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EWG's Tap Water Database — 2019 UPDATE

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Chlorate

Hilo

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.

 

16

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
2013ND80ND
2014ND80ND
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
2013-09-23201309250113AMND
2013-09-23201309250033AMND
2013-09-23201309250035AMND
2013-09-23201309250118AMND
2013-09-23201309250031AMND
2013-09-23201309250130AMND
2013-09-23201309250121AMND
2013-09-23201309250037AMND
2014-03-24201403260442AMND
2014-03-24201403260446AMND
2014-03-24201403260462AMND
2014-03-24201403260453AMND
2014-03-24201403260451AMND
2014-03-24201403260471AMND
2014-03-24201403260469AMND
2014-03-24201403260456AMND