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Radon Levels in Montgomery County, Missouri

EPA puts Montgomery 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

    12.8%

    17.8 pts below MO

    Montgomery
    12.8%
    Missouri
    30.6%

    47 tests, 2008 to 2017

  • Median result

    1.6pCi/L

    Below action level

    Montgomery
    1.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    47

    59th of 72 by tests

    Montgomery
    47
    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

    70 of 72

    Lowest quarter

    Montgomery
    12.8%
    Atchison
    69.9%

    By share, of 72 with 30+ tests

Read a result for Montgomery County

Starts at Montgomery County's median, 1.6 pCi/L

1.6pCi/L

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

EPA’s reading of 1.6 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Montgomery County's median reported result, 2008 to 2017.

Interpret this reading

The data

Montgomery County, At a glance

Montgomery County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Montgomery 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 Montgomery County, 2023

Share of reported tests at or above 4 pCi/L, by year, Montgomery County
Share of reported tests at or above 4 pCi/L, by year, Montgomery County
YearShare of reported tests at or above 4 pCi/L
20150.0%
20160.0%
20170.0%
2018100.0%
202050.0%
202133.3%
202214.3%
202350.0%

2023: 50.0%. 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 Montgomery 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

Montgomery County, Compared

Montgomery County radon figures, compared

Calculated by Radon411

Montgomery County reports fewer high tests than Missouri overall. 12.8% of its 47 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 17.8 points below the 30.6% pooled from 115 Missouri counties.

The newest figure, in 2023, counts only 2 tests (50.0% at or above 4 pCi/L), too few to compare, so this reading uses the 47-test figure.

Ordered from highest share down, it comes 70th of 72 Missouri counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Montgomery County sits 22.9 points below it.

Next door, the shares run from 15.4% in Osage County to 40.0% in Pike County. Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 12.8% share point the same way here.

Half the tests came in under 1.6 pCi/L and half over it; the single highest reached 35.6 pCi/L. The rest split 57.4% under 2 pCi/L and 29.8% from 2 to 4 (Missouri: 41.2% and 28.1%).

The busiest year on file was 2022, with 7 tests reported; the quietest, 2018, had 1.

Montgomery County against Missouri, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Montgomery County
Montgomery County4712.8%1.6 pCi/LThis county
Missouri, pooled115 counties, pooled58,52530.6%Not pooled+17.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+22.9 points
Atchison Countyhighest in the state10369.9%5.6 pCi/L+57.1 points
Vernon Countylowest in the state348.8%0.9 pCi/L−4.0 points
Pike County, MOborders it3540.0%2.9 pCi/L+27.2 points
Warren County, MOborders it28536.8%2.7 pCi/L+24.0 points
Lincoln County, MOborders it44433.6%2.2 pCi/L+20.8 points
Gasconade County, MOborders it4431.8%2.3 pCi/L+19.0 points
Audrain County, MOborders it12729.9%2.5 pCi/L+17.1 points
Callaway County, MOborders it19227.1%1.7 pCi/L+14.3 points
Osage County, MOborders it5215.4%1.5 pCi/L+2.6 points
Where Montgomery County's reported results fell, 2008 to 2017, laboratory, beside Missouri and the United States
ResultMontgomery County testsMontgomery County shareMissouri shareU.S. shareAgainst Missouri
Under 2 pCi/L2757.4%41.2%39.6%+16.2 points
2 to 4 pCi/L1429.8%28.1%24.7%+1.7 points
4 pCi/L and above612.8%30.6%35.7%−17.8 points
Montgomery 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
Linn County62 of 723718.9%1.8 pCi/L
Pulaski County63 of 7210718.7%1.3 pCi/L
Randolph County64 of 725817.2%1.8 pCi/L
Miller County65 of 7215416.9%1.9 pCi/L
St. Louis city66 of 721,87316.9%1.9 pCi/L
Osage County67 of 725215.4%1.5 pCi/L
Phelps County68 of 7220414.7%1.5 pCi/L
Crawford County68 of 723414.7%1.5 pCi/L
Montgomery County70 of 724712.8%1.6 pCi/L
Polk County71 of 727811.5%1.6 pCi/L
Vernon County72 of 72348.8%0.9 pCi/L
Montgomery County radon tests by year, against Missouri's pooled share
YearTestsAt or above 4 pCi/LMedianHighestMissouri, pooledChange from the row before
2023250.0%3.5 pCi/L4.4 pCi/L35.7%+35.7 points
2022714.3%2.6 pCi/L8.0 pCi/L40.8%−19.0 points
2021633.3%2.1 pCi/L6.3 pCi/L31.8%−16.7 points
2020250.0%2.3 pCi/L4.1 pCi/L33.2%−50.0 points
20181100.0%7.0 pCi/L7.0 pCi/L42.1%+100.0 points
201730.0%2.0 pCi/L3.5 pCi/L37.0%Level
201650.0%1.1 pCi/L3.2 pCi/L29.8%Level
201510.0%1.3 pCi/L1.3 pCi/L27.6%First on file

