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Radon Levels in McCook County, South Dakota

EPA puts McCook County in Zone 1, its highest radon zone, and high results are common there: 50.0% of the 30 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

    50.0%

    8.5 pts below SD

    McCook
    50.0%
    SD
    58.5%

    30 tests, 2008 to 2017

  • Median result

    3.9pCi/L

    Below action level

    McCook
    3.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    30

    23rd of 23 by tests

    McCook
    30
    Minnehaha
    1,920

    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 SD

    22 of 23

    Lowest quarter

    McCook
    50.0%
    Lake
    76.0%

    By share, of 23 with 30+ tests

Read a result for McCook County

Starts at McCook County's median, 3.9 pCi/L

3.9pCi/L

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

EPA’s reading of 3.9 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. McCook County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

McCook County, At a glance

McCook County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, McCook County, 2008 to 2017, laboratory
Under 2 pCi/L: 33%2 to 4 pCi/L: 17%4 pCi/L and above: 50%

Of 30 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, McCook County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1033.3%
2 to 4 pCi/L516.7%
4 pCi/L and above1550.0%
What these figures count

These are the 30 tests reported to CDC for McCook 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

McCook County, Compared

McCook County radon figures, compared

Calculated by Radon411

More than half: 50.0% of the 30 radon tests reported to CDC for McCook County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 22nd of 23 South Dakota counties with 30 or more tests for the same period. That is 8.5 points below the 58.5% pooled from 62 South Dakota counties.

The median result, 3.9 pCi/L, sits between 2 and EPA's 4 pCi/L action level, and the top reported result was 18.8 pCi/L. The rest split 33.3% under 2 pCi/L and 16.7% from 2 to 4 (South Dakota: 23.6% and 17.9%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 50.0% share point the same way here.

All 4 of its bordering counties with figures ran higher, led by Lake County at 76.0%; the lowest of them, Minnehaha County, reported 58.5%. Statewide for the same period, Lake County reported the highest share (76.0%) and Davison County the lowest (48.8%).

CDC's ten-year totals for McCook County went from 16 tests (2005 to 2014) to 30 (2008 to 2017), the share going from 56.3% to 50.0%.

Nationally, every county with a figure for the same period pools to 35.7%; McCook County sits 14.3 points above it.

McCook County against South Dakota, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from McCook County
McCook County3050.0%3.9 pCi/LThis county
South Dakota, pooled62 counties, pooled6,27558.5%Not pooled+8.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−14.3 points
Bon Homme Countyhighest in the state6274.2%7.2 pCi/L+24.2 points
Davison Countylowest in the state8448.8%3.8 pCi/L−1.2 points
Lake County, SDborders it5076.0%8.5 pCi/L+26.0 points
Hutchinson County, SDborders it3966.7%5.8 pCi/L+16.7 points
Turner County, SDborders it5858.6%4.8 pCi/L+8.6 points
Minnehaha County, SDborders it1,92058.5%4.8 pCi/L+8.5 points
Miner County, SDborders it450.0%3.9 pCi/LLevel
Hanson County, SDborders it825.0%2.8 pCi/L−25.0 points
Where McCook County's reported results fell, 2008 to 2017, laboratory, beside South Dakota and the United States
ResultMcCook County testsMcCook County shareSouth Dakota shareU.S. shareAgainst South Dakota
Under 2 pCi/L1033.3%23.6%39.6%+9.7 points
2 to 4 pCi/L516.7%17.9%24.7%−1.2 points
4 pCi/L and above1550.0%58.5%35.7%−8.5 points
McCook County ranked among the 23 South 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
Turner County13 of 235858.6%4.8 pCi/L
Minnehaha County14 of 231,92058.5%4.8 pCi/L
Lawrence County15 of 2316056.9%5.3 pCi/L
Lincoln County16 of 2379556.5%4.7 pCi/L
Grant County17 of 237855.1%5.0 pCi/L
Pennington County18 of 231,02953.6%4.3 pCi/L
Clay County19 of 238351.8%4.2 pCi/L
Meade County20 of 2319751.8%4.1 pCi/L
Union County21 of 2334851.1%4.1 pCi/L
McCook County22 of 233050.0%3.9 pCi/L
Davison County23 of 238448.8%3.8 pCi/L
McCook County ten-year laboratory totals, against South Dakota's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestSouth Dakota, pooledChange from the row before
2008 to 20173050.0%3.9 pCi/L18.8 pCi/L58.5%+7.9 points
2007 to 20161942.1%2.3 pCi/L16.2 pCi/L57.4%−7.9 points
2006 to 20151850.0%4.3 pCi/L16.2 pCi/L58.8%−6.3 points
2005 to 20141656.3%6.2 pCi/L16.2 pCi/L59.6%First on file

