Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
Locations and reports
Radon Levels in St. Clair County, Michigan
EPA puts St. Clair County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 13.7% of 641 (2008 to 2017, laboratory totals) reached 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
13.7%
13.2 pts below MI
- St. Clair
- 13.7%
- Michigan
- 26.9%
641 tests, 2008 to 2017
Median result
1.5pCi/L
Below action level
- St. Clair
- 1.5 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
641
38th of 82 by tests
- St. Clair
- 641
- Oakland
- 16,224
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Michigan
55 of 82
Middle half
- St. Clair
- 13.7%
- Lenawee
- 56.7%
By share, of 82 with 30+ tests
Read a result for St. Clair County
Starts at St. Clair County's median, 1.5 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 1.5 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. St. Clair County's median reported result, 2008 to 2017.
The data
St. Clair County, At a glance
St. Clair County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Moderate across 95% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for St. Clair County, 2008 to 2017, laboratory
Under 2 pCi/L: 62%2 to 4 pCi/L: 24%4 pCi/L and above: 14%
Of 641 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 397 | 61.9% |
| 2 to 4 pCi/L | 156 | 24.3% |
| 4 pCi/L and above | 88 | 13.7% |
What these figures count
These are the 641 tests reported to CDC for St. Clair County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
St. Clair County, Compared
St. Clair County radon figures, compared
Calculated by Radon411St. Clair County reports fewer high tests than Michigan overall. 13.7% of its 641 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 13.2 points below the 26.9% pooled from 83 Michigan counties.
Ordered from highest share down, it comes 55th of 82 Michigan counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; St. Clair County sits 22.0 points below it.
Next door, the shares run from 13.4% in Macomb County to 33.4% in Lapeer County, with Macomb County below St. Clair County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 13.7% share point the same way here.
Half the tests came in under 1.5 pCi/L and half over it; the single highest reached 16.2 pCi/L. The rest split 61.9% under 2 pCi/L and 24.3% from 2 to 4 (Michigan: 46.4% and 26.7%).
CDC's ten-year totals for St. Clair County went from 581 tests (2005 to 2014) to 641 (2008 to 2017), the share going from 11.0% to 13.7%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
St. Clair County, State data
Michigan's own radon test data
MeasuredWhat Michigan's own agencies publish about radon tests in St. Clair County, with their period. These are not CDC's figures and are never added to them.
MeasuredState figures, not CDC's
What Michigan EGLE reports for the ZIP codes in St. Clair County
Michigan EGLE publishes its figures by ZIP code, not by county. These are the 21 ZIP codes that lie wholly or partly in St. Clair County, each with the state's own figures for it. Period: About 10 years to 2026-05-15.
| ZIP code | What the state reports |
|---|---|
| 48002 | 43% greater than 4 pCi/L, median 2.7 pCi/L, 7 tests |
| 48006 | 33% greater than 4 pCi/L, median 2.4 pCi/L, 12 tests |
| 48014 | 9% greater than 4 pCi/L, median 1.1 pCi/L, 11 tests |
| 48022 | 33% greater than 4 pCi/L, median 0.7 pCi/L, 6 tests |
| 48023 | 4 tests, figures not shown |
| 48027 | 14% greater than 4 pCi/L, median 1.7 pCi/L, 7 tests |
| 48028 | 2 tests, figures not shown |
| 48032 | 25% greater than 4 pCi/L, median 1.1 pCi/L, 8 tests |
| 48040 | 5% greater than 4 pCi/L, median 1.3 pCi/L, 38 tests |
| 48041 | 31% greater than 4 pCi/L, median 2.8 pCi/L, 13 tests |
| 48049 | 0% greater than 4 pCi/L, median 1.1 pCi/L, 14 tests |
| 48054 | 30% greater than 4 pCi/L, median 2.4 pCi/L, 27 tests |
| 48059 | 6% greater than 4 pCi/L, median 0.8 pCi/L, 18 tests |
| 48060 | 5% greater than 4 pCi/L, median 1.1 pCi/L, 76 tests |
| 48063 | 21% greater than 4 pCi/L, median 1.8 pCi/L, 14 tests |
| 48064 | 14% greater than 4 pCi/L, median 2.0 pCi/L, 7 tests |
| 48074 | 14% greater than 4 pCi/L, median 1.3 pCi/L, 22 tests |
| 48079 | 23% greater than 4 pCi/L, median 1.4 pCi/L, 40 tests |
| 48097 | 24% greater than 4 pCi/L, median 2.8 pCi/L, 17 tests |
| 48416 | 0% greater than 4 pCi/L, median 0.0 pCi/L, 5 tests |
| 48444 | 43% greater than 4 pCi/L, median 2.8 pCi/L, 21 tests |
- EGLE's figures cover first-time tests only, from organizations willing to provide data.
- EGLE does not publish figures for a ZIP code with fewer than 5 test results.
- EGLE says the map is not intended to decide whether a home should be tested: all homes should be tested.
- ZIP code boundaries are postal delivery areas, not legal or administrative boundaries.
- A ZIP code that crosses the county line is listed whole; its figures cover all of it.
