Molybdenum Contamination

Molybdenum in California Drinking Water

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

283

Cities Tested

Over HA

% Over HA

11.37 µg/L

State Avg

▲ 2% vs national

vs National

620

Health Violations

Analysis

Molybdenum in California: what the data shows

California has 283 cities with molybdenum data from the EPA's UCMR 3 program (2013–2015). Molybdenum exceeded the 40 µg/L EPA lifetime health advisory in 11 of those cities. The state average max detected level is 11.37 µg/L. Molybdenum is a naturally occurring trace element found in groundwater across the western United States, particularly in areas with shale or copper-mining geology. Industrial sources include mining, steel alloy production, and coal-fired power plants. There is no federal MCL — the EPA lifetime health advisory is 40 µg/L. Molybdenum is an essential nutrient at low doses, but chronic excess intake from drinking water has been linked to elevated uric acid, gout-like symptoms, and possible reproductive effects. Reverse osmosis is the most effective household treatment.

Comparison

Cities exceeding 40 µg/L EPA lifetime HA (no MCL)

California

11 of 283 cities

→ ▲ 2% above national rate (worse)

National avg

36 of 2205 cities

City Map

Molybdenum data across California

Each dot is a city with UCMR 3 molybdenum testing data. Cities where molybdenum exceeds the 40 µg/L EPA lifetime health advisory are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by molybdenum level in California

Highest Molybdenum levels (µg/L)

