Kids in 23 of Illinois' counties are breathing unhealthy air, according to a recent report evaluating ground-level smog and particulate pollution.
The American Lung Association said in its 2026 “State of the Air” report that nearly half of U.S. children — about 33.5 million — are breathing unhealthy levels of air pollution, with 152 million people overall living in areas that received failing grades for smog (ozone) or particle pollution.
The report, based on 2022–2024 data, evaluates counties for ground-level ozone (smog) and both short- and long-term particle pollution, ranking the cleanest and most polluted areas nationwide.
The Chicago-Naperville metro area is one of the most polluted areas in the country, coming in at number 15 on the American Lung Association's list for smog and 13 for particle pollution.
The St.Louis-St.Charles-Farmington metro area, which includes communities in Missouri and Illinois, also made the list as the 24th worst for high ozone days.
Throughout the state 23 out of 102 counties could be graded for at least one measure of air quality.
The worst five counties for high ozone days are:
The worst five counties for particle pollution are:
Illinoisans who want to know the quality of the air they’re breathing can use this tool that sorts data by county and ZIP code.
Researchers warned that despite decades of progress under the Clean Air Act, worsening wildfires, extreme heat, and recent federal rollbacks of environmental protections threaten air quality gains and could expose more people, especially children, to harmful pollution.
Children are particularly vulnerable because their lungs are still developing.
Exposure to unsafe air is linked to asthma, reduced lung growth, cognitive disorders, and an increased risk of disease later in life. Pollution has also been linked to heart attacks, strokes, premature death, and lung cancer.
The report also found disparities, with people of color more than twice as likely as white residents to live in communities with failing grades for all major pollution measures.
The top five metro areas for ozone pollution are:
The top five metro areas for short-term particulate matter are:
The top five metro areas for year-round particle pollution are.
By contrast, several smaller metro areas ranked among those with the cleanest air across all three categories, including Bangor, Maine, which made the list for all three measures.
In Illinois, only the Peoria-Canton metropolitan area made the cleanest list. While it ranked among the best for 24-hour particle pollution, it ranked 37th worst for high ozone days.
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