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Radon zones in Ohio

The EPA assigns every county in Ohio to one of three radon potential zones. 53 are in Zone 1, the highest category, home to about 63% of the state's residents.

88
Counties
53
Zone 1 counties
Predicted average above 4 pCi/L
35
Zone 2 counties
Predicted average 2-4 pCi/L
0
Zone 3 counties
Predicted average below 2 pCi/L

The map

Radon potential across Ohio

Every county in Ohio, filled by the zone the EPA assigns it. Zones follow geology rather than county lines, so the colour usually changes where the bedrock does, not where the border is.

Zone 1 · 53Zone 2 · 35Zone 3 · 0

Hover a county · click to open it

County by county

All 88 Ohio counties

Zone 1 · > 4 pCi/LZone 2 · 2 - 4 pCi/LZone 3 · < 2 pCi/L
CountyZonePopulationCOPDSmokingLung ca. deaths
Adams County128k11.8%21.9%66.5
Allen County1101k9.1%17.0%41.7
Ashland County152k9.6%17.7%30.9
Auglaize County146k8.1%15.3%43.6
Belmont County165k9.8%18.1%47.1
Butler County1393k7.2%14.6%39.5
Carroll County127k10.5%19.0%52.8
Champaign County139k8.5%16.4%43.0
Clark County1135k9.9%17.9%44.0
Clinton County142k9.3%17.7%51.3
Columbiana County1100k10.3%18.5%42.2
Coshocton County137k11.1%20.1%47.3
Crawford County142k10.3%18.3%43.1
Darke County151k9.7%17.7%36.5
Delaware County1232k4.9%10.1%25.3
Fairfield County1165k7.2%14.4%37.3
Fayette County129k10.2%19.9%51.9
Franklin County11.3M6.3%13.9%33.9
Greene County1170k6.6%12.3%34.8
Guernsey County138k10.6%19.0%57.6
Hamilton County1827k7.1%13.9%37.4
Hancock County175k7.5%14.5%36.5
Hardin County130k9.1%17.7%59.9
Harrison County114k10.6%19.0%55.5
Holmes County144k10.7%21.5%28.4
Huron County158k9.0%17.2%42.0
Jefferson County164k10.1%17.6%49.3
Knox County163k8.5%15.5%34.7
Licking County1183k7.6%15.4%43.1
Logan County146k9.2%17.5%43.5
Madison County145k7.8%16.5%46.2
Marion County165k10.0%19.6%45.2
Mercer County142k7.9%15.0%33.4
Miami County1111k8.0%15.3%39.1
Montgomery County1534k8.1%15.2%39.7
Morrow County136k9.2%17.8%49.0
Muskingum County186k9.6%18.1%47.7
Perry County136k10.1%19.3%54.8
Pickaway County161k8.5%17.9%46.5
Pike County127k12.5%22.9%59.6
Preble County141k9.1%17.0%45.0
Richland County1125k9.7%18.0%42.1
Ross County177k10.0%19.8%51.0
Seneca County155k8.5%16.4%36.9
Shelby County148k8.8%17.0%40.8
Stark County1373k8.8%17.1%38.6
Summit County1536k7.9%14.6%37.2
Tuscarawas County192k9.7%17.5%40.3
Union County170k5.7%12.6%27.9
Van Wert County129k8.8%16.5%37.8
Warren County1252k5.8%12.2%32.7
Wayne County1117k8.7%16.3%36.9
Wyandot County121k8.4%15.5%37.6
Ashtabula County297k11.0%20.1%41.7
Athens County263k7.7%15.2%43.6
Brown County244k10.4%19.7%50.5
Clermont County2212k7.6%15.6%42.4
Cuyahoga County21.2M7.7%14.8%34.9
Defiance County238k8.2%15.9%38.4
Erie County274k8.9%14.9%36.3
Fulton County242k8.1%15.1%34.5
Gallia County229k11.0%20.8%52.0
Geauga County295k7.6%12.8%26.7
Henry County228k8.3%15.8%38.2
Highland County244k10.4%19.5%62.8
Hocking County228k10.9%20.5%52.8
Jackson County233k10.5%20.1%54.8
Lake County2232k7.7%14.5%36.4
Lawrence County256k10.6%19.6%66.4
Lorain County2318k8.2%15.0%34.1
Lucas County2425k8.6%16.4%39.6
Mahoning County2226k9.5%16.9%38.1
Medina County2184k7.0%13.1%31.8
Meigs County222k12.9%22.5%49.6
Monroe County213k11.6%20.0%35.7
Morgan County214k11.1%19.5%48.7
Noble County214k11.8%18.5%29.0
Ottawa County240k8.5%14.0%43.4
Paulding County219k9.2%17.2%45.8
Portage County2163k7.6%14.5%37.3
Putnam County234k7.4%14.0%26.6
Sandusky County259k8.8%16.6%41.5
Scioto County272k11.4%20.8%60.2
Trumbull County2200k10.2%18.4%45.4
Vinton County212k11.4%21.2%68.2
Washington County259k9.6%17.0%45.9
Williams County237k9.5%17.8%39.9
Wood County2133k6.6%12.7%35.3

Zones from the EPA Map of Radon Zones. COPD and smoking are CDC PLACES model-based estimates of adult prevalence. Lung cancer death rates are age-adjusted deaths per 100,000 per year, 2019-2023, from NCI State Cancer Profiles. A dash means the source does not report a value for that county.

Highest potential

Zone 1 counties in Ohio

These 53 counties have a predicted average indoor radon screening level above the EPA action level. The EPA recommends every home in them be tested.

Other states

Radon zones elsewhere