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EWG's Tap Water Database — 2019 UPDATE

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Chlorate

City of Mesa

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.

 

128

Samples

0

Samples exceeding legal limit (MCL)

22

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
2012N/A00N/A
201394.0 ppb12081ND - 440.0 ppb
201498.8 ppb65ND - 170.0 ppb
2015130.0 ppb22120.0 ppb - 140.0 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
2013-01-15201301160556AMND
2013-01-15201301160548AMND
2013-01-15201301160554AMND
2013-01-16201301160558AM23.0 ppb
2013-01-16201301160560AM340.0 ppb
2013-01-16201301160562AMND
2013-01-16201301160566AMND
2013-01-16201301160564AMND
2013-01-22201301240174AMND
2013-01-22201301240176AM330.0 ppb
2013-01-22201301240172AM240.0 ppb
2013-01-22201301240152AMND
2013-01-23201301240197AM300.0 ppb
2013-01-23201301240195AM120.0 ppb
2013-01-30201301310433AMND
2013-01-30201301310431AM410.0 ppb
2013-02-12201302140551AM21.0 ppb
2013-02-12201302140549AM150.0 ppb
2013-02-12201302140542AMND
2013-02-12201302140544AMND
2013-02-12201302140546AM62.0 ppb
2013-02-13201302140538AM210.0 ppb
2013-02-13201302140540AM40.0 ppb
2013-02-13201302140535AM50.0 ppb
2013-02-13201302140531AM28.0 ppb
2013-02-13201302140529AM38.0 ppb
2013-02-13201302140533AM56.0 ppb
2013-02-19201302200371AM130.0 ppb
2013-02-19201302200375AM140.0 ppb
2013-02-19201302200373AM74.0 ppb
2013-04-08201304100491AM250.0 ppb
2013-04-09201304100493AM50.0 ppb
2013-04-09201304100477AMND
2013-04-09201304100479AMND
2013-04-09201304100481AM22.0 ppb
2013-04-10201304110554AMND
2013-04-10201304110552AM160.0 ppb
2013-04-10201304110546AM24.0 ppb
2013-04-10201304110542AM36.0 ppb
2013-04-10201304110540AM35.0 ppb
2013-04-10201304110544AMND
2013-04-16201304170691AM57.0 ppb
2013-04-17201304170697AM110.0 ppb
2013-04-17201304170701AM30.0 ppb
2013-04-17201304170699AM320.0 ppb
2013-04-17201304170695AM270.0 ppb
2013-05-09201305100048AM250.0 ppb
2013-05-09201305100040AMND
2013-05-09201305100038AMND
2013-05-09201305100042AM21.0 ppb
2013-05-09201305100044AM81.0 ppb
2013-05-09201305100046AM56.0 ppb
2013-05-14201305150463AM160.0 ppb
2013-05-14201305150465AM77.0 ppb
2013-05-15201305150520AM68.0 ppb
2013-05-15201305150518AMND
2013-05-20201305200188AM100.0 ppb
2013-05-20201305200190AM230.0 ppb
2013-05-20201305200068AMND
2013-05-20201305200127AMND
2013-07-09201307100757AM330.0 ppb
2013-07-09201307100755AMND
2013-07-10201307100759AM190.0 ppb
2013-07-10201307100761AM390.0 ppb
2013-07-16201307170500AM160.0 ppb
2013-07-16201307170508AMND
2013-07-16201307170504AM26.0 ppb
2013-07-16201307170506AMND
2013-07-16201307170510AM25.0 ppb
2013-07-17201307170514AM110.0 ppb
2013-07-17201307170512AM94.0 ppb
2013-07-17201307170520AMND
2013-07-17201307170518AMND
2013-07-17201307170516AM21.0 ppb
2013-07-23201307240533AM360.0 ppb
2013-07-23201307240531AM240.0 ppb
2013-07-24201307240537AMND
2013-07-24201307240544AMND
2013-08-06201308070603AM94.0 ppb
2013-08-06201308070601AMND
2013-08-06201308070586AMND
2013-08-06201308070588AMND
2013-08-06201308070584AMND
2013-08-07201308070605AM41.0 ppb
2013-08-07201308070590AM53.0 ppb
2013-08-13201308140062AM260.0 ppb
2013-08-13201308140060AM160.0 ppb
2013-08-14201308140418AM170.0 ppb
2013-08-14201308140416AM61.0 ppb
2013-08-14201308140394AM20.0 ppb
2013-08-14201308140392AMND
2013-10-08201310080650AM220.0 ppb
2013-10-08201310080652AM260.0 ppb
2013-10-08201310080610AMND
2013-10-08201310080612AMND
2013-10-08201310080614AM35.0 ppb
2013-10-08201310080616AMND
2013-10-09201310090515AM110.0 ppb
2013-10-09201310090517AM150.0 ppb
2013-10-09201310090511AMND
2013-10-09201310090513AM39.0 ppb
2013-10-15201310150509AM55.0 ppb
2013-10-15201310150507AM73.0 ppb
2013-10-15201310150505AM340.0 ppb
2013-10-15201310150503AM300.0 ppb
2013-10-16201310160477AM45.0 ppb
2013-10-16201310160475AM110.0 ppb
2013-11-05201311070309AM320.0 ppb
2013-11-05201311070311AM440.0 ppb
2013-11-05201311050403AMND
2013-11-05201311050401AM25.0 ppb
2013-11-06201311070313AM280.0 ppb
2013-11-06201311070294AM70.0 ppb
2013-11-06201311070298AMND
2013-11-06201311070300AM33.0 ppb
2013-11-06201311070296AM33.0 ppb
2013-11-12201311130338AM73.0 ppb
2013-11-12201311130336AM160.0 ppb
2013-11-13201311140713AMND
2013-11-20201311210516AM140.0 ppb
2014-03-25201403250421AM120.0 ppb
2014-03-25201403250419AM170.0 ppb
2014-06-04201406040578AM160.0 ppb
2014-06-04201406040576AM95.0 ppb
2014-09-02201409020219AM48.0 ppb
2014-09-02201409020217AMND
2015-01-21201501220206AM140.0 ppb
2015-01-21201501220204AM120.0 ppb