Nitrate Contamination

Nitrate in Montana Drinking Water

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

103

Cities Tested

103

Has Violations

100%

% Has Violations

12.6 violations

State Avg

▼ 0% vs national

vs National

Health Violations

Analysis

Nitrate in Montana: what the data shows

Montana has 103 cities with nitrate-related violations. The EPA MCL for nitrate is 10 mg/L (measured as nitrogen). The state has 103 cities with at least one nitrate violation. Nitrate is the most common groundwater contaminant in the United States. It enters water supplies primarily through agricultural fertilizer runoff, septic system leaching, and animal feedlot operations. Rural and agricultural communities face the highest risk. The primary acute health concern is methemoglobinemia ("blue baby syndrome") in infants under six months. Emerging research also links chronic nitrate exposure to thyroid disease, certain cancers, and adverse birth outcomes. Reverse osmosis, ion exchange, and distillation can remove nitrate from drinking water — standard carbon filters do not.

Comparison

Cities exceeding 10 mg/L EPA MCL

Montana

100%

103 of 103 cities

← = Exactly at national rate

National avg

100%

8001 of 8001 cities

City Map

Nitrate data across Montana

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

Worst Offenders

Top 10 cities by nitrate level in Montana

Highest Nitrate levels (violations)

All Cities

All Montana cities ranked by nitrate level

#	City	Level	Violations?	Violations	Grade
1	Billings	107 violations	Yes	51	F
2	Missoula	101 violations	Yes	189	F
3	Kalispell	101 violations	Yes	162	F
4	Bozeman	86 violations	Yes	57	F
5	Lewistown	74 violations	Yes	99	D
6	Helena	67 violations	Yes	90	F
7	Livingston	39 violations	Yes	40	D
8	Great Falls	32 violations	Yes	64	F
9	Columbia Falls	28 violations	Yes	23	D
10	Lolo	27 violations	Yes	14	D+
11	Hamilton	26 violations	Yes	20	D+
12	Frenchtown	23 violations	Yes	28	C+
13	Polson	20 violations	Yes	26	D+
14	East Helena	20 violations	Yes	9	D+
15	Dillon	19 violations	Yes	36	F
16	Libby	18 violations	Yes	50	F
17	Harlem	18 violations	Yes	237	D
18	Crow Agency	18 violations	Yes	43	D
19	Belgrade	17 violations	Yes	27	F
20	Manhattan	17 violations	Yes	8	D+
21	Whitefish	16 violations	Yes	42	F
22	Valier	16 violations	Yes	21	B
23	Glendive	15 violations	Yes	16	D
24	Malta	14 violations	Yes	0	D
25	Havre	12 violations	Yes	151	F
26	Cut Bank	12 violations	Yes	29	D
27	Pinesdale	11 violations	Yes	17	B
28	Stanford	11 violations	Yes	3	C-
29	Anaconda	10 violations	Yes	12	D+
30	Big Sky	10 violations	Yes	17	F
31	Clancy	10 violations	Yes	68	F
32	Ballantine	10 violations	Yes	8	C+
33	Ballantine	10 violations	Yes	8	C+
34	Corwin Springs	10 violations	Yes	18	C+
35	Ashland	9 violations	Yes	49	D+
36	West Yellowstone	8 violations	Yes	10	D
37	Sidney	8 violations	Yes	27	F
38	Deer Lodge	8 violations	Yes	7	D
39	Harlowton	8 violations	Yes	9	C+
40	Sand Coulee	8 violations	Yes	10	C-
41	Lame Deer	7 violations	Yes	54	F
42	Thompson Falls	7 violations	Yes	27	B+
43	Townsend	7 violations	Yes	3	B
44	Fairfield	7 violations	Yes	0	B-
45	Absarokee	7 violations	Yes	4	B+
