HAA5 Contamination

HAA5 in California Drinking Water

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

339

Cities Tested

Exceeds Limit

% Exceeds Limit

9.0 µg/L

State Avg

▼ 1% vs national

vs National

624

Health Violations

Analysis

HAA5 in California: what the data shows

California has 339 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 339 cities

← ▼ 1% below national rate (better)

National avg

23 of 4420 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	San Juan Capistrano	5.0 µg/L	No	5	B+
200	Altadena	4.8 µg/L	No	2	B+
201	Brentwood	4.8 µg/L	No	91	F
202	Camp Pendleton	4.8 µg/L	No	13	B
203	Adelanto	4.8 µg/L	No	13	C
204	San Jacinto	4.7 µg/L	No	9	B
205	Orange	4.7 µg/L	No	3	B
206	Compton	4.6 µg/L	No	8	B
207	Cotati	4.5 µg/L	No	9	A-
208	Camarillo	4.3 µg/L	No	4	B
209	Rosemead	4.3 µg/L	No	17	C-
210	El Verano	4.1 µg/L	No	0	B+
211	Norwalk	4.0 µg/L	No	1	A-
212	Whittier	3.9 µg/L	No	4	C+
213	Huntington Park	3.9 µg/L	No	3	B+
214	Lompoc	3.7 µg/L	No	18	C
215	Marysville	3.6 µg/L	No	11	B+
216	Anaheim	3.6 µg/L	No	8	C+
217	Temescal Valley	3.5 µg/L	No	2	A
218	Brea	3.5 µg/L	No	0	A
219	Buena Park	3.5 µg/L	No	1	B+
220	Jurupa Valley	3.4 µg/L	No	62	B
221	Riverside	3.3 µg/L	No	13	C
222	Pala	3.3 µg/L	No	30	C-
223	Costa Mesa	3.1 µg/L	No	2	A-
224	Fresno	3.0 µg/L	No	523	F
225	San Joaquin	3.0 µg/L	No	13	A
226	Signal Hill	3.0 µg/L	No	6	B
227	Santa Ana	2.9 µg/L	No	8	C
228	Santa Rosa	2.9 µg/L	No	177	F
229	Cutten	2.9 µg/L	No	5	A+
230	Delano	2.8 µg/L	No	67	B
231	Port Hueneme	2.7 µg/L	No	0	B+
232	Scotts Valley	2.6 µg/L	No	11	B-
233	Bell Gardens	2.4 µg/L	No	0	B
234	Martinez	2.4 µg/L	No	0	A
235	Montebello	2.3 µg/L	No	5	B
236	Newport Beach	2.3 µg/L	No	4	B+
237	Santa Monica	2.2 µg/L	No	0	B
238	Tustin	2.1 µg/L	No	8	B
239	Windsor	2.0 µg/L	No	2	A+
240	Arcadia	2.0 µg/L	No	2	B
241	Rohnert Park	1.9 µg/L	No	21	F
242	Mcfarland	1.9 µg/L	No	42	C+
243	Palm Desert	1.9 µg/L	No	12	C+
244	Fortuna	1.8 µg/L	No	7	B-
245	Santa Paula	1.8 µg/L	No	5	A-
246	Apple Valley	1.7 µg/L	No	57	D
247	Norco	1.7 µg/L	No	39	F
248	Shafter	1.7 µg/L	No	25	A-
249	Fort Irwin	1.6 µg/L	No	60	B+
250	Downey	1.6 µg/L	No	14	B
251	Palm Springs	1.6 µg/L	No	16	B
252	Truckee	1.6 µg/L	No	7	A-
253	Watsonville	1.6 µg/L	No	74	F
254	Sierra Madre	1.5 µg/L	No	5	A
255	Marina	1.5 µg/L	No	4	A+
256	Burbank	1.5 µg/L	No	1	A-
257	Pico Rivera	1.5 µg/L	No	4	B
258	Bloomington	1.5 µg/L	No	1	A
259	Hemet	1.4 µg/L	No	31	B-
260	Morgan Hill	1.4 µg/L	No	92	F
261	Cerritos	1.3 µg/L	No	0	B
262	La Habra Heights	1.3 µg/L	No	0	A
