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Radon Levels in Woodford County, Illinois

EPA puts Woodford County in Zone 1, its highest radon zone, and high results are common there: 52.9% of the 765 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

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  • Share at 4+ pCi/L

    52.9%

    19.2 pts above IL

    Woodford
    52.9%
    Illinois
    33.7%

    765 tests, 2017

  • Median result

    4.2pCi/L

    Action level reached

    Woodford
    4.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    765

    21st of 70 by tests

    Woodford
    765
    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

    17 of 70

    Top quarter

    Woodford
    52.9%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Woodford County

Starts at Woodford County's median, 4.2 pCi/L

4.2pCi/L

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

EPA’s reading of 4.2 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. Woodford County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Woodford County, At a glance

Woodford County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Woodford 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 Woodford County, 2017

Share of reported tests at or above 4 pCi/L, by year, Woodford County
Share of reported tests at or above 4 pCi/L, by year, Woodford County
YearShare of reported tests at or above 4 pCi/L
201457.1%
201557.6%
201675.0%
201752.9%

2017: 52.9%. Across these years the share ran from 52.9% to 75.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 765 tests reported to CDC for Woodford 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

Woodford County, Compared

Woodford County radon figures, compared

Calculated by Radon411

More than half: 52.9% of the 765 radon tests reported to CDC for Woodford County in 2017 read at least 4 pCi/L. That places it 17th of 70 Illinois counties with 30 or more tests for the same period. That is 19.2 points above the 33.7% pooled from 93 Illinois counties.

The median result, 4.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 34.0 pCi/L. The rest split 28.2% under 2 pCi/L and 18.8% from 2 to 4 (Illinois: 37.7% and 28.6%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 52.9% share point the same way here.

1 of its 6 bordering counties with figures ran higher, led by Livingston County at 61.7%; Peoria County reported 40.2%. 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 2014, with 1,230 tests reported; the quietest, 2016, had 12.

Over 3 years of annual figures the share fell 4.2 points, from 57.1% in 2014 to 52.9% in 2017; its peak was 57.6% in 2015. Nationally, every county with a figure for the same period pools to 31.7%; Woodford County sits 21.2 points above it.

Share of reported tests at or above 4 pCi/L by year, Woodford County against Illinois2014 to 2017, years with 30 or more tests: Woodford County 57.1% to 52.9%, the state's pooled share 33.7% in 2017.
Woodford CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Woodford County against Illinois: data table
YearTestsWoodford County, at or above 4 pCi/LIllinois, pooled
20141,23057.1%37.8%
201549557.6%36.6%
201776552.9%33.7%
Woodford County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Woodford County
Woodford County76552.9%4.2 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−19.2 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−21.2 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+16.3 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−44.5 points
Livingston County, ILborders it34561.7%5.3 pCi/L+8.8 points
Marshall County, ILborders it8148.1%3.8 pCi/L−4.8 points
Tazewell County, ILborders it2,72446.4%3.6 pCi/L−6.5 points
LaSalle County, ILborders it1,00245.8%3.6 pCi/L−7.1 points
McLean County, ILborders it4,54842.5%3.3 pCi/L−10.4 points
Peoria County, ILborders it3,81640.2%3.1 pCi/L−12.7 points
Where Woodford County's reported results fell, 2017, beside Illinois and the United States
ResultWoodford County testsWoodford County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L21628.2%37.7%43.5%−9.5 points
2 to 4 pCi/L14418.8%28.6%24.8%−9.8 points
4 pCi/L and above40552.9%33.7%31.7%+19.2 points
Woodford 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
Henry County12 of 7042055.7%4.6 pCi/L
McDonough County12 of 7021055.7%4.3 pCi/L
Piatt County14 of 7027954.8%4.3 pCi/L
Vermilion County15 of 703953.8%4.7 pCi/L
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
Woodford County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
201776552.9%4.2 pCi/L34.0 pCi/L33.7%−22.1 points
20161275.0%19.8 pCi/L35.6 pCi/L17.4%+17.4 points
201549557.6%4.9 pCi/L43.5 pCi/L36.6%+0.5 points
20141,23057.1%5.1 pCi/L39.2 pCi/L37.8%First on file

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

Woodford County, Geology

The ground under Woodford County

Predicted

USGS's geologic map puts all of Woodford 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 Woodford 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.

Woodford County beside the ground around it

Woodford 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; LaSalle County comes nearest at 100%.

Share of land by USGS radon potential: Woodford County, the 6 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Woodford CountyZone 1NoneNone100%
Marshall CountyZone 1NoneNone100%
Tazewell CountyZone 1NoneNone100%
McLean CountyZone 1NoneNone100%
Peoria CountyZone 1NoneNone100%
Livingston CountyZone 1NoneNone100%
LaSalle 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

Woodford County, Local resources

Radon testing and mitigation in Woodford 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

Woodford County, Questions

Questions about radon in Woodford County

Are radon levels high in Woodford County?

In 2017, 52.9% of the radon tests reported to CDC for Woodford County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.2 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 16 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Woodford County?

Woodford County borders 6 counties: Marshall County, Tazewell County, McLean County, Peoria County, Livingston County and LaSalle County.

Products

Woodford County, Products

Testing a home in Woodford County

In Woodford County, 52.9% of 765 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Woodford 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

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

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Woodford County, Bordering counties

Counties bordering Woodford County

Calculated by Radon411

Woodford County, Cities and towns

Cities and towns in Woodford County

About 38,111 people live in Woodford County by the Census Bureau's estimate for July 1, 2025, 294 fewer than in 2020 (−0.8%). That works out to 72 people per square mile of land. No town dominates: Eureka, the largest, has 5,129 residents, 13.5% of the total. Testing is reported here more often than across the state: CDC's 765 reported tests for 2017 come to 20.1 for every 1,000 residents (2025 estimate), against 10.9 for Illinois.

From Eureka to Panola, CDC publishes no figure by town: each reads Woodford County's.

The 12 largest cities and towns in Woodford County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Eureka5,129−1.7%13.5%
Metamora3,857−1.0%10.1%
Germantown Hills3,436+0.3%9.0%
El Pasoextends beyond Woodford County2,723−0.9%Counted whole
Roanoke1,918−1.9%5.0%
Minonk1,889−1.9%5.0%
Washburnextends beyond Woodford County1,008−2.4%Counted whole
Goodfieldextends beyond Woodford County961+1.5%Counted whole
Deer Creekextends beyond Woodford County649−2.0%Counted whole
Congerville500+1.2%1.3%
Spring Bay489+4.9%1.3%
Benson403−2.2%1.1%
  • Bay View Gardens
  • Secor
  • Kappa
  • Panola

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 Woodford County is counted whole, so it has no share.

Woodford County, Homes

Homes in Woodford County

Woodford County is a place of houses on their own lots: 85% of its 15,745 homes are detached single-family houses, against 58% across Illinois. Half of its homes were built before 1973, close to Illinois' 1970: 35% date from before 1960 and 19% from 2000 or later. Owners live in 84% of the occupied homes (Illinois: 67%), so for most households a test and a fix are their own to order.

Homes in Woodford County, Illinois, 2019 to 2023
HomesWoodford CountyIllinois
Housing units15,7455,443,501
Detached houses85%58%
In buildings of 5 or more4%22%
Mobile homes4%2%
Built before 196035%38%
Built since 200019%16%
Middle year built19731970
Owner-occupied84%67%

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