Lithium Contamination

Lithium in California Drinking Water

Ranked by max lithium detected (µg/L) · UCMR 5 data (2023–2025) · Data from EPA SDWIS & UCMR

248

Cities Tested

248

Detected

100%

% Detected

44.8 µg/L

State Avg

▼ 0% vs national

vs National

620

Health Violations

Analysis

Lithium in California: what the data shows

California has 248 cities with lithium data from the EPA's UCMR 5 program (2023–2025). Lithium was detected in 248 of those cities. There is currently no federal MCL or health advisory for lithium — the state average max detected level is 44.8 µg/L. Nationally, lithium is detected in roughly 28% of sampled water systems. Lithium occurs naturally in groundwater, particularly in arid western states, and is concentrated in some surface waters near industrial discharge or geothermal sources. UCMR 5 added lithium monitoring in 2023, providing the first systematic national snapshot of public-water lithium levels. At therapeutic doses (administered as a medication), lithium is used to treat bipolar disorder. Chronic low-dose exposure from drinking water has been associated in some studies with effects on thyroid function and possibly mood. The most protective state guidance value is around 60 µg/L. Reverse osmosis and ion exchange are effective removal methods.

Comparison

Cities exceeding No federal MCL or HA

California

100%

248 of 248 cities

← = Exactly at national rate

National avg

100%

2776 of 2776 cities

City Map

Lithium data across California

Each dot is a city with UCMR 5 lithium testing data. Detected cities are shown — there is no federal limit, though some states use 60 µg/L as a screening level. Size reflects population served.

Worst Offenders

Top 10 cities by lithium level in California

Highest Lithium levels (µg/L)

