Nitrate Contamination

Nitrate in California Drinking Water

Ranked by nitrate violation count · Data from EPA SDWIS & UCMR

382

Cities Tested

382

Has Violations

100%

% Has Violations

10.8 violations

State Avg

▼ 0% vs national

vs National

620

Health Violations

Analysis

Nitrate in California: what the data shows

California has 382 cities with nitrate-related violations. The EPA MCL for nitrate is 10 mg/L (measured as nitrogen). The state has 382 cities with at least one nitrate violation. Nitrate is the most common groundwater contaminant in the United States. It enters water supplies primarily through agricultural fertilizer runoff, septic system leaching, and animal feedlot operations. Rural and agricultural communities face the highest risk. The primary acute health concern is methemoglobinemia ("blue baby syndrome") in infants under six months. Emerging research also links chronic nitrate exposure to thyroid disease, certain cancers, and adverse birth outcomes. Reverse osmosis, ion exchange, and distillation can remove nitrate from drinking water — standard carbon filters do not.

Comparison

Cities exceeding 10 mg/L EPA MCL

California

100%

382 of 382 cities

← = Exactly at national rate

National avg

100%

7727 of 7727 cities

City Map

Nitrate data across California

Each dot is a city with nitrate violation data. Cities with at least one nitrate-related violation are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by nitrate level in California

Highest Nitrate levels (violations)