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

Montgomery County, Geology

The ground under Montgomery County

Predicted

USGS's geologic map puts all of Montgomery County's mapped land in one class: moderate radon potential. The map puts 62.0% of Montgomery County in the area it calls Dissected Till Plains and 38.0% in Salem Plateau. USGS gives both a radon index of 11, in the moderate band (9 to 11).

USGS's geologic areas under Montgomery County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Dissected Till PlainsTill-covered Pennsylvanian sandstone, shale, and limestone.Moderate1162.0%
Salem PlateauOrdovician dolomite, sandstone, limestone, and shale.Moderate1138.0%

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

Montgomery County beside the ground around it

Across Missouri 8.2% of the land is rated high; none of Montgomery County's is. Of the 7 counties that border it, 2 have more high-potential ground, Pike County the most at 4.4%.

Share of land by USGS radon potential: Montgomery County, the 7 counties bordering it and Missouri
AreaEPA zoneLow potentialModerate potentialHigh potential
Montgomery CountyZone 2None100%None
Warren CountyZone 2None100%None
Audrain CountyZone 2None100%None
Callaway CountyZone 2None100%None
Lincoln CountyZone 2None97.4%2.6%
Gasconade CountyZone 2None100%None
Pike CountyZone 2None95.6%4.4%
Osage 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

Montgomery County, Local resources

Radon testing and mitigation in Montgomery County

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

What it means

Montgomery County, Questions

Questions about radon in Montgomery County

Are radon levels high in Montgomery County?

In 2023, 50.0% of the radon tests reported to CDC for Montgomery County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 69 reported a higher share; pooled, the state comes to 30.6%.

Which counties border Montgomery County?

Montgomery County borders 7 counties: Warren County, Audrain County, Callaway County, Lincoln County, Gasconade County, Pike County and Osage County.

Products

Montgomery County, Products

Testing a home in Montgomery County

In Montgomery County, 12.8% of 47 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 Montgomery County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Montgomery County homes, compared

Explore

Montgomery County, Bordering counties

Counties bordering Montgomery County

Calculated by Radon411

Montgomery County, Cities and towns

Cities and towns in Montgomery County

The Census Bureau estimates 11,590 residents in Montgomery County for July 1, 2025, 297 more than in 2020 (+2.6%). That works out to 22 people per square mile of land. Its largest town, Montgomery City, has 2,782 residents, 24.0% of the total. Together its 9 incorporated places hold 53.6% of those residents; the other 46.4% live outside any of them. Reported testing is thin here: 47 tests over 2008 to 2017, or 4.1 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.

From Montgomery City to McKittrick, CDC publishes no figure by town: each reads Montgomery County's.

The cities and towns in Montgomery County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Montgomery City2,782−0.7%24.0%
Wellsville1,012+2.1%8.7%
Jonesburg864+19.3%7.5%
New Florence650+1.6%5.6%
Bellflower337+2.7%2.9%
High Hill186−0.5%1.6%
Middletown169−0.6%1.5%
Rhineland138−0.7%1.2%
McKittrick80+1.3%0.7%

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).

Montgomery County, Homes

Homes in Montgomery County

Montgomery County is a place of houses on their own lots: 80% of its 5,797 homes are detached single-family houses, against 70% across Missouri. Half of its homes were built before 1978, close to Missouri's 1978: 27% date from before 1960 and 20% from 2000 or later. 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 Montgomery County, Missouri, 2019 to 2023
HomesMontgomery CountyMissouri
Housing units5,7972,809,501
Detached houses80%70%
In buildings of 5 or more2%13%
Mobile homes12%5%
Built before 196027%28%
Built since 200020%21%
Middle year built19781978
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.