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Radon zones in Iowa

The EPA assigns every county in Iowa to one of three radon potential zones. Every one of its 99 counties is in Zone 1, the highest category, where the predicted average indoor screening level is above the EPA action level of 4 pCi/L.

99
Counties
99
Zone 1 counties
Predicted average above 4 pCi/L
0
Zone 2 counties
Predicted average 2-4 pCi/L
0
Zone 3 counties
Predicted average below 2 pCi/L

The map

Radon potential across Iowa

Every county in Iowa, filled by the zone the EPA assigns it. Zones follow geology rather than county lines, so the colour usually changes where the bedrock does, not where the border is.

Zone 1 · 99Zone 2 · 0Zone 3 · 0

Hover a county · click to open it

County by county

All 99 Iowa counties

Zone 1 · > 4 pCi/LZone 2 · 2 - 4 pCi/LZone 3 · < 2 pCi/L
CountyZonePopulationCOPDSmokingLung ca. deaths
Adair County17,3898.7%16.7%27.0
Adams County13,5448.4%15.6% -
Allamakee County114k8.6%16.2%32.7
Appanoose County112k10.8%19.6%37.7
Audubon County15,5349.0%16.3%32.9
Benton County126k7.1%14.9%30.7
Black Hawk County1130k7.0%15.6%38.6
Boone County127k6.8%14.3%46.3
Bremer County125k6.3%13.2%19.3
Buchanan County121k7.0%15.3%36.7
Buena Vista County121k7.2%15.6%23.2
Butler County114k8.3%15.7%34.8
Calhoun County19,7638.0%15.6%34.2
Carroll County121k7.7%15.2%28.6
Cass County113k9.2%17.5%32.5
Cedar County118k7.4%15.2%31.3
Cerro Gordo County142k8.0%15.5%29.1
Cherokee County112k9.0%16.4%33.7
Chickasaw County112k8.0%15.5%35.8
Clarke County19,5889.4%18.8%52.2
Clay County117k7.8%15.3%24.1
Clayton County117k9.7%17.8%27.8
Clinton County146k8.5%16.9%44.9
Crawford County116k8.4%16.7%22.1
Dallas County1111k4.5%10.9%24.5
Davis County19,1698.5%17.5%34.9
Decatur County17,6658.5%15.9%36.5
Delaware County118k8.3%16.3%28.7
Des Moines County138k7.9%15.9%43.6
Dickinson County118k7.5%13.1%26.6
Dubuque County199k6.8%13.6%28.9
Emmet County19,2298.4%16.2%35.2
Fayette County119k8.6%16.9%36.0
Floyd County115k8.3%16.2%39.9
Franklin County19,8759.0%17.0%27.9
Fremont County16,4588.1%15.2%62.6
Greene County18,5848.6%16.5%42.2
Grundy County112k6.8%13.9%31.2
Guthrie County111k7.6%14.6%35.2
Hamilton County115k7.3%14.7%30.2
Hancock County111k8.1%15.5%30.5
Hardin County116k8.3%16.2%30.4
Harrison County115k7.8%15.8%36.3
Henry County120k7.8%16.1%48.7
Howard County19,3768.3%16.6%34.3
Humboldt County19,5008.7%16.8%28.6
Ida County16,8338.2%16.0%43.2
Iowa County116k7.3%14.8%31.7
Jackson County119k8.4%16.3%40.1
Jasper County138k7.6%16.5%36.0
Jefferson County115k8.1%14.0%24.8
Johnson County1158k5.0%10.9%21.2
Jones County121k7.7%16.0%38.9
Keokuk County19,9148.9%17.6%30.1
Kossuth County114k8.2%14.9%25.5
Lee County133k8.6%17.5%34.5
Linn County1229k6.5%13.5%34.7
Louisa County111k7.7%15.7%49.2
Lucas County18,7479.6%18.4%41.2
Lyon County112k7.3%16.0%24.4
Madison County117k6.4%14.2%33.4
Mahaska County122k7.8%16.3%41.4
Marion County134k6.4%13.3%33.5
Marshall County140k7.2%15.2%34.9
Mills County115k6.7%13.8%29.8
Mitchell County111k7.9%15.3%20.1
Monona County18,4938.8%16.3%41.7
Monroe County17,5047.5%15.5% -
Montgomery County110k8.6%16.5%28.2
Muscatine County142k7.4%15.9%28.0
O'Brien County114k8.4%16.4%34.1
Osceola County15,9789.3%17.1%38.5
Page County115k9.1%18.0%50.1
Palo Alto County18,8107.8%15.1%61.1
Plymouth County126k6.8%14.5%32.3
Pocahontas County16,9768.6%15.9%41.9
Polk County1505k5.8%13.3%38.1
Pottawattamie County193k7.8%17.0%44.8
Poweshiek County118k7.5%14.7%36.0
Ringgold County14,6427.7%14.8% -
Sac County19,6868.1%15.1%27.8
Scott County1174k6.7%14.0%36.1
Shelby County112k7.9%15.2%26.3
Sioux County136k6.0%12.9%17.7
Story County199k4.8%11.1%26.6
Tama County117k8.8%17.4%30.6
Taylor County15,9248.3%16.3% -
Union County112k7.9%15.8%47.1
Van Buren County17,2669.8%18.5%56.6
Wapello County135k8.6%18.0%48.2
Warren County155k5.7%12.6%29.5
Washington County123k7.6%15.1%32.1
Wayne County16,5579.1%17.2%37.0
Webster County136k7.7%16.0%36.6
Winnebago County111k7.4%14.3%30.0
Winneshiek County120k6.6%12.4%24.2
Woodbury County1106k7.3%16.1%40.4
Worth County17,2977.8%15.5%26.8
Wright County113k8.7%16.0%26.3

Zones from the EPA Map of Radon Zones. COPD and smoking are CDC PLACES model-based estimates of adult prevalence. Lung cancer death rates are age-adjusted deaths per 100,000 per year, 2019-2023, from NCI State Cancer Profiles. A dash means the source does not report a value for that county.

Other states

Radon zones elsewhere