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Radon Levels in Brown County, Wisconsin

EPA puts Brown County in Zone 2, its middle radon zone, and 23.0% of its 551 reported radon tests (2023) were 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

    23.0%

    12.7 pts below WI

    Brown
    23.0%
    Wisconsin
    35.7%

    551 tests, 2023

  • Median result

    1.4pCi/L

    Below action level

    Brown
    1.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    551

    6th of 69 by tests

    Brown
    551
    Dane
    2,887

    Reported to CDC before any fix, 2023

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Wisconsin

    57 of 69

    Lowest quarter

    Brown
    23.0%
    Langlade
    65.8%

    By share, of 69 with 30+ tests

Read a result for Brown County

Starts at Brown County's median, 1.4 pCi/L

1.4pCi/L

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

EPA’s reading of 1.4 pCi/L

Below 2 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 below 2 pCi/L, the level at which EPA says a fix should be considered. Brown County's median reported result, 2023.

Interpret this reading

The data

Brown County, At a glance

Brown County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Brown County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 99% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Brown County, 2023

Share of reported tests at or above 4 pCi/L, by year, Brown County
Share of reported tests at or above 4 pCi/L, by year, Brown County
YearShare of reported tests at or above 4 pCi/L
201445.0%
201554.4%
201644.0%
201749.4%
201945.7%
202036.5%
202144.3%
202243.9%
202323.0%

2023: 23.0%. Across these years the share ran from 23.0% to 54.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 551 tests reported to CDC for Brown County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Brown County, Compared

Brown County radon figures, compared

Calculated by Radon411

Brown County's 551 reported tests in 2023 had a middle value of 1.4 pCi/L and a maximum of 52.6 pCi/L, and 23.0% reached 4 pCi/L. Wisconsin as a whole (72 Wisconsin counties, pooled) comes to 35.7%: 12.7 points higher than here.

Among its state's counties it ranks 57th of 69 Wisconsin counties with 30 or more tests for the same period. Statewide for the same period, Langlade County reported the highest share (65.8%) and Bayfield County the lowest (5.7%).

Below the action level, 328 tests (59.5%) came in under 2 pCi/L, against 41.4% statewide, and 96 tests (17.4%) fell between 2 and 4, against 23.0% statewide. The busiest year on file was 2016, with 586 tests reported; the quietest, 2022, had 253.

EPA's 1993 zone map puts Brown County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 99% of the county's land moderate radon potential.

Next door, the shares run from 31.1% in Manitowoc County to 57.0% in Shawano County. Over 9 years of annual figures the share fell 22.0 points, from 45.0% in 2014 to 23.0% in 2023; its peak was 54.4% in 2015.

CDC also counts 25 tests taken after mitigation in Brown County for the same period: tests in homes where a fix was already in.

Share of reported tests at or above 4 pCi/L by year, Brown County against Wisconsin2014 to 2023, years with 30 or more tests: Brown County 45.0% to 23.0%, the state's pooled share 35.7% in 2023.
Brown CountyWisconsin, pooled
Share of reported tests at or above 4 pCi/L by year, Brown County against Wisconsin: data table
YearTestsBrown County, at or above 4 pCi/LWisconsin, pooled
201457345.0%51.1%
201554854.4%51.6%
201658644.0%45.2%
201744549.4%44.8%
201934145.7%42.9%
202033436.5%27.0%
202127144.3%39.9%
202225343.9%42.9%
202355123.0%35.7%
Brown County against Wisconsin, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Brown County
Brown County55123.0%1.4 pCi/LThis county
Wisconsin, pooled72 counties, pooled20,87935.7%Not pooled+12.7 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+10.4 points
Langlade Countyhighest in the state22565.8%6.0 pCi/L+42.8 points
Bayfield Countylowest in the state355.7%1.5 pCi/L−17.3 points
Shawano County, WIborders it11457.0%5.0 pCi/L+34.0 points
Oconto County, WIborders it13052.3%4.5 pCi/L+29.3 points
Calumet County, WIborders it12251.6%4.4 pCi/L+28.6 points
Kewaunee County, WIborders it5644.6%3.7 pCi/L+21.6 points
Outagamie County, WIborders it33740.7%3.1 pCi/L+17.7 points
Manitowoc County, WIborders it20931.1%2.2 pCi/L+8.1 points
Where Brown County's reported results fell, 2023, beside Wisconsin and the United States
ResultBrown County testsBrown County shareWisconsin shareU.S. shareAgainst Wisconsin
Under 2 pCi/L32859.5%41.4%41.4%+18.1 points
2 to 4 pCi/L9617.4%23.0%25.2%−5.6 points
4 pCi/L and above12723.0%35.7%33.4%−12.7 points
Brown County ranked among the 69 Wisconsin counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Columbia County52 of 6916328.8%2.0 pCi/L
Waushara County53 of 697125.4%1.9 pCi/L
Clark County54 of 697525.3%2.2 pCi/L
Lincoln County55 of 698123.5%2.1 pCi/L
Burnett County56 of 695223.1%1.6 pCi/L
Brown County57 of 6955123.0%1.4 pCi/L
Monroe County58 of 6921322.5%2.2 pCi/L
Vilas County59 of 6910621.7%2.1 pCi/L
Adams County60 of 694820.8%1.7 pCi/L
Milwaukee County61 of 692,60520.2%1.5 pCi/L
Fond du Lac County62 of 6998419.6%1.4 pCi/L
Brown County radon tests by year, against Wisconsin's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWisconsin, pooledChange from the row before
202355123.0%1.4 pCi/L52.6 pCi/L35.7%−20.9 points
202225343.9%3.5 pCi/L53.2 pCi/L42.9%−0.4 points
202127144.3%3.4 pCi/L26.1 pCi/L39.9%+7.8 points
202033436.5%2.8 pCi/L61.7 pCi/L27.0%−9.2 points
201934145.7%3.6 pCi/L42.5 pCi/L42.9%−3.7 points
201744549.4%3.9 pCi/L63.4 pCi/L44.8%+5.4 points
201658644.0%3.4 pCi/L45.3 pCi/L45.2%−10.4 points
201554854.4%4.3 pCi/L69.1 pCi/L51.6%+9.4 points
201457345.0%3.5 pCi/L34.2 pCi/L51.1%First on file

