Chromium-6 Contamination

Chromium-6 in California Drinking Water

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

330

Cities Tested

330

Detected

100%

% Detected

3.85 µg/L

State Avg

▼ 0% vs national

vs National

624

Health Violations

Analysis

Chromium-6 in California: what the data shows

California has 330 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 330 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 3.85 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)

California

100%

330 of 330 cities

← = Exactly at national rate

National avg

100%

4005 of 4005 cities

City Map

Chromium-6 data across California

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 California

Highest Chromium-6 levels (µg/L)

All Cities

All California cities ranked by chromium-6 level

#	City	Level	Detected?	Violations	Grade
1	Davis	47.00 µg/L	Detected	47	B+
2	Los Banos	42.00 µg/L	Detected	29	B
3	Soquel	35.00 µg/L	Detected	1	A
4	Kerman	31.00 µg/L	Detected	13	B
5	Woodland	26.00 µg/L	Detected	52	F
6	Patterson	26.00 µg/L	Detected	35	B+
7	Twentynine Palms	24.00 µg/L	Detected	70	B+
8	Palm Desert	20.00 µg/L	Detected	12	C+
9	Vacaville	20.00 µg/L	Detected	26	F
10	Coachella	20.00 µg/L	Detected	11	C-
11	Newman	20.00 µg/L	Detected	3	A-
12	Indio	19.00 µg/L	Detected	12	F
13	Banning	19.00 µg/L	Detected	15	B-
14	Hesperia	18.00 µg/L	Detected	2	B
15	Tracy	18.00 µg/L	Detected	45	C
16	Watsonville	18.00 µg/L	Detected	74	F
17	Hollister	18.00 µg/L	Detected	132	F
18	Desert Hot Springs	17.00 µg/L	Detected	4	A
19	Phelan	17.00 µg/L	Detected	0	B+
20	Alhambra	16.00 µg/L	Detected	7	A-
21	Rosamond	16.00 µg/L	Detected	205	F
22	Rio Linda	15.00 µg/L	Detected	2	A-
23	Bermuda Dunes	15.00 µg/L	Detected	0	A+
24	Sacramento	14.81 µg/L	Detected	425	F
25	Beaumont	14.00 µg/L	Detected	2	A-
26	Delano	14.00 µg/L	Detected	67	B
27	Fresno	13.00 µg/L	Detected	523	F
28	Daly City	13.00 µg/L	Detected	4	A
29	San Luis Obispo	13.00 µg/L	Detected	27	F
30	Brentwood	13.00 µg/L	Detected	91	F
31	Arcadia	13.00 µg/L	Detected	2	B
32	29 Palms	13.00 µg/L	Detected	3	B
33	Rosemead	11.30 µg/L	Detected	17	C-
34	Covina	11.00 µg/L	Detected	10	B
35	Quartz Hill	11.00 µg/L	Detected	1	A-
36	Mcfarland	11.00 µg/L	Detected	42	C+
37	Los Osos	10.55 µg/L	Detected	0	B+
38	California City	10.00 µg/L	Detected	22	A-
39	Ripon	9.50 µg/L	Detected	10	A-
40	Victorville	9.40 µg/L	Detected	1	B+
41	Wasco	9.20 µg/L	Detected	26	B+
42	Anaheim	9.00 µg/L	Detected	8	C+
43	San Dimas	8.60 µg/L	Detected	6	B-
44	Turlock	8.50 µg/L	Detected	16	B-
45	Pleasanton	8.40 µg/L	Detected	3	B-
46	Lodi	8.30 µg/L	Detected	16	C+
47	Burbank	8.10 µg/L	Detected	1	A-
48	Palmdale	7.70 µg/L	Detected	15	C+
49	Ontario	7.60 µg/L	Detected	1	B+
50	San Jose	7.30 µg/L	Detected	142	F
51	Montclair	7.20 µg/L	Detected	0	B+
