts gradually snowballed into calls for federal funding of air pollution research (1955) and for legislation to protect the health of humans and their ecosystems. Their crowning achievements are the Clean Air Act of 1963, the first Earth day (April 22, 1970) and the establishment of the Environmental Protection Agency (1970).

Today, the skies are clearer for Donora’s 4,500 inhabitants. It is known as “The Home of Champions,” having birthed baseball greats Stan “The Man” Musial and both Ken Griffey Sr. and Jr. Lest you think a straight path connected the Donora smog to the triumphs of environmentalism, consider its most famous daughter. Mary Ochsenhirt Amdur (1921-1998) earned a bachelor’s degree in chemistry from the University of Pittsburgh (1943) and a PhD in biochemistry at Cornell University (1946). While researching the effects of air pollution at the Harvard School of Public Health, Amdur and her husband devised a chamber for subjecting guinea pigs to sulfuric acid. Unsurprisingly, they found acute and chronic respiratory problems, as well as weight loss.

However, industry leaders felt so threatened by her results that they sent two thugs to threaten her in an elevator at a national conference, and they pressured her mentor to quash the related article. After Amdur was fired, Alice Hamilton wrote to her, “The trouble with this branch of medical science is that it is always tied up more or less with somebody’s pocketbook – Maybe the companies, maybe the insurance people, maybe the doctor in charge.” Amdur found other positions at Harvard, MIT, and finally NYU. Because of her continued work on inhalation chemistry, she is now known as the “Mother of Air Pollution Toxicology.” She was the first female recipient of the Merit Award of the Society of Toxicology (1997), and today the Society gives a student award in her honor.

A Donora Smog Museum opened in 2008. Visit for more information.

For more reading

  1. Devra Davis, When Smoke Ran Like Water (New York: Basic Books, 2002)

  2. Robert K. Musil, Rachel Carson and Her Sisters: Extraordinary Women Who Have Shaped America’s Environment (New Brunswick: Rutgers University Press, 2014)

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