Skip to content
RADON411

Locations and reports

Radon Levels in Marion County, Kansas

EPA puts Marion County in Zone 1, its highest radon zone, and high results are common there: 40.0% of the 45 radon tests reported to CDC (2022) 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

    40.0%

    8.0 pts above KS

    Marion
    40.0%
    Kansas
    32.0%

    45 tests, 2022

  • Median result

    2.5pCi/L

    Below action level

    Marion
    2.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    45

    33rd of 38 by tests

    Marion
    45
    Johnson
    5,240

    Reported to CDC before any fix, 2022

  • 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 Kansas

    12 of 38

    Middle half

    Marion
    40.0%
    Mitchell
    57.4%

    By share, of 38 with 30+ tests

Read a result for Marion County

Starts at Marion County's median, 2.5 pCi/L

2.5pCi/L

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

EPA’s reading of 2.5 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. Marion County's median reported result, 2022.

Interpret this readingWhat a fix costs

The data

Marion County, At a glance

Marion County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Marion 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: Moderate across 82% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Marion County, 2022

Share of reported tests at or above 4 pCi/L, by year, Marion County
Share of reported tests at or above 4 pCi/L, by year, Marion County
YearShare of reported tests at or above 4 pCi/L
201651.1%
201728.1%
201856.1%
201935.1%
202055.6%
202130.3%
202240.0%

2022: 40.0%. Across these years the share ran from 28.1% to 56.1%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 45 tests reported to CDC for Marion 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

Marion County, Compared

Marion County radon figures, compared

Calculated by Radon411

In Marion County, about 4 in 10 reported tests in 2022 (18 of 45) were at or above EPA's action level. Against the national pool of 23.9%, the gap is 16.1 points higher. Across 96 Kansas counties pooled together, 32.0% of tests reached that level, so Marion County runs 8.0 points above its state.

Of 5 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 25.5% (Butler County) to 52.3% (Saline County). By share, Marion County is 12th of 38 Kansas counties with 30 or more tests for the same period.

Year by year, 2016 opened at 51.1% and 2022 closed at 40.0% (down 11.1 points), with 2018 the high at 56.1%. Half the tests came in under 2.5 pCi/L and half over it; the single highest reached 17.5 pCi/L. Below the action level, 20 tests (44.4%) came in under 2 pCi/L, against 45.8% statewide, and 7 tests (15.6%) fell between 2 and 4, against 22.1% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 40.0% share point the same way here. USGS geology rates 82% of the county's land moderate radon potential.

The busiest year on file was 2021, with 99 tests reported; the quietest, 2020, had 27.

Share of reported tests at or above 4 pCi/L by year, Marion County against Kansas2016 to 2022, years with 30 or more tests: Marion County 51.1% to 40.0%, the state's pooled share 32.0% in 2022.
Marion CountyKansas, pooled
Share of reported tests at or above 4 pCi/L by year, Marion County against Kansas: data table
YearTestsMarion County, at or above 4 pCi/LKansas, pooled
20164551.1%35.4%
20173228.1%37.3%
20184156.1%37.3%
20193735.1%33.7%
20219930.3%31.8%
20224540.0%32.0%
Marion County against Kansas, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Marion County
Marion County4540.0%2.5 pCi/LThis county
Kansas, pooled96 counties, pooled18,38532.0%Not pooled−8.0 points
United States, pooled853 counties, pooled333,14023.9%Not pooled−16.1 points
Mitchell Countyhighest in the state4757.4%6.2 pCi/L+17.4 points
Crawford Countylowest in the state345.9%0.8 pCi/L−34.1 points
Chase County, KSborders it366.7%4.4 pCi/L+26.7 points
Saline County, KSborders it72952.3%4.2 pCi/L+12.3 points
McPherson County, KSborders it21551.6%4.1 pCi/L+11.6 points
Morris County, KSborders it2343.5%3.5 pCi/L+3.5 points
Dickinson County, KSborders it11338.9%2.7 pCi/L−1.1 points
Harvey County, KSborders it23234.1%2.8 pCi/L−5.9 points
Butler County, KSborders it55025.5%2.1 pCi/L−14.5 points
Where Marion County's reported results fell, 2022, beside Kansas and the United States
ResultMarion County testsMarion County shareKansas shareU.S. shareAgainst Kansas
Under 2 pCi/L2044.4%45.8%54.5%−1.4 points
2 to 4 pCi/L715.6%22.1%21.7%−6.5 points
4 pCi/L and above1840.0%32.0%23.9%+8.0 points
Marion 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
McPherson County7 of 3821551.6%4.1 pCi/L
Pawnee County8 of 385343.4%3.7 pCi/L
Atchison County9 of 386041.7%3.3 pCi/L
Johnson County10 of 385,24041.2%3.0 pCi/L
Miami County11 of 3821440.2%3.0 pCi/L
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
Marion County radon tests by year, against Kansas' pooled share
YearTestsAt or above 4 pCi/LMedianHighestKansas, pooledChange from the row before
20224540.0%2.5 pCi/L17.5 pCi/L32.0%+9.7 points
20219930.3%2.3 pCi/L10.2 pCi/L31.8%−25.3 points
20202755.6%4.6 pCi/L17.1 pCi/L31.3%+20.5 points
20193735.1%2.5 pCi/L8.0 pCi/L33.7%−21.0 points
20184156.1%5.1 pCi/L15.1 pCi/L37.3%+28.0 points
20173228.1%2.3 pCi/L20.6 pCi/L37.3%−23.0 points
20164551.1%4.1 pCi/L17.3 pCi/L35.4%First on file

