Radon levels in Iowa

Verified county-level radon indicators are available for 99 Iowa counties. Select a county for its source period and sample details.

High results are most common in Sioux County (84%) and least common in Decatur County (26%)Share of tests at or above 4 pCi/L by county · Iowa radon test results from laboratories, 2008–2017 · 99 of 99 counties have data
Adair County: 72% of tests at or above 4 pCi/L · 98 testsAdams County: 65% of tests at or above 4 pCi/L · 81 testsAllamakee County: 73% of tests at or above 4 pCi/L · 492 testsAppanoose County: 45% of tests at or above 4 pCi/L · 117 testsAudubon County: 78% of tests at or above 4 pCi/L · 189 testsBenton County: 62% of tests at or above 4 pCi/L · 696 testsBlack Hawk County: 48% of tests at or above 4 pCi/L · 3,223 testsBoone County: 69% of tests at or above 4 pCi/L · 1,134 testsBremer County: 53% of tests at or above 4 pCi/L · 957 testsBuchanan County: 51% of tests at or above 4 pCi/L · 564 testsBuena Vista County: 72% of tests at or above 4 pCi/L · 688 testsButler County: 60% of tests at or above 4 pCi/L · 377 testsCalhoun County: 70% of tests at or above 4 pCi/L · 507 testsCarroll County: 78% of tests at or above 4 pCi/L · 594 testsCass County: 77% of tests at or above 4 pCi/L · 327 testsCedar County: 60% of tests at or above 4 pCi/L · 765 testsCerro Gordo County: 59% of tests at or above 4 pCi/L · 1,662 testsCherokee County: 74% of tests at or above 4 pCi/L · 795 testsChickasaw County: 59% of tests at or above 4 pCi/L · 498 testsClarke County: 46% of tests at or above 4 pCi/L · 120 testsClay County: 79% of tests at or above 4 pCi/L · 744 testsClayton County: 63% of tests at or above 4 pCi/L · 310 testsClinton County: 53% of tests at or above 4 pCi/L · 1,375 testsCrawford County: 75% of tests at or above 4 pCi/L · 373 testsDallas County: 59% of tests at or above 4 pCi/L · 2,352 testsDavis County: 42% of tests at or above 4 pCi/L · 85 testsDecatur County: 26% of tests at or above 4 pCi/L · 85 testsDelaware County: 50% of tests at or above 4 pCi/L · 520 testsDes Moines County: 51% of tests at or above 4 pCi/L · 436 testsDickinson County: 70% of tests at or above 4 pCi/L · 831 testsDubuque County: 47% of tests at or above 4 pCi/L · 3,775 testsEmmet County: 71% of tests at or above 4 pCi/L · 420 testsFayette County: 63% of tests at or above 4 pCi/L · 746 testsFloyd County: 60% of tests at or above 4 pCi/L · 697 testsFranklin County: 73% of tests at or above 4 pCi/L · 313 testsFremont County: 70% of tests at or above 4 pCi/L · 205 testsGreene County: 71% of tests at or above 4 pCi/L · 143 testsGrundy County: 67% of tests at or above 4 pCi/L · 501 testsGuthrie County: 71% of tests at or above 4 pCi/L · 257 testsHamilton County: 64% of tests at or above 4 pCi/L · 252 testsHancock County: 65% of tests at or above 4 pCi/L · 640 testsHardin County: 63% of tests at or above 4 pCi/L · 349 testsHarrison County: 70% of tests at or above 4 pCi/L · 367 testsHenry County: 46% of tests at or above 4 pCi/L · 168 testsHoward County: 61% of tests at or above 4 pCi/L · 388 testsHumboldt County: 70% of tests at or above 4 pCi/L · 385 testsIda County: 72% of tests at or above 4 pCi/L · 399 testsIowa County: 59% of tests at or above 4 pCi/L · 519 testsJackson County: 53% of tests at or above 4 pCi/L · 1,056 testsJasper County: 73% of tests at or above 4 pCi/L · 746 testsJefferson County: 34% of tests at or above 4 pCi/L · 841 testsJohnson County: 42% of tests at or above 4 pCi/L · 7,321 testsJones County: 59% of tests at or above 4 pCi/L · 555 testsKeokuk County: 60% of tests at or above 4 pCi/L · 214 testsKossuth County: 66% of tests at or above 4 pCi/L · 434 testsLee County: 44% of tests at or above 4 pCi/L · 351 testsLinn County: 40% of tests at or above 4 pCi/L · 9,395 testsLouisa County: 52% of tests at or above 4 pCi/L · 96 testsLucas County: 39% of tests at or above 4 pCi/L · 84 testsLyon County: 78% of tests at or above 4 pCi/L · 237 testsMadison County: 62% of tests at or above 4 pCi/L · 318 testsMahaska County: 61% of tests at or above 4 pCi/L · 288 testsMarion County: 67% of tests at or above 4 pCi/L · 1,151 testsMarshall County: 70% of tests at or above 4 pCi/L · 570 testsMills County: 70% of tests at or above 4 pCi/L · 465 testsMitchell County: 71% of tests at or above 4 pCi/L · 444 testsMonona County: 75% of tests at or above 4 pCi/L · 603 testsMonroe County: 34% of tests at or above 4 pCi/L · 59 testsMontgomery County: 67% of tests at or above 4 pCi/L · 233 testsMuscatine County: 47% of tests at or above 4 pCi/L · 954 testsO'Brien County: 82% of tests at or above 4 pCi/L · 652 testsOsceola County: 67% of tests at or above 4 pCi/L · 122 testsPage County: 72% of tests at or above 4 pCi/L · 653 testsPalo Alto County: 71% of tests at or above 4 pCi/L · 462 testsPlymouth County: 82% of tests at or above 4 pCi/L · 1,405 testsPocahontas County: 69% of tests at or above 4 pCi/L · 417 testsPolk County: 64% of tests at or above 4 pCi/L · 10,945 testsPottawattamie County: 57% of tests at or above 4 pCi/L · 1,868 testsPoweshiek County: 71% of tests at or above 4 pCi/L · 419 testsRinggold County: 29% of tests at or above 4 pCi/L · 87 testsSac County: 77% of tests at or above 4 pCi/L · 491 testsScott County: 44% of tests at or above 4 pCi/L · 3,520 testsShelby County: 78% of tests at or above 4 pCi/L · 857 testsSioux County: 84% of tests at or above 4 pCi/L · 1,982 testsStory County: 60% of tests at or above 4 pCi/L · 2,568 testsTama County: 68% of tests at or above 4 pCi/L · 333 testsTaylor County: 61% of tests at or above 4 pCi/L · 235 testsUnion County: 62% of tests at or above 4 pCi/L · 131 testsVan Buren County: 32% of tests at or above 4 pCi/L · 56 testsWapello County: 36% of tests at or above 4 pCi/L · 287 testsWarren County: 66% of tests at or above 4 pCi/L · 1,513 testsWashington County: 55% of tests at or above 4 pCi/L · 1,186 testsWayne County: 35% of tests at or above 4 pCi/L · 46 testsWebster County: 69% of tests at or above 4 pCi/L · 1,189 testsWinnebago County: 72% of tests at or above 4 pCi/L · 829 testsWinneshiek County: 66% of tests at or above 4 pCi/L · 1,071 testsWoodbury County: 69% of tests at or above 4 pCi/L · 3,541 testsWorth County: 68% of tests at or above 4 pCi/L · 154 testsWright County: 67% of tests at or above 4 pCi/L · 292 tests
  • Under 10%
  • 10–20%
  • 20–30%
  • 30–40%
  • 40% or more
  • No data

