# Counties in Ohio by median Air Quality Index (US EPA), 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_median`
- Unit: index
- Definition: 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.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: median daily AQI (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Publisher page: https://invokely.ai/en/publishers/environmental-protection-agency
- Retrieved: 2026-10-12
- Citation: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/median-air-quality-index/ohio-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Cuyahoga County | 72 |
| 2 | Hamilton County | 68 |
| 3 | Butler County | 66 |
| 3 | Franklin County | 66 |
| 3 | Jefferson County | 66 |
| 6 | Montgomery County | 65 |
| 7 | Summit County | 64 |
| 8 | Lucas County | 63 |
| 9 | Mahoning County | 62 |
| 10 | Trumbull County | 61 |
| 11 | Lawrence County | 60 |
| 12 | Athens County | 54 |
| 12 | Clark County | 54 |
| 14 | Portage County | 52 |
| 15 | Clinton County | 49 |
| 15 | Preble County | 49 |
| 17 | Delaware County | 48 |
| 17 | Geauga County | 48 |
| 17 | Knox County | 48 |
| 17 | Madison County | 48 |
| 17 | Miami County | 48 |
| 22 | Clermont County | 47 |
| 22 | Stark County | 47 |
| 24 | Greene County | 46 |
| 25 | Ashtabula County | 45 |
| 25 | Licking County | 45 |
| 25 | Medina County | 45 |
| 25 | Warren County | 45 |
| 29 | Lorain County | 44 |
| 29 | Scioto County | 44 |
| 29 | Washington County | 44 |
| 29 | Wood County | 44 |
| 33 | Allen County | 43 |
| 34 | Noble County | 42 |
| 35 | Lake County | 41 |
| 36 | Crawford County | 38 |
| 36 | Fayette County | 38 |
| 38 | Columbiana County | 26 |
| 39 | Monroe County | 24 |
| 39 | Ottawa County | 24 |
| 41 | Hancock County | 23 |
| 42 | Belmont County | 21 |
| 42 | Sandusky County | 21 |
| 44 | Wyandot County | 20 |
| 45 | Seneca County | 18 |