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Radon Levels in Humboldt County, Iowa

EPA puts Humboldt County in Zone 1, its highest radon zone, and high results are common there: 70.1% of the 385 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

    70.1%

    11.6 pts above IA

    Humboldt
    70.1%
    Iowa
    58.5%

    385 tests, 2008 to 2017

  • Median result

    7.0pCi/L

    Action level reached

    Humboldt
    7.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    385

    61st of 99 by tests

    Humboldt
    385
    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

    30 of 99

    Middle half

    Humboldt
    70.1%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Humboldt County

Starts at Humboldt County's median, 7.0 pCi/L

7.0pCi/L

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

EPA’s reading of 7.0 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. Humboldt County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Humboldt County, At a glance

Humboldt County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Humboldt County, 2008 to 2017, laboratory
Under 2 pCi/L: 15%2 to 4 pCi/L: 15%4 pCi/L and above: 70%

Of 385 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Humboldt County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L5915.3%
2 to 4 pCi/L5614.5%
4 pCi/L and above27070.1%
What these figures count

These are the 385 tests reported to CDC for Humboldt 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

Humboldt County, Compared

Humboldt County radon figures, compared

Calculated by Radon411

More than half: 70.1% of the 385 radon tests reported to CDC for Humboldt County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 30th of 99 Iowa counties with 30 or more tests for the same period. That is 11.6 points above the 58.5% pooled from 99 Iowa counties.

The median result, 7.0 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 116.0 pCi/L. The rest split 15.3% under 2 pCi/L and 14.5% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 70.1% share point the same way here.

1 of its 6 bordering counties with figures ran higher, led by Palo Alto County at 70.8%; Hancock County reported 64.5%. 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 Humboldt County went from 245 tests (2005 to 2014) to 385 (2008 to 2017), the share going from 62.4% to 70.1%.

Nationally, every county with a figure for the same period pools to 35.7%; Humboldt County sits 34.4 points above it. CDC also counts 39 tests taken after mitigation in Humboldt County for the same period: tests in homes where a fix was already in.

Humboldt County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Humboldt County
Humboldt County38570.1%7.0 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−11.6 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−34.4 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+14.1 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−44.2 points
Palo Alto County, IAborders it46270.8%5.9 pCi/L+0.7 points
Webster County, IAborders it1,18969.4%6.5 pCi/L−0.7 points
Pocahontas County, IAborders it41768.8%6.4 pCi/L−1.3 points
Wright County, IAborders it29266.8%6.2 pCi/L−3.3 points
Kossuth County, IAborders it43466.1%5.7 pCi/L−4.0 points
Hancock County, IAborders it64064.5%5.5 pCi/L−5.6 points
Where Humboldt County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultHumboldt County testsHumboldt County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L5915.3%21.8%39.6%−6.5 points
2 to 4 pCi/L5614.5%19.7%24.7%−5.2 points
4 pCi/L and above27070.1%58.5%35.7%+11.6 points
Humboldt 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
Palo Alto County25 of 9946270.8%5.9 pCi/L
Mitchell County26 of 9944470.7%6.4 pCi/L
Poweshiek County27 of 9941970.6%7.2 pCi/L
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
Humboldt County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201738570.1%7.0 pCi/L116.0 pCi/L58.5%−0.9 points
2007 to 201635971.0%7.0 pCi/L116.0 pCi/L58.6%+2.5 points
2006 to 201533668.5%6.7 pCi/L116.0 pCi/L59.4%+6.1 points
2005 to 201424562.4%5.9 pCi/L116.0 pCi/L59.6%First on file

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

Humboldt County, Geology

The ground under Humboldt County

Predicted

USGS's geologic map puts all of Humboldt County's mapped land in one class: high radon potential. All of it lies in the area the map calls Des Moines Lobe, to which USGS gives a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Humboldt County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Des Moines LobeCalcareous loamy till derived from shale, limestone, dolomite, sandstone.High12100%

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

Humboldt County beside the ground around it

On high-potential ground Humboldt 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; Hancock County comes nearest at 100%.

Share of land by USGS radon potential: Humboldt County, the 6 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Humboldt CountyZone 1NoneNone100%
Kossuth CountyZone 1NoneNone100%
Pocahontas CountyZone 1NoneNone100%
Wright CountyZone 1NoneNone100%
Webster CountyZone 1NoneNone100%
Palo Alto CountyZone 1NoneNone100%
Hancock CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Humboldt County, Local resources

Radon testing and mitigation in Humboldt County

Listed radon businesses with an address in Humboldt County:

Listed radon professionals by town: Humboldt

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

Humboldt County, Questions

Questions about radon in Humboldt County

Are radon levels high in Humboldt County?

Over the 2008 to 2017 laboratory totals, 70.1% of the radon tests reported to CDC for Humboldt County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 7.0 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 29 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Humboldt County?

Humboldt County borders 6 counties: Kossuth County, Pocahontas County, Wright County, Webster County, Palo Alto County and Hancock County.

Products

Humboldt County, Products

Testing a home in Humboldt County

In Humboldt County, 70.1% of 385 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 Humboldt 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

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

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Humboldt County, Bordering counties

Counties bordering Humboldt County

Calculated by Radon411

Humboldt County, Cities and towns

Cities and towns in Humboldt County

About 9,409 people live in Humboldt County by the Census Bureau's estimate for July 1, 2025, 190 fewer than in 2020 (−2.0%). That works out to 22 people per square mile of land. Its largest town, Humboldt, has 4,675 residents, 49.7% of the total. CDC's 385 reported tests for 2008 to 2017 work out to 40.9 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

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

The 12 largest cities and towns in Humboldt County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Humboldt4,675−2.4%49.7%
Dakota City747−1.6%7.9%
Gilmore Cityextends beyond Humboldt County471−2.9%Counted whole
Livermore374−2.1%4.0%
Bode298−2.6%3.2%
Lu Verneextends beyond Humboldt County246−3.1%Counted whole
Renwick222−2.6%2.4%
Thor177−1.1%1.9%
Rutland115−1.7%1.2%
Bradgate73−2.7%0.8%
Hardy53−1.9%0.6%
Ottosen39−2.5%0.4%
  • Pioneer

13 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 Humboldt County is counted whole, so it has no share.

Humboldt County, Homes

Homes in Humboldt County

Humboldt County is a place of houses on their own lots: 84% of its 4,600 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1958 (1971 for Iowa), and 52% date from before 1960. Owners live in 75% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Humboldt County, Iowa, 2019 to 2023
HomesHumboldt CountyIowa
Housing units4,6001,427,175
Detached houses84%72%
In buildings of 5 or more9%14%
Mobile homes2%3%
Built before 196052%39%
Built since 200011%21%
Middle year built19581971
Owner-occupied75%72%

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