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Radon Levels in Judith Basin County, Montana

EPA puts Judith Basin County in Zone 1, its highest radon zone, and high results are common there: 64.3% of the 42 radon tests reported to CDC (2008 to 2017, laboratory totals) 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

    64.3%

    18.8 pts above MT

    Judith Basin
    64.3%
    Montana
    45.5%

    42 tests, 2008 to 2017

  • Median result

    5.9pCi/L

    Action level reached

    Judith Basin
    5.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    42

    20th of 23 by tests

    Judith Basin
    42
    Missoula
    2,613

    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 Montana

    6 of 23

    Top quarter

    Judith Basin
    64.3%
    Richland
    78.6%

    By share, of 23 with 30+ tests

Read a result for Judith Basin County

Starts at Judith Basin County's median, 5.9 pCi/L

5.9pCi/L

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

EPA’s reading of 5.9 pCi/L

At or above 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Judith Basin County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Judith Basin County, At a glance

Judith Basin County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Judith Basin 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: High across 56% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Judith Basin County, 2008 to 2017, laboratory

Reported results by concentration band, Judith Basin County, 2008 to 2017, laboratory
Under 2 pCi/L: 5%2 to 4 pCi/L: 31%4 pCi/L and above: 64%

Of 42 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Judith Basin County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L24.8%
2 to 4 pCi/L1331.0%
4 pCi/L and above2764.3%
What these figures count

These are the 42 tests reported to CDC for Judith Basin County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Judith Basin County, Compared

Judith Basin County radon figures, compared

Calculated by Radon411

More than half: 64.3% of the 42 radon tests reported to CDC for Judith Basin County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 6th of 23 Montana counties with 30 or more tests for the same period. That is 18.8 points above the 45.5% pooled from 51 Montana counties.

The median result, 5.9 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 20.9 pCi/L. The rest split 4.8% under 2 pCi/L and 31.0% from 2 to 4 (Montana: 29.2% and 25.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 64.3% share point the same way here.

1 of its 2 bordering counties with figures ran higher, led by Fergus County at 72.4%; Cascade County reported 29.4%. Statewide for the same period, Richland County reported the highest share (78.6%) and Cascade County the lowest (29.4%).

CDC's ten-year totals for Judith Basin County went from 40 tests (2005 to 2014) to 42 (2008 to 2017), the share going from 62.5% to 64.3%.

Nationally, every county with a figure for the same period pools to 35.7%; Judith Basin County sits 28.6 points above it.

Judith Basin County against Montana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Judith Basin County
Judith Basin County4264.3%5.9 pCi/LThis county
Montana, pooled51 counties, pooled9,89345.5%Not pooled−18.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−28.6 points
Richland Countyhighest in the state4278.6%5.9 pCi/L+14.3 points
Flathead Countylowest in the state89137.8%3.0 pCi/L−26.5 points
Wheatland County, MTborders it1100.0%12.8 pCi/L+35.7 points
Fergus County, MTborders it7672.4%7.2 pCi/L+8.1 points
Chouteau County, MTborders it1154.5%5.5 pCi/L−9.8 points
Cascade County, MTborders it23529.4%1.7 pCi/L−34.9 points
Meagher County, MTborders it10.0%3.6 pCi/L−64.3 points
Where Judith Basin County's reported results fell, 2008 to 2017, laboratory, beside Montana and the United States
ResultJudith Basin County testsJudith Basin County shareMontana shareU.S. shareAgainst Montana
Under 2 pCi/L24.8%29.2%39.6%−24.4 points
2 to 4 pCi/L1331.0%25.2%24.7%+5.8 points
4 pCi/L and above2764.3%45.5%35.7%+18.8 points
Judith Basin County ranked among the 23 Montana counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Richland County1 of 234278.6%5.9 pCi/L
Sheridan County2 of 237075.7%6.5 pCi/L
Fergus County3 of 237672.4%7.2 pCi/L
Jefferson County4 of 236271.0%6.3 pCi/L
Silver Bow County5 of 2317470.1%6.0 pCi/L
Judith Basin County6 of 234264.3%5.9 pCi/L
Lewis and Clark County7 of 2346861.8%5.1 pCi/L
Park County8 of 2315060.0%5.3 pCi/L
Beaverhead County9 of 233759.5%5.0 pCi/L
Mineral County10 of 233056.7%5.1 pCi/L
Stillwater County11 of 235955.9%4.8 pCi/L
Judith Basin County ten-year laboratory totals, against Montana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMontana, pooledChange from the row before
2008 to 20174264.3%5.9 pCi/L20.9 pCi/L45.5%Level
2007 to 20164264.3%5.9 pCi/L20.9 pCi/L46.6%Level
2006 to 20154264.3%5.9 pCi/L20.9 pCi/L47.4%+1.8 points
2005 to 20144062.5%5.9 pCi/L20.9 pCi/L48.0%First on file

