(Iowa Capital Dispatch) Wildfires have reversed years of progress toward mitigating ozone pollution, worsening air quality and causing premature deaths, University of Iowa researchers have found.
Eleven “uncontained large” wildfires were burning simultaneously across the United States as of June 12, according to the National Interagency Fire Center. Halfway through 2026, more than 32,000 wildfires have swept across more than 2.5 million acres, beating 10-year averages by thousands of fires and acreage.
The closest blaze to Iowa is located in the Nebraska National Forest, measured at just under 40,000 acres and currently 80% contained. While many Iowans would need a workday’s drive to reach the fire, researchers from the University of Iowa have found that invisible gases from wildfire debris worsen ozone pollution over the Midwest and other areas.
These wildfires have been increasing in frequency and intensity, in turn increasing the pollution that has reversed previous environmental gains and shortened people’s lifespans.
Jun Wang, a University of Iowa professor of chemical and biochemical engineering, Ph.D. student Weizhi Deng and their research team produced a recently published report stating ozone reductions made between 2003 and 2015 were reversed in the following nine years due to wildfire emissions, leading to 318 more premature deaths per year. According to the study, the emissions offset ozone pollution mitigation progress by four years.
“I’m particularly interested in the air pollution that wildfires generate,” Deng said. “Although wildfires can burn houses and kill people, I think the bigger impact is actually the smoke and air pollution generated by the wildfires that can transport and infest.”
Unlike the smoke and ash from wildfires that can easily be spotted, even as a haze in Iowa skies if the wind is right, Deng said the team’s work focused on ozone. This gas pollutant cannot be seen but can cause lung irritation and respiratory disease.
Wang described wildfire emissions as “a wild card,” with many different chemical compounds. Surface-level ozone, or smog, is created when sunlight interacts with carbon monoxide and other pollutants released by organic matter not fully burned away. The gas can also develop far away from fires when in contact with different emissions.
“The ozone pollution in the Midwest is getting worse, which is something that we did not expect at first, because it is just not a wildfire source region, but rather a downwind transport region,” Deng said.
Using information from Environmental Protection Agency surface ozone monitoring stations, satellite observations and weather and air quality monitoring data, Deng said the team trained a machine learning model to estimate surface ozone levels across the U.S. The datasets, spanning from 2003 to 2024, drill down to one-kilometer areas to show ozone distribution.
Researchers ran the air pollution model with and without data on wildfire smoke, Deng said, and the differences showed the smog’s impact on air quality over two decades.
The EPA operates more than 1,000 monitoring stations for surface ozone pollution, Deng said, but they don’t cover everywhere and are concentrated in urban areas. Monitoring sites in Iowa are clustered around Iowa City and Des Moines, Wang said, leaving out rural areas that also see smog come through from fires.
In order to calculate premature deaths from wildfire smog, Wang said the team factored in average lifespan and population density with ozone pollution exposure.
“Ozone shortens the lifespan for everybody,” Wang said. “If everybody’s lifespan is shortened by a month, then you can change the equivalent to how many lives lost we’re talking about.”
Deng recalled instances in the summers of 2023 and 2025 seeing wildfire smoke in Iowa from fires raging in Canada and the Rocky Mountains. He also saw friends who weren’t wearing masks or taking other steps to protect themselves from the dangerous air.
The key to lowering ozone pollution is to reduce the size and frequency of wildfires, Deng said, an effort that can be tackled through fewer agricultural burns and natural wildfire suppression, more prescribed burns, reduced fossil fuel burning and better monitoring.
Providing forecasts of air quality to decision-makers is also an important tool in keeping people safe, said study co-author Meng Zhou, a UI alum and assistant research scientist at NASA Goddard Space Flight Center. This study was launched from NASA-funded work in the Fire and Air Quality Project, in which Wang, Zhou and others provide information during wildfire season like forecasting.
“If we can have this forecast capability developed, this will provide more valuable information to the general public on the ozone exposures, and to help them to avoid some health issues,” Zhou said.
