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EWG's Tap Water Database — 2019 UPDATE

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Chlorate

Johnson Utilities

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.

 

39

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
2014N/A00N/A
20152.00 ppb393ND - 34.0 ppb
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
2015-01-193173624ND
2015-01-193173505ND
2015-01-193173581ND
2015-01-213175872ND
2015-01-273178371ND
2015-01-273178382ND
2015-01-28318110134.0 ppb
2015-01-283179079ND
2015-01-283181239ND
2015-02-093185891ND
2015-02-093185893ND
2015-02-233194483ND
2015-02-233194475ND
2015-02-233194479ND
2015-02-243195533ND
2015-02-243195525ND
2015-02-243195567ND
2015-02-243195559ND
2015-03-173209597ND
2015-07-143280730ND
2015-07-14327952921.0 ppb
2015-07-143280677ND
2015-07-143280713ND
2015-07-143279541ND
2015-07-143280690ND
2015-07-153281632ND
2015-07-15328159223.0 ppb
2015-07-153281584ND
2015-07-153281567ND
2015-07-153281615ND
2015-07-153281597ND
2015-07-213285560ND
2015-07-213285529ND
2015-07-213285493ND
2015-07-213285582ND
2015-07-213285472ND
2015-07-213285485ND
2015-07-213285510ND
2015-07-213285550ND