Manganese Contamination

Manganese in California Drinking Water

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

320

Cities Tested

Over SMCL

17%

% Over SMCL

31.3 µg/L

State Avg

▼ 1% vs national

vs National

624

Health Violations

Analysis

Manganese in California: what the data shows

California has 320 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 31.3 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 320 cities

← ▼ 1% below national rate (better)

National avg

18%

729 of 4068 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	Bakersfield	34.0 µg/L	No	690	F
74	Placerville	34.0 µg/L	No	6	A-
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	Morgan Hill	15.0 µg/L	No	92	F
123	San Bruno	15.0 µg/L	No	0	A+
124	Arroyo Grande	15.0 µg/L	No	93	F
125	Grand Terrace	15.0 µg/L	No	1	B
126	Exeter	15.0 µg/L	No	41	B
127	Bell Gardens	15.0 µg/L	No	0	B
128	Orange	14.7 µg/L	No	3	B
129	Patterson	14.5 µg/L	No	35	B+
130	Ventura	14.0 µg/L	No	21	D+
131	South Lake Tahoe	14.0 µg/L	No	15	C
132	Banning	14.0 µg/L	No	15	B-
133	Tulare	13.0 µg/L	No	61	C-
134	Woodland	13.0 µg/L	No	52	F
135	San Fernando	13.0 µg/L	No	1	A+
136	Oakland	12.7 µg/L	No	13	B
137	Corte Madera	12.2 µg/L	No	0	A-
138	Fountain Valley	12.1 µg/L	No	0	A
139	Santa Rosa	12.0 µg/L	No	177	F
140	Porterville	12.0 µg/L	No	74	F
141	Los Banos	12.0 µg/L	No	29	B
142	Chico	12.0 µg/L	No	306	F
143	Three Rivers	12.0 µg/L	No	177	F
144	Santa Cruz	11.0 µg/L	No	38	F
145	California City	11.0 µg/L	No	22	A-
146	Placentia	10.8 µg/L	No	0	B+
147	Chula Vista	10.0 µg/L	No	1	B+
148	Cutten	10.0 µg/L	No	5	A+
149	Santa Monica	9.8 µg/L	No	0	B
150	Half Moon Bay	9.7 µg/L	No	6	A
151	Rio Linda	9.7 µg/L	No	2	A-
152	Hesperia	9.5 µg/L	No	2	B
153	Lakewood	9.4 µg/L	No	1	A-
154	Spring Valley	9.2 µg/L	No	4	B
155	San Luis Obispo	9.2 µg/L	No	27	F
156	Scotts Valley	9.2 µg/L	No	11	B-
157	Fremont	8.9 µg/L	No	3	B-
158	Roseville	8.6 µg/L	No	11	B
159	Valley Center	8.5 µg/L	No	15	F
160	Alhambra	8.4 µg/L	No	7	A-
161	Lincoln	8.4 µg/L	No	6	A-
162	San Diego	8.2 µg/L	No	43	F
163	Hemet	8.1 µg/L	No	31	B-
164	South Pasadena	8.0 µg/L	No	5	A
165	Pico Rivera	7.9 µg/L	No	4	B
166	Hollister	7.9 µg/L	No	132	F
167	Antioch	7.8 µg/L	No	3	A
168	Escondido	7.1 µg/L	No	10	B
169	Mendota	7.0 µg/L	No	3	A
170	Atascadero	6.8 µg/L	No	1	B
171	Millbrae	6.8 µg/L	No	1	A-
172	Burlingame	6.6 µg/L	No	14	A-
173	Novato	6.5 µg/L	No	3	B+
