Manganese Contamination

Manganese in California Drinking Water

Ranked by max manganese detected (µg/L) · UCMR 4 data (2018–2020) · Data from EPA SDWIS & UCMR

318

Cities Tested

Over SMCL

17%

% Over SMCL

31.5 µg/L

State Avg

▼ 1% vs national

vs National

620

Health Violations

Analysis

Manganese in California: what the data shows

California has 318 cities with manganese data from the EPA's UCMR 4 program (2018–2020). Manganese exceeded the 50 µg/L EPA secondary MCL in 53 of those cities. The state average max detected level is 31.5 µg/L. Manganese occurs naturally in groundwater and surface water. Elevated levels are common in areas with iron-rich geology and in systems that draw from reservoirs with low dissolved oxygen. The secondary MCL of 50 µg/L is based on aesthetic concerns (taste, staining), but health-based guidelines suggest neurological effects at higher concentrations. Emerging research links chronic manganese exposure in drinking water to neurodevelopmental effects in children, including reduced IQ and behavioral issues. Oxidation filtration and water softeners are effective at removing manganese from household water.

Comparison

Cities exceeding 50 µg/L EPA Secondary MCL

California

17%

53 of 318 cities

← ▼ 1% below national rate (better)

National avg

18%

716 of 4016 cities

City Map

Manganese data across California

Each dot is a city with UCMR 4 manganese testing data. Cities where manganese exceeds the 50 µg/L EPA secondary MCL are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by manganese level in California

Highest Manganese levels (µg/L)

