HAA5 Contamination

HAA5 in California Drinking Water

Ranked by average HAA5 concentration (µg/L) · UCMR 4 data (2018–2020) · Data from EPA SDWIS & UCMR

337

Cities Tested

Exceeds Limit

% Exceeds Limit

9.0 µg/L

State Avg

▼ 1% vs national

vs National

620

Health Violations

Analysis

HAA5 in California: what the data shows

California has 337 cities with HAA5 monitoring data from the EPA's UCMR 4 program (2018–2020). Haloacetic acids (HAA5) form when chlorine-based disinfectants react with natural organic matter in water. The state average is 9.0 µg/L — better than the 15.5 µg/L national average. No cities currently exceed the 60 µg/L EPA MCL. HAA5 is a group of five chlorinated and brominated acetic acids. Long-term exposure above the MCL is associated with increased cancer risk and adverse reproductive outcomes. The EPA classifies total HAA5 as a probable human carcinogen at elevated concentrations. Activated carbon filtration (especially granular or block carbon) is effective at reducing HAA5. Running water through a refrigerator filter or letting it sit in an open pitcher for 30 minutes also helps, as some HAA5 species are volatile. Boiling does not remove disinfection byproducts and may concentrate them.

Comparison

Cities exceeding 60 µg/L EPA MCL

California

0 of 337 cities

← ▼ 1% below national rate (better)

National avg

23 of 4342 cities

City Map

HAA5 data across California

Each dot is a city with UCMR 4 HAA5 testing data. Cities where average HAA5 exceeded the 60 µg/L EPA MCL are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by haa5 level in California

Highest HAA5 levels (µg/L)

