Locations and reports
Radon in Green Bay, Wisconsin
EPA puts Brown County, where Green Bay is, 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
Share at 4+ pCi/L
23.0%
12.7 pts below WI
- Brown
- 23.0%
- Wisconsin
- 35.7%
Brown, 57th of 69 in WI, 2023
Median result
1.4pCi/L
Below action level
- Brown
- 1.4 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Brown's tests, 2023
Nearest county
44.6%
Kewaunee, 18 miles
- Kewaunee
- 44.6%
- Brown
- 23.0%
56 tests, 2023
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
Brown, where Green Bay is
Tests reported
551
In Brown
- Brown
- 551
- Kewaunee
- 56
Reported to CDC before any fix, 2023
Read a result for Green Bay
Starts at Brown County's median, 1.4 pCi/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
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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.
The data
Green Bay, What is published
What is published for Green Bay
Every figure for Green Bay is a county's
Radon data is published by county, not by city, so for Green Bay it is Brown County's: its EPA zone (Zone 2) and the 551 tests reported to CDC for 2023. Only a test tells you about one home.
Green Bay covers 45.5 square miles of land, all of it in Brown County. About 106,675 people live there, 2,346 to the square mile.
Green Bay, Counties
The county Green Bay lies in
MeasuredBrown County's EPA zone and the figures CDC publishes for it, 2023.
Brown CountyZone 2Moderate predicted potential
- 23.0%
- Reported tests at or above 4 pCi/L
- 1.4 pCi/L
- Median reported result
- 551 tests
- Tests reported to CDC
- 9
- Annual years on file
Brown County ranks 57th of 69 Wisconsin counties with 30 or more tests for that period, 12.7 points below the 35.7% pooled across Wisconsin's counties, 10.4 points below the national pool of 33.4%.
Measured from the middle of Green Bay, the nearest counties with a CDC figure for 2023 are Kewaunee County (18 miles, 44.6% of 56 tests), Outagamie County (24 miles, 40.7% of 337 tests) and Manitowoc County (29 miles, 31.1% of 209 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 31.1% to 57.0%; the farthest of them, Winnebago County, is 45 miles away at 42.4%.
No business in the directory gives Green Bay as its address; the Wisconsin list covers it. Wisconsin's other cities with a page of their own: Madison, Appleton, Oshkosh and Wausau.
The counties around Green Bay
By distance from the middle of Green Bay; counties with 30 or more tests.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.
Green Bay, Geology
The ground under Green Bay
PredictedUSGS's geologic map puts all of Green Bay's mapped land in one class: moderate radon potential. 98.0% 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).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Green Bay Lobe | Glacial deposits derived from carbonate and igneous rocks. | Moderate | 10 | 98.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Green Bay beside its county and Wisconsin
The ground under Green Bay is close to Brown County's as a whole: 98.0% rated moderate against 99.2%. Across Wisconsin 34.8% of the land is rated high; none of Green Bay's is.
The map rates the ground, not the air in any home.
Green Bay, Homes
Homes in Green Bay
Of Green Bay's 45,797 homes, 58% are detached houses, against 64% across Brown County; 21% are in buildings of five or more homes. The homes are older than Brown County's as a whole: half were built before 1971 (1980 for Brown County), and 36% date from before 1960. 56% of occupied homes are lived in by their owner (Brown County: 65%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Green Bay | Brown County | Wisconsin |
|---|---|---|---|
| Housing units | 45,797 | 114,123 | 2,750,750 |
| Detached houses | 58% | 64% | 66% |
| In buildings of 5 or more | 21% | 20% | 17% |
| Mobile homes | 1% | 1% | 3% |
| Built before 1960 | 36% | 23% | 34% |
| Built since 2000 | 11% | 23% | 20% |
| Middle year built | 1971 | 1980 | 1975 |
| Owner-occupied | 56% | 65% | 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
Green Bay, Local resources
Local resources for Green Bay
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
Green Bay, Questions
Questions about radon in Green Bay
What radon zone is Green Bay in?
Green Bay takes its zone from Brown County, which EPA puts in Zone 2, the map's middle class: a predicted county average of 2 to 4 pCi/L.
What are radon levels in Green Bay?
Most tests near Green Bay come back under EPA's action level, but not all: 23.0% of Brown County's 551 tests for 2023 were at or above 4 pCi/L. The median reported result was 1.4 pCi/L.
Should I test my home in Green Bay?
Yes. In Brown County, about one reported test in 4 reached 4 pCi/L. That is below Wisconsin's pooled 35.7%, and still not a reason to skip it, and ranks Brown County 57th of the 69 Wisconsin counties with 30 or more tests. The number for one house comes only from testing it. How to test a home.
What ground is Green Bay built on, as far as radon goes?
USGS's geologic map puts all of Green Bay on one named area, "Green Bay Lobe", rated moderate for radon potential, radon index 10.
Is radon higher in the counties around Green Bay?
Higher, in every direction measured: all 8 of the nearest counties with a figure report a larger share of high tests than Brown County's 23.0%, up to Shawano County (57.0%, 43 miles off).
The answers use the published figures of Brown County, the county Green Bay lies in.
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