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Radon Levels in Douglas County, Illinois

EPA puts Douglas County in Zone 1, its highest radon zone, and high results are common there: 50.0% of the 84 radon tests reported to CDC (2017) came back 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

    50.0%

    16.3 pts above IL

    Douglas
    50.0%
    Illinois
    33.7%

    84 tests, 2017

  • Median result

    3.8pCi/L

    Below action level

    Douglas
    3.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    84

    52nd of 70 by tests

    Douglas
    84
    Cook
    26,937

    Reported to CDC before any fix, 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Illinois

    21 of 70

    Middle half

    Douglas
    50.0%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Douglas County

Starts at Douglas County's median, 3.8 pCi/L

3.8pCi/L

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

EPA’s reading of 3.8 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. Douglas County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Douglas County, At a glance

Douglas County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Douglas County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Douglas County, 2017

Share of reported tests at or above 4 pCi/L, by year, Douglas County
Share of reported tests at or above 4 pCi/L, by year, Douglas County
YearShare of reported tests at or above 4 pCi/L
201453.8%
201552.6%
201750.0%

2017: 50.0%. Across these years the share ran from 50.0% to 53.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 84 tests reported to CDC for Douglas 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

Douglas County, Compared

Douglas County radon figures, compared

Calculated by Radon411

More than half: 50.0% of the 84 radon tests reported to CDC for Douglas County in 2017 read at least 4 pCi/L. That places it 21st of 70 Illinois counties with 30 or more tests for the same period. That is 16.3 points above the 33.7% pooled from 93 Illinois counties.

The median result, 3.8 pCi/L, sits between 2 and EPA's 4 pCi/L action level, and the top reported result was 9.2 pCi/L. The rest split 25.0% under 2 pCi/L and 25.0% from 2 to 4 (Illinois: 37.7% and 28.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 50.0% share point the same way here.

3 of its 5 bordering counties with figures ran higher, led by Piatt County at 54.8%; Champaign County reported 44.7%. Statewide for the same period, Stark County reported the highest share (69.2%) and Williamson County the lowest (8.4%).

The busiest year on file was 2017, with 84 tests reported; the quietest, 2015, had 57.

Over 3 years of annual figures the share fell 3.8 points, from 53.8% in 2014 to 50.0% in 2017; its peak was 53.8% in 2014. Nationally, every county with a figure for the same period pools to 31.7%; Douglas County sits 18.3 points above it.

Share of reported tests at or above 4 pCi/L by year, Douglas County against Illinois2014 to 2017, years with 30 or more tests: Douglas County 53.8% to 50.0%, the state's pooled share 33.7% in 2017.
Douglas CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Douglas County against Illinois: data table
YearTestsDouglas County, at or above 4 pCi/LIllinois, pooled
20147853.8%37.8%
20155752.6%36.6%
20178450.0%33.7%
Douglas County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Douglas County
Douglas County8450.0%3.8 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−16.3 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−18.3 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+19.2 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−41.6 points
Edgar County, ILborders it2157.1%4.5 pCi/L+7.1 points
Piatt County, ILborders it27954.8%4.3 pCi/L+4.8 points
Vermilion County, ILborders it3953.8%4.7 pCi/L+3.8 points
Coles County, ILborders it19851.5%4.2 pCi/L+1.5 points
Moultrie County, ILborders it4546.7%3.3 pCi/L−3.3 points
Champaign County, ILborders it3,15944.7%3.4 pCi/L−5.3 points
Where Douglas County's reported results fell, 2017, beside Illinois and the United States
ResultDouglas County testsDouglas County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L2125.0%37.7%43.5%−12.7 points
2 to 4 pCi/L2125.0%28.6%24.8%−3.6 points
4 pCi/L and above4250.0%33.7%31.7%+16.3 points
Douglas 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
Putnam County16 of 704553.3%4.5 pCi/L
Woodford County17 of 7076552.9%4.2 pCi/L
Ogle County18 of 7063652.4%4.1 pCi/L
Menard County19 of 7016851.8%4.3 pCi/L
Coles County20 of 7019851.5%4.2 pCi/L
Douglas County21 of 708450.0%3.8 pCi/L
Warren County21 of 704250.0%3.6 pCi/L
Marshall County23 of 708148.1%3.8 pCi/L
Boone County24 of 7052546.9%3.4 pCi/L
Moultrie County25 of 704546.7%3.3 pCi/L
Rock Island County26 of 702,28346.5%3.7 pCi/L
Douglas County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20178450.0%3.8 pCi/L9.2 pCi/L33.7%−2.6 points
20155752.6%4.0 pCi/L18.3 pCi/L36.6%−1.2 points
20147853.8%4.6 pCi/L24.5 pCi/L37.8%First on file

