Menu

EWG's Tap Water Database — 2019 UPDATE

Donate

Chlorate

St. Louis City

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.

 

21

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
2013ND200ND
2014ND10ND
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
2013-02-06AB90466ND
2013-02-06AB90468ND
2013-02-06AB90470ND
2013-02-06AB90472ND
2013-04-033590884010AMND
2013-04-033590884009AMND
2013-04-033590884008AMND
2013-04-043590884019AAMND
2013-04-23AB96371ND
2013-04-23AB96369ND
2013-04-23AB96367ND
2013-04-23AB96365ND
2013-07-16AC05140ND
2013-07-16AC05134ND
2013-07-16AC05138ND
2013-07-16AC05136ND
2013-10-14AC13655ND
2013-10-14AC13657ND
2013-10-14AC13659ND
2013-10-14AC13661ND
2014-02-03AC18020ND