Menu

EWG's Tap Water Database — 2019 UPDATE

Donate

Chlorate

Prescott Valley WD Upper

Chlorate forms in drinking water as a byproduct of disinfection. Chlorate impairs thyroid function, making chlorate exposure most harmful during pregnancy and childhood. Read More.

In 2002, California scientists proposed an advisory value, called an action level, for chlorate at 200 parts per billion. Between 2013 and 2015, the EPA collected data through the Unregulated Contaminant Monitoring Rule program and found that over 15 percent of water tests from 38 percent of utilities had chlorate levels above a health-protective concentration, which federal scientists defined as 210 parts per billion, nearly equivalent to the California advisory value.

Click here to read more about disinfection byproducts.

 

44

Samples

0

Samples exceeding legal limit (MCL)

0

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012N/A00N/A
2013N/A00N/A
2014ND220ND
2015ND220ND
2016N/A00N/A
2017N/A00N/A

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 210 ppb

The EWG Health Guideline of 210 ppb for chlorate was defined by the Environmental Protection Agency as a benchmark for testing under the Unregulated Contaminant Monitoring Rule program. This health guideline protects against hormone disruption.

ppb = parts per billion

All test results

Date Lab ID Result
2014-12-08201412110322AMND
2014-12-08201412100580AMND
2014-12-08201412110324AMND
2014-12-08201412100471AMND
2014-12-08201412110257AMND
2014-12-08201412110334AMND
2014-12-08201412100410AMND
2014-12-08201412100594AMND
2014-12-08201412100582AMND
2014-12-08201412110346AMND
2014-12-09201412100638AMND
2014-12-09201412100640AMND
2014-12-09201412100527AMND
2014-12-09201412100422AMND
2014-12-09201412100424AMND
2014-12-09201412100554AMND
2014-12-09201412100430AMND
2014-12-09201412100396AMND
2014-12-09201412100646AMND
2014-12-09201412100420AMND
2014-12-09201412100849AMND
2014-12-10201412100788AMND
2015-06-09201506100460AMND
2015-06-09201506100542AMND
2015-06-09201506100245AMND
2015-06-09201506100454AMND
2015-06-09201506100487AMND
2015-06-09201506100383AMND
2015-06-09201506100468AMND
2015-06-09201506100241AMND
2015-06-09201506100489AMND
2015-06-09201506100535AMND
2015-06-09201506100452AMND
2015-06-09201506100540AMND
2015-06-09201506100447AMND
2015-06-09201506100554AMND
2015-06-09201506100464AMND
2015-06-09201506100537AMND
2015-06-09201506100400AMND
2015-06-09201506100559AMND
2015-06-09201506100569AMND
2015-06-09201506100411AMND
2015-06-09201506100544AMND
2015-06-09201506100370AMND