EWG's Tap Water Database — 2021 UPDATE



Devens Massdevelopment

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.





Samples exceeding legal limit (MCL)


Samples exceeding
health guidelines

Testing results - average by year

YearAverage resultSamples takenDetectionsRange of results
20140.0933 ppb32ND - 0.210 ppb
20150.0967 ppb32ND - 0.210 ppb
20160.107 ppb32ND - 0.240 ppb
20170.120 ppb330.0500 ppb - 0.210 ppb
20180.0750 ppb220.0700 ppb - 0.0800 ppb
20190.0767 ppb330.0600 ppb - 0.1000 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 Result
2014-07-150.0700 ppb
2014-07-220.210 ppb
2015-08-180.210 ppb
2015-08-180.0800 ppb
2016-07-140.0800 ppb
2016-07-140.240 ppb
2017-08-090.210 ppb
2017-08-090.1000 ppb
2017-08-090.0500 ppb
2018-08-080.0800 ppb
2018-08-080.0700 ppb
2019-08-060.1000 ppb
2019-08-060.0600 ppb
2019-11-120.0700 ppb