All Cities

All California cities ranked by molybdenum level

#	City	Level	Over HA?	Violations	Grade
1	Nipomo	190.00 µg/L	Over HA	1	A
2	Sacramento	180.00 µg/L	Over HA	425	F
3	California City	150.00 µg/L	Over HA	22	A-
4	Paso Robles	86.00 µg/L	Over HA	42	F
5	South Lake Tahoe	72.00 µg/L	Over HA	15	C
6	Fillmore	61.00 µg/L	Over HA	13	B-
7	Fort Irwin	59.00 µg/L	Over HA	60	B+
8	Anaheim	49.90 µg/L	Over HA	8	C+
9	Delano	44.00 µg/L	Over HA	67	B
10	Lompoc	43.00 µg/L	Over HA	18	C
11	Covina	41.00 µg/L	Over HA	10	B
12	Montara	37.90 µg/L	No	3	A-
13	Buena Park	37.50 µg/L	No	1	B+
14	Moorpark	34.70 µg/L	No	1	A-
15	Lake Elsinore	33.00 µg/L	No	8	A
16	Desert Hot Springs	32.00 µg/L	No	4	A
17	Simi Valley	31.00 µg/L	No	3	A
18	Greenfield	31.00 µg/L	No	17	B
19	Marina	30.00 µg/L	No	4	A+
20	La Habra	29.00 µg/L	No	0	A-
21	Norco	28.00 µg/L	No	39	F
22	Arvin	27.00 µg/L	No	81	C+
23	Grover Beach	27.00 µg/L	No	34	F
24	Coachella	26.00 µg/L	No	11	C-
25	Yucca Valley	24.00 µg/L	No	7	A-
26	Hemet	23.00 µg/L	No	31	B-
27	Ventura	22.00 µg/L	No	21	D+
28	Norwalk	22.00 µg/L	No	1	A-
29	Indio	21.00 µg/L	No	12	F
30	Salinas	21.00 µg/L	No	639	F
31	Yucaipa	21.00 µg/L	No	9	C+
32	Cerritos	21.00 µg/L	No	0	B
33	Mcfarland	21.00 µg/L	No	42	C+
34	Fullerton	20.40 µg/L	No	8	B
35	Tustin	20.20 µg/L	No	8	B
36	San Jose	19.00 µg/L	No	142	F
37	Irvine	19.00 µg/L	No	84	F
38	El Monte	19.00 µg/L	No	79	F
39	Palm Desert	19.00 µg/L	No	12	C+
40	Temecula	19.00 µg/L	No	12	C+
41	Ridgecrest	19.00 µg/L	No	26	A-
42	Twentynine Palms	19.00 µg/L	No	70	B+
43	La Palma	18.90 µg/L	No	0	A-
44	Camarillo	18.00 µg/L	No	4	B
45	Arcadia	18.00 µg/L	No	2	B
46	Lemoore	18.00 µg/L	No	112	D
47	Arroyo Grande	18.00 µg/L	No	93	F
48	Corona	17.00 µg/L	No	81	D
49	Pasadena	16.00 µg/L	No	92	F
50	Boulder Creek	16.00 µg/L	No	119	F
51	Susanville	15.80 µg/L	No	34	A-
52	Perris	15.00 µg/L	No	0	A
53	Point Mugu	15.00 µg/L	No	11	A-
54	Pacific Grove	14.40 µg/L	No	15	B-
55	Bermuda Dunes	14.40 µg/L	No	0	A+
56	Alhambra	14.00 µg/L	No	7	A-
57	Downey	14.00 µg/L	No	14	B
58	Highland	14.00 µg/L	No	3	B+
59	Burbank	13.00 µg/L	No	1	A-
60	Placentia	13.00 µg/L	No	0	B+
61	Palm Springs	13.00 µg/L	No	16	B
62	Carpinteria	13.00 µg/L	No	5	A
63	Mendota	13.00 µg/L	No	3	A
64	Rosemead	12.00 µg/L	No	17	C-
65	Hanford	12.00 µg/L	No	197	D+
66	Santa Paula	12.00 µg/L	No	5	A-
67	Soledad	12.00 µg/L	No	28	C+
68	Vernon	12.00 µg/L	No	3	A
69	South Pasadena	12.00 µg/L	No	5	A
70	Lamont	12.00 µg/L	No	40	B+
71	Santa Ana	11.10 µg/L	No	8	C
72	Hawthorne	11.00 µg/L	No	3	B
73	Oxnard	11.00 µg/L	No	49	F
74	San Dimas	11.00 µg/L	No	6	B-
75	Victorville	11.00 µg/L	No	1	B+
76	Santa Barbara	11.00 µg/L	No	52	F
77	Madera	11.00 µg/L	No	564	D
78	Goleta	11.00 µg/L	No	11	B
79	Port Hueneme	11.00 µg/L	No	0	B+
80	Livingston	11.00 µg/L	No	29	C-
81	Pala	11.00 µg/L	No	30	C-
82	Los Angeles	10.10 µg/L	No	94	F
83	Bakersfield	10.00 µg/L	No	690	F
84	Nuevo	10.00 µg/L	No	6	B+
85	Huntington Park	9.80 µg/L	No	3	B+
86	Modesto	9.70 µg/L	No	76	D
87	Lynwood	9.40 µg/L	No	0	B+
88	Compton	9.10 µg/L	No	8	B
89	Banning	8.90 µg/L	No	15	B-
90	Rancho Cordova	8.80 µg/L	No	115	F
91	Quartz Hill	8.80 µg/L	No	1	A-
92	South Gate	8.70 µg/L	No	2	B
93	Carmel Valley	8.43 µg/L	No	45	C+
94	Exeter	8.30 µg/L	No	41	B
95	Chula Vista	8.20 µg/L	No	1	B+
96	Ontario	8.10 µg/L	No	1	B+
97	Ceres	7.90 µg/L	No	129	F
98	San Clemente	7.80 µg/L	No	3	A-
99	Orange	7.70 µg/L	No	3	B
100	Monterey Park	7.70 µg/L	No	1	B
101	Camp Pendleton	7.60 µg/L	No	13	B
102	Farmersville	7.60 µg/L	No	20	B+
103	Newhall	7.50 µg/L	No	1	B+
