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Radon Levels in Butler County, Iowa

EPA puts Butler County in Zone 1, its highest radon zone, and high results are common there: 59.9% of the 377 radon tests reported to CDC (2008 to 2017, laboratory totals) 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

    59.9%

    1.4 pts above IA

    Butler
    59.9%
    Iowa
    58.5%

    377 tests, 2008 to 2017

  • Median result

    5.2pCi/L

    Action level reached

    Butler
    5.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    377

    62nd of 99 by tests

    Butler
    377
    Polk
    10,945

    Reported to CDC before any fix, 2008 to 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 Iowa

    64 of 99

    Middle half

    Butler
    59.9%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Butler County

Starts at Butler County's median, 5.2 pCi/L

5.2pCi/L

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

EPA’s reading of 5.2 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. Butler County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Butler County, At a glance

Butler County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Butler 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 Butler County, 2008 to 2017, laboratory

Reported results by concentration band, Butler County, 2008 to 2017, laboratory
Under 2 pCi/L: 21%2 to 4 pCi/L: 19%4 pCi/L and above: 60%

Of 377 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Butler County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L8121.5%
2 to 4 pCi/L7018.6%
4 pCi/L and above22659.9%
What these figures count

These are the 377 tests reported to CDC for Butler County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Butler County, Compared

Butler County radon figures, compared

Calculated by Radon411

More than half: 59.9% of the 377 radon tests reported to CDC for Butler County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 64th of 99 Iowa counties with 30 or more tests for the same period. That is 1.4 points above the 58.5% pooled from 99 Iowa counties.

The median result, 5.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 65.7 pCi/L. The rest split 21.5% under 2 pCi/L and 18.6% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 59.9% share point the same way here.

3 of its 8 bordering counties with figures ran higher, led by Franklin County at 73.5%; Black Hawk County reported 48.4%. Statewide for the same period, Sioux County reported the highest share (84.2%) and Decatur County the lowest (25.9%).

CDC's ten-year totals for Butler County went from 259 tests (2005 to 2014) to 377 (2008 to 2017), the share going from 61.8% to 59.9%.

Nationally, every county with a figure for the same period pools to 35.7%; Butler County sits 24.2 points above it. CDC also counts 48 tests taken after mitigation in Butler County for the same period: tests in homes where a fix was already in.

Butler County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Butler County
Butler County37759.9%5.2 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−1.4 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−24.2 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+24.3 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−34.0 points
Franklin County, IAborders it31373.5%6.2 pCi/L+13.6 points
Grundy County, IAborders it50166.9%6.9 pCi/L+7.0 points
Hardin County, IAborders it34962.8%5.6 pCi/L+2.9 points
Floyd County, IAborders it69759.5%5.1 pCi/L−0.4 points
Cerro Gordo County, IAborders it1,66259.0%4.8 pCi/L−0.9 points
Chickasaw County, IAborders it49859.0%4.9 pCi/L−0.9 points
Bremer County, IAborders it95753.0%4.3 pCi/L−6.9 points
Black Hawk County, IAborders it3,22348.4%3.8 pCi/L−11.5 points
Where Butler County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultButler County testsButler County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L8121.5%21.8%39.6%−0.3 points
2 to 4 pCi/L7018.6%19.7%24.7%−1.1 points
4 pCi/L and above22659.9%58.5%35.7%+1.4 points
Butler County ranked among the 99 Iowa counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Howard County59 of 9938861.3%5.9 pCi/L
Mahaska County60 of 9928861.1%5.2 pCi/L
Taylor County61 of 9923560.9%4.6 pCi/L
Cedar County62 of 9976560.4%5.0 pCi/L
Keokuk County63 of 9921460.3%5.2 pCi/L
Butler County64 of 9937759.9%5.2 pCi/L
Story County65 of 992,56859.9%5.0 pCi/L
Floyd County66 of 9969759.5%5.1 pCi/L
Jones County67 of 9955559.3%5.1 pCi/L
Iowa County68 of 9951959.2%5.1 pCi/L
Chickasaw County69 of 9949859.0%4.9 pCi/L
Butler County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201737759.9%5.2 pCi/L65.7 pCi/L58.5%−0.3 points
2007 to 201631460.2%5.2 pCi/L65.7 pCi/L58.6%−1.1 points
2006 to 201527461.3%5.2 pCi/L65.7 pCi/L59.4%−0.5 points
2005 to 201425961.8%5.3 pCi/L65.7 pCi/L59.6%First on file

