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Radon Levels in Wood County, Wisconsin

EPA puts Wood County in Zone 1, its highest radon zone, and 18.3% of its 208 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

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  • Share at 4+ pCi/L

    18.3%

    17.4 pts below WI

    Wood
    18.3%
    Wisconsin
    35.7%

    208 tests, 2023

  • Median result

    1.4pCi/L

    Below action level

    Wood
    1.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    208

    30th of 69 by tests

    Wood
    208
    Dane
    2,887

    Reported to CDC before any fix, 2023

  • 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 Wisconsin

    64 of 69

    Lowest quarter

    Wood
    18.3%
    Langlade
    65.8%

    By share, of 69 with 30+ tests

Read a result for Wood County

Starts at Wood 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. Wood County's median reported result, 2023.

Interpret this reading

The data

Wood County, At a glance

Wood County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Wood 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 54% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Wood County, 2023

Share of reported tests at or above 4 pCi/L, by year, Wood County
Share of reported tests at or above 4 pCi/L, by year, Wood County
YearShare of reported tests at or above 4 pCi/L
201443.2%
201552.7%
201635.8%
201732.6%
201938.2%
202036.0%
202139.6%
202236.4%
202318.3%

2023: 18.3%. Across these years the share ran from 18.3% to 52.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 208 tests reported to CDC for Wood 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

Wood County, Compared

Wood County radon figures, compared

Calculated by Radon411

Wood County's 208 reported tests in 2023 had a middle value of 1.4 pCi/L and a maximum of 21.4 pCi/L, and 18.3% reached 4 pCi/L. Wisconsin as a whole (72 Wisconsin counties, pooled) comes to 35.7%: 17.4 points higher than here.

Among its state's counties it ranks 64th 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, 128 tests (61.5%) came in under 2 pCi/L, against 41.4% statewide, and 42 tests (20.2%) fell between 2 and 4, against 23.0% statewide. The busiest year on file was 2016, with 240 tests reported; the quietest, 2021, had 91.

EPA's 1993 zone map puts Wood County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 54% of the county's land high radon potential.

Next door, the shares run from 10.0% in Juneau County to 51.9% in Marathon County, with Juneau County below Wood County. Over 9 years of annual figures the share fell 24.9 points, from 43.2% in 2014 to 18.3% in 2023; its peak was 52.7% in 2015.

Share of reported tests at or above 4 pCi/L by year, Wood County against Wisconsin2014 to 2023, years with 30 or more tests: Wood County 43.2% to 18.3%, the state's pooled share 35.7% in 2023.
Wood CountyWisconsin, pooled
Share of reported tests at or above 4 pCi/L by year, Wood County against Wisconsin: data table
YearTestsWood County, at or above 4 pCi/LWisconsin, pooled
201415543.2%51.1%
201516552.7%51.6%
201624035.8%45.2%
201719332.6%44.8%
201910238.2%42.9%
202011136.0%27.0%
20219139.6%39.9%
20229936.4%42.9%
202320818.3%35.7%
Wood County against Wisconsin, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Wood County
Wood County20818.3%1.4 pCi/LThis county
Wisconsin, pooled72 counties, pooled20,87935.7%Not pooled+17.4 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+15.1 points
Langlade Countyhighest in the state22565.8%6.0 pCi/L+47.5 points
Bayfield Countylowest in the state355.7%1.5 pCi/L−12.6 points
Marathon County, WIborders it34951.9%4.3 pCi/L+33.6 points
Jackson County, WIborders it9338.7%3.2 pCi/L+20.4 points
Portage County, WIborders it33435.6%3.0 pCi/L+17.3 points
Clark County, WIborders it7525.3%2.2 pCi/L+7.0 points
Adams County, WIborders it4820.8%1.7 pCi/L+2.5 points
Juneau County, WIborders it5010.0%1.1 pCi/L−8.3 points
Where Wood County's reported results fell, 2023, beside Wisconsin and the United States
ResultWood County testsWood County shareWisconsin shareU.S. shareAgainst Wisconsin
Under 2 pCi/L12861.5%41.4%41.4%+20.1 points
2 to 4 pCi/L4220.2%23.0%25.2%−2.8 points
4 pCi/L and above3818.3%35.7%33.4%−17.4 points
Wood 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
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
Taylor County63 of 693718.9%2.1 pCi/L
Wood County64 of 6920818.3%1.4 pCi/L
Pepin County65 of 696515.4%1.2 pCi/L
Marquette County66 of 694015.0%1.3 pCi/L
Juneau County67 of 695010.0%1.1 pCi/L
Douglas County68 of 69449.1%1.5 pCi/L
Bayfield County69 of 69355.7%1.5 pCi/L
Wood County radon tests by year, against Wisconsin's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWisconsin, pooledChange from the row before
202320818.3%1.4 pCi/L21.4 pCi/L35.7%−18.1 points
20229936.4%3.3 pCi/L15.7 pCi/L42.9%−3.2 points
20219139.6%3.4 pCi/L14.2 pCi/L39.9%+3.6 points
202011136.0%2.6 pCi/L32.0 pCi/L27.0%−2.2 points
201910238.2%2.6 pCi/L33.1 pCi/L42.9%+5.6 points
201719332.6%2.8 pCi/L60.9 pCi/L44.8%−3.2 points
201624035.8%2.8 pCi/L23.9 pCi/L45.2%−16.9 points
201516552.7%4.2 pCi/L61.0 pCi/L51.6%+9.5 points
201415543.2%3.6 pCi/L21.6 pCi/L51.1%First on file

