In October 1948, a thick haze rolled into Donora, Pennsylvania, a steel town in the Monongahela Valley, south of Pittsburgh. For five days, toxic fumes from a zinc smelter – a plant that turns zinc ore into pure zinc metal – poured out of the factory’s stacks, became trapped in the valley and thus blanketed Donora. The air was filled with sulfur oxides, heavy metal dust and airborne particulates.
Firefighters carried 60-pound oxygen tanks door to door to relieve elderly and asthmatic victims. Nurses attended to mill workers in the infirmary, laying patients on the floor as hospital beds filled to capacity. Funeral homes ran out of space. The disaster eventually claimed 20 lives and caused chronic lung disease in many more.
In 1948, 40 patients were hospitalized in Donora, Pa., due to a smoke and fog disaster that led to the death of 20 residents.
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This was one of the first clear demonstrations in the U.S. that air pollution could kill. Today, new global health research quantifying the risks of pollution exposure helps explain why disasters like Donora were so deadly, and why similar health threats persist.
As a public health researcher and a public health physician, we recently published a study in the journal Annals of Global Health on the health impacts of air pollution in southwestern Pennsylvania that shows the Pittsburgh area as a hot spot for pollution.
A turning point
Research triggered by the Donora disaster uncovered that air pollution causes serious health issues, including chronic heart disease, stroke, chronic obstructive pulmonary disease, lung cancer and diabetes in adults, and can lead to premature birth, low birth weight, stillbirth, asthma and impaired lung development in children.
Emerging evidence indicates that air pollution is also associated with dementia in adults and with IQ loss, attention-deficit/hyperactivity disorder and autism spectrum disorder in children.
Before the Donora disaster, the federal government did not regulate air quality. Pollution was legally viewed as a local nuisance – the unavoidable price of progress.
But the tragedy in Donora forced policymakers, scientists and the public to recognize that air pollution is a serious threat to health. Donora thus laid the groundwork for the Clean Air Act, the federal air pollution law initially enacted in 1963, then strengthened in 1970 and again in 1990. It also catalyzed the nation’s first air pollution research programs.
Pollution persists
Despite this progress, air pollution is still responsible for an estimated 200,000 deaths across the U.S. each year. These deaths are not evenly distributed. Instead, they are concentrated in pollution hot spots.
Because of its heavy industry and lack of local enforcement of the Clean Air Act, Pittsburgh is still one of the most polluted regions of the country.
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Our research shows southwestern Pennsylvania, the region around Donora and including Pittsburgh, is one of these hot spots.
Because of its steel mills, coke ovens – which burn coal to produce fuel for steel production – steep valleys that trap pollution and a history of inadequate local enforcement of the Clean Air Act, the Pittsburgh metropolitan area continues to rank among the nation’s most polluted regions.
Breaking down the new data
Fine particle air pollution, known as PM2.5, doesn’t just dirty the air in Pittsburgh and surrounding communities. It can kill people and harm children before they are even born.
To understand the full toll, we conducted an epidemiological study. Using NASA satellite images to measure pollution levels in each census tract, we linked that data to death and birth records from the Pennsylvania Department of Health.
The findings were stark. In 2019, between 3,085 and 3,467 deaths in southwestern Pennsylvania – roughly 11% to 12.5% of all adult deaths that year – were likely attributable to PM2.5 pollution. The damage extended to newborns as well: We estimated pollution caused 229 premature births, 177 infants with low birth weight and 12 stillbirths.
Using existing scientific data showing that every small increase in air pollution is linked to a measurable drop in children’s IQ, we applied that formula to Pittsburgh’s pollution levels across all 24,604 children born there in 2019. That calculation produced an estimated collective loss of more than 60,000 IQ points across the group. That’s an average of approximately 2.5 IQ points per child.
Fine particulate air pollution was responsible for the loss of 2.5 IQ points per child born in Pittsburgh in 2019.
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Importantly, many of the harms we saw in Pittsburgh occurred at PM2.5 levels below EPA’s air quality standard of 9 micrograms per cubic meter. This indicates that even low-level PM2.5 exposures carry significant risks to health.
Our findings arrive at a pivotal moment for U.S. air policy. EPA Administrator Lee Zeldin has announced his intention to raise the allowable limit for PM2.5, relax enforcement of the Clean Air Act and repeal the greenhouse gas endangerment finding, which allows the EPA to regulate the emissions that drive climate change.
The EPA has also eliminated its long-standing practice of counting the economic benefits of pollution control. According to new calculations, the EPA will count only the costs of pollution control while stripping out the economic value of lives saved – a metric known as the “value of a statistical life” that agencies have long used to justify health regulations.
What happens next?
During the first Trump administration, environmental rollbacks and a lack of pollution prevention efforts led to an estimated 20,000 deaths per year, according to the Environmental Protection Network, a nonprofit organization consisting of EPA alumni who volunteer their expertise to protect environmental integrity and public health. The deaths were clustered mostly in Southern and Midwestern states with heavy industry and lax pollution rules. States that had already put strong pollution controls in place were able to cushion the blow of the federal cutbacks.
Public health researchers point to local enforcement of the Clean Air Act as a way to limit health impacts of federal agency rollbacks. Allegheny County has legal authority under the Clean Air Act to set and enforce pollution standards stricter than federal minimums, but has not consistently used that authority.
Community and advocacy groups, including the Clean Air Council and PennEnvironment, have pushed the county health department to adopt stricter standards and increase permit enforcement. The Allegheny County Health Department holds regular public meetings where air quality rules and enforcement priorities are subject to review.
As the regulatory landscape shifts, the data from communities like southwestern Pennsylvania will be critical to understanding and documenting what is lost due to air pollution.