AQI 52 · PM2.5 · Trend: Improving
| Average AQI | 52 |
| Good Days / Year | 200 |
| Unhealthy Days / Year | 12 |
| Primary Pollutant | PM2.5 |
| PM2.5 Average | 9.5 µg/m³ |
| Trend | ↓ Improving |
| Monitoring Stations | 55 |
| Nonattainment Areas | 2 |
Illinois air quality is dominated by the Chicago metro area, where vehicle traffic, industrial activity, and freight operations create moderate pollution. Downstate areas generally have good air quality with agricultural burning as the main seasonal concern.
Illinois EPA enforces air quality standards. Chicago metro vehicle emissions testing. Member of RGGI-adjacent consultation. Coal plant retirement accelerating.
Chicago-Naperville metro — ozone and PM2.5 nonattainment. Metro East (St. Louis area) — ozone nonattainment.