104	Redlands	7.50 µg/L	No	2	B
105	Mammoth Lakes	7.50 µg/L	No	24	B
106	Tulare	7.40 µg/L	No	61	C-
107	Paramount	7.40 µg/L	No	0	A-
108	Costa Mesa	7.20 µg/L	No	2	A-
109	Gonzales	7.20 µg/L	No	53	F
110	Fresno	7.10 µg/L	No	523	F
111	Long Beach	7.10 µg/L	No	2	C
112	Altadena	7.10 µg/L	No	2	B+
113	Scotts Valley	7.10 µg/L	No	11	B-
114	Westminster	7.00 µg/L	No	2	A-
115	Kingsburg	7.00 µg/L	No	17	B
116	Grand Terrace	6.90 µg/L	No	1	B
117	Huntington Beach	6.80 µg/L	No	5	C-
118	Seal Beach	6.80 µg/L	No	0	A-
119	Chino	6.70 µg/L	No	9	B
120	Imperial	6.70 µg/L	No	36	C+
121	Thousand Oaks	6.60 µg/L	No	1	A
122	Westlake Village	6.60 µg/L	No	8	F
123	Atascadero	6.50 µg/L	No	1	B
124	Glendale	6.40 µg/L	No	0	A-
125	Brentwood	6.30 µg/L	No	91	F
126	Rancho Cucamonga	6.20 µg/L	No	0	B+
127	Jurupa Valley	6.20 µg/L	No	62	B
128	La Verne	6.20 µg/L	No	6	B+
129	Turlock	6.10 µg/L	No	16	B-
130	Colton	6.10 µg/L	No	5	B-
131	El Centro	6.10 µg/L	No	14	C-
132	Loma Linda	6.10 µg/L	No	3	A
133	Rosamond	6.10 µg/L	No	205	F
134	Fountain Valley	5.90 µg/L	No	0	A
135	Corcoran	5.90 µg/L	No	3	A
136	Cudahy	5.90 µg/L	No	3	B+
137	29 Palms	5.90 µg/L	No	3	B
138	Garden Grove	5.80 µg/L	No	2	B
139	Brawley	5.80 µg/L	No	5	A-
140	Glendora	5.70 µg/L	No	0	A-
141	Calexico	5.70 µg/L	No	7	B-
142	San Jacinto	5.70 µg/L	No	9	B
143	Santa Maria	5.60 µg/L	No	36	F
144	Gilroy	5.50 µg/L	No	28	C+
145	Newport Beach	5.40 µg/L	No	4	B+
146	Beverly Hills	5.40 µg/L	No	18	B
147	San Luis Obispo	5.30 µg/L	No	27	F
148	Lomita	5.20 µg/L	No	1	A-
149	Santa Fe Springs	5.20 µg/L	No	1	B+
150	Trabuco Canyon	5.20 µg/L	No	2	A-
151	Edwards Afb	5.20 µg/L	No	8	A-
152	Rancho Santa Margarita	5.10 µg/L	No	0	A
153	Walnut	5.10 µg/L	No	1	A-
154	Inglewood	5.10 µg/L	No	3	A-
155	Laguna Beach	5.10 µg/L	No	2	B
156	Lake Forest	5.10 µg/L	No	38	B-
157	San Bernardin0	5.00 µg/L	No	0	A-
158	Santa Clara	5.00 µg/L	No	5	B
159	Lakewood	5.00 µg/L	No	1	A-
160	Porterville	5.00 µg/L	No	74	F
161	Fallbrook	5.00 µg/L	No	3	A
162	Lindsay	5.00 µg/L	No	240	F
163	Rialto	4.90 µg/L	No	6	B+
164	La Crescenta	4.90 µg/L	No	3	B+
165	Coalinga	4.90 µg/L	No	267	D
166	Fontana	4.80 µg/L	No	0	A-
167	Manhattan Beach	4.80 µg/L	No	1	A-
168	Rancho Santa Fe	4.80 µg/L	No	3	A-
169	San Diego	4.70 µg/L	No	43	F
170	Riverside	4.70 µg/L	No	13	C
171	Oceanside	4.70 µg/L	No	2	A-
172	Laguna Hills	4.70 µg/L	No	1	B+
173	Torrance	4.70 µg/L	No	0	A-
174	Montclair	4.70 µg/L	No	0	B+
175	Valley Center	4.70 µg/L	No	15	F
176	Signal Hill	4.70 µg/L	No	6	B
177	San Marcos	4.60 µg/L	No	27	D
178	Watsonville	4.60 µg/L	No	74	F
179	Brea	4.60 µg/L	No	0	A
180	Ramona	4.60 µg/L	No	36	C
181	Clovis	4.50 µg/L	No	221	F
182	Encinitas	4.50 µg/L	No	55	F
183	Calabasas	4.50 µg/L	No	14	A-
184	Hollister	4.50 µg/L	No	132	F
185	Temescal Valley	4.50 µg/L	No	2	A
186	El Segundo	4.50 µg/L	No	0	A-
187	Spring Valley	4.40 µg/L	No	4	B
188	Palmdale	4.40 µg/L	No	15	C+
189	Adelanto	4.40 µg/L	No	13	C
190	Escondido	4.31 µg/L	No	10	B
191	La Mesa	4.30 µg/L	No	0	A+
192	Carlsbad	4.30 µg/L	No	0	A+
193	Rowland Heights	4.30 µg/L	No	0	B+
194	Galt	4.30 µg/L	No	27	B+
195	Blythe	4.30 µg/L	No	143	D
196	Sierra Madre	4.30 µg/L	No	5	A
197	Dinuba	4.30 µg/L	No	24	A-
198	Tracy	4.20 µg/L	No	45	C
199	Lakeside	4.20 µg/L	No	0	A-
200	Phelan	4.20 µg/L	No	0	B+
201	Ripon	4.20 µg/L	No	10	A-
202	Vista	4.10 µg/L	No	0	A-
203	Imperial Beach	4.10 µg/L	No	1	A
204	Davis	4.00 µg/L	No	47	B+
205	Santa Monica	4.00 µg/L	No	0	B
206	Poway	4.00 µg/L	No	0	A-
207	San Fernando	4.00 µg/L	No	1	A+
208	Taft	4.00 µg/L	No	0	A-
