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Counties with the Highest Radon Potential in Idaho

The top 25 of 44 Idaho 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
1Adams County
3
2Gem County
3
3Lewis County
3
4Nez Perce County
3
5Washington County
3
6Ada County
2
7Bannock County
2
8Bear Lake County
2
9Bingham County
2
10Bonneville County
2
11Canyon County
2
12Caribou County
2
13Cassia County
2
14Franklin County
2
15Jefferson County
2
16Jerome County
2
17Lincoln County
2
18Madison County
2
19Minidoka County
2
20Oneida County
2
21Owyhee County
2
22Payette County
2
23Power County
2
24Teton County
2
25Twin Falls 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 Idaho”, https://gismap.land/rankings/idaho/highest-radon-counties. Figures from EPA Map of Radon Zones (September 2025).

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