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National Drinking Water Database

National Drinking Water Database - Chemical Contaminants


Status: Unregulated - EPA has not established a maximum legal limit in tapwater for this contaminant.

Chlorate is a disinfection byproduct (unregulated chlorine dioxide byproduct), an herbicide and a pollutant from explosives.

Found above
health guidelines
Found above
legal limit
Water utilities
People Served

Chlorate Exposure by State

Water utilities in 6 states have reported detecting Chlorate in treated tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies.

StateWater Suppliers with Chlorate contamination
New York154,269

The Most Polluted Communities

44 water utilities reported detecting Chlorate in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies

Ranked by highest average Chlorate level

RankSystem Population Served Positive test results of total reported tests Average Level
1Henrico County Public Utilities
Richmond, VA
289,00048 of 49419.68 ppb
(0 to 1062 ppb)
2Gcwsa - Jarratt
Emporia, VA
7,19021 of 21402.76 ppb
(134.33 to 754.33 ppb)
3Randall-Bold Water Treatment Plant
Oakley, Ca, CA
30,0009 of 9380.11 ppb
(55 to 690 ppb)
4Diablo Water District
Oakley, CA
33,2509 of 9380.11 ppb
(55 to 690 ppb)
Fairmont, MN
10,77855 of 56313.32 ppb
(0 to 801.67 ppb)
6San Diego County Water Authority
San Diego, CA
03 of 3292.67 ppb
(220 to 350 ppb)
7Santa FE I.D.
Rancho Santa Fe, CA
20,82817 of 17238 ppb
(21 to 389 ppb)
8Los Angeles Department of Water and Power
Los Angeles, CA
3,828,7008 of 8235.5 ppb
(85 to 331 ppb)
9Cal AM Water Company - Monterey
Pacific Grove, CA
92,11539 of 39183.97 ppb
(15 to 330 ppb)
10Zone 7 Water Agency
Livermore, CA
195,23091 of 98173.66 ppb
(0 to 534 ppb)

Testing Summary for Chlorate

Are tests routinely required for Chlorate by federal law?No
Water suppliers reporting tests for Chlorate (2004-2009):58 of 47,576
Average testing rate for water supplier reporting tests (2004-2009):2.3 per year

Government, industry, academic studies and classifications

government/industry list/academic study appears on list as classification(s)


government/industry list/academic study reference

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