Nitrate Contamination

Nitrate in California Drinking Water

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

385

Cities Tested

385

Has Violations

100%

% Has Violations

10.9 violations

State Avg

▼ 0% vs national

vs National

624

Health Violations

Analysis

Nitrate in California: what the data shows

California has 385 cities with nitrate-related violations. The EPA MCL for nitrate is 10 mg/L (measured as nitrogen). The state has 385 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%

385 of 385 cities

← = Exactly at national rate

National avg

100%

8001 of 8001 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	Morgan Hill	81 violations	Yes	92	F
10	Corona	72 violations	Yes	81	D
11	Visalia	72 violations	Yes	121	D+
12	Pauma Valley	71 violations	Yes	88	F
13	Castroville	71 violations	Yes	86	D+
14	Fresno	66 violations	Yes	523	F
15	Jurupa Valley	60 violations	Yes	62	B
16	Anza	60 violations	Yes	53	F
17	Klamath	59 violations	Yes	102	D
18	Gonzales	55 violations	Yes	53	F
19	Sultana	55 violations	Yes	73	C-
20	Weldon	52 violations	Yes	193	D+
21	Tulare	51 violations	Yes	61	C-
22	Campo	49 violations	Yes	74	D
23	Clovis	47 violations	Yes	221	F
24	Thermal	40 violations	Yes	127	D
25	Santa Ysabel	38 violations	Yes	17	D
26	Springville	36 violations	Yes	82	D+
27	Lucerne Valley	35 violations	Yes	37	D
28	Pasadena	33 violations	Yes	92	F
29	Woodland	33 violations	Yes	52	F
30	Valley Center	32 violations	Yes	15	F
31	Hemet	31 violations	Yes	31	B-
32	Santa Rosa	29 violations	Yes	177	F
33	San Luis Obispo	29 violations	Yes	27	F
34	Hollister	28 violations	Yes	132	F
35	Julian	28 violations	Yes	22	D
36	Mcfarland	27 violations	Yes	42	C+
37	Meadview	27 violations	Yes	16	B
38	Meadview	27 violations	Yes	16	B
39	Soledad	24 violations	Yes	28	C+
40	Madera	22 violations	Yes	564	D
41	Needles	22 violations	Yes	45	F
42	Alpine	22 violations	Yes	25	C-
43	Point Arena	22 violations	Yes	24	D
44	Los Altos	21 violations	Yes	13	B
45	San Jose	20 violations	Yes	142	F
46	San Marcos	20 violations	Yes	27	D
47	Livingston	20 violations	Yes	29	C-
48	Lindsay	20 violations	Yes	240	F
49	Lancaster	20 violations	Yes	204	D
50	Oxnard	19 violations	Yes	49	F
51	Santa Maria	19 violations	Yes	36	F
52	Elk Grove	19 violations	Yes	28	C
53	Arroyo Grande	18 violations	Yes	93	F
54	Hilmar	18 violations	Yes	17	C
55	Frazier Park	18 violations	Yes	56	C+
56	San Diego	17 violations	Yes	43	F
57	Lake Isabella	17 violations	Yes	162	D+
58	Ceres	16 violations	Yes	129	F
59	Ojai	16 violations	Yes	35	C-
60	Three Rivers	16 violations	Yes	177	F
61	Tule River Reservation	16 violations	Yes	34	D
62	Trinidad	15 violations	Yes	30	D
63	Santa Cruz	14 violations	Yes	38	F
64	Colusa	14 violations	Yes	6	C-
65	Bishop	14 violations	Yes	25	D
66	Escalon	14 violations	Yes	13	A
67	Oakhurst	14 violations	Yes	198	D
68	Irvine	13 violations	Yes	84	F
69	Modesto	13 violations	Yes	76	D
70	Delano	13 violations	Yes	67	B
71	Ramona	13 violations	Yes	36	C