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

Wood County, Geology

The ground under Wood County

Predicted

USGS's geologic map splits Wood County: 53.7% of its land is high radon potential and 46.3% moderate. The map puts 53.7% of Wood County in the area it calls Wolf River Batholith and 29.8% in Central Plain/Northern Highland, with one smaller area beside them. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Wood County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Wolf River BatholithPlutonic granitic rocks including quartz monzonite, syenite, monzonite, anorthosite.High1353.7%
Central Plain/Northern HighlandPre-Late Wisconsinan glacial deposits derived from sandstone and carbonate rocks.Moderate1029.8%
Driftless AreaCambrian sandstone.Moderate1016.5%

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

Wood County beside the ground around it

Wood County has more high-potential ground than Wisconsin as a whole: 53.7% of its land against 34.8%. Of the 6 counties that border it, 2 have more high-potential ground, Marathon County the most at 84.0%.

Share of land by USGS radon potential: Wood County, the 6 counties bordering it and Wisconsin
AreaEPA zoneLow potentialModerate potentialHigh potential
Wood CountyZone 1None46.3%53.7%
Portage CountyZone 1None24.0%76.0%
Marathon CountyZone 1None16.0%84.0%
Juneau CountyZone 2None100%None
Clark CountyZone 2None97.5%2.5%
Jackson CountyZone 2None100%None
Adams CountyZone 2None100%None
Wisconsin72 counties, pooled by land areaVaries1.4%63.5%34.8%

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

Local help

Wood County, Local resources

Radon testing and mitigation in Wood 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

Wood County, Questions

Questions about radon in Wood County

Are radon levels high in Wood County?

In 2023, 18.3% of the radon tests reported to CDC for Wood 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, 63 reported a higher share; pooled, the state comes to 35.7%.

Which counties border Wood County?

Wood County borders 6 counties: Portage County, Marathon County, Juneau County, Clark County, Jackson County and Adams County.

Products

Wood County, Products

Testing a home in Wood County

In Wood County, 18.3% of 208 tests reported to CDC in 2023 reached 4 pCi/L, against 35.7% pooled across Wisconsin. In Zone 1 the year-round level in Wood 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

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

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Wood County, Bordering counties

Counties bordering Wood County

Calculated by Radon411

Wood County, Cities and towns

Cities and towns in Wood County

Wood County's population has barely moved since 2020: 74,060 residents on July 1, 2025 against 74,180 then, by the Census Bureau's estimates. That works out to 93 people per square mile of land. Marshfield, the largest place on its list (18,980 residents in all), extends beyond Wood County, so no share of the total is worked out for it. CDC's 208 reported tests for 2023 work out to 2.8 per 1,000 residents (2025 estimate), close to Wisconsin's 3.5.

From Marshfield to Milladore, CDC publishes no figure by town: each reads Wood County's.

The cities and towns in Wood County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Marshfieldextends beyond Wood County18,980+0.2%Counted whole
Wisconsin Rapids18,654−1.1%25.2%
Nekoosa2,402−1.7%3.2%
Port Edwards1,761−1.0%2.4%
Biron860+2.1%1.2%
Pittsville820+0.6%1.1%
Hewitt798+0.4%1.1%
Auburndale724+3.1%1.0%
Vesper531+2.5%0.7%
Rudolph429−1.6%0.6%
Arpin297−1.0%0.4%
Milladoreextends beyond Wood County263−1.5%Counted whole

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 Wood County is counted whole, so it has no share.

Wood County, Homes

Homes in Wood County

Of Wood County's 34,662 homes, 74% are detached houses, against 66% across Wisconsin; 12% are in buildings of five or more homes. Half of its homes were built before 1973, close to Wisconsin's 1975: 35% date from before 1960 and 15% from 2000 or later. 73% 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 Wood County, Wisconsin, 2019 to 2023
HomesWood CountyWisconsin
Housing units34,6622,750,750
Detached houses74%66%
In buildings of 5 or more12%17%
Mobile homes4%3%
Built before 196035%34%
Built since 200015%20%
Middle year built19731975
Owner-occupied73%68%

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