Skip to content
RADON411

Locations and reports

Radon Levels in Worth County, Iowa

EPA puts Worth County in Zone 1, its highest radon zone, and high results are common there: 67.5% of the 154 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

    67.5%

    9.0 pts above IA

    Worth
    67.5%
    Iowa
    58.5%

    154 tests, 2008 to 2017

  • Median result

    6.0pCi/L

    Action level reached

    Worth
    6.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    154

    84th of 99 by tests

    Worth
    154
    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

    40 of 99

    Middle half

    Worth
    67.5%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Worth County

Starts at Worth County's median, 6.0 pCi/L

6.0pCi/L

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

EPA’s reading of 6.0 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. Worth County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Worth County, At a glance

Worth County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Worth County, 2008 to 2017, laboratory
Under 2 pCi/L: 13%2 to 4 pCi/L: 20%4 pCi/L and above: 67%

Of 154 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Worth County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L2013.0%
2 to 4 pCi/L3019.5%
4 pCi/L and above10467.5%
What these figures count

These are the 154 tests reported to CDC for Worth 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

Worth County, Compared

Worth County radon figures, compared

Calculated by Radon411

More than half: 67.5% of the 154 radon tests reported to CDC for Worth County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 40th of 99 Iowa counties with 30 or more tests for the same period. That is 9.0 points above the 58.5% pooled from 99 Iowa counties.

The median result, 6.0 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 39.5 pCi/L. The rest split 13.0% under 2 pCi/L and 19.5% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 67.5% share point the same way here.

3 of its 6 bordering counties with figures ran higher, led by Winnebago County at 71.9%; 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 Worth County went from 126 tests (2005 to 2014) to 154 (2008 to 2017), the share going from 66.7% to 67.5%.

Nationally, every county with a figure for the same period pools to 35.7%; Worth County sits 31.8 points above it. CDC also counts 19 tests taken after mitigation in Worth County for the same period: tests in homes where a fix was already in.

Worth County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Worth County
Worth County15467.5%6.0 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−9.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−31.8 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+16.7 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−41.6 points
Winnebago County, IAborders it82971.9%6.7 pCi/L+4.4 points
Mitchell County, IAborders it44470.7%6.4 pCi/L+3.2 points
Freeborn County, MNborders it81669.1%6.2 pCi/L+1.6 points
Hancock County, IAborders it64064.5%5.5 pCi/L−3.0 points
Cerro Gordo County, IAborders it1,66259.0%4.8 pCi/L−8.5 points
Mower County, MNborders it50048.2%3.8 pCi/L−19.3 points
Where Worth County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultWorth County testsWorth County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L2013.0%21.8%39.6%−8.8 points
2 to 4 pCi/L3019.5%19.7%24.7%−0.2 points
4 pCi/L and above10467.5%58.5%35.7%+9.0 points
Worth 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
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
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
Worth County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201715467.5%6.0 pCi/L39.5 pCi/L58.5%−0.7 points
2007 to 201614868.2%6.0 pCi/L39.5 pCi/L58.6%−0.1 points
2006 to 201513968.3%5.9 pCi/L39.5 pCi/L59.4%+1.6 points
2005 to 201412666.7%5.9 pCi/L39.5 pCi/L59.6%First on file

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

Worth County, Geology

The ground under Worth County

Predicted

USGS's geologic map puts all of Worth County's mapped land in one class: high radon potential. The map puts 67.5% of Worth County in the area it calls Iowan Surface and 32.5% in Des Moines Lobe. USGS gives both a radon index of 12, in the high band (12 to 17).

USGS's geologic areas under Worth County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Iowan SurfacePre-Illinoian glaical deposits and loess.High1267.5%
Des Moines LobeCalcareous loamy till derived from shale, limestone, dolomite, sandstone.High1232.5%

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

Worth County beside the ground around it

On high-potential ground Worth 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; Cerro Gordo County comes nearest at 100%.

Share of land by USGS radon potential: Worth County, the 6 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Worth CountyZone 1NoneNone100%
Freeborn County, MNZone 1NoneNone100%
Cerro Gordo CountyZone 1NoneNone100%
Mitchell CountyZone 1NoneNone100%
Winnebago CountyZone 1NoneNone100%
Hancock CountyZone 1NoneNone100%
Mower County, MNZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Worth County, Local resources

Radon testing and mitigation in Worth 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

Worth County, Questions

Questions about radon in Worth County

Are radon levels high in Worth County?

Over the 2008 to 2017 laboratory totals, 67.5% of the radon tests reported to CDC for Worth County, Iowa were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.0 pCi/L. Of 99 Iowa counties with 30 or more tests for the same period, 39 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Worth County?

Worth County borders 6 counties: Freeborn County, MN, Cerro Gordo County, IA, Mitchell County, IA, Winnebago County, IA, Hancock County, IA and Mower County, MN.

Products

Worth County, Products

Testing a home in Worth County

In Worth County, 67.5% of 154 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 Worth 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

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

Explore

Worth County, Bordering counties

Counties bordering Worth County

Calculated by Radon411

Worth County, Cities and towns

Cities and towns in Worth County

About 7,338 people live in Worth County by the Census Bureau's estimate for July 1, 2025, 99 fewer than in 2020 (−1.3%). That works out to 18 people per square mile of land. Its largest town, Northwood, has 2,056 residents, 28.0% of the total. Together its 7 incorporated places hold 61.0% of those residents; the other 39.0% live outside any of them. CDC's 154 reported tests for 2008 to 2017 work out to 21.0 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

From Northwood to Hanlontown, CDC publishes no figure by town: each reads Worth County's.

The cities and towns in Worth County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Northwood2,056−0.6%28.0%
Manly1,239−1.6%16.9%
Fertile301−1.3%4.1%
Kensett258−0.4%3.5%
Grafton212−1.9%2.9%
Joice207−1.9%2.8%
Hanlontown203−1.9%2.8%

7 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).

Worth County, Homes

Homes in Worth County

Worth County is a place of houses on their own lots: 89% of its 3,487 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1949 (1971 for Iowa), and 61% 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 Worth County, Iowa, 2019 to 2023
HomesWorth CountyIowa
Housing units3,4871,427,175
Detached houses89%72%
In buildings of 5 or more4%14%
Mobile homes2%3%
Built before 196061%39%
Built since 20008%21%
Middle year built19491971
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.