Chromium-6 Contamination

Chromium-6 in Arizona 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

11.50 µg/L

State Avg

▼ 0% vs national

vs National

241

Health Violations

Analysis

Chromium-6 in Arizona: what the data shows

Arizona has 67 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 67 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 11.50 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)

Arizona

100%

67 of 67 cities

← = Exactly at national rate

National avg

100%

4005 of 4005 cities

City Map

Chromium-6 data across Arizona

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 Arizona

Highest Chromium-6 levels (µg/L)

All Cities

All Arizona cities ranked by chromium-6 level

#	City	Level	Detected?	Violations	Grade
1	Kingman	79.00 µg/L	Detected	110	D
2	Surprise	62.00 µg/L	Detected	18	F
3	Phoenix	54.00 µg/L	Detected	59	F
4	Casa Grande	37.00 µg/L	Detected	44	F
5	Scottsdale	36.00 µg/L	Detected	22	F
6	Peoria	36.00 µg/L	Detected	13	F
7	Buckeye-Sono	33.00 µg/L	Detected	2	B-
8	Paradise Valley	30.06 µg/L	Detected	3	C
9	Goodyear	27.00 µg/L	Detected	3	F
10	Glendale	26.00 µg/L	Detected	5	F
11	Vaya Chin, Hickiwan, San Simon Village/S	25.10 µg/L	Detected	1	A-
12	Mesa	24.00 µg/L	Detected	3	F
13	Buckeye	22.00 µg/L	Detected	103	F
14	Sun City	21.98 µg/L	Detected	1	B
15	Chandler	19.00 µg/L	Detected	32	F
16	Salt River Indian Community	18.00 µg/L	Detected	22	B
17	Gilbert	17.00 µg/L	Detected	11	F
18	Litchfield Park	16.00 µg/L	Detected	21	F
19	Prescott Valley	16.00 µg/L	Detected	6	D
20	El Mirage	15.00 µg/L	Detected	3	D
21	Avondale	14.00 µg/L	Detected	13	C+
22	Cottonwood	12.00 µg/L	Detected	184	D
23	Apache Junction	9.60 µg/L	Detected	18	F
24	Tempe	9.50 µg/L	Detected	3	D+
25	Tucson	9.40 µg/L	Detected	150	F
26	Fountain Hills	9.19 µg/L	Detected	21	F
27	Cave Creek	8.40 µg/L	Detected	25	C-
28	Johnson Ranch	8.30 µg/L	Detected	7	D
29	Prescott	8.20 µg/L	Detected	33	F
30	Sun City West	7.90 µg/L	Detected	3	B+
31	Maricopa	7.00 µg/L	Detected	228	D
32	Queen Creek	6.80 µg/L	Detected	14	D
33	Douglas	5.70 µg/L	Detected	55	D
34	Bullhead City	5.40 µg/L	Detected	57	F
35	Fort Defiance, Window Rock, St. Michaels	3.90 µg/L	Detected	22	B-
36	Sacaton, Sacaton Flats,Upper San Tan, Bl	3.40 µg/L	Detected	11	B
37	Nogales	2.30 µg/L	Detected	39	F
38	Flagstaff	2.20 µg/L	Detected	74	D
39	Green Valley	2.20 µg/L	Detected	9	D
40	Sedona	2.00 µg/L	Detected	174	F
41	Globe	1.90 µg/L	Detected	46	F
42	Lake Havasu City	1.50 µg/L	Detected	5	D
43	Grand Canyon	1.50 µg/L	Detected	11	D
44	Anthem	1.42 µg/L	Detected	1	B
45	Heber	1.30 µg/L	Detected	11	F
46	Red Rock	1.15 µg/L	Detected	1	D+
47	Sahuarita	1.10 µg/L	Detected	19	F
48	Oro Valley	1.00 µg/L	Detected	11	D
49	Florence	1.00 µg/L	Detected	60	F
50	Rio Rico	1.00 µg/L	Detected	4	C
51	Safford	0.83 µg/L	Detected	9	D
52	Yuma	0.72 µg/L	Detected	318	F
53	Sierra Vista	0.71 µg/L	Detected	44	D
54	Catalina	0.61 µg/L	Detected	2	D
55	Show Low	0.46 µg/L	Detected	60	D
56	Kaibeto	0.45 µg/L	Detected	0	B
57	Ganado, Cornfield, Steamboat, Woodspring	0.43 µg/L	Detected	4	B+
58	Fort Huachuca	0.41 µg/L	Detected	9	F
59	Benson	0.40 µg/L	Detected	29	D
60	Upper Fruitland, Nenahnezad, San Juan, N	0.32 µg/L	Detected	9	B+
61	Upper Fruitland, Nenahnezad, San Juan, N	0.32 µg/L	Detected	9	B+
62	Whiteriver	0.12 µg/L	Detected	7	D
63	Payson	0.07 µg/L	Detected	60	F
64	San Luis	0.06 µg/L	Detected	8	D
65	Mohave Valley	0.04 µg/L	Detected	14	F
66	Somerton	0.04 µg/L	Detected	17	D
67	Holbrook	0.04 µg/L	Detected	6	F

FAQ

Frequently asked questions about chromium-6 in Arizona

Is chromium-6 in Arizona 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. 67 cities in Arizona 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 Arizona 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 Arizona?

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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