Iowa Radon Levels
99Zone 1 (High)
0Zone 2 (Moderate)
0Zone 3 (Low)
100% of counties in Iowa are classified as EPA Zone 1 (highest radon potential), meaning predicted average indoor radon levels exceed 4 pCi/L — the EPA action level. The EPA recommends that all homes be tested for radon, regardless of zone classification.
| County | EPA Zone | Risk Level |
|---|---|---|
| Adair County | Zone 1 | Highest Potential |
| Adams County | Zone 1 | Highest Potential |
| Allamakee County | Zone 1 | Highest Potential |
| Appanoose County | Zone 1 | Highest Potential |
| Audubon County | Zone 1 | Highest Potential |
| Benton County | Zone 1 | Highest Potential |
| Black Hawk County | Zone 1 | Highest Potential |
| Boone County | Zone 1 | Highest Potential |
| Bremer County | Zone 1 | Highest Potential |
| Buchanan County | Zone 1 | Highest Potential |
| Buena Vista County | Zone 1 | Highest Potential |
| Butler County | Zone 1 | Highest Potential |
| Calhoun County | Zone 1 | Highest Potential |
| Carroll County | Zone 1 | Highest Potential |
| Cass County | Zone 1 | Highest Potential |
| Cedar County | Zone 1 | Highest Potential |
| Cerro Gordo County | Zone 1 | Highest Potential |
| Cherokee County | Zone 1 | Highest Potential |
| Chickasaw County | Zone 1 | Highest Potential |
| Clarke County | Zone 1 | Highest Potential |
| Clay County | Zone 1 | Highest Potential |
| Clayton County | Zone 1 | Highest Potential |
| Clinton County | Zone 1 | Highest Potential |
| Crawford County | Zone 1 | Highest Potential |
| Dallas County | Zone 1 | Highest Potential |
| Davis County | Zone 1 | Highest Potential |
| Decatur County | Zone 1 | Highest Potential |
| Delaware County | Zone 1 | Highest Potential |
| Des Moines County | Zone 1 | Highest Potential |
| Dickinson County | Zone 1 | Highest Potential |
| Dubuque County | Zone 1 | Highest Potential |
| Emmet County | Zone 1 | Highest Potential |
| Fayette County | Zone 1 | Highest Potential |
| Floyd County | Zone 1 | Highest Potential |
| Franklin County | Zone 1 | Highest Potential |
| Fremont County | Zone 1 | Highest Potential |
| Greene County | Zone 1 | Highest Potential |
| Grundy County | Zone 1 | Highest Potential |
| Guthrie County | Zone 1 | Highest Potential |
| Hamilton County | Zone 1 | Highest Potential |
| Hancock County | Zone 1 | Highest Potential |
| Hardin County | Zone 1 | Highest Potential |
| Harrison County | Zone 1 | Highest Potential |
| Henry County | Zone 1 | Highest Potential |
| Howard County | Zone 1 | Highest Potential |
| Humboldt County | Zone 1 | Highest Potential |
| Ida County | Zone 1 | Highest Potential |
| Iowa County | Zone 1 | Highest Potential |
| Jackson County | Zone 1 | Highest Potential |
| Jasper County | Zone 1 | Highest Potential |
| Jefferson County | Zone 1 | Highest Potential |
| Johnson County | Zone 1 | Highest Potential |
| Jones County | Zone 1 | Highest Potential |
| Keokuk County | Zone 1 | Highest Potential |
| Kossuth County | Zone 1 | Highest Potential |
| Lee County | Zone 1 | Highest Potential |
| Linn County | Zone 1 | Highest Potential |
| Louisa County | Zone 1 | Highest Potential |
| Lucas County | Zone 1 | Highest Potential |
| Lyon County | Zone 1 | Highest Potential |
| Madison County | Zone 1 | Highest Potential |
| Mahaska County | Zone 1 | Highest Potential |
| Marion County | Zone 1 | Highest Potential |
| Marshall County | Zone 1 | Highest Potential |
| Mills County | Zone 1 | Highest Potential |
| Mitchell County | Zone 1 | Highest Potential |
| Monona County | Zone 1 | Highest Potential |
| Monroe County | Zone 1 | Highest Potential |
| Montgomery County | Zone 1 | Highest Potential |
| Muscatine County | Zone 1 | Highest Potential |
| O'Brien County | Zone 1 | Highest Potential |
| Osceola County | Zone 1 | Highest Potential |
| Page County | Zone 1 | Highest Potential |
| Palo Alto County | Zone 1 | Highest Potential |
| Plymouth County | Zone 1 | Highest Potential |
| Pocahontas County | Zone 1 | Highest Potential |
| Polk County | Zone 1 | Highest Potential |
| Pottawattamie County | Zone 1 | Highest Potential |
| Poweshiek County | Zone 1 | Highest Potential |
| Ringgold County | Zone 1 | Highest Potential |
| Sac County | Zone 1 | Highest Potential |
| Scott County | Zone 1 | Highest Potential |
| Shelby County | Zone 1 | Highest Potential |
| Sioux County | Zone 1 | Highest Potential |
| Story County | Zone 1 | Highest Potential |
| Tama County | Zone 1 | Highest Potential |
| Taylor County | Zone 1 | Highest Potential |
| Union County | Zone 1 | Highest Potential |
| Van Buren County | Zone 1 | Highest Potential |
| Wapello County | Zone 1 | Highest Potential |
| Warren County | Zone 1 | Highest Potential |
| Washington County | Zone 1 | Highest Potential |
| Wayne County | Zone 1 | Highest Potential |
| Webster County | Zone 1 | Highest Potential |
| Winnebago County | Zone 1 | Highest Potential |
| Winneshiek County | Zone 1 | Highest Potential |
| Woodbury County | Zone 1 | Highest Potential |
| Worth County | Zone 1 | Highest Potential |
| Wright County | Zone 1 | Highest Potential |