WaterVerge
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

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.

Cities exceeding 10 mg/L EPA MCL

California
100%
385 of 385 cities
= Exactly at national rate
National avg
100%
8001 of 8001 cities

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.

All California cities ranked by nitrate level

# City Level 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

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.