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

Butler County, Geology

The ground under Butler County

Predicted

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

USGS's geologic areas under Butler County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Iowan SurfacePre-Illinoian glaical deposits and loess.High12100%

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

Butler County beside the ground around it

On high-potential ground Butler County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 8 counties that border it, none has as large a share of high-potential ground; Black Hawk County comes nearest at 100%.

Share of land by USGS radon potential: Butler County, the 8 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Butler CountyZone 1NoneNone100%
Floyd CountyZone 1NoneNone100%
Bremer CountyZone 1NoneNone100%
Franklin CountyZone 1NoneNone100%
Grundy CountyZone 1NoneNone100%
Chickasaw CountyZone 1NoneNone100%
Black Hawk CountyZone 1NoneNone100%
Cerro Gordo CountyZone 1NoneNone100%
Hardin CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Butler County, Local resources

Radon testing and mitigation in Butler County

Listed radon businesses with an address in Butler County:

Listed radon professionals by town: Aplington

What Iowa's program says
Phone
(515) 281-4928
Licensing of radon professionals
Iowa’s radon program approves applications for persons who wish to become certified to perform radon testing or credentialed to perform mitigation and laboratories that provide radon testing devices and analytical services.
Disclosure when a home is sold or rented
However, per Iowa Code chapters 543B.9 and 543B.18 and Iowa Administrative Code 193E Chapter 14 administered by the Iowa Real Estate Commission, a seller must disclose any known tests for the presence of radon and if yes, provide the date of last report and the result(s).

What it means

Butler County, Questions

Questions about radon in Butler County

Are radon levels high in Butler County?

Over the 2008 to 2017 laboratory totals, 59.9% of the radon tests reported to CDC for Butler County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.2 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 63 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Butler County?

Butler County borders 8 counties: Floyd County, Bremer County, Franklin County, Grundy County, Chickasaw County, Black Hawk County, Cerro Gordo County and Hardin County.

Products

Butler County, Products

Testing a home in Butler County

In Butler County, 59.9% of 377 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 58.5% pooled across Iowa. In Zone 1 the year-round level in Butler 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

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

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Butler County, Bordering counties

Counties bordering Butler County

Calculated by Radon411

Butler County, Cities and towns

Cities and towns in Butler County

About 14,049 people live in Butler County by the Census Bureau's estimate for July 1, 2025, 288 fewer than in 2020 (−2.0%). That works out to 24 people per square mile of land. No town dominates: Parkersburg, the largest, has 1,969 residents, 14.0% of the total. CDC's 377 reported tests for 2008 to 2017 work out to 26.8 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Parkersburg to Aredale, CDC publishes no figure by town: each reads Butler County's.

The cities and towns in Butler County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Parkersburg1,969−2.4%14.0%
Shell Rock1,252−1.3%8.9%
Clarksville1,225−2.7%8.7%
Aplington1,084−2.4%7.7%
Greeneextends beyond Butler County939−5.6%Counted whole
Allison933−3.2%6.6%
Dumont612−4.1%4.4%
New Hartford553−3.2%3.9%
Bristow135−4.9%1.0%
Aredale61−3.2%0.4%

10 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 Butler County is counted whole, so it has no share.

Butler County, Homes

Homes in Butler County

Butler County is a place of houses on their own lots: 89% of its 6,569 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1956 (1971 for Iowa), and 54% date from before 1960. Owners live in 80% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Butler County, Iowa, 2019 to 2023
HomesButler CountyIowa
Housing units6,5691,427,175
Detached houses89%72%
In buildings of 5 or more4%14%
Mobile homes2%3%
Built before 196054%39%
Built since 200014%21%
Middle year built19561971
Owner-occupied80%72%

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