72	Norco	13 violations	Yes	39	F
73	Tipton	13 violations	Yes	15	B+
74	Inyokern	13 violations	Yes	21	D
75	Palm Springs	12 violations	Yes	16	B
76	West Covina	12 violations	Yes	25	F
77	Plymouth	12 violations	Yes	6	B
78	Fairfield	11 violations	Yes	7	B-
79	Gilroy	11 violations	Yes	28	C+
80	Arvin	11 violations	Yes	81	C+
81	Kerman	11 violations	Yes	13	B
82	Kingsburg	11 violations	Yes	17	B
83	Richgrove	11 violations	Yes	24	C
84	Watsonville	10 violations	Yes	74	F
85	San Francisco	10 violations	Yes	100	F
86	San Juan Bautista	10 violations	Yes	18	C+
87	Yuma	10 violations	Yes	22	D
88	Santa Barbara	9 violations	Yes	52	F
89	Napa	9 violations	Yes	53	F
90	Tehachapi	9 violations	Yes	96	F
91	Reedley	9 violations	Yes	12	B-
92	Westlake Village	9 violations	Yes	8	F
93	Exeter	9 violations	Yes	41	B
94	Willits	9 violations	Yes	23	C-
95	Mariposa	9 violations	Yes	71	C
96	Nixon	9 violations	Yes	2	C-
97	Nixon	9 violations	Yes	2	C-
98	Oakland	8 violations	Yes	13	B
99	Orange	8 violations	Yes	3	B
100	Indio	8 violations	Yes	12	F
101	Apple Valley	8 violations	Yes	57	D
102	Adelanto	8 violations	Yes	13	C
103	Sonora	8 violations	Yes	25	D+
104	Sanger	8 violations	Yes	16	C
105	Carmel	8 violations	Yes	49	C-
106	Laton	8 violations	Yes	49	C+
107	Upper Lake	8 violations	Yes	4	B
108	Wadsworth, Nv	8 violations	Yes	2	D+
109	Wadsworth, Nv	8 violations	Yes	2	D+
110	Madison	8 violations	Yes	6	D+
111	Los Angeles	7 violations	Yes	94	F
112	Rialto	7 violations	Yes	6	B+
113	Rancho Cordova	7 violations	Yes	115	F
114	Palmdale	7 violations	Yes	15	C+
115	Brentwood	7 violations	Yes	91	F
116	Colton	7 violations	Yes	5	B-
117	Pala	7 violations	Yes	30	C-
118	Georgetown	7 violations	Yes	4	B+
119	Havasu Lake	7 violations	Yes	37	D
120	Long Beach	6 violations	Yes	2	C
121	Riverside	6 violations	Yes	13	C
122	Hanford	6 violations	Yes	197	D+
123	Yucaipa	6 violations	Yes	9	C+
124	Lincoln	6 violations	Yes	6	A-
125	Granite Bay	6 violations	Yes	43	B-
126	Crestline	6 violations	Yes	9	C+
127	Blythe	6 violations	Yes	143	D
128	Coarsegold	6 violations	Yes	24	C-
129	Smith River	6 violations	Yes	11	C+
130	San Martin	6 violations	Yes	11	A-
131	Lone Pine Reservation	6 violations	Yes	6	A-
132	Ludlow	6 violations	Yes	82	D+
133	Alhambra	5 violations	Yes	7	A-
134	Encinitas	5 violations	Yes	55	F
135	Santee	5 violations	Yes	14	B
136	Rohnert Park	5 violations	Yes	21	F
137	Arcadia	5 violations	Yes	2	B
138	Desert Hot Springs	5 violations	Yes	4	A
139	Oakdale	5 violations	Yes	34	C-
140	Grover Beach	5 violations	Yes	34	F
141	Healdsburg	5 violations	Yes	12	B+
142	Forestville	5 violations	Yes	14	B-
143	Firebaugh	5 violations	Yes	89	D
144	Santa Ynez	5 violations	Yes	14	A-
145	Solvang	5 violations	Yes	6	B
146	Cutler	5 violations	Yes	20	B
147	Jamestown	5 violations	Yes	25	C+
148	Riverdale	5 violations	Yes	69	B+
149	Loleta	5 violations	Yes	3	B-
150	Bridgeport	5 violations	Yes	47	B-
151	North Edwards	5 violations	Yes	119	D
152	Downey	4 violations	Yes	14	B
