Locations and reports
Radon Levels in Washington County, Wisconsin
What this means for you
- Your area: EPA rates Washington County Zone 1, the highest of its three radon zones. That is a prediction for the whole county, and homes with elevated levels occur in all three zones.
- Local tests: Of 399 radon tests reported to CDC for Washington County (2023), 47.9% were at or above 4 pCi/L, EPA's action level.
- Your home: The only way to know your home’s level is to test it.
pCi/L (picocuries per liter) is the unit radon is measured in. EPA recommends fixing a home at 4 pCi/L or above, its action level.
In 2023, 47.9% of the radon tests reported to CDC for Washington County, Wisconsin came back at or above the EPA action level of 4 pCi/L, and the median result was 3.8 pCi/L. EPA's Map of Radon Zones places the county in Zone 1, highest predicted potential. Radon levels vary from home to home, so only a test measures the level in yours.
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county as a whole.
This is a county-level geologic prediction. It is not a measurement of any address, and houses with elevated radon are found in all three zones.
USGS geologic potential: Low across 100% of the county's land area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Washington County, 2023
- Tests reported
- 399
- At or above 4 pCi/L
- 47.9%
- Median result
- 3.8 pCi/L
Of 399 pre-mitigation tests reported to CDC, not homes in this area. CDC publishes the share in each band, not a count per band, so the per-band counts in the table are calculated by Radon411 and rounded to add up to the published total.
| Result band | Tests Calculated by Radon411 | Share Measured |
|---|---|---|
| Under 2 pCi/L | 117 | 29.3% |
| 2 to 4 pCi/L | 91 | 22.8% |
| 4 pCi/L and above | 191 | 47.9% |
Distribution of tested buildings, not this house. People testing before a sale, or because they suspect a problem, are over-represented in any reported testing data.
Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Washington County, In figures
Washington County in figures
What the published data says about Washington County, in words. A zone and a share of tests describe an area, never the level in any one home.
Predicted
PredictedEPA places Washington County in Zone 1, highest predicted potential, as it does 27 other counties of Wisconsin's 72.
Of the 6 bordering counties, EPA places Dodge County, Fond du Lac County and Waukesha County in Zone 1 and Milwaukee County, Ozaukee County and Sheboygan County in Zone 2.
Reported tests
MeasuredCDC has annual figures for Washington County for 9 years, 2014 to 2023. In 2023, 47.9% of 399 reported tests were at or above 4 pCi/L.
Across those years the share ranged from 45.5% (2020) to 56.3% (2014). Few tests in a year can move it a long way.
Local record
Wisconsin's radon program and its page are under Local resources.
The county's largest incorporated places are Milwaukee, West Bend and Germantown; the figures here cover them as part of the county.
Washington County, Reported testing
Reported testing over time
MeasuredNo figures are published for 2018. The axis keeps the space for the missing year and the line is not drawn across it.
| Year | Median reported result | Highest reported result | Share of tests at or above 4 pCi/L |
|---|---|---|---|
| 2014 | 4.6 pCi/L | 81.6 pCi/L | 56.3% |
| 2015 | 4.4 pCi/L | 84.2 pCi/L | 55.0% |
| 2016 | 4.0 pCi/L | 108.6 pCi/L | 50.2% |
| 2017 | 3.6 pCi/L | 58.6 pCi/L | 47.9% |
| 2019 | 3.9 pCi/L | 65.7 pCi/L | 49.9% |
| 2020 | 3.6 pCi/L | 70.8 pCi/L | 45.5% |
| 2021 | 3.8 pCi/L | 65.4 pCi/L | 47.8% |
| 2022 | 3.5 pCi/L | 43.4 pCi/L | 46.1% |
| 2023 | 3.8 pCi/L | 45.6 pCi/L | 47.9% |
What these figures count
Every percentage here is a share of radon tests reported to CDC for Washington County in 2023. It is not a share of homes in Washington County, and it is not a random sample: it counts only the tests people chose to run and that were reported.