All Cities

All California cities ranked by lithium level

#	City	Level	Detected?	Violations	Grade
1	Sacramento	474.0 µg/L	Detected	425	F
2	Blythe	159.0 µg/L	Detected	143	D
3	Mammoth Lakes	153.0 µg/L	Detected	24	B
4	Ventura	140.0 µg/L	Detected	21	D+
5	Mariposa	113.0 µg/L	Detected	71	C
6	Needles	108.0 µg/L	Detected	45	F
7	Coarsegold	106.0 µg/L	Detected	24	C-
8	Running Springs	106.0 µg/L	Detected	3	B
9	China Lake	104.0 µg/L	Detected	8	A
10	Brentwood	102.0 µg/L	Detected	91	F
11	Los Angeles	100.0 µg/L	Detected	94	F
12	Santa Rosa	96.0 µg/L	Detected	177	F
13	Rosemead	91.9 µg/L	Detected	17	C-
14	Downey	88.6 µg/L	Detected	14	B
15	Soquel	88.0 µg/L	Detected	1	A
16	San Dimas	87.0 µg/L	Detected	6	B-
17	San Jose	81.3 µg/L	Detected	142	F
18	Holtville	81.1 µg/L	Detected	66	B-
19	Barstow	79.0 µg/L	Detected	66	F
20	Imperial	78.8 µg/L	Detected	36	C+
21	Camarillo	78.5 µg/L	Detected	4	B
22	Oroville	76.0 µg/L	Detected	7	C-
23	St. Helena	75.0 µg/L	Detected	29	C+
24	Heber	74.4 µg/L	Detected	15	A
25	Ojai	74.1 µg/L	Detected	35	C-
26	Patterson	74.0 µg/L	Detected	35	B+
27	Lompoc	72.2 µg/L	Detected	18	C
28	Fillmore	70.0 µg/L	Detected	13	B-
29	Scotts Valley	69.5 µg/L	Detected	11	B-
30	El Centro	69.0 µg/L	Detected	14	C-
31	Santa Barbara	67.9 µg/L	Detected	52	F
32	Lomita	67.4 µg/L	Detected	1	A-
33	Irvine	67.2 µg/L	Detected	84	F
34	Mojave	66.5 µg/L	Detected	114	D
35	Tracy	66.2 µg/L	Detected	45	C
36	Trabuco Canyon	65.9 µg/L	Detected	2	A-
37	Montebello	65.7 µg/L	Detected	5	B
38	La Canada Flintridge	65.7 µg/L	Detected	4	A
39	Imperial Beach	65.5 µg/L	Detected	1	A
40	Salinas	65.1 µg/L	Detected	639	F
41	San Diego	65.0 µg/L	Detected	43	F
42	Pasadena	64.2 µg/L	Detected	92	F
43	Roseville	62.6 µg/L	Detected	11	B
44	Santa Ynez	62.2 µg/L	Detected	14	A-
45	Brawley	62.0 µg/L	Detected	5	A-
46	Inglewood	61.4 µg/L	Detected	3	A-
47	Anaheim	61.0 µg/L	Detected	8	C+
48	Cerritos	61.0 µg/L	Detected	0	B
49	Bell Gardens	61.0 µg/L	Detected	0	B
50	Glendale	60.4 µg/L	Detected	0	A-
51	Ridgecrest	60.3 µg/L	Detected	26	A-
52	San Clemente	60.0 µg/L	Detected	3	A-
53	Arroyo Grande	60.0 µg/L	Detected	93	F
54	Santa Fe Springs	60.0 µg/L	Detected	1	B+
55	Calexico	59.0 µg/L	Detected	7	B-
56	Norwalk	59.0 µg/L	Detected	1	A-
57	Alhambra	58.0 µg/L	Detected	7	A-
58	Torrance	58.0 µg/L	Detected	0	A-
59	Compton	58.0 µg/L	Detected	8	B
60	Signal Hill	58.0 µg/L	Detected	6	B
61	Pacific Grove	57.5 µg/L	Detected	15	B-
62	La Habra	56.3 µg/L	Detected	0	A-
63	Highland	56.2 µg/L	Detected	3	B+
64	Brea	56.2 µg/L	Detected	0	A
65	Paramount	56.0 µg/L	Detected	0	A-
66	Vernon	56.0 µg/L	Detected	3	A
67	Corona	55.1 µg/L	Detected	81	D
68	Vandenberg Sfb	55.1 µg/L	Detected	8	A
69	Greenfield	54.3 µg/L	Detected	17	B
70	Encinitas	54.1 µg/L	Detected	55	F
71	Long Beach	54.0 µg/L	Detected	2	C
72	Covina	54.0 µg/L	Detected	10	B
73	Santa Cruz	54.0 µg/L	Detected	38	F
74	Huntington Park	54.0 µg/L	Detected	3	B+
75	Altadena	53.6 µg/L	Detected	2	B+
76	Goleta	53.5 µg/L	Detected	11	B
77	Newhall	53.1 µg/L	Detected	1	B+
78	La Canada	53.0 µg/L	Detected	5	B
79	Avalon	52.9 µg/L	Detected	1	A-
80	Carlsbad	52.5 µg/L	Detected	0	A+
81	Vista	52.0 µg/L	Detected	0	A-
82	San Marcos	52.0 µg/L	Detected	27	D
83	Fallbrook	51.6 µg/L	Detected	3	A
84	Manhattan Beach	51.4 µg/L	Detected	1	A-
85	Hawthorne	51.3 µg/L	Detected	3	B
86	Rancho Santa Margarita	50.1 µg/L	Detected	0	A
87	Walnut	50.1 µg/L	Detected	1	A-
88	Temecula	50.0 µg/L	Detected	12	C+
89	Murphys	50.0 µg/L	Detected	11	B+
90	California City	49.7 µg/L	Detected	22	A-
91	Lynwood	49.0 µg/L	Detected	0	B+
92	Poway	48.7 µg/L	Detected	0	A-
93	Firebaugh	48.6 µg/L	Detected	89	D
94	La Habra Heights	48.5 µg/L	Detected	0	A
