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Radon Levels in Shelby County, Illinois

EPA puts Shelby County in Zone 2, its middle radon zone, and only 21 radon tests from it are on file with CDC (2017). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    56.6%

    13.5 pts above IL

    Shelby
    56.6%
    Illinois
    43.1%

    113 tests, 2008 to 2017

  • Median result

    4.4pCi/L

    Action level reached

    Shelby
    4.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    113

    69th of 93 by tests

    Shelby
    113
    Cook
    14,199

    Reported to CDC before any fix, 2008 to 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

    21 of 93

    Top quarter

    Shelby
    56.6%
    Stark
    80.5%

    By share, of 93 with 30+ tests

Read a result for Shelby County

Starts at Shelby County's median, 4.4 pCi/L

4.4pCi/L

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

EPA’s reading of 4.4 pCi/L

At or above 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Shelby County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Shelby County, At a glance

Shelby County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Shelby 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 55% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Shelby County, 2017

Share of reported tests at or above 4 pCi/L, by year, Shelby County
Share of reported tests at or above 4 pCi/L, by year, Shelby County
YearShare of reported tests at or above 4 pCi/L
201440.0%
2015100.0%
201771.4%

2017: 71.4%. Across these years the share ran from 40.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 21 tests were reported to CDC for Shelby County over 2017, 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: 2017. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Shelby County, Compared

Shelby County radon figures, compared

Calculated by Radon411

More than half: 56.6% of the 113 radon tests reported to CDC for Shelby County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 21st of 93 Illinois counties with 30 or more tests for the same period. That is 13.5 points above the 43.1% pooled from 102 Illinois counties.

The newest figure, in 2017, counts only 21 tests (71.4% at or above 4 pCi/L), too few to compare, so this reading uses the 113-test figure.

The median result, 4.4 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 33.8 pCi/L. The rest split 22.1% under 2 pCi/L and 21.2% from 2 to 4 (Illinois: 31.6% and 25.3%). The reported tests do not follow EPA's Zone 2 label for Shelby County (predicted average between 2 and 4 pCi/L): 56.6% of them reached 4 pCi/L, fewer than that label suggests.

No bordering county with a figure for the same period reported a higher share; the closest is Moultrie County at 47.8%, the lowest Cumberland County at 21.8%. Statewide for the same period, Stark County reported the highest share (80.5%) and Williamson County the lowest (13.3%).

The busiest year on file was 2014, with 60 tests reported; the quietest, 2015, had 3.

Nationally, every county with a figure for the same period pools to 35.7%; Shelby County sits 20.9 points above it.

Shelby County against Illinois, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Shelby County
Shelby County11356.6%4.4 pCi/LThis county
Illinois, pooled102 counties, pooled108,90943.1%Not pooled−13.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−20.9 points
Stark Countyhighest in the state8780.5%7.4 pCi/L+23.9 points
Williamson Countylowest in the state60113.3%1.3 pCi/L−43.3 points
Moultrie County, ILborders it6947.8%3.8 pCi/L−8.8 points
Christian County, ILborders it23146.3%3.7 pCi/L−10.3 points
Macon County, ILborders it74444.5%3.4 pCi/L−12.1 points
Coles County, ILborders it29538.6%3.1 pCi/L−18.0 points
Effingham County, ILborders it76337.9%3.0 pCi/L−18.7 points
Montgomery County, ILborders it23636.9%2.8 pCi/L−19.7 points
Fayette County, ILborders it13333.1%2.7 pCi/L−23.5 points
Cumberland County, ILborders it5521.8%1.8 pCi/L−34.8 points
Where Shelby County's reported results fell, 2008 to 2017, laboratory, beside Illinois and the United States
ResultShelby County testsShelby County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L2522.1%31.6%39.6%−9.5 points
2 to 4 pCi/L2421.2%25.3%24.7%−4.1 points
4 pCi/L and above6456.6%43.1%35.7%+13.5 points
Shelby County ranked among the 93 Illinois counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
De Witt County16 of 9314260.6%4.8 pCi/L
Henry County17 of 931,37660.4%4.9 pCi/L
Tazewell County18 of 935,01059.6%5.1 pCi/L
Bureau County19 of 9329257.5%4.6 pCi/L
Jo Daviess County20 of 9398557.2%4.6 pCi/L
Shelby County21 of 9311356.6%4.4 pCi/L
Adams County22 of 933,67755.2%4.5 pCi/L
McDonough County23 of 9372054.4%4.5 pCi/L
McLean County24 of 934,69352.8%4.3 pCi/L
Sangamon County25 of 932,96252.2%4.2 pCi/L
Piatt County26 of 9359051.7%4.0 pCi/L
Shelby County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20172171.4%5.2 pCi/L7.3 pCi/L33.7%−28.6 points
20153100.0%4.5 pCi/L4.5 pCi/L36.6%+60.0 points
20146040.0%2.5 pCi/L24.5 pCi/L37.8%First on file

