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Radon Levels in McLean County, North Dakota

EPA puts McLean County in Zone 1, its highest radon zone, and high results are common there: 63.2% of the 95 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

    63.2%

    3.9 pts above ND

    McLean
    63.2%
    ND
    59.3%

    95 tests, 2008 to 2017

  • Median result

    5.6pCi/L

    Action level reached

    McLean
    5.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    95

    13th of 29 by tests

    McLean
    95
    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

    16 of 29

    Middle half

    McLean
    63.2%
    Pembina
    82.5%

    By share, of 29 with 30+ tests

Read a result for McLean County

Starts at McLean County's median, 5.6 pCi/L

5.6pCi/L

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

EPA’s reading of 5.6 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. McLean County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

McLean County, At a glance

McLean County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of McLean 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 McLean County, 2008 to 2017, laboratory

Reported results by concentration band, McLean County, 2008 to 2017, laboratory
Under 2 pCi/L: 18%2 to 4 pCi/L: 19%4 pCi/L and above: 63%

Of 95 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, McLean County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1717.9%
2 to 4 pCi/L1818.9%
4 pCi/L and above6063.2%
What these figures count

These are the 95 tests reported to CDC for McLean 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

McLean County, Compared

McLean County radon figures, compared

Calculated by Radon411

More than half: 63.2% of the 95 radon tests reported to CDC for McLean County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 16th of 29 North Dakota counties with 30 or more tests for the same period. That is 3.9 points above the 59.3% pooled from 53 North Dakota counties.

The median result, 5.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 30.2 pCi/L. The rest split 17.9% under 2 pCi/L and 18.9% 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 63.2% share point the same way here.

3 of its 5 bordering counties with figures ran higher, led by Dunn County at 74.3%; Ward County reported 43.0%. 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 McLean County went from 100 tests (2005 to 2014) to 95 (2008 to 2017), the share going from 50.0% to 63.2%.

Nationally, every county with a figure for the same period pools to 35.7%; McLean County sits 27.5 points above it. CDC also counts 6 tests taken after mitigation in McLean County for the same period: tests in homes where a fix was already in.

McLean County against North Dakota, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from McLean County
McLean County9563.2%5.6 pCi/LThis county
North Dakota, pooled53 counties, pooled6,60759.3%Not pooled−3.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−27.5 points
Pembina Countyhighest in the state5782.5%9.3 pCi/L+19.3 points
Williams Countylowest in the state20433.8%2.9 pCi/L−29.4 points
Dunn County, NDborders it3574.3%7.1 pCi/L+11.1 points
Oliver County, NDborders it1266.7%6.0 pCi/L+3.5 points
Mountrail County, NDborders it4866.7%7.3 pCi/L+3.5 points
McHenry County, NDborders it2864.3%5.3 pCi/L+1.1 points
Mercer County, NDborders it8563.5%5.7 pCi/L+0.3 points
Sheridan County, NDborders it1154.5%4.2 pCi/L−8.7 points
Burleigh County, NDborders it1,55851.1%4.0 pCi/L−12.1 points
Ward County, NDborders it44643.0%3.3 pCi/L−20.2 points
Where McLean County's reported results fell, 2008 to 2017, laboratory, beside North Dakota and the United States
ResultMcLean County testsMcLean County shareNorth Dakota shareU.S. shareAgainst North Dakota
Under 2 pCi/L1717.9%18.3%39.6%−0.4 points
2 to 4 pCi/L1818.9%22.4%24.7%−3.5 points
4 pCi/L and above6063.2%59.3%35.7%+3.9 points
McLean 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
Barnes County11 of 298367.5%5.6 pCi/L
Dickey County12 of 297067.1%4.8 pCi/L
Mountrail County13 of 294866.7%7.3 pCi/L
Bottineau County14 of 2911164.0%5.7 pCi/L
Mercer County15 of 298563.5%5.7 pCi/L
McLean County16 of 299563.2%5.6 pCi/L
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
McLean 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 20179563.2%5.6 pCi/L30.2 pCi/L59.3%+6.1 points
2007 to 20169157.1%5.0 pCi/L22.2 pCi/L58.7%+4.7 points
2006 to 201510352.4%4.3 pCi/L22.2 pCi/L56.3%+2.4 points
2005 to 201410050.0%4.0 pCi/L22.2 pCi/L54.0%First on file

