Research from the University of Iowa shows a 20% increase in the number of large wildfires in the United States last year is damaging air quality in Iowa and other Midwestern states.
The data suggest fires have reversed progress the region had made in reducing emissions from other sources. Nearly 79,000 wildfires scorched more than 5 million acres in 2025, up sharply from the previous year.
Jun Wang, a biochemical engineering professor at the University of Iowa, said emissions from vehicles and power plants had been reduced, improving air quality in the region. But he said the increase in wildfires is pushing that trend in the opposite direction.
“Because of increase of fire emissions in the upwind regions, California, Northwestern U.S., Canada, our air quality in the Midwest regions is worsened,” Wang said.
An online map shows a large area of higher ozone levels and dirty air concentrated in the Midwest and Plains states. The data show air quality in the region had been improving since 2003 but began worsening with the increase in wildfires.
Wang said advanced technology has helped scientists better study the effects of wildfires on air quality. The tools produce more timely information about when fires start and where they’re active.
“One of the strategy is to improve the monitoring and prediction capabilities,” Wang said. “Once fires occur, we can use satellite to monitor them.”
The U.S. Environmental Protection Agency sets the national standard for ozone levels, but addressing air quality is largely up to state and local governments.