Menu

EWG's Tap Water Database — 2019 UPDATE

Donate

Chlorate

City of Hewitt

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.

 

22

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
2013ND90ND
2014ND130ND
2015N/A00N/A
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
2013-10-09Q1308728015ND
2013-10-09Q1308728001ND
2013-10-09Q1308728009ND
2013-10-09Q1308728017ND
2013-10-09Q1308728007ND
2013-10-09Q1308728011ND
2013-10-09Q1308728003ND
2013-10-09Q1308728005ND
2013-10-09Q1308728013ND
2014-01-14Q1400599001ND
2014-01-14Q1400599003ND
2014-04-17Q1412218009ND
2014-04-17Q1412218005ND
2014-04-17Q1412218007ND
2014-04-17Q1412218011ND
2014-04-17Q1412218017ND
2014-04-17Q1412218013ND
2014-04-17Q1412218015ND
2014-04-17Q1412218001ND
2014-04-17Q1412218003ND
2014-07-29Q1431973001ND
2014-07-29Q1431973003ND