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Radon Levels in Brookings County, South Dakota

EPA puts Brookings County in Zone 1, its highest radon zone, and high results are common there: 68.5% of the 356 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

    68.5%

    10.0 pts above SD

    Brookings
    68.5%
    SD
    58.5%

    356 tests, 2008 to 2017

  • Median result

    6.6pCi/L

    Action level reached

    Brookings
    6.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    356

    4th of 23 by tests

    Brookings
    356
    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

    6 of 23

    Top quarter

    Brookings
    68.5%
    Lake
    76.0%

    By share, of 23 with 30+ tests

Read a result for Brookings County

Starts at Brookings County's median, 6.6 pCi/L

6.6pCi/L

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

EPA’s reading of 6.6 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. Brookings County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Brookings County, At a glance

Brookings County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

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

Reported results by concentration band, Brookings County, 2008 to 2017, laboratory
Under 2 pCi/L: 20%2 to 4 pCi/L: 11%4 pCi/L and above: 69%

Of 356 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Brookings County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L7119.9%
2 to 4 pCi/L4111.5%
4 pCi/L and above24468.5%
What these figures count

These are the 356 tests reported to CDC for Brookings 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

Brookings County, Compared

Brookings County radon figures, compared

Calculated by Radon411

More than half: 68.5% of the 356 radon tests reported to CDC for Brookings County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 6th of 23 South Dakota counties with 30 or more tests for the same period. That is 10.0 points above the 58.5% pooled from 62 South Dakota counties.

The median result, 6.6 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 138.9 pCi/L. The rest split 19.9% under 2 pCi/L and 11.5% 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 68.5% share point the same way here.

2 of its 4 bordering counties with figures ran higher, led by Lake County at 76.0%; Lincoln County, MN reported 64.2%. 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 Brookings County went from 289 tests (2005 to 2014) to 356 (2008 to 2017), the share going from 66.4% to 68.5%.

Nationally, every county with a figure for the same period pools to 35.7%; Brookings County sits 32.8 points above it.

Brookings County against South Dakota, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Brookings County
Brookings County35668.5%6.6 pCi/LThis county
South Dakota, pooled62 counties, pooled6,27558.5%Not pooled−10.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−32.8 points
Bon Homme Countyhighest in the state6274.2%7.2 pCi/L+5.7 points
Davison Countylowest in the state8448.8%3.8 pCi/L−19.7 points
Hamlin County, SDborders it1376.9%6.3 pCi/L+8.4 points
Lake County, SDborders it5076.0%8.5 pCi/L+7.5 points
Deuel County, SDborders it2576.0%6.2 pCi/L+7.5 points
Pipestone County, MNborders it36071.4%5.8 pCi/L+2.9 points
Moody County, SDborders it2070.0%6.2 pCi/L+1.5 points
Kingsbury County, SDborders it4468.2%7.4 pCi/L−0.3 points
Lincoln County, MNborders it13764.2%6.8 pCi/L−4.3 points
Where Brookings County's reported results fell, 2008 to 2017, laboratory, beside South Dakota and the United States
ResultBrookings County testsBrookings County shareSouth Dakota shareU.S. shareAgainst South Dakota
Under 2 pCi/L7119.9%23.6%39.6%−3.7 points
2 to 4 pCi/L4111.5%17.9%24.7%−6.4 points
4 pCi/L and above24468.5%58.5%35.7%+10.0 points
Brookings 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
Lake County1 of 235076.0%8.5 pCi/L
Bon Homme County2 of 236274.2%7.2 pCi/L
Yankton County3 of 2311872.9%6.3 pCi/L
Brown County4 of 236271.0%5.9 pCi/L
Hughes County5 of 237170.4%5.7 pCi/L
Brookings County6 of 2335668.5%6.6 pCi/L
Kingsbury County7 of 234468.2%7.4 pCi/L
Brule County8 of 233767.6%6.4 pCi/L
Hutchinson County9 of 233966.7%5.8 pCi/L
Custer County10 of 2310865.7%6.2 pCi/L
Codington County11 of 237764.9%5.8 pCi/L
Brookings 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 201735668.5%6.6 pCi/L138.9 pCi/L58.5%+0.4 points
2007 to 201633568.1%6.6 pCi/L138.9 pCi/L57.4%+0.7 points
2006 to 201532867.4%6.4 pCi/L138.9 pCi/L58.8%+1.0 points
2005 to 201428966.4%6.1 pCi/L58.8 pCi/L59.6%First on file

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

Brookings County, Geology

The ground under Brookings County

Predicted

USGS's geologic map puts all of Brookings County's mapped land in one class: high radon potential. The map puts 68.7% of Brookings County in the area it calls Loess-Covered Drift Plains and 31.1% in Missouri Coteau/James River Lowland/Coteau des Prairies. USGS gives the first a radon index of 13 and the second 14, both in the high band (12 to 17).

