Chromium-6 Contamination

Chromium-6 in Connecticut Drinking Water

Ranked by max chromium-6 detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR

113

Cities Tested

113

Detected

100%

% Detected

0.40 µg/L

State Avg

▼ 0% vs national

vs National

134

Health Violations

Analysis

Chromium-6 in Connecticut: what the data shows

Connecticut has 113 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 113 of those cities. There is currently no federal MCL for chromium-6 — California's 10 µg/L limit is used as a reference. The state average max detected level is 0.40 µg/L. Chromium-6 occurs naturally in some groundwater aquifers but also from industrial discharge, particularly from steel processing, chrome plating, and leather tanning. It is distinct from trivalent chromium (Cr III), which is an essential nutrient at low doses. The National Toxicology Program and IARC classify chromium-6 as a carcinogen via inhalation; the evidence for drinking water carcinogenicity is strong but regulatory action at the federal level remains pending as of 2026. Reverse osmosis systems effectively remove chromium-6 to near-undetectable levels.

Comparison

Cities exceeding No federal MCL (CA: 10 µg/L)

Connecticut

100%

113 of 113 cities

← = Exactly at national rate

National avg

100%

4005 of 4005 cities

City Map

Chromium-6 data across Connecticut

Each dot is a city with UCMR 3 chromium-6 data. Detected cities are shown; there is no federal MCL — California's 10 µg/L limit is used as a reference. Size reflects population served.

Worst Offenders

Top 10 cities by chromium-6 level in Connecticut

Highest Chromium-6 levels (µg/L)

