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Radon Levels in Dallas County, Iowa

EPA puts Dallas County in Zone 1, its highest radon zone, and high results are common there: 58.5% of the 2,352 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

    58.5%

    0.0 pts above IA

    Dallas
    58.5%
    Iowa
    58.5%

    2,352 tests, 2008 to 2017

  • Median result

    4.9pCi/L

    Action level reached

    Dallas
    4.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    2,352

    9th of 99 by tests

    Dallas
    2,352
    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

    71 of 99

    Middle half

    Dallas
    58.5%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Dallas County

Starts at Dallas County's median, 4.9 pCi/L

4.9pCi/L

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

EPA’s reading of 4.9 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. Dallas County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Dallas County, At a glance

Dallas County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Dallas County, 2008 to 2017, laboratory
Under 2 pCi/L: 21%2 to 4 pCi/L: 21%4 pCi/L and above: 58%

Of 2,352 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Dallas County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L48620.7%
2 to 4 pCi/L48920.8%
4 pCi/L and above1,37758.5%
What these figures count

These are the 2,352 tests reported to CDC for Dallas 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

Dallas County, Compared

Dallas County radon figures, compared

Calculated by Radon411

More than half: 58.5% of the 2,352 radon tests reported to CDC for Dallas County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 71st of 99 Iowa counties with 30 or more tests for the same period. Pooled across 99 Iowa counties, the share is the same 58.5%.

The median result, 4.9 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 103.9 pCi/L. The rest split 20.7% under 2 pCi/L and 20.8% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 58.5% share point the same way here.

All 7 of its bordering counties with figures ran higher, led by Adair County at 72.4%; the lowest of them, Madison County, reported 62.3%. 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 Dallas County went from 1,646 tests (2005 to 2014) to 2,352 (2008 to 2017), the share going from 60.0% to 58.5%.

Nationally, every county with a figure for the same period pools to 35.7%; Dallas County sits 22.8 points above it. CDC also counts 318 tests taken after mitigation in Dallas County for the same period: tests in homes where a fix was already in.

Dallas County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Dallas County
Dallas County2,35258.5%4.9 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooledLevel
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−22.8 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+25.7 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−32.6 points
Adair County, IAborders it9872.4%9.3 pCi/L+13.9 points
Greene County, IAborders it14371.3%6.2 pCi/L+12.8 points
Guthrie County, IAborders it25770.8%6.9 pCi/L+12.3 points
Boone County, IAborders it1,13468.7%6.0 pCi/L+10.2 points
Warren County, IAborders it1,51366.0%6.3 pCi/L+7.5 points
Polk County, IAborders it10,94564.4%5.6 pCi/L+5.9 points
Madison County, IAborders it31862.3%6.0 pCi/L+3.8 points
Where Dallas County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultDallas County testsDallas County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L48620.7%21.8%39.6%−1.1 points
2 to 4 pCi/L48920.8%19.7%24.7%+1.1 points
4 pCi/L and above1,37758.5%58.5%35.7%Level
Dallas 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
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
Cerro Gordo County70 of 991,66259.0%4.8 pCi/L
Dallas County71 of 992,35258.5%4.9 pCi/L
Pottawattamie County72 of 991,86857.4%4.7 pCi/L
Washington County73 of 991,18654.9%4.6 pCi/L
Bremer County74 of 9995753.0%4.3 pCi/L
Jackson County75 of 991,05652.7%4.1 pCi/L
Clinton County76 of 991,37552.7%4.3 pCi/L
Dallas County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 20172,35258.5%4.9 pCi/L103.9 pCi/L58.5%−0.3 points
2007 to 20162,14758.8%4.9 pCi/L103.9 pCi/L58.6%+0.3 points
2006 to 20151,97758.5%4.9 pCi/L103.9 pCi/L59.4%−1.5 points
2005 to 20141,64660.0%5.1 pCi/L103.9 pCi/L59.6%First on file

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

Dallas County, Geology

The ground under Dallas County

Predicted

USGS's geologic map puts all of Dallas County's mapped land in one class: high radon potential. The map puts 82.4% of Dallas County in the area it calls Des Moines Lobe and 17.6% 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 Dallas County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Des Moines LobeCalcareous loamy till derived from shale, limestone, dolomite, sandstone.High1282.4%
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1317.6%

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

Dallas County beside the ground around it

On high-potential ground Dallas 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; Adair County comes nearest at 100%.

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

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

Local help

Dallas County, Local resources

Radon testing and mitigation in Dallas County

Listed radon businesses with an address in Dallas County:

Listed radon professionals by town: West Des Moines, Urbandale, Waukee, Clive, Adel

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

Dallas County, Questions

Questions about radon in Dallas County

Are radon levels high in Dallas County?

Over the 2008 to 2017 laboratory totals, 58.5% of the radon tests reported to CDC for Dallas County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.9 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 70 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Dallas County?

Dallas County borders 7 counties: Boone County, Guthrie County, Polk County, Madison County, Greene County, Warren County and Adair County.

Products

Dallas County, Products

Testing a home in Dallas County

In Dallas County, 58.5% of 2,352 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 Dallas 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

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

Explore

Dallas County, Bordering counties

Counties bordering Dallas County

Calculated by Radon411

Dallas County, Cities and towns

Cities and towns in Dallas County

Dallas County is growing: the Census Bureau puts it at 118,457 residents on July 1, 2025, up 17.8% from 100,521 in 2020. That works out to 201 people per square mile of land. West Des Moines, the largest place on its list (74,224 residents in all), extends beyond Dallas County, so no share of the total is worked out for it. CDC's 2,352 reported tests for 2008 to 2017 work out to 19.9 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From West Des Moines to Dawson, CDC publishes no figure by town: each reads Dallas County's.

The 12 largest cities and towns in Dallas County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
West Des Moinesextends beyond Dallas County74,224+7.6%Counted whole
Urbandaleextends beyond Dallas County48,570+6.5%Counted whole
Waukee34,890+44.3%29.5%
Cliveextends beyond Dallas County19,861+6.3%Counted whole
Grimesextends beyond Dallas County17,405+10.7%Counted whole
Perry8,208+4.1%6.9%
Adel7,098+14.6%6.0%
Grangerextends beyond Dallas County2,179+25.4%Counted whole
Dallas Center2,042+7.0%1.7%
Van Meter1,978+32.2%1.7%
Woodwardextends beyond Dallas County1,426+5.4%Counted whole
De Soto976+5.7%0.8%
  • Redfield
  • Dexter
  • Minburn
  • Linden
  • Bouton
  • Dawson

18 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 Dallas County is counted whole, so it has no share.

Dallas County, Homes

Homes in Dallas County

Of Dallas County's 43,195 homes, 63% are detached houses, against 72% across Iowa; 22% are in buildings of five or more homes. Much of Dallas County is recent building: 63% of its homes have gone up since 2000 and the middle year built is 2005, against 1971 for Iowa. 69% 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 Dallas County, Iowa, 2019 to 2023
HomesDallas CountyIowa
Housing units43,1951,427,175
Detached houses63%72%
In buildings of 5 or more22%14%
Mobile homes2%3%
Built before 196014%39%
Built since 200063%21%
Middle year built20051971
Owner-occupied69%72%

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