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Radon Levels in Rock Island County, Illinois

EPA puts Rock Island County in Zone 1, its highest radon zone, and high results are common there: 46.5% of the 2,283 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

    46.5%

    12.8 pts above IL

    Rock Island
    46.5%
    Illinois
    33.7%

    2,283 tests, 2017

  • Median result

    3.7pCi/L

    Below action level

    Rock Island
    3.7 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2017

  • Tests reported

    2,283

    16th of 70 by tests

    Rock Island
    2,283
    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

    26 of 70

    Middle half

    Rock Island
    46.5%
    Stark
    69.2%

    By share, of 70 with 30+ tests

Read a result for Rock Island County

Starts at Rock Island County's median, 3.7 pCi/L

3.7pCi/L

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

EPA’s reading of 3.7 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. Rock Island County's median reported result, 2017.

Interpret this readingWhat a fix costs

The data

Rock Island County, At a glance

Rock Island County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Rock Island 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 Rock Island County, 2017

Share of reported tests at or above 4 pCi/L, by year, Rock Island County
Share of reported tests at or above 4 pCi/L, by year, Rock Island County
YearShare of reported tests at or above 4 pCi/L
201460.4%
201557.5%
2016100.0%
201746.5%

2017: 46.5%. Across these years the share ran from 46.5% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 2,283 tests reported to CDC for Rock Island 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

Rock Island County, Compared

Rock Island County radon figures, compared

Calculated by Radon411

In Rock Island County, about 5 in 10 reported tests in 2017 (1,062 of 2,283) were at or above EPA's action level. Against the national pool of 31.7%, the gap is 14.8 points higher. Across 93 Illinois counties pooled together, 33.7% of tests reached that level, so Rock Island County runs 12.8 points above its state.

Of 3 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 43.1% (Whiteside County) to 68.2% (Mercer County). By share, Rock Island County is 26th of 70 Illinois counties with 30 or more tests for the same period.

Year by year, 2014 opened at 60.4% and 2017 closed at 46.5% (down 13.9 points), with 2014 the high at 60.4%. Half the tests came in under 3.7 pCi/L and half over it; the single highest reached 33.1 pCi/L. Below the action level, 627 tests (27.5%) came in under 2 pCi/L, against 37.7% statewide, and 594 tests (26.0%) fell between 2 and 4, against 28.6% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 46.5% 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 2,877 tests reported; the quietest, 2016, had 9.

Share of reported tests at or above 4 pCi/L by year, Rock Island County against Illinois2014 to 2017, years with 30 or more tests: Rock Island County 60.4% to 46.5%, the state's pooled share 33.7% in 2017.
Rock Island CountyIllinois, pooled
Share of reported tests at or above 4 pCi/L by year, Rock Island County against Illinois: data table
YearTestsRock Island County, at or above 4 pCi/LIllinois, pooled
20142,87760.4%37.8%
20151,48857.5%36.6%
20172,28346.5%33.7%
Rock Island County against Illinois, the United States and nearby counties, 2017
AreaTestsAt or above 4 pCi/LMedianDifference from Rock Island County
Rock Island County2,28346.5%3.7 pCi/LThis county
Illinois, pooled93 counties, pooled138,00633.7%Not pooled−12.8 points
United States, pooled937 counties, pooled528,06231.7%Not pooled−14.8 points
Stark Countyhighest in the state3969.2%5.8 pCi/L+22.7 points
Williamson Countylowest in the state2498.4%0.9 pCi/L−38.1 points
Mercer County, ILborders it6668.2%5.5 pCi/L+21.7 points
Henry County, ILborders it42055.7%4.6 pCi/L+9.2 points
Whiteside County, ILborders it69643.1%3.3 pCi/L−3.4 points
Where Rock Island County's reported results fell, 2017, beside Illinois and the United States
ResultRock Island County testsRock Island County shareIllinois shareU.S. shareAgainst Illinois
Under 2 pCi/L62727.5%37.7%43.5%−10.2 points
2 to 4 pCi/L59426.0%28.6%24.8%−2.6 points
4 pCi/L and above1,06246.5%33.7%31.7%+12.8 points
Rock Island 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
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
Jersey County27 of 7012946.5%3.6 pCi/L
Tazewell County28 of 702,72446.4%3.6 pCi/L
Adams County29 of 7088546.1%3.6 pCi/L
Logan County30 of 707245.8%3.4 pCi/L
LaSalle County31 of 701,00245.8%3.6 pCi/L
Rock Island County radon tests by year, against Illinois' pooled share
YearTestsAt or above 4 pCi/LMedianHighestIllinois, pooledChange from the row before
20172,28346.5%3.7 pCi/L33.1 pCi/L33.7%−53.5 points
20169100.0%10.6 pCi/L11.5 pCi/L17.4%+42.5 points
20151,48857.5%4.8 pCi/L38.0 pCi/L36.6%−2.9 points
20142,87760.4%5.1 pCi/L39.3 pCi/L37.8%First on file

