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Radon zones in Idaho

The EPA assigns every county in Idaho to one of three radon potential zones. 19 are in Zone 1, the highest category, home to about 24% of the state's residents.

44
Counties
19
Zone 1 counties
Predicted average above 4 pCi/L
20
Zone 2 counties
Predicted average 2-4 pCi/L
5
Zone 3 counties
Predicted average below 2 pCi/L

The map

Radon potential across Idaho

Every county in Idaho, 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 · 19Zone 2 · 20Zone 3 · 5

Hover a county · click to open it

County by county

All 44 Idaho counties

Zone 1 · > 4 pCi/LZone 2 · 2 - 4 pCi/LZone 3 · < 2 pCi/L
CountyZonePopulationCOPDSmokingLung ca. deaths
Benewah County110k10.2%16.8%39.0
Blaine County125k6.1%9.6%10.9
Boise County18,5177.7%11.7% -
Bonner County153k8.4%12.9%24.7
Boundary County114k9.3%14.7%32.5
Butte County12,75811.8%17.3% -
Camas County11,2327.8%12.4% -
Clark County18018.3%13.9% -
Clearwater County19,2149.3%14.1%35.5
Custer County14,5239.1%12.7% -
Elmore County130k7.1%13.8%41.0
Fremont County114k7.1%12.9%21.2
Gooding County116k8.7%15.0%28.3
Idaho County118k9.1%13.1%28.1
Kootenai County1185k7.2%12.1%27.8
Latah County141k5.5%10.0%18.7
Lemhi County18,4419.2%13.4%28.6
Shoshone County114k9.9%15.9%36.9
Valley County113k8.6%13.2%16.4
Ada County2525k5.3%10.4%23.7
Bannock County290k6.6%12.9%27.1
Bear Lake County26,7668.1%13.3% -
Bingham County250k7.1%14.0%22.6
Bonneville County2131k6.0%11.4%22.2
Canyon County2258k6.6%12.4%28.7
Caribou County27,2197.3%13.6% -
Cassia County226k6.9%13.0%13.7
Franklin County215k6.6%12.9% -
Jefferson County234k6.0%12.2%19.2
Jerome County225k8.0%15.7%23.5
Lincoln County25,4507.3%14.2% -
Madison County255k4.4%10.0% -
Minidoka County222k7.3%13.5%21.5
Oneida County24,9537.2%12.4% -
Owyhee County213k9.3%16.4%23.8
Payette County227k8.4%14.3%37.0
Power County28,2537.9%13.8% -
Teton County213k5.4%10.7% -
Twin Falls County295k7.3%13.3%25.5
Adams County34,90310.0%14.3% -
Gem County321k7.8%12.9%29.0
Lewis County33,73910.9%15.5%41.9
Nez Perce County343k7.9%13.5%29.2
Washington County311k10.0%15.2%35.5

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 Idaho

These 19 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