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Air quality in Iowa

EPA monitors report from 17 of Iowa’s 99 counties. That is the honest limit of this page: the other 82 are not measured, not clean. In 2025 the most affected monitored county was Palo Alto County, with 9 days above the moderate category.

17
Counties with monitors
82
Counties without
42
Days above moderate, 2025
Summed across monitored counties
9.9%
Adults with asthma
Population-weighted county estimate

County by county

Monitored Iowa counties

GoodModerateUnhealthy for sensitive groupsUnhealthyVery unhealthyHazardous
County90th %ile AQIAbove moderateMax AQI2025 days by category
Palo Alto County719134
Linn County685163
Johnson County614159
Webster County654165
Clinton County713166
Woodbury County613122
Black Hawk County632158
Harrison County642119
Muscatine County592141
Polk County642136
Scott County712159
Van Buren County612129
Bremer County541115
Montgomery County611133
Cerro Gordo County41056
Lee County64097
Pottawattamie County57087

EPA Air Quality System annual summaries by county, 2025. The 90th percentile AQI describes a day worse than nine out of ten, which is a steadier measure than the annual maximum a single wildfire can set.

Not measured

82 counties without a monitor

No EPA monitor reported from these counties, so there is no air quality record to publish. Their radon zone is known, and radon is measured in the building rather than the air outside it.

Other states

Air quality elsewhere