Measured: Michigan EGLE data, About 10 years to 2026-05-15.
St. Clair County, Geology
The ground under St. Clair County
PredictedUSGS's geologic map puts all of St. Clair County's mapped land in one class: moderate radon potential. The map puts 54.0% of St. Clair County in the area it calls Antrim Shale-Lake deposits and 40.5% in South-Central Michigan Basin. USGS gives the first a radon index of 9 and the second 10, both in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Antrim Shale-Lake deposits | Antrim black shale covered by glacial lake deposits. | Moderate | 9 | 54.0% |
| South-Central Michigan Basin | Sandy and silty glacial deposits derived from sandstones, gray shales, limestones, and dolomites. | Moderate | 10 | 40.5% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
St. Clair County beside the ground around it
Across Michigan 9.6% of the land is rated high; none of St. Clair County's is. Every one of the 3 counties that border it has more moderate-potential ground, Lapeer County the most at 100%.
The map rates the ground, not the air in any home.
Local help
St. Clair County, Local resources
Radon testing and mitigation in St. Clair County
- Michigan Indoor Radon ProgramMichigan Indoor Radon Program, run by Michigan Department of Environment, Great Lakes, and Energy, does not license radon professionals, and answers questions about testing and mitigation in Michigan.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Michigan69 professionals are listed in Michigan.
What Michigan's program says
- Phone
- 800-723-6642
- Radon@Michigan.gov
- Licensing of radon professionals
Michigan does not license or regulate radon testing and mitigation contractors.
What it means
St. Clair County, Questions
Questions about radon in St. Clair County
Are radon levels high in St. Clair County?
Over the 2008 to 2017 laboratory totals, 13.7% of the radon tests reported to CDC for St. Clair County, Michigan were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.5 pCi/L. Of 82 Michigan counties with 30 or more tests for the same period, 54 reported a higher share; pooled, the state comes to 26.9%.
Which counties border St. Clair County?
St. Clair County borders 3 counties: Macomb County, Lapeer County and Sanilac County.
Products
St. Clair County, Products
Testing a home in St. Clair County
In St. Clair County, 13.7% of 641 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 26.9% pooled across Michigan. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in St. Clair County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
MonitorAranet
Radon One battery digital radon monitor with an e-ink screen
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
St. Clair County, Bordering counties
Counties bordering St. Clair County
Calculated by Radon411- Radon levels in Lapeer CountyEPA zone 2
33.4%at or above 4 pCi/L
Median 2.7 pCi/L · 649 tests · 19.7 points above St. Clair County
- Radon levels in Sanilac CountyEPA zone 2
16.6%at or above 4 pCi/L
Median 1.6 pCi/L · 325 tests · 2.9 points above St. Clair County
- Radon levels in Macomb CountyEPA zone 3
13.4%at or above 4 pCi/L
Median 1.6 pCi/L · 5,629 tests · 0.3 points below St. Clair County
St. Clair County, Cities and towns
Cities and towns in St. Clair County
St. Clair County's population has barely moved since 2020: 160,486 residents on July 1, 2025 against 160,386 then, by the Census Bureau's estimates. That works out to 222 people per square mile of land. No town dominates: Port Huron, the largest, has 28,273 residents, 17.6% of the total. Reported testing is thin here: 641 tests over 2008 to 2017, or 4.0 for every 1,000 residents (2025 estimate), where Michigan as a whole comes to 11.3.
From Port Huron to Emmett, CDC publishes no figure by town: each reads St. Clair County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Port Huron | 28,273 | −2.3% | 17.6% |
| Marysville | 9,868 | −1.3% | 6.1% |
| Richmondextends beyond St. Clair County | 5,927 | +1.0% | Counted whole |
| St. Clair | 5,833 | +6.8% | 3.6% |
| Algonac | 4,109 | −2.0% | 2.6% |
| Marine City | 3,997 | −1.8% | 2.5% |
| Capac | 1,943 | −2.2% | 1.2% |
| Yale | 1,873 | −1.3% | 1.2% |
| Memphisextends beyond St. Clair County | 1,091 | +1.3% | Counted whole |
| Emmett | 236 | −1.3% | 0.1% |
10 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 St. Clair County is counted whole, so it has no share.
St. Clair County, Homes
Homes in St. Clair County
St. Clair County is a place of houses on their own lots: 79% of its 72,467 homes are detached single-family houses, against 72% across Michigan. Half of its homes were built before 1975, close to Michigan's 1972: 35% date from before 1960 and 16% from 2000 or later. Owners live in 81% of the occupied homes (Michigan: 73%), so for most households a test and a fix are their own to order.
| Homes | St. Clair County | Michigan |
|---|---|---|
| Housing units | 72,467 | 4,599,683 |
| Detached houses | 79% | 72% |
| In buildings of 5 or more | 7% | 13% |
| Mobile homes | 6% | 5% |
| Built before 1960 | 35% | 36% |
| Built since 2000 | 16% | 15% |
| Middle year built | 1975 | 1972 |
| Owner-occupied | 81% | 73% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.