All Cities

All California cities ranked by nitrate level

#	City	Level	Violations?	Violations	Grade
1	Bakersfield	258 violations	Yes	690	F
2	Salinas	240 violations	Yes	639	F
3	Royal Oaks	132 violations	Yes	201	D
4	Chico	122 violations	Yes	306	F
5	Stockton	112 violations	Yes	261	F
6	Strathmore	110 violations	Yes	118	D+
7	Sacramento	99 violations	Yes	425	F
8	Porterville	81 violations	Yes	74	F
9	Corona	72 violations	Yes	81	D
10	Visalia	72 violations	Yes	121	D+
11	Pauma Valley	71 violations	Yes	88	F
12	Castroville	71 violations	Yes	86	D+
13	Fresno	66 violations	Yes	523	F
14	Jurupa Valley	60 violations	Yes	62	B
15	Anza	60 violations	Yes	53	F
16	Klamath	59 violations	Yes	102	D
17	Gonzales	55 violations	Yes	53	F
18	Sultana	55 violations	Yes	73	C-
19	Weldon	52 violations	Yes	193	D+
20	Tulare	51 violations	Yes	61	C-
21	Campo	49 violations	Yes	74	D
22	Clovis	47 violations	Yes	221	F
23	Thermal	40 violations	Yes	127	D
24	Santa Ysabel	38 violations	Yes	17	D
25	Springville	36 violations	Yes	82	D+
26	Lucerne Valley	35 violations	Yes	37	D
27	Pasadena	33 violations	Yes	92	F
28	Woodland	33 violations	Yes	52	F
29	Valley Center	32 violations	Yes	15	F
30	Hemet	31 violations	Yes	31	B-
31	Santa Rosa	29 violations	Yes	177	F
32	San Luis Obispo	29 violations	Yes	27	F
33	Hollister	28 violations	Yes	132	F
34	Julian	28 violations	Yes	22	D
35	Mcfarland	27 violations	Yes	42	C+
36	Meadview	27 violations	Yes	16	B
37	Meadview	27 violations	Yes	16	B
38	Soledad	24 violations	Yes	28	C+
39	Madera	22 violations	Yes	564	D
40	Needles	22 violations	Yes	45	F
41	Alpine	22 violations	Yes	25	C-
42	Point Arena	22 violations	Yes	24	D
43	Los Altos	21 violations	Yes	13	B
44	San Jose	20 violations	Yes	142	F
45	San Marcos	20 violations	Yes	27	D
46	Livingston	20 violations	Yes	29	C-
47	Lancaster	20 violations	Yes	204	D
48	Lindsay	20 violations	Yes	240	F
49	Oxnard	19 violations	Yes	49	F
50	Santa Maria	19 violations	Yes	36	F
51	Elk Grove	19 violations	Yes	28	C
52	Arroyo Grande	18 violations	Yes	93	F
53	Hilmar	18 violations	Yes	17	C
54	Frazier Park	18 violations	Yes	56	C+
55	San Diego	17 violations	Yes	43	F
56	Lake Isabella	17 violations	Yes	162	D+
57	Ceres	16 violations	Yes	129	F
58	Ojai	16 violations	Yes	35	C-
59	Three Rivers	16 violations	Yes	177	F
60	Tule River Reservation	16 violations	Yes	34	D
61	Trinidad	15 violations	Yes	30	D
62	Santa Cruz	14 violations	Yes	38	F
63	Colusa	14 violations	Yes	6	C-
64	Bishop	14 violations	Yes	25	D
65	Escalon	14 violations	Yes	13	A
66	Oakhurst	14 violations	Yes	198	D
67	Irvine	13 violations	Yes	84	F
68	Modesto	13 violations	Yes	76	D
69	Delano	13 violations	Yes	67	B
70	Ramona	13 violations	Yes	36	C
71	Norco	13 violations	Yes	39	F
72	Tipton	13 violations	Yes	15	B+
73	Inyokern	13 violations	Yes	21	D
74	Palm Springs	12 violations	Yes	16	B
75	West Covina	12 violations	Yes	25	F
76	Plymouth	12 violations	Yes	6	B
77	Fairfield	11 violations	Yes	7	B-
78	Gilroy	11 violations	Yes	28	C+
79	Arvin	11 violations	Yes	81	C+
80	Kerman	11 violations	Yes	13	B
81	Kingsburg	11 violations	Yes	17	B
82	Richgrove	11 violations	Yes	24	C
