The wildfire smoke that blanketed Pittsburgh in July has cleared. But the health threat it exposed remains.
Smoke from Canadian wildfires pushed Allegheny County’s air quality into the maroon range July 16, meaning the pollution posed a hazard to everyone rather than only children, older adults and people with certain health conditions. County officials urged residents to limit their time outdoors.
For people with asthma and other respiratory conditions, the microscopic particles in wildfire smoke can trigger attacks, worsen breathing and lead to emergency care.
Climate scientists expect severe wildfire smoke to affect communities far from the fires with increasing frequency. In Pittsburgh, health and air quality experts warn that those episodes will arrive on top of a persistent local problem: industrial pollution that has contributed to elevated asthma rates and left some residents particularly susceptible to another surge of dangerous particles.
“Those are people who are already affected by day-to-day air pollution, and the wildfires are pollution on steroids,” said Angelo Taranto, a board member of Allegheny County Clean Air Now (ACCAN).
The combination raises two questions for a region that cannot prevent smoke from traveling: How can residents protect themselves when it arrives, and how much can local officials reduce the pollution already in Pittsburgh’s air?
A dangerous layer on top
Even before the wildfire smoke reached the region, many Allegheny County residents were breathing air that put their health at risk.
Asthma rates in Pittsburgh and Allegheny County are higher than the national average, with some of the greatest burdens in Mon Valley communities near major industrial facilities. According to Allegheny County Health Department data, the share of adults reporting asthma increased from 9% in 2017 to 16% in 2022.
One study found that children living near outdoor air pollution sites in the Pittsburgh region, including in the Mon Valley, had asthma at nearly three times the national rate. The rate was similar, however, to those reported in studies of underserved children in other U.S. cities.
Taranto said ACCAN hears from residents whose respiratory problems became noticeably worse after moving to the Pittsburgh area.
“Some of the cases that stand out are people who have moved here from out of town and, for the first time, experienced this air pollution,” he said. People who already used inhalers, he added, sometimes found themselves relying on them much more frequently than they had elsewhere.
The Clairton Coke Works, operated by U.S. Steel, is the region’s largest source of industrial air pollution.
“While air quality in Southwestern Pennsylvania is influenced by many sources and conditions across the region, U.S. Steel remains focused on the areas within our control,” said a spokesperson for U.S. Steel in a statement to Public Source. “In addition, our Mon Valley Works facilities maintain a more than 99% compliance rate.”
“The wildfires are pollution on steroids.”
Angelo taranto, Allegheny County Clean Air now
Dr. Sally Wenzel, a University of Pittsburgh department chair and director of UPMC’s Asthma Environmental Lung Health Institute, said extreme air quality events, such as those caused by wildfires, exacerbate respiratory disease symptoms.
Additionally, she said cardiovascular events like heart attacks become more common under pollution stress.
“All of those things can be worsened by exposure to high levels of pollution, enough to send you to the doctor’s office or the emergency room,” Wenzel said.
Wildfire smoke contains fine particulate matter that can penetrate deep into the lungs and enter the bloodstream. For people whose respiratory systems are already strained, a sudden increase can trigger asthma attacks and other serious problems.
“The size of the particles is important, the intensity of the exposure is important and the duration of the exposure is really critical,” Wenzel said.
Asthma-related emergency room visits in the United States were 17% higher than the average during the wildfire smoke episodes of summer 2023, according to data published by the Centers for Disease Control and Prevention.
Albert Presto, a Carnegie Mellon University professor who studies air quality, said Pittsburgh has experienced three major wildfire-smoke events since 2021, with increasingly severe effects.
“As the climate warms, the chances for wildfires go up. The chances for those wildfires to be large go up,” Presto said. “You would expect that, in a warming world, you would get more of these fires.”
Aarushi Pant, executive director of ACCAN, said those events compound an unequal health burden already carried by communities near industrial facilities.
“The burden is often put on local communities, communities of color, while they are already facing these issues,” Pant said. “Wildfire smoke just builds on top of each other.”
Temperature inversions, in which warm air traps pollution close to the ground, occur nearly one out of every three days in Allegheny County, according to Ana Hoffman, CREATE Lab air quality program director. Wildfire smoke is less frequent, but it can turn that persistent pollution burden into an acute health threat.
“The wildfire smoke definitely adds stress on top of the already moderate air quality that Pittsburgh has,” Pant said.
Protection is not equally available
The most effective way to reduce the risk from wildfire smoke is also the simplest: Avoid breathing it.
County officials and air quality experts advise residents to stay indoors, close windows and doors, and filter the air inside their homes. Anyone who must work or spend time outside should wear a well-fitting N95 mask.
But it isn’t just outdoor workers who may find those recommendations challenging.
People without central air conditioning may have to choose between opening their windows and enduring dangerous indoor heat, particularly when wildfire smoke coincides with a heat wave. Air purifiers and upgraded HVAC filters also carry costs that some households cannot easily absorb.
Presto said even relatively modest filtration improvements can make a meaningful difference.
“Paying for the more expensive filter for your air conditioner or your furnace actually makes a difference,” he said.
Whole-home filtration systems are among the most expensive options. Standalone air purifiers can clean the air in a single room, while a lower-cost alternative can be built by attaching a high-efficiency filter to a box fan.
“That’s simply a box fan, a very good air filter taped to a box fan. It’s called a MERV 13 filter,” Taranto said. “Putting that together is probably less than $100.”
People with asthma and other respiratory conditions should be especially cautious during hazardous-air days, Pant said. In addition to limiting outdoor exposure and wearing an N95, they said wearing goggles adds another layer of protection.
Reducing the pollution Pittsburgh can control
Allegheny County cannot stop smoke from Canadian wildfires from entering the region. It can, however, regulate the local pollution that mixes with it.
The county health department monitors air quality, enforces local air pollution regulations and can penalize facilities that violate emissions limits.
Clairton Coke Works, which is owned by US Steel, has faced numerous multimillion dollar fines for excessive emissions.
In 2021, Allegheny County adopted the Mon Valley Air Pollution Episode Rule. It requires certain industrial facilities to reduce emissions when weather conditions are expected to trap pollution in the Mon Valley. During the July wildfires, U.S. Steel said that it complied with the rule, which requires it to curb activity to decrease pollution.
“While that rule cannot prevent pollution from wildfire smoke traveling hundreds or thousands of miles, it helps reduce local emissions during periods when air quality is already poor,” the Allegheny County Health Department wrote in a statement.
Cilia Catello is an editorial intern at Pittsburgh’s Public Source. She can be reached at cilia@publicsource.org.
Clarification (8/10/2026): This story was updated with clarifying information about the region’s asthma rates and the findings of a study on local child asthma cases.
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