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Radon Levels in Tama County, Iowa

EPA puts Tama County in Zone 1, its highest radon zone, and high results are common there: 67.9% of the 333 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

    67.9%

    9.4 pts above IA

    Tama
    67.9%
    Iowa
    58.5%

    333 tests, 2008 to 2017

  • Median result

    7.0pCi/L

    Action level reached

    Tama
    7.0 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    333

    67th of 99 by tests

    Tama
    333
    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

    39 of 99

    Middle half

    Tama
    67.9%
    Sioux
    84.2%

    By share, of 99 with 30+ tests

Read a result for Tama County

Starts at Tama 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. Tama County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Tama County, At a glance

Tama County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Tama County, 2008 to 2017, laboratory
Under 2 pCi/L: 18%2 to 4 pCi/L: 14%4 pCi/L and above: 68%

Of 333 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Tama County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L5917.7%
2 to 4 pCi/L4814.4%
4 pCi/L and above22667.9%
What these figures count

These are the 333 tests reported to CDC for Tama 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

Tama County, Compared

Tama County radon figures, compared

Calculated by Radon411

More than half: 67.9% of the 333 radon tests reported to CDC for Tama County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 39th of 99 Iowa counties with 30 or more tests for the same period. That is 9.4 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 109.3 pCi/L. The rest split 17.7% under 2 pCi/L and 14.4% from 2 to 4 (Iowa: 21.8% and 19.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 67.9% share point the same way here.

3 of its 7 bordering counties with figures ran higher, led by Jasper County at 73.3%; Black Hawk County reported 48.4%. 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 Tama County went from 328 tests (2005 to 2014) to 333 (2008 to 2017), the share going from 72.6% to 67.9%.

Nationally, every county with a figure for the same period pools to 35.7%; Tama County sits 32.2 points above it. CDC also counts 46 tests taken after mitigation in Tama County for the same period: tests in homes where a fix was already in.

Tama County against Iowa, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Tama County
Tama County33367.9%7.0 pCi/LThis county
Iowa, pooled99 counties, pooled95,24558.5%Not pooled−9.4 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−32.2 points
Sioux Countyhighest in the state1,98284.2%10.7 pCi/L+16.3 points
Decatur Countylowest in the state8525.9%2.5 pCi/L−42.0 points
Jasper County, IAborders it74673.3%8.2 pCi/L+5.4 points
Poweshiek County, IAborders it41970.6%7.2 pCi/L+2.7 points
Marshall County, IAborders it57070.2%8.2 pCi/L+2.3 points
Grundy County, IAborders it50166.9%6.9 pCi/L−1.0 points
Benton County, IAborders it69662.1%5.6 pCi/L−5.8 points
Iowa County, IAborders it51959.2%5.1 pCi/L−8.7 points
Black Hawk County, IAborders it3,22348.4%3.8 pCi/L−19.5 points
Where Tama County's reported results fell, 2008 to 2017, laboratory, beside Iowa and the United States
ResultTama County testsTama County shareIowa shareU.S. shareAgainst Iowa
Under 2 pCi/L5917.7%21.8%39.6%−4.1 points
2 to 4 pCi/L4814.4%19.7%24.7%−5.3 points
4 pCi/L and above22667.9%58.5%35.7%+9.4 points
Tama 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
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
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
Tama County ten-year laboratory totals, against Iowa's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIowa, pooledChange from the row before
2008 to 201733367.9%7.0 pCi/L109.3 pCi/L58.5%−2.0 points
2007 to 201633969.9%7.4 pCi/L109.3 pCi/L58.6%−1.2 points
2006 to 201534271.1%7.6 pCi/L109.3 pCi/L59.4%−1.5 points
2005 to 201432872.6%7.8 pCi/L109.3 pCi/L59.6%First on file

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

Tama County, Geology

The ground under Tama County

Predicted

USGS's geologic map puts all of Tama County's mapped land in one class: high radon potential. 97.1% 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 Tama County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1397.1%
Iowan SurfacePre-Illinoian glaical deposits and loess.High122.9%

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

Tama County beside the ground around it

On high-potential ground Tama 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; Benton County comes nearest at 100%.

Share of land by USGS radon potential: Tama County, the 7 counties bordering it and Iowa
AreaEPA zoneLow potentialModerate potentialHigh potential
Tama CountyZone 1NoneNone100%
Poweshiek CountyZone 1NoneNone100%
Marshall CountyZone 1NoneNone100%
Benton CountyZone 1NoneNone100%
Grundy CountyZone 1NoneNone100%
Iowa CountyZone 1NoneNone100%
Jasper CountyZone 1NoneNone100%
Black Hawk CountyZone 1NoneNone100%
Iowa99 counties, pooled by land areaVariesNone1.2%98.8%

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

Local help

Tama County, Local resources

Radon testing and mitigation in Tama County

Listed radon businesses with an address in Tama County:

Listed radon professionals by town: Toledo

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

Tama County, Questions

Questions about radon in Tama County

Are radon levels high in Tama County?

Over the 2008 to 2017 laboratory totals, 67.9% of the radon tests reported to CDC for Tama 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, 38 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Tama County?

Tama County borders 7 counties: Poweshiek County, Marshall County, Benton County, Grundy County, Iowa County, Jasper County and Black Hawk County.

Products

Tama County, Products

Testing a home in Tama County

In Tama County, 67.9% of 333 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 Tama 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

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

Explore

Tama County, Bordering counties

Counties bordering Tama County

Calculated by Radon411

Tama County, Cities and towns

Cities and towns in Tama County

About 16,796 people live in Tama County by the Census Bureau's estimate for July 1, 2025, 254 fewer than in 2020 (−1.5%). That works out to 23 people per square mile of land. No town dominates: Tama, the largest, has 3,011 residents, 17.9% of the total. CDC's 333 reported tests for 2008 to 2017 work out to 19.8 per 1,000 residents (2025 estimate), close to Iowa's 29.4.

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

The 12 largest cities and towns in Tama County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Tama3,011−2.5%17.9%
Toledo2,384+0.9%14.2%
Traer1,555−1.3%9.3%
Dysart1,268−0.7%7.5%
Le Grandextends beyond Tama County883−1.9%Counted whole
Gladbrook779−2.6%4.6%
Garwin469−2.9%2.8%
Clutier209−1.9%1.2%
Chelsea208−2.8%1.2%
Montour197−2.5%1.2%
Elberon178−1.7%1.1%
Lincoln120−0.8%0.7%
  • Vining

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 Tama County is counted whole, so it has no share.

Tama County, Homes

Homes in Tama County

Tama County is a place of houses on their own lots: 87% of its 7,595 homes are detached single-family houses, against 72% across Iowa. The homes are older than Iowa's as a whole: half were built before 1956 (1971 for Iowa), and 54% date from before 1960. Owners live in 76% of the occupied homes (Iowa: 72%), so for most households a test and a fix are their own to order.

Homes in Tama County, Iowa, 2019 to 2023
HomesTama CountyIowa
Housing units7,5951,427,175
Detached houses87%72%
In buildings of 5 or more5%14%
Mobile homes4%3%
Built before 196054%39%
Built since 200011%21%
Middle year built19561971
Owner-occupied76%72%

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