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Radon Levels in Morton County, North Dakota

EPA puts Morton County in Zone 1, its highest radon zone, and high results are common there: 53.4% of the 268 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

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  • Share at 4+ pCi/L

    53.4%

    5.9 pts below ND

    Morton
    53.4%
    ND
    59.3%

    268 tests, 2008 to 2017

  • Median result

    4.2pCi/L

    Action level reached

    Morton
    4.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    268

    7th of 29 by tests

    Morton
    268
    Burleigh
    1,558

    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 ND

    22 of 29

    Middle half

    Morton
    53.4%
    Pembina
    82.5%

    By share, of 29 with 30+ tests

Read a result for Morton County

Starts at Morton County's median, 4.2 pCi/L

4.2pCi/L

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

EPA’s reading of 4.2 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. Morton County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Morton County, At a glance

Morton County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Morton 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 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Morton County, 2008 to 2017, laboratory

Reported results by concentration band, Morton County, 2008 to 2017, laboratory
Under 2 pCi/L: 24%2 to 4 pCi/L: 23%4 pCi/L and above: 53%

Of 268 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Morton County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L6423.9%
2 to 4 pCi/L6122.8%
4 pCi/L and above14353.4%
What these figures count

These are the 268 tests reported to CDC for Morton 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

Morton County, Compared

Morton County radon figures, compared

Calculated by Radon411

More than half: 53.4% of the 268 radon tests reported to CDC for Morton County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 22nd of 29 North Dakota counties with 30 or more tests for the same period. That is 5.9 points below the 59.3% pooled from 53 North Dakota counties.

The median result, 4.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 113.7 pCi/L. The rest split 23.9% under 2 pCi/L and 22.8% from 2 to 4 (North Dakota: 18.3% and 22.4%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 53.4% share point the same way here.

2 of its 3 bordering counties with figures ran higher, led by Mercer County at 63.5%; Burleigh County reported 51.1%. Statewide for the same period, Pembina County reported the highest share (82.5%) and Williams County the lowest (33.8%).

CDC's ten-year totals for Morton County went from 272 tests (2005 to 2014) to 268 (2008 to 2017), the share going from 51.1% to 53.4%.

Nationally, every county with a figure for the same period pools to 35.7%; Morton County sits 17.7 points above it. CDC also counts 20 tests taken after mitigation in Morton County for the same period: tests in homes where a fix was already in.

Morton County against North Dakota, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Morton County
Morton County26853.4%4.2 pCi/LThis county
North Dakota, pooled53 counties, pooled6,60759.3%Not pooled+5.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−17.7 points
Pembina Countyhighest in the state5782.5%9.3 pCi/L+29.1 points
Williams Countylowest in the state20433.8%2.9 pCi/L−19.6 points
Sioux County, NDborders it2100.0%9.3 pCi/L+46.6 points
Emmons County, NDborders it2986.2%7.1 pCi/L+32.8 points
Grant County, NDborders it2373.9%7.4 pCi/L+20.5 points
Oliver County, NDborders it1266.7%6.0 pCi/L+13.3 points
Mercer County, NDborders it8563.5%5.7 pCi/L+10.1 points
Stark County, NDborders it38662.4%5.1 pCi/L+9.0 points
Burleigh County, NDborders it1,55851.1%4.0 pCi/L−2.3 points
Where Morton County's reported results fell, 2008 to 2017, laboratory, beside North Dakota and the United States
ResultMorton County testsMorton County shareNorth Dakota shareU.S. shareAgainst North Dakota
Under 2 pCi/L6423.9%18.3%39.6%+5.6 points
2 to 4 pCi/L6122.8%22.4%24.7%+0.4 points
4 pCi/L and above14353.4%59.3%35.7%−5.9 points
Morton County ranked among the 29 North Dakota counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Stark County17 of 2938662.4%5.1 pCi/L
Ransom County18 of 2915161.6%5.8 pCi/L
Foster County19 of 293161.3%4.5 pCi/L
Cass County20 of 2986257.5%4.7 pCi/L
McKenzie County21 of 294156.1%4.8 pCi/L
Morton County22 of 2926853.4%4.2 pCi/L
Traill County23 of 293751.4%4.1 pCi/L
Burleigh County24 of 291,55851.1%4.0 pCi/L
Pierce County25 of 293948.7%3.8 pCi/L
Wells County26 of 298148.1%3.8 pCi/L
Ward County27 of 2944643.0%3.3 pCi/L
Morton County ten-year laboratory totals, against North Dakota's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestNorth Dakota, pooledChange from the row before
2008 to 201726853.4%4.2 pCi/L113.7 pCi/L59.3%+1.0 points
2007 to 201626952.4%4.1 pCi/L113.7 pCi/L58.7%−1.9 points
2006 to 201528054.3%4.3 pCi/L113.7 pCi/L56.3%+3.2 points
2005 to 201427251.1%4.0 pCi/L113.7 pCi/L54.0%First on file

