Environmental News Service
Published July 23, 2007
WASHINGTON, DC, July 24, 2007 (ENS) - Toxic by-products of the chemicals used to purify Potomac River water have been found in District of Columbia tap water at levels above annual federal health limits by a nonprofit research organization with offices in the nation's capital.
The Environmental Working Group collected tap water samples from 18 locations across the city, including the U.S. Capitol, headquarters of the U.S. Environmental Protection Agency, parks, schools, and residences of pregnant women and other groups susceptible to health problems from exposures to disinfection byproducts.
Tests were commissioned from an accredited lab for two classes of disinfection byproducts - total trihalomethanes, or THMs, and haloacetic acids, or HAAs.
More than 40 percent of the tap water samples contained these chemical byproducts above annual federal health limits.
The HAAs were found at their highest levels since 2001, the last year before the District of Columbia's public water system, the Washington Aqueduct, modified its treatment techniques to reduce levels of THMs.
"These results illustrate the tremendous difficulties that water utilities face when trying to provide tap water that is free of potentially deadly bacteria and pathogens, yet not contaminated with toxic by-products of the chemicals used to kill these same microbes," the Environmental Working Group said, releasing the results of its tests.
"These toxic byproducts will continue to persist until the Potomac River is adequately cleaned up," said EWG Executive Director Richard Wiles.
"Until that happens residents of Washington and Northern Virginia should use carbon filters that can reduce these contaminants dramatically at one tenth the cost of bottled water," he said.
The EPA classifies HAAs as possible human carcinogens, and peer-reviewed studies have identified adverse reproductive and developmental effects, and the ability to damage DNA.
Wiles says the by-products of chlorination present a significant health issue that is not well addressed by current drinking water health standards.
EPA scientists have identified a total of 600 disinfection byproducts in tap water but EPA has set legal limits in tap water for only 11 of them.
These legal limits, such as those for HAAs and THMs, are established as a balance between health, treatment cost and feasibility.
Wiles warned, "These results represent the tip of the iceberg for chemical contamination of DC tap water."
The Washington Aqueduct produces drinking water for one million people in the District of Columbia, Arlington County, Virginia, and the City of Falls Church, Virginia.
A division of the Baltimore District, U.S. Army Corps of Engineers, the Aqueduct is a federally owned and operated public water supply agency that produces an average of 180 million gallons of water per day at two treatment plants located in the District of Columbia.
For more on how the Washington Aqueduct treats drinking water, click here.
