Radon in South Dakota: radon map by county
EPA's Map of Radon Zones puts 48 of South Dakota's 66 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 18 in Zone 2 and 0 in Zone 3. Of 4,760 building tests that radon laboratories reported for 2008 to 2017, 58.6% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 2 of 42 states with 1,000+ tests). The highest county share is Lake County (76% of 43 tests).
Radon by county in South Dakota
| County | EPA zone | Lab tests | Median | 4+ pCi/L |
|---|---|---|---|---|
| Aurora County | Zone 1 | 12 | 2.7 | 40% |
| Beadle County | Zone 1 | 40 | 4.8 | 59.3% |
| Bennett County | Zone 2 | 2 | 3.0 | 33.3% |
| Bon Homme County | Zone 1 | 45 | 7.2 | 74.2% |
| Brookings County | Zone 1 | 276 | 6.6 | 68.5% |
| Brown County | Zone 1 | 56 | 5.9 | 71% |
| Brule County | Zone 1 | 27 | 6.4 | 67.6% |
| Buffalo County | Zone 1 | n/a | n/a | n/a |
| Butte County | Zone 2 | 16 | 5.4 | 58.3% |
| Campbell County | Zone 1 | 3 | 2.4 | 28.6% |
| Charles Mix County | Zone 1 | 18 | 6.5 | 60.7% |
| Clark County | Zone 1 | 6 | 5.9 | 77.8% |
| Clay County | Zone 1 | 57 | 4.2 | 51.8% |
| Codington County | Zone 1 | 58 | 5.8 | 64.9% |
| Corson County | Zone 1 | n/a | n/a | n/a |
| Custer County | Zone 2 | 59 | 6.2 | 65.7% |
| Davison County | Zone 1 | 67 | 3.8 | 48.8% |
| Day County | Zone 1 | 8 | 4.5 | 54.5% |
| Deuel County | Zone 1 | 14 | 6.2 | 76% |
| Dewey County | Zone 2 | 1 | 0.6 | 0% |
| Douglas County | Zone 1 | 2 | 1.3 | 0% |
| Edmunds County | Zone 1 | 10 | 5.9 | 66.7% |
| Fall River County | Zone 2 | 15 | 5.8 | 62.5% |
| Faulk County | Zone 1 | 1 | 32.2 | 100% |
| Grant County | Zone 1 | 47 | 5.0 | 55.1% |
| Gregory County | Zone 2 | 11 | 5.3 | 66.7% |
| Haakon County | Zone 2 | 3 | 8.0 | 80% |
| Hamlin County | Zone 1 | 11 | 6.3 | 76.9% |
| Hand County | Zone 1 | 8 | 4.8 | 81.8% |
| Hanson County | Zone 1 | 6 | 2.8 | 25% |
| Harding County | Zone 2 | 1 | 5.1 | 100% |
| Hughes County | Zone 1 | 43 | 5.7 | 70.4% |
| Hutchinson County | Zone 1 | 28 | 5.8 | 66.7% |
| Hyde County | Zone 1 | 4 | 4.9 | 57.1% |
| Jackson County | Zone 2 | 1 | 1.1 | 0% |
| Jerauld County | Zone 1 | 17 | 8.8 | 69.6% |
| Jones County | Zone 2 | 4 | 20.8 | 75% |
| Kingsbury County | Zone 1 | 27 | 7.4 | 68.2% |
| Lake County | Zone 1 | 43 | 8.5 | 76% |
| Lawrence County | Zone 2 | 119 | 5.3 | 56.9% |
| Lincoln County | Zone 1 | 671 | 4.7 | 56.5% |
| Lyman County | Zone 1 | 2 | 22.1 | 100% |
| Marshall County | Zone 1 | 6 | 10.5 | 81.3% |
| McCook County | Zone 1 | 24 | 3.9 | 50% |
| McPherson County | Zone 1 | 8 | 4.8 | 58.3% |
| Meade County | Zone 2 | 134 | 4.1 | 51.8% |
| Mellette County | Zone 2 | n/a | n/a | n/a |
| Miner County | Zone 1 | 4 | 3.9 | 50% |
| Minnehaha County | Zone 1 | 1,633 | 4.8 | 58.5% |
| Moody County | Zone 1 | 15 | 6.2 | 70% |
| Oglala Lakota County | Zone 2* | n/a | n/a | n/a |
| Pennington County | Zone 2 | 662 | 4.3 | 53.6% |
| Perkins County | Zone 1 | 8 | 8.1 | 76.9% |
| Potter County | Zone 1 | 1 | 1.2 | 0% |
| Roberts County | Zone 1 | 19 | 3.8 | 46.2% |
| Sanborn County | Zone 1 | 5 | 5.5 | 71.4% |
| Spink County | Zone 1 | 15 | 3.8 | 50% |
| Stanley County | Zone 1 | 3 | 4.2 | 66.7% |
| Sully County | Zone 1 | 1 | 4.1 | 100% |
| Todd County | Zone 2 | 1 | 4.7 | 100% |
| Tripp County | Zone 2 | 8 | 4.2 | 55.6% |
| Turner County | Zone 1 | 48 | 4.8 | 58.6% |
| Union County | Zone 1 | 213 | 4.1 | 51.1% |
| Walworth County | Zone 1 | 15 | 4.7 | 55.6% |
| Yankton County | Zone 1 | 97 | 6.3 | 72.9% |
| Ziebach County | Zone 2 | 1 | 11.6 | 100% |
Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report). * Zone of the county or area this one was renamed from or created from after 1993 (see the county page).
What the zones mean
Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.
Radon in South Dakota: questions
What radon zone is South Dakota?
EPA's 1993 map does not give states one zone; it zones each county. In South Dakota, 48 counties are Zone 1, 18 Zone 2 and 0 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".
Which South Dakota counties have the highest radon levels?
By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Lake County 76% (median 8.5 pCi/L, 43 tests); Bon Homme County 74.2% (median 7.2 pCi/L, 45 tests); Yankton County 72.9% (median 6.3 pCi/L, 97 tests); Brown County 71% (median 5.9 pCi/L, 56 tests); Hughes County 70.4% (median 5.7 pCi/L, 43 tests).
How common is high radon in South Dakota?
58.6% of the 4,760 tests in the laboratory data for South Dakota (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.
Should I test for radon in South Dakota?
Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
States bordering South Dakota
Other free hazard lookups
- Radon by county and ZIP codeEPA radon zone and the radon test results on file for any county, ZIP code or address.
- Fault lines near an addressUSGS-mapped earthquake faults within 5 miles, their age and slip rate, and the USGS seismic hazard value.
- Power lines near an addressHigh-voltage transmission lines within 1 mile from federal maps, with voltage and distance.
- Flood zone lookupThe FEMA flood zone mapped at any US address. Not an official flood zone determination.
- Superfund sites near an addressThe nearest EPA Superfund (NPL) sites and their status.
All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).
Superfund sites in South Dakota · Radon map of every state
Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.