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Notice to Readers: Limitations Inherent to a Cross-Sectional Assessment of Blood Lead Levels Among Persons Living in Homes with High Levels of Lead in Drinking Water

During 2000--2003, the District of Columbia (DC) experienced very high concentrations of lead in drinking water. In February 2004, the DC Department of Health requested assistance from CDC to assess health effects of elevated lead levels in residential tap water. CDC reviewed available blood lead surveillance data for the period 1998--2003 and reported the findings of a longitudinal analysis and a cross-sectional assessment in MMWR on April 2, 2004 (1).

The cross-sectional assessment was designed for a limited purpose, to take a snapshot of blood lead levels in the homes with the highest levels of lead in water and to provide service to children at risk for lead poisoning. The assessment had several design limitations. The data were not collected in a manner that would allow a comparison between the amount of lead consumed in drinking water and blood lead levels. Additionally, the blood lead levels did not necessarily represent what peak blood levels might have been before the problems with the DC water supply were recognized. Thus, these results should not be used to make conclusions about the contribution of water lead to blood lead levels in DC, to predict what might occur in other situations where lead levels in drinking water are high, or to determine safe levels of lead in drinking water. The dataset for the cross-sectional assessment is not available to CDC for further analysis.

CDC has conducted a more thorough analysis of trends in DC blood lead levels for the period 1998--2006, which confirms the conclusions in the original analysis. In addition, CDC has examined the association between DC blood lead levels and the partial replacement of leaded drinking water service lines. Preliminary data show that strategies of replacing only the publicly owned portion of lead pipes (known as partial mitigation) do not decrease (and might increase) blood lead levels. CDC notified the U.S. Environmental Protection Agency, DC, and other jurisdictions when these preliminary findings became known, and is following up with more definitive guidance. These findings have been submitted to a scientific journal for publication. The information related to the preliminary findings concerning partial lead pipe replacement is available at


  1. CDC. Blood lead levels in residents of homes with elevated lead in tap water---District of Columbia, 2004. MMWR 2004;53:268--70.

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