Test results in St. Clair County
| Result | Share | EPA guidance |
|---|---|---|
| Below 2 pCi/L | 27% | Below EPA's levels |
| 2 to 4 pCi/L | 29% | Consider fixing |
| 4 pCi/L or more | 44% | EPA recommends fixing |
What the data shows
- Higher share of high results than 59 of 102 Illinois counties.
- Highest of 7 neighbouring counties.
- 73% of results at or above 2 pCi/L.
- EPA's 1993 map: Zone 2, an average between 2 and 4 pCi/L. Measured average: 4.9 pCi/L.
- 24.0 tests per 1,000 homes (Illinois: 20.0).
- Median result 3.5 pCi/L: between the 2 and 4 pCi/L EPA levels.
How St. Clair County compares
Data table
| Area | Tests ≥ 4 pCi/L | Tests |
|---|---|---|
| St. Clair County | 44% | 2,771 |
| Monroe County | 44% | 1,021 |
| Randolph County | 40% | 134 |
| Madison County | 37% | 3,343 |
| Clinton County | 36% | 272 |
| Washington County | 27% | 132 |
| St. Louis County, Missouri | 26% | 17,747 |
| St. Louis city, Missouri | 17% | 1,873 |
| Illinois (102 counties) | 43% | 108,909 |
Same source as St. Clair County.
What it means for your home
About 1 in 2 results in St. Clair 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 →
About this data
Source: Radon test results from laboratories (CDC Environmental Public Health Tracking Network). Period: 2008–2017. Tests: 2,771. 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