# Counties in Ohio by share of days unhealthy for sensitive groups or worse (US EPA AQI), 2001

All 45 values come from U.S. Environmental Protection Agency for 2001, so the places are comparable. 13 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/ohio-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | Ashtabula County | 19.2 |
| 1 | Geauga County | 19.2 |
| 3 | Clinton County | 16.4 |
| 4 | Cuyahoga County | 16.2 |
| 5 | Lawrence County | 14.8 |
| 6 | Delaware County | 14.6 |
| 7 | Knox County | 14 |
| 8 | Hamilton County | 13.2 |
| 9 | Medina County | 13.1 |
| 10 | Summit County | 12.6 |
| 11 | Portage County | 12.5 |
| 11 | Trumbull County | 12.5 |
| 13 | Franklin County | 12.1 |
| 13 | Jefferson County | 12.1 |
| 13 | Madison County | 12.1 |
| 16 | Wood County | 11.7 |
| 17 | Butler County | 11.2 |
| 18 | Lucas County | 11 |
| 19 | Mahoning County | 10.9 |
| 20 | Warren County | 10.7 |
| 21 | Clermont County | 10.1 |
| 21 | Licking County | 10.1 |
| 23 | Lorain County | 9.3 |
| 23 | Montgomery County | 9.3 |
| 23 | Stark County | 9.3 |
| 26 | Crawford County | 9.1 |
| 27 | Clark County | 8.9 |
| 28 | Lake County | 8.8 |
| 28 | Noble County | 8.8 |
| 30 | Washington County | 8.7 |
| 31 | Greene County | 6.8 |
| 32 | Preble County | 5.9 |
| 33 | Miami County | 5.6 |
| 34 | Allen County | 5.2 |
| 34 | Scioto County | 5.2 |
| 36 | Fayette County | 5 |
| 37 | Athens County | 0.9 |
| 38 | Belmont County | 0 |
| 38 | Columbiana County | 0 |
| 38 | Hancock County | 0 |
| 38 | Monroe County | 0 |
| 38 | Ottawa County | 0 |
| 38 | Sandusky County | 0 |
| 38 | Seneca County | 0 |
| 38 | Wyandot County | 0 |