Molybdenum Contamination

Molybdenum in California Drinking Water

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

285

Cities Tested

Over HA

% Over HA

11.31 µg/L

State Avg

▲ 2% vs national

vs National

624

Health Violations

Analysis

Molybdenum in California: what the data shows

California has 285 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 11.31 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 285 cities

→ ▲ 2% above national rate (worse)

National avg

36 of 2228 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	San Juan Capistrano	5.50 µg/L	No	5	B+
146	Newport Beach	5.40 µg/L	No	4	B+
147	Beverly Hills	5.40 µg/L	No	18	B
148	San Luis Obispo	5.30 µg/L	No	27	F
149	Santa Fe Springs	5.20 µg/L	No	1	B+
150	Lomita	5.20 µg/L	No	1	A-
151	Trabuco Canyon	5.20 µg/L	No	2	A-
152	Edwards Afb	5.20 µg/L	No	8	A-
153	Rancho Santa Margarita	5.10 µg/L	No	0	A
154	Walnut	5.10 µg/L	No	1	A-
155	Inglewood	5.10 µg/L	No	3	A-
156	Laguna Beach	5.10 µg/L	No	2	B
157	Lake Forest	5.10 µg/L	No	38	B-
158	San Bernardin0	5.00 µg/L	No	0	A-
159	Santa Clara	5.00 µg/L	No	5	B
160	Lakewood	5.00 µg/L	No	1	A-
161	Porterville	5.00 µg/L	No	74	F
162	Fallbrook	5.00 µg/L	No	3	A
163	Lindsay	5.00 µg/L	No	240	F
164	Rialto	4.90 µg/L	No	6	B+
165	La Crescenta	4.90 µg/L	No	3	B+
166	Coalinga	4.90 µg/L	No	267	D
167	Fontana	4.80 µg/L	No	0	A-
168	Manhattan Beach	4.80 µg/L	No	1	A-
169	Rancho Santa Fe	4.80 µg/L	No	3	A-
170	San Diego	4.70 µg/L	No	43	F
171	Riverside	4.70 µg/L	No	13	C
172	Oceanside	4.70 µg/L	No	2	A-
173	Laguna Hills	4.70 µg/L	No	1	B+
174	Torrance	4.70 µg/L	No	0	A-
175	Montclair	4.70 µg/L	No	0	B+
176	Valley Center	4.70 µg/L	No	15	F
177	Signal Hill	4.70 µg/L	No	6	B
178	San Marcos	4.60 µg/L	No	27	D
179	Watsonville	4.60 µg/L	No	74	F
180	Brea	4.60 µg/L	No	0	A
181	Ramona	4.60 µg/L	No	36	C
182	Clovis	4.50 µg/L	No	221	F
183	Encinitas	4.50 µg/L	No	55	F
184	Calabasas	4.50 µg/L	No	14	A-
185	Hollister	4.50 µg/L	No	132	F
186	Temescal Valley	4.50 µg/L	No	2	A
187	El Segundo	4.50 µg/L	No	0	A-
188	Spring Valley	4.40 µg/L	No	4	B
189	Palmdale	4.40 µg/L	No	15	C+
190	Adelanto	4.40 µg/L	No	13	C
191	Escondido	4.31 µg/L	No	10	B
192	La Mesa	4.30 µg/L	No	0	A+
193	Carlsbad	4.30 µg/L	No	0	A+
194	Rowland Heights	4.30 µg/L	No	0	B+
195	Galt	4.30 µg/L	No	27	B+
196	Blythe	4.30 µg/L	No	143	D
197	Sierra Madre	4.30 µg/L	No	5	A
198	Dinuba	4.30 µg/L	No	24	A-
199	Tracy	4.20 µg/L	No	45	C
200	Lakeside	4.20 µg/L	No	0	A-
201	Phelan	4.20 µg/L	No	0	B+
202	Ripon	4.20 µg/L	No	10	A-
203	Vista	4.10 µg/L	No	0	A-
204	Imperial Beach	4.10 µg/L	No	1	A
205	Davis	4.00 µg/L	No	47	B+
