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Radon Levels in Shawnee County, Kansas

EPA puts Shawnee County in Zone 2, its middle radon zone, and 34.5% of its 388 reported radon tests (2022) were 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

    34.5%

    2.5 pts above KS

    Shawnee
    34.5%
    Kansas
    32.0%

    388 tests, 2022

  • Median result

    2.6pCi/L

    Below action level

    Shawnee
    2.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    388

    9th of 38 by tests

    Shawnee
    388
    Johnson
    5,240

    Reported to CDC before any fix, 2022

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Kansas

    17 of 38

    Middle half

    Shawnee
    34.5%
    Mitchell
    57.4%

    By share, of 38 with 30+ tests

Read a result for Shawnee County

Starts at Shawnee County's median, 2.6 pCi/L

2.6pCi/L

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

EPA’s reading of 2.6 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Shawnee County's median reported result, 2022.

Interpret this readingWhat a fix costs

The data

Shawnee County, At a glance

Shawnee County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Shawnee County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 79% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Shawnee County, 2022

Share of reported tests at or above 4 pCi/L, by year, Shawnee County
Share of reported tests at or above 4 pCi/L, by year, Shawnee County
YearShare of reported tests at or above 4 pCi/L
201637.1%
201737.3%
201839.5%
201929.0%
202031.1%
202125.0%
202234.5%

2022: 34.5%. Across these years the share ran from 25.0% to 39.5%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 388 tests reported to CDC for Shawnee County over 2022, 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: 2022. Measured data period: 2016 to 2022 (every CDC figure on file).

How to read these figures

Shawnee County, Compared

Shawnee County radon figures, compared

Calculated by Radon411

In Shawnee County, about 3 in 10 reported tests in 2022 (134 of 388) were at or above EPA's action level. Against the national pool of 23.9%, the gap is 10.6 points higher. Across 96 Kansas counties pooled together, 32.0% of tests reached that level, so Shawnee County runs 2.5 points above its state.

Of 4 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 25.2% (Pottawatomie County) to 39.6% (Jefferson County). By share, Shawnee County is 17th of 38 Kansas counties with 30 or more tests for the same period.

Year by year, 2016 opened at 37.1% and 2022 closed at 34.5% (down 2.6 points), with 2018 the high at 39.5%. Half the tests came in under 2.6 pCi/L and half over it; the single highest reached 78.0 pCi/L. Below the action level, 159 tests (41.0%) came in under 2 pCi/L, against 45.8% statewide, and 95 tests (24.5%) fell between 2 and 4, against 22.1% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 34.5% share point the same way here. USGS geology rates 79% of the county's land moderate radon potential. CDC also counts 20 tests taken after mitigation in Shawnee County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2021, with 1,392 tests reported; the quietest, 2022, had 388.

Share of reported tests at or above 4 pCi/L by year, Shawnee County against Kansas2016 to 2022, years with 30 or more tests: Shawnee County 37.1% to 34.5%, the state's pooled share 32.0% in 2022.
Shawnee CountyKansas, pooled
Share of reported tests at or above 4 pCi/L by year, Shawnee County against Kansas: data table
YearTestsShawnee County, at or above 4 pCi/LKansas, pooled
201671437.1%35.4%
20171,12337.3%37.3%
20181,12139.5%37.3%
201985829.0%33.7%
202070431.1%31.3%
20211,39225.0%31.8%
202238834.5%32.0%
Shawnee County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Shawnee County
Shawnee County38834.5%2.6 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled−2.5 points
United States, pooled853 counties, pooled333,14023.9%Not pooled−10.6 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+22.9 points
Crawford Countylowest in the state345.9%0.8 pCi/L−28.6 points
Osage County, KSborders it2642.3%3.5 pCi/L+7.8 points
Jefferson County, KSborders it5339.6%2.4 pCi/L+5.1 points
Wabaunsee County, KSborders it3129.0%2.2 pCi/L−5.5 points
Douglas County, KSborders it86825.8%1.8 pCi/L−8.7 points
Pottawatomie County, KSborders it20625.2%1.7 pCi/L−9.3 points
Jackson County, KSborders it2123.8%2.7 pCi/L−10.7 points
Where Shawnee County's reported results fell, 2022, beside Kansas and the United States
ResultShawnee County testsShawnee County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L15941.0%45.8%54.5%−4.8 points
2 to 4 pCi/L9524.5%22.1%21.7%+2.4 points
4 pCi/L and above13434.5%32.0%23.9%+2.5 points
Shawnee County ranked among the 38 Kansas counties with 30 or more tests, by share at or above 4 pCi/L, 2022
CountyRankTestsAt or above 4 pCi/LMedian
Marion County12 of 384540.0%2.5 pCi/L
Cowley County13 of 3811839.8%3.3 pCi/L
Jefferson County14 of 385339.6%2.4 pCi/L
Dickinson County15 of 3811338.9%2.7 pCi/L
Ford County16 of 385036.0%3.8 pCi/L
Shawnee County17 of 3838834.5%2.6 pCi/L
Harvey County18 of 3823234.1%2.8 pCi/L
Franklin County19 of 3810634.0%2.1 pCi/L
Lyon County20 of 384731.9%2.5 pCi/L
Marshall County21 of 386631.8%1.9 pCi/L
Riley County22 of 3880031.3%1.9 pCi/L
Shawnee County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
202238834.5%2.6 pCi/L78.0 pCi/L32.0%+9.5 points
20211,39225.0%2.0 pCi/L40.1 pCi/L31.8%−6.1 points
202070431.1%2.3 pCi/L50.6 pCi/L31.3%+2.1 points
201985829.0%2.2 pCi/L38.3 pCi/L33.7%−10.5 points
20181,12139.5%2.9 pCi/L186.4 pCi/L37.3%+2.2 points
20171,12337.3%2.8 pCi/L29.4 pCi/L37.3%+0.2 points
201671437.1%3.2 pCi/L30.6 pCi/L35.4%First on file