83	Watsonville	10 violations	Yes	74	F
84	San Francisco	10 violations	Yes	100	F
85	San Juan Bautista	10 violations	Yes	18	C+
86	Santa Barbara	9 violations	Yes	52	F
87	Napa	9 violations	Yes	53	F
88	Tehachapi	9 violations	Yes	96	F
89	Reedley	9 violations	Yes	12	B-
90	Westlake Village	9 violations	Yes	8	F
91	Exeter	9 violations	Yes	41	B
92	Willits	9 violations	Yes	23	C-
93	Mariposa	9 violations	Yes	71	C
94	Nixon	9 violations	Yes	2	C-
95	Nixon	9 violations	Yes	2	C-
96	Oakland	8 violations	Yes	13	B
97	Orange	8 violations	Yes	3	B
98	Indio	8 violations	Yes	12	F
99	Apple Valley	8 violations	Yes	57	D
100	Adelanto	8 violations	Yes	13	C
101	Sonora	8 violations	Yes	25	D+
102	Sanger	8 violations	Yes	16	C
103	Carmel	8 violations	Yes	49	C-
104	Laton	8 violations	Yes	49	C+
105	Upper Lake	8 violations	Yes	4	B
106	Wadsworth, Nv	8 violations	Yes	2	D+
107	Wadsworth, Nv	8 violations	Yes	2	D+
108	Madison	8 violations	Yes	6	D+
109	Los Angeles	7 violations	Yes	94	F
110	Rialto	7 violations	Yes	6	B+
111	Rancho Cordova	7 violations	Yes	115	F
112	Palmdale	7 violations	Yes	15	C+
113	Brentwood	7 violations	Yes	91	F
114	Colton	7 violations	Yes	5	B-
115	Pala	7 violations	Yes	30	C-
116	Georgetown	7 violations	Yes	4	B+
117	Havasu Lake	7 violations	Yes	37	D
118	Long Beach	6 violations	Yes	2	C
119	Riverside	6 violations	Yes	13	C
120	Hanford	6 violations	Yes	197	D+
121	Yucaipa	6 violations	Yes	9	C+
122	Lincoln	6 violations	Yes	6	A-
123	Granite Bay	6 violations	Yes	43	B-
124	Crestline	6 violations	Yes	9	C+
125	Blythe	6 violations	Yes	143	D
126	Coarsegold	6 violations	Yes	24	C-
127	Smith River	6 violations	Yes	11	C+
128	San Martin	6 violations	Yes	11	A-
129	Lone Pine Reservation	6 violations	Yes	6	A-
130	Ludlow	6 violations	Yes	82	D+
131	Alhambra	5 violations	Yes	7	A-
132	Encinitas	5 violations	Yes	55	F
133	Santee	5 violations	Yes	14	B
134	Rohnert Park	5 violations	Yes	21	F
135	Arcadia	5 violations	Yes	2	B
136	Desert Hot Springs	5 violations	Yes	4	A
137	Oakdale	5 violations	Yes	34	C-
138	Grover Beach	5 violations	Yes	34	F
139	Healdsburg	5 violations	Yes	12	B+
140	Forestville	5 violations	Yes	14	B-
141	Firebaugh	5 violations	Yes	89	D
142	Santa Ynez	5 violations	Yes	14	A-
143	Solvang	5 violations	Yes	6	B
144	Cutler	5 violations	Yes	20	B
145	Jamestown	5 violations	Yes	25	C+
146	Riverdale	5 violations	Yes	69	B+
147	Loleta	5 violations	Yes	3	B-
148	Bridgeport	5 violations	Yes	47	B-
149	North Edwards	5 violations	Yes	119	D
150	Downey	4 violations	Yes	14	B
151	Temecula	4 violations	Yes	12	C+
152	Ventura	4 violations	Yes	21	D+
153	Torrance	4 violations	Yes	0	A-
154	Manteca	4 violations	Yes	39	B-
155	Turlock	4 violations	Yes	16	B-
156	Laguna Beach	4 violations	Yes	2	B
157	Lake Forest	4 violations	Yes	38	B-
158	Oakley	4 violations	Yes	60	D
159	Beverly Hills	4 violations	Yes	18	B
160	La Verne	4 violations	Yes	6	B+
161	Lamont	4 violations	Yes	40	B+
162	Mendota	4 violations	Yes	3	A
163	Farmersville	4 violations	Yes	20	B+
164	Delhi	4 violations	Yes	7	A-
165	Idyllwild	4 violations	Yes	10	B
166	Hoopa	4 violations	Yes	16	B+
