Share of days unhealthy for sensitive groups or worse (US EPA AQI)
Days with a daily Air Quality Index above 100 (unhealthy for sensitive groups, unhealthy, very unhealthy or hazardous) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; the counts are stored with each value.
Use the share rather than the number of days to compare counties, since the days with an AQI differ. 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 share of days unhealthy for sensitive groups or worse (US EPA AQI) of 1000 counties in 2019, at 36.4%, and York County the lowest, at 0%. Source: EPA.
- 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 share of days unhealthy for sensitive groups or worse (US EPA AQI), 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
- Jackson County
- Norfolk city
- Rockingham County
- Hillsborough County
- Davis County
- Lancaster 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 share of days unhealthy for sensitive groups or worse (US EPA AQI)? Use official data and cite it.
rank_places {"indicator":"aqi_unhealthy_sensitive_or_worse_days_share","level":"province","within":"United States"}
GET https://invokely.ai/api/v1/rank?indicator=aqi_unhealthy_sensitive_or_worse_days_share&level=province&within=United%20States