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Radon Levels in Ottawa County, Ohio

EPA puts Ottawa County in Zone 2, its middle radon zone, and high results are common there: 40.3% of the 541 radon tests reported to CDC (2008 to 2017, laboratory totals) 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

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  • Share at 4+ pCi/L

    40.3%

    12.0 pts below OH

    Ottawa
    40.3%
    Ohio
    52.3%

    541 tests, 2008 to 2017

  • Median result

    2.9pCi/L

    Below action level

    Ottawa
    2.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    541

    38th of 79 by tests

    Ottawa
    541
    Franklin
    16,142

    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 Ohio

    64 of 79

    Lowest quarter

    Ottawa
    40.3%
    Pickaway
    81.4%

    By share, of 79 with 30+ tests

Read a result for Ottawa County

Starts at Ottawa 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. Ottawa County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Ottawa County, At a glance

Ottawa County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Ottawa 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 84% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Ottawa County, 2008 to 2017, laboratory
Under 2 pCi/L: 37%2 to 4 pCi/L: 23%4 pCi/L and above: 40%

Of 541 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Ottawa County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L19836.6%
2 to 4 pCi/L12523.1%
4 pCi/L and above21840.3%
What these figures count

These are the 541 tests reported to CDC for Ottawa 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

Ottawa County, Compared

Ottawa County radon figures, compared

Calculated by Radon411

In Ottawa County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (218 of 541) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 4.6 points higher. Across 88 Ohio counties pooled together, 52.3% of tests reached that level, so Ottawa County runs 12.0 points below its state.

Of 4 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 40.2% (Lucas County) to 59.2% (Sandusky County). By share, Ottawa County is 64th of 79 Ohio 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 61.5 pCi/L. Below the action level, 198 tests (36.6%) came in under 2 pCi/L, against 23.1% statewide, and 125 tests (23.1%) fell between 2 and 4, against 24.6% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 40.3% share point the same way here. USGS geology rates 84% of the county's land moderate radon potential. CDC also counts 129 tests taken after mitigation in Ottawa County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Ottawa County went from 343 tests (2005 to 2014) to 541 (2008 to 2017), the share going from 46.6% to 40.3%.

Ottawa County against Ohio, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Ottawa County
Ottawa County54140.3%2.9 pCi/LThis county
Ohio, pooled88 counties, pooled98,84052.3%Not pooled+12.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−4.6 points
Pickaway Countyhighest in the state18381.4%9.5 pCi/L+41.1 points
Cuyahoga Countylowest in the state10,09221.7%2.0 pCi/L−18.6 points
Sandusky County, OHborders it64959.2%5.0 pCi/L+18.9 points
Erie County, OHborders it1,65154.5%4.4 pCi/L+14.2 points
Wood County, OHborders it1,19245.5%3.5 pCi/L+5.2 points
Lucas County, OHborders it1,38140.2%3.0 pCi/L−0.1 points
Where Ottawa County's reported results fell, 2008 to 2017, laboratory, beside Ohio and the United States
ResultOttawa County testsOttawa County shareOhio shareU.S. shareAgainst Ohio
Under 2 pCi/L19836.6%23.1%39.6%+13.5 points
2 to 4 pCi/L12523.1%24.6%24.7%−1.5 points
4 pCi/L and above21840.3%52.3%35.7%−12.0 points
Ottawa County ranked among the 79 Ohio counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Fulton County59 of 796245.2%3.1 pCi/L
Guernsey County60 of 7911744.4%3.6 pCi/L
Medina County61 of 792,13943.4%3.5 pCi/L
Hardin County62 of 796743.3%3.4 pCi/L
Jackson County63 of 794841.7%3.3 pCi/L
Ottawa County64 of 7954140.3%2.9 pCi/L
Lucas County65 of 791,38140.2%3.0 pCi/L
Portage County66 of 791,66139.3%3.2 pCi/L
Summit County67 of 796,48638.7%3.1 pCi/L
Washington County68 of 7934938.1%3.1 pCi/L
Athens County69 of 7931838.1%3.1 pCi/L
Ottawa County ten-year laboratory totals, against Ohio's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestOhio, pooledChange from the row before
2008 to 201754140.3%2.9 pCi/L61.5 pCi/L52.3%−0.1 points
2007 to 201645040.4%2.8 pCi/L61.5 pCi/L52.8%−4.1 points
2006 to 201539844.5%3.3 pCi/L61.5 pCi/L52.9%−2.1 points
2005 to 201434346.6%3.4 pCi/L61.5 pCi/L52.4%First on file

