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Radon Levels in Cass County, Missouri

EPA puts Cass County in Zone 1, its highest radon zone, and only 24 radon tests from it are on file with CDC (2023). 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

    45.5%

    14.9 pts above MO

    Cass
    45.5%
    Missouri
    30.6%

    988 tests, 2008 to 2017

  • Median result

    3.5pCi/L

    Below action level

    Cass
    3.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    988

    10th of 72 by tests

    Cass
    988
    St. Louis
    17,747

    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 Missouri

    7 of 72

    Top quarter

    Cass
    45.5%
    Atchison
    69.9%

    By share, of 72 with 30+ tests

Read a result for Cass County

Starts at Cass County's median, 3.5 pCi/L

3.5pCi/L

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

EPA’s reading of 3.5 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. Cass County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Cass County, At a glance

Cass County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Cass 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 64% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Cass County, 2023

Share of reported tests at or above 4 pCi/L, by year, Cass County
Share of reported tests at or above 4 pCi/L, by year, Cass County
YearShare of reported tests at or above 4 pCi/L
201457.4%
201554.0%
201644.1%
201750.0%
201853.8%
201933.3%
202047.1%
202129.6%
202261.3%
202362.5%

2023: 62.5%. Across these years the share ran from 29.6% to 62.5%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 24 tests were reported to CDC for Cass County over 2023, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.

Measured: CDC tracking data. Figure above: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Cass County, Compared

Cass County radon figures, compared

Calculated by Radon411

In Cass County, about 5 in 10 reported tests over the 2008 to 2017 laboratory totals (450 of 988) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 9.8 points higher. Across 115 Missouri counties pooled together, 30.6% of tests reached that level, so Cass County runs 14.9 points above its state.

The newest figure, in 2023, counts only 24 tests (62.5% at or above 4 pCi/L), too few to compare, so this reading uses the 988-test figure.

Of 3 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 25.8% (Johnson County) to 41.3% (Jackson County). By share, Cass County is 7th of 72 Missouri counties with 30 or more tests for the same period.

Year by year, 2014 opened at 57.4% and 2022 closed at 61.3% (up 3.9 points), with 2022 the high at 61.3%. Half the tests came in under 3.5 pCi/L and half over it; the single highest reached 104.0 pCi/L. Below the action level, 317 tests (32.1%) came in under 2 pCi/L, against 41.2% statewide, and 221 tests (22.4%) fell between 2 and 4, against 28.1% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 45.5% share point the same way here. USGS geology rates 64% of the county's land moderate radon potential. CDC also counts 41 tests taken after mitigation in Cass County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2016, with 93 tests reported; the quietest, 2019, had 9.

Share of reported tests at or above 4 pCi/L by year, Cass County against Missouri2014 to 2022, years with 30 or more tests: Cass County 57.4% to 61.3%, the state's pooled share 40.8% in 2022.
Cass CountyMissouri, pooled
Share of reported tests at or above 4 pCi/L by year, Cass County against Missouri: data table
YearTestsCass County, at or above 4 pCi/LMissouri, pooled
20145457.4%34.4%
20155054.0%27.6%
20169344.1%29.8%
20174050.0%37.0%
20183953.8%42.1%
20223161.3%40.8%
Cass County against Missouri, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Cass County
Cass County98845.5%3.5 pCi/LThis county
Missouri, pooled115 counties, pooled58,52530.6%Not pooled−14.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−9.8 points
Atchison Countyhighest in the state10369.9%5.6 pCi/L+24.4 points
Vernon Countylowest in the state348.8%0.9 pCi/L−36.7 points
Jackson County, MOborders it6,61841.3%3.1 pCi/L−4.2 points
Henry County, MOborders it8138.3%3.4 pCi/L−7.2 points
Bates County, MOborders it2326.1%1.5 pCi/L−19.4 points
Johnson County, MOborders it26425.8%1.9 pCi/L−19.7 points
Where Cass County's reported results fell, 2008 to 2017, laboratory, beside Missouri and the United States
ResultCass County testsCass County shareMissouri shareU.S. shareAgainst Missouri
Under 2 pCi/L31732.1%41.2%39.6%−9.1 points
2 to 4 pCi/L22122.4%28.1%24.7%−5.7 points
4 pCi/L and above45045.5%30.6%35.7%+14.9 points
Cass County ranked among the 72 Missouri counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Andrew County2 of 7215860.8%4.9 pCi/L
Buchanan County3 of 7257552.9%4.2 pCi/L
Saline County4 of 725549.1%3.7 pCi/L
Lafayette County5 of 7218446.7%3.5 pCi/L
Howell County6 of 7213845.7%3.5 pCi/L
Cass County7 of 7298845.5%3.5 pCi/L
Howard County8 of 726243.5%3.5 pCi/L
Marion County9 of 7228241.8%3.2 pCi/L
Barry County10 of 725541.8%3.1 pCi/L
Jefferson County11 of 722,65241.6%3.1 pCi/L
Stone County12 of 7213741.6%2.9 pCi/L
Cass County radon tests by year, against Missouri's pooled share
YearTestsAt or above 4 pCi/LMedianHighestMissouri, pooledChange from the row before
20232462.5%4.6 pCi/L17.9 pCi/L35.7%+1.2 points
20223161.3%6.2 pCi/L41.0 pCi/L40.8%+31.7 points
20212729.6%1.9 pCi/L21.1 pCi/L31.8%−17.5 points
20201747.1%3.6 pCi/L37.5 pCi/L33.2%+13.8 points
2019933.3%2.2 pCi/L16.1 pCi/L33.5%−20.5 points
20183953.8%4.9 pCi/L72.5 pCi/L42.1%+3.8 points
20174050.0%4.3 pCi/L80.3 pCi/L37.0%+5.9 points
20169344.1%3.5 pCi/L29.9 pCi/L29.8%−9.9 points
20155054.0%4.1 pCi/L26.2 pCi/L27.6%−3.4 points
20145457.4%4.8 pCi/L32.3 pCi/L34.4%First on file