167	Twain Harte	4 violations	Yes	5	C+
168	Big Pine	4 violations	Yes	2	B
169	Cabazon	4 violations	Yes	5	A-
170	Gerber	4 violations	Yes	5	B
171	Yorba Linda	4 violations	Yes	38	B
172	Biola	4 violations	Yes	12	A
173	La Honda	4 violations	Yes	9	C-
174	Felton	4 violations	Yes	21	C
175	Warsaw	4 violations	Yes	2	A-
176	Santa Ana	3 violations	Yes	8	C
177	Spring Valley	3 violations	Yes	4	B
178	Rosemead	3 violations	Yes	17	C-
179	Rancho Cucamonga	3 violations	Yes	0	B+
180	Concord	3 violations	Yes	19	B-
181	Escondido	3 violations	Yes	10	B
182	Fullerton	3 violations	Yes	8	B
183	Pacific Grove	3 violations	Yes	15	B-
184	Camarillo	3 violations	Yes	4	B
185	Tustin	3 violations	Yes	8	B
186	Banning	3 violations	Yes	15	B-
187	Carmichael	3 violations	Yes	1	B+
188	Lebec	3 violations	Yes	42	C
189	Paso Robles	3 violations	Yes	42	F
190	Oroville	3 violations	Yes	7	C-
191	San Andreas	3 violations	Yes	17	B-
192	Wasco	3 violations	Yes	26	B+
193	Big Bear Lake	3 violations	Yes	1	B+
194	Olivehurst	3 violations	Yes	2	A
195	San Jacinto	3 violations	Yes	9	B
196	Marysville	3 violations	Yes	11	B+
197	Red Bluff	3 violations	Yes	23	F
198	Morro Bay	3 violations	Yes	12	A-
199	Jamul	3 violations	Yes	16	C+
200	Sonoma	3 violations	Yes	5	B-
201	Scotts Valley	3 violations	Yes	11	B-
202	Calimesa	3 violations	Yes	6	B
203	Live Oak	3 violations	Yes	26	A-
204	Earlimart	3 violations	Yes	40	B
205	Fowler	3 violations	Yes	2	A
206	Armona	3 violations	Yes	71	B+
207	Boron	3 violations	Yes	60	B+
208	Green Valley Lake	3 violations	Yes	2	C+
209	Bishop Paiute-Shoshone Reservation	3 violations	Yes	4	B
210	Caruthers	3 violations	Yes	63	B-
211	Mi Wuk Village	3 violations	Yes	7	B+
212	Devore	3 violations	Yes	2	A-
213	Buttonwillow	3 violations	Yes	14	A
214	Santa Rosa Rancheria	3 violations	Yes	25	D
215	Shaver Lake	3 violations	Yes	0	B+
216	Ducor	3 violations	Yes	10	A-
217	Palm Desert	2 violations	Yes	12	C+
218	San Dimas	2 violations	Yes	6	B-
219	Garden Grove	2 violations	Yes	2	B
220	San Bernardino	2 violations	Yes	192	F
221	Merced	2 violations	Yes	9	C+
222	Upland	2 violations	Yes	4	B+
223	Yuba City	2 violations	Yes	24	A-
224	Lodi	2 violations	Yes	16	C+
225	Newport Beach	2 violations	Yes	4	B+
226	La Habra	2 violations	Yes	0	A-
227	Lemoore	2 violations	Yes	112	D
228	Ridgecrest	2 violations	Yes	26	A-
229	Lakeside	2 violations	Yes	0	A-
230	Atascadero	2 violations	Yes	1	B
231	Atwater	2 violations	Yes	3	B+
232	Riverbank	2 violations	Yes	75	D
233	Greenfield	2 violations	Yes	17	B
234	Half Moon Bay	2 violations	Yes	6	A
235	Rosamond	2 violations	Yes	205	F
236	Lakeport	2 violations	Yes	14	C-
237	Pinedale	2 violations	Yes	7	A-
238	Ripon	2 violations	Yes	10	A-
239	El Cajon	2 violations	Yes	24	B+
240	Newman	2 violations	Yes	3	A-
241	King George	2 violations	Yes	30	D+
242	Cloverdale	2 violations	Yes	9	B
243	Winton	2 violations	Yes	5	A-
244	Orange Cove	2 violations	Yes	10	B+
245	La Canada	2 violations	Yes	5	B
246	Huron	2 violations	Yes	69	B-
247	Sebastopol	2 violations	Yes	18	B-
248	Fort Bragg	2 violations	Yes	4	B
249	Hughson	2 violations	Yes	139	D+
250	Castaic	2 violations	Yes	17	F