All Cities

All Connecticut cities ranked by chromium-6 level

#	City	Level	Detected?	Violations	Grade
1	East Granby	1.20 µg/L	Detected	9	D
2	East Granby	1.20 µg/L	Detected	25	F
3	East Windsor	1.20 µg/L	Detected	6	C+
4	Ansonia	1.10 µg/L	Detected	12	F
5	Ansonia	1.10 µg/L	Detected	18	F
6	Ansonia	1.10 µg/L	Detected	28	F
7	Berlin	1.00 µg/L	Detected	3	D+
8	Plainville	1.00 µg/L	Detected	3	C+
9	East Granby	1.00 µg/L	Detected	9	F
10	Ansonia	0.86 µg/L	Detected	2	D
11	Ansonia	0.86 µg/L	Detected	1	C+
12	Ansonia	0.86 µg/L	Detected	4	D
13	Ansonia	0.86 µg/L	Detected	4	C+
14	Ansonia	0.86 µg/L	Detected	0	C-
15	Ansonia	0.86 µg/L	Detected	4	D+
16	Ansonia	0.86 µg/L	Detected	0	B+
17	Ansonia	0.86 µg/L	Detected	0	B+
18	Ansonia	0.86 µg/L	Detected	0	B+
19	Ansonia	0.86 µg/L	Detected	0	B+
20	Ansonia	0.86 µg/L	Detected	25	F
21	Ansonia	0.86 µg/L	Detected	0	B+
22	Ansonia	0.86 µg/L	Detected	0	B+
23	Ansonia	0.86 µg/L	Detected	0	B+
24	Ansonia	0.86 µg/L	Detected	0	B+
25	Ansonia	0.86 µg/L	Detected	0	B+
26	Ansonia	0.86 µg/L	Detected	0	B+
27	Berlin	0.81 µg/L	Detected	5	C
28	Berlin	0.81 µg/L	Detected	8	C
29	Berlin	0.81 µg/L	Detected	4	B+
30	East Granby	0.81 µg/L	Detected	5	C-
31	Berlin	0.69 µg/L	Detected	40	F
32	Berlin	0.69 µg/L	Detected	0	B-
33	East Granby	0.69 µg/L	Detected	85	F
34	East Granby	0.69 µg/L	Detected	24	F
35	East Granby	0.69 µg/L	Detected	12	C-
36	East Granby	0.69 µg/L	Detected	1	C+
37	East Granby	0.69 µg/L	Detected	0	B
38	Berlin	0.68 µg/L	Detected	4	C
39	Bristol	0.68 µg/L	Detected	4	C+
40	East Granby	0.58 µg/L	Detected	3	C+
41	Berlin	0.49 µg/L	Detected	6	F
42	Berlin	0.49 µg/L	Detected	1	B-
43	Beacon Falls	0.26 µg/L	Detected	27	F
44	Bethel	0.26 µg/L	Detected	135	F
45	Bethel	0.26 µg/L	Detected	59	F
46	Bethel	0.26 µg/L	Detected	25	F
47	Hampton	0.26 µg/L	Detected	12	B-
48	Hampton	0.26 µg/L	Detected	1	B
49	East Lyme	0.26 µg/L	Detected	6	C
50	Beacon Falls	0.22 µg/L	Detected	4	F
51	Beacon Falls	0.22 µg/L	Detected	5	F
52	Middlebury	0.20 µg/L	Detected	11	D+
53	Harwinton	0.20 µg/L	Detected	8	F
54	Harwinton	0.20 µg/L	Detected	19	F
55	Harwinton	0.20 µg/L	Detected	3	B+
56	Harwinton	0.20 µg/L	Detected	5	D
57	Bristol	0.19 µg/L	Detected	18	C
58	Bristol	0.19 µg/L	Detected	9	C
59	Mashantucket	0.17 µg/L	Detected	7	B
60	Beacon Falls	0.16 µg/L	Detected	7	F
61	Beacon Falls	0.16 µg/L	Detected	3	C-
62	Middlebury	0.16 µg/L	Detected	14	C
63	Beacon Falls	0.16 µg/L	Detected	1	A
64	Beacon Falls	0.14 µg/L	Detected	7	D
65	Beacon Falls	0.14 µg/L	Detected	7	D
66	Beacon Falls	0.14 µg/L	Detected	7	D
67	Beacon Falls	0.14 µg/L	Detected	2	C-
68	Beacon Falls	0.14 µg/L	Detected	46	F
69	Beacon Falls	0.14 µg/L	Detected	7	F
70	Beacon Falls	0.14 µg/L	Detected	2	F
71	Beacon Falls	0.14 µg/L	Detected	2	F
72	Beacon Falls	0.14 µg/L	Detected	2	F
73	Beacon Falls	0.14 µg/L	Detected	2	C-
74	Beacon Falls	0.14 µg/L	Detected	2	C-
75	Beacon Falls	0.14 µg/L	Detected	2	C-
76	Beacon Falls	0.14 µg/L	Detected	2	C-
77	Beacon Falls	0.14 µg/L	Detected	2	C-
78	Cromwell	0.12 µg/L	Detected	11	D
79	Cromwell	0.12 µg/L	Detected	25	F
80	Ansonia	0.12 µg/L	Detected	6	B-
81	Clinton	0.11 µg/L	Detected	18	C+
82	Clinton	0.11 µg/L	Detected	20	D
83	Clinton	0.11 µg/L	Detected	4	D+
84	Clinton	0.11 µg/L	Detected	7	C+
85	Clinton	0.11 µg/L	Detected	0	B-
86	Groton	0.10 µg/L	Detected	23	D+
87	Groton	0.10 µg/L	Detected	17	F
88	Uncasville	0.10 µg/L	Detected	1	A
89	Groton	0.10 µg/L	Detected	6	B-
90	Chester	0.10 µg/L	Detected	10	D
91	Chester	0.10 µg/L	Detected	12	B-
92	Chester	0.10 µg/L	Detected	5	C
93	Franklin	0.09 µg/L	Detected	143	F
94	New London	0.09 µg/L	Detected	16	C-
95	New London	0.09 µg/L	Detected	0	C+
96	Middlebury	0.08 µg/L	Detected	18	C-
97	Franklin	0.07 µg/L	Detected	27	F
98	Franklin	0.07 µg/L	Detected	32	F
99	Franklin	0.07 µg/L	Detected	19	B-
100	Franklin	0.07 µg/L	Detected	23	D+
101	Franklin	0.07 µg/L	Detected	13	B
102	Franklin	0.07 µg/L	Detected	13	B
103	Windham	0.07 µg/L	Detected	11	B+
104	Berlin	0.06 µg/L	Detected	1	D
105	Berlin	0.06 µg/L	Detected	0	B+
106	Berlin	0.06 µg/L	Detected	9	C
107	Berlin	0.06 µg/L	Detected	33	F
108	Berlin	0.06 µg/L	Detected	1	B
109	Berlin	0.06 µg/L	Detected	0	A-
110	Berlin	0.06 µg/L	Detected	0	A-
111	Berlin	0.06 µg/L	Detected	0	A-
112	Berlin	0.06 µg/L	Detected	0	A-
113	Berlin	0.06 µg/L	Detected	0	B-

FAQ

Frequently asked questions about chromium-6 in Connecticut

Is chromium-6 in Connecticut tap water dangerous?

Chromium-6 (hexavalent chromium) is a potential human carcinogen. There is currently no federal MCL — California's 10 µg/L limit is the most protective US standard. 113 cities in Connecticut had detectable chromium-6 in UCMR 3 testing (2013–2015). Reverse osmosis is the most effective removal method.

Where does chromium-6 come from in Connecticut water?

Chromium-6 enters water supplies from two main sources: natural weathering of chromium-containing rock formations (especially in the Southwest and parts of the Midwest) and industrial discharge from steel mills, chrome plating, and coal ash sites. Groundwater systems are more commonly affected by natural sources, while surface water systems near industrial areas face pollution-related risks.

How can I filter chromium-6 from my water in Connecticut?

Reverse osmosis (RO) systems are the most effective, removing over 95% of chromium-6. Some high-quality activated alumina or anion exchange filters also provide significant reduction. Standard carbon filters and pitcher filters are generally NOT effective against chromium-6. Look for filters certified by NSF International against NSF/ANSI 58 (for RO systems).

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