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

Brown County, Geology

The ground under Brown County

Predicted

USGS's geologic map puts all of Brown County's mapped land in one class: moderate radon potential. 99.2% of it lies in the area the map calls Green Bay Lobe, to which USGS gives a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Brown County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Green Bay LobeGlacial deposits derived from carbonate and igneous rocks.Moderate1099.2%

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

Brown County beside the ground around it

Across Wisconsin 34.8% of the land is rated high; none of Brown County's is. Of the 6 counties that border it, 5 have more high-potential ground, Shawano County the most at 63.3%.

Share of land by USGS radon potential: Brown County, the 6 counties bordering it and Wisconsin
AreaEPA zoneLow potentialModerate potentialHigh potential
Brown CountyZone 2None99.2%None
Kewaunee CountyZone 226.5%60.7%12.1%
Manitowoc CountyZone 247.6%37.2%14.7%
Outagamie CountyZone 2None100%None
Calumet CountyZone 2None72.2%27.8%
Shawano CountyZone 1None36.7%63.3%
Oconto CountyZone 2None67.2%32.6%
Wisconsin72 counties, pooled by land areaVaries1.4%63.5%34.8%

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

Local help

Brown County, Local resources

Radon testing and mitigation in Brown County

What Wisconsin's program says
Phone
1-888-569-7236
Email
DHSRadon@dhs.wisconsin.gov
Licensing of radon professionals
The State of Wisconsin does not require contractors performing radon measurement or mitigation work to be state licensed or nationally certified.

What it means

Brown County, Questions

Questions about radon in Brown County

Are radon levels high in Brown County?

In 2023, 23.0% of the radon tests reported to CDC for Brown County, Wisconsin were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of 69 Wisconsin counties with 30 or more tests for the same period, 56 reported a higher share; pooled, the state comes to 35.7%.

Which counties border Brown County?

Brown County borders 6 counties: Kewaunee County, Manitowoc County, Outagamie County, Calumet County, Shawano County and Oconto County.

Products

Brown County, Products

Testing a home in Brown County

In Brown County, 23.0% of 551 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Brown County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Brown County homes, compared

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Brown County, Bordering counties

Counties bordering Brown County

Calculated by Radon411

Brown County, Cities and towns

Cities and towns in Brown County

The Census Bureau estimates 275,803 residents in Brown County for July 1, 2025, 6,851 more than in 2020 (+2.5%). That works out to 520 people per square mile of land. Its largest town, Green Bay, has 106,675 residents, 38.7% of the total. Reported testing is thin here: 551 tests over 2023, or 2.0 for every 1,000 residents (2025 estimate), where Wisconsin as a whole comes to 3.5.

From Green Bay to Denmark, CDC publishes no figure by town: each reads Brown County's.

The cities and towns in Brown County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Green Bay106,675−0.6%38.7%
De Pere25,590+0.7%9.3%
Howardextends beyond Brown County22,233+11.2%Counted whole
Ashwaubenon17,398+1.8%6.3%
Bellevue16,776+5.2%6.1%
Allouez13,838−2.1%5.0%
Suamico13,153+2.3%4.8%
Hobart11,674+14.2%4.2%
Wrightstownextends beyond Brown County4,169+30.7%Counted whole
Pulaskiextends beyond Brown County4,048+4.4%Counted whole
Denmark2,875+18.9%1.0%

11 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 Brown County is counted whole, so it has no share.

Brown County, Homes

Homes in Brown County

Of Brown County's 114,123 homes, 64% are detached houses, against 66% across Wisconsin; 20% are in buildings of five or more homes. Half of its homes were built before 1980, close to Wisconsin's 1975: 23% date from before 1960 and 23% from 2000 or later. 65% of occupied homes are lived in by their owner (Wisconsin: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Brown County, Wisconsin, 2019 to 2023
HomesBrown CountyWisconsin
Housing units114,1232,750,750
Detached houses64%66%
In buildings of 5 or more20%17%
Mobile homes1%3%
Built before 196023%34%
Built since 200023%20%
Middle year built19801975
Owner-occupied65%68%

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