EWG's Tap Water Database — 2019 UPDATE



Attleboro Water Department

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
20120.165 ppb220.110 ppb - 0.220 ppb
20130.385 ppb220.320 ppb - 0.450 ppb
20140.262 ppb550.0600 ppb - 0.500 ppb
20150.313 ppb440.160 ppb - 0.470 ppb
20160.250 ppb330.180 ppb - 0.300 ppb
20170.163 ppb330.130 ppb - 0.210 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
2012-07-050.220 ppb
2012-07-050.110 ppb
2013-07-010.450 ppb
2013-07-010.320 ppb
2014-06-160.310 ppb
2014-06-160.310 ppb
2014-07-020.500 ppb
2014-07-020.0600 ppb
2014-09-180.130 ppb
2015-03-040.310 ppb
2015-03-040.310 ppb
2015-07-150.160 ppb
2015-08-210.470 ppb
2016-07-180.300 ppb
2016-07-180.180 ppb
2016-08-030.270 ppb
2017-07-190.130 ppb
2017-07-190.150 ppb
2017-11-130.210 ppb