52	Modesto	7.00 µg/L	Detected	76	D
53	Pasadena	7.00 µg/L	Detected	92	F
54	Redlands	7.00 µg/L	Detected	2	B
55	Atwater	6.70 µg/L	Detected	3	B+
56	Stockton	6.60 µg/L	Detected	261	F
57	Chino Hills	6.60 µg/L	Detected	2	A
58	Yucaipa	6.60 µg/L	Detected	9	C+
59	Morgan Hill	6.40 µg/L	Detected	92	F
60	Chino	6.20 µg/L	Detected	9	B
61	Red Bluff	6.20 µg/L	Detected	23	F
62	Elk Grove	5.90 µg/L	Detected	28	C
63	Fort Irwin	5.90 µg/L	Detected	60	B+
64	Salinas	5.80 µg/L	Detected	639	F
65	Edwards Afb	5.80 µg/L	Detected	8	A-
66	Soledad	5.70 µg/L	Detected	28	C+
67	El Monte	5.60 µg/L	Detected	79	F
68	Lamont	5.60 µg/L	Detected	40	B+
69	Cottonwood	5.51 µg/L	Detected	7	B
70	Downey	5.50 µg/L	Detected	14	B
71	Rancho Cordova	5.50 µg/L	Detected	115	F
72	Porterville	5.40 µg/L	Detected	74	F
73	Kingsburg	5.40 µg/L	Detected	17	B
74	Hemet	5.30 µg/L	Detected	31	B-
75	Merced	5.20 µg/L	Detected	9	C+
76	Lindsay	5.20 µg/L	Detected	240	F
77	Jurupa Valley	5.10 µg/L	Detected	62	B
78	Glendale	5.00 µg/L	Detected	0	A-
79	Ridgecrest	5.00 µg/L	Detected	26	A-
80	Riverbank	5.00 µg/L	Detected	75	D
81	Temecula	4.90 µg/L	Detected	12	C+
82	Rohnert Park	4.90 µg/L	Detected	21	F
83	Pomona	4.80 µg/L	Detected	6	C+
84	Shafter	4.70 µg/L	Detected	25	A-
85	Arvin	4.70 µg/L	Detected	81	C+
86	South Pasadena	4.60 µg/L	Detected	5	A
87	Manteca	4.50 µg/L	Detected	39	B-
88	Monterey Park	4.50 µg/L	Detected	1	B
89	Madera	4.40 µg/L	Detected	564	D
90	Marina	4.30 µg/L	Detected	4	A+
91	San Bruno	4.20 µg/L	Detected	0	A+
92	Santa Clara	4.10 µg/L	Detected	5	B
93	South Gate	4.10 µg/L	Detected	2	B
94	Gonzales	4.00 µg/L	Detected	53	F
95	Chowchilla	3.90 µg/L	Detected	25	A-
96	Fontana	3.80 µg/L	Detected	0	A-
97	Camarillo	3.80 µg/L	Detected	4	B
98	Palm Springs	3.80 µg/L	Detected	16	B
99	Lynwood	3.70 µg/L	Detected	0	B+
100	Loma Linda	3.70 µg/L	Detected	3	A
101	Sunnyvale	3.60 µg/L	Detected	3	A
102	San Fernando	3.50 µg/L	Detected	1	A+
103	Huntington Park	3.40 µg/L	Detected	3	B+
104	Rancho Cucamonga	3.30 µg/L	Detected	0	B+
105	Rialto	3.30 µg/L	Detected	6	B+
106	Los Angeles	3.26 µg/L	Detected	94	F
107	Santa Fe Springs	3.20 µg/L	Detected	1	B+
108	Lincoln	3.20 µg/L	Detected	6	A-
109	Yucca Valley	3.20 µg/L	Detected	7	A-
110	Oakdale	3.10 µg/L	Detected	34	C-
111	Roseville	3.00 µg/L	Detected	11	B
112	Citrus Heights	3.00 µg/L	Detected	2	A
113	San Bernardin0	2.90 µg/L	Detected	0	A-
114	Lathrop	2.90 µg/L	Detected	44	B
115	Reedley	2.90 µg/L	Detected	12	B-
116	Paso Robles	2.80 µg/L	Detected	42	F
117	Nipomo	2.80 µg/L	Detected	1	A
118	Fountain Valley	2.77 µg/L	Detected	0	A
119	Tulare	2.70 µg/L	Detected	61	C-
120	Greenfield	2.70 µg/L	Detected	17	B
121	Highland	2.60 µg/L	Detected	3	B+
122	Ceres	2.60 µg/L	Detected	129	F
123	Monrovia	2.60 µg/L	Detected	0	B+
124	Exeter	2.50 µg/L	Detected	41	B
125	Newhall	2.40 µg/L	Detected	1	B+
