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Radon Levels in Clinton County, Illinois

EPA puts Clinton County in Zone 2, its middle radon zone, and 37.6% of its 582 reported radon tests (2017) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    37.6%

    3.9 pts above IL

    Clinton
    37.6%
    Illinois
    33.7%

    582 tests, 2017

  • Median result

    3.0pCi/L

    Below action level

    Clinton
    3.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    582

    25th of 70 by tests

    Clinton
    582
    Cook
    26,937

    Reported to CDC before any fix, 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Illinois

    46 of 70

    Middle half

    Clinton
    37.6%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Clinton County

Starts at Clinton County's median, 3.0 pCi/L

3.0pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 3.0 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Clinton County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Clinton County, At a glance

Clinton County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Clinton County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

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 Clinton County, 2017

Share of reported tests at or above 4 pCi/L, by year, Clinton County
Share of reported tests at or above 4 pCi/L, by year, Clinton County
YearShare of reported tests at or above 4 pCi/L
201422.6%
201534.5%
2016100.0%
201737.6%

2017: 37.6%. Across these years the share ran from 22.6% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 582 tests reported to CDC for Clinton County over 2017, many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Clinton County, Compared

Clinton County radon figures, compared

Calculated by Radon411

In Clinton County, about 4 in 10 reported tests in 2017 (219 of 582) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 5.9 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Clinton County runs 3.9 points above its state.

Of 6 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 11.8% (Washington County) to 33.7% (St. Clair County). By share, Clinton County is 46th of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 22.6% and 2017 closed at 37.6% (up 15.0 points), with 2017 the high at 37.6%. Half the tests came in under 3.0 pCi/L and half over it; the single highest reached 38.9 pCi/L. Below the action level, 174 tests (29.9%) came in under 2 pCi/L, against 37.7% statewide, and 189 tests (32.5%) fell between 2 and 4, against 28.6% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 37.6% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.

The busiest year on file was 2017, with 582 tests reported; the quietest, 2016, had 3.

Share of reported tests at or above 4 pCi/L by year, Clinton County against Illinois2014 to 2017, years with 30 or more tests: Clinton County 22.6% to 37.6%, the state's pooled share 33.7% in 2017.
Clinton CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Clinton County against Illinois: data table
YearTestsClinton County, at or above 4 pCi/LIllinois, pooled
201431822.6%37.8%
201526134.5%36.6%
201758237.6%33.7%
Clinton County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Clinton County
Clinton County58237.6%3.0 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−3.9 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−5.9 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+31.6 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−29.2 points
St. Clair County, ILborders it5,19333.7%2.6 pCi/L−3.9 points
Bond County, ILborders it7532.0%2.6 pCi/L−5.6 points
Madison County, ILborders it5,21429.5%2.6 pCi/L−8.1 points
Fayette County, ILborders it5726.3%2.5 pCi/L−11.3 points
Marion County, ILborders it4520.0%1.9 pCi/L−17.6 points
Washington County, ILborders it5111.8%2.0 pCi/L−25.8 points
Where Clinton County's reported results fell, 2017, beside Illinois and the United States
ResultClinton County testsClinton County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L17429.9%37.7%43.5%−7.8 points
2 to 4 pCi/L18932.5%28.6%24.8%+3.9 points
4 pCi/L and above21937.6%33.7%31.7%+3.9 points
Clinton County ranked among the 70 Illinois counties with 30 or more tests, by share at or above 4 pCi/L, 2017
CountyRankTestsAt or above 4 pCi/LMedian
Peoria County41 of 703,81640.2%3.1 pCi/L
Will County42 of 7010,77640.0%3.1 pCi/L
Monroe County43 of 7071439.9%3.0 pCi/L
Macon County44 of 701,25138.8%3.1 pCi/L
Effingham County45 of 7014138.3%2.7 pCi/L
Clinton County46 of 7058237.6%3.0 pCi/L
Kane County47 of 708,68236.6%2.8 pCi/L
McHenry County48 of 706,47435.1%2.9 pCi/L
Randolph County49 of 706035.0%2.9 pCi/L
Kendall County50 of 703,04535.0%2.8 pCi/L
Winnebago County51 of 702,70334.9%2.9 pCi/L
Clinton County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
201758237.6%3.0 pCi/L38.9 pCi/L33.7%−62.4 points
20163100.0%7.7 pCi/L7.7 pCi/L17.4%+65.5 points
201526134.5%2.5 pCi/L21.3 pCi/L36.6%+11.9 points
201431822.6%2.6 pCi/L19.4 pCi/L37.8%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Clinton County, Geology

