PHILADELPHIA– The most recent water monitoring data for the District of Columbiaâ tap water shows that lead levels continue to exceed regulated Environmental Protection Agency levels, and that residents should continue to follow the consumer advisory for flushing and filtering tap water before use. However, some reductions of lead levels were noted in the latter half of the monitoring period, which could be attributed to the treatment with orthophosphates that began in August 2004.

The data  130 household drinking water samples collected between July and December 2004 by the District of Columbia Water and Sewer Authority  show a trend towards lower lead levels later in the year. Before the flushing and filtering advisory can be lifted, 90 percent of samples must have lead levels of 15 parts per billion or lower. Most recent results reported by WASA show that 90 percent of samples have lead levels at 59 parts per billion or lower.

Details on the monitoring results are available online at www.epa.gov/dclead along with other developments, including a supplement to EPA administrative order regarding lead service line replacement, the status on flushing distribution lines and updates on the latest lead-treatment research.

Experts have indicated it would take about six months or longer for the orthophosphate to begin coating the inside of water service lines with a protective film that would prevent lead from leaching into the water.

The most recent data indicates that orthophosphate treatment is progressing as expected, but additional rounds of monitoring are needed for conclusive evidence of its effectiveness,” said Jon Capacasa, director of the water protection division for EPA mid-Atlantic region. œIt is essential that consumers continue to flush and filter their water before use in accordance with earlier guidance.

Although lead levels remain above the regulated EPA levels, concentrations of lead have declined from the first half to the second half of the monitoring period. This latest data reinforces preliminary results from laboratory pipe loop studies that showed how lead levels should drop significantly after an extended period of orthophosphate treatment.

The Washington Aqueduct, water producer for the Washington, D.C. area, began adding orthophosphate to part of the water system in June and throughout the entire district in August. Orthophosphate is a tasteless, odorless, food-grade additive used by many water systems nationwide to control corrosion in metal pipes. It works by building up a thin protective coating inside pipes and plumbing fixtures to prevent metals such as lead, copper, and iron from leaching into the water.

The water that district residents drink comes from the Potomac River and is treated at the Washington Aqueduct. The water contains almost no lead until it reaches individual service lines, some of which are made of lead. But water, which is a corrosive solvent, dissolves lead from lead service lines, some types of water meters and from household plumbing fixtures that contain lead.

Residents are reminded that EPA lead-related flushing guidance is still in effect because lead levels remain elevated above the action level for replacing lead service lines. Residents who know or suspect they have lead service lines should run the water in their home for 10 minutes to flush the pipes before drinking or using tap water for cooking. Showering or washing clothes counts as flushing. Residents using water filters provided by WASA should follow all flushing instructions before filtering tap water. Residents should also be sure to run each faucet for at least an additional 60 seconds before use. Only cold water should be used for drinking or cooking. Boiling water will not remove lead.

WASA, the Washington Aqueduct, EPA and other members of the Technical Expert Working Group will continue to evaluate the latest monitoring results and research, and update the public regularly. Go to EPA website at www.epa.gov/dclead or call the Safe Drinking Water Hotline (800) 426-4791 for more information.