126	Brea	2.40 µg/L	Detected	0	A
127	Parlier	2.40 µg/L	Detected	14	A-
128	Clovis	2.30 µg/L	Detected	221	F
129	La Habra	2.30 µg/L	Detected	0	A-
130	Hamilton City	2.28 µg/L	Detected	0	A+
131	Crescent City	2.20 µg/L	Detected	14	C
132	Cutten	2.20 µg/L	Detected	5	A+
133	Garden Grove	2.16 µg/L	Detected	2	B
134	Bakersfield	2.10 µg/L	Detected	690	F
135	Santa Ana	2.06 µg/L	Detected	8	C
136	Buena Park	2.02 µg/L	Detected	1	B+
137	Riverside	2.00 µg/L	Detected	13	C
138	Colton	2.00 µg/L	Detected	5	B-
139	Carmichael	2.00 µg/L	Detected	1	B+
140	Sanger	1.90 µg/L	Detected	16	C
141	Santa Barbara	1.80 µg/L	Detected	52	F
142	Dinuba	1.80 µg/L	Detected	24	A-
143	San Bernardino	1.70 µg/L	Detected	192	F
144	Gilroy	1.70 µg/L	Detected	28	C+
145	Norwalk	1.70 µg/L	Detected	1	A-
146	Cupertino	1.70 µg/L	Detected	3	A+
147	Pacific Grove	1.62 µg/L	Detected	15	B-
148	Hawthorne	1.60 µg/L	Detected	3	B
149	Santa Monica	1.60 µg/L	Detected	0	B
150	Mountain View	1.60 µg/L	Detected	3	A
151	Petaluma	1.60 µg/L	Detected	2	B
152	Upland	1.50 µg/L	Detected	4	B+
153	Altadena	1.50 µg/L	Detected	2	B+
154	Pala	1.50 µg/L	Detected	30	C-
155	Sierra Madre	1.50 µg/L	Detected	5	A
156	Westminster	1.45 µg/L	Detected	2	A-
157	Arroyo Grande	1.41 µg/L	Detected	93	F
158	Perris	1.40 µg/L	Detected	0	A
159	Lakewood	1.40 µg/L	Detected	1	A-
160	Truckee	1.40 µg/L	Detected	7	A-
161	Bellflower	1.40 µg/L	Detected	0	B+
162	Livermore	1.40 µg/L	Detected	53	B
163	El Verano	1.40 µg/L	Detected	0	B+
164	Taft	1.40 µg/L	Detected	0	A-
165	Carpinteria	1.40 µg/L	Detected	5	A
166	Orange	1.39 µg/L	Detected	3	B
167	Fullerton	1.36 µg/L	Detected	8	B
168	Cudahy	1.30 µg/L	Detected	3	B+
169	Grand Terrace	1.30 µg/L	Detected	1	B
170	Santa Maria	1.20 µg/L	Detected	36	F
171	La Verne	1.20 µg/L	Detected	6	B+
172	South Lake Tahoe	1.10 µg/L	Detected	15	C
173	Baldwin Park	1.10 µg/L	Detected	1	A
174	Norco	1.10 µg/L	Detected	39	F
175	Livingston	1.10 µg/L	Detected	29	C-
176	Nuevo	1.01 µg/L	Detected	6	B+
177	Adelanto	1.00 µg/L	Detected	13	C
178	Vernon	1.00 µg/L	Detected	3	A
179	Corcoran	0.97 µg/L	Detected	3	A
180	Pico Rivera	0.94 µg/L	Detected	4	B
181	Sonoma	0.93 µg/L	Detected	5	B-
182	Whittier	0.92 µg/L	Detected	4	C+
183	Chico	0.90 µg/L	Detected	306	F
184	Half Moon Bay	0.87 µg/L	Detected	6	A
185	Goleta	0.85 µg/L	Detected	11	B
186	Susanville	0.84 µg/L	Detected	34	A-
187	Temescal Valley	0.83 µg/L	Detected	2	A
188	Lake Elsinore	0.77 µg/L	Detected	8	A
189	Irvine	0.72 µg/L	Detected	84	F
190	Anderson	0.72 µg/L	Detected	14	C-
191	Farmersville	0.70 µg/L	Detected	20	B+
192	Costa Mesa	0.68 µg/L	Detected	2	A-
193	Westlake Village	0.68 µg/L	Detected	8	F
194	Walnut	0.66 µg/L	Detected	1	A-
195	Thousand Oaks	0.66 µg/L	Detected	1	A
196	Healdsburg	0.64 µg/L	Detected	12	B+
197	Apple Valley	0.59 µg/L	Detected	57	D