251	Beale Afb	2 violations	Yes	6	A
252	Gustine	2 violations	Yes	4	B+
253	Montara	2 violations	Yes	3	A-
254	Keyes	2 violations	Yes	60	B+
255	Denair	2 violations	Yes	3	A
256	Mojave	2 violations	Yes	114	D
257	Wheatland	2 violations	Yes	2	A
258	San Joaquin	2 violations	Yes	13	A
259	Aptos	2 violations	Yes	9	A-
260	Los Gatos	2 violations	Yes	138	D
261	Angwin	2 violations	Yes	37	B
262	Bloomington	2 violations	Yes	1	A
263	Littlerock	2 violations	Yes	0	A
264	Twin Peaks	2 violations	Yes	3	B
265	Pine Valley	2 violations	Yes	11	B-
266	Valley Springs	2 violations	Yes	2	A
267	Lost Hills	2 violations	Yes	13	A
268	Poplar	2 violations	Yes	5	A
269	Biggs	2 violations	Yes	3	B+
270	Big Sur	2 violations	Yes	58	C+
271	Midway City	2 violations	Yes	11	A
272	Le Grand	2 violations	Yes	15	B-
273	Kernville	2 violations	Yes	38	B-
274	Point Reyes Station	2 violations	Yes	0	A-
275	Forest Falls	2 violations	Yes	3	B-
276	Barstow	2 violations	Yes	66	F
277	Friant	2 violations	Yes	19	A-
278	Paicines	2 violations	Yes	9	B-
279	Corona Del Mar	2 violations	Yes	3	C-
280	Alpaugh	2 violations	Yes	48	B
281	Tranquillity	2 violations	Yes	37	B
282	Monterey	2 violations	Yes	3	B-
283	La Selva Beach	2 violations	Yes	0	A
284	West Hollywood	2 violations	Yes	17	B-
285	Big Pine Reservation	2 violations	Yes	5	A-
286	Palo Verde	2 violations	Yes	7	C
287	Crows Landing	2 violations	Yes	3	B
288	Mountain Center	2 violations	Yes	1	B+
289	Perris	1 violations	Yes	0	A
290	Covina	1 violations	Yes	10	B
291	Hawthorne	1 violations	Yes	3	B
292	El Monte	1 violations	Yes	79	F
293	Rancho Santa Margarita	1 violations	Yes	0	A
294	Sunnyvale	1 violations	Yes	3	A
295	Victorville	1 violations	Yes	1	B+
296	South Lake Tahoe	1 violations	Yes	15	C
297	Hesperia	1 violations	Yes	2	B
298	Chino	1 violations	Yes	9	B
299	Simi Valley	1 violations	Yes	3	A
300	Goleta	1 violations	Yes	11	B
301	Chino Hills	1 violations	Yes	2	A
302	Lakewood	1 violations	Yes	1	A-
303	Petaluma	1 violations	Yes	2	B
304	Lompoc	1 violations	Yes	18	C
305	San Bruno	1 violations	Yes	0	A+
306	Livermore	1 violations	Yes	53	B
307	Monrovia	1 violations	Yes	0	B+
308	La Crescenta	1 violations	Yes	3	B+
309	Martinez	1 violations	Yes	0	A
310	Yucca Valley	1 violations	Yes	7	A-
311	Galt	1 violations	Yes	27	B+
312	South Pasadena	1 violations	Yes	5	A
313	Patterson	1 violations	Yes	35	B+
314	Shafter	1 violations	Yes	25	A-
315	Corcoran	1 violations	Yes	3	A
316	Menlo Park	1 violations	Yes	2	A-
317	Port Hueneme	1 violations	Yes	0	B+
318	Twentynine Palms	1 violations	Yes	70	B+
319	Coalinga	1 violations	Yes	267	D
320	Fillmore	1 violations	Yes	13	B-
321	Sutter Creek	1 violations	Yes	7	B+
322	Rio Linda	1 violations	Yes	2	A-
323	Avenal	1 violations	Yes	35	B
324	Palomar Mtn Road	1 violations	Yes	2	A+
325	Edwards Afb	1 violations	Yes	8	A-
326	La Canada Flintridge	1 violations	Yes	4	A
327	Mammoth Lakes	1 violations	Yes	24	B
328	Pismo Beach	1 violations	Yes	4	A-
329	Oceano	1 violations	Yes	1	A
330	Gridley	1 violations	Yes	4	B
331	Kelseyville	1 violations	Yes	36	B-
332	Nuevo	1 violations	Yes	6	B+
333	China Lake	1 violations	Yes	8	A