The shares and the median are calculated from pre-mitigation tests (399 for 2023). CDC also reports the number of buildings tested (364), a different count, so the two totals are not interchangeable.
Washington County, Comparison
How Washington County compares
MeasuredWashington County's own published CDC figures beside those of the counties that border it, for the same period.
Share of reported tests at or above 4 pCi/L
Measured2023, highest first. Each county’s own published CDC figure.
- Dodge CountyWI257 tests54.9%
- Washington CountyThis page399 tests47.9%
- Ozaukee CountyWI445 tests45.8%
- Waukesha CountyWI1,633 tests43.2%
- Sheboygan CountyWI399 tests42.9%
- Milwaukee CountyWI2,605 tests20.2%
- Fond du Lac CountyWI984 tests19.6%
Median reported result
Measured2023, highest first. Each county’s own published CDC figure.
- Dodge CountyWI257 tests4.8 pCi/L
- Washington CountyThis page399 tests3.8 pCi/L
- Ozaukee CountyWI445 tests3.6 pCi/L
- Sheboygan CountyWI399 tests3.3 pCi/L
- Waukesha CountyWI1,633 tests3.2 pCi/L
- Milwaukee CountyWI2,605 tests1.5 pCi/L
- Fond du Lac CountyWI984 tests1.4 pCi/L
Each figure is that county’s own published CDC figure for 2023, counting radon tests reported to CDC, not homes. Washington County is this page. Nothing is averaged or combined across counties. The test count beside each county is CDC’s published number of pre-mitigation tests behind its figures. Figures from few tests can swing widely from year to year. Every Wisconsin county’s own figure is in the Wisconsin county table.
CDC publishes this figure only for counties here, so there is no state or national number to compare Washington County, Wisconsin with.
Washington County, Bordering counties
Counties bordering Washington County
Calculated by Radon4116 counties share a boundary with Washington County, computed from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county’s report can be worth reading alongside this one.
- Ozaukee CountyWIZone 2: Moderate predicted potential
- Waukesha CountyWIZone 1: Highest predicted potential
- Dodge CountyWIZone 1: Highest predicted potential
- Milwaukee CountyWIZone 2: Moderate predicted potential
- Sheboygan CountyWIZone 2: Moderate predicted potential
- Fond du Lac CountyWIZone 1: Highest predicted potential
Washington County, Local resources
Local resources in Wisconsin
Who to ask in Wisconsin: the state's radon program, test kits and professionals.
Wisconsin's radon program
Wisconsin Department of Health Services
Wisconsin’s radon program answers questions about testing, mitigation and the rules where you live.
- 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.
Test kits
The 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.
Radon professionals
13 professionals are listed in Wisconsin.
Professionals in WisconsinWashington County, Cities and towns
Cities and towns in Washington County
The radon figures on this page are for Washington County as a whole. They do not differ by city or town.
- Milwaukee (part)
- West Bend
- Germantown
- Hartford (part)
- Richfield
- Jackson
- Slinger
- Kewaskum (part)
- Newburg (part)
9 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county.
Washington County, Questions
Questions about radon in Washington County
Common questions8 questions, answered from the figures above
Are radon levels high in Washington County?
In 2023, 47.9% of the radon tests reported to CDC for Washington County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. That is a share of reported tests, not of homes. EPA places Washington County in Zone 1, highest predicted potential, a predicted average indoor screening level greater than 4 pCi/L. Homes with elevated levels occur in all three zones, so the figures describe the area, not your house. Testing is the only way to know the radon level in a specific building.
How do I get a radon test in Washington County?
EPA says you can test your home yourself or hire a qualified radon test company, and that either approach takes only a small amount of time and effort. No certified tester listed on Radon411 names Washington County as a service area yet. The Wisconsin radon program is the place to ask about certified testers and any test kit offer it runs.
