# Counties in Alaska by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2020

All 9 values come from U.S. Environmental Protection Agency for 2020, so the places are comparable. 4 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/alaska-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Fairbanks North Star Borough | 10.1 |
| 2 | Juneau City and Borough | 0.3 |
| 2 | Matanuska-Susitna Borough | 0.3 |
| 4 | Aleutians East Borough | 0 |
| 4 | Anchorage Municipality | 0 |
| 4 | Bethel Census Area | 0 |
| 4 | Denali Borough | 0 |
| 4 | Kenai Peninsula Borough | 0 |
| 4 | North Slope Borough | 0 |