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

Judith Basin County, Geology

The ground under Judith Basin County

Predicted

USGS's geologic map splits Judith Basin County: 55.5% of its land is high radon potential and 44.5% moderate. The map puts 55.5% of Judith Basin County in the area it calls Northern Rocky Mountains and 44.5% in Plains and Mountains. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Judith Basin County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Rocky MountainsGranitic, metaigneous, metasedimentary rocks, valley fill colluvium and alluvium.High1355.5%
Plains and MountainsMarine and continental shale, siltstone, and sandstone of Cretaceous and Tertiary ages, and volcanic rocks.Moderate1044.5%

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

Judith Basin County beside the ground around it

Montana as a whole has more high-potential ground than Judith Basin County: 78.5% of its land, against 55.5% here. Of the 5 counties that border it, 4 have more high-potential ground, Cascade County the most at 96.9%.

Share of land by USGS radon potential: Judith Basin County, the 5 counties bordering it and Montana
AreaEPA zoneLow potentialModerate potentialHigh potential
Judith Basin CountyZone 1None44.5%55.5%
Meagher CountyZone 1None21.7%78.3%
Fergus CountyZone 1None33.1%66.9%
Wheatland CountyZone 2None91.4%8.6%
Cascade CountyZone 1None3.1%96.9%
Chouteau CountyZone 1None9.1%90.9%
Montana56 counties, pooled by land areaVariesNone21.5%78.5%

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

Local help

Judith Basin County, Local resources

Radon testing and mitigation in Judith Basin County

What Montana's program says
Phone
1-800-546-0483
Licensing of radon professionals
Montana DEQ does not certify or require proof of certification for the contractors listed.

What it means

Judith Basin County, Questions

Questions about radon in Judith Basin County

Are radon levels high in Judith Basin County?

Over the 2008 to 2017 laboratory totals, 64.3% of the radon tests reported to CDC for Judith Basin County, Montana were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.9 pCi/L. Of 23 Montana counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 45.5%.

Which counties border Judith Basin County?

Judith Basin County borders 5 counties: Meagher County, Fergus County, Wheatland County, Cascade County and Chouteau County.

Products

Judith Basin County, Products

Testing a home in Judith Basin County

In Judith Basin County, 64.3% of 42 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 45.5% pooled across Montana. In Zone 1 the year-round level in Judith Basin 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

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

Explore

Judith Basin County, Bordering counties

Counties bordering Judith Basin County

Calculated by Radon411

Judith Basin County, Cities and towns

Cities and towns in Judith Basin County

Judith Basin County is growing: the Census Bureau puts it at 2,162 residents on July 1, 2025, up 6.8% from 2,025 in 2020. Spread over its land, that is 1.2 people to the square mile. No town dominates: Stanford, the largest, has 427 residents, 19.8% of the total. Together its 2 incorporated places hold 28.6% of those residents; the other 71.4% live outside any of them. Testing is reported here more often than across the state: CDC's 42 reported tests for 2008 to 2017 come to 19.4 for every 1,000 residents (2025 estimate), against 8.6 for Montana.

From Stanford to Hobson, CDC publishes no figure by town: each reads Judith Basin County's.

The cities and towns in Judith Basin County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Stanford427+6.8%19.8%
Hobson191+7.3%8.8%

2 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).

Judith Basin County, Homes

Homes in Judith Basin County

Judith Basin County is a place of houses on their own lots: 85% of its 1,233 homes are detached single-family houses, against 69% across Montana. The homes are older than Montana's as a whole: half were built before 1968 (1980 for Montana), and 41% date from before 1960. Owners live in 75% of the occupied homes (Montana: 69%), so for most households a test and a fix are their own to order.

Homes in Judith Basin County, Montana, 2019 to 2023
HomesJudith Basin CountyMontana
Housing units1,233522,939
Detached houses85%69%
In buildings of 5 or more1%9%
Mobile homes13%10%
Built before 196041%26%
Built since 200012%27%
Middle year built19681980
Owner-occupied75%69%

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