Lead in D.C. water: Still more to do

By Thomas R. Frieden
Sunday, June 27, 2010

Congressional interest in past lead contamination has raised important questions about the safety of the District's public water supply and the response of the Centers for Disease Control and Prevention. This past year, since becoming director of the CDC, I have carefully reviewed the agency's efforts related to the District's drinking water.

Everyone agrees that lead is dangerous and that there is no safe blood lead level for children. For nearly three decades, CDC has spearheaded an effective national lead-prevention campaign. When we began, 88 percent of American children had blood lead levels above 10 micrograms per deciliter. Today it is less than 1 percent. Although we have further to go, this has been one of our nation's greatest public health success stories.

This success makes what occurred in the District particularly painful. A decade ago, a change in disinfection procedures for the city's water supply had the unintended consequence of hastening corrosion of lead pipes, resulting in high lead levels in some homes. Although testing by the District's Water and Sewer Authority (WASA) in 2000 revealed increased lead levels, this information was not widely known, and levels remained high for the next four years. In January 2004, The Post reported that most D.C. homes with lead pipes had water lead levels above the Environmental Protection Agency regulatory threshold. Two weeks later, the District asked the CDC for help.

Our agency responded immediately. The first priority was to prevent continuing exposure of District residents, particularly children, to water contaminated with lead. The CDC worked closely with the D.C. Department of Health, WASA, the EPA, the U.S. Public Health Service, and other federal and local agencies to warn that pregnant and breastfeeding women and children should not drink unfiltered tap water. Having initiated steps to prevent exposures, the CDC worked to determine the health consequences of the contamination.

In such situations, the CDC partners with local authorities, relying on them to provide the necessary data, and this was the case in the District. The CDC used information provided by WASA to identify homes at risk of lead exposure and depended on the D.C. Department of Health to monitor and report blood lead tests of residents.

Our agency published initial data in the Morbidity and Mortality Weekly Report, repeating earlier advice that young children and pregnant and breastfeeding women refrain from drinking unfiltered tap water. The report showed that lead in tap water contributed to an increase in blood lead levels. But in one section it also stated that no children were identified with elevated blood lead levels, even in homes with the highest lead concentrations in water.

Over the years, this analysis and others have been questioned by a congressional subcommittee, some scientists and the media. After I became the CDC director, I also had questions about the initial CDC report. I contacted the District government to request data on all blood lead tests that had not been previously reported to CDC and ordered an internal review of the CDC lead program and its handling of this incident.

I concluded that, in its urgency to rapidly assess the situation, the CDC communicated scientific results poorly. The CDC's report left room for misinterpretation and may have led some people to improperly minimize concerns about lead exposure and conclude that lead in the water had never been a problem.

This year, having recovered missing data, CDC conducted an intensive reanalysis. This reanalysis, which included the missing data, did not alter the original conclusion that lead in water was associated with an increase in blood lead levels. But it did prompt the CDC to issue a new report clearly acknowledging that the statement in the 2004 report that no children were identified with elevated blood lead levels was wrong. In fact, both the original analysis and the new analysis show that children living in homes serviced by lead water pipes were more than twice as likely as other D.C. children to have elevated blood lead levels. We also learned that replacing lead pipes outside but not in homes does not appear to reduce the risk of lead exposure.

Lead in water remains an important health concern. The CDC has worked to improve the District's lead program and protect city residents. Elevated blood lead levels among D.C. children have fallen by half over the past five years and are now lower than the national average and similar to those in other large cities. D.C. Water (WASA's new name, as of this month) reports that the water supply is within EPA limits, but there are still homes with lead pipes and other sources of lead that require abatement, and residents who are concerned can have their water tested by D.C. Water.

Our focus must now be on how best to protect people from lead poisoning. I have met with D.C. Del. Eleanor Holmes Norton (D) and have pledged to work with her, Chairman Brad Miller (D-N.C.) of the House Science Oversight and Investigations Subcommittee, other members of Congress, and District officials to eliminate lead poisoning here and across the country. As Norton emphasized at a recent congressional hearing, a high priority is to increase the percentage of eligible children in the District who are being screened. Lead exposure can cause harm even at low levels, and we must be aggressive in our prevention efforts. A single lead-poisoned child is one too many.

The writer is director of the Centers for Disease Control and Prevention.

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