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

Shelby County, Geology

The ground under Shelby County

Predicted

USGS's geologic map splits Shelby County: 54.9% of its land is moderate radon potential and 45.1% high. The map puts 54.9% of Shelby County in the area it calls Southern Central Lowland Province and 38.2% in Bloomington Ridged Plain, with one smaller area beside them. USGS gives the first a radon index of 9, in the moderate band (9 to 11), and the second 13, in the high band (12 to 17).

USGS's geologic areas under Shelby County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Southern Central Lowland ProvinceIllinoian glacial deposits, sandstone, and gray shale.Moderate954.9%
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High1338.2%
Galesburg PlainIllinoian glacial deposits and loess over Paleozoic sedimentary rocks.High137.0%

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

Shelby County beside the ground around it

Illinois as a whole has more high-potential ground than Shelby County: 64.5% of its land, against 45.1% here. Of the 8 counties that border it, 4 have more high-potential ground, Macon County the most at 100%.

Share of land by USGS radon potential: Shelby County, the 8 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Shelby CountyZone 2None54.9%45.1%
Moultrie CountyZone 1NoneNone100%
Effingham CountyZone 2None100%None
Cumberland CountyZone 2None94.7%5.3%
Coles CountyZone 1None1.9%98.1%
Christian CountyZone 2None16.9%83.1%
Macon CountyZone 1NoneNone100%
Fayette CountyZone 2None100%None
Montgomery CountyZone 2None88.8%11.2%
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

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

Local help

Shelby County, Local resources

Radon testing and mitigation in Shelby 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

Shelby County, Questions

Questions about radon in Shelby County

Are radon levels high in Shelby County?

In 2017, 71.4% of the radon tests reported to CDC for Shelby County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.2 pCi/L. Of 93 Illinois counties with 30 or more tests for the same period, 20 reported a higher share; pooled, the state comes to 43.1%.

Which counties border Shelby County?

Shelby County borders 8 counties: Moultrie County, Effingham County, Cumberland County, Coles County, Christian County, Macon County, Fayette County and Montgomery County.

Products

Shelby County, Products

Testing a home in Shelby County

In Shelby County, 56.6% of 113 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 43.1% pooled across Illinois. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Shelby County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Shelby County homes, compared

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Shelby County, Bordering counties

Counties bordering Shelby County

Calculated by Radon411

Shelby County, Cities and towns

Cities and towns in Shelby County

About 20,576 people live in Shelby County by the Census Bureau's estimate for July 1, 2025, 345 fewer than in 2020 (−1.6%). That works out to 27 people per square mile of land. Pana, the largest place on its list (5,010 residents in all), extends beyond Shelby County, so no share of the total is worked out for it. Reported testing is thin here: 113 tests over 2008 to 2017, or 5.5 for every 1,000 residents (2025 estimate), where Illinois as a whole comes to 8.6.

From Pana to Oconee, CDC publishes no figure by town: each reads Shelby County's.

The cities and towns in Shelby County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Panaextends beyond Shelby County5,010−3.2%Counted whole
Shelbyville4,537−2.2%22.0%
Moweaquaextends beyond Shelby County1,735−1.2%Counted whole
Windsor1,035−3.0%5.0%
Stewardson716−0.4%3.5%
Findlay658−1.8%3.2%
Strasburg518−2.8%2.5%
Cowden497−3.3%2.4%
Tower Hill473−1.7%2.3%
Herrick354−1.1%1.7%
Sigel319−1.2%1.6%
Oconee133−2.2%0.6%

12 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). A place that extends beyond Shelby County is counted whole, so it has no share.

Shelby County, Homes

Homes in Shelby County

Shelby County is a place of houses on their own lots: 85% of its 10,054 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1965, close to Illinois' 1970: 46% date from before 1960 and 12% 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 Shelby County, Illinois, 2019 to 2023
HomesShelby CountyIllinois
Housing units10,0545,443,501
Detached houses85%58%
In buildings of 5 or more4%22%
Mobile homes7%2%
Built before 196046%38%
Built since 200012%16%
Middle year built19651970
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.