SmogRank / World / United States / Illinois / 2025
Most polluted cities in Illinois, United States, 2025
30 cities in Illinois, United States ranked by their average PM2.5 over the 365 days; 30 above the WHO annual guideline (5.0 µg/m³). Worst: Elmwood Park at 13.6 µg/m³, #486 of 2,624 cities in the world. Cleanest: Jerseyville at 6.7. A city needs measurements on 70% of the days to be ranked.
About 22.3K people in this city breathed unhealthy air on an average day of 2025.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
- 1Chicago 22.3K
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
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SmogRank, most polluted cities in Illinois, United States, PM2.5, 2025, smogrank.com/us/region/illinois/history/2025 (accessed 6 Oct 2026).
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.