Test results in Jefferson County
| Result | Share | EPA guidance |
|---|---|---|
| Below 2 pCi/L | 38% | Below EPA's levels |
| 2 to 4 pCi/L | 23% | Consider fixing |
| 4 pCi/L or more | 39% | EPA recommends fixing |
What the data shows
- Higher share of high results than 34 of 72 Wisconsin counties.
- Below the Wisconsin rate of 42%.
- Higher than 1 of 5 neighbouring counties.
- 62% of results at or above 2 pCi/L.
- 58.5 tests per 1,000 homes (Wisconsin: 70.0).
- Median result 2.9 pCi/L: between the 2 and 4 pCi/L EPA levels.
How Jefferson County compares
Data table
| Area | Tests ≥ 4 pCi/L | Tests |
|---|---|---|
| Dodge County | 54% | 2,208 |
| Rock County | 49% | 4,112 |
| Walworth County | 49% | 3,690 |
| Waukesha County | 46% | 23,315 |
| Jefferson County | 39% | 2,157 |
| Dane County | 38% | 18,790 |
| Wisconsin (72 counties) | 42% | 194,443 |
Same source as Jefferson County.
What it means for your home
About 1 in 3 results in Jefferson County were at or above 4 pCi/L, where the EPA recommends a fix. Only a test shows your own home's level.
Levels in pCi/L from the EPA. The WHO reference level is 100 Bq/m³, about 2.7 pCi/L.
Test your home
Start with a short-term test (2–90 days) and confirm a result of 4 pCi/L or more with a second test. EPA guide
Sponsored: we earn a commission on purchases through these links. We haven't tested Airthings monitors yet.
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Fixing high radon
No local job records yet. National range: $800–$2,500, average $1,200 (EPA, 2003). Cost guide →
Wisconsin doesn't license radon mitigators; look for NRPP or NRSB certification. Source
Buying or selling here
Wisconsin sellers must tell buyers about any known unsafe radon levels through the Real Estate Condition Report (Wis. Stat. § 709.03). Source
Checked against the official text on 2026-11-03. Not legal advice.
About this data
Source: Wisconsin county radon test results (Wisconsin Department of Health Services). Period: 2005–2017. Tests: 2,157. Read the methodology →
These are voluntary and real-estate tests, not a random sample of homes, so they describe tested homes rather than every home.
About this page
Published by Ray Roman, editor of Radon by County. Figures are loaded from the cited source and spot-checked against it. Editorial policy · About us