Chlorate Contamination

Chlorate in Ohio Drinking Water

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

Cities Tested

Over HA

53%

% Over HA

322.6 µg/L

State Avg

▼ 6% vs national

vs National

398

Health Violations

Analysis

Chlorate in Ohio: what the data shows

Ohio has 87 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 46 of those cities. The state average max detected level is 322.6 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)

Ohio

53%

46 of 87 cities

← ▼ 6% below national rate (better)

National avg

59%

1866 of 3166 cities

City Map

Chlorate data across Ohio

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 Ohio

Highest Chlorate levels (µg/L)

All Cities

All Ohio cities ranked by chlorate level

#	City	Level	Over HA?	Violations	Grade
1	Delaware	2100.0 µg/L	Over HA	5	B
2	Wapakoneta	1300.0 µg/L	Over HA	7	B
3	Cedarville	1250.0 µg/L	Over HA	1	B+
4	Bowling Green	1199.8 µg/L	Over HA	85	F
5	East Liverpool	1010.0 µg/L	Over HA	14	B
6	New Richmond	870.0 µg/L	Over HA	0	B-
7	Kent	854.0 µg/L	Over HA	36	F
8	Stow	808.0 µg/L	Over HA	4	C+
9	Tallmadge	759.0 µg/L	Over HA	1	B
10	Norton	702.0 µg/L	Over HA	17	A-
11	Celina	580.0 µg/L	Over HA	45	B-
12	Chagrin Falls	576.0 µg/L	Over HA	1	C
13	Chillicothe	565.5 µg/L	Over HA	0	B+
14	Ravenna	542.0 µg/L	Over HA	3	C
15	Jackson	541.5 µg/L	Over HA	11	B-
16	Quincy	476.0 µg/L	Over HA	0	A-
17	Gallipolis	452.2 µg/L	Over HA	3	B
18	Ashtabula	450.0 µg/L	Over HA	3	B+
19	Huber Heights	440.0 µg/L	Over HA	4	A-
20	Beavercreek	427.0 µg/L	Over HA	9	B+
21	Nevada	420.0 µg/L	Over HA	0	B+
22	Bellville	418.5 µg/L	Over HA	9	C-
23	Waterford	417.1 µg/L	Over HA	5	C+
24	Port Clinton	390.0 µg/L	Over HA	46	D+
25	Columbus	370.0 µg/L	Over HA	56	F
26	Portsmouth	356.0 µg/L	Over HA	1	B
27	Conneaut	353.0 µg/L	Over HA	6	B+
28	Warren	352.0 µg/L	Over HA	62	F
29	West Unity	339.4 µg/L	Over HA	0	B
30	Urbana	327.0 µg/L	Over HA	24	C+
31	Findlay	325.0 µg/L	Over HA	6	A-
32	Bexley	290.0 µg/L	Over HA	16	C
33	Jefferson	290.0 µg/L	Over HA	1	B
34	Attica	287.2 µg/L	Over HA	32	C-
35	Alliance	281.0 µg/L	Over HA	17	B+
36	Ashland	278.4 µg/L	Over HA	2	B+
37	Marion	270.0 µg/L	Over HA	9	B-
38	Vienna	270.0 µg/L	Over HA	9	B
39	Defiance	264.0 µg/L	Over HA	171	F
40	Painesville	242.0 µg/L	Over HA	0	B+
41	Zanesville	239.8 µg/L	Over HA	7	D+
42	Norwalk	237.0 µg/L	Over HA	12	B+
43	Trenton	217.0 µg/L	Over HA	10	B-
44	Steubenville	216.3 µg/L	Over HA	30	F
45	Monroe	215.0 µg/L	Over HA	2	B
46	Huron	214.0 µg/L	Over HA	13	C+
47	N Canton	210.0 µg/L	No	0	A-
48	Pickerington	204.3 µg/L	No	1	A-
49	Wooster	201.0 µg/L	No	14	F
50	Mcdermott	200.0 µg/L	No	2	A
51	Mentor	190.0 µg/L	No	6	B-
52	Newark	190.0 µg/L	No	6	B-
53	Hamilton	180.0 µg/L	No	5	B-
54	Sandusky	177.0 µg/L	No	6	A-
55	Sylvania	155.0 µg/L	No	0	A-
56	Streetsboro	155.0 µg/L	No	1	A+
57	Springboro	153.0 µg/L	No	4	B+
58	Cincinnati	150.0 µg/L	No	10	F
59	Aurora	148.0 µg/L	No	0	A-
60	Xenia	147.0 µg/L	No	1	A-
61	Franklin	136.0 µg/L	No	2	B+
62	Cleveland	120.0 µg/L	No	2	A-
63	Massillon	120.0 µg/L	No	13	D+
64	Toledo	111.0 µg/L	No	13	B
65	Lancaster	94.1 µg/L	No	6	B+
66	Maumee	92.7 µg/L	No	6	B-
67	Berea	89.2 µg/L	No	1	B+
68	Batavia	79.7 µg/L	No	2	B+
69	Lakewood	74.9 µg/L	No	0	B+
70	Fairfield	72.6 µg/L	No	9	B
71	Whitehouse	69.2 µg/L	No	8	B
72	Vandalia	65.0 µg/L	No	10	B+
73	Reading	62.3 µg/L	No	3	B
74	Bedford	60.3 µg/L	No	0	A
75	Medina	58.8 µg/L	No	15	C+
76	Camden	55.0 µg/L	No	1	B+
77	Pataskala	54.7 µg/L	No	4	B+
78	Lebanon	52.2 µg/L	No	28	D
79	Cuyahoga Falls	51.8 µg/L	No	3	B-
80	Mount Vernon	42.7 µg/L	No	3	B+
81	Norwood	42.0 µg/L	No	3	B+
82	Vermilion	41.0 µg/L	No	7	B+
83	Wilmington	37.9 µg/L	No	26	B
84	Lorain	37.8 µg/L	No	15	B+
85	Oregon	37.3 µg/L	No	1	B+
86	Ironton	34.9 µg/L	No	12	C-
87	Morrow	29.5 µg/L	No	7	B-

FAQ

Frequently asked questions about chlorate in Ohio

Is chlorate in Ohio tap water dangerous?

Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 46 cities in Ohio 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 Ohio 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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