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Radon Levels in Peoria County, Illinois

EPA puts Peoria County in Zone 1, its highest radon zone, and high results are common there: 40.2% of the 3,816 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

    40.2%

    6.5 pts above IL

    Peoria
    40.2%
    Illinois
    33.7%

    3,816 tests, 2017

  • Median result

    3.1pCi/L

    Below action level

    Peoria
    3.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    3,816

    10th of 70 by tests

    Peoria
    3,816
    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

    41 of 70

    Middle half

    Peoria
    40.2%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Peoria County

Starts at Peoria County's median, 3.1 pCi/L

3.1pCi/L

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

EPA’s reading of 3.1 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. Peoria County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Peoria County, At a glance

Peoria County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Peoria 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 Peoria County, 2017

Share of reported tests at or above 4 pCi/L, by year, Peoria County
Share of reported tests at or above 4 pCi/L, by year, Peoria County
YearShare of reported tests at or above 4 pCi/L
201441.6%
201541.7%
201625.0%
201740.2%

2017: 40.2%. Across these years the share ran from 25.0% to 41.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 3,816 tests reported to CDC for Peoria 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

Peoria County, Compared

Peoria County radon figures, compared

Calculated by Radon411

In Peoria County, about 4 in 10 reported tests in 2017 (1,533 of 3,816) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 8.5 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Peoria County runs 6.5 points above its state.

Of 6 neighbours with a figure, all 6 reported a larger share at or above 4 pCi/L; the spread is 46.4% (Tazewell County) to 69.2% (Stark County). By share, Peoria County is 41st of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 41.6% and 2017 closed at 40.2% (about level), with 2015 the high at 41.7%. Half the tests came in under 3.1 pCi/L and half over it; the single highest reached 44.0 pCi/L. Below the action level, 1,293 tests (33.9%) came in under 2 pCi/L, against 37.7% statewide, and 990 tests (25.9%) fell between 2 and 4, against 28.6% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 40.2% share point the same way here. USGS geology rates 100% of the county's land high radon potential.

The busiest year on file was 2014, with 6,231 tests reported; the quietest, 2016, had 12.

Share of reported tests at or above 4 pCi/L by year, Peoria County against Illinois2014 to 2017, years with 30 or more tests: Peoria County 41.6% to 40.2%, the state's pooled share 33.7% in 2017.
Peoria CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Peoria County against Illinois: data table
YearTestsPeoria County, at or above 4 pCi/LIllinois, pooled
20146,23141.6%37.8%
20152,13941.7%36.6%
20173,81640.2%33.7%
Peoria County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Peoria County
Peoria County3,81640.2%3.1 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−6.5 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−8.5 points
Mercer Countyhighest in the state6668.2%5.5 pCi/L+28.0 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−31.8 points
Stark County, ILborders it3969.2%5.8 pCi/L+29.0 points
Fulton County, ILborders it14464.6%5.8 pCi/L+24.4 points
Knox County, ILborders it24956.6%4.7 pCi/L+16.4 points
Woodford County, ILborders it76552.9%4.2 pCi/L+12.7 points
Marshall County, ILborders it8148.1%3.8 pCi/L+7.9 points
Tazewell County, ILborders it2,72446.4%3.6 pCi/L+6.2 points
Where Peoria County's reported results fell, 2017, beside Illinois and the United States
ResultPeoria County testsPeoria County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L1,29333.9%37.7%43.5%−3.8 points
2 to 4 pCi/L99025.9%28.6%24.8%−2.7 points
4 pCi/L and above1,53340.2%33.7%31.7%+6.5 points
Peoria 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
Sangamon County36 of 703,37843.7%3.7 pCi/L
Whiteside County37 of 7069643.1%3.3 pCi/L
McLean County38 of 704,54842.5%3.3 pCi/L
Christian County39 of 7021342.3%3.5 pCi/L
DeKalb County40 of 701,70741.1%3.3 pCi/L
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
Peoria County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20173,81640.2%3.1 pCi/L44.0 pCi/L33.7%+15.2 points
20161225.0%1.7 pCi/L5.7 pCi/L17.4%−16.7 points
20152,13941.7%3.1 pCi/L26.1 pCi/L36.6%+0.1 points
20146,23141.6%3.2 pCi/L56.6 pCi/L37.8%First on file

