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EWG's Tap Water Database

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Chlorate

Cole County PWSD 1

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.

 

14

Samples

0

Samples exceeding legal limit (MCL)

0

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2010N/A00N/A
2011N/A00N/A
2012N/A00N/A
2013ND70ND
2014ND70ND
2015N/A00N/A

ppb = parts per billion.

State and national drinking water standards and health guidelines

Health Guideline 210 ppb

The 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
2013-06-04AB97376ND
2013-06-04AB97388ND
2013-06-04AB97386ND
2013-06-04AB97384ND
2013-06-04AB97382ND
2013-06-04AB97380ND
2013-06-04AB97378ND
2014-02-25AC14979ND
2014-02-25AC14977ND
2014-02-25AC14975ND
2014-02-25AC14973ND
2014-02-25AC14971ND
2014-02-25AC14969ND
2014-02-25AC14981ND