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EWG's Tap Water Database — 2019 UPDATE

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Chlorate

Town of Gilbert

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.

 

68

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
201333.9 ppb6244ND - 100.0 ppb
201446.0 ppb42ND - 96.0 ppb
201510.00 ppb21ND - 20.0 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
2013-04-22201304220123AM24.0 ppb
2013-04-22201304220129AM24.0 ppb
2013-04-22201304220127AM26.0 ppb
2013-04-22201304220125AM23.0 ppb
2013-04-22201304220108AMND
2013-04-22201304220110AM85.0 ppb
2013-04-22201304220119AM25.0 ppb
2013-04-22201304220121AM23.0 ppb
2013-04-23201304230228AM86.0 ppb
2013-04-23201304230213AM26.0 ppb
2013-04-23201304230225AM44.0 ppb
2013-04-23201304230223AM81.0 ppb
2013-04-23201304230221AM72.0 ppb
2013-04-23201304230217AM53.0 ppb
2013-04-23201304230219AMND
2013-04-23201304230215AMND
2013-04-23201304230211AMND
2013-04-24201304240155AM25.0 ppb
2013-04-24201304240159AM79.0 ppb
2013-04-24201304240169AMND
2013-04-24201304240167AMND
2013-04-24201304240157AM28.0 ppb
2013-04-24201304240163AMND
2013-04-24201304240161AMND
2013-04-24201304240165AM72.0 ppb
2013-04-25201304250474AMND
2013-04-25201304250476AM51.0 ppb
2013-04-25201304250480AM71.0 ppb
2013-04-25201304250478AMND
2013-07-25201307250333AM50.0 ppb
2013-07-25201307250327AMND
2013-07-25201307250329AMND
2013-07-25201307250331AM96.0 ppb
2013-10-14201310140290AM31.0 ppb
2013-10-14201310140278AM99.0 ppb
2013-10-14201310140288AM45.0 ppb
2013-10-14201310140294AM100.0 ppb
2013-10-14201310140292AMND
2013-10-14201310140286AM25.0 ppb
2013-10-14201310140284AM21.0 ppb
2013-10-14201310140282AM37.0 ppb
2013-10-14201310140280AM22.0 ppb
2013-10-14201310140276AMND
2013-10-15201310150554AM49.0 ppb
2013-10-15201310150552AM31.0 ppb
2013-10-15201310150556AM84.0 ppb
2013-10-15201310150548AM26.0 ppb
2013-10-15201310150550AM37.0 ppb
2013-10-15201310150546AM36.0 ppb
2013-10-16201310160457AM68.0 ppb
2013-10-16201310160455AM44.0 ppb
2013-10-16201310160451AM33.0 ppb
2013-10-16201310160453AM68.0 ppb
2013-10-22201310220324AM41.0 ppb
2013-10-22201310220322AM36.0 ppb
2013-10-22201310220320AM26.0 ppb
2013-10-22201310220328AM42.0 ppb
2013-10-22201310220326AMND
2013-10-23201310230754AM39.0 ppb
2013-10-23201310230758AMND
2013-10-23201310230760AMND
2013-10-23201310230756AMND
2014-01-09201401090389AMND
2014-01-09201401090391AMND
2014-01-21201401210282AM96.0 ppb
2014-01-21201401210278AM88.0 ppb
2015-06-15201506150309AMND
2015-12-13201512140112AM20.0 ppb