About radon in Iowa

Iowa has the highest share of high-radon homes in the country. The Iowa Radon Survey found that 71.6% of homes were above the EPA's 4 pCi/L action level (Iowa HHS), and the EPA places all 99 Iowa counties in its highest-risk Zone 1.

Iowa's health department no longer publishes county test results, so our Iowa figures come from the CDC's Environmental Public Health Tracking Network, which collects radon tests from laboratories. They cover 95,245 tests from 2008 to 2017, the most recent ten-year period the CDC reports. Across those tests, 58.5% were at or above 4 pCi/L. That is lower than the state survey, partly because the two measure different homes over different years, but by either measure most Iowa homes have high radon.

Even in Iowa, counties differ. In our data, Sioux County in the northwest has the highest share of high results (84%) and Decatur County on the Missouri border the lowest (26%). Every county with data has at least 46 tests on record.

Iowa regulates radon work. Anyone who installs radon mitigation for pay in Iowa must be credentialed by the state (Iowa Admin. Code 641—44). Sellers complete the Real Estate Commission's disclosure statement and must give buyers the "Iowa Radon Home-Buyers and Sellers Fact Sheet" (Iowa Admin. Code 193E). From July 1, 2026, Iowa's building code requires new single- and two-family homes to include a passive radon mitigation system (Iowa HHS).