All Cities

All California cities ranked by manganese level

#	City	Level	Over SMCL?	Violations	Grade
1	Norco	420.0 µg/L	Over SMCL	39	F
2	San Joaquin	410.0 µg/L	Over SMCL	13	A
3	Citrus Heights	325.0 µg/L	Over SMCL	2	A
4	Jurupa Valley	300.0 µg/L	Over SMCL	62	B
5	Sacramento	290.0 µg/L	Over SMCL	425	F
6	Yucaipa	220.0 µg/L	Over SMCL	9	C+
7	Manteca	210.0 µg/L	Over SMCL	39	B-
8	Newman	210.0 µg/L	Over SMCL	3	A-
9	Davis	200.0 µg/L	Over SMCL	47	B+
10	Soledad	199.0 µg/L	Over SMCL	28	C+
11	Boulder Creek	180.0 µg/L	Over SMCL	119	F
12	Livingston	180.0 µg/L	Over SMCL	29	C-
13	Alpine	180.0 µg/L	Over SMCL	25	C-
14	Goleta	170.0 µg/L	Over SMCL	11	B
15	Wasco	160.0 µg/L	Over SMCL	26	B+
16	Colusa	160.0 µg/L	Over SMCL	6	C-
17	Carmichael	150.0 µg/L	Over SMCL	1	B+
18	Santa Paula	150.0 µg/L	Over SMCL	5	A-
19	Clovis	140.0 µg/L	Over SMCL	221	F
20	Rialto	130.0 µg/L	Over SMCL	6	B+
21	Ceres	130.0 µg/L	Over SMCL	129	F
22	Norwalk	130.0 µg/L	Over SMCL	1	A-
23	Rosemead	120.0 µg/L	Over SMCL	17	C-
24	Vernon	120.0 µg/L	Over SMCL	3	A
25	Blythe	120.0 µg/L	Over SMCL	143	D
26	Gilroy	116.0 µg/L	Over SMCL	28	C+
27	Modesto	110.0 µg/L	Over SMCL	76	D
28	Temecula	110.0 µg/L	Over SMCL	12	C+
29	San Jose	100.0 µg/L	Over SMCL	142	F
30	Rancho Cordova	97.0 µg/L	Over SMCL	115	F
31	Redding	95.0 µg/L	Over SMCL	49	F
32	Compton	92.0 µg/L	Over SMCL	8	B
33	Fresno	86.0 µg/L	Over SMCL	523	F
34	Sonora	85.0 µg/L	Over SMCL	25	D+
35	Lake Elsinore	83.0 µg/L	Over SMCL	8	A
36	Perris	81.0 µg/L	Over SMCL	0	A
37	Stockton	77.0 µg/L	Over SMCL	261	F
38	Camarillo	77.0 µg/L	Over SMCL	4	B
39	Moorpark	77.0 µg/L	Over SMCL	1	A-
40	Tracy	70.0 µg/L	Over SMCL	45	C
41	San Marcos	65.0 µg/L	Over SMCL	27	D
42	Lebec	64.0 µg/L	Over SMCL	42	C
43	Oakley	62.3 µg/L	Over SMCL	60	D
44	Corona	62.0 µg/L	Over SMCL	81	D
45	San Jacinto	62.0 µg/L	Over SMCL	9	B
46	Temescal Valley	60.0 µg/L	Over SMCL	2	A
47	Victorville	58.0 µg/L	Over SMCL	1	B+
48	La Palma	57.8 µg/L	Over SMCL	0	A-
49	Petaluma	57.0 µg/L	Over SMCL	2	B
50	Farmersville	57.0 µg/L	Over SMCL	20	B+
51	Coalinga	56.0 µg/L	Over SMCL	267	D
52	Paradise	53.0 µg/L	Over SMCL	2	A
53	Pacific Grove	51.0 µg/L	Over SMCL	15	B-
54	Cerritos	47.0 µg/L	No	0	B
55	Paso Robles	47.0 µg/L	No	42	F
56	Hawthorne	46.0 µg/L	No	3	B
57	Covina	45.0 µg/L	No	10	B
58	Concord	45.0 µg/L	No	19	B-
59	Highland	45.0 µg/L	No	3	B+
60	Torrance	45.0 µg/L	No	0	A-
61	Buena Park	44.6 µg/L	No	1	B+
62	Marysville	44.0 µg/L	No	11	B+
63	Santa Barbara	42.0 µg/L	No	52	F
64	Cotati	42.0 µg/L	No	9	A-
65	Oakdale	39.0 µg/L	No	34	C-
66	South Gate	38.0 µg/L	No	2	B
67	Montebello	37.0 µg/L	No	5	B
68	American Canyon	37.0 µg/L	No	15	A-
69	Colton	36.0 µg/L	No	5	B-
70	Huntington Park	36.0 µg/L	No	3	B+
71	Watsonville	35.0 µg/L	No	74	F
72	Beaumont	35.0 µg/L	No	2	A-
73	Placerville	34.0 µg/L	No	6	A-
74	Bakersfield	34.0 µg/L	No	690	F
75	La Habra	34.0 µg/L	No	0	A-
76	Downey	33.0 µg/L	No	14	B
77	Grover Beach	32.0 µg/L	No	34	F
78	Fortuna	32.0 µg/L	No	7	B-
79	Lynwood	31.0 µg/L	No	0	B+