198	Moorpark	0.58 µg/L	Detected	1	A-
199	Glendora	0.57 µg/L	Detected	0	A-
200	Calabasas	0.55 µg/L	Detected	14	A-
201	Brooks	0.55 µg/L	Detected	2	B+
202	Redding	0.54 µg/L	Detected	49	F
203	Compton	0.54 µg/L	Detected	8	B
204	Paradise	0.54 µg/L	Detected	2	A
205	Rowland Heights	0.53 µg/L	Detected	0	B+
206	La Crescenta	0.53 µg/L	Detected	3	B+
207	Galt	0.53 µg/L	Detected	27	B+
208	Shasta Lake 4510007	0.52 µg/L	Detected	1	A+
209	Huntington Beach	0.51 µg/L	Detected	5	C-
210	Bell Gardens	0.50 µg/L	Detected	0	B
211	Oakley	0.49 µg/L	Detected	60	D
212	Mammoth Lakes	0.49 µg/L	Detected	24	B
213	Santa Rosa	0.48 µg/L	Detected	177	F
214	Montara	0.48 µg/L	Detected	3	A-
215	Fair Oaks	0.47 µg/L	Detected	0	B+
216	Martinez	0.47 µg/L	Detected	0	A
217	Port Hueneme	0.46 µg/L	Detected	0	B+
218	Mckinleyville	0.46 µg/L	Detected	2	A-
219	Windsor	0.44 µg/L	Detected	2	A+
220	Corona	0.43 µg/L	Detected	81	D
221	Camp Pendleton	0.43 µg/L	Detected	13	B
222	Rancho Santa Margarita	0.42 µg/L	Detected	0	A
223	Lompoc	0.41 µg/L	Detected	18	C
224	Arcata	0.41 µg/L	Detected	3	A
225	Corte Madera	0.40 µg/L	Detected	0	A-
226	Tustin	0.40 µg/L	Detected	8	B
227	Novato	0.40 µg/L	Detected	3	B+
228	Lemoore	0.40 µg/L	Detected	112	D
229	Boulder Creek	0.40 µg/L	Detected	119	F
230	Brownsville	0.39 µg/L	Detected	0	A-
231	Olivehurst	0.38 µg/L	Detected	2	A
232	Oxnard	0.37 µg/L	Detected	49	F
233	San Diego	0.36 µg/L	Detected	43	F
234	Carlsbad	0.34 µg/L	Detected	0	A+
235	Atascadero	0.32 µg/L	Detected	1	B
236	Eureka	0.30 µg/L	Detected	3	A-
237	Fairfield	0.29 µg/L	Detected	7	B-
238	Inglewood	0.29 µg/L	Detected	3	A-
239	Fremont	0.28 µg/L	Detected	3	B-
240	West Sacramento	0.27 µg/L	Detected	1	B+
241	Newport Beach	0.26 µg/L	Detected	4	B+
242	Seal Beach	0.25 µg/L	Detected	0	A-
243	Point Mugu	0.25 µg/L	Detected	11	A-
244	San Clemente	0.24 µg/L	Detected	3	A-
245	Napa	0.23 µg/L	Detected	53	F
246	Oakland	0.22 µg/L	Detected	13	B
247	Palo Alto	0.21 µg/L	Detected	8	A-
248	Simi Valley	0.20 µg/L	Detected	3	A
249	Lomita	0.20 µg/L	Detected	1	A-
250	Ventura	0.19 µg/L	Detected	21	D+
251	Azusa	0.18 µg/L	Detected	2	B+
252	Placentia	0.18 µg/L	Detected	0	B+
253	Yuba City	0.18 µg/L	Detected	24	A-
254	Paramount	0.18 µg/L	Detected	0	A-
255	Montebello	0.18 µg/L	Detected	5	B
256	Ukiah	0.18 µg/L	Detected	14	C+
257	Fillmore	0.18 µg/L	Detected	13	B-
258	Oroville	0.17 µg/L	Detected	7	C-
259	Coalinga	0.17 µg/L	Detected	267	D
260	Grass Valley	0.16 µg/L	Detected	8	A
261	Avenal	0.16 µg/L	Detected	35	B
262	Kirkwood	0.16 µg/L	Detected	0	A
263	Burlingame	0.15 µg/L	Detected	14	A-
264	Auburn	0.15 µg/L	Detected	8	A
265	Fortuna	0.14 µg/L	Detected	7	B-
266	Concord	0.14 µg/L	Detected	19	B-
267	Santa Cruz	0.14 µg/L	Detected	38	F
268	Folsom	0.14 µg/L	Detected	1	A-
269	Millbrae	0.14 µg/L	Detected	1	A-
270	Morro Bay	0.14 µg/L	Detected	12	A-