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

Ottawa County, Geology

The ground under Ottawa County

Predicted

Most of the ground under Ottawa County is one class on USGS's geologic map: 84.2% of its land is moderate radon potential, with 12.1% high. The map puts 84.2% of Ottawa County in the area it calls Lake Plains and 12.1% in Till Plains. USGS gives the first a radon index of 10, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Ottawa County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Lake PlainsGlacial lake deposits, Devonian shale and limestone.Moderate1084.2%
Till PlainsGlacial deposits underlain by Ordovician through Devonian limestone and shale.High1412.1%

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

Ottawa County beside the ground around it

Ohio as a whole has more high-potential ground than Ottawa County: 62.8% of its land, against 12.1% here. Every one of the 4 counties that border it has more high-potential ground, Wood County the most at 91.7%.

Share of land by USGS radon potential: Ottawa County, the 4 counties bordering it and Ohio
AreaEPA zoneLow potentialModerate potentialHigh potential
Ottawa CountyZone 2None84.2%12.1%
Sandusky CountyZone 2None53.0%46.5%
Wood CountyZone 2None8.3%91.7%
Lucas CountyZone 2None85.6%13.9%
Erie CountyZone 2None56.5%41.3%
Ohio88 counties, pooled by land areaVariesNone37.2%62.8%

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

Local help

Ottawa County, Local resources

Radon testing and mitigation in Ottawa County

Listed radon businesses with an address in Ottawa County:

Listed radon professionals by town: Port Clinton

What Ohio's program says
Phone
614-728-0272
Email
indoor.radon@odh.ohio.gov
Licensing of radon professionals
This program licenses companies and persons directly involved with the radon testing and mitigation industry.

What it means

Ottawa County, Questions

Questions about radon in Ottawa County

Are radon levels high in Ottawa County?

Over the 2008 to 2017 laboratory totals, 40.3% of the radon tests reported to CDC for Ottawa County, Ohio were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.9 pCi/L. Of 79 Ohio counties with 30 or more tests for the same period, 63 reported a higher share; pooled, the state comes to 52.3%.

Which counties border Ottawa County?

Ottawa County borders 4 counties: Sandusky County, Wood County, Lucas County and Erie County.

Products

Ottawa County, Products

Testing a home in Ottawa County

In Ottawa County, 40.3% of 541 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 52.3% pooled across Ohio. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Ottawa County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Ottawa County homes, compared

Explore

Ottawa County, Bordering counties

Counties bordering Ottawa County

Calculated by Radon411

Ottawa County, Cities and towns

Cities and towns in Ottawa County

About 39,481 people live in Ottawa County by the Census Bureau's estimate for July 1, 2025, 822 fewer than in 2020 (−2.0%). That works out to 155 people per square mile of land. No town dominates: Port Clinton, the largest, has 5,875 residents, 14.9% of the total. Testing is reported here more often than across the state: CDC's 541 reported tests for 2008 to 2017 come to 13.7 for every 1,000 residents (2025 estimate), against 8.3 for Ohio.

From Port Clinton to Put-in-Bay, CDC publishes no figure by town: each reads Ottawa County's.

The cities and towns in Ottawa County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Port Clinton5,875−2.3%14.9%
Oak Harbor2,780−1.4%7.0%
Genoa2,167−2.8%5.5%
Elmoreextends beyond Ottawa County1,370−2.6%Counted whole
Marblehead829−2.2%2.1%
Rocky Ridge303−2.3%0.8%
Clay Center247−5.0%0.6%
Put-in-Bay152−2.6%0.4%

8 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 Ottawa County is counted whole, so it has no share.

Ottawa County, Homes

Homes in Ottawa County

Of Ottawa County's 28,762 homes, 73% are detached houses, against 69% across Ohio; 11% are mobile homes. Half of its homes were built before 1974, close to Ohio's 1970: 36% date from before 1960 and 18% from 2000 or later. Owners live in 84% of the occupied homes (Ohio: 67%), so for most households a test and a fix are their own to order.

Homes in Ottawa County, Ohio, 2019 to 2023
HomesOttawa CountyOhio
Housing units28,7625,271,573
Detached houses73%69%
In buildings of 5 or more7%15%
Mobile homes11%4%
Built before 196036%38%
Built since 200018%16%
Middle year built19741970
Owner-occupied84%67%

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