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EWG's Tap Water Database — 2019 UPDATE

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Perchlorate

Washington Aqueduct Division

Perchlorate, a component of rocket fuel, occurs both naturally and as a synthetic chemical. Ingested perchlorate interferes with thyroid function. Exposure to perchlorate during pregnancy and childhood can impair cognitive development. Read More.

According to the EPA, perchlorate likely contaminates the water of more than 16 million Americans. Perchlorate interferes with iodine uptake in the thyroid, which can result in reduced thyroid hormones and an impact on metabolism, physical development and cognitive development. Children and developing fetuses are the most at risk from perchlorate contamination.

Perchlorate is the only unregulated contaminant for which the EPA has attempted to set a federal drinking water standard since 1996. However, the agency has yet to propose a draft limit for this contaminant. Perchlorate in drinking water is regulated in Arizona, California, Massachusetts, New Jersey, New York and Texas. California set a public health goal of 1 part per billion for perchlorate in 2015.

Click here to read more about perchlorate.

 

143

Samples

0

Samples exceeding legal limit (MCL)

4

Samples exceeding
health guidelines

Testing results - average by year

 
YearAverage resultSamples takenDetectionsRange of results
20120.500 ppb24240.400 ppb - 0.600 ppb
20130.438 ppb24240.300 ppb - 0.700 ppb
20140.579 ppb24240.300 ppb - 0.900 ppb
20150.596 ppb24240.300 ppb - 1.90 ppb
20160.433 ppb2422ND - 1.40 ppb
20170.361 ppb23230.200 ppb - 0.600 ppb

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 1 ppb

The EWG Health Guideline of 1 ppb for perchlorate was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against hormone disruption.

