Man-made air pollution has decreased in recent years — but overall air pollution is worsening due in part to wildfires sweeping smog across the country, according to a new analysis.
The American Lung Association notes “a distressing reversal” of progress in its 2025 State of the Air report, released Wednesday.
“Years of successful cleanup of emissions from transportation, energy generation and industrial processes have contributed to falling ozone levels across much of the country since … 2000,” according to the report, which analyzed air quality data collected in 2023 from the Environmental Protection Agency.
“Unfortunately, as was shown in 2023, one bad fire season has the potential to offset that progress, at least temporarily, creating new challenges for air pollution control efforts and putting the health of the communities affected at increased risk.”
The Chicago area continues to rank among the worst in the nation for air pollution, according to the analysis. The metro area ranked 15th overall for levels of smog. That’s worse than the last two yearly reports, which Chicago ranked 17th.
California dominated this year’s list, with 9 of the 25 most polluted cities. Los Angeles ranked first for most polluted by ozone.
Smog, technically known as ozone air pollution, is caused by air pollutants that combine in sunlight. The pollution is produced by burning fossil fuels, including gasoline, diesel, coal and natural gas, that then chemically react in sunlight. The more sunlight, the more ozone pollution is produced.
The reports notes that climate change is behind the extreme weather events contributing to the higher levels of air pollution.
“Increases in high ozone days and spikes in particle pollution related to extreme heat, drought and wildfires are putting millions of people at risk and adding challenges to the work that states and cities are doing across the nation to clean up air pollution,” the report states.
The report “reinforces that we need to do more to curb air pollution,” Kristina Hamilton, Illinois advocacy director for the lung association, said in an interview.
Transportation is one of the main sources of pollution in the Chicago area, Hamilton said. Reducing those sources could improve the air quality for everyone, especially the low-income communities that are more likely to live next to industrial centers, she said.
“If we can address diesel pollution, truck and freight traffic — and emissions from those sources — that would be tremendously helpful to the air pollution problem in the Chicago area,” Hamilton said.
The American Lung Association is urging state lawmakers to pass vehicle standards to reduce tailpipe emissions, she said.
Chicago also ranked poorly by another measure of air quality: particle pollution. The metro area ranked 19th in the nation for annual average pollution by fine particles. That’s worse than Chicago’s 22nd position in last year’s report, and 24th the year prior.
Other takeaways from the report:
- The report found 46% of Americans, or 156 million people, live in places with failing grades for unhealthy levels of ozone or particle pollution. It’s 25 million more people than in last year’s report, and the most of any State of the Air report in the last decade.
- Illinois saw among the highest increase in ozone pollution between 2020-2022 and 2021-2023, the most recent years studied for ozone in the report
- Cook County got an “F” grade for high ozone days from 2021-2023, with 52 “orange” days and 6 “red” days of extremely bad pollution.
- The Peoria area ranked the 23rd cleanest cities in America for short-term particle pollution.