Radon levels in Wisconsin: Moderate
The model predicts a population-weighted basement average of 2.0 pCi/L (model estimate) across Wisconsin's 72 counties - close to the US average of 1.8 pCi/L. Above-ground floors average 1.4 pCi/L.
Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. Measured state test results are shown separately below, labeled with their source and years. How the numbers work.
28 / 72
EPA Zone 1 counties (39%)
44 / 0
Zone 2 / Zone 3 counties
0
counties predicted ≥ 4 pCi/L
28.8%
of measured tests ≥ 4 pCi/L (1995-2016)
Test Wisconsin - the EPA says "consider fixing" in this range
The predicted basement average here is 2.0 pCi/L, in the 2-4 pCi/L band where the EPA recommends considering mitigation. Plenty of individual homes in a moderate area test above 4. Start with a short-term test; if it comes back at 2 or higher, follow up with a long-term test or a continuous monitor.
Monitor link goes to the Airthings store - use code RADONGRADE-10OFF at checkout for 10% off any Airthings monitor.
Already tested at 4 pCi/L or higher? Find a certified mitigation professional (EPA). A mitigation system typically runs $800-$2,500 installed.
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What the data says about radon in Wisconsin
According to the EPA zone map, 28 of Wisconsin's 72 counties are EPA Zone 1 (39%), 44 are Zone 2 and 0 are Zone 3. Zone 2 (predicted screening average of 2-4 pCi/L) is the most common designation, with the 28 Zone 1 counties marking where the EPA expected the highest potential. Treat the map as a coarse prior: it predates two decades of test data and never replaces a test in your own home.
The 2001-2021 national model predicts a population-weighted basement average of 2.0 pCi/L for Wisconsin (moderate range, close to the US average of 1.8). Of the 72 counties with predictions, 0 are predicted at or above 4 pCi/L, 52 in the 2-4 band and 20 below 2. The highest predicted county is Lafayette County at 3.4 pCi/L; the lowest is Milwaukee County at 1.3 - a 2.2 pCi/L spread that means a statewide average tells you little about any one county.
69.3% of the state's modeled ZIP codes are predicted at or above 2 pCi/L, and 0.1% at or above the 4 pCi/L action level - below the national 4.2% at the action level but above the national 48.7% at 2 pCi/L. With more than half of ZIPs above 2, a test is worth doing before any purchase or renovation here.
Measured data exists for Wisconsin: Wisconsin Department of Health Services publishes 1995-2016 results for 72 counties (102,698 tests). Weighted by test count, the measured mean is 5.3 pCi/L and 28.8% of results are at or above 4 pCi/L. The county with the largest share of elevated results is Marathon County (67%); the smallest is Iron County (-862.8%). In 60 of the 72 counties with both figures, the measured mean is higher than the model's long-term basement estimate - expected, because state tests are voluntary and skew toward basements and homeowners who suspected a problem. Each county page shows both side by side.
Wisconsin counties by predicted radon
Sorted highest to lowest predicted basement average (model estimate). 72 counties. The “Measured ≥ 4” column is the share of Wisconsin Department of Health Services test results at or above 4 pCi/L, 1995-2016.