Free test kits are available to Iowa households through the American Lung Association and the state's Healthy Hometowns program, depending on your county (Iowa HHS). Pick your county below to see its results.

Written and reviewed by Ray Roman · 2026-11-03

Counties

CountyTests% ≥ 4 pCi/LMedian (pCi/L)EPA zone (1993)Source
Adair County9872%9.3Zone 1Iowa radon test results from laboratories through 2017
Adams County8165%6.1Zone 1Iowa radon test results from laboratories through 2017
Allamakee County49273%7.0Zone 1Iowa radon test results from laboratories through 2017
Appanoose County11745%3.7Zone 1Iowa radon test results from laboratories through 2017
Audubon County18978%9.5Zone 1Iowa radon test results from laboratories through 2017
Benton County69662%5.6Zone 1Iowa radon test results from laboratories through 2017
Black Hawk County3,22348%3.8Zone 1Iowa radon test results from laboratories through 2017
Boone County1,13469%6.0Zone 1Iowa radon test results from laboratories through 2017
Bremer County95753%4.3Zone 1Iowa radon test results from laboratories through 2017
Buchanan County56451%4.1Zone 1Iowa radon test results from laboratories through 2017
Buena Vista County68872%6.9Zone 1Iowa radon test results from laboratories through 2017
Butler County37760%5.2Zone 1Iowa radon test results from laboratories through 2017
Calhoun County50770%6.1Zone 1Iowa radon test results from laboratories through 2017
Carroll County59478%7.8Zone 1Iowa radon test results from laboratories through 2017
Cass County32777%8.1Zone 1Iowa radon test results from laboratories through 2017
Cedar County76560%5.0Zone 1Iowa radon test results from laboratories through 2017
Cerro Gordo County1,66259%4.8Zone 1Iowa radon test results from laboratories through 2017
Cherokee County79574%7.6Zone 1Iowa radon test results from laboratories through 2017
Chickasaw County49859%4.9Zone 1Iowa radon test results from laboratories through 2017
Clarke County12046%3.5Zone 1Iowa radon test results from laboratories through 2017
Clay County74479%9.6Zone 1Iowa radon test results from laboratories through 2017
Clayton County31063%5.8Zone 1Iowa radon test results from laboratories through 2017
Clinton County1,37553%4.3Zone 1Iowa radon test results from laboratories through 2017
Crawford County37375%7.0Zone 1Iowa radon test results from laboratories through 2017
Dallas County2,35259%4.9Zone 1Iowa radon test results from laboratories through 2017
Davis County8542%3.1Zone 1Iowa radon test results from laboratories through 2017
Decatur County8526%2.5Zone 1Iowa radon test results from laboratories through 2017
Delaware County52050%4.0Zone 1Iowa radon test results from laboratories through 2017
Des Moines County43651%4.2Zone 1Iowa radon test results from laboratories through 2017
Dickinson County83170%7.0Zone 1Iowa radon test results from laboratories through 2017
Dubuque County3,77547%3.6Zone 1Iowa radon test results from laboratories through 2017
Emmet County42071%6.3Zone 1Iowa radon test results from laboratories through 2017
Fayette County74663%5.6Zone 1Iowa radon test results from laboratories through 2017
Floyd County69760%5.1Zone 1Iowa radon test results from laboratories through 2017
Franklin County31373%6.2Zone 1Iowa radon test results from laboratories through 2017
Fremont County20570%7.2Zone 1Iowa radon test results from laboratories through 2017
Greene County14371%6.2Zone 1Iowa radon test results from laboratories through 2017
Grundy County50167%6.9Zone 1Iowa radon test results from laboratories through 2017
Guthrie County25771%6.9Zone 1Iowa radon test results from laboratories through 2017
Hamilton County25264%5.5Zone 1Iowa radon test results from laboratories through 2017
Hancock County64065%5.5Zone 1Iowa radon test results from laboratories through 2017
Hardin County34963%5.6Zone 1Iowa radon test results from laboratories through 2017
Harrison County36770%6.2Zone 1Iowa radon test results from laboratories through 2017
Henry County16846%3.4Zone 1Iowa radon test results from laboratories through 2017
Howard County38861%5.9Zone 1Iowa radon test results from laboratories through 2017
Humboldt County38570%7.0Zone 1Iowa radon test results from laboratories through 2017
Ida County39972%7.4Zone 1Iowa radon test results from laboratories through 2017
Iowa County51959%5.1Zone 1Iowa radon test results from laboratories through 2017
Jackson County1,05653%4.1Zone 1Iowa radon test results from laboratories through 2017