95	Del Mar	48.1 µg/L	Detected	3	B-
96	Laguna Beach	48.0 µg/L	Detected	2	B
97	Rowland Heights	48.0 µg/L	Detected	0	B+
98	Santee	47.0 µg/L	Detected	14	B
99	Beverly Hills	47.0 µg/L	Detected	18	B
100	Rosamond	46.9 µg/L	Detected	205	F
101	Twentynine Palms	46.5 µg/L	Detected	70	B+
102	Paso Robles	46.2 µg/L	Detected	42	F
103	Woodland	46.1 µg/L	Detected	52	F
104	Castaic	46.1 µg/L	Detected	17	F
105	Santa Paula	46.0 µg/L	Detected	5	A-
106	Lake Forest	45.0 µg/L	Detected	38	B-
107	Vacaville	45.0 µg/L	Detected	26	F
108	La Crescenta	45.0 µg/L	Detected	3	B+
109	Oxnard	44.4 µg/L	Detected	49	F
110	San Bernardino	44.0 µg/L	Detected	192	F
111	El Segundo	44.0 µg/L	Detected	0	A-
112	Los Banos	43.6 µg/L	Detected	29	B
113	Escondido	43.0 µg/L	Detected	10	B
114	Laguna Hills	43.0 µg/L	Detected	1	B+
115	Colusa	41.9 µg/L	Detected	6	C-
116	Solvang	41.1 µg/L	Detected	6	B
117	Cotati	41.0 µg/L	Detected	9	A-
118	Marina	40.9 µg/L	Detected	4	A+
119	Borrego Springs	40.8 µg/L	Detected	2	A+
120	Dixon	40.5 µg/L	Detected	2	A
121	Castroville	40.2 µg/L	Detected	86	D+
122	San Bruno	40.0 µg/L	Detected	0	A+
123	Valley Center	40.0 µg/L	Detected	15	F
124	Sonoma	40.0 µg/L	Detected	5	B-
125	Newman	40.0 µg/L	Detected	3	A-
126	Tehachapi	39.9 µg/L	Detected	96	F
127	Rancho Santa Fe	39.8 µg/L	Detected	3	A-
128	Perris	39.0 µg/L	Detected	0	A
129	Lake Elsinore	39.0 µg/L	Detected	8	A
130	Rohnert Park	39.0 µg/L	Detected	21	F
131	Gustine	39.0 µg/L	Detected	4	B+
132	Paicines	38.7 µg/L	Detected	9	B-
133	Santa Ana	38.5 µg/L	Detected	8	C
134	Redding	38.4 µg/L	Detected	49	F
135	Oceanside	38.0 µg/L	Detected	2	A-
136	Tustin	37.9 µg/L	Detected	8	B
137	Davis	37.3 µg/L	Detected	47	B+
138	Carpinteria	37.3 µg/L	Detected	5	A
139	Costa Mesa	37.3 µg/L	Detected	2	A-
140	Riverside	37.0 µg/L	Detected	13	C
141	Oak View	37.0 µg/L	Detected	12	B+
142	Camp Pendleton	36.9 µg/L	Detected	13	B
143	La Palma	36.7 µg/L	Detected	0	A-
144	Westminster	36.6 µg/L	Detected	2	A-
145	Buena Park	36.5 µg/L	Detected	1	B+
146	Placentia	36.4 µg/L	Detected	0	B+
147	Newport Beach	36.2 µg/L	Detected	4	B+
148	Fountain Valley	36.1 µg/L	Detected	0	A
149	Huntington Beach	36.0 µg/L	Detected	5	C-
150	Ramona	36.0 µg/L	Detected	36	C
151	El Verano	36.0 µg/L	Detected	0	B+
152	Norco	35.9 µg/L	Detected	39	F
153	Rancho Cordova	35.5 µg/L	Detected	115	F
154	San Joaquin	35.5 µg/L	Detected	13	A
155	Seal Beach	35.5 µg/L	Detected	0	A-
156	Orange	35.3 µg/L	Detected	3	B
157	Fullerton	35.0 µg/L	Detected	8	B
158	Santa Monica	34.8 µg/L	Detected	0	B
159	Garden Grove	34.7 µg/L	Detected	2	B
160	Discovery Bay	34.0 µg/L	Detected	3	A+
161	Gonzales	33.4 µg/L	Detected	53	F
162	Williams	32.3 µg/L	Detected	3	A+
163	Truckee	32.0 µg/L	Detected	7	A-
164	Soledad	32.0 µg/L	Detected	28	C+
165	Boulder Creek	32.0 µg/L	Detected	119	F
166	Lakeside	31.0 µg/L	Detected	0	A-
167	Port Hueneme	29.7 µg/L	Detected	0	B+
168	Hollister	29.0 µg/L	Detected	132	F
169	Spring Valley	28.9 µg/L	Detected	4	B
170	Quartz Hill	28.1 µg/L	Detected	1	A-
171	Chula Vista	28.0 µg/L	Detected	1	B+
172	Watsonville	27.3 µg/L	Detected	74	F
173	Templeton	27.3 µg/L	Detected	1	A
174	Buellton	27.3 µg/L	Detected	2	B+
175	Villa Park	27.1 µg/L	Detected	1	A-
176	Winters	27.0 µg/L	Detected	1	A+
177	South Lake Tahoe	26.3 µg/L	Detected	15	C
178	La Mesa	26.0 µg/L	Detected	0	A+
179	Kelseyville	26.0 µg/L	Detected	36	B-
180	Clearlake	25.0 µg/L	Detected	5	B+
181	Wildomar	24.0 µg/L	Detected	11	A-
182	Susanville	23.9 µg/L	Detected	34	A-
183	Yucca Valley	23.0 µg/L	Detected	7	A-
184	Nuevo	23.0 µg/L	Detected	6	B+
185	Pittsburg	22.9 µg/L	Detected	0	A
186	Apple Valley	22.9 µg/L	Detected	57	D