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

Peoria County, Geology

The ground under Peoria County

Predicted

USGS's geologic map puts all of Peoria County's mapped land in one class: high radon potential. The map puts 69.0% of Peoria County in the area it calls Galesburg Plain and 31.0% in Bloomington Ridged Plain. USGS gives both a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Peoria County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Galesburg PlainIllinoian glacial deposits and loess over Paleozoic sedimentary rocks.High1369.0%
Bloomington Ridged PlainWisconsinan glacial deposits and loess over Paleozoic sedimentary rocks.High1331.0%

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

Peoria County beside the ground around it

Peoria 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; Fulton County comes nearest at 100%.

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

Peoria County, Local resources

Radon testing and mitigation in Peoria County

Listed radon businesses with an address in Peoria County:

Listed radon professionals by town: Peoria, Princeville, Dunlap, Hanna City

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

Peoria County, Questions

Questions about radon in Peoria County

Are radon levels high in Peoria County?

In 2017, 40.2% of the radon tests reported to CDC for Peoria County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.1 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 40 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Peoria County?

Peoria County borders 6 counties: Tazewell County, Stark County, Knox County, Fulton County, Woodford County and Marshall County.

Products

Peoria County, Products

Testing a home in Peoria County

In Peoria County, 40.2% of 3,816 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Peoria 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

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

Explore

Peoria County, Bordering counties

Counties bordering Peoria County

Calculated by Radon411

Peoria County, Cities and towns

Cities and towns in Peoria County

About 178,553 people live in Peoria County by the Census Bureau's estimate for July 1, 2025, 2,952 fewer than in 2020 (−1.6%). That works out to 289 people per square mile of land. Peoria alone is home to 110,920 of them, 62.1% of the total. Testing is reported here more often than across the state: CDC's 3,816 reported tests for 2017 come to 21.4 for every 1,000 residents (2025 estimate), against 10.9 for Illinois.

From Peoria to Mapleton, CDC publishes no figure by town: each reads Peoria County's.

The 12 largest cities and towns in Peoria County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Peoria110,920−1.7%62.1%
Pekinextends beyond Peoria County31,277−1.6%Counted whole
Chillicothe6,033−1.2%3.4%
Bartonville5,804−2.1%3.3%
Peoria Heightsextends beyond Peoria County5,767−2.1%Counted whole
West Peoria4,187−1.9%2.3%
Farmingtonextends beyond Peoria County2,298−4.0%Counted whole
Elmwood2,030−1.9%1.1%
Bellevue1,888+0.8%1.1%
Princeville1,713−0.9%1.0%
Dunlap1,588−1.3%0.9%
Hanna City1,238−1.7%0.7%
  • Glasford
  • Brimfield
  • Norwood
  • Kingston Mines
  • Mapleton

17 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 Peoria County is counted whole, so it has no share.

Peoria County, Homes

Homes in Peoria County

Of Peoria County's 84,992 homes, 72% are detached houses, against 58% across Illinois; 18% are in buildings of five or more homes. Half of its homes were built before 1966, close to Illinois' 1970: 42% date from before 1960 and 15% from 2000 or later. 67% of occupied homes are lived in by their owner (Illinois: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Peoria County, Illinois, 2019 to 2023
HomesPeoria CountyIllinois
Housing units84,9925,443,501
Detached houses72%58%
In buildings of 5 or more18%22%
Mobile homes1%2%
Built before 196042%38%
Built since 200015%16%
Middle year built19661970
Owner-occupied67%67%

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