AirHistory — Air Quality Trends & Grades for 1,000+ US Cities

Skip to main content

Cleanest Air Worst Air Improving Compare Tools Guides Glossary Blog Trends

C

Saint Charles, Missouri, MO

Air Quality Grade: 63/100

Median AQI: 45. Trend: Stable.

View full report →

Data from AirHistory

AirHistory

10-year air quality trends for every US city. Data from EPA Air Quality System (AQS), updated annually.

Rankings

Cleanest Air Cities Worst Air Quality Cities Fastest-Improving Compare Cities

Pollutants

PM2.5 Trends Ozone Trends NO2 Trends CO Trends PM10 Trends

Browse

Grade A Cities Improving Cities Worsening Cities Good AQI Cities Tools Air Quality Report Card Exposure Estimator Air Quality Guides Glossary Air Quality Blog

About

Methodology 2026 Report Privacy Policy

Data sourced from EPA Air Quality System (AQS). Not affiliated with the US Environmental Protection Agency.