Arsenic Contamination

Arsenic in Connecticut Drinking Water

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

100

Cities Tested

100

Has Violations

100%

% Has Violations

5.2 violations

State Avg

▼ 0% vs national

vs National

134

Health Violations

Analysis

Arsenic in Connecticut: what the data shows

Connecticut has 100 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 100 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

Connecticut

100%

100 of 100 cities

← = Exactly at national rate

National avg

100%

5489 of 5489 cities

City Map

Arsenic data across Connecticut

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 Connecticut

Highest Arsenic levels (violations)

All Cities

All Connecticut cities ranked by arsenic level

#	City	Level	Violations?	Violations	Grade
1	Lower Sipaulovi, Lower Mishongnovi	75 violations	Yes	63	D
2	Lower Sipaulovi, Lower Mishongnovi	75 violations	Yes	63	D
3	Putnam	56 violations	Yes	120	F
4	Bow	34 violations	Yes	53	D
5	Pomfret	26 violations	Yes	66	D
6	Putnam	13 violations	Yes	72	F
7	Brookfield	9 violations	Yes	85	F
8	East Haddam	8 violations	Yes	26	D
9	Brookfield	7 violations	Yes	56	D+
10	Berlin	6 violations	Yes	40	F
11	Franklin	6 violations	Yes	32	F
12	East Hampton	6 violations	Yes	64	D
13	Bethel	5 violations	Yes	59	F
14	Middlebury	5 violations	Yes	15	F
15	Colchester	5 violations	Yes	34	D
16	Old Lyme	5 violations	Yes	42	D
17	Hebron	5 violations	Yes	21	F
18	Ashford	5 violations	Yes	32	D
19	Ansonia	4 violations	Yes	12	F
20	Beacon Falls	4 violations	Yes	27	F
21	Beacon Falls	4 violations	Yes	2	F
22	East Granby	4 violations	Yes	85	F
23	East Granby	4 violations	Yes	9	D
24	East Granby	4 violations	Yes	25	F
25	Bethel	4 violations	Yes	135	F
26	Bristol	4 violations	Yes	18	C
27	Bristol	4 violations	Yes	9	C
28	Harwinton	4 violations	Yes	19	F
29	Beacon Falls	3 violations	Yes	7	F
30	Beacon Falls	3 violations	Yes	2	F
31	Beacon Falls	3 violations	Yes	2	F
32	Berlin	3 violations	Yes	4	C
33	East Granby	3 violations	Yes	12	C-
34	Bristol	3 violations	Yes	4	C+
35	Groton	3 violations	Yes	23	D+
36	Harwinton	3 violations	Yes	5	D
37	Clinton	3 violations	Yes	4	D+
38	Chester	3 violations	Yes	5	C
39	Kent	3 violations	Yes	30	D
40	Ansonia	2 violations	Yes	2	D
41	Beacon Falls	2 violations	Yes	4	F
42	Berlin	2 violations	Yes	5	C
43	Berlin	2 violations	Yes	8	C
44	Beacon Falls	2 violations	Yes	7	F
45	Beacon Falls	2 violations	Yes	5	F
46	Berlin	2 violations	Yes	0	B-
47	Beacon Falls	2 violations	Yes	7	D
48	Beacon Falls	2 violations	Yes	7	D
49	Beacon Falls	2 violations	Yes	7	D
50	Beacon Falls	2 violations	Yes	2	C-
51	Beacon Falls	2 violations	Yes	3	C-
52	Beacon Falls	2 violations	Yes	46	F
53	Beacon Falls	2 violations	Yes	2	C-
54	Beacon Falls	2 violations	Yes	2	C-
55	Beacon Falls	2 violations	Yes	2	C-
56	Beacon Falls	2 violations	Yes	2	C-
57	Beacon Falls	2 violations	Yes	2	C-
58	East Granby	2 violations	Yes	5	C-
59	East Granby	2 violations	Yes	24	F
60	East Granby	2 violations	Yes	1	C+
61	East Granby	2 violations	Yes	0	B
62	Groton	2 violations	Yes	17	F
63	Harwinton	2 violations	Yes	8	F
64	Franklin	2 violations	Yes	27	F
65	Cromwell	2 violations	Yes	25	F
66	Clinton	2 violations	Yes	20	D
67	East Windsor	2 violations	Yes	6	C+
68	Groton	2 violations	Yes	6	B-
69	Griswold	2 violations	Yes	53	F
70	Chester	2 violations	Yes	10	D
71	Chester	2 violations	Yes	12	B-
72	Plainfield	2 violations	Yes	37	D
73	Woodbury	2 violations	Yes	18	D+
74	Willington	2 violations	Yes	41	F
75	Ansonia	1 violations	Yes	18	F
76	Berlin	1 violations	Yes	6	F
77	Ansonia	1 violations	Yes	28	F
78	Berlin	1 violations	Yes	3	D+
79	Berlin	1 violations	Yes	1	B-
80	Berlin	1 violations	Yes	9	C
81	Bethel	1 violations	Yes	25	F
82	Franklin	1 violations	Yes	143	F
83	New London	1 violations	Yes	16	C-
84	New London	1 violations	Yes	0	C+
85	Harwinton	1 violations	Yes	3	B+
86	Franklin	1 violations	Yes	19	B-
87	Clinton	1 violations	Yes	18	C+
88	Clinton	1 violations	Yes	7	C+
89	Clinton	1 violations	Yes	0	B-
90	East Granby	1 violations	Yes	9	F
91	East Granby	1 violations	Yes	3	C+
92	Killingly	1 violations	Yes	32	F
93	Killingly	1 violations	Yes	14	C-
94	Barkhamsted	1 violations	Yes	12	C
95	Putnam	1 violations	Yes	19	D
96	Avon	1 violations	Yes	8	C
97	Coventry	1 violations	Yes	34	F
98	Washington	1 violations	Yes	31	F
99	Sprague	1 violations	Yes	0	B+
100	Hopkinton	1 violations	Yes	37	F

FAQ

Frequently asked questions about arsenic in Connecticut

Is arsenic in Connecticut tap water a concern?

Yes — 100 cities in Connecticut 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 Connecticut?

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 Connecticut 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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