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

Cass County, Geology

The ground under Cass County

Predicted

USGS's geologic map splits Cass County: 64.5% of its land is moderate radon potential and 35.5% high. The map puts 64.5% of Cass County in the area it calls Osage Plains and 35.5% in Northwestern Dissected Till Plains. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 13, in the high band (12 to 17).

USGS's geologic areas under Cass County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Osage PlainsOrdovician dolomite, sandstone, limestone, and shale.Moderate1164.5%
Northwestern Dissected Till PlainsPennsylvanian shales covered by thick loess.High1335.5%

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

Cass County beside the ground around it

Cass County has more high-potential ground than Missouri as a whole: 35.5% of its land against 8.2%. Of the 6 counties that border it, 2 have more high-potential ground, Johnson County, KS the most at 97.6%.

Share of land by USGS radon potential: Cass County, the 6 counties bordering it and Missouri
AreaEPA zoneLow potentialModerate potentialHigh potential
Cass CountyZone 1None64.5%35.5%
Bates CountyZone 2None99.7%0.3%
Jackson CountyZone 1None30.5%69.5%
Miami County, KSZone 2None68.6%31.4%
Johnson CountyZone 2None100%None
Johnson County, KSZone 1None2.4%97.6%
Henry CountyZone 2None100%None
Missouri115 counties, pooled by land areaVaries5.8%86.0%8.2%

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

Local help

Cass County, Local resources

Radon testing and mitigation in Cass County

Listed radon professionals by town: Kansas City, Lee's Summit

What Missouri's program says
Phone
573-751-6102
Email
radon@health.mo.gov

What it means

Cass County, Questions

Questions about radon in Cass County

Are radon levels high in Cass County?

In 2023, 62.5% of the radon tests reported to CDC for Cass County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.6 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 6 reported a higher share; pooled, the state comes to 30.6%.

Which counties border Cass County?

Cass County borders 6 counties: Bates County, MO, Jackson County, MO, Miami County, KS, Johnson County, MO, Johnson County, KS and Henry County, MO.

Products

Cass County, Products

Testing a home in Cass County

In Cass County, 45.5% of 988 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.6% pooled across Missouri. In Zone 1 the year-round level in Cass 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

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

Explore

Cass County, Bordering counties

Counties bordering Cass County

Calculated by Radon411

Cass County, Cities and towns

Cities and towns in Cass County

Cass County is growing: the Census Bureau puts it at 115,859 residents on July 1, 2025, up 7.1% from 108,160 in 2020. That works out to 166 people per square mile of land. Kansas City, the largest place on its list (521,220 residents in all), extends beyond Cass County, so no share of the total is worked out for it. CDC's 988 reported tests for 2008 to 2017 work out to 8.5 per 1,000 residents (2025 estimate), close to Missouri's 9.3.

From Kansas City to Riverview Estates, CDC publishes no figure by town: each reads Cass County's.

The 12 largest cities and towns in Cass County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Kansas Cityextends beyond Cass County521,220+2.6%Counted whole
Lee's Summitextends beyond Cass County107,514+5.9%Counted whole
Raymore26,633+15.8%23.0%
Belton26,193+9.0%22.6%
Harrisonville10,040−0.9%8.7%
Pleasant Hillextends beyond Cass County8,956+1.9%Counted whole
Peculiar6,365+12.7%5.5%
Greenwoodextends beyond Cass County6,315+4.8%Counted whole
Lake Winnebago1,869+27.5%1.6%
Garden City1,617−1.0%1.4%
Archie1,305+2.6%1.1%
Loch Lloyd1,090+24.9%0.9%
  • Drexel (part)
  • Cleveland
  • Freeman
  • Creighton
  • East Lynne
  • West Line
  • Strasburg
  • Lake Annette
  • Baldwin Park
  • Gunn City
  • Riverview Estates

23 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 Cass County is counted whole, so it has no share.

Cass County, Homes

Homes in Cass County

Cass County is a place of houses on their own lots: 78% of its 44,928 homes are detached single-family houses, against 70% across Missouri. Much of Cass County is recent building: 34% of its homes have gone up since 2000 and the middle year built is 1991, against 1978 for Missouri. Owners live in 76% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.

Homes in Cass County, Missouri, 2019 to 2023
HomesCass CountyMissouri
Housing units44,9282,809,501
Detached houses78%70%
In buildings of 5 or more4%13%
Mobile homes5%5%
Built before 196011%28%
Built since 200034%21%
Middle year built19911978
Owner-occupied76%68%

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