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Radon Levels in Ionia County, Michigan

EPA puts Ionia County in Zone 2, its middle radon zone, and 36.8% of its 1,391 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

    36.8%

    9.9 pts above MI

    Ionia
    36.8%
    Michigan
    26.9%

    1,391 tests, 2008 to 2017

  • Median result

    2.9pCi/L

    Below action level

    Ionia
    2.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    1,391

    22nd of 82 by tests

    Ionia
    1,391
    Oakland
    16,224

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Michigan

    10 of 82

    Top quarter

    Ionia
    36.8%
    Lenawee
    56.7%

    By share, of 82 with 30+ tests

Read a result for Ionia County

Starts at Ionia County's median, 2.9 pCi/L

2.9pCi/L

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

EPA’s reading of 2.9 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. Ionia County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Ionia County, At a glance

Ionia County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Ionia County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Ionia County, 2008 to 2017, laboratory
Under 2 pCi/L: 35%2 to 4 pCi/L: 28%4 pCi/L and above: 37%

Of 1,391 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Ionia County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L48634.9%
2 to 4 pCi/L39328.3%
4 pCi/L and above51236.8%
What these figures count

These are the 1,391 tests reported to CDC for Ionia 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

Ionia County, Compared

Ionia County radon figures, compared

Calculated by Radon411

In Ionia County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (512 of 1,391) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 1.1 points higher. Across 83 Michigan counties pooled together, 26.9% of tests reached that level, so Ionia County runs 9.9 points above its state.

Of 6 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 5 a smaller one; the spread is 16.5% (Kent County) to 38.5% (Clinton County). By share, Ionia County is 10th of 82 Michigan counties with 30 or more tests for the same period.

Half the tests came in under 2.9 pCi/L and half over it; the single highest reached 74.6 pCi/L. Below the action level, 486 tests (34.9%) came in under 2 pCi/L, against 46.4% statewide, and 393 tests (28.3%) fell between 2 and 4, against 26.7% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 36.8% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential. CDC also counts 90 tests taken after mitigation in Ionia County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Ionia County went from 1,502 tests (2005 to 2014) to 1,391 (2008 to 2017), the share going from 36.2% to 36.8%.

Ionia County against Michigan, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Ionia County
Ionia County1,39136.8%2.9 pCi/LThis county
Michigan, pooled83 counties, pooled114,40726.9%Not pooled−9.9 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−1.1 points
Lenawee Countyhighest in the state1,90756.7%4.6 pCi/L+19.9 points
Muskegon Countylowest in the state6293.2%1.2 pCi/L−33.6 points
Clinton County, MIborders it2,31338.5%3.1 pCi/L+1.7 points
Eaton County, MIborders it3,41134.4%2.8 pCi/L−2.4 points
Barry County, MIborders it1,61530.7%2.6 pCi/L−6.1 points
Montcalm County, MIborders it55023.6%2.1 pCi/L−13.2 points
Gratiot County, MIborders it45716.8%1.7 pCi/L−20.0 points
Kent County, MIborders it8,44916.5%1.8 pCi/L−20.3 points
Where Ionia County's reported results fell, 2008 to 2017, laboratory, beside Michigan and the United States
ResultIonia County testsIonia County shareMichigan shareU.S. shareAgainst Michigan
Under 2 pCi/L48634.9%46.4%39.6%−11.5 points
2 to 4 pCi/L39328.3%26.7%24.7%+1.6 points
4 pCi/L and above51236.8%26.9%35.7%+9.9 points
Ionia 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
Livingston County5 of 824,88543.1%3.4 pCi/L
Washtenaw County6 of 828,50041.3%3.2 pCi/L
Dickinson County7 of 8284339.3%3.1 pCi/L
Clinton County8 of 822,31338.5%3.1 pCi/L
Otsego County9 of 821,08038.2%3.2 pCi/L
Ionia County10 of 821,39136.8%2.9 pCi/L
Calhoun County11 of 821,64936.4%3.0 pCi/L
Iron County12 of 8226536.2%2.6 pCi/L
Tuscola County13 of 8236935.5%2.6 pCi/L
Eaton County14 of 823,41134.4%2.8 pCi/L
St. Joseph County15 of 821,06834.1%2.9 pCi/L
Ionia County ten-year laboratory totals, against Michigan's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestMichigan, pooledChange from the row before
2008 to 20171,39136.8%2.9 pCi/L74.6 pCi/L26.9%+0.1 points
2007 to 20161,48436.7%2.9 pCi/L74.6 pCi/L26.8%+0.7 points
2006 to 20151,57636.0%2.9 pCi/L74.6 pCi/L26.8%−0.2 points
2005 to 20141,50236.2%2.9 pCi/L74.6 pCi/L26.2%First on file

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

Ionia County, State data

Michigan's own radon test data

Measured

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

Michigan EGLE publishes its figures by ZIP code, not by county. These are the 20 ZIP codes that lie wholly or partly in Ionia County, each with the state's own figures for it. Period: About 10 years to 2026-05-15.

