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

328

Cities Tested

328

Detected

100%

% Detected

3.85 µg/L

State Avg

▼ 0% vs national

vs National

620

Health Violations

Analysis

Chromium-6 in California: what the data shows

California has 328 cities with chromium-6 data from the EPA's UCMR 3 program (2013–2015). Hexavalent chromium (Cr VI) was detected in 328 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%

328 of 328 cities

← = Exactly at national rate

National avg

100%

3934 of 3934 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	Coachella	20.00 µg/L	Detected	11	C-
10	Vacaville	20.00 µg/L	Detected	26	F
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	Chino	6.20 µg/L	Detected	9	B
60	Red Bluff	6.20 µg/L	Detected	23	F
61	Elk Grove	5.90 µg/L	Detected	28	C
62	Fort Irwin	5.90 µg/L	Detected	60	B+
63	Salinas	5.80 µg/L	Detected	639	F
64	Edwards Afb	5.80 µg/L	Detected	8	A-
65	Soledad	5.70 µg/L	Detected	28	C+
66	El Monte	5.60 µg/L	Detected	79	F
67	Lamont	5.60 µg/L	Detected	40	B+
68	Cottonwood	5.51 µg/L	Detected	7	B
69	Downey	5.50 µg/L	Detected	14	B
70	Rancho Cordova	5.50 µg/L	Detected	115	F
71	Porterville	5.40 µg/L	Detected	74	F
72	Kingsburg	5.40 µg/L	Detected	17	B
73	Hemet	5.30 µg/L	Detected	31	B-
74	Merced	5.20 µg/L	Detected	9	C+
75	Lindsay	5.20 µg/L	Detected	240	F
76	Jurupa Valley	5.10 µg/L	Detected	62	B
77	Glendale	5.00 µg/L	Detected	0	A-
78	Ridgecrest	5.00 µg/L	Detected	26	A-
79	Riverbank	5.00 µg/L	Detected	75	D
80	Temecula	4.90 µg/L	Detected	12	C+
81	Rohnert Park	4.90 µg/L	Detected	21	F
82	Pomona	4.80 µg/L	Detected	6	C+
83	Shafter	4.70 µg/L	Detected	25	A-
84	Arvin	4.70 µg/L	Detected	81	C+
85	South Pasadena	4.60 µg/L	Detected	5	A
86	Manteca	4.50 µg/L	Detected	39	B-
87	Monterey Park	4.50 µg/L	Detected	1	B
88	Madera	4.40 µg/L	Detected	564	D
89	Marina	4.30 µg/L	Detected	4	A+
90	San Bruno	4.20 µg/L	Detected	0	A+
91	Santa Clara	4.10 µg/L	Detected	5	B
92	South Gate	4.10 µg/L	Detected	2	B
93	Gonzales	4.00 µg/L	Detected	53	F
94	Chowchilla	3.90 µg/L	Detected	25	A-
95	Fontana	3.80 µg/L	Detected	0	A-
96	Camarillo	3.80 µg/L	Detected	4	B
97	Palm Springs	3.80 µg/L	Detected	16	B
98	Lynwood	3.70 µg/L	Detected	0	B+
99	Loma Linda	3.70 µg/L	Detected	3	A
100	Sunnyvale	3.60 µg/L	Detected	3	A
101	San Fernando	3.50 µg/L	Detected	1	A+
102	Huntington Park	3.40 µg/L	Detected	3	B+
103	Rancho Cucamonga	3.30 µg/L	Detected	0	B+
104	Rialto	3.30 µg/L	Detected	6	B+
105	Los Angeles	3.26 µg/L	Detected	94	F
106	Lincoln	3.20 µg/L	Detected	6	A-
107	Yucca Valley	3.20 µg/L	Detected	7	A-
108	Santa Fe Springs	3.20 µg/L	Detected	1	B+
109	Oakdale	3.10 µg/L	Detected	34	C-
110	Roseville	3.00 µg/L	Detected	11	B
111	Citrus Heights	3.00 µg/L	Detected	2	A
112	San Bernardin0	2.90 µg/L	Detected	0	A-
113	Lathrop	2.90 µg/L	Detected	44	B
