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Radon Levels in Howard County, Iowa

EPA puts Howard County in Zone 1, its highest radon zone, and high results are common there: 61.3% of the 388 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

    61.3%

    2.8 pts above IA

    Howard
    61.3%
    Iowa
    58.5%

    388 tests, 2008 to 2017

  • Median result

    5.9pCi/L

    Action level reached

    Howard
    5.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    388

    60th of 99 by tests

    Howard
    388
    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

    59 of 99

    Middle half

    Howard
    61.3%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Howard County

Starts at Howard County's median, 5.9 pCi/L

5.9pCi/L

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

EPA’s reading of 5.9 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. Howard County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Howard County, At a glance

Howard County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Howard County, 2008 to 2017, laboratory
Under 2 pCi/L: 18%2 to 4 pCi/L: 21%4 pCi/L and above: 61%

Of 388 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Howard County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L7118.3%
2 to 4 pCi/L7920.4%
4 pCi/L and above23861.3%
What these figures count

These are the 388 tests reported to CDC for Howard 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

Howard County, Compared

Howard County radon figures, compared

Calculated by Radon411

More than half: 61.3% of the 388 radon tests reported to CDC for Howard County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 59th of 99 Iowa counties with 30 or more tests for the same period. That is 2.8 points above the 58.5% pooled from 99 Iowa counties.

The median result, 5.9 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 122.7 pCi/L. The rest split 18.3% under 2 pCi/L and 20.4% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 61.3% share point the same way here.

3 of its 6 bordering counties with figures ran higher, led by Mitchell County at 70.7%; Mower County, MN reported 48.2%. 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 Howard County went from 411 tests (2005 to 2014) to 388 (2008 to 2017), the share going from 62.5% to 61.3%.

Nationally, every county with a figure for the same period pools to 35.7%; Howard County sits 25.6 points above it. CDC also counts 41 tests taken after mitigation in Howard County for the same period: tests in homes where a fix was already in.

Howard County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Howard County
Howard County38861.3%5.9 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−2.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−25.6 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+22.9 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−35.4 points
Mitchell County, IAborders it44470.7%6.4 pCi/L+9.4 points
Winneshiek County, IAborders it1,07166.4%6.2 pCi/L+5.1 points
Fillmore County, MNborders it1,24264.1%6.1 pCi/L+2.8 points
Floyd County, IAborders it69759.5%5.1 pCi/L−1.8 points
Chickasaw County, IAborders it49859.0%4.9 pCi/L−2.3 points
Mower County, MNborders it50048.2%3.8 pCi/L−13.1 points
Where Howard County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultHoward County testsHoward County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L7118.3%21.8%39.6%−3.5 points
2 to 4 pCi/L7920.4%19.7%24.7%+0.7 points
4 pCi/L and above23861.3%58.5%35.7%+2.8 points
Howard 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
Fayette County54 of 9974662.7%5.6 pCi/L
Clayton County55 of 9931062.6%5.8 pCi/L
Madison County56 of 9931862.3%6.0 pCi/L
Benton County57 of 9969662.1%5.6 pCi/L
Union County58 of 9913161.8%4.9 pCi/L
Howard County59 of 9938861.3%5.9 pCi/L
Mahaska County60 of 9928861.1%5.2 pCi/L
Taylor County61 of 9923560.9%4.6 pCi/L
Cedar County62 of 9976560.4%5.0 pCi/L
Keokuk County63 of 9921460.3%5.2 pCi/L
Butler County64 of 9937759.9%5.2 pCi/L
Howard County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201738861.3%5.9 pCi/L122.7 pCi/L58.5%−0.2 points
2007 to 201640061.5%5.9 pCi/L122.7 pCi/L58.6%−0.8 points
2006 to 201543062.3%5.8 pCi/L122.7 pCi/L59.4%−0.2 points
2005 to 201441162.5%5.9 pCi/L108.7 pCi/L59.6%First on file

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

Howard County, Geology

The ground under Howard County

Predicted

USGS's geologic map puts all of Howard County's mapped land in one class: high radon potential. 95.9% of it lies in the area the map calls Iowan Surface, to which USGS gives a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Howard County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Iowan SurfacePre-Illinoian glaical deposits and loess.High1295.9%
Paleozoic PlateauOrdovician carbonate and Cambrian sandstone bedrock covered by varying amounts of Quaternary glacial deposits and loess.High134.1%

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

Howard County beside the ground around it

On high-potential ground Howard 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; Chickasaw County comes nearest at 100%.

Share of land by USGS radon potential: Howard County, the 6 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Howard CountyZone 1NoneNone100%
Mitchell CountyZone 1NoneNone100%
Fillmore County, MNZone 1NoneNone100%
Winneshiek CountyZone 1NoneNone100%
Chickasaw CountyZone 1NoneNone100%
Mower County, MNZone 1NoneNone100%
Floyd CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Howard County, Local resources

Radon testing and mitigation in Howard County

Listed radon businesses with an address in Howard County:

Listed radon professionals by town: Cresco

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

Howard County, Questions

Questions about radon in Howard County

Are radon levels high in Howard County?

Over the 2008 to 2017 laboratory totals, 61.3% of the radon tests reported to CDC for Howard County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.9 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 58 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Howard County?

Howard County borders 6 counties: Mitchell County, IA, Fillmore County, MN, Winneshiek County, IA, Chickasaw County, IA, Mower County, MN and Floyd County, IA.

Products

Howard County, Products

Testing a home in Howard County

In Howard County, 61.3% of 388 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 Howard 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

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

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Howard County, Bordering counties

Counties bordering Howard County

Calculated by Radon411

Howard County, Cities and towns

Cities and towns in Howard County

About 9,415 people live in Howard County by the Census Bureau's estimate for July 1, 2025, 79 fewer than in 2020 (−0.8%). That works out to 20 people per square mile of land. Its largest town, Cresco, has 3,925 residents, 41.7% of the total. CDC's 388 reported tests for 2008 to 2017 work out to 41.2 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Cresco to Chester, CDC publishes no figure by town: each reads Howard County's.

The cities and towns in Howard County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Cresco3,925+0.6%41.7%
Ricevilleextends beyond Howard County805−0.7%Counted whole
Elma492−3.0%5.2%
Lime Springs471−1.5%5.0%
Protivinextends beyond Howard County263−1.5%Counted whole
Chester134−2.2%1.4%

6 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 Howard County is counted whole, so it has no share.

Howard County, Homes

Homes in Howard County

Howard County is a place of houses on their own lots: 91% of its 4,314 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 52% date from before 1960. Owners live in 77% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Howard County, Iowa, 2019 to 2023
HomesHoward CountyIowa
Housing units4,3141,427,175
Detached houses91%72%
In buildings of 5 or more3%14%
Mobile homes1%3%
Built before 196052%39%
Built since 200011%21%
Middle year built19541971
Owner-occupied77%72%

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