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Radon Levels in Audrain County, Missouri

EPA puts Audrain County in Zone 2, its middle radon zone, and only 2 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

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  • Share at 4+ pCi/L

    29.9%

    0.7 pts below MO

    Audrain
    29.9%
    Missouri
    30.6%

    127 tests, 2008 to 2017

  • Median result

    2.5pCi/L

    Below action level

    Audrain
    2.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    127

    34th of 72 by tests

    Audrain
    127
    St. Louis
    17,747

    Reported to CDC before any fix, 2008 to 2017

  • 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 Missouri

    39 of 72

    Middle half

    Audrain
    29.9%
    Atchison
    69.9%

    By share, of 72 with 30+ tests

Read a result for Audrain County

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

Interpret this readingWhat a fix costs

The data

Audrain County, At a glance

Audrain County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Audrain 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 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Audrain County, 2023

Share of reported tests at or above 4 pCi/L, by year, Audrain County
Share of reported tests at or above 4 pCi/L, by year, Audrain County
YearShare of reported tests at or above 4 pCi/L
201435.0%
20150.0%
20160.0%
201725.0%
2018100.0%
20200.0%
202122.2%
202237.5%
2023100.0%

2023: 100.0%. Across these years the share ran from 0.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 2 tests were reported to CDC for Audrain 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

Audrain County, Compared

Audrain County radon figures, compared

Calculated by Radon411

Audrain County's 127 reported tests over the 2008 to 2017 laboratory totals had a middle value of 2.5 pCi/L and a maximum of 24.8 pCi/L, and 29.9% reached 4 pCi/L. Missouri as a whole (115 Missouri counties, pooled) comes to 30.6%: 0.7 points higher than here.

The newest figure, in 2023, counts only 2 tests (100.0% at or above 4 pCi/L), too few to compare, so this reading uses the 127-test figure.

Among its state's counties it ranks 39th of 72 Missouri counties with 30 or more tests for the same period. Statewide for the same period, Atchison County reported the highest share (69.9%) and Vernon County the lowest (8.8%).

Below the action level, 57 tests (44.9%) came in under 2 pCi/L, against 41.2% statewide, and 32 tests (25.2%) fell between 2 and 4, against 28.1% statewide. The busiest year on file was 2014, with 20 tests reported; the quietest, 2018, had 1.

EPA's 1993 zone map puts Audrain County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.

Next door, the shares run from 12.8% in Montgomery County to 40.0% in Pike County, with Callaway County, Monroe County and Boone County below Audrain County.

Audrain County against Missouri, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Audrain County
Audrain County12729.9%2.5 pCi/LThis county
Missouri, pooled115 counties, pooled58,52530.6%Not pooled+0.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+5.8 points
Atchison Countyhighest in the state10369.9%5.6 pCi/L+40.0 points
Vernon Countylowest in the state348.8%0.9 pCi/L−21.1 points
Pike County, MOborders it3540.0%2.9 pCi/L+10.1 points
Ralls County, MOborders it4332.6%2.7 pCi/L+2.7 points
Callaway County, MOborders it19227.1%1.7 pCi/L−2.8 points
Monroe County, MOborders it3023.3%1.5 pCi/L−6.6 points
Boone County, MOborders it4,76721.7%1.9 pCi/L−8.2 points
Randolph County, MOborders it5817.2%1.8 pCi/L−12.7 points
Montgomery County, MOborders it4712.8%1.6 pCi/L−17.1 points
Where Audrain County's reported results fell, 2008 to 2017, laboratory, beside Missouri and the United States
ResultAudrain County testsAudrain County shareMissouri shareU.S. shareAgainst Missouri
Under 2 pCi/L5744.9%41.2%39.6%+3.7 points
2 to 4 pCi/L3225.2%28.1%24.7%−2.9 points
4 pCi/L and above3829.9%30.6%35.7%−0.7 points
Audrain 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
Gasconade County34 of 724431.8%2.3 pCi/L
Christian County35 of 7243631.7%1.9 pCi/L
Newton County36 of 7216731.1%2.5 pCi/L
Ste. Genevieve County37 of 727431.1%2.5 pCi/L
Benton County38 of 724930.6%2.0 pCi/L
Audrain County39 of 7212729.9%2.5 pCi/L
Scott County40 of 725129.4%2.2 pCi/L
Jasper County41 of 7225129.1%2.0 pCi/L
Adair County42 of 729227.2%1.8 pCi/L
Lawrence County43 of 727027.1%1.8 pCi/L
Callaway County44 of 7219227.1%1.7 pCi/L
Audrain County radon tests by year, against Missouri's pooled share
YearTestsAt or above 4 pCi/LMedianHighestMissouri, pooledChange from the row before
20232100.0%9.7 pCi/L12.0 pCi/L35.7%+62.5 points
2022837.5%3.0 pCi/L10.3 pCi/L40.8%+15.3 points
2021922.2%0.8 pCi/L8.3 pCi/L31.8%+22.2 points
202020.0%2.0 pCi/L2.9 pCi/L33.2%−100.0 points
20181100.0%6.1 pCi/L6.1 pCi/L42.1%+75.0 points
2017425.0%2.9 pCi/L5.6 pCi/L37.0%+25.0 points
201620.0%2.5 pCi/L3.2 pCi/L29.8%Level
201530.0%1.0 pCi/L3.6 pCi/L27.6%−35.0 points
20142035.0%2.0 pCi/L24.8 pCi/L34.4%First on file

