Nitrate Contamination

Nitrate in New Hampshire Drinking Water

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

Cities Tested

Has Violations

100%

% Has Violations

5.3 violations

State Avg

▼ 0% vs national

vs National

118

Health Violations

Analysis

Nitrate in New Hampshire: what the data shows

New Hampshire has 87 cities with nitrate-related violations. The EPA MCL for nitrate is 10 mg/L (measured as nitrogen). The state has 87 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

New Hampshire

100%

87 of 87 cities

← = Exactly at national rate

National avg

100%

8001 of 8001 cities

City Map

Nitrate data across New Hampshire

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 New Hampshire

Highest Nitrate levels (violations)

All Cities

All New Hampshire cities ranked by nitrate level

#	City	Level	Violations?	Violations	Grade
1	Gilford	39 violations	Yes	122	F
2	Ossipee	24 violations	Yes	27	F
3	Thornton	19 violations	Yes	69	F
4	Barrington	18 violations	Yes	117	F
5	Londonderry	15 violations	Yes	134	F
6	Belmont	13 violations	Yes	47	F
7	Campton	13 violations	Yes	76	F
8	Conway	12 violations	Yes	95	F
9	Moultonborough	12 violations	Yes	44	F
10	Bartlett	11 violations	Yes	193	D
11	Alton	8 violations	Yes	31	D
12	Sandown	8 violations	Yes	26	C+
13	Tilton	8 violations	Yes	15	B-
14	Salem	7 violations	Yes	37	D
15	Hinsdale	7 violations	Yes	6	B-
16	Northfield	7 violations	Yes	18	C-
17	Northwood	7 violations	Yes	23	C
18	Newmarket	6 violations	Yes	28	B
19	Meredith	6 violations	Yes	62	C-
20	Swanzey	6 violations	Yes	22	D+
21	Walpole	6 violations	Yes	6	D
22	Danville	6 violations	Yes	44	F
23	Tamworth	6 violations	Yes	64	F
24	Weare	6 violations	Yes	67	F
25	Rochester	5 violations	Yes	49	F
26	Derry	5 violations	Yes	63	F
27	Plymouth	5 violations	Yes	50	C
28	Wolfeboro	5 violations	Yes	28	C+
29	Haverhill	5 violations	Yes	18	D
30	Hillsborough	5 violations	Yes	104	D
31	New London	5 violations	Yes	29	C+
32	Plaistow	5 violations	Yes	95	F
33	Enfield	5 violations	Yes	50	F
34	Stratham	5 violations	Yes	168	F
35	Pittsfield	5 violations	Yes	10	C+
36	Loudon	5 violations	Yes	58	F
37	Laconia	4 violations	Yes	13	C+
38	Seabrook	4 violations	Yes	29	C+
39	Exeter	4 violations	Yes	60	F
40	Claremont	4 violations	Yes	6	A
41	Hooksett	4 violations	Yes	9	A-
42	Hampstead	4 violations	Yes	17	B-
43	Littleton	4 violations	Yes	16	A-
44	Newport	4 violations	Yes	4	B-
45	Northumberland	4 violations	Yes	4	C+
46	Sunapee	4 violations	Yes	24	C+
47	Pelham	4 violations	Yes	69	F
48	Madison	4 violations	Yes	11	D
49	Stow	4 violations	Yes	7	C-
50	Troy	4 violations	Yes	5	B-
51	Freedom	4 violations	Yes	24	F
52	Lebanon	3 violations	Yes	33	B-
53	Hanover	3 violations	Yes	31	A-
54	Pembroke	3 violations	Yes	18	B
55	Charlestown	3 violations	Yes	23	C-
56	Gorham	3 violations	Yes	3	B-
57	Windham	3 violations	Yes	53	F
58	Lancaster	3 violations	Yes	7	A-
59	Wakefield	3 violations	Yes	15	D+
60	Greenville	3 violations	Yes	14	D
61	Andover	3 violations	Yes	9	F
62	Unity	3 violations	Yes	3	A-
63	Durham	2 violations	Yes	26	B
64	Milford	2 violations	Yes	11	F
65	Franklin	2 violations	Yes	2	A-
66	Raymond	2 violations	Yes	52	F
67	Henniker	2 violations	Yes	13	B-
68	Barnstead	2 violations	Yes	9	A-
69	Ashland	2 violations	Yes	10	C+
70	Epsom	2 violations	Yes	27	D
71	Colebrook	2 violations	Yes	4	C+
72	Jackson	2 violations	Yes	21	C-
73	Amherst	2 violations	Yes	9	A-
74	Concord	1 violations	Yes	1	D+
75	Portsmouth	1 violations	Yes	12	B+
76	Hudson	1 violations	Yes	27	B
77	Rye	1 violations	Yes	5	A-
78	Winchester	1 violations	Yes	6	C-
79	Hopkinton	1 violations	Yes	54	F
80	Epping	1 violations	Yes	47	B
81	Wilton	1 violations	Yes	2	B
82	Bethlehem	1 violations	Yes	52	D+
83	Canaan	1 violations	Yes	50	F
84	Plainfield	1 violations	Yes	4	C+
85	Lisbon	1 violations	Yes	6	C
86	Chester	1 violations	Yes	7	A-
87	Newton	1 violations	Yes	12	B+

FAQ

Frequently asked questions about nitrate in New Hampshire

Is nitrate in New Hampshire tap water dangerous?

Yes — 87 cities in New Hampshire 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 New Hampshire 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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