271	Vallejo	0.13 µg/L	Detected	6	A
272	Milpitas	0.13 µg/L	Detected	2	A-
273	Pacifica	0.13 µg/L	Detected	2	A
274	Menlo Park	0.13 µg/L	Detected	2	A-
275	Hillsborough	0.13 µg/L	Detected	7	A
276	Belmont	0.12 µg/L	Detected	3	A+
277	Clearlake	0.12 µg/L	Detected	5	B+
278	Escondido	0.11 µg/L	Detected	10	B
279	Laguna Beach	0.11 µg/L	Detected	2	B
280	Sonora	0.11 µg/L	Detected	25	D+
281	San Andreas	0.11 µg/L	Detected	17	B-
282	Manhattan Beach	0.11 µg/L	Detected	1	A-
283	Benicia	0.11 µg/L	Detected	1	A-
284	Laguna Hills	0.10 µg/L	Detected	1	B+
285	Antioch	0.10 µg/L	Detected	3	A
286	Cerritos	0.10 µg/L	Detected	0	B
287	Ramona	0.10 µg/L	Detected	36	C
288	Orangevale	0.10 µg/L	Detected	0	A
289	Granite Bay	0.10 µg/L	Detected	43	B-
290	American Canyon	0.09 µg/L	Detected	15	A-
291	Placerville	0.09 µg/L	Detected	6	A-
292	Fallbrook	0.09 µg/L	Detected	3	A
293	Hayward	0.09 µg/L	Detected	0	A-
294	San Marcos	0.09 µg/L	Detected	27	D
295	Imperial Beach	0.09 µg/L	Detected	1	A
296	Foster City	0.09 µg/L	Detected	2	A+
297	Stanford	0.09 µg/L	Detected	3	A+
298	El Segundo	0.09 µg/L	Detected	0	A-
299	Oak View	0.09 µg/L	Detected	12	B+
300	Chula Vista	0.09 µg/L	Detected	1	B+
301	Grover Beach	0.08 µg/L	Detected	34	F
302	Long Beach	0.07 µg/L	Detected	2	C
303	Valley Center	0.07 µg/L	Detected	15	F
304	Spring Valley	0.07 µg/L	Detected	4	B
305	Pittsburg	0.07 µg/L	Detected	0	A
306	San Juan Capistrano	0.07 µg/L	Detected	5	B+
307	Lakeside	0.06 µg/L	Detected	0	A-
308	Encinitas	0.06 µg/L	Detected	55	F
309	La Palma	0.06 µg/L	Detected	0	A-
310	Scotts Valley	0.06 µg/L	Detected	11	B-
311	Santee	0.06 µg/L	Detected	14	B
312	Rancho Santa Fe	0.06 µg/L	Detected	3	A-
313	Torrance	0.06 µg/L	Detected	0	A-
314	Vista	0.06 µg/L	Detected	0	A-
315	El Centro	0.06 µg/L	Detected	14	C-
316	Redwood City	0.05 µg/L	Detected	10	B+
317	Lake Forest	0.05 µg/L	Detected	38	B-
318	La Mesa	0.05 µg/L	Detected	0	A+
319	Oceanside	0.05 µg/L	Detected	2	A-
320	Firebaugh	0.05 µg/L	Detected	89	D
321	Beverly Hills	0.04 µg/L	Detected	18	B
322	Calexico	0.04 µg/L	Detected	7	B-
323	Trabuco Canyon	0.04 µg/L	Detected	2	A-
324	Poway	0.04 µg/L	Detected	0	A-
325	Signal Hill	0.04 µg/L	Detected	6	B
326	Discovery Bay	0.04 µg/L	Detected	3	A+
327	Carmel Valley	0.03 µg/L	Detected	45	C+
328	San Jacinto	0.03 µg/L	Detected	9	B
329	Brawley	0.03 µg/L	Detected	5	A-
330	East Palo Alto	0.03 µg/L	Detected	8	A

FAQ

Frequently asked questions about chromium-6 in California

Is chromium-6 in California 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. 330 cities in California 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 California 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 California?

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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