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Radon Levels in Fremont County, Iowa

EPA puts Fremont County in Zone 1, its highest radon zone, and high results are common there: 69.8% of the 205 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

    69.8%

    11.3 pts above IA

    Fremont
    69.8%
    Iowa
    58.5%

    205 tests, 2008 to 2017

  • Median result

    7.2pCi/L

    Action level reached

    Fremont
    7.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    205

    81st of 99 by tests

    Fremont
    205
    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

    33 of 99

    Middle half

    Fremont
    69.8%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Fremont County

Starts at Fremont County's median, 7.2 pCi/L

7.2pCi/L

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

EPA’s reading of 7.2 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. Fremont County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Fremont County, At a glance

Fremont County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Fremont County, 2008 to 2017, laboratory
Under 2 pCi/L: 13%2 to 4 pCi/L: 17%4 pCi/L and above: 70%

Of 205 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Fremont County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2713.2%
2 to 4 pCi/L3517.1%
4 pCi/L and above14369.8%
What these figures count

These are the 205 tests reported to CDC for Fremont 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

Fremont County, Compared

Fremont County radon figures, compared

Calculated by Radon411

More than half: 69.8% of the 205 radon tests reported to CDC for Fremont County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 33rd of 99 Iowa counties with 30 or more tests for the same period. That is 11.3 points above the 58.5% pooled from 99 Iowa counties.

The median result, 7.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 44.3 pCi/L. The rest split 13.2% under 2 pCi/L and 17.1% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 69.8% share point the same way here.

4 of its 6 bordering counties with figures ran higher, led by Page County at 71.7%; Cass County, NE reported 66.0%. 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 Fremont County went from 127 tests (2005 to 2014) to 205 (2008 to 2017), the share going from 76.4% to 69.8%.

Nationally, every county with a figure for the same period pools to 35.7%; Fremont County sits 34.1 points above it. CDC also counts 17 tests taken after mitigation in Fremont County for the same period: tests in homes where a fix was already in.

Fremont County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Fremont County
Fremont County20569.8%7.2 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−11.3 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−34.1 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+14.4 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−43.9 points
Page County, IAborders it65371.7%7.2 pCi/L+1.9 points
Mills County, IAborders it46570.1%6.1 pCi/L+0.3 points
Otoe County, NEborders it40269.9%6.5 pCi/L+0.1 points
Atchison County, MOborders it10369.9%5.6 pCi/L+0.1 points
Montgomery County, IAborders it23367.4%6.1 pCi/L−2.4 points
Cass County, NEborders it62066.0%6.3 pCi/L−3.8 points
Where Fremont County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultFremont County testsFremont County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L2713.2%21.8%39.6%−8.6 points
2 to 4 pCi/L3517.1%19.7%24.7%−2.6 points
4 pCi/L and above14369.8%58.5%35.7%+11.3 points
Fremont 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
Dickinson County28 of 9983170.3%7.0 pCi/L
Marshall County29 of 9957070.2%8.2 pCi/L
Humboldt County30 of 9938570.1%7.0 pCi/L
Mills County31 of 9946570.1%6.1 pCi/L
Calhoun County32 of 9950769.8%6.1 pCi/L
Fremont County33 of 9920569.8%7.2 pCi/L
Harrison County34 of 9936769.8%6.2 pCi/L
Webster County35 of 991,18969.4%6.5 pCi/L
Woodbury County36 of 993,54169.2%6.1 pCi/L
Pocahontas County37 of 9941768.8%6.4 pCi/L
Boone County38 of 991,13468.7%6.0 pCi/L
Fremont County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201720569.8%7.2 pCi/L44.3 pCi/L58.5%−2.6 points
2007 to 201618172.4%8.2 pCi/L44.3 pCi/L58.6%−1.2 points
2006 to 201514873.6%8.7 pCi/L53.9 pCi/L59.4%−2.8 points
2005 to 201412776.4%8.8 pCi/L53.9 pCi/L59.6%First on file

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

Fremont County, Geology

The ground under Fremont County

Predicted

USGS's geologic map puts all of Fremont 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 Fremont County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1399.7%

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

Fremont County beside the ground around it

On high-potential ground Fremont 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; Cass County, NE comes nearest at 100%.

Share of land by USGS radon potential: Fremont County, the 6 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Fremont CountyZone 1NoneNone100%
Mills CountyZone 1NoneNone100%
Atchison County, MOZone 1NoneNone100%
Page CountyZone 1NoneNone100%
Otoe County, NEZone 1NoneNone100%
Cass County, NEZone 1NoneNone100%
Montgomery CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Fremont County, Local resources

Radon testing and mitigation in Fremont 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

Fremont County, Questions

Questions about radon in Fremont County

Are radon levels high in Fremont County?

Over the 2008 to 2017 laboratory totals, 69.8% of the radon tests reported to CDC for Fremont County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 7.2 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 32 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Fremont County?

Fremont County borders 6 counties: Mills County, IA, Atchison County, MO, Page County, IA, Otoe County, NE, Cass County, NE and Montgomery County, IA.

Products

Fremont County, Products

Testing a home in Fremont County

In Fremont County, 69.8% of 205 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 Fremont 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

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

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Fremont County, Bordering counties

Counties bordering Fremont County

Calculated by Radon411

Fremont County, Cities and towns

Cities and towns in Fremont County

About 6,522 people live in Fremont County by the Census Bureau's estimate for July 1, 2025, 53 fewer than in 2020 (−0.8%). That works out to 13 people per square mile of land. Shenandoah, the largest place on its list (4,808 residents in all), extends beyond Fremont County, so no share of the total is worked out for it. CDC's 205 reported tests for 2008 to 2017 work out to 31.4 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Shenandoah to Imogene, CDC publishes no figure by town: each reads Fremont County's.

The cities and towns in Fremont County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Shenandoahextends beyond Fremont County4,808−2.3%Counted whole
Sidney1,051−1.5%16.1%
Taborextends beyond Fremont County985−2.2%Counted whole
Hamburg866−1.7%13.3%
Farragut481−1.2%7.4%
Riverton243−2.0%3.7%
Randolph186−1.6%2.9%
Thurman163Level2.5%
Imogene37−2.6%0.6%

9 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 Fremont County is counted whole, so it has no share.

Fremont County, Homes

Homes in Fremont County

Fremont County is a place of houses on their own lots: 92% of its 3,130 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1957 (1971 for Iowa), and 52% date from before 1960. Owners live in 81% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Fremont County, Iowa, 2019 to 2023
HomesFremont CountyIowa
Housing units3,1301,427,175
Detached houses92%72%
In buildings of 5 or more1%14%
Mobile homes2%3%
Built before 196052%39%
Built since 200012%21%
Middle year built19571971
Owner-occupied81%72%

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