Chlorate Contamination

Chlorate in Texas Drinking Water

Ranked by max chlorate detected (µg/L) · UCMR 3 data (2013–2015) · Data from EPA SDWIS & UCMR

185

Cities Tested

115

Over HA

62%

% Over HA

583.7 µg/L

State Avg

▲ 3% vs national

vs National

900

Health Violations

Analysis

Chlorate in Texas: what the data shows

Texas has 185 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 115 of those cities. The state average max detected level is 583.7 µg/L. Chlorate is a disinfection byproduct that forms when chlorine dioxide or hypochlorite solutions are used to disinfect drinking water. It is most common in systems that use chlorine dioxide for taste-and-odor control or that store hypochlorite for extended periods. There is no federal MCL — the EPA lifetime health advisory is 210 µg/L. Chlorate can interfere with thyroid function by blocking iodide uptake, an effect of particular concern for pregnant women, infants, and people with thyroid conditions. Reverse osmosis and ion exchange (anion-specific) are effective at removing chlorate; standard activated carbon filters provide only modest reduction.

Comparison

Cities exceeding 210 µg/L EPA lifetime HA (no MCL)

Texas

62%

115 of 185 cities

→ ▲ 3% above national rate (worse)

National avg

59%

1866 of 3166 cities

City Map

Chlorate data across Texas

Each dot is a city with UCMR 3 chlorate testing data. Cities where chlorate exceeds the 210 µg/L EPA lifetime health advisory are highlighted. Size reflects population served.

Worst Offenders

Top 10 cities by chlorate level in Texas

Highest Chlorate levels (µg/L)