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

McCook County, Geology

The ground under McCook County

Predicted

USGS's geologic map puts all of McCook County's mapped land in one class: high radon potential. All of it lies in the area the map calls Missouri Coteau/James River Lowland/Coteau des Prairies, to which USGS gives a radon index of 14, in the high band (12 to 17).

USGS's geologic areas under McCook County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Missouri Coteau/James River Lowland/Coteau des PrairiesGlacial drift derived largely from Cretaceous marine shale.High14100%

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

McCook County beside the ground around it

McCook County has more high-potential ground than South Dakota as a whole: 100% of its land against 56.7%. Of the 6 counties that border it, none has as large a share of high-potential ground; Hanson County comes nearest at 100%.

Share of land by USGS radon potential: McCook County, the 6 counties bordering it and South Dakota
AreaEPA zoneLow potentialModerate potentialHigh potential
McCook CountyZone 1NoneNone100%
Hanson CountyZone 1NoneNone100%
Turner CountyZone 1NoneNone100%
Lake CountyZone 1NoneNone100%
Miner CountyZone 1NoneNone100%
Minnehaha CountyZone 1NoneNone99.9%
Hutchinson CountyZone 1NoneNone100%
South Dakota66 counties, pooled by land areaVaries1.0%42.3%56.7%

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

Local help

McCook County, Local resources

Radon testing and mitigation in McCook County

What South Dakota's program says
Phone
1-800-438-3367

What it means

McCook County, Questions

Questions about radon in McCook County

Are radon levels high in McCook County?

Over the 2008 to 2017 laboratory totals, 50.0% of the radon tests reported to CDC for McCook County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.9 pCi/L. Of 23 South Dakota counties with 30 or more tests for the same period, 21 reported a higher share; pooled, the state comes to 58.5%.

Which counties border McCook County?

McCook County borders 6 counties: Hanson County, Turner County, Lake County, Miner County, Minnehaha County and Hutchinson County.

Products

McCook County, Products

Testing a home in McCook County

In McCook County, 50.0% of 30 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 58.5% pooled across South Dakota. In Zone 1 the year-round level in McCook 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

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

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McCook County, Bordering counties

Counties bordering McCook County

Calculated by Radon411

McCook County, Cities and towns

Cities and towns in McCook County

McCook County is growing: the Census Bureau puts it at 5,964 residents on July 1, 2025, up 5.2% from 5,671 in 2020. That works out to 10 people per square mile of land. Its largest town, Salem, has 1,357 residents, 22.8% of the total. Together its 5 incorporated places hold 52.9% of those residents; the other 47.1% live outside any of them. CDC's 30 reported tests for 2008 to 2017 work out to 5.0 per 1,000 residents (2025 estimate), close to South Dakota's 6.7.

From Salem to Spencer, CDC publishes no figure by town: each reads McCook County's.

The cities and towns in McCook County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Salem1,357+2.0%22.8%
Canistota664+5.6%11.1%
Bridgewater517+1.6%8.7%
Montrose476+2.6%8.0%
Spencer139+2.2%2.3%

5 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).

McCook County, Homes

Homes in McCook County

McCook County is a place of houses on their own lots: 87% of its 2,467 homes are detached single-family houses, against 67% across South Dakota. The homes are older than South Dakota's as a whole: half were built before 1965 (1979 for South Dakota), and 47% date from before 1960. Owners live in 82% of the occupied homes (South Dakota: 69%), so for most households a test and a fix are their own to order.

Homes in McCook County, South Dakota, 2019 to 2023
HomesMcCook CountySouth Dakota
Housing units2,467402,364
Detached houses87%67%
In buildings of 5 or more2%16%
Mobile homes3%8%
Built before 196047%29%
Built since 200018%28%
Middle year built19651979
Owner-occupied82%69%

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