187	Crestline	22.2 µg/L	Detected	9	C+
188	Maywood	21.8 µg/L	Detected	3	A-
189	Alpine	21.4 µg/L	Detected	25	C-
190	Delano	21.1 µg/L	Detected	67	B
191	Modesto	21.0 µg/L	Detected	76	D
192	Edwards Afb	20.8 µg/L	Detected	8	A-
193	Atascadero	20.7 µg/L	Detected	1	B
194	Bakersfield	20.6 µg/L	Detected	690	F
195	Aptos	20.3 µg/L	Detected	9	A-
196	Redlands	20.0 µg/L	Detected	2	B
197	El Cajon	20.0 µg/L	Detected	24	B+
198	Arnold	20.0 µg/L	Detected	2	B-
199	Rio Vista	19.0 µg/L	Detected	3	A+
200	Kirkwood	19.0 µg/L	Detected	0	A
201	Citrus Heights	18.0 µg/L	Detected	2	A
202	Lakeport	18.0 µg/L	Detected	14	C-
203	Palm Desert	17.7 µg/L	Detected	12	C+
204	Hidden Valley Lake	17.3 µg/L	Detected	1	A+
205	Pleasanton	16.8 µg/L	Detected	3	B-
206	Victorville	16.5 µg/L	Detected	1	B+
207	Sebastopol	16.3 µg/L	Detected	18	B-
208	Hemet	16.2 µg/L	Detected	31	B-
209	Los Osos	16.1 µg/L	Detected	0	B+
210	Banning	16.0 µg/L	Detected	15	B-
211	Ceres	15.7 µg/L	Detected	129	F
212	Guadalupe	15.6 µg/L	Detected	0	A
213	Santa Maria	15.1 µg/L	Detected	36	F
214	Calabasas	15.0 µg/L	Detected	14	A-
215	Oakley	15.0 µg/L	Detected	60	D
216	Big Bear Lake	14.5 µg/L	Detected	1	B+
217	Helendale	14.5 µg/L	Detected	22	A-
218	Lamont	14.1 µg/L	Detected	40	B+
219	Skyforest	14.1 µg/L	Detected	0	A-
220	Alturas	13.8 µg/L	Detected	11	B+
221	Joshua Tree	13.7 µg/L	Detected	3	A-
222	Bolinas	13.6 µg/L	Detected	49	A-
223	Daly City	13.0 µg/L	Detected	4	A
224	Nipomo	13.0 µg/L	Detected	1	A
225	Tahoe City	13.0 µg/L	Detected	11	B+
226	Rio Linda	12.9 µg/L	Detected	2	A-
227	Sonora	12.5 µg/L	Detected	25	D+
228	Moorpark	12.0 µg/L	Detected	1	A-
229	Pala	12.0 µg/L	Detected	30	C-
230	Porterville	11.6 µg/L	Detected	74	F
231	Orland	11.2 µg/L	Detected	5	A
232	Adelanto	11.1 µg/L	Detected	13	C
233	Santa Clara	11.0 µg/L	Detected	5	B
234	Gilroy	11.0 µg/L	Detected	28	C+
235	Grand Terrace	11.0 µg/L	Detected	1	B
236	Fort Irwin	11.0 µg/L	Detected	60	B+
237	Pismo Beach	10.8 µg/L	Detected	4	A-
238	Hesperia	10.2 µg/L	Detected	2	B
239	Corning	10.2 µg/L	Detected	17	B-
240	San Luis Obispo	10.0 µg/L	Detected	27	F
241	Ripon	9.9 µg/L	Detected	10	A-
242	Westlake Village	9.8 µg/L	Detected	8	F
243	West Covina	9.8 µg/L	Detected	25	F
244	Cutten	9.5 µg/L	Detected	5	A+
245	Pomona	9.3 µg/L	Detected	6	C+
246	Mountain View	9.3 µg/L	Detected	3	A
247	San Bernardin0	9.1 µg/L	Detected	0	A-
248	Wasco	9.1 µg/L	Detected	26	B+

FAQ

Frequently asked questions about lithium in California

Is lithium in California tap water harmful?

Lithium has no federal MCL or health advisory. Some state agencies use 60 µg/L as a screening level. 248 cities in California had detectable lithium in UCMR 5 testing. Therapeutic lithium doses (used to treat bipolar disorder) are far higher than typical drinking-water levels, but chronic low-level exposure has been studied for potential thyroid and mood effects.

Where does lithium in tap water come from?

Lithium occurs naturally in groundwater, especially in arid western states with lithium-bearing geology (parts of Nevada, California, North Carolina, Texas). It can also enter water from industrial sources such as battery manufacturing, ceramics, and lithium-mining wastewater. Geothermal hot springs are another natural source.

How can I remove lithium from my drinking water?

Reverse osmosis is highly effective at removing lithium, typically reducing it by 90% or more. Ion exchange systems and distillation also work well. Standard activated carbon filters are NOT effective against lithium. If you rely on a private well in a lithium-rich geological area, consider testing.

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