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

Morton County, Geology

The ground under Morton County

Predicted

USGS's geologic map puts all of Morton County's mapped land in one class: high radon potential. 95.3% of it lies in the area the map calls Great Plains (Glaciated), to which USGS gives a radon index of 13, in the high band (12 to 17).

USGS's geologic areas under Morton County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Great Plains (Glaciated)Glacial deposits derived from Cretaceous shales containing higher than average amounts of uranium.High1395.3%
Great Plains (Unglaciated)Tertiary and Upper Cretaceous sandstones, shales, and locally, coal-bearing units.High134.7%

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

Morton County beside the ground around it

On high-potential ground Morton County is close to North Dakota as a whole: 100% of its land against 98.9%. Of the 7 counties that border it, none has as large a share of high-potential ground; Burleigh County comes nearest at 100%.

Share of land by USGS radon potential: Morton County, the 7 counties bordering it and North Dakota
AreaEPA zoneLow potentialModerate potentialHigh potential
Morton CountyZone 1NoneNone100%
Grant CountyZone 1None3.4%96.6%
Sioux CountyZone 1None21.4%78.6%
Oliver CountyZone 1NoneNone100%
Burleigh CountyZone 1NoneNone100%
Emmons CountyZone 1NoneNone100%
Mercer CountyZone 1NoneNone100%
Stark CountyZone 1NoneNone100%
North Dakota53 counties, pooled by land areaVariesNone1.1%98.9%

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

Local help

Morton County, Local resources

Radon testing and mitigation in Morton County

What North Dakota's program says
Phone
701-328-5166
Email
jOtto@nd.gov

What it means

Morton County, Questions

Questions about radon in Morton County

Are radon levels high in Morton County?

Over the 2008 to 2017 laboratory totals, 53.4% of the radon tests reported to CDC for Morton County, North Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.2 pCi/L. Of 29 North Dakota counties with 30 or more tests for the same period, 21 reported a higher share; pooled, the state comes to 59.3%.

Which counties border Morton County?

Morton County borders 7 counties: Grant County, Sioux County, Oliver County, Burleigh County, Emmons County, Mercer County and Stark County.

Products

Morton County, Products

Testing a home in Morton County

In Morton County, 53.4% of 268 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 59.3% pooled across North Dakota. In Zone 1 the year-round level in Morton 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

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

Explore

Morton County, Bordering counties

Counties bordering Morton County

Calculated by Radon411

Morton County, Cities and towns

Cities and towns in Morton County

The Census Bureau estimates 34,601 residents in Morton County for July 1, 2025, 1,277 more than in 2020 (+3.8%). That works out to 18 people per square mile of land. Mandan alone is home to 25,061 of them, 72.4% of the total. Together its 6 incorporated places hold 80.8% of those residents; the other 19.2% live outside any of them. CDC's 268 reported tests for 2008 to 2017 work out to 7.7 per 1,000 residents (2025 estimate), close to North Dakota's 8.3.

From Mandan to Almont, CDC publishes no figure by town: each reads Morton County's.

The cities and towns in Morton County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Mandan25,061+3.5%72.4%
New Salem1,082+10.3%3.1%
Hebron792−0.9%2.3%
Glen Ullin708−3.1%2.0%
Flasher230+6.0%0.7%
Almont93+4.5%0.3%

6 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).

Morton County, Homes

Homes in Morton County

Of Morton County's 15,334 homes, 68% are detached houses, against 57% across North Dakota; 16% are in buildings of five or more homes. Half of its homes were built before 1979, close to North Dakota's 1981: 23% date from before 1960 and 31% from 2000 or later. Owners live in 75% of the occupied homes (North Dakota: 63%), so for most households a test and a fix are their own to order.

Homes in Morton County, North Dakota, 2019 to 2023
HomesMorton CountyNorth Dakota
Housing units15,334374,866
Detached houses68%57%
In buildings of 5 or more16%25%
Mobile homes12%7%
Built before 196023%24%
Built since 200031%31%
Middle year built19791981
Owner-occupied75%63%

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