| County | Predicted basement | Upstairs | Grade | EPA zone | Measured ≥ 4 | ZIPs |
|---|---|---|---|---|---|---|
| Lafayette County | 3.4 pCi/L | 2.2 | Moderate | EPA Zone 1 | 57.7% | 8 |
| Marathon County | 3.4 pCi/L | 2.1 | Moderate | EPA Zone 1 | 67% | 15 |
| Grant County | 3.3 pCi/L | 2.2 | Moderate | EPA Zone 1 | 61.6% | 18 |
| Vernon County | 3.0 pCi/L | 2.1 | Moderate | EPA Zone 1 | 60.2% | 10 |
| Green County | 3.0 pCi/L | 2.1 | Moderate | EPA Zone 1 | -175.2% | 7 |
| Langlade County | 3.0 pCi/L | 2.3 | Moderate | EPA Zone 1 | -96.2% | 8 |
| Iowa County | 3.0 pCi/L | 2.1 | Moderate | EPA Zone 1 | -87.4% | 11 |
| Crawford County | 3.0 pCi/L | 1.9 | Moderate | EPA Zone 1 | -321.1% | 7 |
| Pierce County | 2.8 pCi/L | 2.0 | Moderate | EPA Zone 1 | 52% | 10 |
| Portage County | 2.8 pCi/L | 1.8 | Moderate | EPA Zone 1 | 60.4% | 10 |
| Dodge County | 2.8 pCi/L | 2.1 | Moderate | EPA Zone 1 | 61.1% | 16 |
| Buffalo County | 2.7 pCi/L | 1.6 | Moderate | EPA Zone 1 | 51.1% | 5 |
| Chippewa County | 2.7 pCi/L | 1.4 | Moderate | EPA Zone 2 | 53.8% | 9 |
| Fond du Lac County | 2.7 pCi/L | 1.8 | Moderate | EPA Zone 1 | 55.7% | 14 |
| Lincoln County | 2.7 pCi/L | 1.4 | Moderate | EPA Zone 2 | 43.5% | 4 |
| Waupaca County | 2.7 pCi/L | 1.7 | Moderate | EPA Zone 1 | 59% | 9 |
| Green Lake County | 2.6 pCi/L | 1.8 | Moderate | EPA Zone 1 | -672.6% | 5 |
| Richland County | 2.6 pCi/L | 1.7 | Moderate | EPA Zone 1 | 39.2% | 5 |
| Pepin County | 2.6 pCi/L | 1.6 | Moderate | EPA Zone 1 | 46.2% | 4 |
| St. Croix County | 2.6 pCi/L | 1.9 | Moderate | EPA Zone 1 | 54.2% | 11 |
| Rock County | 2.6 pCi/L | 1.8 | Moderate | EPA Zone 1 | 5.5% | 11 |
| Menominee County | 2.6 pCi/L | 2.0 | Moderate | EPA Zone 1 | 52.8% | 2 |
| Trempealeau County | 2.6 pCi/L | 1.6 | Moderate | EPA Zone 2 | -153.2% | 10 |
| Winnebago County | 2.5 pCi/L | 1.3 | Moderate | EPA Zone 2 | 53.5% | 8 |
| Florence County | 2.5 pCi/L | 1.4 | Moderate | EPA Zone 2 | 52% | 2 |
| Walworth County | 2.5 pCi/L | 1.9 | Moderate | EPA Zone 1 | 59.2% | 11 |
| Calumet County | 2.4 pCi/L | 1.5 | Moderate | EPA Zone 2 | 52.4% | 7 |
| Barron County | 2.4 pCi/L | 1.3 | Moderate | EPA Zone 2 | -295.7% | 10 |
| Clark County | 2.3 pCi/L | 1.4 | Moderate | EPA Zone 2 | 30.7% | 14 |
| Outagamie County | 2.3 pCi/L | 1.3 | Moderate | EPA Zone 2 | 49.8% | 13 |
| Columbia County | 2.3 pCi/L | 1.5 | Moderate | EPA Zone 2 | 43.4% | 10 |
| Eau Claire County | 2.3 pCi/L | 1.3 | Moderate | EPA Zone 2 | 40.9% | 7 |
| Wood County | 2.3 pCi/L | 1.7 | Moderate | EPA Zone 1 | -24.4% | 12 |
| Door County | 2.3 pCi/L | 1.5 | Moderate | EPA Zone 1 | 51.3% | 9 |
| Taylor County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | -264.1% | 7 |
| Polk County | 2.2 pCi/L | 1.3 | Moderate | EPA Zone 2 | 41% | 14 |