All Cities

All Texas cities ranked by chlorate level

#	City	Level	Over HA?	Violations	Grade
1	Houston	13600.0 µg/L	Over HA	929	F
2	Austin	4510.0 µg/L	Over HA	1288	F
3	Tyler	4080.0 µg/L	Over HA	53	F
4	Bonham	3242.5 µg/L	Over HA	30	B+
5	Montague	2900.0 µg/L	Over HA	5	D
6	Cypress	2080.0 µg/L	Over HA	624	F
7	Stamford	2013.7 µg/L	Over HA	76	D
8	Weslaco	1500.0 µg/L	Over HA	2	C+
9	Greenville	1470.0 µg/L	Over HA	8	C
10	Frisco	1460.0 µg/L	Over HA	3	B
11	Terrell	1430.0 µg/L	Over HA	21	F
12	Richardson	1410.0 µg/L	Over HA	30	F
13	Georgetown	1400.0 µg/L	Over HA	3	F
14	Mesquite	1400.0 µg/L	Over HA	0	B+
15	The Colony	1400.0 µg/L	Over HA	2	A-
16	Allen	1300.0 µg/L	Over HA	0	A-
17	Wylie	1250.0 µg/L	Over HA	2	B-
18	Alamo	1240.0 µg/L	Over HA	7	B+
19	Garland	1220.0 µg/L	Over HA	0	A-
20	Lubbock	1200.0 µg/L	Over HA	1231	F
21	Plano	1170.0 µg/L	Over HA	5	A-
22	Forney	1160.0 µg/L	Over HA	10	B-
23	Little Elm	1130.0 µg/L	Over HA	2	C
24	Mckinney	1100.0 µg/L	Over HA	0	A-
25	San Marcos	1100.0 µg/L	Over HA	56	C-
26	Fate	1100.0 µg/L	Over HA	0	B
27	San Benito	1100.0 µg/L	Over HA	16	B+
28	Diboll	1100.0 µg/L	Over HA	9	B-
29	Friendswood	1080.0 µg/L	Over HA	0	B+
30	Murphy	1050.0 µg/L	Over HA	0	B+
31	Pearland	1040.0 µg/L	Over HA	14	F
32	Waxahachie	955.0 µg/L	Over HA	70	D+
33	College Station	870.0 µg/L	Over HA	2	B-
34	Rio Grande	840.0 µg/L	Over HA	6	B
35	Parker	840.0 µg/L	Over HA	0	A-
36	Coldspring	825.0 µg/L	Over HA	1	B
37	Red Oak	811.0 µg/L	Over HA	10	B+
38	Grand Prairie	807.0 µg/L	Over HA	10	F
39	De Leon	795.7 µg/L	Over HA	45	F
40	Stafford	790.0 µg/L	Over HA	1	A-
41	Lockhart	789.0 µg/L	Over HA	0	A-
42	Benbrook	764.0 µg/L	Over HA	0	B
43	Rockwall	756.0 µg/L	Over HA	4	D
44	Zapata	722.0 µg/L	Over HA	75	D
45	Fort Worth	720.0 µg/L	Over HA	25	F
46	Post	720.0 µg/L	Over HA	28	F
47	Sachse	715.0 µg/L	Over HA	1	A
48	Leander	706.0 µg/L	Over HA	5	F
49	Lake Dallas	695.0 µg/L	Over HA	2	B-
50	Mcallen	668.0 µg/L	Over HA	0	A
51	Mission	665.0 µg/L	Over HA	23	C-
52	Royse City	658.0 µg/L	Over HA	6	C+
53	Rowlett	631.0 µg/L	Over HA	0	A-
54	Flower Mound	618.0 µg/L	Over HA	2	C
55	Corinth	613.0 µg/L	Over HA	2	A-
56	Highland Village	612.0 µg/L	Over HA	3	A-
57	Midlothian	600.0 µg/L	Over HA	12	B
58	Edinburg	582.0 µg/L	Over HA	12	C-
59	Lewisville	576.0 µg/L	Over HA	1	C+
60	Temple	570.0 µg/L	Over HA	31	C-
61	Coupland	545.0 µg/L	Over HA	6	C
62	Mineral Wells	543.0 µg/L	Over HA	7	C-
63	White Settlement	527.0 µg/L	Over HA	13	C+
64	Donna	520.0 µg/L	Over HA	6	B
65	Denison	508.0 µg/L	Over HA	24	F
66	Marion	484.0 µg/L	Over HA	2	B-
67	Niederwald	483.0 µg/L	Over HA	6	B-
68	El Paso	480.0 µg/L	Over HA	192	F
69	Seguin	480.0 µg/L	Over HA	42	F
70	Del Rio	471.0 µg/L	Over HA	117	F
71	Round Rock	467.0 µg/L	Over HA	17	F
72	Denton	440.0 µg/L	Over HA	3	F
73	Pharr	434.0 µg/L	Over HA	0	A-
74	Portland	430.0 µg/L	Over HA	2	B+
75	Roma	419.0 µg/L	Over HA	40	F
76	Brenham	400.0 µg/L	Over HA	20	F
77	Sulphur Springs	382.0 µg/L	Over HA	18	C
78	Joshua	381.0 µg/L	Over HA	2	C-
79	Abilene	374.5 µg/L	Over HA	46	F
80	Keller	372.0 µg/L	Over HA	1	B+
81	Victoria	369.2 µg/L	Over HA	28	F
82	Rockport	363.0 µg/L	Over HA	20	B-
83	Bedford	362.0 µg/L	Over HA	0	B+
84	Livingston	351.0 µg/L	Over HA	398	F
85	Pflugerville	349.0 µg/L	Over HA	19	C+
86	Rio Hondo	347.0 µg/L	Over HA	70	F
87	San Juan	341.0 µg/L	Over HA	4	B+
88	Ingleside	340.0 µg/L	Over HA	3	D+
89	Mansfield	331.0 µg/L	Over HA	0	A-
90	Sugar Land	330.0 µg/L	Over HA	4	F
91	Amarillo	326.0 µg/L	Over HA	26	F
92	Angleton	325.0 µg/L	Over HA	47	F
93	Southlake	305.0 µg/L	Over HA	3	B
94	Hutto	303.0 µg/L	Over HA	17	B
95	Weatherford	291.0 µg/L	Over HA	140	F
96	Granbury	282.0 µg/L	Over HA	28	F
97	White Oak	280.0 µg/L	Over HA	7	B
98	Canyon	278.0 µg/L	Over HA	5	F
99	Comanche	270.0 µg/L	Over HA	42	D
100	Freeport	262.0 µg/L	Over HA	209	F
101	North Richland Hills	260.0 µg/L	Over HA	1	B+
102	Brownsville	257.0 µg/L	Over HA	5	C+
