Perchlorate
Wellesley Water Division (MWRA)
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.
Samples
Samples exceeding legal limit (MCL)
Samples exceeding
health guidelines
Testing results - average by year
| Year | Average result | Samples taken | Detections | Range of results |
|---|---|---|---|---|
| 2014 | 0.0980 ppb | 3 | 3 | 0.0520 ppb - 0.166 ppb |
| 2015 | 0.0957 ppb | 3 | 3 | 0.0650 ppb - 0.144 ppb |
| 2016 | 0.111 ppb | 3 | 3 | 0.0560 ppb - 0.186 ppb |
| 2017 | 0.159 ppb | 3 | 3 | 0.0620 ppb - 0.282 ppb |
| 2018 | 0.142 ppb | 3 | 3 | 0.0840 ppb - 0.243 ppb |
| 2019 | 0.0937 ppb | 3 | 2 | ND - 0.215 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 |
|---|---|
| 2014-08-12 | 0.166 ppb |
| 2014-08-12 | 0.0520 ppb |
| 2014-08-12 | 0.0760 ppb |
| 2015-09-23 | 0.0780 ppb |
| 2015-09-23 | 0.144 ppb |
| 2015-09-23 | 0.0650 ppb |
| 2016-09-21 | 0.0900 ppb |
| 2016-09-21 | 0.186 ppb |
| 2016-09-21 | 0.0560 ppb |
| 2017-08-08 | 0.282 ppb |
| 2017-08-08 | 0.0620 ppb |
| 2017-08-08 | 0.132 ppb |
| 2018-09-04 | 0.0980 ppb |
| 2018-09-04 | 0.243 ppb |
| 2018-09-04 | 0.0840 ppb |
| 2019-09-17 | 0.0660 ppb |
| 2019-09-17 | 0.215 ppb |
| 2019-09-17 | ND |