All Cities

All California cities ranked by haa5 level

#	City	Level	Exceeds?	Violations	Grade
1	Shasta	47.7 µg/L	No	0	A+
2	Lindsay	40.8 µg/L	No	240	F
3	Sonora	39.6 µg/L	No	25	D+
4	Burlingame	36.8 µg/L	No	14	A-
5	American Canyon	36.0 µg/L	No	15	A-
6	Placerville	34.6 µg/L	No	6	A-
7	Idyllwild	34.4 µg/L	No	10	B
8	Oakland	34.2 µg/L	No	13	B
9	San Andreas	33.7 µg/L	No	17	B-
10	Redwood City	32.9 µg/L	No	10	B+
11	Santa Cruz	32.9 µg/L	No	38	F
12	Lathrop	31.5 µg/L	No	44	B
13	Menlo Park	31.2 µg/L	No	2	A-
14	Palo Alto	31.0 µg/L	No	8	A-
15	Lincoln	30.1 µg/L	No	6	A-
16	Hayward	30.1 µg/L	No	0	A-
17	Milpitas	30.1 µg/L	No	2	A-
18	Hillsborough	29.8 µg/L	No	7	A
19	Stanford	29.3 µg/L	No	3	A+
20	Redding	27.9 µg/L	No	49	F
21	Napa	27.9 µg/L	No	53	F
22	Folsom	27.2 µg/L	No	1	A-
23	Citrus Heights	26.9 µg/L	No	2	A
24	Yuba City	26.7 µg/L	No	24	A-
25	San Luis Obispo	26.5 µg/L	No	27	F
26	Taft	26.4 µg/L	No	0	A-
27	Bakersfield	25.8 µg/L	No	690	F
28	Calexico	25.6 µg/L	No	7	B-
29	Auburn	24.7 µg/L	No	8	A
30	Foster City	24.6 µg/L	No	2	A+
31	Orangevale	24.6 µg/L	No	0	A
32	Carpinteria	24.2 µg/L	No	5	A
33	Granite Bay	24.1 µg/L	No	43	B-
34	Belmont	24.1 µg/L	No	3	A+
35	Ventura	24.0 µg/L	No	21	D+
36	Fair Oaks	23.1 µg/L	No	0	B+
37	Millbrae	22.9 µg/L	No	1	A-
38	East Palo Alto	22.8 µg/L	No	8	A
39	Paradise	22.7 µg/L	No	2	A
40	Daly City	22.4 µg/L	No	4	A
41	Imperial	22.1 µg/L	No	36	C+
42	Mountain View	21.9 µg/L	No	3	A
43	Stockton	21.3 µg/L	No	261	F
44	Fort Bragg	21.2 µg/L	No	4	B
45	Shasta Lake 4510007	21.1 µg/L	No	1	A+
46	Rancho Santa Fe	20.5 µg/L	No	3	A-
47	Sunnyvale	20.4 µg/L	No	3	A
48	Santa Barbara	20.3 µg/L	No	52	F
49	Manteca	20.0 µg/L	No	39	B-
50	Poway	19.9 µg/L	No	0	A-
51	Grass Valley	19.8 µg/L	No	8	A
52	Tracy	19.7 µg/L	No	45	C
53	Goleta	19.6 µg/L	No	11	B
54	El Centro	19.6 µg/L	No	14	C-
55	West Sacramento	19.3 µg/L	No	1	B+
56	Murphys	19.0 µg/L	No	11	B+
57	Arroyo Grande	18.9 µg/L	No	93	F
58	Brawley	18.9 µg/L	No	5	A-
59	Half Moon Bay	18.7 µg/L	No	6	A
60	Roseville	17.7 µg/L	No	11	B
61	Oroville	17.4 µg/L	No	7	C-
62	Chula Vista	17.3 µg/L	No	1	B+
63	Santa Clara	17.3 µg/L	No	5	B
64	Modesto	17.1 µg/L	No	76	D
65	Encinitas	16.7 µg/L	No	55	F
66	Benicia	16.5 µg/L	No	1	A-
67	Vacaville	16.0 µg/L	No	26	F
68	Cupertino	15.8 µg/L	No	3	A+
69	Oceanside	15.6 µg/L	No	2	A-
70	Sacramento	15.3 µg/L	No	425	F
71	Clearlake	15.2 µg/L	No	5	B+
72	Avenal	14.8 µg/L	No	35	B
73	Corte Madera	14.3 µg/L	No	0	A-
74	Crescent City	14.3 µg/L	No	14	C
75	Escondido	14.2 µg/L	No	10	B
76	Fairfield	14.1 µg/L	No	7	B-
77	Boulder Creek	14.0 µg/L	No	119	F
78	Three Rivers	14.0 µg/L	No	177	F
79	Grover Beach	13.9 µg/L	No	34	F
80	Vallejo	13.7 µg/L	No	6	A
81	Hollister	13.7 µg/L	No	132	F
82	San Jose	13.3 µg/L	No	142	F
83	Morro Bay	13.3 µg/L	No	12	A-
84	Vista	13.1 µg/L	No	0	A-
85	Pacific Grove	13.0 µg/L	No	15	B-
86	Paso Robles	12.6 µg/L	No	42	F
87	Lemoore	12.6 µg/L	No	112	D
88	Redlands	12.5 µg/L	No	2	B
89	Yucaipa	12.0 µg/L	No	9	C+
90	La Crescenta	12.0 µg/L	No	3	B+
91	Azusa	11.9 µg/L	No	2	B+
92	Walnut	11.9 µg/L	No	1	A-
