The 1948 Donora Smog and the birth of air quality regulations

Sixty-seven years ago today, residents of Donora, a town of around 14,000 lying along Monongahela River some 24 miles downstream of Pittsburgh, woke up to find a dense, yellow smog had blanketed the town. Donorans were accustomed to such smogs, as the town lay in a river valley ringed by hills that could reach up to 400 feet high. During the “smog season,” pollution from the industrial base of the city – including a steel mill and a zinc works – would collect in this natural depression and develop into smog until changes in meteorological conditions (shifting winds, rainfall) would dissolve the cloud.

But that didn’t happen on October 27. Or October 28, 29, or 30. Instead, a strong atmospheric inversion, which occurs when a blanket of lighter, warmer air flows in over heavier, colder air, sealed the smog in place. As this happened, emissions from the town’s factories, which included sulfuric acid, nitrogen dioxide, and flourine gas, continued to accumulate near the surface, instead of dissipating into the atmosphere. As the days passed, this blanket of toxic smog engulfing the town continued to get thicker and more noxious.

Given the prevailing views of the day, which suggested that air pollution was just a necessary byproduct of industrial progress, Donorans continued to go on with their lives. The high school football team played its home game that Friday; the Donora and Monongahela teams simply adjusted their tactics, with neither team throwing the ball. And the town even carried on with its Halloween festivities as planned. Workers at the steel and zinc mills continued to show up to work, despite the fact that they were producing the toxic emissions enveloping the town. The owners of the zinc works and steel mill rejected initial requests to shut down the factory as the days went by, and only agreed to cut back production on Halloween. This step occurred just as a storm blew into the area, helping to break the inversion and clear the air of the pollution.

All told, at least 20 people died during the smog, and, in the coming months, 50 more people died in the town than would have been expected under normal circumstances. But almost no one escaped the legacy of the smog, even those who did not succumb to its immediate impacts. The official epidemiological study conducted in the aftermath of the event concluded that “15.5 per cent of the total populace in the area were mildly affected; 16.8 per cent, moderately affected; and 10.4 per cent, severely affected.” The town’s overall mortality rate remained elevated for a decade or more. Relatively little changed for Donora or the country in the short-term. The town’s steel and zinc plants largely avoided being held liable, as investigators placed the blame on the extreme meteorological conditions that occurred. Whereas residents sued the steel plant for more than $4.5 million, U.S. Steel eventually settled for just $256,000, less than 6% of the damages sought.

To this day, the Donora smog remains less well-known than the Great London Smog of 1952, which, given that it affected a major metropolis, killed far more people (perhaps 12,000) and garnered considerably more attention. But Donora did lay the groundwork for air quality regulations in the United States. According to the Pittsburgh Gazette, Allegheny County regulated pollution for the first time the following year, and the passage of the 1955 U.S. Air Pollution Control Act, “the first federal legislation to recognize pollution as a problem,” can be linked to Donora (UPDATE: Per Ben Ross, author of The Polluters: The Making of Our Chemically Altered EnvironmentO, the 1955 Air Pollution Control Act was not the first federal bill to address air pollution. That can be traced back to the 1910 Organic Act, which created the Bureau of Mines. In fact, he noted, the 1955 act was a step backwards from the 1910 law in certain regards). The town’s museum commemorating the smog bears a sign proclaiming that “Clean Air Started Here,” while the town’s historical marker notes that “major federal clean air laws became a legacy of this environmental disaster.” Just as we think of the Cuyahoga River fire of 1969 as the impetus for the 1972 Clean Water Act (a story which is largely a fable), we should turn to Donora as we commemorate the 45th anniversary of the 1970 Clean Air Act Amendments that helped to end the legacy of these toxic smogs.

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  • Ben Ross

    It’s not historically accurate to say that the 1955 Air Pollution Control Act was the first federal legislation to recognize air pollution as a problem. That goes back at least to the Bureau of Mines organic act of 1910. The 1955 law was actually a step backwards in pollution control, shutting down the Bureau of Mines’ air pollution activities and transferring it to a division of the Public Health Service which was a foe of pollution control.

    This story is told briefly in this blog post and in more detail in my book The Polluters.

    • Tim

      Thanks for reading the post and for the comment. I have updated the post to reflect your information.

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