Radon and home risks by county
Radon in Iowa
Every county in Iowa is in EPA radon Zone 1 (high potential). Radon zones describe an area's potential; EPA recommends testing every home regardless of zone.
Zone 1 counties
99
high radon potential
Zone 2 counties
0
moderate potential
Zone 3 counties
0
low potential
Counties with water violations
55
since 2016; 3 with unresolved ones
Find your county by ZIP
Zone 1: high potential (99 counties)
| County | Residents | Water systems | Health violations since 2016 | Unresolved |
|---|---|---|---|---|
| Adair County | 7,431 | 7 | 0 | 0 |
| Adams County | 3,606 | 3 | 2 | 0 |
| Allamakee County | 14,184 | 4 | 1 | 0 |
| Appanoose County | 12,106 | 6 | 0 | 0 |
| Audubon County | 5,562 | 4 | 0 | 0 |
| Benton County | 25,799 | 17 | 8 | 0 |
| Black Hawk County | 132,348 | 11 | 0 | 0 |
| Boone County | 26,729 | 12 | 6 | 0 |
| Bremer County | 25,328 | 10 | 0 | 0 |
| Buchanan County | 20,733 | 10 | 1 | 0 |
| Buena Vista County | 20,816 | 12 | 0 | 0 |
| Butler County | 14,156 | 10 | 9 | 0 |
| Calhoun County | 9,711 | 12 | 8 | 0 |
| Carroll County | 20,407 | 13 | 15 | 0 |
| Cass County | 13,024 | 7 | 2 | 0 |
| Cedar County | 18,231 | 13 | 1 | 0 |
| Cerro Gordo County | 42,493 | 9 | 0 | 0 |
| Cherokee County | 11,658 | 11 | 0 | 0 |
| Chickasaw County | 11,719 | 6 | 0 | 0 |
| Clarke County | 9,524 | 4 | 5 | 0 |
| Clay County | 16,474 | 6 | 0 | 0 |
| Clayton County | 16,931 | 16 | 1 | 0 |
| Clinton County | 46,015 | 16 | 3 | 0 |
| Crawford County | 16,378 | 10 | 0 | 0 |
| Dallas County | 115,343 | 20 | 8 | 0 |
| Davis County | 9,193 | 3 | 0 | 0 |
| Decatur County | 7,656 | 6 | 8 | 0 |
| Delaware County | 17,609 | 8 | 1 | 0 |
| Des Moines County | 38,411 | 9 | 2 | 0 |
| Dickinson County | 18,158 | 10 | 2 | 0 |
| Dubuque County | 99,242 | 32 | 4 | 0 |
| Emmet County | 9,162 | 7 | 0 | 0 |
| Fayette County | 19,152 | 11 | 1 | 0 |
| Floyd County | 15,008 | 7 | 1 | 0 |
| Franklin County | 10,024 | 9 | 0 | 0 |
| Fremont County | 6,494 | 7 | 0 | 0 |
| Greene County | 8,662 | 5 | 0 | 0 |
| Grundy County | 12,405 | 9 | 0 | 0 |
| Guthrie County | 10,774 | 7 | 1 | 0 |
| Hamilton County | 14,856 | 9 | 0 | 0 |
| Hancock County | 10,616 | 8 | 1 | 0 |
| Hardin County | 16,464 | 12 | 0 | 0 |
| Harrison County | 14,626 | 11 | 1 | 0 |
| Henry County | 19,361 | 11 | 1 | 1 |
| Howard County | 9,360 | 6 | 0 | 0 |
| Humboldt County | 9,617 | 8 | 1 | 1 |
| Ida County | 6,810 | 5 | 0 | 0 |
| Iowa County | 16,423 | 11 | 10 | 0 |
| Jackson County | 19,390 | 10 | 5 | 0 |
| Jasper County | 38,107 | 11 | 0 | 0 |
| Jefferson County | 15,781 | 10 | 0 | 0 |
| Johnson County | 160,080 | 75 | 66 | 0 |
| Jones County | 21,116 | 13 | 2 | 0 |
| Keokuk County | 9,855 | 11 | 0 | 0 |
| Kossuth County | 14,408 | 15 | 1 | 0 |
| Lee County | 32,376 | 6 | 11 | 0 |
| Linn County | 231,762 | 40 | 1 | 0 |
| Louisa County | 10,630 | 8 | 0 | 0 |
| Lucas County | 8,758 | 3 | 19 | 0 |
| Lyon County | 12,378 | 12 | 0 | 0 |
| Madison County | 17,161 | 5 | 1 | 0 |
| Mahaska County | 22,034 | 4 | 1 | 0 |
| Marion County | 34,048 | 13 | 1 | 0 |
| Marshall County | 40,392 | 14 | 0 | 0 |
| Mills County | 14,717 | 7 | 6 | 0 |
| Mitchell County | 10,632 | 5 | 0 | 0 |
| Monona County | 8,429 | 8 | 0 | 0 |
| Monroe County | 7,373 | 3 | 0 | 0 |
| Montgomery County | 10,063 | 4 | 0 | 0 |
| Muscatine County | 42,132 | 22 | 2 | 0 |
| O'Brien County | 14,260 | 7 | 0 | 0 |
| Osceola County | 6,036 | 7 | 0 | 0 |
| Page County | 15,038 | 9 | 1 | 0 |
| Palo Alto County | 8,809 | 7 | 14 | 0 |
| Plymouth County | 25,825 | 10 | 0 | 0 |
| Pocahontas County | 7,006 | 9 | 5 | 0 |
| Polk County | 516,185 | 38 | 4 | 0 |
| Pottawattamie County | 93,529 | 16 | 1 | 0 |
| Poweshiek County | 18,454 | 8 | 16 | 1 |
| Ringgold County | 4,608 | 4 | 0 | 0 |
| Sac County | 9,533 | 8 | 7 | 0 |
| Scott County | 175,601 | 48 | 1 | 0 |
| Shelby County | 11,821 | 9 | 1 | 0 |
| Sioux County | 36,554 | 16 | 1 | 0 |
| Story County | 102,498 | 20 | 7 | 0 |
| Tama County | 16,738 | 11 | 0 | 0 |
| Taylor County | 5,825 | 4 | 2 | 0 |
| Union County | 11,955 | 2 | 2 | 0 |
| Van Buren County | 7,217 | 8 | 0 | 0 |
| Wapello County | 35,681 | 6 | 0 | 0 |
| Warren County | 56,343 | 14 | 0 | 0 |
| Washington County | 22,631 | 14 | 1 | 0 |
| Wayne County | 6,622 | 6 | 0 | 0 |
| Webster County | 36,909 | 24 | 4 | 0 |
| Winnebago County | 10,383 | 7 | 0 | 0 |
| Winneshiek County | 19,723 | 13 | 0 | 0 |
| Woodbury County | 107,257 | 17 | 6 | 0 |
| Worth County | 7,307 | 7 | 0 | 0 |
| Wright County | 12,729 | 7 | 0 | 0 |
How to read this table
Water systems counts community systems that list the county in their service area; one system can serve several counties. Health violations are breaches of a legal limit or treatment rule recorded by EPA since January 2016, not paperwork lapses. A violation stays unresolved until the state records it as fixed.
Other states
- Arizona
- California
- Colorado
- Florida
- Idaho
- Illinois
- Michigan
- Minnesota
- New Jersey
- New York
- Ohio
- Pennsylvania
- Texas
- Utah
Sources: EPA Map of Radon Zones, EPA ECHO Safe Drinking Water Act data (2026Q3, published October 2026), US Census Bureau Vintage 2024 estimates. See the methodology.