# Counties in Indiana by median Air Quality Index (US EPA), 2015

All 39 values come from U.S. Environmental Protection Agency for 2015, so the places are comparable. 14 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/indiana-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Howard County | 58 |
| 2 | Marion County | 56 |
| 3 | Montgomery County | 55 |
| 4 | Lake County | 54 |
| 5 | St. Joseph County | 53 |
| 5 | Vanderburgh County | 53 |
| 7 | Clark County | 52 |
| 7 | Floyd County | 52 |
| 7 | Vigo County | 52 |
| 10 | Allen County | 51 |
| 10 | Bartholomew County | 51 |
| 10 | Elkhart County | 51 |
| 10 | Tippecanoe County | 51 |
| 10 | Whitley County | 51 |
| 15 | Dubois County | 47 |
| 15 | Porter County | 47 |
| 17 | Madison County | 45 |
| 17 | Spencer County | 45 |
| 19 | Greene County | 44 |
| 19 | Hamilton County | 44 |
| 21 | Carroll County | 43 |
| 21 | Perry County | 43 |
| 23 | Boone County | 42 |
| 23 | LaPorte County | 42 |
| 23 | Warrick County | 42 |
| 26 | Jackson County | 41 |
| 26 | Monroe County | 41 |
| 28 | Posey County | 40 |
| 29 | Johnson County | 39 |
| 29 | Morgan County | 39 |
| 29 | Shelby County | 39 |
| 32 | Brown County | 38 |
| 32 | Delaware County | 38 |
| 32 | Henry County | 38 |
| 35 | Hendricks County | 35 |
| 35 | Wabash County | 35 |
| 37 | Hancock County | 34 |
| 37 | Knox County | 34 |
| 39 | Huntington County | 31 |