Science News - November 17, 2004

Perchlorate contamination mystery in Massachusetts

High concentrations of perchlorate have been found in drinking-water source wells in Massachusetts and in discharged water from a wastewater treatment plant in the northeastern corner of the state. What makes these events troubling is that the discoveries cannot be linked to traditional anthropogenic sources, such as rocket-fuel production facilities or military bases, and the levels appear to be too high to be explained by natural sources.

Until now, perchlorate contamination of water in the United States has been typically associated with California and southwestern states. Anthropogenic sources are considered the main cause of most U.S. contamination. However, natural sources of perchlorate appear to be responsible for low levels of contamination over a 60,000-square-mile area of west Texas (Environ. Sci. Technol. 2003, 37, 376A–377A; 377A–378A).

The finding in Massachusetts of perchlorate at levels of hundreds of parts per billion (ppb) in wastewater plant discharges, the first such report in the country, has led to speculation that the source could be sodium hypochlorite bleach used as a disinfectant. Analyses made in October did find high perchlorate levels of 4300–5000 ppb in the bleach used at a water treatment plant upstream of a Massachusetts town with perchlorate in its drinking water, according to Lewis Zediana, the town’s water treatment plant engineer. However, the bleach is added at such low concentrations that it can’t be the perchlorate source, he says.

Zediana believes that dumping upstream of the waste treatment plant is the source. But the state’s Department of Environmental Protection is still evaluating the possibility that water treatment procedures are part of the problem, according to spokesperson Edward Colletta.

The perchlorate discoveries were serendipitous. In January 2004, Massachusetts issued emergency guidelines requiring communities to monitor for perchlorate between February 2004 and February 2005 after the discovery of groundwater contamination at a military base on Cape Cod. Since then, 700 water treatment systems have been conducting tests and 7 have found contamination, according to Colletta. Because many of these systems are not located near military suppliers or bases, the perchlorate source is unknown—blasting powder and fireworks are among the possible sources being investigated, he says.

In May, Massachusetts set an interim public health recommendation of 1 ppb perchlorate in drinking water for pregnant women, infants, and people with hypothyroidism. —REBECCA RENNER