93	Livermore	11.7 µg/L	No	53	B
94	Blythe	11.5 µg/L	No	143	D
95	Chico	11.2 µg/L	No	306	F
96	La Verne	11.1 µg/L	No	6	B+
97	Atascadero	10.5 µg/L	No	1	B
98	Highland	10.5 µg/L	No	3	B+
99	Trabuco Canyon	10.5 µg/L	No	2	A-
100	Coalinga	10.5 µg/L	No	267	D
101	Manhattan Beach	10.5 µg/L	No	1	A-
102	Clovis	10.4 µg/L	No	221	F
103	Long Beach	10.2 µg/L	No	2	C
104	Point Mugu	10.1 µg/L	No	11	A-
105	Pacifica	10.1 µg/L	No	2	A
106	Novato	10.0 µg/L	No	3	B+
107	Placentia	10.0 µg/L	No	0	B+
108	Mountain House	10.0 µg/L	No	1	A+
109	Newhall	9.9 µg/L	No	1	B+
110	San Diego	9.8 µg/L	No	43	F
111	San Clemente	9.7 µg/L	No	3	A-
112	La Mesa	9.7 µg/L	No	0	A+
113	Laguna Beach	9.6 µg/L	No	2	B
114	Rowland Heights	9.5 µg/L	No	0	B+
115	Spring Valley	9.4 µg/L	No	4	B
116	Corcoran	9.4 µg/L	No	3	A
117	Quartz Hill	9.4 µg/L	No	1	A-
118	Fremont	9.4 µg/L	No	3	B-
119	Healdsburg	9.4 µg/L	No	12	B+
120	South San Francisco	9.3 µg/L	No	2	A
121	Irvine	9.2 µg/L	No	84	F
122	Lake Forest	9.0 µg/L	No	38	B-
123	Imperial Beach	8.9 µg/L	No	1	A
124	Hawthorne	8.8 µg/L	No	3	B
125	Santa Maria	8.7 µg/L	No	36	F
126	Fallbrook	8.5 µg/L	No	3	A
127	Seal Beach	8.3 µg/L	No	0	A-
128	Los Banos	8.2 µg/L	No	29	B
129	Petaluma	8.1 µg/L	No	2	B
130	Nipomo	8.1 µg/L	No	1	A
131	San Bruno	8.1 µg/L	No	0	A+
132	Fontana	8.1 µg/L	No	0	A-
133	Inglewood	8.0 µg/L	No	3	A-
134	Laguna Hills	8.0 µg/L	No	1	B+
135	Moorpark	7.9 µg/L	No	1	A-
136	Rancho Cucamonga	7.9 µg/L	No	0	B+
137	Ontario	7.8 µg/L	No	1	B+
138	Rancho Cordova	7.8 µg/L	No	115	F
139	Chino	7.7 µg/L	No	9	B
140	Carlsbad	7.7 µg/L	No	0	A+
141	Pomona	7.7 µg/L	No	6	C+
142	Discovery Bay	7.6 µg/L	No	3	A+
143	Lodi	7.6 µg/L	No	16	C+
144	Rancho Santa Margarita	7.2 µg/L	No	0	A
145	Beverly Hills	7.2 µg/L	No	18	B
146	Hanford	7.2 µg/L	No	197	D+
147	Lakewood	7.1 µg/L	No	1	A-
148	Valley Center	7.0 µg/L	No	15	F
149	Lakeside	7.0 µg/L	No	0	A-
150	Huntington Beach	6.9 µg/L	No	5	C-
151	Chino Hills	6.8 µg/L	No	2	A
152	Oxnard	6.8 µg/L	No	49	F
153	Mckinleyville	6.8 µg/L	No	2	A-
154	Covina	6.7 µg/L	No	10	B
155	Eureka	6.7 µg/L	No	3	A-
156	Santee	6.7 µg/L	No	14	B
157	Lebec	6.7 µg/L	No	42	C
158	Concord	6.6 µg/L	No	19	B-
159	El Segundo	6.5 µg/L	No	0	A-
160	Ramona	6.5 µg/L	No	36	C
161	La Habra	6.4 µg/L	No	0	A-
162	Sonoma	6.4 µg/L	No	5	B-
163	Santa Fe Springs	6.3 µg/L	No	1	B+
164	Ukiah	6.2 µg/L	No	14	C+
165	San Dimas	6.2 µg/L	No	6	B-
166	Edwards Afb	6.2 µg/L	No	8	A-
167	Glendale	6.2 µg/L	No	0	A-
168	Calabasas	6.1 µg/L	No	14	A-
169	Rialto	6.0 µg/L	No	6	B+
170	Lomita	6.0 µg/L	No	1	A-
171	Los Angeles	6.0 µg/L	No	94	F
172	Westlake Village	5.9 µg/L	No	8	F
173	Carmichael	5.9 µg/L	No	1	B+
174	Corona	5.9 µg/L	No	81	D
175	Simi Valley	5.8 µg/L	No	3	A
176	San Marcos	5.8 µg/L	No	27	D
177	Thousand Oaks	5.8 µg/L	No	1	A
178	Soquel	5.7 µg/L	No	1	A
179	Montclair	5.5 µg/L	No	0	B+
180	Fullerton	5.5 µg/L	No	8	B
181	Pittsburg	5.5 µg/L	No	0	A
182	Torrance	5.4 µg/L	No	0	A-
183	Pasadena	5.4 µg/L	No	92	F
184	Perris	5.3 µg/L	No	0	A
185	Pleasanton	5.3 µg/L	No	3	B-
186	Woodland	5.3 µg/L	No	52	F