80	Sonoma	31.0 µg/L	No	5	B-
81	Pasadena	30.0 µg/L	No	92	F
82	Napa	30.0 µg/L	No	53	F
83	Hanford	30.0 µg/L	No	197	D+
84	Manhattan Beach	28.6 µg/L	No	1	A-
85	San Dimas	28.5 µg/L	No	6	B-
86	Costa Mesa	28.4 µg/L	No	2	A-
87	Auburn	28.0 µg/L	No	8	A
88	Elk Grove	28.0 µg/L	No	28	C
89	Anaheim	27.8 µg/L	No	8	C+
90	Lodi	26.0 µg/L	No	16	C+
91	Rohnert Park	25.9 µg/L	No	21	F
92	Bellflower	25.0 µg/L	No	0	B+
93	La Crescenta	25.0 µg/L	No	3	B+
94	Kerman	25.0 µg/L	No	13	B
95	Westminster	24.4 µg/L	No	2	A-
96	Paramount	24.0 µg/L	No	0	A-
97	Riverside	23.0 µg/L	No	13	C
98	Newhall	23.0 µg/L	No	1	B+
99	Murphys	23.0 µg/L	No	11	B+
100	Laguna Hills	22.0 µg/L	No	1	B+
101	Healdsburg	22.0 µg/L	No	12	B+
102	Huntington Beach	20.1 µg/L	No	5	C-
103	Santa Clara	20.0 µg/L	No	5	B
104	Atwater	20.0 µg/L	No	3	B+
105	Riverbank	20.0 µg/L	No	75	D
106	Coachella	19.0 µg/L	No	11	C-
107	Grass Valley	18.0 µg/L	No	8	A
108	Lemoore	18.0 µg/L	No	112	D
109	Fair Oaks	18.0 µg/L	No	0	B+
110	Fillmore	18.0 µg/L	No	13	B-
111	Milpitas	17.0 µg/L	No	2	A-
112	Menlo Park	16.7 µg/L	No	2	A-
113	Indio	16.0 µg/L	No	12	F
114	Soquel	16.0 µg/L	No	1	A
115	Truckee	15.5 µg/L	No	7	A-
116	Olivehurst	15.4 µg/L	No	2	A
117	La Mesa	15.3 µg/L	No	0	A+
118	Oxnard	15.0 µg/L	No	49	F
119	Madera	15.0 µg/L	No	564	D
120	Salinas	15.0 µg/L	No	639	F
121	Fallbrook	15.0 µg/L	No	3	A
122	San Bruno	15.0 µg/L	No	0	A+
123	Arroyo Grande	15.0 µg/L	No	93	F
124	Grand Terrace	15.0 µg/L	No	1	B
125	Exeter	15.0 µg/L	No	41	B
126	Bell Gardens	15.0 µg/L	No	0	B
127	Orange	14.7 µg/L	No	3	B
128	Patterson	14.5 µg/L	No	35	B+
129	Ventura	14.0 µg/L	No	21	D+
130	South Lake Tahoe	14.0 µg/L	No	15	C
131	Banning	14.0 µg/L	No	15	B-
132	Tulare	13.0 µg/L	No	61	C-
133	Woodland	13.0 µg/L	No	52	F
134	San Fernando	13.0 µg/L	No	1	A+
135	Oakland	12.7 µg/L	No	13	B
136	Corte Madera	12.2 µg/L	No	0	A-
137	Fountain Valley	12.1 µg/L	No	0	A
138	Santa Rosa	12.0 µg/L	No	177	F
139	Porterville	12.0 µg/L	No	74	F
140	Los Banos	12.0 µg/L	No	29	B
141	Chico	12.0 µg/L	No	306	F
142	Three Rivers	12.0 µg/L	No	177	F
143	Santa Cruz	11.0 µg/L	No	38	F
144	California City	11.0 µg/L	No	22	A-
145	Placentia	10.8 µg/L	No	0	B+
146	Chula Vista	10.0 µg/L	No	1	B+
147	Cutten	10.0 µg/L	No	5	A+
148	Santa Monica	9.8 µg/L	No	0	B
149	Half Moon Bay	9.7 µg/L	No	6	A
150	Rio Linda	9.7 µg/L	No	2	A-
151	Hesperia	9.5 µg/L	No	2	B
152	Lakewood	9.4 µg/L	No	1	A-
153	Spring Valley	9.2 µg/L	No	4	B
154	San Luis Obispo	9.2 µg/L	No	27	F
155	Scotts Valley	9.2 µg/L	No	11	B-
156	Fremont	8.9 µg/L	No	3	B-
157	Roseville	8.6 µg/L	No	11	B
158	Valley Center	8.5 µg/L	No	15	F
159	Alhambra	8.4 µg/L	No	7	A-
160	Lincoln	8.4 µg/L	No	6	A-
161	San Diego	8.2 µg/L	No	43	F
162	Hemet	8.1 µg/L	No	31	B-
163	South Pasadena	8.0 µg/L	No	5	A
164	Pico Rivera	7.9 µg/L	No	4	B
165	Hollister	7.9 µg/L	No	132	F
166	Antioch	7.8 µg/L	No	3	A
167	Escondido	7.1 µg/L	No	10	B
168	Mendota	7.0 µg/L	No	3	A
169	Atascadero	6.8 µg/L	No	1	B
170	Millbrae	6.8 µg/L	No	1	A-
171	Burlingame	6.6 µg/L	No	14	A-
172	Novato	6.5 µg/L	No	3	B+