209	Kerman	4.00 µg/L	No	13	B
210	Discovery Bay	4.00 µg/L	No	3	A+
211	Bell Gardens	4.00 µg/L	No	0	B
212	Pomona	3.90 µg/L	No	6	C+
213	Santee	3.90 µg/L	No	14	B
214	Upland	3.90 µg/L	No	4	B+
215	Chino Hills	3.90 µg/L	No	2	A
216	Pico Rivera	3.80 µg/L	No	4	B
217	Apple Valley	3.60 µg/L	No	57	D
218	Atwater	3.60 µg/L	No	3	B+
219	Woodland	3.50 µg/L	No	52	F
220	Rohnert Park	3.50 µg/L	No	21	F
221	Oak View	3.50 µg/L	No	12	B+
222	Vacaville	3.40 µg/L	No	26	F
223	Patterson	3.20 µg/L	No	35	B+
224	Chowchilla	3.20 µg/L	No	25	A-
225	Firebaugh	3.20 µg/L	No	89	D
226	Lodi	3.10 µg/L	No	16	C+
227	Pittsburg	3.10 µg/L	No	0	A
228	Bellflower	3.10 µg/L	No	0	B+
229	Soquel	3.10 µg/L	No	1	A
230	Lathrop	3.10 µg/L	No	44	B
231	Sonoma	3.10 µg/L	No	5	B-
232	Newman	3.10 µg/L	No	3	A-
233	Whittier	3.00 µg/L	No	4	C+
234	Wasco	3.00 µg/L	No	26	B+
235	Morro Bay	3.00 µg/L	No	12	A-
236	Merced	2.90 µg/L	No	9	C+
237	Mountain View	2.90 µg/L	No	3	A
238	Petaluma	2.90 µg/L	No	2	B
239	Manteca	2.80 µg/L	No	39	B-
240	Montebello	2.80 µg/L	No	5	B
241	Half Moon Bay	2.80 µg/L	No	6	A
242	Kirkwood	2.80 µg/L	No	0	A
243	Avenal	2.70 µg/L	No	35	B
244	Santa Cruz	2.60 µg/L	No	38	F
245	Baldwin Park	2.60 µg/L	No	1	A
246	Reedley	2.60 µg/L	No	12	B-
247	Beaumont	2.50 µg/L	No	2	A-
248	Sunnyvale	2.40 µg/L	No	3	A
249	Azusa	2.40 µg/L	No	2	B+
250	Los Osos	2.35 µg/L	No	0	B+
251	Fremont	2.20 µg/L	No	3	B-
252	Pleasanton	2.20 µg/L	No	3	B-
253	Hesperia	2.20 µg/L	No	2	B
254	Shafter	2.20 µg/L	No	25	A-
255	Cupertino	2.20 µg/L	No	3	A+
256	Redding	2.16 µg/L	No	49	F
257	Ukiah	2.10 µg/L	No	14	C+
258	Milpitas	2.00 µg/L	No	2	A-
259	Sanger	2.00 µg/L	No	16	C
260	Fair Oaks	1.90 µg/L	No	0	B+
261	Santa Rosa	1.80 µg/L	No	177	F
262	Oakley	1.80 µg/L	No	60	D
263	Monrovia	1.80 µg/L	No	0	B+
264	Riverbank	1.80 µg/L	No	75	D
265	Parlier	1.80 µg/L	No	14	A-
266	Concord	1.70 µg/L	No	19	B-
267	Stockton	1.60 µg/L	No	261	F
268	Vallejo	1.60 µg/L	No	6	A
269	San Bernardino	1.50 µg/L	No	192	F
270	Truckee	1.50 µg/L	No	7	A-
271	Carmichael	1.50 µg/L	No	1	B+
272	Livermore	1.40 µg/L	No	53	B
273	Martinez	1.40 µg/L	No	0	A
274	Benicia	1.40 µg/L	No	1	A-
275	El Verano	1.40 µg/L	No	0	B+
276	American Canyon	1.40 µg/L	No	15	A-
277	Napa	1.30 µg/L	No	53	F
278	Oakdale	1.30 µg/L	No	34	C-
279	Oakland	1.20 µg/L	No	13	B
280	Antioch	1.20 µg/L	No	3	A
281	Fairfield	1.10 µg/L	No	7	B-
282	Elk Grove	1.10 µg/L	No	28	C
283	Cottonwood	1.10 µg/L	No	7	B

FAQ

Frequently asked questions about molybdenum in California

Is molybdenum in California tap water harmful?

Molybdenum is an essential trace nutrient at low levels, but chronic exposure above the EPA's 40 µg/L lifetime health advisory has been associated with elevated uric acid, gout-like joint pain, and possible reproductive effects. 11 cities in California exceed the 40 µg/L health advisory.

Where does molybdenum come from?

Molybdenum occurs naturally in groundwater, especially in the western US in regions with shale, copper mining, or molybdenum mining geology. Industrial sources include mining tailings, steel alloy production, and coal ash. Surface-water systems generally have lower molybdenum than groundwater.

How can I remove molybdenum from drinking water?

Reverse osmosis is the most effective household treatment for molybdenum, typically removing 90%+. Anion exchange and some specialty media (like activated alumina) also work. Standard activated carbon filters are NOT effective against molybdenum.

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