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Radon Levels in Isabella County, Michigan

EPA puts Isabella County in Zone 3, its lowest radon zone, and 16.4% of its 870 reported radon tests (2008 to 2017, laboratory totals) 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

    16.4%

    10.5 pts below MI

    Isabella
    16.4%
    Michigan
    26.9%

    870 tests, 2008 to 2017

  • Median result

    1.6pCi/L

    Below action level

    Isabella
    1.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    870

    31st of 82 by tests

    Isabella
    870
    Oakland
    16,224

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

  • Rank in Michigan

    45 of 82

    Middle half

    Isabella
    16.4%
    Lenawee
    56.7%

    By share, of 82 with 30+ tests

Read a result for Isabella County

Starts at Isabella County's median, 1.6 pCi/L

1.6pCi/L

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

EPA’s reading of 1.6 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. Isabella County's median reported result, 2008 to 2017.

Interpret this reading

The data

Isabella County, At a glance

Isabella County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Isabella County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 73% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Isabella County, 2008 to 2017, laboratory

Reported results by concentration band, Isabella County, 2008 to 2017, laboratory
Under 2 pCi/L: 59%2 to 4 pCi/L: 24%4 pCi/L and above: 17%

Of 870 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Isabella County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L51659.3%
2 to 4 pCi/L21124.3%
4 pCi/L and above14316.4%
What these figures count

These are the 870 tests reported to CDC for Isabella 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).

How to read these figures

Isabella County, Compared

Isabella County radon figures, compared

Calculated by Radon411

Isabella County's 870 reported tests over the 2008 to 2017 laboratory totals had a middle value of 1.6 pCi/L and a maximum of 39.4 pCi/L, and 16.4% reached 4 pCi/L. Michigan as a whole (83 Michigan counties, pooled) comes to 26.9%: 10.5 points higher than here.

Among its state's counties it ranks 45th of 82 Michigan counties with 30 or more tests for the same period. Statewide for the same period, Lenawee County reported the highest share (56.7%) and Muskegon County the lowest (3.2%).

Below the action level, 516 tests (59.3%) came in under 2 pCi/L, against 46.4% statewide, and 211 tests (24.3%) fell between 2 and 4, against 26.7% statewide. CDC's ten-year totals for Isabella County went from 1,017 tests (2005 to 2014) to 870 (2008 to 2017), the share going from 14.1% to 16.4%.

EPA's 1993 zone map puts Isabella County in Zone 3, a predicted county average under 2 pCi/L. USGS geology rates 73% of the county's land low radon potential.

Next door, the shares run from 5.3% in Midland County to 23.6% in Montcalm County, with Gladwin County, Clare County and Osceola County below Isabella County.

CDC also counts 28 tests taken after mitigation in Isabella County for the same period: tests in homes where a fix was already in.

Isabella County against Michigan, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Isabella County
Isabella County87016.4%1.6 pCi/LThis county
Michigan, pooled83 counties, pooled114,40726.9%Not pooled+10.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+19.3 points
Lenawee Countyhighest in the state1,90756.7%4.6 pCi/L+40.3 points
Muskegon Countylowest in the state6293.2%1.2 pCi/L−13.2 points
Montcalm County, MIborders it55023.6%2.1 pCi/L+7.2 points
Mecosta County, MIborders it61421.7%2.0 pCi/L+5.3 points
Gratiot County, MIborders it45716.8%1.7 pCi/L+0.4 points
Gladwin County, MIborders it24715.4%1.3 pCi/L−1.0 points
Clare County, MIborders it19814.1%1.6 pCi/L−2.3 points
Osceola County, MIborders it24610.6%1.7 pCi/L−5.8 points
Midland County, MIborders it2,0065.3%1.0 pCi/L−11.1 points
Where Isabella County's reported results fell, 2008 to 2017, laboratory, beside Michigan and the United States
ResultIsabella County testsIsabella County shareMichigan shareU.S. shareAgainst Michigan
Under 2 pCi/L51659.3%46.4%39.6%+12.9 points
2 to 4 pCi/L21124.3%26.7%24.7%−2.4 points
4 pCi/L and above14316.4%26.9%35.7%−10.5 points
Isabella County ranked among the 82 Michigan counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Ottawa County40 of 822,54616.8%1.6 pCi/L
Gratiot County41 of 8245716.8%1.7 pCi/L
Sanilac County42 of 8232516.6%1.6 pCi/L
Kent County43 of 828,44916.5%1.8 pCi/L
Manistee County44 of 8238816.5%1.6 pCi/L
Isabella County45 of 8287016.4%1.6 pCi/L
Alger County46 of 8218916.4%1.2 pCi/L
Gladwin County47 of 8224715.4%1.3 pCi/L
Emmet County48 of 8281515.2%1.6 pCi/L
Schoolcraft County49 of 826615.2%0.6 pCi/L
Ogemaw County50 of 8212015.0%2.0 pCi/L
Isabella County ten-year laboratory totals, against Michigan's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMichigan, pooledChange from the row before
2008 to 201787016.4%1.6 pCi/L39.4 pCi/L26.9%+1.2 points
2007 to 201691015.2%1.5 pCi/L39.4 pCi/L26.8%+1.1 points
2006 to 201598114.1%1.4 pCi/L39.4 pCi/L26.8%Level
2005 to 20141,01714.1%1.3 pCi/L39.4 pCi/L26.2%First on file

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

Isabella County, State data

Michigan's own radon test data

Measured

What Michigan's own agencies publish about radon tests in Isabella 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 Isabella County

Michigan EGLE publishes its figures by ZIP code, not by county. These are the 14 ZIP codes that lie wholly or partly in Isabella County, each with the state's own figures for it. Period: About 10 years to 2026-05-15.

