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, Wisconsin
EPA puts Walworth County in Zone 1, its highest radon zone, and 37.9% of its 340 reported radon tests (2023) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
37.9%
2.2 pts above WI
- Walworth
- 37.9%
- Wisconsin
- 35.7%
340 tests, 2023
Median result
2.8pCi/L
Below action level
- Walworth
- 2.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
340
17th of 69 by tests
- Walworth
- 340
- Dane
- 2,887
Reported to CDC before any fix, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Wisconsin
35 of 69
Middle half
- Walworth
- 37.9%
- Langlade
- 65.8%
By share, of 69 with 30+ tests
Read a result for Walworth County
Starts at Walworth County's median, 2.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.8 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Walworth County's median reported result, 2023.
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, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 54.6% |
| 2015 | 59.5% |
| 2016 | 57.7% |
| 2017 | 56.0% |
| 2019 | 50.2% |
| 2020 | 39.9% |
| 2021 | 54.1% |
| 2022 | 40.6% |
| 2023 | 37.9% |
2023: 37.9%. Across these years the share ran from 37.9% to 59.5%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 340 tests reported to CDC for Walworth County over 2023, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Walworth County, Compared
Walworth County radon figures, compared
Calculated by Radon411In Walworth County, about 4 in 10 reported tests in 2023 (129 of 340) were at or above EPA's action level. Against the national pool of 33.4%, the gap is 4.5 points higher. Across 72 Wisconsin counties pooled together, 35.7% of tests reached that level, so Walworth County runs 2.2 points above its state.
Of 5 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 37.3% (Racine County) to 49.9% (Rock County). By share, Walworth County is 35th of 69 Wisconsin counties with 30 or more tests for the same period.
Year by year, 2014 opened at 54.6% and 2023 closed at 37.9% (down 16.7 points), with 2015 the high at 59.5%. Half the tests came in under 2.8 pCi/L and half over it; the single highest reached 66.6 pCi/L. Below the action level, 131 tests (38.5%) came in under 2 pCi/L, against 41.4% statewide, and 80 tests (23.5%) fell between 2 and 4, against 23.0% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 37.9% share point the same way here. USGS geology rates 100% of the county's land high radon potential. CDC also counts 8 tests taken after mitigation in Walworth County for the same period: tests in homes where a fix was already in.
The busiest year on file was 2015, with 454 tests reported; the quietest, 2021, had 157.
Walworth CountyWisconsin, pooled
| Year | Tests | Walworth County, at or above 4 pCi/L | Wisconsin, pooled |
|---|---|---|---|
| 2014 | 355 | 54.6% | 51.1% |
| 2015 | 454 | 59.5% | 51.6% |
| 2016 | 265 | 57.7% | 45.2% |
| 2017 | 234 | 56.0% | 44.8% |
| 2019 | 225 | 50.2% | 42.9% |
| 2020 | 213 | 39.9% | 27.0% |
| 2021 | 157 | 54.1% | 39.9% |
| 2022 | 234 | 40.6% | 42.9% |
| 2023 | 340 | 37.9% | 35.7% |
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. 99.0% of it lies in the area the map calls Eastern Ridges and Lowlands, to which USGS gives a radon index of 12, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Eastern Ridges and Lowlands | Glacial deposits derived from Ordovician carbonate rocks. | High | 12 | 99.0% |
| Bloomington Ridged Plain | Wisconsinan glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 0.6% |
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 Wisconsin as a whole: 100% of its land against 34.8%. Of the 7 counties that border it, none has as large a share of high-potential ground; Boone County, IL 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
Listed radon businesses with an address in Walworth County:
- Wisconsin's radon programWisconsin Department of Health ServicesWisconsin's radon program does not license radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Wisconsin.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We recommend starting with your regional Radon Information Center since many centers provide test kits for free or reduced cost, and often with laboratory fees covered.
- Compare kits
- Professionals in Wisconsin19 professionals are listed in Wisconsin.
Listed radon professionals by town: Williams Bay, Genoa City
What Wisconsin's program says
- Phone
- 1-888-569-7236
- DHSRadon@dhs.wisconsin.gov
- Licensing of radon professionals
The State of Wisconsin does not require contractors performing radon measurement or mitigation work to be state licensed or nationally certified.