ZIP codes in Ionia County
ZIP codeWhat the state reports
4880927% greater than 4 pCi/L, median 2.6 pCi/L, 62 tests
4881522% greater than 4 pCi/L, median 1.7 pCi/L, 27 tests
4883430% greater than 4 pCi/L, median 2.9 pCi/L, 10 tests
4883727% greater than 4 pCi/L, median 2.6 pCi/L, 286 tests
4883833% greater than 4 pCi/L, median 2.4 pCi/L, 92 tests
488450% greater than 4 pCi/L, median 0.0 pCi/L, 5 tests
4884627% greater than 4 pCi/L, median 2.5 pCi/L, 137 tests
4884924% greater than 4 pCi/L, median 2.5 pCi/L, 58 tests
4885135% greater than 4 pCi/L, median 3.3 pCi/L, 17 tests
4886030% greater than 4 pCi/L, median 3.4 pCi/L, 10 tests
4886131% greater than 4 pCi/L, median 2.4 pCi/L, 16 tests
488650% greater than 4 pCi/L, median 1.7 pCi/L, 11 tests
4887347% greater than 4 pCi/L, median 3.2 pCi/L, 17 tests
4887545% greater than 4 pCi/L, median 3.5 pCi/L, 123 tests
4888117% greater than 4 pCi/L, median 1.8 pCi/L, 41 tests
4889043% greater than 4 pCi/L, median 3.6 pCi/L, 14 tests
4889439% greater than 4 pCi/L, median 3.1 pCi/L, 44 tests
4930216% greater than 4 pCi/L, median 1.9 pCi/L, 79 tests
4932531% greater than 4 pCi/L, median 3.0 pCi/L, 13 tests
4933121% greater than 4 pCi/L, median 2.0 pCi/L, 146 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.

Ionia County, Geology

The ground under Ionia County

Predicted

USGS's geologic map puts all of Ionia County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls South-Central Michigan Basin, to which USGS gives a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Ionia County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
South-Central Michigan BasinSandy and silty glacial deposits derived from sandstones, gray shales, limestones, and dolomites.Moderate10100%

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

Ionia County beside the ground around it

Across Michigan 9.6% of the land is rated high; none of Ionia County's is. Of the 6 counties that border it, 1 has more high-potential ground, Barry County the most at 7.1%.

Share of land by USGS radon potential: Ionia County, the 6 counties bordering it and Michigan
AreaEPA zoneLow potentialModerate potentialHigh potential
Ionia CountyZone 2None100%None
Clinton CountyZone 26.0%94.0%None
Montcalm CountyZone 22.6%97.4%None
Kent CountyZone 223.6%76.4%None
Eaton CountyZone 2None100%None
Barry CountyZone 2None92.9%7.1%
Gratiot CountyZone 357.9%42.1%None
Michigan83 counties, pooled by land areaVaries45.0%44.3%9.6%

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

Local help

Ionia County, Local resources

Radon testing and mitigation in Ionia County

Listed radon businesses with an address in Ionia County:

Listed radon professionals by town: Pewamo

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

Ionia County, Questions

Questions about radon in Ionia County

Are radon levels high in Ionia County?

Over the 2008 to 2017 laboratory totals, 36.8% of the radon tests reported to CDC for Ionia County, Michigan were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.9 pCi/L. Of 82 Michigan counties with 30 or more tests for the same period, 9 reported a higher share; pooled, the state comes to 26.9%.

Which counties border Ionia County?

Ionia County borders 6 counties: Clinton County, Montcalm County, Kent County, Eaton County, Barry County and Gratiot County.

Products

Ionia County, Products

Testing a home in Ionia County

In Ionia County, 36.8% of 1,391 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 26.9% pooled across Michigan. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Ionia County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Ionia County homes, compared

Explore

Ionia County, Bordering counties

Counties bordering Ionia County

Calculated by Radon411

Ionia County, Cities and towns

Cities and towns in Ionia County

Ionia County's population has barely moved since 2020: 66,557 residents on July 1, 2025 against 66,871 then, by the Census Bureau's estimates. That works out to 116 people per square mile of land. No town dominates: Ionia, the largest, has 12,208 residents, 18.3% of the total. Testing is reported here more often than across the state: CDC's 1,391 reported tests for 2008 to 2017 come to 20.9 for every 1,000 residents (2025 estimate), against 11.3 for Michigan.

From Ionia to Hubbardston, CDC publishes no figure by town: each reads Ionia County's.

The cities and towns in Ionia County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Ionia12,208−8.6%18.3%
Belding6,000+0.9%9.0%
Portland3,770−0.9%5.7%
Lake Odessa2,089+1.8%3.1%
Saranac1,386+0.9%2.1%
Lyons780+1.2%1.2%
Muir651+0.9%1.0%
Pewamo517+1.0%0.8%
Clarksville409+1.2%0.6%
Hubbardstonextends beyond Ionia County342+0.9%Counted whole

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 Ionia County is counted whole, so it has no share.

Ionia County, Homes

Homes in Ionia County

Ionia County is a place of houses on their own lots: 76% of its 24,746 homes are detached single-family houses, against 72% across Michigan. Half of its homes were built before 1972, close to Michigan's 1972: 41% date from before 1960 and 17% from 2000 or later. Owners live in 77% of the occupied homes (Michigan: 73%), so for most households a test and a fix are their own to order.

Homes in Ionia County, Michigan, 2019 to 2023
HomesIonia CountyMichigan
Housing units24,7464,599,683
Detached houses76%72%
In buildings of 5 or more8%13%
Mobile homes11%5%
Built before 196041%36%
Built since 200017%15%
Middle year built19721972
Owner-occupied77%73%

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