Arsenic Contamination

Arsenic in Idaho Drinking Water

Ranked by arsenic violation count · Data from EPA SDWIS & UCMR

Cities Tested

Has Violations

100%

% Has Violations

13.1 violations

State Avg

▼ 0% vs national

vs National

134

Health Violations

Analysis

Arsenic in Idaho: what the data shows

Idaho has 79 cities with arsenic-related violations on record. Arsenic contamination is a federal MCL violation at levels above 10 µg/L (10 ppb). The state has 79 cities with at least one arsenic violation. Arsenic enters drinking water primarily through erosion of natural deposits, particularly in western states with arsenite-bearing geology. Industrial sources include mining runoff, glass manufacturing, and semiconductor production. Groundwater systems are significantly more likely to have arsenic issues than surface water systems. Long-term arsenic exposure above the MCL increases the risk of bladder, lung, and skin cancer, as well as cardiovascular disease and diabetes. Reverse osmosis and specialized arsenic-removal media are the most effective point-of-use treatment options.

Comparison

Cities exceeding 10 µg/L EPA MCL

Idaho

100%

79 of 79 cities

← = Exactly at national rate

National avg

100%

5489 of 5489 cities

City Map

Arsenic data across Idaho

Each dot is a city with arsenic violation data. Cities with at least one arsenic-related violation are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by arsenic level in Idaho

Highest Arsenic levels (violations)

All Cities

All Idaho cities ranked by arsenic level

#	City	Level	Violations?	Violations	Grade
1	Nampa	162 violations	Yes	255	F
2	Fruitland	109 violations	Yes	120	D
3	Buhl	79 violations	Yes	65	D
4	Caldwell	77 violations	Yes	226	F
5	Coeur D Alene	68 violations	Yes	125	F
6	Boise	51 violations	Yes	218	F
7	Twin Falls	41 violations	Yes	71	D+
8	Notus	40 violations	Yes	37	C
9	Filer	36 violations	Yes	34	B-
10	Pocatello	30 violations	Yes	117	F
11	Middleton	20 violations	Yes	64	D+
12	Emmett	17 violations	Yes	31	D
13	New Plymouth	17 violations	Yes	64	D+
14	Marsing	17 violations	Yes	29	D+
15	American Falls	16 violations	Yes	36	F
16	Mountain Home	13 violations	Yes	55	D
17	Spirit Lake	13 violations	Yes	26	D+
18	Dayton	13 violations	Yes	20	B
19	Rathdrum	12 violations	Yes	79	D
20	Sandpoint	12 violations	Yes	328	F
21	Sun Valley	11 violations	Yes	13	D
22	Kuna	10 violations	Yes	98	D
23	Athol	10 violations	Yes	67	D+
24	Bonners Ferry	9 violations	Yes	516	D
25	Hayden	8 violations	Yes	56	D
26	Idaho Falls	7 violations	Yes	101	D
27	Preston	7 violations	Yes	82	F
28	Ovid	6 violations	Yes	2	B+
29	Eagle	5 violations	Yes	52	F
30	Coeur D'Alene	5 violations	Yes	87	D
31	Plummer	5 violations	Yes	24	F
32	Kamiah	5 violations	Yes	127	D
33	Sagle	5 violations	Yes	39	D
34	Lapwai	5 violations	Yes	48	D+
35	Idaho City	5 violations	Yes	20	B-
36	Post Falls	4 violations	Yes	56	D
37	Lewiston	4 violations	Yes	91	F
38	Mountain Home Afb	4 violations	Yes	17	D
39	St Maries	4 violations	Yes	17	B-
40	Worley	4 violations	Yes	24	F
41	Garden Valley	4 violations	Yes	109	D
42	Challis	4 violations	Yes	8	B
43	Mccall	3 violations	Yes	19	F
44	Driggs	3 violations	Yes	12	D+
45	Salmon	3 violations	Yes	43	D
46	Fort Hall	3 violations	Yes	5	D
47	Troy	3 violations	Yes	19	C+
48	Mackay	3 violations	Yes	7	A
49	Blackfoot	2 violations	Yes	85	F
50	Burley	2 violations	Yes	29	F
51	Kellogg	2 violations	Yes	90	C+
52	St Anthony	2 violations	Yes	25	D
53	Moyie Springs	2 violations	Yes	18	B
54	Genesee	2 violations	Yes	8	A-
55	Horseshoe Bend	2 violations	Yes	77	C-
56	Fernwood	2 violations	Yes	103	B
57	Dubois	2 violations	Yes	3	A
58	Meridian	1 violations	Yes	34	F
59	Rexburg	1 violations	Yes	83	F
60	Moscow	1 violations	Yes	20	C-
61	Ammon	1 violations	Yes	52	D+
62	Payette	1 violations	Yes	8	B
63	Franklin	1 violations	Yes	13	C+
64	Weiser	1 violations	Yes	0	A-
65	Shelley	1 violations	Yes	44	D
66	Gooding	1 violations	Yes	13	B+
67	Dalton Gardens	1 violations	Yes	6	A
68	Victor	1 violations	Yes	6	B-
69	Pinehurst	1 violations	Yes	0	A-
70	Cottonwood	1 violations	Yes	26	B+
71	Kingston	1 violations	Yes	16	A-
72	Potlatch	1 violations	Yes	16	B
73	Grace	1 violations	Yes	14	B-
74	Donnelly	1 violations	Yes	6	B
75	Clark Fork	1 violations	Yes	3	A-
76	Roberts	1 violations	Yes	7	A-
77	Ririe	1 violations	Yes	8	A-
78	Coolin	1 violations	Yes	2	B+
79	Old Town	1 violations	Yes	0	B+

FAQ

Frequently asked questions about arsenic in Idaho

Is arsenic in Idaho tap water a concern?

Yes — 79 cities in Idaho have arsenic-related violations on record. The EPA MCL for arsenic is 10 µg/L. Even at levels below the MCL, long-term arsenic exposure has been linked to cancer and cardiovascular disease.

How can I remove arsenic from my drinking water in Idaho?

Reverse osmosis (RO) systems are the most effective at removing arsenic, typically reducing it by 90% or more. Specialized arsenic-removal media (such as iron-based adsorption filters) are also highly effective. Standard carbon filters and pitcher filters do NOT effectively remove arsenic. If your water comes from a private well, have it tested for arsenic.

Where does arsenic in Idaho water come from?

Arsenic enters drinking water primarily through natural erosion of arsenic-bearing rock formations. It is most common in groundwater systems in the western United States, parts of the Midwest, and New England. Industrial sources include mining, smelting, and agricultural pesticide residues. Groundwater sources are far more likely to contain arsenic than surface water.

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