By Carol D. Leonnig
Washington Post Staff Writer
Thursday, July 19, 2007; A01

Toxic chlorine pollutants were found at unsafe levels in 40 percent of D.C. tap water samples tested this spring during the water utility's annual chlorine surge, according to a national environmental group's report to be released today.

The nonprofit Environmental Working Group conducted tests at 18 sites -- including private homes, an elementary school, the U.S. Capitol and the Environmental Protection Agency -- to measure the levels of chlorine toxins that could cause cancer, reproductive problems and developmental delays in children. In 90 percent of the samples, the tests found another class of chlorine toxin at levels that some epidemiological studies have associated with low birth weight and serious birth defects.

The findings suggest that the chemicals needed to help make Potomac River water potable could be creating a different risk to consumers. Chlorine is used to kill disease-causing microbes. Heavy use results in chemical compounds, called disinfection byproducts, that are formed when organic matter in the river water reacts with the chlorine.

The District's water utility has reported a general decrease in chlorine toxins since it switched from treating its water with chlorine to less-potent chloramine in 2000. But environmental groups and scientists said the new findings highlight a potential problem nationwide for many water utilities that, as in Washington, have switched at the EPA's urging to the chloramines and periodically flush their systems with high doses of chlorine to kill pathogens deep in their pipes.

The tests were conducted from May 1 to 4, at the end of a month-long "chlorine burn" the Washington Aqueduct annually conducts to remove sludge and sediment from pipes. The burn temporarily raises the levels of the toxins.

The Washington-based working group specializes in researching environmental issues, notably chemical contaminants in water and pesticides in food.

Its report comes amid concerns raised about the quality of the water supply for more than 1.1 million customers in the District, Arlington and Falls Church after dangerously high levels of lead contamination were found in tap water. Neighborhood and environmental activists have complained that the Washington Aqueduct, which treats the water, and the D.C. Water and Sewer Authority, which delivers the water to customers, do not do enough to address general water concerns or the high lead levels found last year in D.C. public schools' water.

Washington Aqueduct General Manager Thomas P. Jacobus said the latest study results are what he would have expected and were probably temporary. He stressed that D.C. water meets EPA safety standards because test results for the concentration of chlorination compounds are averaged over the year.

WASA General Manager Jerry N. Johnson did not respond to calls for comment. His spokesman, Michele Quander-Collins, said WASA's testing shows acceptable levels of disinfection toxins in the water supply in every monthly test this year.

"The byproduct levels we test for at eight EPA-approved locations have been well within EPA parameters," she said. "Our tests don't show high levels."

Rick Rogers, a water official in EPA's regional office in Philadelphia, which is responsible for overseeing the District's water quality, said the test results submitted by WASA do not suggest any problem with chlorine toxins. He said EPA regulations focus on limiting risks from long-term exposure, not short-term spikes.

"A couple of months of higher numbers -- we don't have any information that shows conclusively that that causes health risks," he said.

But the working group said the high levels found during the chlorine flushing reflect badly on what it calls the aqueduct's antiquated treatment system and the EPA's lack of knowledge about the ramifications of using a brew of chemicals to make dirty river water potable.

"It's time to face up to the fact that it's impossible to take the Potomac River in its current polluted state, put it through a very old, rudimentary treatment system and get water that people can safely drink," said the group's executive director, Richard Wiles.

His organization recommends that the U.S. Army Corps of Engineers, which operates the aqueduct, switch to carbon filtration to remove more chlorine byproducts and that residents use Brita-like filters until then.

Wiles said the District's water problem is a "classic case" of a national water-treatment problem.

Although the EPA has urged utilities to disinfect with chloramines instead of chlorine, many utilities find the chloramines are not strong enough to kill microbes throughout their vast distribution systems. They flush every year or two with chlorine to kill pathogens such as cryptosporidium, which can kill people with vulnerable immune systems. Some studies suggest chloramines are creating more toxic kinds of chlorine byproducts, few of which have been thoroughly studied.

"We switched from one treatment to the next" before knowing whether it was safe, Wiles said.

To carry out the tests, the working group submitted samples to an independent lab, Environmental Engineering and Technology. It tested for two disinfection byproducts: total trihalomethanes and haloacetic acids. Nineteen sites were tested, but one sample was lost.

The tests found that trihalomethanes were not markedly increased and did not exceed safety limits. But haloacetic acids were at the highest levels in the city since 2001, when the aqueduct started chloramine treatment.

The highest concentrations were found at a bathroom tap at the Martin Luther King Jr. Memorial Library, at an elementary school in Northwest Washington and at the home of a pregnant woman. Unsafe levels were also found at water fountains and bathroom taps at two public parks, in Anacostia and Fort Dupont, and at the National Zoo.

Robert Etris, director of public utilities for Falls Church, and David Hundelt, chief of water, sewer and streets for Arlington County, said they were not worried about the high levels.

"Well, if it were in my water system I would be, but we are not finding that in our system," Etris said of the chlorine pollutants. "If these samples were taken during the chlorine flush, which was a very short amount of time, then the numbers might be on the high side."

Hundelt agreed that the spike in levels should not make consumers fear for their health. "The risk is not an acute risk," he said.

Staff writer Amy Orndorff contributed to this report.