174	Lindsay	6.5 µg/L	No	240	F
175	Whittier	6.4 µg/L	No	4	C+
176	Ridgecrest	6.4 µg/L	No	26	A-
177	Daly City	6.3 µg/L	No	4	A
178	Hayward	6.3 µg/L	No	0	A-
179	Ontario	6.2 µg/L	No	1	B+
180	Montclair	6.2 µg/L	No	0	B+
181	Clearlake	6.2 µg/L	No	5	B+
182	Mcfarland	6.1 µg/L	No	42	C+
183	Belmont	5.9 µg/L	No	3	A+
184	Seal Beach	5.8 µg/L	No	0	A-
185	Fullerton	5.8 µg/L	No	8	B
186	Encinitas	5.7 µg/L	No	55	F
187	Palm Springs	5.7 µg/L	No	16	B
188	Pittsburg	5.3 µg/L	No	0	A
189	Foster City	5.2 µg/L	No	2	A+
190	Arvin	5.2 µg/L	No	81	C+
191	El Segundo	5.2 µg/L	No	0	A-
192	Quartz Hill	5.1 µg/L	No	1	A-
193	Vacaville	5.0 µg/L	No	26	F
194	Palo Alto	5.0 µg/L	No	8	A-
195	Martinez	5.0 µg/L	No	0	A
196	Brentwood	4.9 µg/L	No	91	F
197	Santa Fe Springs	4.9 µg/L	No	1	B+
198	Cudahy	4.9 µg/L	No	3	B+
199	Orangevale	4.9 µg/L	No	0	A
200	Rancho Santa Margarita	4.8 µg/L	No	0	A
201	Sunnyvale	4.8 µg/L	No	3	A
202	Vista	4.8 µg/L	No	0	A-
203	Big Bear City	4.8 µg/L	No	1	A
204	Rancho Cucamonga	4.7 µg/L	No	0	B+
205	Carlsbad	4.7 µg/L	No	0	A+
206	Azusa	4.5 µg/L	No	2	B+
207	Idyllwild	4.5 µg/L	No	10	B
208	Rowland Heights	4.4 µg/L	No	0	B+
209	San Andreas	4.3 µg/L	No	17	B-
210	Laguna Beach	4.1 µg/L	No	2	B
211	San Juan Capistrano	4.1 µg/L	No	5	B+
212	Lakeside	4.1 µg/L	No	0	A-
213	Avenal	4.1 µg/L	No	35	B
214	South San Francisco	3.8 µg/L	No	2	A
215	Thousand Oaks	3.7 µg/L	No	1	A
216	Stanford	3.7 µg/L	No	3	A+
217	Long Beach	3.6 µg/L	No	2	C
218	Merced	3.6 µg/L	No	9	C+
219	Hillsborough	3.6 µg/L	No	7	A
220	Upland	3.5 µg/L	No	4	B+
221	Galt	3.5 µg/L	No	27	B+
222	Fontana	3.4 µg/L	No	0	A-
223	Palmdale	3.4 µg/L	No	15	C+
224	San Clemente	3.3 µg/L	No	3	A-
225	Santa Ana	3.3 µg/L	No	8	C
226	Garden Grove	3.3 µg/L	No	2	B
227	Granite Bay	3.2 µg/L	No	43	B-
228	East Palo Alto	3.2 µg/L	No	8	A
229	Greenfield	3.2 µg/L	No	17	B
230	Pala	3.2 µg/L	No	30	C-
231	Felton	3.2 µg/L	No	21	C
232	Mountain View	3.1 µg/L	No	3	A
233	Twentynine Palms	3.1 µg/L	No	70	B+
234	Signal Hill	3.1 µg/L	No	6	B
235	Pomona	3.0 µg/L	No	6	C+
236	Tustin	2.9 µg/L	No	8	B
237	El Monte	2.8 µg/L	No	79	F
238	Walnut	2.8 µg/L	No	1	A-
239	Pauma Valley	2.8 µg/L	No	88	F
240	Loma Linda	2.7 µg/L	No	3	A
241	Irvine	2.7 µg/L	No	84	F
242	Ukiah	2.6 µg/L	No	14	C+
243	Newport Beach	2.5 µg/L	No	4	B+
244	Santee	2.5 µg/L	No	14	B
245	Los Angeles	2.4 µg/L	No	94	F
246	Baldwin Park	2.4 µg/L	No	1	A
247	Lake Forest	2.4 µg/L	No	38	B-