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

Marion County, Geology

The ground under Marion County

Predicted

Most of the ground under Marion County is one class on USGS's geologic map: 82.3% of its land is moderate radon potential, with 17.7% high. The map puts 82.3% of Marion County in the area it calls Glaciated Area and 9.9% in Smoky Hills, with one smaller area beside them. 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 Marion 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.Moderate982.3%
Smoky HillsCretaceous marine sandstone, shale, and siltstone covered by discontinuous loess deposits.High129.9%
Mid-Continent Rift ZoneFaulted and fractured Permian limestone, dolomite, shale, and sandstone related to the Mid-Continent Rift zone.High127.8%

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

Marion County beside the ground around it

Kansas as a whole has more high-potential ground than Marion County: 59.9% of its land, against 17.7% here. Of the 7 counties that border it, 4 have more high-potential ground, Saline County the most at 100%.

Share of land by USGS radon potential: Marion County, the 7 counties bordering it and Kansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Marion CountyZone 1None82.3%17.7%
Harvey CountyZone 2None100%None
Chase CountyZone 2None100%None
McPherson CountyZone 1None52.1%47.9%
Butler CountyZone 2None100%None
Morris CountyZone 2None80.0%20.0%
Saline CountyZone 1NoneNone100%
Dickinson CountyZone 1NoneNone100%
Kansas105 counties, pooled by land areaVariesNone40.1%59.9%

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

Local help

Marion County, Local resources

Radon testing and mitigation in Marion County

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

What it means

Marion County, Questions

Questions about radon in Marion County

Are radon levels high in Marion County?

In 2022, 40.0% of the radon tests reported to CDC for Marion County, Kansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.5 pCi/L. Of 38 Kansas counties with 30 or more tests for the same period, 11 reported a higher share; pooled, the state comes to 32.0%.

Which counties border Marion County?

Marion County borders 7 counties: Harvey County, Chase County, McPherson County, Butler County, Morris County, Saline County and Dickinson County.

Products

Marion County, Products

Testing a home in Marion County

In Marion County, 40.0% of 45 tests reported to CDC in 2022 reached 4 pCi/L, against 32.0% pooled across Kansas. In Zone 1 the year-round level in Marion 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

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

Explore

Marion County, Bordering counties

Counties bordering Marion County

Calculated by Radon411

Marion County, Cities and towns

Cities and towns in Marion County

About 11,634 people live in Marion County by the Census Bureau's estimate for July 1, 2025, 154 fewer than in 2020 (−1.3%). That works out to 12 people per square mile of land. Its largest town, Hillsboro, has 2,646 residents, 22.7% of the total. Together its 12 incorporated places hold 62.5% of those residents; the other 37.5% live outside any of them. Reported testing is thin here: 45 tests over 2022, or 3.9 for every 1,000 residents (2025 estimate), where Kansas as a whole comes to 6.2.

From Hillsboro to Lost Springs, CDC publishes no figure by town: each reads Marion County's.

The cities and towns in Marion County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Hillsboro2,646−2.9%22.7%
Marion1,897−1.2%16.3%
Peabody909−3.0%7.8%
Goessel558−0.4%4.8%
Florence377−3.3%3.2%
Burns227−2.6%2.0%
Lincolnville168−0.6%1.4%
Lehigh159+0.6%1.4%
Tampa102−4.7%0.9%
Durham90−1.1%0.8%
Ramona79+1.3%0.7%
Lost Springs54Level0.5%

12 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).

Marion County, Homes

Homes in Marion County

Marion County is a place of houses on their own lots: 87% of its 5,673 homes are detached single-family houses, against 72% across Kansas. The homes are older than Kansas' as a whole: half were built before 1957 (1975 for Kansas), and 55% date from before 1960. Owners live in 81% of the occupied homes (Kansas: 67%), so for most households a test and a fix are their own to order.

Homes in Marion County, Kansas, 2019 to 2023
HomesMarion CountyKansas
Housing units5,6731,285,221
Detached houses87%72%
In buildings of 5 or more3%13%
Mobile homes5%4%
Built before 196055%33%
Built since 200010%20%
Middle year built19571975
Owner-occupied81%67%

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