173	Lindsay	6.5 µg/L	No	240	F
174	Whittier	6.4 µg/L	No	4	C+
175	Ridgecrest	6.4 µg/L	No	26	A-
176	Daly City	6.3 µg/L	No	4	A
177	Hayward	6.3 µg/L	No	0	A-
178	Ontario	6.2 µg/L	No	1	B+
179	Montclair	6.2 µg/L	No	0	B+
180	Clearlake	6.2 µg/L	No	5	B+
181	Mcfarland	6.1 µg/L	No	42	C+
182	Belmont	5.9 µg/L	No	3	A+
183	Seal Beach	5.8 µg/L	No	0	A-
184	Fullerton	5.8 µg/L	No	8	B
185	Encinitas	5.7 µg/L	No	55	F
186	Palm Springs	5.7 µg/L	No	16	B
187	Pittsburg	5.3 µg/L	No	0	A
188	Foster City	5.2 µg/L	No	2	A+
189	Arvin	5.2 µg/L	No	81	C+
190	El Segundo	5.2 µg/L	No	0	A-
191	Quartz Hill	5.1 µg/L	No	1	A-
192	Palo Alto	5.0 µg/L	No	8	A-
193	Vacaville	5.0 µg/L	No	26	F
194	Martinez	5.0 µg/L	No	0	A
195	Brentwood	4.9 µg/L	No	91	F
196	Cudahy	4.9 µg/L	No	3	B+
197	Santa Fe Springs	4.9 µg/L	No	1	B+
198	Orangevale	4.9 µg/L	No	0	A
199	Rancho Santa Margarita	4.8 µg/L	No	0	A
200	Sunnyvale	4.8 µg/L	No	3	A
201	Vista	4.8 µg/L	No	0	A-
202	Big Bear City	4.8 µg/L	No	1	A
203	Rancho Cucamonga	4.7 µg/L	No	0	B+
204	Carlsbad	4.7 µg/L	No	0	A+
205	Azusa	4.5 µg/L	No	2	B+
206	Idyllwild	4.5 µg/L	No	10	B
207	Rowland Heights	4.4 µg/L	No	0	B+
208	San Andreas	4.3 µg/L	No	17	B-
209	Laguna Beach	4.1 µg/L	No	2	B
210	Lakeside	4.1 µg/L	No	0	A-
211	Avenal	4.1 µg/L	No	35	B
212	South San Francisco	3.8 µg/L	No	2	A
213	Thousand Oaks	3.7 µg/L	No	1	A
214	Stanford	3.7 µg/L	No	3	A+
215	Long Beach	3.6 µg/L	No	2	C
216	Merced	3.6 µg/L	No	9	C+
217	Hillsborough	3.6 µg/L	No	7	A
218	Upland	3.5 µg/L	No	4	B+
219	Galt	3.5 µg/L	No	27	B+
220	Fontana	3.4 µg/L	No	0	A-
221	Palmdale	3.4 µg/L	No	15	C+
222	San Clemente	3.3 µg/L	No	3	A-
223	Santa Ana	3.3 µg/L	No	8	C
224	Garden Grove	3.3 µg/L	No	2	B
225	Granite Bay	3.2 µg/L	No	43	B-
226	East Palo Alto	3.2 µg/L	No	8	A
227	Greenfield	3.2 µg/L	No	17	B
228	Pala	3.2 µg/L	No	30	C-
229	Felton	3.2 µg/L	No	21	C
230	Mountain View	3.1 µg/L	No	3	A
231	Twentynine Palms	3.1 µg/L	No	70	B+
232	Signal Hill	3.1 µg/L	No	6	B
233	Pomona	3.0 µg/L	No	6	C+
234	Tustin	2.9 µg/L	No	8	B
235	El Monte	2.8 µg/L	No	79	F
236	Walnut	2.8 µg/L	No	1	A-
237	Pauma Valley	2.8 µg/L	No	88	F
238	Loma Linda	2.7 µg/L	No	3	A
239	Irvine	2.7 µg/L	No	84	F
240	Ukiah	2.6 µg/L	No	14	C+
241	Newport Beach	2.5 µg/L	No	4	B+
242	Santee	2.5 µg/L	No	14	B
243	Los Angeles	2.4 µg/L	No	94	F
244	Baldwin Park	2.4 µg/L	No	1	A
245	Lake Forest	2.4 µg/L	No	38	B-
246	Glendale	2.3 µg/L	No	0	A-
247	Apple Valley	2.3 µg/L	No	57	D
248	Oakhurst	2.2 µg/L	No	198	D
249	Red Bluff	2.1 µg/L	No	23	F
250	Calabasas	2.0 µg/L	No	14	A-
251	Imperial	2.0 µg/L	No	36	C+
252	Eureka	2.0 µg/L	No	3	A-
253	Chowchilla	2.0 µg/L	No	25	A-
254	Redwood City	2.0 µg/L	No	10	B+
255	Vallejo	1.9 µg/L	No	6	A
256	Imperial Beach	1.9 µg/L	No	1	A
257	La Habra Heights	1.9 µg/L	No	0	A
258	Fairfield	1.8 µg/L	No	7	B-
259	Chino	1.8 µg/L	No	9	B
260	Chino Hills	1.8 µg/L	No	2	A
261	Marina	1.8 µg/L	No	4	A+
262	Phelan	1.8 µg/L	No	0	B+
263	Fort Bragg	1.8 µg/L	No	4	B
264	Monterey Park	1.7 µg/L	No	1	B
265	Dinuba	1.7 µg/L	No	24	A-
