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Radon in Madison, Wisconsin

EPA puts Dane County, where Madison is, in Zone 1, its highest radon zone, and 34.9% of its 2,887 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

    34.9%

    0.8 pts below WI

    Dane
    34.9%
    Wisconsin
    35.7%

    Dane, 42nd of 69 in WI, 2023

  • Median result

    2.5pCi/L

    Below action level

    Dane
    2.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of Dane's tests, 2023

  • Nearest county

    28.8%

    Columbia, 27 miles

    Columbia
    28.8%
    Dane
    34.9%

    163 tests, 2023

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    Dane, where Madison is

  • Tests reported

    2,887

    In Dane

    Dane
    2,887
    Columbia
    163

    Reported to CDC before any fix, 2023

Read a result for Madison

Starts at Dane County's median, 2.5 pCi/L

2.5pCi/L

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

EPA’s reading of 2.5 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. Dane County's median reported result, 2023.

Interpret this readingWhat a fix costs

The data

Madison, What is published

What is published for Madison

Information:

Every figure for Madison is a county's

Radon data is published by county, not by city, so for Madison it is Dane County's: its EPA zone (Zone 1) and the 2,887 tests reported to CDC for 2023. Only a test tells you about one home.

Madison covers 79.6 square miles of land, all of it in Dane County. About 286,233 people live there, 3,597 to the square mile.

Madison, Counties

The county Madison lies in

Measured

Dane County's EPA zone and the figures CDC publishes for it, 2023.

Dane CountyZone 1Highest predicted potential

34.9%
Reported tests at or above 4 pCi/L
2.5 pCi/L
Median reported result
2,887 tests
Tests reported to CDC
9
Annual years on file

Dane County ranks 42nd of 69 Wisconsin counties with 30 or more tests for that period, 0.8 points below the 35.7% pooled across Wisconsin's counties, 1.5 points above the national pool of 33.4%.

Measured from the middle of Madison, the nearest counties with a CDC figure for 2023 are Columbia County (27 miles, 28.8% of 163 tests), Green County (30 miles, 33.6% of 235 tests) and Jefferson County (32 miles, 44.3% of 296 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 28.8% to 61.0%; the farthest of them, Lafayette County, is 47 miles away at 52.2%.

No business in the directory gives Madison as its address; the Wisconsin list covers it. Wisconsin's other cities with a page of their own: Appleton, Green Bay, Oshkosh and Wausau.

The counties around Madison

By distance from the middle of Madison; counties with 30 or more tests.

Nearest counties to Madison with 30 or more tests
CountyDistanceTestsAt or above 4 pCi/LMedian
Columbia County27 mi16328.8%2.0 pCi/L
Green County30 mi23533.6%2.1 pCi/L
Jefferson County32 mi29644.3%3.5 pCi/L
Rock County33 mi45149.9%3.9 pCi/L
Sauk County37 mi24141.1%3.3 pCi/L
Iowa County38 mi14661.0%4.8 pCi/L
Dodge County42 mi25754.9%4.8 pCi/L
Lafayette County47 mi4652.2%4.2 pCi/L

Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.

Madison, Geology

The ground under Madison

Predicted

USGS's geologic map splits Madison: 63.6% of its land is moderate radon potential and 36.4% high. The map puts 63.6% of Madison in the area it calls Green Bay Lobe and 36.4% in Eastern Ridges and Lowlands. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 12, in the high band (12 to 17).

USGS's geologic areas under Madison
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Green Bay LobeGlacial deposits derived from carbonate and igneous rocks.Moderate1063.6%
Eastern Ridges and LowlandsGlacial deposits derived from Ordovician carbonate rocks.High1236.4%

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

Madison beside its county and Wisconsin

Dane County as a whole has more high-potential ground than Madison: 72.0% of the county against 36.4% of the city. On high-potential ground Madison is close to Wisconsin as a whole: 36.4% of its land against 34.8%.

Share of land by USGS radon potential: Madison, the county it lies in and Wisconsin
AreaEPA zoneLow potentialModerate potentialHigh potential
MadisonBy countyNone63.6%36.4%
Dane CountyZone 1None28.0%72.0%
Wisconsin72 counties, pooled by land areaVaries1.4%63.5%34.8%

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

Madison, Homes

Homes in Madison

Madison has 130,848 homes, and many share a building: 42% are in buildings of five or more, 41% are detached houses, against 51% across Dane County. Half of its homes were built before 1979, close to Dane County's 1985: 27% date from before 1960 and 27% from 2000 or later. Most occupied homes here are rented: owners live in 47% (Dane County: 58%). A tenant can run a test; a fix is the landlord's to make.

Homes in Madison, Dane County, Wisconsin, 2019 to 2023
HomesMadisonDane CountyWisconsin
Housing units130,848254,8802,750,750
Detached houses41%51%66%
In buildings of 5 or more42%33%17%
Mobile homes1%1%3%
Built before 196027%21%34%
Built since 200027%30%20%
Middle year built197919851975
Owner-occupied47%58%68%

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

Local help

Madison, Local resources

Local resources for Madison

Who to ask in Wisconsin: its radon program, test kits and professionals.

The program's own words on licensing are on the Wisconsin page.

What it means

Madison, Questions

Questions about radon in Madison

What radon zone is Madison in?

EPA's map puts Dane County, and with it Madison, in Zone 1, the map's highest class: a predicted county average above 4 pCi/L.

What are radon levels in Madison?

Around Madison, 34.9% of 2,887 tests reported from Dane County for 2023 reached 4 pCi/L or more, so a high result is no surprise here. The median reported result was 2.5 pCi/L.

Should I test my home in Madison?

Yes. Dane County reported about 1,008 of its 2,887 tests at or above 4 pCi/L. That is about what Wisconsin as a whole reports (35.7%), and ranks Dane County 42nd of the 69 Wisconsin counties with 30 or more tests. Which homes they were, no map can say. How to test a home.

What ground is Madison built on, as far as radon goes?

63.6% of Madison sits on what USGS's map calls "Green Bay Lobe", rated moderate for radon potential, radon index 10; another 36.4% is "Eastern Ridges and Lowlands", rated high for radon potential, radon index 12. So the ground changes within Madison itself.

Is radon higher in the counties around Madison?

It depends which way you go. 6 of the 8 nearest counties with a figure report a larger share than Dane County's 34.9% and 2 a smaller one: from Columbia County (28.8%, 27 miles off) to Iowa County (61.0%, 38 miles off).

The answers use the published figures of Dane County, the county Madison lies in.

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