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RankingsOhioHighest radon potential

Counties with the Highest Radon Potential in Ohio

The top 25 of 88 Ohio counties on GIS Map, ranked by EPA radon zone, where zone 1 carries the highest predicted indoor radon potential and zone 3 the lowest.

#CountyEPA radon zone
1Ashtabula County
2
2Athens County
2
3Brown County
2
4Clermont County
2
5Cuyahoga County
2
6Defiance County
2
7Erie County
2
8Fulton County
2
9Gallia County
2
10Geauga County
2
11Henry County
2
12Highland County
2
13Hocking County
2
14Jackson County
2
15Lake County
2
16Lawrence County
2
17Lorain County
2
18Lucas County
2
19Mahoning County
2
20Medina County
2
21Meigs County
2
22Monroe County
2
23Morgan County
2
24Noble County
2
25Ottawa County
2

Source: EPA Map of Radon Zones (September 2025). All counties with data are ranked. Estimates carry margins of error.

Citing this page: GIS Map, “Counties with the Highest Radon Potential in Ohio”, https://gismap.land/rankings/ohio/highest-radon-counties. Figures from EPA Map of Radon Zones (September 2025).

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