Short-term kit
PicoCan short-term charcoal canister radon test
- Lab fee included
Method: Charcoal
In home: 48 to 96 hours
Locations and reports
Radon Levels in St. Clair County, Missouri
EPA puts St. Clair County in Zone 2, its middle radon zone, and only 2 radon tests from it are on file with CDC (2022). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
38.3%
Henry County
- Henry
- 38.3%
- Vernon
- 8.8%
4 of 7 neighbours have 30+ tests, 2008 to 2017
Nearest county
38.3%
Henry County, 24 miles
- Henry
- 38.3%
- Missouri
- 30.6%
Share at 4+ pCi/L, 81 tests, 2008 to 2017
Ground above low
100.0%
5.8 pts above Missouri
- St. Clair
- 100.0%
- Missouri
- 94.2%
Share of land USGS rates moderate or high potential
Tests reported
13
Too few for a share
- St. Clair
- 13
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for St. Clair County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The data
St. Clair County, At a glance
St. Clair County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
St. Clair County is a
USGS geologic potential: Moderate across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Clair County, 2022
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 0.0% |
| 2015 | 0.0% |
| 2017 | 0.0% |
| 2018 | 100.0% |
| 2020 | 0.0% |
| 2021 | 33.3% |
| 2022 | 0.0% |
2022: 0.0%. Across these years the share ran from 0.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 2 tests were reported to CDC for St. Clair County over 2022, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2022. Measured data period: 2005 to 2022 (every CDC figure on file).
St. Clair County, Compared
St. Clair County radon figures, compared
Calculated by Radon411CDC's largest figure for St. Clair County rests on 13 tests over the 2008 to 2017 laboratory totals, 1 of them at or above 4 pCi/L, so each test moves its share by 7.7 points and no rank or comparison is drawn from it. Results reached as high as 5.6 pCi/L, with a middle value of 1.5 pCi/L.
Of the counties bordering it, 4 have a figure over the 2008 to 2017 laboratory totals: Henry County reported the largest share at or above 4 pCi/L, 38.3%, and Vernon County the smallest, 8.8%, with Benton County at 30.6% and Polk County at 11.5% between. Farther out, Johnson County (49 miles away) at 25.8%, Cass County (53 miles away) at 45.5% and Pettis County (55 miles away) at 37.9% have figures too. Pooled across 115 Missouri counties, 30.6% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Atchison County reported the highest share (69.9%) and Vernon County the lowest (8.8%). EPA's 1993 map puts St. Clair County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Clair County, Geology
The ground under St. Clair County
PredictedUSGS's geologic map puts all of St. Clair County's mapped land in one class: moderate radon potential. The map puts 56.6% of St. Clair County in the area it calls Osage Plains and 35.9% in Springfield Plateau, with one smaller area beside them. USGS gives both a radon index of 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Osage Plains | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 56.6% |
| Springfield Plateau | Mississippian limestone, shale, and sandstone. | Moderate | 11 | 35.9% |
| Salem Plateau | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 7.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Clair County beside the ground around it
Across Missouri 8.2% of the land is rated high; none of St. Clair County's is. Of the 7 counties that border it, 1 has more high-potential ground, Bates County the most at 0.3%.
The map rates the ground, not the air in any home.
Local help
St. Clair County, Local resources
Radon testing and mitigation in St. Clair County
- Missouri Radon ProgramMissouri Radon Program, run by Missouri Department of Health and Senior Services, offers free or discounted test kits, and answers questions about testing and mitigation in Missouri.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Free radon test kits are available for Missouri residents (limit one per household).
- Compare kits
- Professionals in Missouri27 professionals are listed in Missouri.
What Missouri's program says
- Phone
- 573-751-6102
- radon@health.mo.gov
What it means
St. Clair County, Questions
Questions about radon in St. Clair County
Are radon levels high in St. Clair County?
In 2022, 0.0% of the radon tests reported to CDC for St. Clair County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.1 pCi/L. Of the counties bordering it, 4 have a figure over the 2008 to 2017 laboratory totals: Henry County reported the largest share at or above 4 pCi/L, 38.3%, and Vernon County the smallest, 8.8%, with Benton County at 30.6% and Polk County at 11.5% between.
Which counties border St. Clair County?
St. Clair County borders 7 counties: Cedar County, Henry County, Hickory County, Polk County, Vernon County, Benton County and Bates County.
Products
St. Clair County, Products
Testing a home in St. Clair County
No CDC figure names St. Clair County; the nearest county with one, Henry County (24 miles away), reported 38.3% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in St. Clair County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Monitor
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
St. Clair County, Bordering counties
Counties bordering St. Clair County
Calculated by Radon411- Radon levels in Henry CountyEPA zone 2
38.3%at or above 4 pCi/L
Median 3.4 pCi/L · 81 tests
- Radon levels in Benton CountyEPA zone 2
30.6%at or above 4 pCi/L
Median 2.0 pCi/L · 49 tests
- Radon levels in Bates CountyEPA zone 2
26.1%at or above 4 pCi/L
Median 1.5 pCi/L · 23 tests
- Radon levels in Polk CountyEPA zone 2
11.5%at or above 4 pCi/L
Median 1.6 pCi/L · 78 tests
- Radon levels in Vernon CountyEPA zone 2
8.8%at or above 4 pCi/L
Median 0.9 pCi/L · 34 tests
- Radon levels in Cedar CountyEPA zone 2
5.0%at or above 4 pCi/L
Median 1.3 pCi/L · 20 tests
- Radon levels in Hickory CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 2.0 pCi/L · 9 tests
St. Clair County, Cities and towns
Cities and towns in St. Clair County
St. Clair County is growing: the Census Bureau puts it at 9,976 residents on July 1, 2025, up 6.7% from 9,350 in 2020. That works out to 15 people per square mile of land. No town dominates: Appleton City, the largest, has 1,096 residents, 11.0% of the total. Together its 7 incorporated places hold 30.5% of those residents; the other 69.5% live outside any of them. Reported testing is thin here: 13 tests over 2008 to 2017, or 1.3 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.
From Appleton City to Gerster, CDC publishes no figure by town: each reads St. Clair County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Appleton City | 1,096 | +5.9% | 11.0% |
| Osceola | 1,012 | +8.2% | 10.1% |
| Lowry City | 657 | +6.3% | 6.6% |
| Collins | 134 | +6.3% | 1.3% |
| Roscoe | 93 | +5.7% | 0.9% |
| Vista | 37 | +5.7% | 0.4% |
| Gerster | 16 | +6.7% | 0.2% |
7 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
St. Clair County, Homes
Homes in St. Clair County
Of St. Clair County's 5,295 homes, 73% are detached houses, against 70% across Missouri; 21% are mobile homes. Half of its homes were built before 1977, close to Missouri's 1978: 26% date from before 1960 and 17% from 2000 or later. Owners live in 76% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.
| Homes | St. Clair County | Missouri |
|---|---|---|
| Housing units | 5,295 | 2,809,501 |
| Detached houses | 73% | 70% |
| In buildings of 5 or more | 2% | 13% |
| Mobile homes | 21% | 5% |
| Built before 1960 | 26% | 28% |
| Built since 2000 | 17% | 21% |
| Middle year built | 1977 | 1978 |
| Owner-occupied | 76% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.