187	Upland	5.3 µg/L	No	4	B+
188	Palmdale	5.2 µg/L	No	15	C+
189	Temecula	5.2 µg/L	No	12	C+
190	Mendota	5.1 µg/L	No	3	A
191	Glendora	5.1 µg/L	No	0	A-
192	Oakley	5.1 µg/L	No	60	D
193	Alhambra	5.0 µg/L	No	7	A-
194	Arcata	5.0 µg/L	No	3	A
195	Alpine	5.0 µg/L	No	25	C-
196	Lake Elsinore	5.0 µg/L	No	8	A
197	Davis	5.0 µg/L	No	47	B+
198	Antioch	5.0 µg/L	No	3	A
199	Altadena	4.8 µg/L	No	2	B+
200	Brentwood	4.8 µg/L	No	91	F
201	Camp Pendleton	4.8 µg/L	No	13	B
202	Adelanto	4.8 µg/L	No	13	C
203	San Jacinto	4.7 µg/L	No	9	B
204	Orange	4.7 µg/L	No	3	B
205	Compton	4.6 µg/L	No	8	B
206	Cotati	4.5 µg/L	No	9	A-
207	Camarillo	4.3 µg/L	No	4	B
208	Rosemead	4.3 µg/L	No	17	C-
209	El Verano	4.1 µg/L	No	0	B+
210	Norwalk	4.0 µg/L	No	1	A-
211	Whittier	3.9 µg/L	No	4	C+
212	Huntington Park	3.9 µg/L	No	3	B+
213	Lompoc	3.7 µg/L	No	18	C
214	Marysville	3.6 µg/L	No	11	B+
215	Anaheim	3.6 µg/L	No	8	C+
216	Temescal Valley	3.5 µg/L	No	2	A
217	Brea	3.5 µg/L	No	0	A
218	Buena Park	3.5 µg/L	No	1	B+
219	Jurupa Valley	3.4 µg/L	No	62	B
220	Riverside	3.3 µg/L	No	13	C
221	Pala	3.3 µg/L	No	30	C-
222	Costa Mesa	3.1 µg/L	No	2	A-
223	Fresno	3.0 µg/L	No	523	F
224	San Joaquin	3.0 µg/L	No	13	A
225	Signal Hill	3.0 µg/L	No	6	B
226	Santa Ana	2.9 µg/L	No	8	C
227	Santa Rosa	2.9 µg/L	No	177	F
228	Cutten	2.9 µg/L	No	5	A+
229	Delano	2.8 µg/L	No	67	B
230	Port Hueneme	2.7 µg/L	No	0	B+
231	Scotts Valley	2.6 µg/L	No	11	B-
232	Bell Gardens	2.4 µg/L	No	0	B
233	Martinez	2.4 µg/L	No	0	A
234	Montebello	2.3 µg/L	No	5	B
235	Newport Beach	2.3 µg/L	No	4	B+
236	Santa Monica	2.2 µg/L	No	0	B
237	Tustin	2.1 µg/L	No	8	B
238	Windsor	2.0 µg/L	No	2	A+
239	Arcadia	2.0 µg/L	No	2	B
240	Rohnert Park	1.9 µg/L	No	21	F
241	Mcfarland	1.9 µg/L	No	42	C+
242	Palm Desert	1.9 µg/L	No	12	C+
243	Fortuna	1.8 µg/L	No	7	B-
244	Santa Paula	1.8 µg/L	No	5	A-
245	Apple Valley	1.7 µg/L	No	57	D
246	Norco	1.7 µg/L	No	39	F
247	Shafter	1.7 µg/L	No	25	A-
248	Fort Irwin	1.6 µg/L	No	60	B+
249	Downey	1.6 µg/L	No	14	B
250	Palm Springs	1.6 µg/L	No	16	B
251	Truckee	1.6 µg/L	No	7	A-
252	Watsonville	1.6 µg/L	No	74	F
253	Sierra Madre	1.5 µg/L	No	5	A
254	Marina	1.5 µg/L	No	4	A+
255	Burbank	1.5 µg/L	No	1	A-
256	Pico Rivera	1.5 µg/L	No	4	B
257	Bloomington	1.5 µg/L	No	1	A
258	Hemet	1.4 µg/L	No	31	B-
259	Cerritos	1.3 µg/L	No	0	B
260	La Habra Heights	1.3 µg/L	No	0	A
261	Greenfield	1.3 µg/L	No	17	B
262	La Palma	1.3 µg/L	No	0	A-
263	Westminster	1.2 µg/L	No	2	A-
264	Yucca Valley	1.2 µg/L	No	7	A-
265	Soledad	1.2 µg/L	No	28	C+
266	Fillmore	1.2 µg/L	No	13	B-
267	San Fernando	1.2 µg/L	No	1	A+
268	Lynwood	1.1 µg/L	No	0	B+
269	Paramount	1.1 µg/L	No	0	A-
270	Colton	1.1 µg/L	No	5	B-
271	Olivehurst	1.0 µg/L	No	2	A
272	Monrovia	1.0 µg/L	No	0	B+
273	Patterson	1.0 µg/L	No	35	B+
274	San Bernardin0	0.9 µg/L	No	0	A-
275	Gilroy	0.9 µg/L	No	28	C+
276	Newman	0.9 µg/L	No	3	A-
277	South Gate	0.9 µg/L	No	2	B
278	Ceres	0.9 µg/L	No	129	F
279	Oakhurst	0.8 µg/L	No	198	D
280	California City	0.8 µg/L	No	22	A-
281	Felton	0.8 µg/L	No	21	C
282	Cudahy	0.8 µg/L	No	3	B+
