# Counties in Iowa by highest daily Air Quality Index (US EPA), 2016

All 19 values come from U.S. Environmental Protection Agency for 2016, so the places are comparable. 7 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/iowa-counties

| Rank | Place | index |
|---:|---|---:|
| 1 | Van Buren County | 158 |
| 2 | Palo Alto County | 155 |
| 3 | Polk County | 138 |
| 4 | Montgomery County | 121 |
| 5 | Black Hawk County | 118 |
| 6 | Scott County | 112 |
| 7 | Clinton County | 108 |
| 8 | Linn County | 106 |
| 9 | Johnson County | 100 |
| 10 | Muscatine County | 96 |
| 11 | Harrison County | 84 |
| 12 | Delaware County | 81 |
| 13 | Bremer County | 80 |
| 14 | Story County | 77 |
| 15 | Lee County | 74 |
| 16 | Pottawattamie County | 71 |
| 16 | Warren County | 71 |
| 18 | Woodbury County | 66 |
| 19 | Cerro Gordo County | 59 |