153	Temecula	4 violations	Yes	12	C+
154	Ventura	4 violations	Yes	21	D+
155	Torrance	4 violations	Yes	0	A-
156	Manteca	4 violations	Yes	39	B-
157	Turlock	4 violations	Yes	16	B-
158	Laguna Beach	4 violations	Yes	2	B
159	Lake Forest	4 violations	Yes	38	B-
160	Oakley	4 violations	Yes	60	D
161	Beverly Hills	4 violations	Yes	18	B
162	San Juan Capistrano	4 violations	Yes	5	B+
163	La Verne	4 violations	Yes	6	B+
164	Lamont	4 violations	Yes	40	B+
165	Mendota	4 violations	Yes	3	A
166	Farmersville	4 violations	Yes	20	B+
167	Delhi	4 violations	Yes	7	A-
168	Idyllwild	4 violations	Yes	10	B
169	Hoopa	4 violations	Yes	16	B+
170	Twain Harte	4 violations	Yes	5	C+
171	Big Pine	4 violations	Yes	2	B
172	Cabazon	4 violations	Yes	5	A-
173	Gerber	4 violations	Yes	5	B
174	Yorba Linda	4 violations	Yes	38	B
175	Biola	4 violations	Yes	12	A
176	La Honda	4 violations	Yes	9	C-
177	Felton	4 violations	Yes	21	C
178	Warsaw	4 violations	Yes	2	A-
179	Santa Ana	3 violations	Yes	8	C
180	Spring Valley	3 violations	Yes	4	B
181	Rosemead	3 violations	Yes	17	C-
182	Rancho Cucamonga	3 violations	Yes	0	B+
183	Concord	3 violations	Yes	19	B-
184	Escondido	3 violations	Yes	10	B
185	Fullerton	3 violations	Yes	8	B
186	Pacific Grove	3 violations	Yes	15	B-
187	Camarillo	3 violations	Yes	4	B
188	Tustin	3 violations	Yes	8	B
189	Banning	3 violations	Yes	15	B-
190	Carmichael	3 violations	Yes	1	B+
191	Lebec	3 violations	Yes	42	C
192	Paso Robles	3 violations	Yes	42	F
193	Oroville	3 violations	Yes	7	C-
194	San Andreas	3 violations	Yes	17	B-
195	Wasco	3 violations	Yes	26	B+
196	Big Bear Lake	3 violations	Yes	1	B+
197	Olivehurst	3 violations	Yes	2	A
198	San Jacinto	3 violations	Yes	9	B
199	Marysville	3 violations	Yes	11	B+
200	Red Bluff	3 violations	Yes	23	F
201	Morro Bay	3 violations	Yes	12	A-
202	Jamul	3 violations	Yes	16	C+
203	Sonoma	3 violations	Yes	5	B-
204	Scotts Valley	3 violations	Yes	11	B-
205	Calimesa	3 violations	Yes	6	B
206	Live Oak	3 violations	Yes	26	A-
207	Earlimart	3 violations	Yes	40	B
208	Fowler	3 violations	Yes	2	A
209	Armona	3 violations	Yes	71	B+
210	Boron	3 violations	Yes	60	B+
211	Mi Wuk Village	3 violations	Yes	7	B+
212	Green Valley Lake	3 violations	Yes	2	C+
213	Bishop Paiute-Shoshone Reservation	3 violations	Yes	4	B
214	Caruthers	3 violations	Yes	63	B-
215	Devore	3 violations	Yes	2	A-
216	Buttonwillow	3 violations	Yes	14	A
217	Santa Rosa Rancheria	3 violations	Yes	25	D
218	Shaver Lake	3 violations	Yes	0	B+
219	Ducor	3 violations	Yes	10	A-
220	Palm Desert	2 violations	Yes	12	C+
221	San Dimas	2 violations	Yes	6	B-
222	Garden Grove	2 violations	Yes	2	B
223	San Bernardino	2 violations	Yes	192	F
224	Merced	2 violations	Yes	9	C+
225	Upland	2 violations	Yes	4	B+
226	Yuba City	2 violations	Yes	24	A-
227	Lodi	2 violations	Yes	16	C+
228	Newport Beach	2 violations	Yes	4	B+
229	La Habra	2 violations	Yes	0	A-
230	Lemoore	2 violations	Yes	112	D
231	Ridgecrest	2 violations	Yes	26	A-
232	Lakeside	2 violations	Yes	0	A-
