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Radon Levels in Osceola County, Iowa

EPA puts Osceola County in Zone 1, its highest radon zone, and high results are common there: 67.2% of the 122 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

    67.2%

    8.7 pts above IA

    Osceola
    67.2%
    Iowa
    58.5%

    122 tests, 2008 to 2017

  • Median result

    6.8pCi/L

    Action level reached

    Osceola
    6.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    122

    87th of 99 by tests

    Osceola
    122
    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

    43 of 99

    Middle half

    Osceola
    67.2%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Osceola County

Starts at Osceola County's median, 6.8 pCi/L

6.8pCi/L

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

EPA’s reading of 6.8 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. Osceola County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Osceola County, At a glance

Osceola County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Osceola County, 2008 to 2017, laboratory
Under 2 pCi/L: 10%2 to 4 pCi/L: 23%4 pCi/L and above: 67%

Of 122 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Osceola County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L129.8%
2 to 4 pCi/L2823.0%
4 pCi/L and above8267.2%
What these figures count

These are the 122 tests reported to CDC for Osceola 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

Osceola County, Compared

Osceola County radon figures, compared

Calculated by Radon411

More than half: 67.2% of the 122 radon tests reported to CDC for Osceola County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 43rd of 99 Iowa counties with 30 or more tests for the same period. That is 8.7 points above the 58.5% pooled from 99 Iowa counties.

The median result, 6.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 34.9 pCi/L. The rest split 9.8% under 2 pCi/L and 23.0% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 67.2% share point the same way here.

All 7 of its bordering counties with figures ran higher, led by Sioux County at 84.2%; the lowest of them, Jackson County, MN, reported 69.8%. 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 Osceola County went from 110 tests (2005 to 2014) to 122 (2008 to 2017), the share going from 74.5% to 67.2%.

Nationally, every county with a figure for the same period pools to 35.7%; Osceola County sits 31.5 points above it.

Osceola County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Osceola County
Osceola County12267.2%6.8 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−8.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−31.5 points
Plymouth Countyhighest in the state1,40582.3%8.6 pCi/L+15.1 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−41.3 points
Sioux County, IAborders it1,98284.2%10.7 pCi/L+17.0 points
O'Brien County, IAborders it65281.7%8.9 pCi/L+14.5 points
Clay County, IAborders it74479.4%9.6 pCi/L+12.2 points
Lyon County, IAborders it23777.6%8.3 pCi/L+10.4 points
Nobles County, MNborders it26770.4%7.0 pCi/L+3.2 points
Dickinson County, IAborders it83170.3%7.0 pCi/L+3.1 points
Jackson County, MNborders it39469.8%6.8 pCi/L+2.6 points
Where Osceola County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultOsceola County testsOsceola County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L129.8%21.8%39.6%−12.0 points
2 to 4 pCi/L2823.0%19.7%24.7%+3.3 points
4 pCi/L and above8267.2%58.5%35.7%+8.7 points
Osceola 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
Boone County38 of 991,13468.7%6.0 pCi/L
Tama County39 of 9933367.9%7.0 pCi/L
Worth County40 of 9915467.5%6.0 pCi/L
Montgomery County41 of 9923367.4%6.1 pCi/L
Marion County42 of 991,15167.3%6.0 pCi/L
Osceola County43 of 9912267.2%6.8 pCi/L
Grundy County44 of 9950166.9%6.9 pCi/L
Wright County45 of 9929266.8%6.2 pCi/L
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
Osceola County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201712267.2%6.8 pCi/L34.9 pCi/L58.5%−3.6 points
2007 to 201613070.8%7.2 pCi/L34.9 pCi/L58.6%−1.2 points
2006 to 201512572.0%7.5 pCi/L34.9 pCi/L59.4%−2.5 points
2005 to 201411074.5%7.7 pCi/L34.9 pCi/L59.6%First on file

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

Osceola County, Geology

The ground under Osceola County

Predicted

USGS's geologic map puts all of Osceola County's mapped land in one class: high radon potential. The map puts 52.0% of Osceola County in the area it calls Loess-Covered Drift Plains and 48.0% in Des Moines Lobe. USGS gives the first a radon index of 13 and the second 12, both in the high band (12 to 17).

USGS's geologic areas under Osceola County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1352.0%
Des Moines LobeCalcareous loamy till derived from shale, limestone, dolomite, sandstone.High1248.0%

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

Osceola County beside the ground around it

On high-potential ground Osceola 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; Clay County comes nearest at 100%.

Share of land by USGS radon potential: Osceola County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Osceola CountyZone 1NoneNone100%
O'Brien CountyZone 1NoneNone100%
Nobles County, MNZone 1NoneNone100%
Dickinson CountyZone 1NoneNone100%
Lyon CountyZone 1NoneNone100%
Jackson County, MNZone 1NoneNone100%
Clay CountyZone 1NoneNone100%
Sioux CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Osceola County, Local resources

Radon testing and mitigation in Osceola 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

Osceola County, Questions

Questions about radon in Osceola County

Are radon levels high in Osceola County?

Over the 2008 to 2017 laboratory totals, 67.2% of the radon tests reported to CDC for Osceola County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.8 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 42 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Osceola County?

Osceola County borders 7 counties: O'Brien County, IA, Nobles County, MN, Dickinson County, IA, Lyon County, IA, Jackson County, MN, Clay County, IA and Sioux County, IA.

Products

Osceola County, Products

Testing a home in Osceola County

In Osceola County, 67.2% of 122 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 Osceola 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

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

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Osceola County, Bordering counties

Counties bordering Osceola County

Calculated by Radon411

Osceola County, Cities and towns

Cities and towns in Osceola County

About 5,980 people live in Osceola County by the Census Bureau's estimate for July 1, 2025, 221 fewer than in 2020 (−3.6%). That works out to 15 people per square mile of land. Its largest town, Sibley, has 2,762 residents, 46.2% of the total. Together its 5 incorporated places hold 66.0% of those residents; the other 34.0% live outside any of them. CDC's 122 reported tests for 2008 to 2017 work out to 20.4 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Sibley to Harris, CDC publishes no figure by town: each reads Osceola County's.

The cities and towns in Osceola County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Sibley2,762−3.6%46.2%
Ashton428−4.7%7.2%
Ocheyedan419−4.3%7.0%
Melvin194−3.5%3.2%
Harris146−3.3%2.4%

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).

Osceola County, Homes

Homes in Osceola County

Osceola County is a place of houses on their own lots: 86% of its 2,867 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 59% date from before 1960. Owners live in 78% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Osceola County, Iowa, 2019 to 2023
HomesOsceola CountyIowa
Housing units2,8671,427,175
Detached houses86%72%
In buildings of 5 or more8%14%
Mobile homes1%3%
Built before 196059%39%
Built since 200010%21%
Middle year built19541971
Owner-occupied78%72%

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