# Counties in Missouri by highest daily Air Quality Index (US EPA), 2025

All 21 values come from U.S. Environmental Protection Agency for 2025, so the places are comparable. 13 counties have no value for that period and are not ranked.

- Indicator id: `aqi_max`
- Unit: index
- Definition: Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.
- Source: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: highest 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: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
- Web page: https://invokely.ai/rankings/highest-daily-air-quality-index/missouri-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | St. Louis city | 738 |
| 2 | Jackson County | 293 |
| 3 | Buchanan County | 256 |
| 4 | St. Charles County | 164 |
| 5 | Jasper County | 162 |
| 6 | Greene County | 160 |
| 7 | Clay County | 156 |
| 8 | St. Louis County | 151 |
| 9 | Jefferson County | 150 |
| 10 | Cass County | 123 |
| 11 | Clinton County | 122 |
| 11 | Lincoln County | 122 |
| 13 | Ste. Genevieve County | 108 |
| 14 | Cedar County | 106 |
| 15 | Perry County | 105 |
| 16 | Monroe County | 97 |
| 17 | Andrew County | 93 |
| 18 | Boone County | 87 |
| 19 | Taney County | 79 |
| 20 | Callaway County | 77 |
| 21 | Stoddard County | 43 |