Chlorate Contamination

Chlorate in Virginia Drinking Water

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

Cities Tested

Over HA

76%

% Over HA

555.9 µg/L

State Avg

▲ 17% vs national

vs National

198

Health Violations

Analysis

Chlorate in Virginia: what the data shows

Virginia has 55 cities with chlorate data from the EPA's UCMR 3 program (2013–2015). Chlorate exceeded the 210 µg/L EPA lifetime health advisory in 42 of those cities. The state average max detected level is 555.9 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)

Virginia

76%

42 of 55 cities

→ ▲ 17% above national rate (worse)

National avg

59%

1866 of 3166 cities

City Map

Chlorate data across Virginia

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 Virginia

Highest Chlorate levels (µg/L)

All Cities

All Virginia cities ranked by chlorate level

#	City	Level	Over HA?	Violations	Grade
1	Vansant	2040.0 µg/L	Over HA	24	C
2	Chesterfield	1800.0 µg/L	Over HA	5	B+
3	Williamsburg	1700.0 µg/L	Over HA	36	D
4	Richmond City	1400.0 µg/L	Over HA	2	A
5	Chesapeake City	1030.0 µg/L	Over HA	48	F
6	Henrico	1000.0 µg/L	Over HA	3	A
7	Front Royal	933.7 µg/L	Over HA	16	F
8	Petersburg City	920.0 µg/L	Over HA	3	A-
9	Roanoke City	917.0 µg/L	Over HA	3	B+
10	Stafford	897.2 µg/L	Over HA	3	B-
11	Hopewell	890.0 µg/L	Over HA	24	F
12	Suffolk City	800.0 µg/L	Over HA	35	A
13	Hanover	777.0 µg/L	Over HA	6	A
14	Amelia	704.1 µg/L	Over HA	1	A+
15	Leesburg	680.0 µg/L	Over HA	2	A-
16	Martinsville City	680.0 µg/L	Over HA	9	A-
17	Lynchburg City	620.0 µg/L	Over HA	0	A+
18	Emporia	600.5 µg/L	Over HA	3	A+
19	Portsmouth City	600.0 µg/L	Over HA	18	A
20	Colonial Heights City	590.0 µg/L	Over HA	3	A+
21	Williamsburg City	590.0 µg/L	Over HA	0	A
22	Bristol City	560.0 µg/L	Over HA	0	A
23	Newport News City	550.0 µg/L	Over HA	8	A-
24	Woodbridge	548.5 µg/L	Over HA	1	B+
25	Virginia Beach City	540.0 µg/L	Over HA	29	A
26	Fredericksburg	540.0 µg/L	Over HA	21	C
27	Winchester City	540.0 µg/L	Over HA	1	A
28	Manassas Park City	540.0 µg/L	Over HA	6	A
29	Harrisonburg City	519.0 µg/L	Over HA	0	A
30	Vienna	490.0 µg/L	Over HA	1	B+
31	Norfolk City	480.0 µg/L	Over HA	7	B+
32	Arlington	440.0 µg/L	Over HA	3	B
33	Charlottesville City	410.0 µg/L	Over HA	0	A
34	Mcincr, Mcb Quantico	410.0 µg/L	Over HA	26	C
35	Waynesboro City	409.0 µg/L	Over HA	5	A
36	Manassas City	401.8 µg/L	Over HA	5	A
37	Herndon	400.0 µg/L	Over HA	14	B
38	Rockville	360.0 µg/L	Over HA	384	F
39	Fort Belvoir	350.0 µg/L	Over HA	7	B+
40	Alexandria City	320.0 µg/L	Over HA	0	A
41	Smithfield	230.0 µg/L	Over HA	111	F
42	Culpeper	229.0 µg/L	Over HA	18	B-
43	Ashburn	200.0 µg/L	No	2	A-
44	Winchester	190.0 µg/L	No	9	A-
45	Charlottesville	160.0 µg/L	No	33	F
46	Fredericksburg City	130.0 µg/L	No	1	A+
47	Staunton City	104.2 µg/L	No	2	A
48	Collinsville	63.0 µg/L	No	3	A+
49	Dilwyn	60.0 µg/L	No	2	A-
50	Clintwood	55.0 µg/L	No	30	D
51	Lynchburg	52.2 µg/L	No	14	C
52	Hopewell City	42.0 µg/L	No	9	A-
53	Abingdon	28.5 µg/L	No	7	B+
54	Chatham	28.0 µg/L	No	46	F
55	Blacksburg	22.3 µg/L	No	1	A-

FAQ

Frequently asked questions about chlorate in Virginia

Is chlorate in Virginia tap water dangerous?

Chlorate has no federal MCL. The EPA lifetime health advisory is 210 µg/L. 42 cities in Virginia 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 Virginia 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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