Perchlorate Update

Update on Perchlorate testing by the Cambridge Water Department (CWD) based on the recent notice by the US Environmental Protection Agency (USEPA) that they will not issue a national regulation at this time – please see EPA link below:

Even with the USEPA not issuing a national regulation on Perchlorate the Massachusetts Department of Environmental Protection (MassDEP) is still regulating and the CWD is still testing for it.

To date all Perchlorate results for Cambridge tap water were less than the Minimum Reporting Limit (MRL) of 1.0 ppb.


In 2004 the MassDEP required public water suppliers to collect a single sample and mandated that public water suppliers had to begin monitoring yearly for Perchlorate beginning in calendar year 2007.  The Maximum Contaminant Level (MCL) for Perchlorate is 0.002 milligrams per liter (mg/L) (2.0 Parts per billion (ppb)).  In 2007 only, Water systems must collect a sample at the entry point to the distribution system for four consecutive quarters. The long-term monitoring frequency for perchlorate may be reduced to once a year after the initial monitoring period if all sample results indicate perchlorate concentrations less than the MRL of 0.0010 mg/L (1.0 ppb).

The initial MassDEP Perchlorate Regulations for Public Drinking Water became effective on July 28, 2006.

A water system can apply for a monitoring waiver after the 2008 – 2010 monitoring period.  Cambridge Department prefers to not apply for waivers and will continue to monitor.

The reason Perchlorate is important is that it interferes with the normal function of the thyroid gland and thus has the potential to affect growth and development and could cause brain damage and other adverse health effects, particularly in fetuses and infants.  Sources of perchlorate contamination comes from blasting operations and fireworks displays.

Where Can I Find Additional Information about Perchlorate on the Internet?

Visit EPA’s perchlorate page at: