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Radon Levels in Polk County, Iowa

EPA puts Polk County in Zone 1, its highest radon zone, and high results are common there: 64.4% of the 10,945 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

    64.4%

    5.9 pts above IA

    Polk
    64.4%
    Iowa
    58.5%

    10,945 tests, 2008 to 2017

  • Median result

    5.6pCi/L

    Action level reached

    Polk
    5.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    10,945

    Most tested in Iowa

    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

    51 of 99

    Middle half

    Polk
    64.4%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Polk County

Starts at Polk County's median, 5.6 pCi/L

5.6pCi/L

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

EPA’s reading of 5.6 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. Polk County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Polk County, At a glance

Polk County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Polk County, 2008 to 2017, laboratory
Under 2 pCi/L: 19%2 to 4 pCi/L: 17%4 pCi/L and above: 64%

Of 10,945 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Polk County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2,07819.0%
2 to 4 pCi/L1,81616.6%
4 pCi/L and above7,05164.4%
What these figures count

These are the 10,945 tests reported to CDC for Polk 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

Polk County, Compared

Polk County radon figures, compared

Calculated by Radon411

More than half: 64.4% of the 10,945 radon tests reported to CDC for Polk County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 51st of 99 Iowa counties with 30 or more tests for the same period. That is 5.9 points above the 58.5% pooled from 99 Iowa counties.

The median result, 5.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 304.4 pCi/L. The rest split 19.0% under 2 pCi/L and 16.6% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 64.4% share point the same way here.

4 of its 7 bordering counties with figures ran higher, led by Jasper County at 73.3%; Dallas County reported 58.5%. 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 Polk County went from 8,432 tests (2005 to 2014) to 10,945 (2008 to 2017), the share going from 65.9% to 64.4%.

Nationally, every county with a figure for the same period pools to 35.7%; Polk County sits 28.7 points above it. CDC also counts 1,639 tests taken after mitigation in Polk County for the same period: tests in homes where a fix was already in.

Polk County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Polk County
Polk County10,94564.4%5.6 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−5.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−28.7 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+19.8 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−38.5 points
Jasper County, IAborders it74673.3%8.2 pCi/L+8.9 points
Boone County, IAborders it1,13468.7%6.0 pCi/L+4.3 points
Marion County, IAborders it1,15167.3%6.0 pCi/L+2.9 points
Warren County, IAborders it1,51366.0%6.3 pCi/L+1.6 points
Madison County, IAborders it31862.3%6.0 pCi/L−2.1 points
Story County, IAborders it2,56859.9%5.0 pCi/L−4.5 points
Dallas County, IAborders it2,35258.5%4.9 pCi/L−5.9 points
Where Polk County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultPolk County testsPolk County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L2,07819.0%21.8%39.6%−2.8 points
2 to 4 pCi/L1,81616.6%19.7%24.7%−3.1 points
4 pCi/L and above7,05164.4%58.5%35.7%+5.9 points
Polk 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
Winneshiek County46 of 991,07166.4%6.2 pCi/L
Kossuth County47 of 9943466.1%5.7 pCi/L
Warren County48 of 991,51366.0%6.3 pCi/L
Adams County49 of 998165.4%6.1 pCi/L
Hancock County50 of 9964064.5%5.5 pCi/L
Polk County51 of 9910,94564.4%5.6 pCi/L
Hamilton County52 of 9925264.3%5.5 pCi/L
Hardin County53 of 9934962.8%5.6 pCi/L
Fayette County54 of 9974662.7%5.6 pCi/L
Clayton County55 of 9931062.6%5.8 pCi/L
Madison County56 of 9931862.3%6.0 pCi/L
Polk County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201710,94564.4%5.6 pCi/L304.4 pCi/L58.5%−0.2 points
2007 to 201610,12664.6%5.6 pCi/L304.4 pCi/L58.6%−0.5 points
2006 to 20159,56665.1%5.7 pCi/L304.4 pCi/L59.4%−0.8 points
2005 to 20148,43265.9%5.8 pCi/L68.1 pCi/L59.6%First on file

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

Polk County, Geology

The ground under Polk County

Predicted

USGS's geologic map puts all of Polk County's mapped land in one class: high radon potential. The map puts 71.7% of Polk County in the area it calls Des Moines Lobe and 28.3% in Loess-Covered Drift Plains. USGS gives the first a radon index of 12 and the second 13, both in the high band (12 to 17).