| Shawano County | 2.2 pCi/L | 1.5 | Moderate | EPA Zone 1 | 50% | 12 |
| La Crosse County | 2.2 pCi/L | 1.4 | Moderate | EPA Zone 2 | 38.7% | 9 |
| Waushara County | 2.2 pCi/L | 1.1 | Moderate | EPA Zone 2 | 35.6% | 10 |
| Oneida County | 2.2 pCi/L | 1.2 | Moderate | EPA Zone 2 | 31.3% | 8 |
| Jefferson County | 2.2 pCi/L | 1.8 | Moderate | EPA Zone 1 | 47.4% | 10 |
| Rusk County | 2.2 pCi/L | 1.2 | Moderate | EPA Zone 2 | 37.5% | 7 |
| Forest County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 34.1% | 7 |
| Juneau County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | -183.2% | 7 |
| Vilas County | 2.1 pCi/L | 1.1 | Moderate | EPA Zone 2 | -78.7% | 11 |
| Price County | 2.1 pCi/L | 1.3 | Moderate | EPA Zone 2 | 36.7% | 8 |
| Washburn County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 38.2% | 7 |
| Jackson County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 35.5% | 6 |
| Kenosha County | 2.1 pCi/L | 1.2 | Moderate | EPA Zone 2 | 50.1% | 10 |
| Adams County | 2.0 pCi/L | 1.1 | Moderate | EPA Zone 2 | -354.3% | 6 |
| Monroe County | 2.0 pCi/L | 1.2 | Moderate | EPA Zone 2 | 28% | 7 |
| Sauk County | 2.0 pCi/L | 1.3 | Moderate | EPA Zone 2 | 39.7% | 12 |
| Dunn County | 2.0 pCi/L | 1.2 | Low | EPA Zone 2 | -62.5% | 9 |
| Washington County | 2.0 pCi/L | 1.7 | Low | EPA Zone 1 | 58.4% | 11 |
| Brown County | 2.0 pCi/L | 1.1 | Low | EPA Zone 2 | 51.7% | 13 |
| Oconto County | 1.9 pCi/L | 1.2 | Low | EPA Zone 2 | 39.3% | 12 |
| Marquette County | 1.9 pCi/L | 1.0 | Low | EPA Zone 2 | 17% | 6 |
| Racine County | 1.9 pCi/L | 1.2 | Low | EPA Zone 2 | 57.2% | 12 |
| Kewaunee County | 1.9 pCi/L | 1.1 | Low | EPA Zone 2 | 55% | 4 |
| Burnett County | 1.8 pCi/L | 1.1 | Low | EPA Zone 2 | -458.3% | 6 |
| Iron County | 1.8 pCi/L | 1.0 | Low | EPA Zone 2 | -862.8% | 7 |
| Sawyer County | 1.8 pCi/L | 1.2 | Low | EPA Zone 2 | -262.1% | 7 |
| Dane County | 1.8 pCi/L | 1.4 | Low | EPA Zone 1 | 50.9% | 32 |
| Bayfield County | 1.8 pCi/L | 1.1 | Low | EPA Zone 2 | 28.2% | 10 |
| Marinette County | 1.6 pCi/L | 1.1 | Low | EPA Zone 2 | 25.4% | 12 |
| Manitowoc County | 1.6 pCi/L | 1.1 | Low | EPA Zone 2 | 35.7% | 10 |
| Waukesha County | 1.6 pCi/L | 1.4 | Low | EPA Zone 1 | 62% | 25 |
| Ashland County | 1.5 pCi/L | 1.0 | Low | EPA Zone 2 | -372.2% | 8 |
| Ozaukee County | 1.5 pCi/L | 1.2 | Low | EPA Zone 2 | 49.5% | 8 |
| Douglas County | 1.5 pCi/L | 0.9 | Low | EPA Zone 2 | 22.1% | 9 |
| Sheboygan County | 1.5 pCi/L | 1.0 | Low | EPA Zone 2 | 55.1% | 13 |
| Milwaukee County | 1.3 pCi/L | 0.8 | Low | EPA Zone 2 | 48.9% | 35 |
Radon levels in Wisconsin cities
The 15 most-populous Wisconsin places among the 1,000 largest US cities (Census incorporated places and CDPs), by population. City figures are ZIP-land-weighted means of the model's ZIP predictions (model estimate).