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

Rock Island County, Geology

The ground under Rock Island County

Predicted

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

USGS's geologic areas under Rock Island County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Galesburg PlainIllinoian glacial deposits and loess over Paleozoic sedimentary rocks.High1399.9%

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

Rock Island County beside the ground around it

Rock Island County has more high-potential ground than Illinois as a whole: 100% of its land against 64.5%. Of the 7 counties that border it, none has as large a share of high-potential ground; Henry County comes nearest at 100%.

Share of land by USGS radon potential: Rock Island County, the 7 counties bordering it and Illinois
AreaEPA zoneLow potentialModerate potentialHigh potential
Rock Island CountyZone 1NoneNone100%
Henry CountyZone 1NoneNone100%
Scott County, IAZone 1NoneNone100%
Whiteside CountyZone 1NoneNone100%
Clinton County, IAZone 1NoneNone100%
Mercer CountyZone 1NoneNone100%
Muscatine County, IAZone 1NoneNone100%
Louisa County, IAZone 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

Rock Island County, Local resources

Radon testing and mitigation in Rock Island County

Listed radon businesses with an address in Rock Island County:

Listed radon professionals by town: Moline

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

Rock Island County, Questions

Questions about radon in Rock Island County

Are radon levels high in Rock Island County?

In 2017, 46.5% of the radon tests reported to CDC for Rock Island County, Illinois were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.7 pCi/L. Of 70 Illinois counties with 30 or more tests for the same period, 25 reported a higher share; pooled, the state comes to 33.7%.

Which counties border Rock Island County?

Rock Island County borders 7 counties: Henry County, IL, Scott County, IA, Whiteside County, IL, Clinton County, IA, Mercer County, IL, Muscatine County, IA and Louisa County, IA.

Products

Rock Island County, Products

Testing a home in Rock Island County

In Rock Island County, 46.5% of 2,283 tests reported to CDC in 2017 reached 4 pCi/L, against 33.7% pooled across Illinois. In Zone 1 the year-round level in Rock Island 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

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

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Rock Island County, Bordering counties

Counties bordering Rock Island County

Calculated by Radon411

Rock Island County, Cities and towns

Cities and towns in Rock Island County

About 141,869 people live in Rock Island County by the Census Bureau's estimate for July 1, 2025, 2,488 fewer than in 2020 (−1.7%). That works out to 332 people per square mile of land. Its largest town, Moline, has 42,362 residents, 29.9% of the total. CDC's 2,283 reported tests for 2017 work out to 16.1 per 1,000 residents (2025 estimate), close to Illinois' 10.9.

From Moline to Hillsdale, CDC publishes no figure by town: each reads Rock Island County's.

The 12 largest cities and towns in Rock Island County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Moline42,362−1.2%29.9%
Rock Island36,225−2.1%25.5%
East Moline20,453−4.0%14.4%
Silvis7,979Level5.6%
Milan5,028−1.3%3.5%
Coal Valleyextends beyond Rock Island County3,859−0.2%Counted whole
Carbon Cliff1,810−1.7%1.3%
Hampton1,751−1.2%1.2%
Port Byron1,638−1.4%1.2%
Andalusia1,175−1.0%0.8%
Rapids City939−0.6%0.7%
Cordova656−1.9%0.5%
  • Reynolds (part)
  • Oak Grove
  • Hillsdale

15 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 Rock Island County is counted whole, so it has no share.

Rock Island County, Homes

Homes in Rock Island County

Of Rock Island County's 66,742 homes, 70% are detached houses, against 58% across Illinois; 16% are in buildings of five or more homes. The homes are older than Illinois' as a whole: half were built before 1962 (1970 for Illinois), and 47% date from before 1960. 69% 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 Rock Island County, Illinois, 2019 to 2023
HomesRock Island CountyIllinois
Housing units66,7425,443,501
Detached houses70%58%
In buildings of 5 or more16%22%
Mobile homes2%2%
Built before 196047%38%
Built since 200010%16%
Middle year built19621970
Owner-occupied69%67%

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