Median Air Quality Index (US EPA)
Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries. The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide). Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.
United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.
Key facts
- San Bernardino County had the highest median Air Quality Index (US EPA) of 1000 counties in 2019, at 81, and Harrison County the lowest, at 2. Source: the U.S. Environmental Protection Agency.
- Published for 1,498 places, with figures from 1980 to 2025.
Rankings
- US counties
- Counties in Texas
- Counties in North Carolina
- Counties in Virginia
- Counties in California
- Counties in Ohio
- Counties in Kentucky
- Counties in Indiana
- Counties in Michigan
- Counties in Wisconsin
- Counties in Oklahoma
- Counties in Pennsylvania
US counties by median Air Quality Index (US EPA), 2019
Places with data
Provinces and counties
- Los Angeles County
- Cook County
- Harris County
- Maricopa County
- San Diego County
- Orange County
- Miami-Dade County
- Dallas County
- Kings County
- Riverside County
- Frederick County
- Lubbock County
- Howard County
- Smith County
- Knox County
- Harford County
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
Which places have the highest median Air Quality Index (US EPA)? Use official data and cite it.
rank_places {"indicator":"aqi_median","level":"province","within":"United States"}
GET https://invokely.ai/api/v1/rank?indicator=aqi_median&level=province&within=United%20States