233	Atascadero	2 violations	Yes	1	B
234	Atwater	2 violations	Yes	3	B+
235	Riverbank	2 violations	Yes	75	D
236	Greenfield	2 violations	Yes	17	B
237	Half Moon Bay	2 violations	Yes	6	A
238	Rosamond	2 violations	Yes	205	F
239	Lakeport	2 violations	Yes	14	C-
240	Pinedale	2 violations	Yes	7	A-
241	Ripon	2 violations	Yes	10	A-
242	El Cajon	2 violations	Yes	24	B+
243	Newman	2 violations	Yes	3	A-
244	King George	2 violations	Yes	30	D+
245	Cloverdale	2 violations	Yes	9	B
246	Winton	2 violations	Yes	5	A-
247	Orange Cove	2 violations	Yes	10	B+
248	La Canada	2 violations	Yes	5	B
249	Huron	2 violations	Yes	69	B-
250	Sebastopol	2 violations	Yes	18	B-
251	Fort Bragg	2 violations	Yes	4	B
252	Hughson	2 violations	Yes	139	D+
253	Castaic	2 violations	Yes	17	F
254	Beale Afb	2 violations	Yes	6	A
255	Gustine	2 violations	Yes	4	B+
256	Montara	2 violations	Yes	3	A-
257	Keyes	2 violations	Yes	60	B+
258	Denair	2 violations	Yes	3	A
259	Mojave	2 violations	Yes	114	D
260	Midway City	2 violations	Yes	11	A
261	Wheatland	2 violations	Yes	2	A
262	San Joaquin	2 violations	Yes	13	A
263	Aptos	2 violations	Yes	9	A-
264	Los Gatos	2 violations	Yes	138	D
265	Angwin	2 violations	Yes	37	B
266	Bloomington	2 violations	Yes	1	A
267	Littlerock	2 violations	Yes	0	A
268	Twin Peaks	2 violations	Yes	3	B
269	Pine Valley	2 violations	Yes	11	B-
270	Valley Springs	2 violations	Yes	2	A
271	Lost Hills	2 violations	Yes	13	A
272	Poplar	2 violations	Yes	5	A
273	Biggs	2 violations	Yes	3	B+
274	Big Sur	2 violations	Yes	58	C+
275	Le Grand	2 violations	Yes	15	B-
276	Kernville	2 violations	Yes	38	B-
277	Point Reyes Station	2 violations	Yes	0	A-
278	Forest Falls	2 violations	Yes	3	B-
279	Barstow	2 violations	Yes	66	F
280	Friant	2 violations	Yes	19	A-
281	Paicines	2 violations	Yes	9	B-
282	Corona Del Mar	2 violations	Yes	3	C-
283	Alpaugh	2 violations	Yes	48	B
284	Tranquillity	2 violations	Yes	37	B
285	Monterey	2 violations	Yes	3	B-
286	La Selva Beach	2 violations	Yes	0	A
287	West Hollywood	2 violations	Yes	17	B-
288	Big Pine Reservation	2 violations	Yes	5	A-
289	Palo Verde	2 violations	Yes	7	C
290	Crows Landing	2 violations	Yes	3	B
291	Mountain Center	2 violations	Yes	1	B+
292	Perris	1 violations	Yes	0	A
293	Hawthorne	1 violations	Yes	3	B
294	Covina	1 violations	Yes	10	B
295	El Monte	1 violations	Yes	79	F
296	Rancho Santa Margarita	1 violations	Yes	0	A
297	Sunnyvale	1 violations	Yes	3	A
298	Victorville	1 violations	Yes	1	B+
299	South Lake Tahoe	1 violations	Yes	15	C
300	Hesperia	1 violations	Yes	2	B
301	Chino	1 violations	Yes	9	B
302	Simi Valley	1 violations	Yes	3	A
303	Goleta	1 violations	Yes	11	B
304	Chino Hills	1 violations	Yes	2	A
305	Lakewood	1 violations	Yes	1	A-
306	Petaluma	1 violations	Yes	2	B
307	Lompoc	1 violations	Yes	18	C
308	San Bruno	1 violations	Yes	0	A+
309	Livermore	1 violations	Yes	53	B
310	Monrovia	1 violations	Yes	0	B+
311	La Crescenta	1 violations	Yes	3	B+
312	Martinez	1 violations	Yes	0	A
313	Yucca Valley	1 violations	Yes	7	A-
