Washington, D.C. Blood Lead Level Tests
Lead Poisoning Prevention Program Managers
The Centers for Disease Control and Prevention, Healthy Homes and Lead Poisoning Prevention Branch has recently acquired and analyzed blood lead test results that were not available to us in 2004 during the public health response to elevated drinking water lead levels in Washington DC and the report of blood lead levels in Washington published in Morbidity Mortality Weekly Review in April 2004. 1
A substantial number of blood lead test results from blood specimens collected in 2003 were unavailable for the analysis published in the 2004 MMWR. In 2009, CDC acquired all known 2003 blood lead test results for DC residents and completed a reanalysis to determine if the addition of the previously missing tests altered the results reported in the 2004 MMWR. The reanalysis included the 9,765 tests used in the original analysis plus 1,753 tests reported in surveillance data after the MMWR was published and 12,168 tests that had not been included in the surveillance files. The reanalysis showed that addition of the missing test data led to a decrease in the proportion of tests with blood lead levels ≥ 5 µg/dL or ≥ 10 µg/dL in 2003, regardless of the type of service line supplying water to the home (Table 1). These results do not change CDC’s original conclusions that … the percentage of test results >10 µg/dL and the percentage of test results >5 µg/dL at addresses with lead service pipes were higher than at addresses without lead service pipes.
Table 1: The Percent of Elevated Blood Lead Tests in 2003 by Type of Water Service Line and Data Set.
|Service Line Type||2004 MMWR Dataset*||Dataset Reported in 2009**||2004 MMWR Dataset*||Dataset Reported in 2009**|
|% ≥ 10 µg/dL||% ≥ 10 µg/dL||% ≥ 5 µg/dL||% ≥ 5 µg/dL|
|Lead Service Line||7.6||6.0 1.||31.2||26.5 3.|
|No Lead Service Line||2.8||2.0 2.||15.6||13.4 4.|
* n=9,683; ** n=10,637. The water service line type was unknown for 2, 670 tests. 1. p=0.09; 2. p< 0.001; 3. p=0.007; 4. p< 0.001
The first sentence of the Editorial Note in the 2004 MMWR referred to a cross-sectional study of homes with very high lead levels in drinking water and stated that … no children were identified with blood lead >10µg/dL, even in homes with the highest water lead levels. This sentence was misleading because it referred only to data from the cross-sectional study, and did not reflect findings of concern from the separate longitudinal study that showed that children living in homes serviced by a lead water pipe were more than twice as likely as other DC children to have had a blood lead level ≥10 µg/dL. CDC reiterates here a key message from the 2004 article … because no threshold for adverse health effects in young children has been demonstrated (no safe blood level has been identified), all sources of lead exposure for children should be controlled or eliminated. Lead concentrations in drinking water should be below the U. S. Environmental Protection Agency’s action level of 15 parts per billion.
The complete report of the reanalysis can be found at http://www.cdc.gov/nceh/lead/leadinwater/.
I would also like to bring to your attention two other strategies to reduce children’s exposure to lead in water. First, on our website www.cdc.gov/nceh/lead/waterlines.htm you can find a letter dated January 12, 2010 that discusses recent research related to blood lead levels and partial replacement of lead water service lines. This research indicates that partial lead service line replacement is associated with increased risk for blood lead levels ≥ 5 µg/dL or ≥ 10 µg/dL. CDC has also recommended that state and or local lead programs work closely with the agency responsible for oversight of water authority compliance with the lead and copper rule to ensure that water samples are taken when inspections are done for children with elevated blood lead levels in areas where the water lead levels exceed the EPA water lead action level of 15 ppb.
Mary Jean Brown ScD, RN
Chief, Healthy Homes and Lead Poisoning Prevention Branch
Centers for Disease Control and Prevention
4770 Buford highway NE
Atlanta, GA 30341
1 Stokes L, Onwuche NC, Thomas P, et al., Blood Lead Levels in Residents of Homes with Elevated Lead in Tap Water – District of Columbia, 2004; MMWR Weekly, April 2, 2004, 53(12); 268-270.