Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Walworth County, South Dakota
EPA puts Walworth County in Zone 1, its highest radon zone, and only 18 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
61.8%
Edmunds County
- Edmunds
- 61.8%
1 of 6 neighbours have 30+ tests, 2006 to 2015
Nearest county
61.8%
Edmunds County, 40 miles
- Edmunds
- 61.8%
- SD
- 58.8%
Share at 4+ pCi/L, 68 tests, 2006 to 2015
Ground above low
100.0%
1.0 pts above SD
- Walworth
- 100.0%
- SD
- 99.0%
Share of land USGS rates moderate or high potential
Tests reported
18
Too few for a share
- Walworth
- 18
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Read a result for Walworth County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The data
Walworth County, At a glance
Walworth County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Walworth County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Walworth County, 2008 to 2017, laboratory
CDC holds 18 reported tests for Walworth County over the 2008 to 2017 laboratory totals, with a median of 4.7 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Walworth County beside the counties around it is how this page reads it.
What these figures count
Only 18 tests were reported to CDC for Walworth County over 2008 to 2017 (laboratory totals), and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Walworth County, Compared
Walworth County radon figures, compared
Calculated by Radon411CDC's largest figure for Walworth County rests on 18 tests over the 2008 to 2017 laboratory totals, 10 of them at or above 4 pCi/L, so each test moves its share by 5.6 points and no rank or comparison is drawn from it. Results reached as high as 21.3 pCi/L, with a middle value of 4.7 pCi/L.
Edmunds County, the one bordering county with a figure over the 2006 to 2015 laboratory totals, reported 61.8% of its tests at or above 4 pCi/L. Farther out, Hughes County (72 miles away) at 66.7%, Brown County (82 miles away) at 59.6% and Beadle County (111 miles away) at 63.0% have figures too. Pooled across 63 South Dakota counties, 58.8% of reported tests reached that level; across every county in the country with a figure, 36.3%.
Statewide for the same period, Bon Homme County reported the highest share (79.5%) and Davison County the lowest (47.9%). EPA's 1993 map puts Walworth County in Zone 1, the map's highest label: a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Walworth County, Geology
The ground under Walworth County
PredictedUSGS's geologic map puts all of Walworth County's mapped land in one class: high radon potential. All of it lies in the area the map calls Missouri Coteau/James River Lowland/Coteau des Prairies, to which USGS gives a radon index of 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Missouri Coteau/James River Lowland/Coteau des Prairies | Glacial drift derived largely from Cretaceous marine shale. | High | 14 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Walworth County beside the ground around it
Walworth County has more high-potential ground than South Dakota as a whole: 100% of its land against 56.7%. Of the 6 counties that border it, none has as large a share of high-potential ground; Edmunds County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Walworth County, Local resources
Radon testing and mitigation in Walworth County
- South Dakota's radon programDepartment of Agriculture and Natural ResourcesSouth Dakota's radon program offers free or discounted test kits, and answers questions about testing and mitigation in South Dakota.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Department of Agriculture and Natural Resources (DANR) will provide 500 free Radon test kits to South Dakota Residents.
- Compare kits
- Professionals in South Dakota5 professionals are listed in South Dakota.
What South Dakota's program says
- Phone
- 1-800-438-3367
What it means
Walworth County, Questions
Questions about radon in Walworth County
Are radon levels high in Walworth County?
Over the 2008 to 2017 laboratory totals, 55.6% of the radon tests reported to CDC for Walworth County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.7 pCi/L. Edmunds County, the one bordering county with a figure over the 2006 to 2015 laboratory totals, reported 61.8% of its tests at or above 4 pCi/L.
Which counties border Walworth County?
Walworth County borders 6 counties: Potter County, Campbell County, Edmunds County, McPherson County, Dewey County and Corson County.
Products
Walworth County, Products
Testing a home in Walworth County
No CDC figure names Walworth County; the nearest county with one, Edmunds County (40 miles away), reported 61.8% of its tests at or above 4 pCi/L over the 2006 to 2015 laboratory totals, the only reading nearby until a test of this home. In Zone 1 the year-round level in Walworth County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
Monitor
Wave Plus battery radon and air quality monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- App only
Method: Alpha spectrometry
Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Walworth County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Walworth County
Explore
Walworth County, Bordering counties
Counties bordering Walworth County
Calculated by Radon411- Radon levels in Edmunds CountyEPA zone 1
61.8%at or above 4 pCi/L
Median 5.0 pCi/L · 68 tests
- Radon levels in McPherson CountyEPA zone 1
52.9%at or above 4 pCi/L
Median 4.3 pCi/L · 17 tests
- Radon levels in Corson CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 8.0 pCi/L · 2 tests
- Radon levels in Campbell CountyEPA zone 1
40.0%at or above 4 pCi/L
Median 3.9 pCi/L · 5 tests
- Radon levels in Potter CountyEPA zone 1
0.0%at or above 4 pCi/L
Median 1.2 pCi/L · 1 test
- Radon levels in Dewey CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 1 test
Walworth County, Cities and towns
Cities and towns in Walworth County
About 5,217 people live in Walworth County by the Census Bureau's estimate for July 1, 2025, 74 fewer than in 2020 (−1.4%). Spread over its land, that is 7.4 people to the square mile. Mobridge alone is home to 3,192 of them, 61.2% of the total. Together its 6 incorporated places hold 78.6% of those residents; the other 21.4% live outside any of them. Reported testing is thin here: 18 tests over 2008 to 2017, or 3.5 for every 1,000 residents (2025 estimate), where South Dakota as a whole comes to 6.7.
From Mobridge to Lowry, CDC publishes no figure by town: each reads Walworth County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Mobridge | 3,192 | −1.7% | 61.2% |
| Selby | 600 | −1.5% | 11.5% |
| Java | 119 | −1.7% | 2.3% |
| Glenham | 106 | −2.8% | 2.0% |
| Akaska | 81 | +6.6% | 1.6% |
| Lowry | 5 | Level | Under 0.1% |
6 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Walworth County, Homes
Homes in Walworth County
Walworth County is a place of houses on their own lots: 79% of its 2,941 homes are detached single-family houses, against 67% across South Dakota. The homes are older than South Dakota's as a whole: half were built before 1966 (1979 for South Dakota), and 40% date from before 1960. 74% of occupied homes are lived in by their owner (South Dakota: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Walworth County | South Dakota |
|---|---|---|
| Housing units | 2,941 | 402,364 |
| Detached houses | 79% | 67% |
| In buildings of 5 or more | 5% | 16% |
| Mobile homes | 12% | 8% |
| Built before 1960 | 40% | 29% |
| Built since 2000 | 15% | 28% |
| Middle year built | 1966 | 1979 |
| Owner-occupied | 74% | 69% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.