314	Galt	1 violations	Yes	27	B+
315	South Pasadena	1 violations	Yes	5	A
316	Patterson	1 violations	Yes	35	B+
317	Shafter	1 violations	Yes	25	A-
318	Corcoran	1 violations	Yes	3	A
319	Menlo Park	1 violations	Yes	2	A-
320	Port Hueneme	1 violations	Yes	0	B+
321	Twentynine Palms	1 violations	Yes	70	B+
322	Coalinga	1 violations	Yes	267	D
323	Fillmore	1 violations	Yes	13	B-
324	Sutter Creek	1 violations	Yes	7	B+
325	Rio Linda	1 violations	Yes	2	A-
326	Avenal	1 violations	Yes	35	B
327	Palomar Mtn Road	1 violations	Yes	2	A+
328	Edwards Afb	1 violations	Yes	8	A-
329	La Canada Flintridge	1 violations	Yes	4	A
330	Mammoth Lakes	1 violations	Yes	24	B
331	Pismo Beach	1 violations	Yes	4	A-
332	Oceano	1 violations	Yes	1	A
333	Gridley	1 violations	Yes	4	B
334	Kelseyville	1 violations	Yes	36	B-
335	Nuevo	1 violations	Yes	6	B+
336	China Lake	1 violations	Yes	8	A
337	Helendale	1 violations	Yes	22	A-
338	Running Springs	1 violations	Yes	3	B
339	June Lake	1 violations	Yes	14	B
340	Carnelian Bay	1 violations	Yes	15	B
341	Murphys	1 violations	Yes	11	B+
342	Ivanhoe	1 violations	Yes	6	A-
343	La Grange	1 violations	Yes	13	B
344	Cobb	1 violations	Yes	3	C+
345	Wildomar	1 violations	Yes	11	A-
346	Groveland	1 violations	Yes	4	B-
347	Borrego Springs	1 violations	Yes	2	A+
348	Aromas	1 violations	Yes	55	B-
349	Seaside	1 violations	Yes	1	A-
350	Brownsville	1 violations	Yes	0	A-
351	Dublin	1 violations	Yes	0	A
352	Terra Bella	1 violations	Yes	26	A-
353	Talmage	1 violations	Yes	2	B-
354	Gualala	1 violations	Yes	2	A+
355	Middletown	1 violations	Yes	32	D+
356	Cedarpines Park	1 violations	Yes	5	A
357	Clearlake Oak	1 violations	Yes	4	B+
358	Pine Grove	1 violations	Yes	17	B
359	Pine Mountain Club	1 violations	Yes	9	A-
360	Graeagle	1 violations	Yes	4	B+
361	Durham	1 violations	Yes	3	A
362	Angelus Oaks	1 violations	Yes	7	B-
363	Bodega Bay	1 violations	Yes	2	A-
364	Pinecrest	1 violations	Yes	3	B-
365	Green Valley	1 violations	Yes	3	B+
366	Kettleman City	1 violations	Yes	58	C+
367	Mount Hermon	1 violations	Yes	1	B+
368	Barona North Reservation	1 violations	Yes	0	A-
369	Dillon Beach	1 violations	Yes	32	B
370	Laytonville	1 violations	Yes	13	A
371	Redwood Valley	1 violations	Yes	2	C
372	Saratoga	1 violations	Yes	7	B+
373	Baker	1 violations	Yes	1	B+
374	North Highlands	1 violations	Yes	1	A-
375	Occidental	1 violations	Yes	3	A
376	Labelle	1 violations	Yes	7	B
377	Etna	1 violations	Yes	2	A-
378	New Cuyama	1 violations	Yes	21	A
379	Bear River - Tish Non Village	1 violations	Yes	0	A-
380	Mineral	1 violations	Yes	2	A-
381	Isleton	1 violations	Yes	52	C+
382	San Ardo	1 violations	Yes	4	A-
383	River Pines	1 violations	Yes	3	A-
384	Jacumba	1 violations	Yes	0	A+
385	Grimes	1 violations	Yes	61	D

FAQ

Frequently asked questions about nitrate in California

Is nitrate in California tap water dangerous?

Yes — 385 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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