Highest Radon Risk ZIP Codes in Idaho — 2026

Out of 145 ZIP codes with data in Idaho, these are the lowest-ranked areas for radon zone. See also: National ZIP Codes with Highest Radon Risk | All Idaho Rankings

Statistic	Value
ZIP codes ranked	145
Lowest value	Zone 1 (High)
Median value	Zone 1 (High)
State	Idaho

100 Lowest-Ranked ZIP Codes

Rank	ZIP Code	City	State	Radon Zone	Safety Score
1	83535	Juliaetta	ID	Zone 1 (High)	12/100
2	83633	King Hill	ID	Zone 1 (High)	33/100
3	83525	Elk City	ID	Zone 1 (High)	38/100
4	83203	Fort Hall	ID	Zone 1 (High)	40/100
5	83227	Clayton	ID	Zone 1 (High)	40/100
6	83229	Cobalt	ID	Zone 1 (High)	40/100
7	83235	Ellis	ID	Zone 1 (High)	40/100
8	83278	Stanley	ID	Zone 1 (High)	40/100
9	83322	Corral	ID	Zone 1 (High)	40/100
10	83337	Hill City	ID	Zone 1 (High)	40/100
11	83421	Chester	ID	Zone 1 (High)	40/100
12	83433	Macks Inn	ID	Zone 1 (High)	40/100
13	83446	Spencer	ID	Zone 1 (High)	40/100
14	83463	Gibbonsville	ID	Zone 1 (High)	40/100
15	83464	Leadore	ID	Zone 1 (High)	40/100
16	83465	Lemhi	ID	Zone 1 (High)	40/100
17	83468	Tendoy	ID	Zone 1 (High)	40/100
18	83533	Greencreek	ID	Zone 1 (High)	40/100
19	83542	Lucile	ID	Zone 1 (High)	40/100
20	83547	Pollock	ID	Zone 1 (High)	40/100
21	83602	Banks	ID	Zone 1 (High)	40/100
22	83627	Hammett	ID	Zone 1 (High)	40/100
23	83637	Lowman	ID	Zone 1 (High)	40/100
24	83657	Ola	ID	Zone 1 (High)	40/100
25	83666	Placerville	ID	Zone 1 (High)	40/100
26	83670	Sweet	ID	Zone 1 (High)	40/100
27	83671	Warren	ID	Zone 1 (High)	40/100
28	83809	Careywood	ID	Zone 1 (High)	40/100
29	83824	Desmet	ID	Zone 1 (High)	40/100
30	83826	Eastport	ID	Zone 1 (High)	40/100
31	83840	Kootenai	ID	Zone 1 (High)	40/100
32	83847	Naples	ID	Zone 1 (High)	40/100
33	83848	Nordman	ID	Zone 1 (High)	40/100
34	83853	Porthill	ID	Zone 1 (High)	40/100
35	83865	Colburn	ID	Zone 1 (High)	40/100
36	83866	Santa	ID	Zone 1 (High)	40/100
37	83868	Smelterville	ID	Zone 1 (High)	40/100
38	83546	Pierce	ID	Zone 1 (High)	41/100
39	83834	Harvard	ID	Zone 1 (High)	41/100
40	83340	Ketchum	ID	Zone 1 (High)	44/100
41	83861	Saint Maries	ID	Zone 1 (High)	45/100
42	83825	Dover	ID	Zone 1 (High)	46/100
43	83629	Horseshoe Bend	ID	Zone 1 (High)	50/100
44	83226	Challis	ID	Zone 1 (High)	51/100
45	83467	Salmon	ID	Zone 1 (High)	52/100
46	83544	Orofino	ID	Zone 1 (High)	52/100
47	83677	Yellow Pine	ID	Zone 1 (High)	52/100
48	83253	May	ID	Zone 1 (High)	53/100
49	83429	Island Park	ID	Zone 1 (High)	53/100
50	83445	Saint Anthony	ID	Zone 1 (High)	53/100
51	83462	Carmen	ID	Zone 1 (High)	53/100
52	83466	North Fork	ID	Zone 1 (High)	53/100
53	83469	Shoup	ID	Zone 1 (High)	53/100
54	83813	Cocolalla	ID	Zone 1 (High)	53/100
55	83822	Oldtown	ID	Zone 1 (High)	53/100
56	83841	Laclede	ID	Zone 1 (High)	53/100
57	83846	Mullan	ID	Zone 1 (High)	53/100
