Know Your Environment. Protect Your Health.

Chlorate

City of Olympia

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.

 

20

Samples

0

Samples exceeding legal limit (MCL)

0

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2013ND200ND
2014N/A00N/A
2015N/A00N/A
2016N/A00N/A
2017N/A00N/A
2018N/A00N/A
2019N/A00N/A
2020N/A00N/A
2021N/A00N/A
2022N/A00N/A
2023N/A00N/A

ppb = parts per billion

State, National, and Health Guidelines for Drinking Water

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
2013-02-14WA97-SE1-13-02624-6123ND
2013-02-14WA97-SE1-13-02624-6124ND
2013-05-20WA97-SE1-13-08686-20034ND
2013-05-20WA97-SE1-13-08686-20030ND
2013-05-20WA97-SE1-13-08686-20031ND
2013-05-20WA97-SE2-13-08686-20029ND
2013-05-20WA97-SE1-13-08686-20033ND
2013-05-20WA97-SE2-13-08686-20036ND
2013-05-20WA97-SE1-13-08686-20035ND
2013-05-20WA97-SE1-13-08686-20032ND
2013-08-05WA97-SE3-13-14093-32130ND
2013-08-05WA97-SE3-13-14093-32129ND
2013-11-13WA97-SE4-13-21665-49262ND
2013-11-13WA97-SE2-13-21665-49261ND
2013-11-13WA97-SE2-13-21665-49259ND
2013-11-13WA97-SE2-13-21665-49258ND
2013-11-13WA97-SE4-13-21665-49255ND
2013-11-13WA97-SE2-13-21665-49257ND
2013-11-13WA97-SE2-13-21665-49256ND
2013-11-13WA97-SE2-13-21665-49260ND