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

Douglas County, Geology

The ground under Douglas County

Predicted

USGS's geologic map puts all of Douglas County's mapped land in one class: high radon potential. All of it lies in the area the map calls Bloomington Ridged Plain, to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Douglas County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High13100%

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

Douglas County beside the ground around it

Douglas County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 6 counties that border it, none has as large a share of high-potential ground; Champaign County comes nearest at 100%.

Share of land by USGS radon potential: Douglas County, the 6 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Douglas CountyZone 1NoneNone100%
Coles CountyZone 1None1.9%98.1%
Champaign CountyZone 1NoneNone100%
Moultrie CountyZone 1NoneNone100%
Piatt CountyZone 1NoneNone100%
Edgar CountyZone 1None5.1%94.9%
Vermilion CountyZone 1NoneNone100%
Illinois102 counties, pooled by land areaVaries0.9%34.5%64.5%

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

Local help

Douglas County, Local resources

Radon testing and mitigation in Douglas County

Listed radon businesses with an address in Douglas County:

Listed radon professionals by town: Tuscola

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

Douglas County, Questions

Questions about radon in Douglas County

Are radon levels high in Douglas County?

In 2017, 50.0% of the radon tests reported to CDC for Douglas County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.8 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 20 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Douglas County?

Douglas County borders 6 counties: Coles County, Champaign County, Moultrie County, Piatt County, Edgar County and Vermilion County.

Products

Douglas County, Products

Testing a home in Douglas County

In Douglas County, 50.0% of 84 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Douglas County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Douglas County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Douglas County

Explore

Douglas County, Bordering counties

Counties bordering Douglas County

Calculated by Radon411

Douglas County, Cities and towns

Cities and towns in Douglas County

The Census Bureau estimates 19,880 residents in Douglas County for July 1, 2025, 106 more than in 2020 (+0.5%). That works out to 48 people per square mile of land. Its largest town, Tuscola, has 4,668 residents, 23.5% of the total. Reported testing is thin here: 84 tests over 2017, or 4.2 for every 1,000 residents (2025 estimate), where Illinois as a whole comes to 10.9.

From Tuscola to Garrett, CDC publishes no figure by town: each reads Douglas County's.

The cities and towns in Douglas County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Tuscola4,668+0.6%23.5%
Arcola2,928−0.2%14.7%
Villa Grove2,447−1.2%12.3%
Arthurextends beyond Douglas County2,261+1.8%Counted whole
Atwoodextends beyond Douglas County1,100−0.9%Counted whole
Newman770−0.9%3.9%
Camargo459+0.9%2.3%
Hindsboro273−1.4%1.4%
Garrett126+0.8%0.6%

9 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 Douglas County is counted whole, so it has no share.

Douglas County, Homes

Homes in Douglas County

Douglas County is a place of houses on their own lots: 86% of its 8,492 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1968, close to Illinois' 1970: 41% date from before 1960 and 15% 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 Douglas County, Illinois, 2019 to 2023
HomesDouglas CountyIllinois
Housing units8,4925,443,501
Detached houses86%58%
In buildings of 5 or more4%22%
Mobile homes4%2%
Built before 196041%38%
Built since 200015%16%
Middle year built19681970
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.