334	Helendale	1 violations	Yes	22	A-
335	Running Springs	1 violations	Yes	3	B
336	June Lake	1 violations	Yes	14	B
337	Carnelian Bay	1 violations	Yes	15	B
338	Murphys	1 violations	Yes	11	B+
339	Ivanhoe	1 violations	Yes	6	A-
340	La Grange	1 violations	Yes	13	B
341	Cobb	1 violations	Yes	3	C+
342	Wildomar	1 violations	Yes	11	A-
343	Groveland	1 violations	Yes	4	B-
344	Borrego Springs	1 violations	Yes	2	A+
345	Aromas	1 violations	Yes	55	B-
346	Seaside	1 violations	Yes	1	A-
347	Brownsville	1 violations	Yes	0	A-
348	Dublin	1 violations	Yes	0	A
349	Terra Bella	1 violations	Yes	26	A-
350	Talmage	1 violations	Yes	2	B-
351	Gualala	1 violations	Yes	2	A+
352	Middletown	1 violations	Yes	32	D+
353	Cedarpines Park	1 violations	Yes	5	A
354	Clearlake Oak	1 violations	Yes	4	B+
355	Pine Grove	1 violations	Yes	17	B
356	Pine Mountain Club	1 violations	Yes	9	A-
357	Graeagle	1 violations	Yes	4	B+
358	Durham	1 violations	Yes	3	A
359	Angelus Oaks	1 violations	Yes	7	B-
360	Bodega Bay	1 violations	Yes	2	A-
361	Pinecrest	1 violations	Yes	3	B-
362	Green Valley	1 violations	Yes	3	B+
363	Kettleman City	1 violations	Yes	58	C+
364	Mount Hermon	1 violations	Yes	1	B+
365	Barona North Reservation	1 violations	Yes	0	A-
366	Dillon Beach	1 violations	Yes	32	B
367	Laytonville	1 violations	Yes	13	A
368	Redwood Valley	1 violations	Yes	2	C
369	Saratoga	1 violations	Yes	7	B+
370	Baker	1 violations	Yes	1	B+
371	North Highlands	1 violations	Yes	1	A-
372	Occidental	1 violations	Yes	3	A
373	Labelle	1 violations	Yes	7	B
374	Etna	1 violations	Yes	2	A-
375	New Cuyama	1 violations	Yes	21	A
376	Bear River - Tish Non Village	1 violations	Yes	0	A-
377	Mineral	1 violations	Yes	2	A-
378	Isleton	1 violations	Yes	52	C+
379	San Ardo	1 violations	Yes	4	A-
380	River Pines	1 violations	Yes	3	A-
381	Jacumba	1 violations	Yes	0	A+
382	Grimes	1 violations	Yes	61	D

FAQ

Frequently asked questions about nitrate in California

Is nitrate in California tap water dangerous?

Yes — 382 cities in California have nitrate-related violations. The EPA MCL is 10 mg/L. Nitrate is especially dangerous for infants under six months, where it can cause methemoglobinemia ("blue baby syndrome"). Adults face lower acute risk, but chronic exposure is linked to thyroid disease and certain cancers.

How can I remove nitrate from my drinking water?

Reverse osmosis, ion exchange, and distillation are effective at removing nitrate. Standard carbon filters (including most pitcher and faucet-mount filters) do NOT remove nitrate. If you rely on a private well in an agricultural area, have your water tested annually for nitrate.

What causes high nitrate levels in California water?

Nitrate contamination comes primarily from agricultural fertilizer runoff, septic system leaching, and animal feedlot operations. Rural communities near intensive farming are most at risk. Shallow wells are particularly vulnerable. Heavy rainfall can spike nitrate levels as it washes fertilizer into groundwater and surface water supplies.

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