46	White Sulphur Springs	7 violations	Yes	44	D+
47	Hot Springs	7 violations	Yes	1	A-
48	Conrad	6 violations	Yes	29	D
49	Troy	6 violations	Yes	6	B+
50	Stevensville	6 violations	Yes	13	B-
51	Chester	6 violations	Yes	26	D
52	Darby	6 violations	Yes	26	C
53	Huntley	6 violations	Yes	2	B+
54	Joliet	6 violations	Yes	0	A-
55	Hardin	5 violations	Yes	6	F
56	Eureka	5 violations	Yes	16	C-
57	Columbus	5 violations	Yes	8	D
58	St Ignatius	5 violations	Yes	10	B
59	Pablo	4 violations	Yes	116	F
60	Ronan	4 violations	Yes	14	C-
61	Red Lodge	4 violations	Yes	4	B
62	Lakeside	4 violations	Yes	20	B+
63	Choteau	4 violations	Yes	5	B-
64	Ennis	4 violations	Yes	3	B+
65	Fort Benton	4 violations	Yes	1	B+
66	Sun River	4 violations	Yes	2	A-
67	Browning	3 violations	Yes	40	F
68	Laurel	3 violations	Yes	6	C+
69	Box Elder	3 violations	Yes	21	B-
70	Colstrip	3 violations	Yes	2	A-
71	Baker	3 violations	Yes	1	D+
72	Plains	3 violations	Yes	0	B+
73	Whitehall	3 violations	Yes	64	D+
74	Philipsburg	3 violations	Yes	19	F
75	Somers	3 violations	Yes	4	A-
76	Sheridan	3 violations	Yes	0	C-
77	Big Sandy	3 violations	Yes	2	A
78	Wibaux	3 violations	Yes	9	D+
79	Fromberg	3 violations	Yes	5	C
80	Butte	2 violations	Yes	4	B+
81	Shelby	2 violations	Yes	50	D
82	Glasgow	2 violations	Yes	5	C+
83	Forsyth	2 violations	Yes	5	A-
84	Three Forks	2 violations	Yes	2	A
85	Big Timber	2 violations	Yes	6	B+
86	Virginia City	2 violations	Yes	11	C+
87	Scobey	2 violations	Yes	0	A-
88	Fairview	2 violations	Yes	4	B+
89	Fort Peck	2 violations	Yes	9	B-
90	Bridger	2 violations	Yes	0	A-
91	Cascade	2 violations	Yes	0	A
92	Medicine Lake	2 violations	Yes	9	B
93	Miles City	1 violations	Yes	15	C+
94	Culbertson	1 violations	Yes	6	B+
95	Roundup	1 violations	Yes	0	C+
96	Black Eagle	1 violations	Yes	11	B
97	Chinook	1 violations	Yes	15	B
98	Superior	1 violations	Yes	0	A
99	Sunburst	1 violations	Yes	5	B
100	Belt	1 violations	Yes	10	B+
101	Warm Springs	1 violations	Yes	0	B
102	Vaughn	1 violations	Yes	0	B+
103	Santa Rita	1 violations	Yes	0	A-

FAQ

Frequently asked questions about nitrate in Montana

Is nitrate in Montana tap water dangerous?

Yes — 103 cities in Montana have nitrate-related violations. The EPA MCL is 10 mg/L. Nitrate is especially dangerous for infants under six months, where it can cause methemoglobinemia ("blue baby syndrome"). Adults face lower acute risk, but chronic exposure is linked to thyroid disease and certain cancers.

How can I remove nitrate from my drinking water?

Reverse osmosis, ion exchange, and distillation are effective at removing nitrate. Standard carbon filters (including most pitcher and faucet-mount filters) do NOT remove nitrate. If you rely on a private well in an agricultural area, have your water tested annually for nitrate.

What causes high nitrate levels in Montana water?

Nitrate contamination comes primarily from agricultural fertilizer runoff, septic system leaching, and animal feedlot operations. Rural communities near intensive farming are most at risk. Shallow wells are particularly vulnerable. Heavy rainfall can spike nitrate levels as it washes fertilizer into groundwater and surface water supplies.

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