USGS's geologic areas under Brookings County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Loess-Covered Drift PlainsPre-Illinoian and Illinoian glacial deposits, and loess.High1368.7%
Missouri Coteau/James River Lowland/Coteau des PrairiesGlacial drift derived largely from Cretaceous marine shale.High1431.1%

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

Brookings County beside the ground around it

Brookings County has more high-potential ground than South Dakota as a whole: 100% of its land against 56.7%. Of the 7 counties that border it, none has as large a share of high-potential ground; Deuel County comes nearest at 100%.

Share of land by USGS radon potential: Brookings County, the 7 counties bordering it and South Dakota
AreaEPA zoneLow potentialModerate potentialHigh potential
Brookings CountyZone 1NoneNone100%
Moody CountyZone 1NoneNone99.9%
Deuel CountyZone 1NoneNone100%
Lincoln County, MNZone 1NoneNone100%
Hamlin CountyZone 1NoneNone100%
Lake CountyZone 1NoneNone100%
Kingsbury CountyZone 1NoneNone100%
Pipestone County, MNZone 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

Brookings County, Local resources

Radon testing and mitigation in Brookings County

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

What it means

Brookings County, Questions

Questions about radon in Brookings County

Are radon levels high in Brookings County?

Over the 2008 to 2017 laboratory totals, 68.5% of the radon tests reported to CDC for Brookings County, South Dakota were at or above 4 pCi/L, and the median reported pre-mitigation result was 6.6 pCi/L. Of 23 South Dakota counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 58.5%.

Which counties border Brookings County?

Brookings County borders 7 counties: Moody County, SD, Deuel County, SD, Lincoln County, MN, Hamlin County, SD, Lake County, SD, Kingsbury County, SD and Pipestone County, MN.

Products

Brookings County, Products

Testing a home in Brookings County

In Brookings County, 68.5% of 356 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 Brookings 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

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

Explore

Brookings County, Bordering counties

Counties bordering Brookings County

Calculated by Radon411

Brookings County, Cities and towns

Cities and towns in Brookings County

Brookings County is growing: the Census Bureau puts it at 37,635 residents on July 1, 2025, up 9.6% from 34,338 in 2020. That works out to 48 people per square mile of land. Brookings alone is home to 25,355 of them, 67.4% of the total. CDC's 356 reported tests for 2008 to 2017 work out to 9.5 per 1,000 residents (2025 estimate), close to South Dakota's 6.7.

From Brookings to Bushnell, CDC publishes no figure by town: each reads Brookings County's.

The cities and towns in Brookings County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Brookings25,355+8.5%67.4%
Volga2,458+16.7%6.5%
Aurora1,286+22.1%3.4%
Arlingtonextends beyond Brookings County926LevelCounted whole
Elkton799+5.7%2.1%
White571+7.3%1.5%
Bruce219+4.3%0.6%
Sinai102+8.5%0.3%
Bushnell76+5.6%0.2%

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). A place that extends beyond Brookings County is counted whole, so it has no share.

Brookings County, Homes

Homes in Brookings County

Of Brookings County's 15,025 homes, 58% are detached houses, against 67% across South Dakota; 22% are in buildings of five or more homes. Half of its homes were built before 1983, close to South Dakota's 1979: 24% date from before 1960 and 34% from 2000 or later. 59% of occupied homes are lived in by their owner (South Dakota: 69%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Brookings County, South Dakota, 2019 to 2023
HomesBrookings CountySouth Dakota
Housing units15,025402,364
Detached houses58%67%
In buildings of 5 or more22%16%
Mobile homes7%8%
Built before 196024%29%
Built since 200034%28%
Middle year built19831979
Owner-occupied59%69%

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