Jasper County74673%8.2Zone 1Iowa radon test results from laboratories through 2017
Jefferson County84134%2.6Zone 1Iowa radon test results from laboratories through 2017
Johnson County7,32142%3.2Zone 1Iowa radon test results from laboratories through 2017
Jones County55559%5.1Zone 1Iowa radon test results from laboratories through 2017
Keokuk County21460%5.2Zone 1Iowa radon test results from laboratories through 2017
Kossuth County43466%5.7Zone 1Iowa radon test results from laboratories through 2017
Lee County35144%3.2Zone 1Iowa radon test results from laboratories through 2017
Linn County9,39540%3.0Zone 1Iowa radon test results from laboratories through 2017
Louisa County9652%4.1Zone 1Iowa radon test results from laboratories through 2017
Lucas County8439%3.3Zone 1Iowa radon test results from laboratories through 2017
Lyon County23778%8.3Zone 1Iowa radon test results from laboratories through 2017
Madison County31862%6.0Zone 1Iowa radon test results from laboratories through 2017
Mahaska County28861%5.2Zone 1Iowa radon test results from laboratories through 2017
Marion County1,15167%6.0Zone 1Iowa radon test results from laboratories through 2017
Marshall County57070%8.2Zone 1Iowa radon test results from laboratories through 2017
Mills County46570%6.1Zone 1Iowa radon test results from laboratories through 2017
Mitchell County44471%6.4Zone 1Iowa radon test results from laboratories through 2017
Monona County60375%7.0Zone 1Iowa radon test results from laboratories through 2017
Monroe County5934%2.9Zone 1Iowa radon test results from laboratories through 2017
Montgomery County23367%6.1Zone 1Iowa radon test results from laboratories through 2017
Muscatine County95447%3.7Zone 1Iowa radon test results from laboratories through 2017
O'Brien County65282%8.9Zone 1Iowa radon test results from laboratories through 2017
Osceola County12267%6.8Zone 1Iowa radon test results from laboratories through 2017
Page County65372%7.2Zone 1Iowa radon test results from laboratories through 2017
Palo Alto County46271%5.9Zone 1Iowa radon test results from laboratories through 2017
Plymouth County1,40582%8.6Zone 1Iowa radon test results from laboratories through 2017
Pocahontas County41769%6.4Zone 1Iowa radon test results from laboratories through 2017
Polk County10,94564%5.6Zone 1Iowa radon test results from laboratories through 2017
Pottawattamie County1,86857%4.7Zone 1Iowa radon test results from laboratories through 2017
Poweshiek County41971%7.2Zone 1Iowa radon test results from laboratories through 2017
Ringgold County8729%2.6Zone 1Iowa radon test results from laboratories through 2017
Sac County49177%7.0Zone 1Iowa radon test results from laboratories through 2017
Scott County3,52044%3.3Zone 1Iowa radon test results from laboratories through 2017
Shelby County85778%9.0Zone 1Iowa radon test results from laboratories through 2017
Sioux County1,98284%10.7Zone 1Iowa radon test results from laboratories through 2017
Story County2,56860%5.0Zone 1Iowa radon test results from laboratories through 2017
Tama County33368%7.0Zone 1Iowa radon test results from laboratories through 2017
Taylor County23561%4.6Zone 1Iowa radon test results from laboratories through 2017
Union County13162%4.9Zone 1Iowa radon test results from laboratories through 2017
Van Buren County5632%2.3Zone 1Iowa radon test results from laboratories through 2017
Wapello County28736%2.7Zone 1Iowa radon test results from laboratories through 2017
Warren County1,51366%6.3Zone 1Iowa radon test results from laboratories through 2017
Washington County1,18655%4.6Zone 1Iowa radon test results from laboratories through 2017
Wayne County4635%3.0Zone 1Iowa radon test results from laboratories through 2017
Webster County1,18969%6.5Zone 1Iowa radon test results from laboratories through 2017
Winnebago County82972%6.7Zone 1Iowa radon test results from laboratories through 2017
Winneshiek County1,07166%6.2Zone 1Iowa radon test results from laboratories through 2017
Woodbury County3,54169%6.1Zone 1Iowa radon test results from laboratories through 2017
Worth County15468%6.0Zone 1Iowa radon test results from laboratories through 2017
Wright County29267%6.2Zone 1Iowa radon test results from laboratories through 2017

Test your home

County figures show how often tests come back high, not the level in your home. Only a test tells you that: see how to test for radon.

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