114	Reedley	2.90 µg/L	Detected	12	B-
115	Paso Robles	2.80 µg/L	Detected	42	F
116	Nipomo	2.80 µg/L	Detected	1	A
117	Fountain Valley	2.77 µg/L	Detected	0	A
118	Tulare	2.70 µg/L	Detected	61	C-
119	Greenfield	2.70 µg/L	Detected	17	B
120	Highland	2.60 µg/L	Detected	3	B+
121	Ceres	2.60 µg/L	Detected	129	F
122	Monrovia	2.60 µg/L	Detected	0	B+
123	Exeter	2.50 µg/L	Detected	41	B
124	Newhall	2.40 µg/L	Detected	1	B+
125	Brea	2.40 µg/L	Detected	0	A
126	Parlier	2.40 µg/L	Detected	14	A-
127	Clovis	2.30 µg/L	Detected	221	F
128	La Habra	2.30 µg/L	Detected	0	A-
129	Hamilton City	2.28 µg/L	Detected	0	A+
130	Crescent City	2.20 µg/L	Detected	14	C
131	Cutten	2.20 µg/L	Detected	5	A+
132	Garden Grove	2.16 µg/L	Detected	2	B
133	Bakersfield	2.10 µg/L	Detected	690	F
134	Santa Ana	2.06 µg/L	Detected	8	C
135	Buena Park	2.02 µg/L	Detected	1	B+
136	Riverside	2.00 µg/L	Detected	13	C
137	Colton	2.00 µg/L	Detected	5	B-
138	Carmichael	2.00 µg/L	Detected	1	B+
139	Sanger	1.90 µg/L	Detected	16	C
140	Santa Barbara	1.80 µg/L	Detected	52	F
141	Dinuba	1.80 µg/L	Detected	24	A-
142	San Bernardino	1.70 µg/L	Detected	192	F
143	Gilroy	1.70 µg/L	Detected	28	C+
144	Norwalk	1.70 µg/L	Detected	1	A-
145	Cupertino	1.70 µg/L	Detected	3	A+
146	Pacific Grove	1.62 µg/L	Detected	15	B-
147	Hawthorne	1.60 µg/L	Detected	3	B
148	Santa Monica	1.60 µg/L	Detected	0	B
149	Mountain View	1.60 µg/L	Detected	3	A
150	Petaluma	1.60 µg/L	Detected	2	B
151	Upland	1.50 µg/L	Detected	4	B+
152	Altadena	1.50 µg/L	Detected	2	B+
153	Pala	1.50 µg/L	Detected	30	C-
154	Sierra Madre	1.50 µg/L	Detected	5	A
155	Westminster	1.45 µg/L	Detected	2	A-
156	Arroyo Grande	1.41 µg/L	Detected	93	F
157	Perris	1.40 µg/L	Detected	0	A
158	Lakewood	1.40 µg/L	Detected	1	A-
159	Truckee	1.40 µg/L	Detected	7	A-
160	Bellflower	1.40 µg/L	Detected	0	B+
161	Livermore	1.40 µg/L	Detected	53	B
162	El Verano	1.40 µg/L	Detected	0	B+
163	Taft	1.40 µg/L	Detected	0	A-
164	Carpinteria	1.40 µg/L	Detected	5	A
165	Orange	1.39 µg/L	Detected	3	B
166	Fullerton	1.36 µg/L	Detected	8	B
167	Cudahy	1.30 µg/L	Detected	3	B+
168	Grand Terrace	1.30 µg/L	Detected	1	B
169	Santa Maria	1.20 µg/L	Detected	36	F
170	La Verne	1.20 µg/L	Detected	6	B+
171	South Lake Tahoe	1.10 µg/L	Detected	15	C
172	Baldwin Park	1.10 µg/L	Detected	1	A
173	Norco	1.10 µg/L	Detected	39	F
174	Livingston	1.10 µg/L	Detected	29	C-
175	Nuevo	1.01 µg/L	Detected	6	B+
176	Adelanto	1.00 µg/L	Detected	13	C
177	Vernon	1.00 µg/L	Detected	3	A
178	Corcoran	0.97 µg/L	Detected	3	A
179	Pico Rivera	0.94 µg/L	Detected	4	B
180	Sonoma	0.93 µg/L	Detected	5	B-
181	Whittier	0.92 µg/L	Detected	4	C+
182	Chico	0.90 µg/L	Detected	306	F
183	Half Moon Bay	0.87 µg/L	Detected	6	A
184	Goleta	0.85 µg/L	Detected	11	B
185	Susanville	0.84 µg/L	Detected	34	A-
186	Temescal Valley	0.83 µg/L	Detected	2	A
187	Lake Elsinore	0.77 µg/L	Detected	8	A
