# Counties in Utah by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2025

All 17 values come from U.S. Environmental Protection Agency for 2025, so the places are comparable. 2 counties have no value for that period and are not ranked.

- Indicator id: `aqi_unhealthy_sensitive_or_worse_days_share`
- Unit: %
- Definition: 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.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Retrieved: 2026-10-12
- Citation: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: days with an AQI above 100 as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/unhealthy-air-quality-days-share/utah-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Salt Lake County | 4.4 |
| 2 | Davis County | 1.9 |
| 3 | Uintah County | 1.1 |
| 4 | Carbon County | 0.5 |
| 4 | Duchesne County | 0.5 |
| 4 | Weber County | 0.5 |
| 7 | Box Elder County | 0.3 |
| 7 | Iron County | 0.3 |
| 7 | San Juan County | 0.3 |
| 7 | Tooele County | 0.3 |
| 7 | Utah County | 0.3 |
| 7 | Wasatch County | 0.3 |
| 13 | Cache County | 0 |
| 13 | Garfield County | 0 |
| 13 | Grand County | 0 |
| 13 | Washington County | 0 |
| 13 | Wayne County | 0 |