The ground under Clinton County

Predicted

USGS's geologic map puts all of Clinton County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Southern Central Lowland Province, to which USGS gives a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Clinton County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Southern Central Lowland ProvinceIllinoian glacial deposits, sandstone, and gray shale.Moderate9100%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Clinton County beside the ground around it

Across Illinois 64.5% of the land is rated high; none of Clinton County's is. Of the 6 counties that border it, 1 has more high-potential ground, Madison County the most at 8.3%.

Share of land by USGS radon potential: Clinton County, the 6 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Clinton CountyZone 2None100%None
Washington CountyZone 2None100%None
Bond CountyZone 2None100%None
Marion CountyZone 2None100%None
Madison CountyZone 2None91.7%8.3%
St. Clair CountyZone 2None100%None
Fayette CountyZone 2None100%None
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

The map rates the ground, not the air in any home.

Local help

Clinton County, Local resources

Radon testing and mitigation in Clinton County

What Illinois's program says
Phone
(800) 325-1245
Licensing of radon professionals
The Agency also licenses and regulates the individuals who provide radon measurement and mitigation to the public.
Disclosure when a home is sold or rented
Illinois Radon Awareness Act - This is the legislation that requires the seller to provide to the buyer of any interest in residential real property the IEMA-OHS pamphlet entitled "Radon Testing Guidelines for Real Estate Transactions" and the Illinois Disclosure of Information on Radon Hazards.

What it means

Clinton County, Questions

Questions about radon in Clinton County

Are radon levels high in Clinton County?

In 2017, 37.6% of the radon tests reported to CDC for Clinton County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.0 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 45 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Clinton County?

Clinton County borders 6 counties: Washington County, Bond County, Marion County, Madison County, St. Clair County and Fayette County.

Products

Clinton County, Products

Testing a home in Clinton County

In Clinton County, 37.6% of 582 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Clinton County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Clinton County homes, compared

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Clinton County, Bordering counties

Counties bordering Clinton County

Calculated by Radon411

Clinton County, Cities and towns

Cities and towns in Clinton County

The Census Bureau estimates 37,128 residents in Clinton County for July 1, 2025, 213 more than in 2020 (+0.6%). That works out to 78 people per square mile of land. Centralia, the largest place on its list (11,863 residents in all), extends beyond Clinton County, so no share of the total is worked out for it. CDC's 582 reported tests for 2017 work out to 15.7 per 1,000 residents (2025 estimate), close to Illinois' 10.9.

From Centralia to Huey, CDC publishes no figure by town: each reads Clinton County's.

The 12 largest cities and towns in Clinton County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Centraliaextends beyond Clinton County11,863−2.1%Counted whole
Breese4,602−1.2%12.4%
New Badenextends beyond Clinton County3,378−1.3%Counted whole
Carlyle3,188−1.7%8.6%
Trenton2,643−1.5%7.1%
Aviston2,454+4.3%6.6%
Germantown1,379+3.8%3.7%
Albers1,114−1.6%3.0%
Wamacextends beyond Clinton County962−2.2%Counted whole
Beckemeyer921Level2.5%
Bartelso644+1.7%1.7%
Damiansville562−1.1%1.5%
  • St. Rose
  • Hoffman
  • Keyesport (part)
  • Huey

16 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Clinton County is counted whole, so it has no share.

Clinton County, Homes

Homes in Clinton County

Clinton County is a place of houses on their own lots: 81% of its 15,677 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1977, close to Illinois' 1970: 28% date from before 1960 and 21% from 2000 or later. Owners live in 79% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.

Homes in Clinton County, Illinois, 2019 to 2023
HomesClinton CountyIllinois
Housing units15,6775,443,501
Detached houses81%58%
In buildings of 5 or more3%22%
Mobile homes9%2%
Built before 196028%38%
Built since 200021%16%
Middle year built19771970
Owner-occupied79%67%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.