Chlorate Contamination

Chlorate in South Carolina Drinking Water

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

Cities Tested

Over HA

63%

% Over HA

296.9 µg/L

State Avg

▲ 4% vs national

vs National

151

Health Violations

Analysis

Chlorate in South Carolina: what the data shows

South Carolina has 52 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 33 of those cities. The state average max detected level is 296.9 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)

South Carolina

63%

33 of 52 cities

→ ▲ 4% above national rate (worse)

National avg

59%

1866 of 3166 cities

City Map

Chlorate data across South Carolina

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 South Carolina

Highest Chlorate levels (µg/L)

All Cities

All South Carolina cities ranked by chlorate level

#	City	Level	Over HA?	Violations	Grade
1	Graniteville	730.0 µg/L	Over HA	3	A-
2	Woodruff	680.0 µg/L	Over HA	5	A-
3	Greenwood	640.0 µg/L	Over HA	14	C
4	Easley	620.0 µg/L	Over HA	2	B+
5	Lexington	590.0 µg/L	Over HA	55	F
6	Myrtle Beach	586.0 µg/L	Over HA	17	B-
7	North Myrtle Beach	580.0 µg/L	Over HA	4	B+
8	Clemson	560.0 µg/L	Over HA	4	B+
9	Belton	540.0 µg/L	Over HA	13	B
10	West Anderson	530.0 µg/L	Over HA	1	A
11	Lancaster	500.0 µg/L	Over HA	33	B+
12	Fort Jackson	480.0 µg/L	Over HA	8	A-
13	La France	470.0 µg/L	Over HA	0	A-
14	Spartanburg	450.0 µg/L	Over HA	2	A
15	Cassatt	410.0 µg/L	Over HA	4	A
16	Okatie	400.0 µg/L	Over HA	7	B+
17	Anderson	380.0 µg/L	Over HA	15	C+
18	Conway	370.0 µg/L	Over HA	14	C+
19	Columbia	340.0 µg/L	Over HA	80	F
20	Pawleys Island	340.0 µg/L	Over HA	13	B-
21	Westminster	340.0 µg/L	Over HA	8	C-
22	Fort Lawn	330.0 µg/L	Over HA	7	B+
23	Hilton Head Island	280.0 µg/L	Over HA	4	B-
24	West Columbia	280.0 µg/L	Over HA	87	F
25	North Charleston	280.0 µg/L	Over HA	0	B
26	Chesnee	280.0 µg/L	Over HA	0	A-
27	Florence	250.0 µg/L	Over HA	3	B+
28	Charleston	240.0 µg/L	Over HA	5	B+
29	Mount Pleasant	240.0 µg/L	Over HA	1	B+
30	Johns Island (Sta.)	240.0 µg/L	Over HA	1	A-
31	North Augusta	230.0 µg/L	Over HA	13	B+
32	Seneca	230.0 µg/L	Over HA	0	A
33	Orangeburg	220.0 µg/L	Over HA	3	A-
34	Carlisle	200.0 µg/L	No	15	B
35	Lamar	180.0 µg/L	No	3	A
36	Union	170.0 µg/L	No	14	B+
37	Summerville	140.0 µg/L	No	22	C+
38	Chesterfield	140.0 µg/L	No	10	A-
39	Lyman	120.0 µg/L	No	2	A+
40	York	120.0 µg/L	No	65	F
41	Laurens	110.0 µg/L	No	17	B-
42	Gaffney	100.0 µg/L	No	12	C+
43	Inman	100.0 µg/L	No	1	A
44	Tega Cay	100.0 µg/L	No	0	B+
45	Rock Hill	73.0 µg/L	No	45	F
46	Pickens	45.8 µg/L	No	7	B+
47	Six Mile	41.0 µg/L	No	1	A+
48	Greenville	40.0 µg/L	No	9	A
49	Greer	34.0 µg/L	No	3	A
50	Newberry	30.0 µg/L	No	28	C
51	Ridge Spring	29.1 µg/L	No	3	A
52	New Ellenton	28.0 µg/L	No	3	B+

FAQ

Frequently asked questions about chlorate in South Carolina

Is chlorate in South Carolina tap water dangerous?

Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 33 cities in South Carolina 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 South Carolina 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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