263	Greenfield	1.3 µg/L	No	17	B
264	La Palma	1.3 µg/L	No	0	A-
265	Westminster	1.2 µg/L	No	2	A-
266	Yucca Valley	1.2 µg/L	No	7	A-
267	Soledad	1.2 µg/L	No	28	C+
268	Fillmore	1.2 µg/L	No	13	B-
269	San Fernando	1.2 µg/L	No	1	A+
270	Lynwood	1.1 µg/L	No	0	B+
271	Paramount	1.1 µg/L	No	0	A-
272	Colton	1.1 µg/L	No	5	B-
273	Olivehurst	1.0 µg/L	No	2	A
274	Monrovia	1.0 µg/L	No	0	B+
275	Patterson	1.0 µg/L	No	35	B+
276	San Bernardin0	0.9 µg/L	No	0	A-
277	Gilroy	0.9 µg/L	No	28	C+
278	Newman	0.9 µg/L	No	3	A-
279	South Gate	0.9 µg/L	No	2	B
280	Ceres	0.9 µg/L	No	129	F
281	Oakhurst	0.8 µg/L	No	198	D
282	California City	0.8 µg/L	No	22	A-
283	Felton	0.8 µg/L	No	21	C
284	Cudahy	0.8 µg/L	No	3	B+
285	Pauma Valley	0.8 µg/L	No	88	F
286	Ridgecrest	0.8 µg/L	No	26	A-
287	Farmersville	0.8 µg/L	No	20	B+
288	Victorville	0.7 µg/L	No	1	B+
289	Loma Linda	0.7 µg/L	No	3	A
290	Grand Terrace	0.7 µg/L	No	1	B
291	Livingston	0.7 µg/L	No	29	C-
292	Salinas	0.7 µg/L	No	639	F
293	Monterey Park	0.7 µg/L	No	1	B
294	Herlong	0.7 µg/L	No	0	A-
295	Wasco	0.7 µg/L	No	26	B+
296	Garden Grove	0.6 µg/L	No	2	B
297	Joshua Tree	0.6 µg/L	No	3	A-
298	Phelan	0.6 µg/L	No	0	B+
299	Sanger	0.6 µg/L	No	16	C
300	Lamont	0.5 µg/L	No	40	B+
301	Vernon	0.5 µg/L	No	3	A
302	Parlier	0.5 µg/L	No	14	A-
303	South Pasadena	0.4 µg/L	No	5	A
304	Fountain Valley	0.4 µg/L	No	0	A
305	San Bernardino	0.4 µg/L	No	192	F
306	El Monte	0.3 µg/L	No	79	F
307	29 Palms	0.3 µg/L	No	3	B
308	Beaumont	0.3 µg/L	No	2	A-
309	Arvin	0.3 µg/L	No	81	C+
310	Desert Hot Springs	0.3 µg/L	No	4	A
311	Atwater	0.3 µg/L	No	3	B+
312	Banning	0.2 µg/L	No	15	B-
313	Rosamond	0.2 µg/L	No	205	F
314	Big Bear City	0.2 µg/L	No	1	A
315	Exeter	0.2 µg/L	No	41	B
316	Twentynine Palms	0.2 µg/L	No	70	B+
317	Indio	0.2 µg/L	No	12	F
318	Elk Grove	0.2 µg/L	No	28	C
319	Galt	0.2 µg/L	No	27	B+
320	Tulare	0.2 µg/L	No	61	C-
321	Madera	0.2 µg/L	No	564	D
322	Midway City	0.2 µg/L	No	11	A
323	Porterville	0.2 µg/L	No	74	F
324	Baldwin Park	0.1 µg/L	No	1	A
325	Bellflower	0.1 µg/L	No	0	B+
326	Ripon	0.1 µg/L	No	10	A-
327	Hesperia	0.1 µg/L	No	2	B
328	South Lake Tahoe	0.1 µg/L	No	15	C
329	Oakdale	0.1 µg/L	No	34	C-
330	Merced	0.1 µg/L	No	9	C+
331	Coachella	0.1 µg/L	No	11	C-
332	Reedley	0.0 µg/L	No	12	B-
333	Riverbank	0.0 µg/L	No	75	D
334	Anderson	0.0 µg/L	No	14	C-
335	Chowchilla	0.0 µg/L	No	25	A-
336	Kerman	0.0 µg/L	No	13	B
337	Rio Linda	0.0 µg/L	No	2	A-
338	Colusa	0.0 µg/L	No	6	C-
339	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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