103	Huntsville	257.0 µg/L	Over HA	128	F
104	Port Arthur	252.0 µg/L	Over HA	8	B+
105	West Columbia	252.0 µg/L	Over HA	2	C+
106	Alice	250.0 µg/L	Over HA	103	F
107	Holliday	250.0 µg/L	Over HA	4	B+
108	Kempner	249.0 µg/L	Over HA	19	B-
109	Robstown	244.0 µg/L	Over HA	31	F
110	Beeville	241.0 µg/L	Over HA	46	F
111	Snyder	228.0 µg/L	Over HA	12	B-
112	Canyon Lake	223.0 µg/L	Over HA	39	F
113	Midland	220.0 µg/L	Over HA	231	F
114	Dickinson	219.0 µg/L	Over HA	8	F
115	Dallas	214.0 µg/L	Over HA	102	F
116	Corpus Christi	210.0 µg/L	No	13	B
117	La Marque	210.0 µg/L	No	3	B
118	Texas City	200.0 µg/L	No	4	B
119	Lancaster	191.0 µg/L	No	5	B-
120	Lake Jackson	190.0 µg/L	No	6	D
121	Sheppard Afb	190.0 µg/L	No	3	A-
122	Wichita Falls	180.0 µg/L	No	823	F
123	Santa Fe	170.0 µg/L	No	25	F
124	League City	163.0 µg/L	No	67	F
125	Burkburnett	162.0 µg/L	No	45	B-
126	Pampa	160.0 µg/L	No	7	B
127	Friona	160.0 µg/L	No	10	B
128	Port Isabel	153.0 µg/L	No	24	B+
129	Gainesville	140.7 µg/L	No	13	D
130	Humble	140.0 µg/L	No	1	B+
131	Sweetwater	136.0 µg/L	No	8	B
132	Galveston	128.0 µg/L	No	2	B+
133	Hemphill	125.0 µg/L	No	115	F
134	Marshall	123.0 µg/L	No	46	F
135	Crowley	119.0 µg/L	No	2	C+
136	Brownwood	113.0 µg/L	No	12	A-
137	Haltom City	111.0 µg/L	No	2	B
138	Mount Pleasant	102.0 µg/L	No	2	A-
139	Longview	99.4 µg/L	No	20	F
140	Stephenville	85.0 µg/L	No	39	F
141	Irving	80.0 µg/L	No	9	C
142	Universal City	79.1 µg/L	No	0	B+
143	Rosenberg	79.0 µg/L	No	1	C-
144	Burleson	78.5 µg/L	No	9	B+
145	Duncanville	73.5 µg/L	No	5	B+
146	Cedar Hill	73.4 µg/L	No	4	A-
147	San Antonio	64.0 µg/L	No	25	F
148	Glenn Heights	62.9 µg/L	No	3	C-
149	Paris	62.4 µg/L	No	15	B+
150	Kyle	61.2 µg/L	No	5	A-
151	Desoto	59.0 µg/L	No	2	A-
152	Athens	56.5 µg/L	No	95	F
153	Colleyville	50.0 µg/L	No	1	B+
154	Clint	49.6 µg/L	No	2	B
155	Grapevine	49.4 µg/L	No	0	A-
156	Taylor	49.2 µg/L	No	6	A-
157	Cooper	48.0 µg/L	No	10	B
158	Bastrop	43.4 µg/L	No	31	F
159	Douglass	43.0 µg/L	No	4	B
160	Menard	43.0 µg/L	No	1	A-
161	Kilgore	41.1 µg/L	No	26	F
162	Trophy Club	40.1 µg/L	No	0	A+
163	Progreso	38.4 µg/L	No	52	D+
164	Richland Hills	37.4 µg/L	No	2	A-
165	Garden Ridge	36.3 µg/L	No	0	A-
166	San Angelo	33.0 µg/L	No	40	F
167	Lavernia	31.8 µg/L	No	0	A-
168	Tool	31.5 µg/L	No	6	A-
169	Texarkana	30.4 µg/L	No	17	F
170	Blue Ridge	29.7 µg/L	No	1	B
171	Gilmer	29.5 µg/L	No	7	C
172	Crockett	29.0 µg/L	No	47	F
173	Hurst	28.5 µg/L	No	1	A-
174	Plainview	28.0 µg/L	No	25	F
175	Coppell	26.6 µg/L	No	0	A-
176	Carrollton	25.7 µg/L	No	0	A-
177	Sherman	24.1 µg/L	No	2	B+
178	Levelland	22.7 µg/L	No	168	F
179	Mabank	22.3 µg/L	No	66	D
180	Borger	22.3 µg/L	No	1	C-
181	Beaumont	22.0 µg/L	No	42	F
182	Pleasanton	21.8 µg/L	No	7	B+
183	Robinson	21.2 µg/L	No	2	A-
184	Kingsville	21.1 µg/L	No	45	D+
185	Odessa	21.0 µg/L	No	225	F

FAQ

Frequently asked questions about chlorate in Texas

Is chlorate in Texas tap water dangerous?

Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 115 cities in Texas exceed this level. Chlorate can interfere with thyroid iodide uptake, which is a particular concern for infants, pregnant women, and people with hypothyroidism.

Where does chlorate in Texas water come from?

Chlorate is a byproduct of chlorine-based disinfectants — particularly chlorine dioxide and hypochlorite (bleach) solutions. Levels tend to be higher in systems that use chlorine dioxide for taste-and-odor treatment or store sodium hypochlorite at high concentrations or for long periods. Levels vary seasonally with disinfectant use.

How can I reduce chlorate exposure?

Reverse osmosis is the most effective home treatment for chlorate, typically removing 80–95%. Anion exchange systems also work but require regeneration. Standard activated carbon filters provide only limited chlorate reduction. Boiling does NOT remove chlorate.

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