188	Irvine	0.72 µg/L	Detected	84	F
189	Anderson	0.72 µg/L	Detected	14	C-
190	Farmersville	0.70 µg/L	Detected	20	B+
191	Costa Mesa	0.68 µg/L	Detected	2	A-
192	Westlake Village	0.68 µg/L	Detected	8	F
193	Walnut	0.66 µg/L	Detected	1	A-
194	Thousand Oaks	0.66 µg/L	Detected	1	A
195	Healdsburg	0.64 µg/L	Detected	12	B+
196	Apple Valley	0.59 µg/L	Detected	57	D
197	Moorpark	0.58 µg/L	Detected	1	A-
198	Glendora	0.57 µg/L	Detected	0	A-
199	Calabasas	0.55 µg/L	Detected	14	A-
200	Brooks	0.55 µg/L	Detected	2	B+
201	Redding	0.54 µg/L	Detected	49	F
202	Compton	0.54 µg/L	Detected	8	B
203	Paradise	0.54 µg/L	Detected	2	A
204	Rowland Heights	0.53 µg/L	Detected	0	B+
205	La Crescenta	0.53 µg/L	Detected	3	B+
206	Galt	0.53 µg/L	Detected	27	B+
207	Shasta Lake 4510007	0.52 µg/L	Detected	1	A+
208	Huntington Beach	0.51 µg/L	Detected	5	C-
209	Bell Gardens	0.50 µg/L	Detected	0	B
210	Oakley	0.49 µg/L	Detected	60	D
211	Mammoth Lakes	0.49 µg/L	Detected	24	B
212	Santa Rosa	0.48 µg/L	Detected	177	F
213	Montara	0.48 µg/L	Detected	3	A-
214	Fair Oaks	0.47 µg/L	Detected	0	B+
215	Martinez	0.47 µg/L	Detected	0	A
216	Port Hueneme	0.46 µg/L	Detected	0	B+
217	Mckinleyville	0.46 µg/L	Detected	2	A-
218	Windsor	0.44 µg/L	Detected	2	A+
219	Corona	0.43 µg/L	Detected	81	D
220	Camp Pendleton	0.43 µg/L	Detected	13	B
221	Rancho Santa Margarita	0.42 µg/L	Detected	0	A
222	Lompoc	0.41 µg/L	Detected	18	C
223	Arcata	0.41 µg/L	Detected	3	A
224	Corte Madera	0.40 µg/L	Detected	0	A-
225	Tustin	0.40 µg/L	Detected	8	B
226	Novato	0.40 µg/L	Detected	3	B+
227	Lemoore	0.40 µg/L	Detected	112	D
228	Boulder Creek	0.40 µg/L	Detected	119	F
229	Brownsville	0.39 µg/L	Detected	0	A-
230	Olivehurst	0.38 µg/L	Detected	2	A
231	Oxnard	0.37 µg/L	Detected	49	F
232	San Diego	0.36 µg/L	Detected	43	F
233	Carlsbad	0.34 µg/L	Detected	0	A+
234	Atascadero	0.32 µg/L	Detected	1	B
235	Eureka	0.30 µg/L	Detected	3	A-
236	Fairfield	0.29 µg/L	Detected	7	B-
237	Inglewood	0.29 µg/L	Detected	3	A-
238	Fremont	0.28 µg/L	Detected	3	B-
239	West Sacramento	0.27 µg/L	Detected	1	B+
240	Newport Beach	0.26 µg/L	Detected	4	B+
241	Seal Beach	0.25 µg/L	Detected	0	A-
242	Point Mugu	0.25 µg/L	Detected	11	A-
243	San Clemente	0.24 µg/L	Detected	3	A-
244	Napa	0.23 µg/L	Detected	53	F
245	Oakland	0.22 µg/L	Detected	13	B
246	Palo Alto	0.21 µg/L	Detected	8	A-
247	Simi Valley	0.20 µg/L	Detected	3	A
248	Lomita	0.20 µg/L	Detected	1	A-
249	Ventura	0.19 µg/L	Detected	21	D+
250	Azusa	0.18 µg/L	Detected	2	B+
251	Placentia	0.18 µg/L	Detected	0	B+
252	Yuba City	0.18 µg/L	Detected	24	A-
253	Paramount	0.18 µg/L	Detected	0	A-
254	Montebello	0.18 µg/L	Detected	5	B
255	Ukiah	0.18 µg/L	Detected	14	C+
256	Fillmore	0.18 µg/L	Detected	13	B-
257	Oroville	0.17 µg/L	Detected	7	C-
258	Coalinga	0.17 µg/L	Detected	267	D
259	Grass Valley	0.16 µg/L	Detected	8	A