USGS's geologic areas under Polk County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Des Moines LobeCalcareous loamy till derived from shale, limestone, dolomite, sandstone.High1271.7%
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1328.3%

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

Polk County beside the ground around it

On high-potential ground Polk County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 7 counties that border it, none has as large a share of high-potential ground; Boone County comes nearest at 100%.

Share of land by USGS radon potential: Polk County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Polk CountyZone 1NoneNone100%
Story CountyZone 1NoneNone100%
Dallas CountyZone 1NoneNone100%
Jasper CountyZone 1NoneNone100%
Boone CountyZone 1NoneNone100%
Warren CountyZone 1NoneNone100%
Madison CountyZone 1NoneNone100%
Marion CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Polk County, Local resources

Radon testing and mitigation in Polk County

Listed radon businesses with an address in Polk County:

Listed radon professionals by town: Des Moines, Ankeny, West Des Moines, Urbandale, Johnston, Altoona, Clive, Norwalk, Pleasant Hill, Bondurant, Polk City

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

Polk County, Questions

Questions about radon in Polk County

Are radon levels high in Polk County?

Over the 2008 to 2017 laboratory totals, 64.4% of the radon tests reported to CDC for Polk County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.6 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 50 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Polk County?

Polk County borders 7 counties: Story County, Dallas County, Jasper County, Boone County, Warren County, Madison County and Marion County.

Products

Polk County, Products

Testing a home in Polk County

In Polk County, 64.4% of 10,945 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 Polk 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

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

Explore

Polk County, Bordering counties

Counties bordering Polk County

Calculated by Radon411

Polk County, Cities and towns

Cities and towns in Polk County

The Census Bureau estimates 516,546 residents in Polk County for July 1, 2025, 23,533 more than in 2020 (+4.8%). That works out to 903 people per square mile of land. Des Moines, the largest place on its list (212,086 residents in all), extends beyond Polk County, so no share of the total is worked out for it. CDC's 10,945 reported tests for 2008 to 2017 work out to 21.2 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Des Moines to Sheldahl, CDC publishes no figure by town: each reads Polk County's.

The 12 largest cities and towns in Polk County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Des Moinesextends beyond Polk County212,086−0.7%Counted whole
Ankeny77,833+13.4%15.1%
West Des Moinesextends beyond Polk County74,224+7.6%Counted whole
Urbandaleextends beyond Polk County48,570+6.5%Counted whole
Johnston25,065+4.5%4.9%
Altoona22,796+15.5%4.4%
Cliveextends beyond Polk County19,861+6.3%Counted whole
Grimesextends beyond Polk County17,405+10.7%Counted whole
Norwalkextends beyond Polk County15,004+16.7%Counted whole
Pleasant Hill11,239+10.7%2.2%
Bondurant9,647+29.1%1.9%
Polk City6,630+18.2%1.3%
  • Windsor Heights
  • Carlisle (part)
  • Mitchellville (part)
  • Granger (part)
  • Elkhart
  • Runnells
  • Alleman
  • Sheldahl (part)

20 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 Polk County is counted whole, so it has no share.

Polk County, Homes

Homes in Polk County

Of Polk County's 215,016 homes, 62% are detached houses, against 72% across Iowa; 24% are in buildings of five or more homes. Much of Polk County is recent building: 29% of its homes have gone up since 2000 and the middle year built is 1981, against 1971 for Iowa. 67% of occupied homes are lived in by their owner (Iowa: 72%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Polk County, Iowa, 2019 to 2023
HomesPolk CountyIowa
Housing units215,0161,427,175
Detached houses62%72%
In buildings of 5 or more24%14%
Mobile homes2%3%
Built before 196029%39%
Built since 200029%21%
Middle year built19811971
Owner-occupied67%72%

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