HAA5 Contamination

HAA5 in Washington Drinking Water

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

Cities Tested

Exceeds Limit

% Exceeds Limit

13.2 µg/L

State Avg

▼ 1% vs national

vs National

261

Health Violations

Analysis

HAA5 in Washington: what the data shows

Washington has 92 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 13.2 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

Washington

0 of 92 cities

← ▼ 1% below national rate (better)

National avg

23 of 4420 cities

City Map

HAA5 data across Washington

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 Washington

Highest HAA5 levels (µg/L)

All Cities

All Washington cities ranked by haa5 level

#	City	Level	Exceeds?	Violations	Grade
1	Hoquiam	46.6 µg/L	No	6	B-
2	Chehalis	40.8 µg/L	No	12	F
3	Monroe	38.5 µg/L	No	4	C
4	Walla Walla	37.6 µg/L	No	84	D
5	Everett	36.3 µg/L	No	16	D
6	Mountlake Terrace	36.0 µg/L	No	0	B+
7	Mukilteo	35.8 µg/L	No	0	A-
8	Lynnwood	35.3 µg/L	No	0	B-
9	Edmonds	32.7 µg/L	No	0	A-
10	Issaquah	32.1 µg/L	No	10	C-
11	Bremerton	30.2 µg/L	No	13	C
12	Snohomish	30.1 µg/L	No	11	D
13	Bothell	29.8 µg/L	No	7	F
14	Richland	28.8 µg/L	No	7	C+
15	Renton	27.4 µg/L	No	11	D+
16	Newcastle	27.2 µg/L	No	1	A
17	Port Townsend	26.9 µg/L	No	15	F
18	Kenmore	26.3 µg/L	No	0	B-
19	Bellevue	25.1 µg/L	No	2	A
20	Mercer Island	24.3 µg/L	No	1	A-
21	Pasco	24.2 µg/L	No	137	D
22	Seattle	24.1 µg/L	No	138	F
23	Maple Valley	23.8 µg/L	No	7	C+
24	Shoreline	23.6 µg/L	No	0	A-
25	Duvall	23.5 µg/L	No	0	A-
26	Marysville	22.8 µg/L	No	12	D
27	Burien	22.7 µg/L	No	1	B+
28	Yakima	22.5 µg/L	No	162	F
29	Redmond	21.1 µg/L	No	4	B-
30	Woodinville	20.4 µg/L	No	1	A-
31	Kirkland	19.1 µg/L	No	4	D+
32	Kent	18.9 µg/L	No	31	F
33	Nas Whidbey Island	18.2 µg/L	No	0	A+
34	Longview	17.9 µg/L	No	0	B+
35	Vashon	17.4 µg/L	No	24	F
36	Silverdale	16.5 µg/L	No	17	F
37	Kelso	16.4 µg/L	No	15	F
38	Kennewick	16.1 µg/L	No	78	F
39	Oak Harbor	14.8 µg/L	No	105	F
40	Mount Vernon	13.1 µg/L	No	191	F
41	Sammamish	12.7 µg/L	No	6	C-
42	Bellingham	12.6 µg/L	No	54	F
43	Arlington	11.8 µg/L	No	83	F
44	West Richland	11.3 µg/L	No	99	F
45	Yelm	11.2 µg/L	No	12	D+
46	Federal Way	10.3 µg/L	No	2	B
47	Sequim	8.1 µg/L	No	64	F
48	Lynden	7.5 µg/L	No	235	F
49	Aberdeen	7.5 µg/L	No	10	D
50	Bainbridge Island	7.5 µg/L	No	3	A
51	Stanwood	4.8 µg/L	No	31	D
52	Port Orchard	4.7 µg/L	No	753	F
53	Washougal	4.6 µg/L	No	2	B+
54	Tacoma	4.2 µg/L	No	232	F
55	Lacey	4.0 µg/L	No	125	F
56	Port Angeles	3.4 µg/L	No	19	F
57	Poulsbo	3.4 µg/L	No	95	F
58	Ferndale	3.0 µg/L	No	110	F
59	Olympia	2.7 µg/L	No	66	F
60	Buckley	2.5 µg/L	No	5	D+
61	Cheney	2.5 µg/L	No	5	A-
62	Moxee	2.3 µg/L	No	2	B
63	Snoqualime	2.3 µg/L	No	4	A-
64	Camas	2.2 µg/L	No	2	C
65	Spanaway	2.2 µg/L	No	9	C+
66	Wenatchee	2.0 µg/L	No	41	D
67	Shelton	1.9 µg/L	No	158	F
68	Grandview	1.8 µg/L	No	5	D+
69	East Wenatchee	1.7 µg/L	No	19	B
70	Puyallup	1.7 µg/L	No	124	F
71	Moses Lake	1.4 µg/L	No	132	F
72	Enumclaw	1.3 µg/L	No	1	B+
73	Centralia	1.3 µg/L	No	5	B-
74	Joint Base Lewis-Mcchord	1.0 µg/L	No	3	B+
75	Tumwater	0.9 µg/L	No	24	D+
76	Vancouver	0.8 µg/L	No	36	F
77	Lakewood	0.8 µg/L	No	5	B+
78	Clarkston	0.7 µg/L	No	16	B+
79	Spokane	0.7 µg/L	No	56	F
80	Spokane Valley	0.6 µg/L	No	10	C-
81	Pullman	0.6 µg/L	No	0	B+
82	Selah	0.5 µg/L	No	4	B
83	Dupont	0.5 µg/L	No	0	A
84	Clinton	0.5 µg/L	No	8	C
85	Auburn	0.5 µg/L	No	18	D+
86	Battle Ground	0.4 µg/L	No	12	B-
87	Sunnyside	0.3 µg/L	No	2	A-
88	Westport	0.1 µg/L	No	4	D+
89	Ellensburg	0.1 µg/L	No	19	D
90	Greenacres	0.0 µg/L	No	12	B+
91	Fircrest	0.0 µg/L	No	4	A-
92	Tekoa	0.0 µg/L	No	5	C

FAQ

Frequently asked questions about haa5 in Washington

What is HAA5 and why does it appear in Washington 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 Washington currently exceed the 60 µg/L EPA MCL. The state average is 13.2 µg/L.

How can I reduce HAA5 exposure from Washington 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 Washington cities have the highest HAA5 levels?

The cities with the highest average HAA5 concentrations in Washington are: Hoquiam (46.6 µg/L), Chehalis (40.8 µg/L), Monroe (38.5 µg/L), Walla Walla (37.6 µg/L), Everett (36.3 µg/L). Note: this data is from UCMR 4 testing (2018–2020) and may not reflect current levels.

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