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

McLean County, Geology

The ground under McLean County

Predicted

USGS's geologic map puts all of McLean County's mapped land in one class: high radon potential. All 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 McLean 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.High13100%

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

McLean County beside the ground around it

On high-potential ground McLean County is close to North Dakota as a whole: 100% of its land against 98.9%. Of the 8 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: McLean County, the 8 counties bordering it and North Dakota
AreaEPA zoneLow potentialModerate potentialHigh potential
McLean CountyZone 1NoneNone100%
Oliver CountyZone 1NoneNone100%
Sheridan CountyZone 1NoneNone100%
Mercer CountyZone 1NoneNone100%
Burleigh CountyZone 1NoneNone100%
McHenry CountyZone 1NoneNone100%
Ward CountyZone 1NoneNone100%
Dunn CountyZone 1NoneNone100%
Mountrail 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

McLean County, Local resources

Radon testing and mitigation in McLean County

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

What it means

McLean County, Questions

Questions about radon in McLean County

Are radon levels high in McLean County?

Over the 2008 to 2017 laboratory totals, 63.2% of the radon tests reported to CDC for McLean County, North Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.6 pCi/L. Of 29 North Dakota counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 59.3%.

Which counties border McLean County?

McLean County borders 8 counties: Oliver County, Sheridan County, Mercer County, Burleigh County, McHenry County, Ward County, Dunn County and Mountrail County.

Products

McLean County, Products

Testing a home in McLean County

In McLean County, 63.2% of 95 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 McLean 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

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

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McLean County, Bordering counties

Counties bordering McLean County

Calculated by Radon411

McLean County, Cities and towns

Cities and towns in McLean County

McLean County's population has barely moved since 2020: 9,740 residents on July 1, 2025 against 9,763 then, by the Census Bureau's estimates. Spread over its land, that is 4.6 people to the square mile. No town dominates: Garrison, the largest, has 1,446 residents, 14.8% of the total. CDC's 95 reported tests for 2008 to 2017 work out to 9.8 per 1,000 residents (2025 estimate), close to North Dakota's 8.3.

From Garrison to Ruso, CDC publishes no figure by town: each reads McLean County's.

The cities and towns in McLean County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Garrison1,446−1.5%14.8%
Washburn1,254−3.2%12.9%
Underwood760−3.6%7.8%
Wiltonextends beyond McLean County702−2.6%Counted whole
Turtle Lake524−2.8%5.4%
Max321−2.7%3.3%
Riverdale221Level2.3%
Mercer122+35.6%1.3%
Butte69+1.5%0.7%
Benedict66+1.5%0.7%
Coleharbor64+8.5%0.7%
Ruso4LevelUnder 0.1%

12 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 McLean County is counted whole, so it has no share.

McLean County, Homes

Homes in McLean County

McLean County is a place of houses on their own lots: 82% of its 5,794 homes are detached single-family houses, against 57% across North Dakota. Half of its homes were built before 1975, close to North Dakota's 1981: 29% date from before 1960 and 23% from 2000 or later. Owners live in 83% of the occupied homes (North Dakota: 63%), so for most households a test and a fix are their own to order.

Homes in McLean County, North Dakota, 2019 to 2023
HomesMcLean CountyNorth Dakota
Housing units5,794374,866
Detached houses82%57%
In buildings of 5 or more5%25%
Mobile homes9%7%
Built before 196029%24%
Built since 200023%31%
Middle year built19751981
Owner-occupied83%63%

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