What it means
Walworth County, Questions
Questions about radon in Walworth County
Are radon levels high in Walworth County?
In 2023, 37.9% of the radon tests reported to CDC for Walworth County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.8 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 34 reported a higher share; pooled, the state comes to 35.7%.
Which counties border Walworth County?
Walworth County borders 7 counties: McHenry County, IL, Racine County, WI, Kenosha County, WI, Rock County, WI, Boone County, IL, Jefferson County, WI and Waukesha County, WI.
Products
Walworth County, Products
Testing a home in Walworth County
In Walworth County, 37.9% of 340 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. 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
MonitorX-Sense
XR0B-SR battery digital radon monitor with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Alpha spectrometry
First reading: Within 24 hours
Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
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 Rock County, WIEPA zone 1
49.9%at or above 4 pCi/L
Median 3.9 pCi/L · 451 tests · 12.0 points above Walworth County
- Radon levels in Jefferson County, WIEPA zone 1
44.3%at or above 4 pCi/L
Median 3.5 pCi/L · 296 tests · 6.4 points above Walworth County
- Radon levels in Waukesha County, WIEPA zone 1
43.2%at or above 4 pCi/L
Median 3.2 pCi/L · 1,633 tests · 5.3 points above Walworth County
- Radon levels in Kenosha County, WIEPA zone 2
42.4%at or above 4 pCi/L
Median 3.4 pCi/L · 415 tests · 4.5 points above Walworth County
- Radon levels in Racine County, WIEPA zone 2
37.3%at or above 4 pCi/L
Median 2.7 pCi/L · 445 tests · 0.6 points below Walworth County
- Radon levels in McHenry County, ILEPA zone 2
No CDC figure for 2023; its page reads it against its own neighbours.
- Radon levels in Boone County, ILEPA zone 1
No CDC figure for 2023; its page reads it against its own neighbours.
Walworth County, Cities and towns
Cities and towns in Walworth County
The Census Bureau estimates 106,127 residents in Walworth County for July 1, 2025, 803 more than in 2020 (+0.8%). That works out to 191 people per square mile of land. Whitewater, the largest place on its list (16,038 residents in all), extends beyond Walworth County, so no share of the total is worked out for it. CDC's 340 reported tests for 2023 work out to 3.2 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.
From Whitewater to Darien, CDC publishes no figure by town: each reads Walworth County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Whitewaterextends beyond Walworth County | 16,038 | −0.6% | Counted whole |
| Burlingtonextends beyond Walworth County | 10,951 | −0.9% | Counted whole |
| Elkhorn | 10,045 | −2.2% | 9.5% |
| Delavan | 9,228 | +8.5% | 8.7% |
| Lake Geneva | 8,818 | +5.9% | 8.3% |
| Mukwonagoextends beyond Walworth County | 8,544 | +2.9% | Counted whole |
| Bloomfield | 6,369 | −1.1% | 6.0% |
| East Troy | 4,988 | +6.3% | 4.7% |
| Williams Bay | 2,935 | −0.4% | 2.8% |
| Genoa Cityextends beyond Walworth County | 2,866 | −3.0% | Counted whole |
| Walworth | 2,759 | −0.1% | 2.6% |
| Fontana-on-Geneva Lake | 1,886 | −0.9% | 1.8% |
- Sharon
- Darien
14 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Walworth County is counted whole, so it has no share.
Walworth County, Homes
Homes in Walworth County
Of Walworth County's 53,508 homes, 70% are detached houses, against 66% across Wisconsin; 16% are in buildings of five or more homes. Half of its homes were built before 1977, close to Wisconsin's 1975: 31% date from before 1960 and 22% from 2000 or later. 71% of occupied homes are lived in by their owner (Wisconsin: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Walworth County | Wisconsin |
|---|---|---|
| Housing units | 53,508 | 2,750,750 |
| Detached houses | 70% | 66% |
| In buildings of 5 or more | 16% | 17% |
| Mobile homes | 2% | 3% |
| Built before 1960 | 31% | 34% |
| Built since 2000 | 22% | 20% |
| Middle year built | 1977 | 1975 |
| Owner-occupied | 71% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.