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Radon Levels in Cass County, Iowa

EPA puts Cass County in Zone 1, its highest radon zone, and high results are common there: 77.4% of the 327 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

    77.4%

    18.9 pts above IA

    Cass
    77.4%
    Iowa
    58.5%

    327 tests, 2008 to 2017

  • Median result

    8.1pCi/L

    Action level reached

    Cass
    8.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    327

    68th of 99 by tests

    Cass
    327
    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

    9 of 99

    Top quarter

    Cass
    77.4%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Cass County

Starts at Cass County's median, 8.1 pCi/L

8.1pCi/L

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

EPA’s reading of 8.1 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. Cass County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Cass County, At a glance

Cass County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Cass County, 2008 to 2017, laboratory
Under 2 pCi/L: 12%2 to 4 pCi/L: 11%4 pCi/L and above: 77%

Of 327 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Cass County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L3811.6%
2 to 4 pCi/L3611.0%
4 pCi/L and above25377.4%
What these figures count

These are the 327 tests reported to CDC for Cass 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

Cass County, Compared

Cass County radon figures, compared

Calculated by Radon411

More than half: 77.4% of the 327 radon tests reported to CDC for Cass County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 9th of 99 Iowa counties with 30 or more tests for the same period. That is 18.9 points above the 58.5% pooled from 99 Iowa counties.

The median result, 8.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 60.8 pCi/L. The rest split 11.6% under 2 pCi/L and 11.0% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 77.4% share point the same way here.

2 of its 7 bordering counties with figures ran higher, led by Shelby County at 78.4%; Pottawattamie County reported 57.4%. 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 Cass County went from 190 tests (2005 to 2014) to 327 (2008 to 2017), the share going from 78.4% to 77.4%.

Nationally, every county with a figure for the same period pools to 35.7%; Cass County sits 41.7 points above it. CDC also counts 32 tests taken after mitigation in Cass County for the same period: tests in homes where a fix was already in.

Cass County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Cass County
Cass County32777.4%8.1 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−18.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−41.7 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+6.8 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−51.5 points
Shelby County, IAborders it85778.4%9.0 pCi/L+1.0 points
Audubon County, IAborders it18978.3%9.5 pCi/L+0.9 points
Adair County, IAborders it9872.4%9.3 pCi/L−5.0 points
Guthrie County, IAborders it25770.8%6.9 pCi/L−6.6 points
Montgomery County, IAborders it23367.4%6.1 pCi/L−10.0 points
Adams County, IAborders it8165.4%6.1 pCi/L−12.0 points
Pottawattamie County, IAborders it1,86857.4%4.7 pCi/L−20.0 points
Where Cass County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultCass County testsCass County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L3811.6%21.8%39.6%−10.2 points
2 to 4 pCi/L3611.0%19.7%24.7%−8.7 points
4 pCi/L and above25377.4%58.5%35.7%+18.9 points
Cass 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
Clay County4 of 9974479.4%9.6 pCi/L
Shelby County5 of 9985778.4%9.0 pCi/L
Audubon County6 of 9918978.3%9.5 pCi/L
Lyon County7 of 9923777.6%8.3 pCi/L
Carroll County8 of 9959477.6%7.8 pCi/L
Cass County9 of 9932777.4%8.1 pCi/L
Sac County10 of 9949176.6%7.0 pCi/L
Crawford County11 of 9937374.8%7.0 pCi/L
Monona County12 of 9960374.6%7.0 pCi/L
Cherokee County13 of 9979574.5%7.6 pCi/L
Franklin County14 of 9931373.5%6.2 pCi/L
Cass County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201732777.4%8.1 pCi/L60.8 pCi/L58.5%−1.0 points
2007 to 201630178.4%8.7 pCi/L60.8 pCi/L58.6%+1.3 points
2006 to 201524577.1%8.7 pCi/L60.8 pCi/L59.4%−1.3 points
2005 to 201419078.4%9.8 pCi/L60.8 pCi/L59.6%First on file

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

Cass County, Geology

The ground under Cass County

Predicted

USGS's geologic map puts all of Cass County's mapped land in one class: high radon potential. All of it lies in the area the map calls Loess-Covered Drift Plains, to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Cass County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High13100%

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

Cass County beside the ground around it

On high-potential ground Cass 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: Cass County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Cass CountyZone 1NoneNone100%
Audubon CountyZone 1NoneNone100%
Adair CountyZone 1NoneNone100%
Montgomery CountyZone 1NoneNone100%
Adams CountyZone 1NoneNone100%
Shelby CountyZone 1NoneNone100%
Guthrie CountyZone 1NoneNone100%
Pottawattamie CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Cass County, Local resources

Radon testing and mitigation in Cass County

Listed radon businesses with an address in Cass County:

Listed radon professionals by town: Anita

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

Cass County, Questions

Questions about radon in Cass County

Are radon levels high in Cass County?

Over the 2008 to 2017 laboratory totals, 77.4% of the radon tests reported to CDC for Cass County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 8.1 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 8 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Cass County?

Cass County borders 7 counties: Audubon County, Adair County, Montgomery County, Adams County, Shelby County, Guthrie County and Pottawattamie County.

Products

Cass County, Products

Testing a home in Cass County

In Cass County, 77.4% of 327 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 Cass 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

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

Explore

Cass County, Bordering counties

Counties bordering Cass County

Calculated by Radon411

Cass County, Cities and towns

Cities and towns in Cass County

About 12,960 people live in Cass County by the Census Bureau's estimate for July 1, 2025, 158 fewer than in 2020 (−1.2%). That works out to 23 people per square mile of land. Atlantic alone is home to 6,676 of them, 51.5% of the total. Together its 8 incorporated places hold 75.2% of those residents; the other 24.8% live outside any of them. CDC's 327 reported tests for 2008 to 2017 work out to 25.2 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Atlantic to Wiota, CDC publishes no figure by town: each reads Cass County's.

The cities and towns in Cass County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Atlantic6,676−1.5%51.5%
Griswold972−1.8%7.5%
Anita949−1.2%7.3%
Lewis354−1.1%2.7%
Massena351−1.4%2.7%
Cumberland247−0.4%1.9%
Marne108Level0.8%
Wiota92Level0.7%

8 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).

Cass County, Homes

Homes in Cass County

Cass County is a place of houses on their own lots: 80% of its 6,397 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1954 (1971 for Iowa), and 58% date from before 1960. 72% 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 Cass County, Iowa, 2019 to 2023
HomesCass CountyIowa
Housing units6,3971,427,175
Detached houses80%72%
In buildings of 5 or more9%14%
Mobile homes3%3%
Built before 196058%39%
Built since 20006%21%
Middle year built19541971
Owner-occupied72%72%

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