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Radon Levels in Audubon County, Iowa

EPA puts Audubon County in Zone 1, its highest radon zone, and high results are common there: 78.3% of the 189 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

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  • Share at 4+ pCi/L

    78.3%

    19.8 pts above IA

    Audubon
    78.3%
    Iowa
    58.5%

    189 tests, 2008 to 2017

  • Median result

    9.5pCi/L

    Action level reached

    Audubon
    9.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    189

    82nd of 99 by tests

    Audubon
    189
    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

    6 of 99

    Top quarter

    Audubon
    78.3%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Audubon County

Starts at Audubon County's median, 9.5 pCi/L

9.5pCi/L

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

EPA’s reading of 9.5 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. Audubon County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Audubon County, At a glance

Audubon County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Audubon County, 2008 to 2017, laboratory
Under 2 pCi/L: 11%2 to 4 pCi/L: 11%4 pCi/L and above: 78%

Of 189 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Audubon County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2010.6%
2 to 4 pCi/L2111.1%
4 pCi/L and above14878.3%
What these figures count

These are the 189 tests reported to CDC for Audubon 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

Audubon County, Compared

Audubon County radon figures, compared

Calculated by Radon411

More than half: 78.3% of the 189 radon tests reported to CDC for Audubon County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 6th of 99 Iowa counties with 30 or more tests for the same period. That is 19.8 points above the 58.5% pooled from 99 Iowa counties.

The median result, 9.5 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 47.7 pCi/L. The rest split 10.6% under 2 pCi/L and 11.1% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 78.3% share point the same way here.

1 of its 6 bordering counties with figures ran higher, led by Shelby County at 78.4%; Guthrie County reported 70.8%. 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 Audubon County went from 148 tests (2005 to 2014) to 189 (2008 to 2017), the share going from 77.7% to 78.3%.

Nationally, every county with a figure for the same period pools to 35.7%; Audubon County sits 42.6 points above it. CDC also counts 18 tests taken after mitigation in Audubon County for the same period: tests in homes where a fix was already in.

Audubon County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Audubon County
Audubon County18978.3%9.5 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−19.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−42.6 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+5.9 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−52.4 points
Shelby County, IAborders it85778.4%9.0 pCi/L+0.1 points
Carroll County, IAborders it59477.6%7.8 pCi/L−0.7 points
Cass County, IAborders it32777.4%8.1 pCi/L−0.9 points
Crawford County, IAborders it37374.8%7.0 pCi/L−3.5 points
Adair County, IAborders it9872.4%9.3 pCi/L−5.9 points
Guthrie County, IAborders it25770.8%6.9 pCi/L−7.5 points
Where Audubon County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultAudubon County testsAudubon County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L2010.6%21.8%39.6%−11.2 points
2 to 4 pCi/L2111.1%19.7%24.7%−8.6 points
4 pCi/L and above14878.3%58.5%35.7%+19.8 points
Audubon 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
Sioux County1 of 991,98284.2%10.7 pCi/L
Plymouth County2 of 991,40582.3%8.6 pCi/L
O'Brien County3 of 9965281.7%8.9 pCi/L
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
Audubon County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201718978.3%9.5 pCi/L47.7 pCi/L58.5%+1.3 points
2007 to 201618377.0%9.2 pCi/L47.7 pCi/L58.6%−1.2 points
2006 to 201517478.2%9.4 pCi/L47.7 pCi/L59.4%+0.5 points
2005 to 201414877.7%9.1 pCi/L47.2 pCi/L59.6%First on file

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

Audubon County, Geology

The ground under Audubon County

Predicted

USGS's geologic map puts all of Audubon 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 Audubon 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.

Audubon County beside the ground around it

On high-potential ground Audubon County is close to Iowa as a whole: 100% of its land against 98.8%. Of the 6 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: Audubon County, the 6 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Audubon CountyZone 1NoneNone100%
Guthrie CountyZone 1NoneNone100%
Shelby CountyZone 1NoneNone100%
Carroll CountyZone 1NoneNone100%
Cass CountyZone 1NoneNone100%
Crawford 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

Audubon County, Local resources

Radon testing and mitigation in Audubon County

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

Audubon County, Questions

Questions about radon in Audubon County

Are radon levels high in Audubon County?

Over the 2008 to 2017 laboratory totals, 78.3% of the radon tests reported to CDC for Audubon County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 9.5 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Audubon County?

Audubon County borders 6 counties: Guthrie County, Shelby County, Carroll County, Cass County, Crawford County and Adair County.

Products

Audubon County, Products

Testing a home in Audubon County

In Audubon County, 78.3% of 189 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 Audubon 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

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

Explore

Audubon County, Bordering counties

Counties bordering Audubon County

Calculated by Radon411

Audubon County, Cities and towns

Cities and towns in Audubon County

About 5,509 people live in Audubon County by the Census Bureau's estimate for July 1, 2025, 171 fewer than in 2020 (−3.0%). That works out to 12 people per square mile of land. Its largest town, Audubon, has 1,989 residents, 36.1% of the total. Together its 5 incorporated places hold 58.6% of those residents; the other 41.4% live outside any of them. CDC's 189 reported tests for 2008 to 2017 work out to 34.3 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Audubon to Gray, CDC publishes no figure by town: each reads Audubon County's.

The cities and towns in Audubon County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Audubon1,989−3.4%36.1%
Exira767−3.2%13.9%
Kimballton277−4.5%5.0%
Brayton136−4.9%2.5%
Gray59Level1.1%

5 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).

Audubon County, Homes

Homes in Audubon County

Audubon County is a place of houses on their own lots: 93% of its 2,786 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1950 (1971 for Iowa), and 64% date from before 1960. Owners live in 76% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Audubon County, Iowa, 2019 to 2023
HomesAudubon CountyIowa
Housing units2,7861,427,175
Detached houses93%72%
In buildings of 5 or more2%14%
Mobile homes1%3%
Built before 196064%39%
Built since 20007%21%
Middle year built19501971
Owner-occupied76%72%

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