266	Palm Desert	1.6 µg/L	No	12	C+
267	San Bernardin0	1.6 µg/L	No	0	A-
268	Ramona	1.6 µg/L	No	36	C
269	La Verne	1.6 µg/L	No	6	B+
270	Folsom	1.5 µg/L	No	1	A-
271	Redlands	1.5 µg/L	No	2	B
272	Lomita	1.5 µg/L	No	1	A-
273	Lompoc	1.4 µg/L	No	18	C
274	Yucca Valley	1.4 µg/L	No	7	A-
275	Shafter	1.4 µg/L	No	25	A-
276	Corcoran	1.4 µg/L	No	3	A
277	Fort Irwin	1.4 µg/L	No	60	B+
278	Westlake Village	1.4 µg/L	No	8	F
279	Herlong	1.4 µg/L	No	0	A-
280	Anderson	1.4 µg/L	No	14	C-
281	Simi Valley	1.3 µg/L	No	3	A
282	Poway	1.3 µg/L	No	0	A-
283	Beverly Hills	1.3 µg/L	No	18	B
284	Kingsburg	1.3 µg/L	No	17	B
285	Delano	1.2 µg/L	No	67	B
286	Brea	1.2 µg/L	No	0	A
287	Benicia	1.2 µg/L	No	1	A-
288	Lamont	1.2 µg/L	No	40	B+
289	Cupertino	1.2 µg/L	No	3	A+
290	Point Mugu	1.2 µg/L	No	11	A-
291	West Sacramento	1.1 µg/L	No	1	B+
292	Inglewood	1.1 µg/L	No	3	A-
293	Arcadia	1.1 µg/L	No	2	B
294	Turlock	1.1 µg/L	No	16	B-
295	Livermore	1.0 µg/L	No	53	B
296	Santa Maria	1.0 µg/L	No	36	F
297	Mountain House	1.0 µg/L	No	1	A+
298	El Verano	1.0 µg/L	No	0	B+
299	Sanger	1.0 µg/L	No	16	C
300	Oceanside	1.0 µg/L	No	2	A-
301	Camp Pendleton	0.9 µg/L	No	13	B
302	Pleasanton	0.9 µg/L	No	3	B-
303	Yuba City	0.9 µg/L	No	24	A-
304	Glendora	0.9 µg/L	No	0	A-
305	Burbank	0.8 µg/L	No	1	A-
306	Parlier	0.8 µg/L	No	14	A-
307	Discovery Bay	0.8 µg/L	No	3	A+
308	Lathrop	0.8 µg/L	No	44	B
309	Mckinleyville	0.8 µg/L	No	2	A-
310	Nipomo	0.7 µg/L	No	1	A
311	Morro Bay	0.6 µg/L	No	12	A-
312	Adelanto	0.6 µg/L	No	13	C
313	Carpinteria	0.6 µg/L	No	5	A
314	Trabuco Canyon	0.6 µg/L	No	2	A-
315	El Centro	0.6 µg/L	No	14	C-
316	Shasta Lake 4510007	0.5 µg/L	No	1	A+
317	29 Palms	0.5 µg/L	No	3	B
318	Altadena	0.5 µg/L	No	2	B+

FAQ

Frequently asked questions about manganese in California

Is manganese in California tap water harmful?

The EPA secondary MCL for manganese is 50 µg/L, set primarily for aesthetic reasons (taste, color, staining). 53 cities in California exceed the secondary MCL. However, emerging research links chronic manganese exposure above 50–100 µg/L to neurodevelopmental effects in children, including reduced IQ.

How can I remove manganese from my drinking water?

Oxidation filtration (such as greensand or birm filters) is the most common and effective method for removing manganese from well water. Water softeners using ion exchange also work well. Standard carbon filters provide limited manganese removal. If your water has a metallic taste or brown/black discoloration, manganese may be the cause.

What causes high manganese in California water?

Manganese occurs naturally in groundwater and surface water, particularly in areas with iron-rich geology. Low dissolved oxygen conditions (common in deep wells and reservoir bottom waters) increase manganese solubility. Industrial sources include mining, steel production, and battery manufacturing. Seasonal changes in reservoir water chemistry can cause manganese spikes.

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