ZIP codes in Isabella County
ZIP codeWhat the state reports
486170% greater than 4 pCi/L, median 1.5 pCi/L, 29 tests
486188% greater than 4 pCi/L, median 1.0 pCi/L, 13 tests
4862231% greater than 4 pCi/L, median 2.5 pCi/L, 16 tests
4863233% greater than 4 pCi/L, median 2.3 pCi/L, 12 tests
488298% greater than 4 pCi/L, median 1.8 pCi/L, 12 tests
4885820% greater than 4 pCi/L, median 2.1 pCi/L, 157 tests
488770% greater than 4 pCi/L, median 0.0 pCi/L, 5 tests
4887814% greater than 4 pCi/L, median 0.7 pCi/L, 7 tests
4888010% greater than 4 pCi/L, median 1.6 pCi/L, 42 tests
4888331% greater than 4 pCi/L, median 3.1 pCi/L, 32 tests
4889317% greater than 4 pCi/L, median 1.6 pCi/L, 30 tests
493050% greater than 4 pCi/L, median 1.3 pCi/L, 15 tests
493100% greater than 4 pCi/L, median 0.9 pCi/L, 6 tests
4934025% greater than 4 pCi/L, median 1.9 pCi/L, 12 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.

Isabella County, Geology

The ground under Isabella County

Predicted

USGS's geologic map splits Isabella County: 73.5% of its land is low radon potential and 26.5% moderate. The map puts 50.8% of Isabella County in the area it calls North-Central Michigan Basin and 26.5% in South-Central Michigan Basin, with one smaller area beside them. USGS gives the first a radon index of 8, in the low band (5 to 8), and the second 10, in the moderate band (9 to 11).

USGS's geologic areas under Isabella County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
North-Central Michigan BasinSandy and silty glacial deposits derived from sandstones, gray shales, limestones, and dolomites.Low850.8%
South-Central Michigan BasinSandy and silty glacial deposits derived from sandstones, gray shales, limestones, and dolomites.Moderate1026.5%
Glacial LakesSilt and clay glacial lake deposits.Low722.7%

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

Isabella County beside the ground around it

Across Michigan 9.6% of the land is rated high; none of Isabella County's is. Of the 7 counties that border it, 2 have more moderate-potential ground, Montcalm County the most at 97.4%.

Share of land by USGS radon potential: Isabella County, the 7 counties bordering it and Michigan
AreaEPA zoneLow potentialModerate potentialHigh potential
Isabella CountyZone 373.5%26.5%None
Midland CountyZone 3100%NoneNone
Mecosta CountyZone 379.3%20.7%None
Clare CountyZone 3100%NoneNone
Montcalm CountyZone 22.6%97.4%None
Gladwin CountyZone 3100%NoneNone
Gratiot CountyZone 357.9%42.1%None
Osceola CountyZone 3100%NoneNone
Michigan83 counties, pooled by land areaVaries45.0%44.3%9.6%

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

Local help

Isabella County, Local resources

Radon testing and mitigation in Isabella County

What Michigan's program says
Phone
800-723-6642
Email
Radon@Michigan.gov
Licensing of radon professionals
Michigan does not license or regulate radon testing and mitigation contractors.

What it means

Isabella County, Questions

Questions about radon in Isabella County

Are radon levels high in Isabella County?

Over the 2008 to 2017 laboratory totals, 16.4% of the radon tests reported to CDC for Isabella County, Michigan were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.6 pCi/L. Of 82 Michigan counties with 30 or more tests for the same period, 44 reported a higher share; pooled, the state comes to 26.9%.

Which counties border Isabella County?

Isabella County borders 7 counties: Midland County, Mecosta County, Clare County, Montcalm County, Gladwin County, Gratiot County and Osceola County.

Products

Isabella County, Products

Testing a home in Isabella County

In Isabella County, 16.4% of 870 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 Isabella County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Isabella County homes, compared

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Isabella County, Bordering counties

Counties bordering Isabella County

Calculated by Radon411

Isabella County, Cities and towns

Cities and towns in Isabella County

Isabella County's population has barely moved since 2020: 64,691 residents on July 1, 2025 against 64,518 then, by the Census Bureau's estimates. That works out to 113 people per square mile of land. Its largest town, Mount Pleasant, has 20,925 residents, 32.3% of the total. CDC's 870 reported tests for 2008 to 2017 work out to 13.4 per 1,000 residents (2025 estimate), close to Michigan's 11.3.

From Mount Pleasant to Rosebush, CDC publishes no figure by town: each reads Isabella County's.

The cities and towns in Isabella County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Mount Pleasant20,925−3.7%32.3%
Clareextends beyond Isabella County3,318+1.1%Counted whole
Lake Isabella1,952+3.1%3.0%
Shepherd1,513+1.5%2.3%
Rosebush361+1.4%0.6%

5 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 Isabella County is counted whole, so it has no share.

Isabella County, Homes

Homes in Isabella County

Of Isabella County's 28,600 homes, 59% are detached houses, against 72% across Michigan; 21% are in buildings of five or more homes. Much of Isabella County is recent building: 22% of its homes have gone up since 2000 and the middle year built is 1983, against 1972 for Michigan. 61% of occupied homes are lived in by their owner (Michigan: 73%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Isabella County, Michigan, 2019 to 2023
HomesIsabella CountyMichigan
Housing units28,6004,599,683
Detached houses59%72%
In buildings of 5 or more21%13%
Mobile homes9%5%
Built before 196021%36%
Built since 200022%15%
Middle year built19831972
Owner-occupied61%73%

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