283	Pauma Valley	0.8 µg/L	No	88	F
284	Ridgecrest	0.8 µg/L	No	26	A-
285	Farmersville	0.8 µg/L	No	20	B+
286	Victorville	0.7 µg/L	No	1	B+
287	Loma Linda	0.7 µg/L	No	3	A
288	Grand Terrace	0.7 µg/L	No	1	B
289	Livingston	0.7 µg/L	No	29	C-
290	Salinas	0.7 µg/L	No	639	F
291	Monterey Park	0.7 µg/L	No	1	B
292	Herlong	0.7 µg/L	No	0	A-
293	Wasco	0.7 µg/L	No	26	B+
294	Garden Grove	0.6 µg/L	No	2	B
295	Joshua Tree	0.6 µg/L	No	3	A-
296	Phelan	0.6 µg/L	No	0	B+
297	Sanger	0.6 µg/L	No	16	C
298	Lamont	0.5 µg/L	No	40	B+
299	Vernon	0.5 µg/L	No	3	A
300	Parlier	0.5 µg/L	No	14	A-
301	South Pasadena	0.4 µg/L	No	5	A
302	Fountain Valley	0.4 µg/L	No	0	A
303	San Bernardino	0.4 µg/L	No	192	F
304	El Monte	0.3 µg/L	No	79	F
305	29 Palms	0.3 µg/L	No	3	B
306	Beaumont	0.3 µg/L	No	2	A-
307	Arvin	0.3 µg/L	No	81	C+
308	Desert Hot Springs	0.3 µg/L	No	4	A
309	Atwater	0.3 µg/L	No	3	B+
310	Banning	0.2 µg/L	No	15	B-
311	Rosamond	0.2 µg/L	No	205	F
312	Big Bear City	0.2 µg/L	No	1	A
313	Exeter	0.2 µg/L	No	41	B
314	Twentynine Palms	0.2 µg/L	No	70	B+
315	Indio	0.2 µg/L	No	12	F
316	Elk Grove	0.2 µg/L	No	28	C
317	Galt	0.2 µg/L	No	27	B+
318	Tulare	0.2 µg/L	No	61	C-
319	Madera	0.2 µg/L	No	564	D
320	Midway City	0.2 µg/L	No	11	A
321	Porterville	0.2 µg/L	No	74	F
322	Baldwin Park	0.1 µg/L	No	1	A
323	Bellflower	0.1 µg/L	No	0	B+
324	Ripon	0.1 µg/L	No	10	A-
325	Hesperia	0.1 µg/L	No	2	B
326	South Lake Tahoe	0.1 µg/L	No	15	C
327	Oakdale	0.1 µg/L	No	34	C-
328	Merced	0.1 µg/L	No	9	C+
329	Coachella	0.1 µg/L	No	11	C-
330	Reedley	0.0 µg/L	No	12	B-
331	Riverbank	0.0 µg/L	No	75	D
332	Anderson	0.0 µg/L	No	14	C-
333	Chowchilla	0.0 µg/L	No	25	A-
334	Kerman	0.0 µg/L	No	13	B
335	Rio Linda	0.0 µg/L	No	2	A-
336	Colusa	0.0 µg/L	No	6	C-
337	Dinuba	0.0 µg/L	No	24	A-

FAQ

Frequently asked questions about haa5 in California

What is HAA5 and why does it appear in California tap water?

HAA5 (haloacetic acids) are disinfection byproducts that form when chlorine reacts with naturally occurring organic matter in source water. They are a normal byproduct of the disinfection process that makes water safe to drink. No cities in California currently exceed the 60 µg/L EPA MCL. The state average is 9.0 µg/L.

How can I reduce HAA5 exposure from California drinking water?

Activated carbon filters (granular or block) effectively reduce HAA5. Refrigerator filters and under-sink carbon systems are convenient options. Unlike lead or PFAS, HAA5 levels can also be reduced by letting water stand in an open container, as some species evaporate. Boiling does NOT remove HAA5 and can concentrate them by reducing water volume.

Which California cities have the highest HAA5 levels?

The cities with the highest average HAA5 concentrations in California are: Shasta (47.7 µg/L), Lindsay (40.8 µg/L), Sonora (39.6 µg/L), Burlingame (36.8 µg/L), American Canyon (36.0 µg/L). Note: this data is from UCMR 4 testing (2018–2020) and may not reflect current levels.

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