| City | Population | Predicted basement | Upstairs | Grade | ZIPs ≥ 4 |
|---|---|---|---|---|---|
| Milwaukee | 561,385 | 1.2 pCi/L | 0.8 | Low | 0% |
| Madison | 280,305 | 1.6 pCi/L | 1.3 | Low | 0% |
| Green Bay | 105,744 | 1.9 pCi/L | 1.1 | Low | 0% |
| Kenosha | 98,211 | 2.0 pCi/L | 1.1 | Moderate | 0% |
| Racine | 76,602 | 1.7 pCi/L | 1.0 | Low | 0% |
| Appleton | 74,719 | 2.3 pCi/L | 1.3 | Moderate | 0% |
| Eau Claire | 70,542 | 2.4 pCi/L | 1.3 | Moderate | 0% |
| Waukesha | 70,446 | 1.4 pCi/L | 1.4 | Low | 0% |
| Oshkosh | 66,184 | 2.5 pCi/L | 1.4 | Moderate | 0% |
| Janesville | 66,102 | 2.5 pCi/L | 1.7 | Moderate | 0% |
| West Allis | 58,874 | 1.2 pCi/L | 0.8 | Low | 0% |
| La Crosse | 51,327 | 2.1 pCi/L | 1.5 | Moderate | 0% |
| Sheboygan | 49,686 | 1.2 pCi/L | 0.8 | Low | 0% |
| Wauwatosa | 47,038 | 1.4 pCi/L | 1.0 | Low | 0% |
| Fond du Lac | 44,300 | 2.7 pCi/L | 1.7 | Moderate | 0% |
Highest-radon ZIP codes in Wisconsin
The 10 Wisconsin ZIP codes with the highest predicted basement average (model estimate), out of 719 modeled. A ZIP average is still an area figure - neighboring homes routinely test several pCi/L apart.
| ZIP | County | Predicted basement | Upstairs | Grade |
|---|---|---|---|---|
| 54448 | Marathon County | 4.9 pCi/L | 2.8 | High |
| 53813 | Grant County | 4.0 pCi/L | 2.5 | Moderate |
| 54619 | Monroe County | 3.7 pCi/L | 2.5 | Moderate |
| 54484 | Marathon County | 3.7 pCi/L | 2.2 | Moderate |
| 54623 | La Crosse County | 3.7 pCi/L | 2.4 | Moderate |
| 53554 | Grant County | 3.7 pCi/L | 2.4 | Moderate |
| 53806 | Grant County | 3.6 pCi/L | 2.4 | Moderate |
| 54440 | Marathon County | 3.6 pCi/L | 2.3 | Moderate |
| 54455 | Marathon County | 3.6 pCi/L | 2.7 | Moderate |
| 54403 | Marathon County | 3.6 pCi/L | 2.5 | Moderate |
Wisconsin radon questions
- Is radon high in Wisconsin?
- Wisconsin's population-weighted predicted basement average is 2.0 pCi/L, close to the US average of 1.8. 0 of its 72 modeled counties are predicted at or above the EPA action level of 4 pCi/L, 52 are in the 2-4 "consider fixing" range and 20 are below 2. 0.1% of Wisconsin ZIP codes are predicted at 4 or higher.
- Which Wisconsin county has the highest radon?
- Lafayette County has the highest predicted basement average in Wisconsin at 3.4 pCi/L (EPA Zone 1). The lowest is Milwaukee County at 1.3 pCi/L. In measured state test data (1995-2016), Marathon County has the largest share of results at or above 4 pCi/L (67%). These are area figures; individual homes in any county can test far higher.
- How many EPA Zone 1 counties are in Wisconsin?
- 28 of Wisconsin's 72 counties (39%) are EPA Zone 1 (highest potential), 44 are Zone 2 and 0 are Zone 3. The EPA zone map dates from 1993; the predicted values on this page come from a 2001-2021 model built on millions of actual tests, so the two can disagree for a given county.
- Should I test for radon in Wisconsin?
- Yes - with some urgency. Wisconsin's predicted average is in the moderate range, and 69.3% of its ZIP codes are predicted at 2 pCi/L or higher. A short-term charcoal kit or a continuous digital monitor will tell you your actual level within days.
- What do actual radon tests show in Wisconsin?
- Wisconsin Department of Health Services publishes 1995-2016 test results for 72 Wisconsin counties (102,698 tests). Weighted by test count, the measured mean is 5.3 pCi/L and 28.8% of results are at or above 4 pCi/L. The measured mean is higher than the model's long-term basement estimate in 60 of 72 comparable counties; state tests are voluntary and skew toward basements and homes where radon was suspected, while the model estimates the average across all homes.
Wisconsin radon program
Wisconsin's radon program page is at www.dhs.wisconsin.gov; it lists testing and certified-mitigator guidance for the state. The EPA also keeps a directory of every state radon contact: EPA state radon contacts page. Then read how to test and what mitigation costs.