58	83849	Osburn	ID	Zone 1 (High)	53/100
59	83867	Silverton	ID	Zone 1 (High)	53/100
60	83716	Boise	ID	Zone 1 (High)	55/100
61	83333	Hailey	ID	Zone 1 (High)	56/100
62	83623	Glenns Ferry	ID	Zone 1 (High)	56/100
63	83857	Princeton	ID	Zone 1 (High)	56/100
64	83638	Mccall	ID	Zone 1 (High)	58/100
65	83836	Hope	ID	Zone 1 (High)	58/100
66	83536	Kamiah	ID	Zone 1 (High)	59/100
67	83874	Murray	ID	Zone 1 (High)	59/100
68	83876	Worley	ID	Zone 1 (High)	59/100
69	83314	Bliss	ID	Zone 1 (High)	60/100
70	83851	Plummer	ID	Zone 1 (High)	60/100
71	83327	Fairfield	ID	Zone 1 (High)	61/100
72	83332	Hagerman	ID	Zone 1 (High)	61/100
73	83611	Cascade	ID	Zone 1 (High)	61/100
74	83615	Donnelly	ID	Zone 1 (High)	61/100
75	83845	Moyie Springs	ID	Zone 1 (High)	61/100
76	83313	Bellevue	ID	Zone 1 (High)	62/100
77	83348	Picabo	ID	Zone 1 (High)	62/100
78	83520	Ahsahka	ID	Zone 1 (High)	62/100
79	83601	Atlanta	ID	Zone 1 (High)	62/100
80	83804	Blanchard	ID	Zone 1 (High)	62/100
81	83522	Cottonwood	ID	Zone 1 (High)	63/100
82	83554	White Bird	ID	Zone 1 (High)	63/100
83	83810	Cataldo	ID	Zone 1 (High)	63/100
84	83837	Kellogg	ID	Zone 1 (High)	63/100
85	83839	Kingston	ID	Zone 1 (High)	63/100
86	83255	Moore	ID	Zone 1 (High)	64/100
87	83320	Carey	ID	Zone 1 (High)	64/100
88	83353	Sun Valley	ID	Zone 1 (High)	64/100
89	83436	Newdale	ID	Zone 1 (High)	64/100
90	83526	Ferdinand	ID	Zone 1 (High)	64/100
91	83531	Fenn	ID	Zone 1 (High)	64/100
92	83622	Garden Valley	ID	Zone 1 (High)	64/100
93	83631	Idaho City	ID	Zone 1 (High)	64/100
94	83801	Athol	ID	Zone 1 (High)	64/100
95	83830	Fernwood	ID	Zone 1 (High)	64/100
96	83833	Harrison	ID	Zone 1 (High)	64/100
97	83843	Moscow	ID	Zone 1 (High)	64/100
98	83864	Sandpoint	ID	Zone 1 (High)	64/100
99	83869	Spirit Lake	ID	Zone 1 (High)	64/100
100	83213	Arco	ID	Zone 1 (High)	65/100

Methodology

Radon rankings are based on EPA county-level radon zone classifications. Zone 1 (highest risk) has predicted average indoor radon levels above 4 pCi/L — the EPA action level. Zone 2 is moderate (2-4 pCi/L) and Zone 3 is low (below 2 pCi/L). Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to prioritize areas with compounding risk factors.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-06-04.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest-risk classification, meaning the county has predicted average indoor radon levels above 4 pCi/L — the level at which the EPA recommends mitigation. Radon causes about 21,000 lung cancer deaths per year in the U.S.

Should I test for radon?

The EPA recommends testing all homes regardless of radon zone. A DIY test kit costs $15-40. Professional testing costs $150-250. If levels exceed 4 pCi/L, mitigation systems ($800-2,500) can reduce radon by up to 99%.