260	Avenal	0.16 µg/L	Detected	35	B
261	Kirkwood	0.16 µg/L	Detected	0	A
262	Burlingame	0.15 µg/L	Detected	14	A-
263	Auburn	0.15 µg/L	Detected	8	A
264	Fortuna	0.14 µg/L	Detected	7	B-
265	Concord	0.14 µg/L	Detected	19	B-
266	Santa Cruz	0.14 µg/L	Detected	38	F
267	Folsom	0.14 µg/L	Detected	1	A-
268	Millbrae	0.14 µg/L	Detected	1	A-
269	Morro Bay	0.14 µg/L	Detected	12	A-
270	Vallejo	0.13 µg/L	Detected	6	A
271	Milpitas	0.13 µg/L	Detected	2	A-
272	Pacifica	0.13 µg/L	Detected	2	A
273	Menlo Park	0.13 µg/L	Detected	2	A-
274	Hillsborough	0.13 µg/L	Detected	7	A
275	Belmont	0.12 µg/L	Detected	3	A+
276	Clearlake	0.12 µg/L	Detected	5	B+
277	Escondido	0.11 µg/L	Detected	10	B
278	Laguna Beach	0.11 µg/L	Detected	2	B
279	Sonora	0.11 µg/L	Detected	25	D+
280	San Andreas	0.11 µg/L	Detected	17	B-
281	Manhattan Beach	0.11 µg/L	Detected	1	A-
282	Benicia	0.11 µg/L	Detected	1	A-
283	Laguna Hills	0.10 µg/L	Detected	1	B+
284	Antioch	0.10 µg/L	Detected	3	A
285	Cerritos	0.10 µg/L	Detected	0	B
286	Ramona	0.10 µg/L	Detected	36	C
287	Orangevale	0.10 µg/L	Detected	0	A
288	Granite Bay	0.10 µg/L	Detected	43	B-
289	American Canyon	0.09 µg/L	Detected	15	A-
290	Placerville	0.09 µg/L	Detected	6	A-
291	Fallbrook	0.09 µg/L	Detected	3	A
292	Hayward	0.09 µg/L	Detected	0	A-
293	San Marcos	0.09 µg/L	Detected	27	D
294	Imperial Beach	0.09 µg/L	Detected	1	A
295	Foster City	0.09 µg/L	Detected	2	A+
296	Stanford	0.09 µg/L	Detected	3	A+
297	El Segundo	0.09 µg/L	Detected	0	A-
298	Oak View	0.09 µg/L	Detected	12	B+
299	Chula Vista	0.09 µg/L	Detected	1	B+
300	Grover Beach	0.08 µg/L	Detected	34	F
301	Long Beach	0.07 µg/L	Detected	2	C
302	Valley Center	0.07 µg/L	Detected	15	F
303	Spring Valley	0.07 µg/L	Detected	4	B
304	Pittsburg	0.07 µg/L	Detected	0	A
305	Lakeside	0.06 µg/L	Detected	0	A-
306	Encinitas	0.06 µg/L	Detected	55	F
307	La Palma	0.06 µg/L	Detected	0	A-
308	Scotts Valley	0.06 µg/L	Detected	11	B-
309	Santee	0.06 µg/L	Detected	14	B
310	Rancho Santa Fe	0.06 µg/L	Detected	3	A-
311	Torrance	0.06 µg/L	Detected	0	A-
312	Vista	0.06 µg/L	Detected	0	A-
313	El Centro	0.06 µg/L	Detected	14	C-
314	Redwood City	0.05 µg/L	Detected	10	B+
315	Lake Forest	0.05 µg/L	Detected	38	B-
316	La Mesa	0.05 µg/L	Detected	0	A+
317	Oceanside	0.05 µg/L	Detected	2	A-
318	Firebaugh	0.05 µg/L	Detected	89	D
319	Beverly Hills	0.04 µg/L	Detected	18	B
320	Calexico	0.04 µg/L	Detected	7	B-
321	Trabuco Canyon	0.04 µg/L	Detected	2	A-
322	Poway	0.04 µg/L	Detected	0	A-
323	Signal Hill	0.04 µg/L	Detected	6	B
324	Discovery Bay	0.04 µg/L	Detected	3	A+
325	Carmel Valley	0.03 µg/L	Detected	45	C+
326	San Jacinto	0.03 µg/L	Detected	9	B
327	Brawley	0.03 µg/L	Detected	5	A-
328	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. 328 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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