206	Santa Monica	4.00 µg/L	No	0	B
207	Poway	4.00 µg/L	No	0	A-
208	San Fernando	4.00 µg/L	No	1	A+
209	Taft	4.00 µg/L	No	0	A-
210	Kerman	4.00 µg/L	No	13	B
211	Discovery Bay	4.00 µg/L	No	3	A+
212	Bell Gardens	4.00 µg/L	No	0	B
213	Pomona	3.90 µg/L	No	6	C+
214	Santee	3.90 µg/L	No	14	B
215	Upland	3.90 µg/L	No	4	B+
216	Chino Hills	3.90 µg/L	No	2	A
217	Pico Rivera	3.80 µg/L	No	4	B
218	Apple Valley	3.60 µg/L	No	57	D
219	Atwater	3.60 µg/L	No	3	B+
220	Woodland	3.50 µg/L	No	52	F
221	Rohnert Park	3.50 µg/L	No	21	F
222	Oak View	3.50 µg/L	No	12	B+
223	Vacaville	3.40 µg/L	No	26	F
224	Patterson	3.20 µg/L	No	35	B+
225	Chowchilla	3.20 µg/L	No	25	A-
226	Firebaugh	3.20 µg/L	No	89	D
227	Lodi	3.10 µg/L	No	16	C+
228	Pittsburg	3.10 µg/L	No	0	A
229	Bellflower	3.10 µg/L	No	0	B+
230	Soquel	3.10 µg/L	No	1	A
231	Lathrop	3.10 µg/L	No	44	B
232	Sonoma	3.10 µg/L	No	5	B-
233	Newman	3.10 µg/L	No	3	A-
234	Whittier	3.00 µg/L	No	4	C+
235	Wasco	3.00 µg/L	No	26	B+
236	Morro Bay	3.00 µg/L	No	12	A-
237	Merced	2.90 µg/L	No	9	C+
238	Mountain View	2.90 µg/L	No	3	A
239	Petaluma	2.90 µg/L	No	2	B
240	Manteca	2.80 µg/L	No	39	B-
241	Montebello	2.80 µg/L	No	5	B
242	Half Moon Bay	2.80 µg/L	No	6	A
243	Kirkwood	2.80 µg/L	No	0	A
244	Avenal	2.70 µg/L	No	35	B
245	Santa Cruz	2.60 µg/L	No	38	F
246	Baldwin Park	2.60 µg/L	No	1	A
247	Reedley	2.60 µg/L	No	12	B-
248	Beaumont	2.50 µg/L	No	2	A-
249	Sunnyvale	2.40 µg/L	No	3	A
250	Azusa	2.40 µg/L	No	2	B+
251	Los Osos	2.35 µg/L	No	0	B+
252	Fremont	2.20 µg/L	No	3	B-
253	Pleasanton	2.20 µg/L	No	3	B-
254	Hesperia	2.20 µg/L	No	2	B
255	Shafter	2.20 µg/L	No	25	A-
256	Cupertino	2.20 µg/L	No	3	A+
257	Redding	2.16 µg/L	No	49	F
258	Ukiah	2.10 µg/L	No	14	C+
259	Milpitas	2.00 µg/L	No	2	A-
260	Sanger	2.00 µg/L	No	16	C
261	Fair Oaks	1.90 µg/L	No	0	B+
262	Santa Rosa	1.80 µg/L	No	177	F
263	Oakley	1.80 µg/L	No	60	D
264	Monrovia	1.80 µg/L	No	0	B+
265	Riverbank	1.80 µg/L	No	75	D
266	Parlier	1.80 µg/L	No	14	A-
267	Concord	1.70 µg/L	No	19	B-
268	Stockton	1.60 µg/L	No	261	F
269	Vallejo	1.60 µg/L	No	6	A
270	San Bernardino	1.50 µg/L	No	192	F
271	Truckee	1.50 µg/L	No	7	A-
272	Carmichael	1.50 µg/L	No	1	B+
273	Livermore	1.40 µg/L	No	53	B
274	Martinez	1.40 µg/L	No	0	A
275	Benicia	1.40 µg/L	No	1	A-
276	El Verano	1.40 µg/L	No	0	B+
277	American Canyon	1.40 µg/L	No	15	A-
278	Napa	1.30 µg/L	No	53	F
279	Oakdale	1.30 µg/L	No	34	C-
280	Oakland	1.20 µg/L	No	13	B
281	Antioch	1.20 µg/L	No	3	A
282	Fairfield	1.10 µg/L	No	7	B-
283	Morgan Hill	1.10 µg/L	No	92	F
284	Elk Grove	1.10 µg/L	No	28	C
285	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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