# Counties in Pennsylvania by median Air Quality Index (US EPA), 2025

All 38 values come from U.S. Environmental Protection Agency for 2025, so the places are comparable. 6 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/pennsylvania-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Allegheny County | 52 |
| 2 | Philadelphia County | 50 |
| 3 | Beaver County | 46 |
| 4 | Lancaster County | 45 |
| 4 | York County | 45 |
| 6 | Dauphin County | 44 |
| 6 | Delaware County | 44 |
| 6 | Washington County | 44 |
| 9 | Berks County | 43 |
| 9 | Chester County | 43 |
| 11 | Adams County | 42 |
| 11 | Lebanon County | 42 |
| 11 | Mercer County | 42 |
| 14 | Armstrong County | 41 |
| 14 | Cambria County | 41 |
| 14 | Centre County | 41 |
| 14 | Lehigh County | 41 |
| 14 | Montgomery County | 41 |
| 19 | Blair County | 40 |
| 19 | Fayette County | 40 |
| 19 | Greene County | 40 |
| 19 | Lycoming County | 40 |
| 23 | Indiana County | 39 |
| 23 | Lackawanna County | 39 |
| 23 | Tioga County | 39 |
| 23 | Westmoreland County | 39 |
| 27 | Northampton County | 38 |
| 28 | Bradford County | 37 |
| 28 | Franklin County | 37 |
| 30 | Bucks County | 36 |
| 30 | Elk County | 36 |
| 30 | Monroe County | 36 |
| 30 | Somerset County | 36 |
| 34 | Cumberland County | 35 |
| 34 | Warren County | 35 |
| 36 | Erie County | 34 |
| 37 | Wyoming County | 24 |
| 38 | Susquehanna County | 22 |