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

Audrain County, Geology

The ground under Audrain County

Predicted

USGS's geologic map puts all of Audrain County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Dissected Till Plains, to which USGS gives a radon index of 11, in the moderate band (9 to 11).

USGS's geologic areas under Audrain County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Dissected Till PlainsTill-covered Pennsylvanian sandstone, shale, and limestone.Moderate11100%

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

Audrain County beside the ground around it

Across Missouri 8.2% of the land is rated high; none of Audrain County's is. Of the 7 counties that border it, 1 has more high-potential ground, Pike County the most at 4.4%.

Share of land by USGS radon potential: Audrain County, the 7 counties bordering it and Missouri
AreaEPA zoneLow potentialModerate potentialHigh potential
Audrain CountyZone 2None100%None
Monroe CountyZone 2None100%None
Montgomery CountyZone 2None100%None
Ralls CountyZone 2None100%None
Callaway CountyZone 2None100%None
Pike CountyZone 2None95.6%4.4%
Boone CountyZone 2None100%None
Randolph 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

Audrain County, Local resources

Radon testing and mitigation in Audrain County

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

What it means

Audrain County, Questions

Questions about radon in Audrain County

Are radon levels high in Audrain County?

In 2023, 100.0% of the radon tests reported to CDC for Audrain County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 9.7 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 38 reported a higher share; pooled, the state comes to 30.6%.

Which counties border Audrain County?

Audrain County borders 7 counties: Monroe County, Montgomery County, Ralls County, Callaway County, Pike County, Boone County and Randolph County.

Products

Audrain County, Products

Testing a home in Audrain County

In Audrain County, 29.9% of 127 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.6% pooled across Missouri. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Audrain County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Audrain County homes, compared

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Audrain County, Bordering counties

Counties bordering Audrain County

Calculated by Radon411

Audrain County, Cities and towns

Cities and towns in Audrain County

About 24,528 people live in Audrain County by the Census Bureau's estimate for July 1, 2025, 250 fewer than in 2020 (−1.0%). That works out to 35 people per square mile of land. Its largest town, Mexico, has 11,558 residents, 47.1% of the total. Reported testing is thin here: 127 tests over 2008 to 2017, or 5.2 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.

From Mexico to Vandiver, CDC publishes no figure by town: each reads Audrain County's.

The cities and towns in Audrain County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Mexico11,558+1.1%47.1%
Centraliaextends beyond Audrain County4,767+4.5%Counted whole
Vandaliaextends beyond Audrain County3,029−11.2%Counted whole
Laddonia508+1.4%2.1%
Martinsburg256+2.0%1.0%
Farber254−0.4%1.0%
Benton City107Level0.4%
Rush Hill104Level0.4%
Vandiver64Level0.3%

9 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 Audrain County is counted whole, so it has no share.

Audrain County, Homes

Homes in Audrain County

Audrain County is a place of houses on their own lots: 81% of its 10,566 homes are detached single-family houses, against 70% across Missouri. The homes are older than Missouri's as a whole: half were built before 1970 (1978 for Missouri), and 36% date from before 1960. 73% of occupied homes are lived in by their owner (Missouri: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Audrain County, Missouri, 2019 to 2023
HomesAudrain CountyMissouri
Housing units10,5662,809,501
Detached houses81%70%
In buildings of 5 or more4%13%
Mobile homes7%5%
Built before 196036%28%
Built since 200014%21%
Middle year built19701978
Owner-occupied73%68%

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