248	Glendale	2.3 µg/L	No	0	A-
249	Apple Valley	2.3 µg/L	No	57	D
250	Oakhurst	2.2 µg/L	No	198	D
251	Red Bluff	2.1 µg/L	No	23	F
252	Calabasas	2.0 µg/L	No	14	A-
253	Imperial	2.0 µg/L	No	36	C+
254	Eureka	2.0 µg/L	No	3	A-
255	Chowchilla	2.0 µg/L	No	25	A-
256	Redwood City	2.0 µg/L	No	10	B+
257	Vallejo	1.9 µg/L	No	6	A
258	Imperial Beach	1.9 µg/L	No	1	A
259	La Habra Heights	1.9 µg/L	No	0	A
260	Fairfield	1.8 µg/L	No	7	B-
261	Chino	1.8 µg/L	No	9	B
262	Chino Hills	1.8 µg/L	No	2	A
263	Marina	1.8 µg/L	No	4	A+
264	Phelan	1.8 µg/L	No	0	B+
265	Fort Bragg	1.8 µg/L	No	4	B
266	Monterey Park	1.7 µg/L	No	1	B
267	Dinuba	1.7 µg/L	No	24	A-
268	Palm Desert	1.6 µg/L	No	12	C+
269	San Bernardin0	1.6 µg/L	No	0	A-
270	Ramona	1.6 µg/L	No	36	C
271	La Verne	1.6 µg/L	No	6	B+
272	Folsom	1.5 µg/L	No	1	A-
273	Redlands	1.5 µg/L	No	2	B
274	Lomita	1.5 µg/L	No	1	A-
275	Lompoc	1.4 µg/L	No	18	C
276	Yucca Valley	1.4 µg/L	No	7	A-
277	Shafter	1.4 µg/L	No	25	A-
278	Corcoran	1.4 µg/L	No	3	A
279	Fort Irwin	1.4 µg/L	No	60	B+
280	Westlake Village	1.4 µg/L	No	8	F
281	Herlong	1.4 µg/L	No	0	A-
282	Anderson	1.4 µg/L	No	14	C-
283	Simi Valley	1.3 µg/L	No	3	A
284	Poway	1.3 µg/L	No	0	A-
285	Beverly Hills	1.3 µg/L	No	18	B
286	Kingsburg	1.3 µg/L	No	17	B
287	Delano	1.2 µg/L	No	67	B
288	Brea	1.2 µg/L	No	0	A
289	Benicia	1.2 µg/L	No	1	A-
290	Lamont	1.2 µg/L	No	40	B+
291	Cupertino	1.2 µg/L	No	3	A+
292	Point Mugu	1.2 µg/L	No	11	A-
293	West Sacramento	1.1 µg/L	No	1	B+
294	Inglewood	1.1 µg/L	No	3	A-
295	Arcadia	1.1 µg/L	No	2	B
296	Turlock	1.1 µg/L	No	16	B-
297	Livermore	1.0 µg/L	No	53	B
298	Santa Maria	1.0 µg/L	No	36	F
299	Mountain House	1.0 µg/L	No	1	A+
300	El Verano	1.0 µg/L	No	0	B+
301	Sanger	1.0 µg/L	No	16	C
302	Oceanside	1.0 µg/L	No	2	A-
303	Camp Pendleton	0.9 µg/L	No	13	B
304	Pleasanton	0.9 µg/L	No	3	B-
305	Yuba City	0.9 µg/L	No	24	A-
306	Glendora	0.9 µg/L	No	0	A-
307	Burbank	0.8 µg/L	No	1	A-
308	Parlier	0.8 µg/L	No	14	A-
309	Discovery Bay	0.8 µg/L	No	3	A+
310	Lathrop	0.8 µg/L	No	44	B
311	Mckinleyville	0.8 µg/L	No	2	A-
312	Nipomo	0.7 µg/L	No	1	A
313	Morro Bay	0.6 µg/L	No	12	A-
314	Adelanto	0.6 µg/L	No	13	C
315	Carpinteria	0.6 µg/L	No	5	A
316	Trabuco Canyon	0.6 µg/L	No	2	A-
317	El Centro	0.6 µg/L	No	14	C-
318	Shasta Lake 4510007	0.5 µg/L	No	1	A+
319	29 Palms	0.5 µg/L	No	3	B
320	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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