ppb = parts per billion

All test results

Date Lab ID Result
2012-01-01Dalecarlia0.400 ppb
2012-01-01McMillan0.400 ppb
2012-02-01Dalecarlia0.500 ppb
2012-02-01McMillan0.400 ppb
2012-03-01Dalecarlia0.400 ppb
2012-03-01McMillan0.400 ppb
2012-04-01Dalecarlia0.500 ppb
2012-04-01McMillan0.600 ppb
2012-05-01Dalecarlia0.500 ppb
2012-05-01McMillan0.400 ppb
2012-06-01Dalecarlia0.600 ppb
2012-06-01McMillan0.500 ppb
2012-07-01Dalecarlia0.600 ppb
2012-07-01McMillan0.600 ppb
2012-08-01Dalecarlia0.500 ppb
2012-08-01McMillan0.500 ppb
2012-09-01Dalecarlia0.600 ppb
2012-09-01McMillan0.600 ppb
2012-10-01Dalecarlia0.500 ppb
2012-10-01McMillan0.500 ppb
2012-11-01Dalecarlia0.500 ppb
2012-11-01McMillan0.500 ppb
2012-12-01Dalecarlia0.500 ppb
2012-12-01McMillan0.500 ppb
2013-01-01Dalecarlia0.400 ppb
2013-01-01McMillan0.400 ppb
2013-02-01Dalecarlia0.400 ppb
2013-02-01McMillan0.500 ppb
2013-03-01Dalecarlia0.300 ppb
2013-03-01McMillan0.400 ppb
2013-04-01Dalecarlia0.500 ppb
2013-04-01McMillan0.500 ppb
2013-05-01Dalecarlia0.600 ppb
2013-05-01McMillan0.400 ppb
2013-06-01Dalecarlia0.400 ppb
2013-06-01McMillan0.300 ppb
2013-07-01Dalecarlia0.500 ppb
2013-07-01McMillan0.400 ppb
2013-08-01Dalecarlia0.500 ppb
2013-08-01McMillan0.400 ppb
2013-09-01Dalecarlia0.700 ppb
2013-09-01McMillan0.600 ppb
2013-10-01Dalecarlia0.400 ppb
2013-10-01McMillan0.300 ppb
2013-11-01Dalecarlia0.400 ppb
2013-11-01McMillan0.400 ppb
2013-12-01Dalecarlia0.400 ppb
2013-12-01McMillan0.400 ppb
2014-01-01Dalecarlia0.800 ppb
2014-01-01McMillan0.600 ppb
2014-02-01Dalecarlia0.400 ppb
2014-02-01McMillan0.500 ppb
2014-03-01Dalecarlia0.400 ppb
2014-03-01McMillan0.400 ppb
2014-04-01Dalecarlia0.400 ppb
2014-04-01McMillan0.400 ppb
2014-05-01Dalecarlia0.300 ppb
2014-05-01McMillan0.300 ppb
2014-06-01Dalecarlia0.500 ppb
2014-06-01McMillan0.400 ppb
2014-07-01Dalecarlia0.600 ppb
2014-07-01McMillan0.500 ppb
2014-08-01Dalecarlia0.900 ppb
2014-08-01McMillan0.700 ppb
2014-09-01Dalecarlia0.700 ppb
2014-09-01McMillan0.900 ppb
2014-10-01Dalecarlia0.800 ppb
2014-10-01McMillan0.700 ppb
2014-11-01Dalecarlia0.700 ppb
2014-11-01McMillan0.700 ppb
2014-12-01Dalecarlia0.600 ppb
2014-12-01McMillan0.700 ppb
2015-01-01Dalecarlia0.500 ppb
2015-01-01McMillan0.500 ppb
2015-02-01Dalecarlia0.800 ppb
2015-02-01McMillan0.800 ppb
2015-03-01Dalecarlia0.300 ppb
2015-03-01McMillan0.400 ppb
2015-04-01Dalecarlia0.400 ppb
2015-04-01McMillan0.400 ppb
2015-05-01Dalecarlia0.300 ppb
2015-05-01McMillan0.400 ppb
2015-06-01Dalecarlia0.300 ppb
2015-06-01McMillan0.400 ppb
2015-07-01Dalecarlia0.400 ppb
2015-07-01McMillan0.500 ppb
2015-08-01Dalecarlia0.700 ppb
2015-08-01McMillan0.700 ppb
2015-09-01Dalecarlia1.80 ppb
2015-09-01McMillan1.90 ppb
2015-10-01Dalecarlia0.500 ppb
2015-10-01McMillan0.500 ppb
2015-11-01Dalecarlia0.500 ppb
2015-11-01McMillan0.500 ppb
2015-12-01Dalecarlia0.400 ppb
2015-12-01McMillan0.400 ppb
2016-01-01Dalecarlia0.400 ppb
2016-01-01McMillan0.400 ppb
2016-02-01Dalecarlia0.300 ppb
2016-02-01McMillan0.400 ppb
2016-03-01Dalecarlia0.400 ppb
2016-03-01McMillan0.300 ppb
2016-04-01Dalecarlia0.300 ppb
2016-04-01McMillan0.500 ppb
2016-05-01Dalecarlia0.300 ppb
2016-05-01McMillan0.600 ppb
2016-06-01DalecarliaND
2016-06-01McMillanND
2016-07-01Dalecarlia0.400 ppb
2016-07-01McMillan0.400 ppb
2016-08-01Dalecarlia0.300 ppb
2016-08-01McMillan0.300 ppb
2016-09-01Dalecarlia0.600 ppb
2016-09-01McMillan1.10 ppb
2016-10-01Dalecarlia1.40 ppb
2016-10-01McMillan0.800 ppb
2016-11-01Dalecarlia0.300 ppb
2016-11-01McMillan0.300 ppb
2016-12-01Dalecarlia0.300 ppb
2016-12-01McMillan0.300 ppb
2017-01-01Dalecarlia0.300 ppb
2017-01-01McMillan0.300 ppb
2017-02-01Dalecarlia0.300 ppb
2017-02-01McMillan0.400 ppb
2017-03-01Dalecarlia0.300 ppb
2017-03-01McMillan0.300 ppb
2017-04-01Dalecarlia0.300 ppb
2017-04-01McMillan0.300 ppb
2017-05-01Dalecarlia0.200 ppb
2017-05-01McMillan0.300 ppb
2017-06-01Dalecarlia0.300 ppb
2017-06-01McMillan0.300 ppb
2017-07-01Dalecarlia0.500 ppb
2017-07-01McMillan0.400 ppb
2017-08-01Dalecarlia0.300 ppb
2017-08-01McMillan0.300 ppb
2017-09-01Dalecarlia0.500 ppb
2017-09-01McMillan0.500 ppb
2017-10-01Dalecarlia0.400 ppb
2017-10-01McMillan0.400 ppb
2017-11-01Dalecarlia0.600 ppb
2017-11-01McMillan0.500 ppb
2017-12-01Dalecarlia0.300 ppb