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

Shawnee County, Geology

The ground under Shawnee County

Predicted

Most of the ground under Shawnee County is one class on USGS's geologic map: 79.3% of its land is moderate radon potential, with 20.7% high. The map puts 79.3% of Shawnee County in the area it calls Glaciated Area and 20.7% in Glacial Drift. USGS gives the first a radon index of 9, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).

USGS's geologic areas under Shawnee County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Glaciated AreaGlacial till underlain by Pennsylvanian and Permian marine and nonmarine sedimentary shale, sandstone, limestone, coal.Moderate979.3%
Glacial DriftGlacial drift and loess of varying thickness, largely locally derived from underlying and nearby Paleozoic sedimentary rocks.High1220.7%

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

Shawnee County beside the ground around it

Kansas as a whole has more high-potential ground than Shawnee County: 59.9% of its land, against 20.7% here. Of the 6 counties that border it, 4 have more high-potential ground, Pottawatomie County the most at 65.3%.

Share of land by USGS radon potential: Shawnee County, the 6 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Shawnee CountyZone 2None79.3%20.7%
Douglas CountyZone 1None100%None
Wabaunsee CountyZone 2None62.4%37.6%
Osage CountyZone 2None100%None
Jefferson CountyZone 2None70.7%29.3%
Jackson CountyZone 1None52.6%47.4%
Pottawatomie CountyZone 1None34.7%65.3%
Kansas105 counties, pooled by land areaVariesNone40.1%59.9%

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

Local help

Shawnee County, Local resources

Radon testing and mitigation in Shawnee County

Listed radon businesses with an address in Shawnee County:

Listed radon professionals by town: Topeka

What Kansas's program says
Phone
(800) 693-5343

What it means

Shawnee County, Questions

Questions about radon in Shawnee County

Are radon levels high in Shawnee County?

In 2022, 34.5% of the radon tests reported to CDC for Shawnee County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.6 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 16 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Shawnee County?

Shawnee County borders 6 counties: Douglas County, Wabaunsee County, Osage County, Jefferson County, Jackson County and Pottawatomie County.

Products

Shawnee County, Products

Testing a home in Shawnee County

In Shawnee County, 34.5% of 388 tests reported to CDC in 2022 reached 4 pCi/L, against 32.0% pooled across Kansas. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Shawnee County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Shawnee County homes, compared

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Shawnee County, Bordering counties

Counties bordering Shawnee County

Calculated by Radon411

Shawnee County, Cities and towns

Cities and towns in Shawnee County

Shawnee County's population has barely moved since 2020: 178,607 residents on July 1, 2025 against 178,699 then, by the Census Bureau's estimates. That works out to 328 people per square mile of land. Topeka alone is home to 125,795 of them, 70.4% of the total. Reported testing is thin here: 388 tests over 2022, or 2.2 for every 1,000 residents (2025 estimate), where Kansas as a whole comes to 6.2.

From Topeka to Willard, CDC publishes no figure by town: each reads Shawnee County's.

The cities and towns in Shawnee County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Topeka125,795−0.5%70.4%
Silver Lake1,316−2.2%0.7%
Auburn1,272−0.3%0.7%
Rossville1,088−1.8%0.6%
Willardextends beyond Shawnee County68+1.5%Counted whole

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). A place that extends beyond Shawnee County is counted whole, so it has no share.

Shawnee County, Homes

Homes in Shawnee County

Of Shawnee County's 80,884 homes, 72% are detached houses, against 72% across Kansas; 14% are in buildings of five or more homes. Half of its homes were built before 1971, close to Kansas' 1975: 33% date from before 1960 and 14% from 2000 or later. 67% of occupied homes are lived in by their owner (Kansas: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Shawnee County, Kansas, 2019 to 2023
HomesShawnee CountyKansas
Housing units80,8841,285,221
Detached houses72%72%
In buildings of 5 or more14%13%
Mobile homes3%4%
Built before 196033%33%
Built since 200014%20%
Middle year built19711975
Owner-occupied67%67%

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