How to test a homeTest kits comparedFree and low-cost kits by stateWisconsin radon program
Who does radon mitigation in Washington County?
No listed mitigator names Washington County as a service area yet; the Wisconsin directory lists 13 companies. EPA recommends having a qualified contractor fix a home with a radon problem, because lowering high radon levels takes technical knowledge and special skills, and some states require the work to be done by a licensed or certified professional. Your state radon program is the place to check whether Wisconsin requires one.
How radon mitigation worksWhat mitigation costsMitigators in Wisconsin
What EPA radon zone is Washington County in?
EPA places Washington County, Wisconsin in Zone 1, which EPA describes as highest predicted potential for the area. A zone is a prediction for the whole county and never determines whether a particular home should be tested. EPA recommends testing every home regardless of zone.
Should I test my home in Washington County?
Yes. Testing is the only way to know the radon level in a specific building. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. How to test a home.
When is the best time of year to test?
EPA says short-term tests stay in the home from 2 to 90 days and that all radon tests should run a minimum of 48 hours; long-term tests stay more than 90 days. EPA's guides do not name a best season: they say radon levels tend to vary from day to day and season to season, so a long-term test is more likely than a short-term test to tell you the year-round average.
What does it cost to test?
EPA's Citizen's Guide calls testing easy and inexpensive, and EPA's Home Buyer's and Seller's Guide says passive short-term and long-term devices are generally inexpensive, while active devices may cost more. No national average price is published for this, so Radon411 does not give one. What testing costs.
Which counties border Washington County?
Washington County borders 6 counties, derived from Census county geometry. Radon potential follows geology rather than county lines, so a bordering county's report can be relevant.
What these figures mean if you own, buy, sell or rent
The reported-test figures on this page describe Washington County, Wisconsin in 2023. They describe tests other people carried out in other buildings, and none of them measures yours.
- How to test a home
If you own your home
Test the lowest lived-in level; a short-term kit screens in days, a long-term kit reflects the year.
- Buying a house: radon guide
If you are buying
Ask for past results and any system's post-mitigation test, and test during the sale.
- Selling a house: radon guide
If you are selling
Testing before you list puts the timing in your hands; disclosure rules differ by state.
- Radon in rental homes
If you rent, or rent out a home
A tenant can test; a fix is the owner's to make, and duties differ by state.
How long a test has to run, under what conditions, and what EPA says a result means: the testing standard, in full.
Washington County, Products
Testing and mitigation products
Whatever the figures for Washington County show, only a test tells you about one home.
Testing
- Short-term test kitsPassive detectors exposed for a few days under closed-building conditions, then analyzed by a lab.
- Long-term test kitsDetectors exposed for more than 90 days, for a closer picture of the annual average.
- Continuous monitorsPowered devices that log radon on a repeating cycle, often used for transaction tests.
- Digital detectorsConsumer devices that display a running radon reading without a lab.
- Water radon testsKits for radon dissolved in well water, analyzed by a lab.
Mitigation
- Mitigation fansThe inline fan that keeps a soil depressurization system running, sized by the installer.
- System indicatorsU-tube manometers and fan alarms that show whether a mitigation system is still working.
- Sealing materialsCrack, joint and sump sealing used alongside a mitigation system, not instead of one.
Washington County / Next steps
What to do next
Learn
Know what radon is
What radon is, how it gets indoors, and why a county zone is not a reading for your home.
Learn about radonTest
Test the building you live in
Short-term or long-term, where the device goes, and closed-house conditions.
How to testFix
Bring a high level down
How a mitigation system works, and the retest that confirms it.
How mitigation worksFind a pro
Hire a certified professional
Measurement and mitigation professionals by state, with their certifications.
Find a professional
Informational. Follow EPA guidance. EPA says all radon tests should be taken for a minimum of 48 hours, with windows and doors closed from 12 hours before a short-term test.