Locations and reports
Radon in Wausau, Wisconsin
EPA puts Marathon County, where Wausau is, in Zone 1, its highest radon zone, and high results are common there: 51.9% of the 349 radon tests reported to CDC (2023) 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
Share at 4+ pCi/L
51.9%
16.2 pts above WI
- Marathon
- 51.9%
- Wisconsin
- 35.7%
Marathon, 10th of 69 in WI, 2023
Median result
4.3pCi/L
Action level reached
- Marathon
- 4.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Marathon's tests, 2023
Nearest county
23.5%
Lincoln, 26 miles
- Lincoln
- 23.5%
- Marathon
- 51.9%
81 tests, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
Marathon, where Wausau is
Tests reported
349
In Marathon
- Marathon
- 349
- Lincoln
- 81
Reported to CDC before any fix, 2023
Read a result for Wausau
Starts at Marathon County's median, 4.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.3 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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. Marathon County's median reported result, 2023.
The data
Wausau, What is published
What is published for Wausau
Every figure for Wausau is a county's
Radon data is published by county, not by city, so for Wausau it is Marathon County's: its EPA zone (Zone 1) and the 349 tests reported to CDC for 2023. Only a test tells you about one home.
Wausau covers 19.2 square miles of land, all of it in Marathon County. About 40,188 people live there, 2,091 to the square mile.
Wausau, Counties
The county Wausau lies in
MeasuredMarathon County's EPA zone and the figures CDC publishes for it, 2023.
Marathon CountyZone 1Highest predicted potential
- 51.9%
- Reported tests at or above 4 pCi/L
- 4.3 pCi/L
- Median reported result
- 349 tests
- Tests reported to CDC
- 9
- Annual years on file
Marathon County ranks 10th of 69 Wisconsin counties with 30 or more tests for that period, 16.2 points above the 35.7% pooled across Wisconsin's counties, 18.5 points above the national pool of 33.4%.
The counties nearest Wausau with a CDC figure for 2023, measured from the middle of the city: Lincoln County (26 miles, 23.5% of 81 tests), Portage County (34 miles, 35.6% of 334 tests) and Langlade County (35 miles, 65.8% of 225 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 18.3% to 65.8%; the farthest of them, Clark County, is 50 miles away at 25.3%.
No business in the directory gives Wausau as its address; the Wisconsin list covers it. Wisconsin's other cities with a page of their own: Madison, Appleton, Green Bay and Oshkosh.
The counties around Wausau
By distance from the middle of Wausau; counties with 30 or more tests.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.
Wausau, Geology
The ground under Wausau
PredictedUSGS's geologic map puts all of Wausau's mapped land in one class: high radon potential. All of it lies in the area the map calls Wolf River Batholith, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Wolf River Batholith | Plutonic granitic rocks including quartz monzonite, syenite, monzonite, anorthosite. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Wausau beside its county and Wisconsin
Wausau sits on more high-potential ground than Marathon County as a whole: 100% of the city against 84.0% of the county. Wausau has more high-potential ground than Wisconsin as a whole: 100% of its land against 34.8%.
The map rates the ground, not the air in any home.
Wausau, Homes
Homes in Wausau
Of Wausau's 18,774 homes, 63% are detached houses, against 75% across Marathon County; 23% are in buildings of five or more homes. The homes are older than Marathon County's as a whole: half were built before 1961 (1977 for Marathon County), and 49% date from before 1960. 58% of occupied homes are lived in by their owner (Marathon County: 73%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Wausau | Marathon County | Wisconsin |
|---|---|---|---|
| Housing units | 18,774 | 60,296 | 2,750,750 |
| Detached houses | 63% | 75% | 66% |
| In buildings of 5 or more | 23% | 13% | 17% |
| Mobile homes | under 1% | 3% | 3% |
| Built before 1960 | 49% | 32% | 34% |
| Built since 2000 | 15% | 23% | 20% |
| Middle year built | 1961 | 1977 | 1975 |
| Owner-occupied | 58% | 73% | 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
Wausau, Local resources
Local resources for Wausau
Who to ask in Wisconsin: its radon program, test kits and professionals.
- Wisconsin's radon programWisconsin Department of Health Services, phone 1-888-569-7236.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We recommend starting with your regional Radon Information Center since many centers provide test kits for free or reduced cost, and often with laboratory fees covered.
- Compare kits
- Professionals in WisconsinRadon testers and mitigators in Wisconsin, each with how its listing was checked.
The program's own words on licensing are on the Wisconsin page.
What it means
Wausau, Questions
Questions about radon in Wausau
What radon zone is Wausau in?
Wausau takes its zone from Marathon County, which EPA puts in Zone 1, the map's highest class: a predicted county average above 4 pCi/L.
What are radon levels in Wausau?
51.9% of the 349 tests reported from Marathon County for 2023 were at or above 4 pCi/L, the level at which EPA says to fix a home: high results are ordinary around Wausau. The median reported result was 4.3 pCi/L.
Should I test my home in Wausau?
Yes. About 181 of the 349 tests reported from Marathon County were at or above 4 pCi/L. That is above Wisconsin's pooled 35.7%, and ranks Marathon County 10th of the 69 Wisconsin counties with 30 or more tests. No map says which homes those are. How to test a home.
What ground is Wausau built on, as far as radon goes?
USGS's geologic map puts all of Wausau on one named area, "Wolf River Batholith", rated high for radon potential, radon index 13.
Is radon higher in the counties around Wausau?
Some are and some are not. Against Marathon County's 51.9%, 3 of the 8 nearest counties with a figure report more and 5 less, from Wood County (18.3%, 40 miles off) to Langlade County (65.8%, 35 miles off).
The answers use the published figures of Marathon County, the county Wausau lies in.
Explore