Chromium-6 Contamination

Chromium-6 in Wisconsin Drinking Water

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

Cities Tested

Detected

100%

% Detected

0.63 µg/L

State Avg

▼ 0% vs national

vs National

388

Health Violations

Analysis

Chromium-6 in Wisconsin: what the data shows

Wisconsin has 75 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 75 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 0.63 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)

Wisconsin

100%

75 of 75 cities

← = Exactly at national rate

National avg

100%

4005 of 4005 cities

City Map

Chromium-6 data across Wisconsin

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 Wisconsin

Highest Chromium-6 levels (µg/L)

All Cities

All Wisconsin cities ranked by chromium-6 level

#	City	Level	Detected?	Violations	Grade
1	Madison	3.30 µg/L	Detected	14	F
2	Baraboo	3.11 µg/L	Detected	0	B
3	Rhinelander	2.56 µg/L	Detected	5	B
4	Beaver Dam	2.40 µg/L	Detected	11	A-
5	Waunakee	2.39 µg/L	Detected	11	B-
6	Beloit	2.08 µg/L	Detected	2	B+
7	Neenah	1.90 µg/L	Detected	6	C+
8	Middleton	1.89 µg/L	Detected	3	C+
9	La Crosse	1.60 µg/L	Detected	34	F
10	Manawa	1.45 µg/L	Detected	2	B
11	Lac Du Flambeau	1.40 µg/L	Detected	1	A
12	Onalaska	1.39 µg/L	Detected	2	A-
13	Plover	1.32 µg/L	Detected	9	B+
14	Arlington	1.20 µg/L	Detected	7	B
15	Shawano	1.10 µg/L	Detected	11	A
16	Stoughton	1.09 µg/L	Detected	4	B+
17	Marshfield	1.05 µg/L	Detected	9	C-
18	Sun Prairie	1.03 µg/L	Detected	4	A
19	Weston	0.96 µg/L	Detected	0	B+
20	Fort Atkinson	0.72 µg/L	Detected	14	A-
21	Janesville	0.68 µg/L	Detected	12	B
22	Hartford	0.64 µg/L	Detected	2	B+
23	Stevens Point	0.51 µg/L	Detected	14	C+
24	Grand Chute	0.47 µg/L	Detected	2	A
25	Kiel	0.47 µg/L	Detected	3	A-
26	Menasha	0.46 µg/L	Detected	1	B+
27	Fort Mccoy	0.45 µg/L	Detected	4	B+
28	Bowler	0.45 µg/L	Detected	8	A-
29	Rice Lake	0.44 µg/L	Detected	17	F
30	Hartland	0.44 µg/L	Detected	8	B
31	South Milwaukee	0.35 µg/L	Detected	0	A-
32	Eau Claire	0.34 µg/L	Detected	18	D+
33	Hudson	0.34 µg/L	Detected	4	B
34	Green Bay	0.27 µg/L	Detected	74	D+
35	West Bend	0.27 µg/L	Detected	11	F
36	Racine	0.26 µg/L	Detected	4	C+
37	Caledonia	0.26 µg/L	Detected	1	B
38	Milwaukee	0.25 µg/L	Detected	2	A
39	Kenosha	0.25 µg/L	Detected	11	D
40	Two Rivers	0.24 µg/L	Detected	5	C-
41	New Berlin	0.24 µg/L	Detected	14	B
42	Glendale	0.24 µg/L	Detected	1	A-
43	Franklin	0.24 µg/L	Detected	10	B
44	Oak Creek	0.23 µg/L	Detected	5	B
45	West Allis	0.22 µg/L	Detected	0	A-
46	Shorewood	0.22 µg/L	Detected	1	A-
47	Sheboygan	0.22 µg/L	Detected	1	A-
48	Manitowoc	0.22 µg/L	Detected	0	B+
49	Whitefish Bay	0.22 µg/L	Detected	0	B+
50	Port Washington	0.22 µg/L	Detected	6	B+
51	Wauwatosa	0.22 µg/L	Detected	1	B+
52	Menomonee Falls	0.21 µg/L	Detected	6	B+
53	De Pere	0.21 µg/L	Detected	38	B
54	Cudahy	0.21 µg/L	Detected	0	B+
55	Kaukauna	0.21 µg/L	Detected	9	B+
56	Greendale	0.21 µg/L	Detected	1	A-
57	Sheboygan Falls	0.21 µg/L	Detected	5	B-
58	Chippewa Falls	0.20 µg/L	Detected	12	D+
59	Marinette	0.19 µg/L	Detected	0	A-
60	Oconomowoc	0.19 µg/L	Detected	13	B
61	Brown Deer	0.18 µg/L	Detected	5	A
62	Monroe	0.16 µg/L	Detected	9	A-
63	Wausau	0.16 µg/L	Detected	24	C
64	Fitchburg	0.11 µg/L	Detected	0	A
65	Wisconsin Rapids	0.10 µg/L	Detected	6	B-
66	Portage	0.08 µg/L	Detected	9	B
67	Edgar	0.07 µg/L	Detected	1	B+
68	Fond Du Lac	0.07 µg/L	Detected	51	F
69	Grafton	0.06 µg/L	Detected	12	C+
70	Oshkosh	0.06 µg/L	Detected	0	A
71	Superior	0.05 µg/L	Detected	17	F
72	Algoma	0.04 µg/L	Detected	2	A-
73	Omro	0.04 µg/L	Detected	1	A-
74	Menomonie	0.03 µg/L	Detected	30	F
75	Little Chute	0.03 µg/L	Detected	1	B+

FAQ

Frequently asked questions about chromium-6 in Wisconsin

Is chromium-6 in Wisconsin 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. 75 cities in Wisconsin 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 Wisconsin 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 Wisconsin?

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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