Chromium-6 Contamination

Chromium-6 in Washington 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

0.80 µg/L

State Avg

▼ 0% vs national

vs National

261

Health Violations

Analysis

Chromium-6 in Washington: what the data shows

Washington has 91 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 91 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 0.80 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)

Washington

100%

91 of 91 cities

← = Exactly at national rate

National avg

100%

4005 of 4005 cities

City Map

Chromium-6 data across Washington

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 Washington

Highest Chromium-6 levels (µg/L)

All Cities

All Washington cities ranked by chromium-6 level

#	City	Level	Detected?	Violations	Grade
1	Silverdale	9.90 µg/L	Detected	17	F
2	Manchester	5.40 µg/L	Detected	7	A
3	Poulsbo	4.00 µg/L	Detected	95	F
4	Sequim	3.42 µg/L	Detected	64	F
5	Arlington	3.04 µg/L	Detected	83	F
6	Yakima	2.92 µg/L	Detected	162	F
7	Vancouver	2.70 µg/L	Detected	36	F
8	Port Orchard	2.60 µg/L	Detected	753	F
9	Marysville	2.50 µg/L	Detected	12	D
10	Bremerton	1.87 µg/L	Detected	13	C
11	Sunnyside	1.64 µg/L	Detected	2	A-
12	Shelton	1.60 µg/L	Detected	158	F
13	Camas	1.60 µg/L	Detected	2	C
14	West Richland	1.46 µg/L	Detected	99	F
15	Snohomish	1.29 µg/L	Detected	11	D
16	Castle Rock	1.27 µg/L	Detected	2	A-
17	Joint Base Lewis-Mcchord	1.24 µg/L	Detected	3	B+
18	Edmonds	1.20 µg/L	Detected	0	A-
19	Cashmere	1.09 µg/L	Detected	21	F
20	Yacolt	1.00 µg/L	Detected	0	A
21	Ellensburg	0.94 µg/L	Detected	19	D
22	Dupont	0.82 µg/L	Detected	0	A
23	Birch Bay	0.72 µg/L	Detected	14	A
24	Selah	0.71 µg/L	Detected	4	B
25	Wenatchee	0.66 µg/L	Detected	41	D
26	Mead	0.64 µg/L	Detected	3	B-
27	Kennewick	0.62 µg/L	Detected	78	F
28	Sammamish	0.58 µg/L	Detected	6	C-
29	Tumwater	0.57 µg/L	Detected	24	D+
30	Royal City	0.57 µg/L	Detected	1	A-
31	Lacey	0.54 µg/L	Detected	125	F
32	Lakewood	0.54 µg/L	Detected	5	B+
33	Spokane	0.53 µg/L	Detected	56	F
34	Tacoma	0.49 µg/L	Detected	232	F
35	Auburn	0.46 µg/L	Detected	18	D+
36	Kent	0.42 µg/L	Detected	31	F
37	Buckley	0.41 µg/L	Detected	5	D+
38	Puyallup	0.40 µg/L	Detected	124	F
39	Lynnwood	0.40 µg/L	Detected	0	B-
40	Port Angeles	0.39 µg/L	Detected	19	F
41	Monroe	0.38 µg/L	Detected	4	C
42	Othello	0.37 µg/L	Detected	102	D
43	Bothell	0.36 µg/L	Detected	7	F
44	Richland	0.35 µg/L	Detected	7	C+
45	Spanaway	0.35 µg/L	Detected	9	C+
46	Mukilteo	0.35 µg/L	Detected	0	A-
47	Spokane Valley	0.34 µg/L	Detected	10	C-
48	Everett	0.34 µg/L	Detected	16	D
49	Federal Way	0.32 µg/L	Detected	2	B
50	Hoquiam	0.31 µg/L	Detected	6	B-
51	Mountlake Terrace	0.31 µg/L	Detected	0	B+
52	Olympia	0.30 µg/L	Detected	66	F
53	Chehalis	0.27 µg/L	Detected	12	F
54	Aberdeen	0.26 µg/L	Detected	10	D
55	South Bend	0.26 µg/L	Detected	83	D+
56	Renton	0.23 µg/L	Detected	11	D+
57	Enumclaw	0.23 µg/L	Detected	1	B+
58	Greenacres	0.21 µg/L	Detected	12	B+
59	Seattle	0.20 µg/L	Detected	138	F
60	Burien	0.20 µg/L	Detected	1	B+
61	Bellevue	0.18 µg/L	Detected	2	A
62	Carbonado	0.18 µg/L	Detected	41	B
63	Bucoda	0.18 µg/L	Detected	5	B+
64	Mount Vernon	0.17 µg/L	Detected	191	F
65	Moses Lake	0.17 µg/L	Detected	132	F
66	Mercer Island	0.17 µg/L	Detected	1	A-
67	Issaquah	0.16 µg/L	Detected	10	C-
68	Redmond	0.16 µg/L	Detected	4	B-
69	Maple Valley	0.16 µg/L	Detected	7	C+
70	Snoqualime	0.16 µg/L	Detected	4	A-
71	Lynden	0.15 µg/L	Detected	235	F
72	Kirkland	0.14 µg/L	Detected	4	D+
73	Longview	0.14 µg/L	Detected	0	B+
74	Shoreline	0.14 µg/L	Detected	0	A-
75	Kelso	0.14 µg/L	Detected	15	F
76	Oak Harbor	0.13 µg/L	Detected	105	F
77	Battle Ground	0.13 µg/L	Detected	12	B-
78	Ferndale	0.13 µg/L	Detected	110	F
79	Yelm	0.13 µg/L	Detected	12	D+
80	Nas Whidbey Island	0.13 µg/L	Detected	0	A+
81	Woodinville	0.11 µg/L	Detected	1	A-
82	Centralia	0.09 µg/L	Detected	5	B-
83	Pasco	0.09 µg/L	Detected	137	D
84	Kenmore	0.09 µg/L	Detected	0	B-
85	Bellingham	0.08 µg/L	Detected	54	F
86	Washougal	0.07 µg/L	Detected	2	B+
87	East Wenatchee	0.07 µg/L	Detected	19	B
88	Stanwood	0.07 µg/L	Detected	31	D
89	Walla Walla	0.06 µg/L	Detected	84	D
90	Bainbridge Island	0.04 µg/L	Detected	3	A
91	Clarkston	0.04 µg/L	Detected	16	B+

FAQ

Frequently asked questions about chromium-6 in Washington

Is chromium-6 in Washington 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. 91 cities in Washington 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 Washington 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 Washington?

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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