About Lead in Drinking Water

For more than 20 years, CDC has championed children’s health by working together with other federal agencies and through effective programs and policies to prevent childhood lead poisoning. Exposure to lead can cause behavior problems and learning disabilities in young children and can also affect the health of adults. Lead can be found in many sources. Lead-based paint and the dust produced as it deteriorates, found mostly in older homes built before 1978, are major contributors of lead exposure in U.S. children. Lead can also be found in some water pipes inside the home or pipes that connect homes to the main water supply pipe. Lead found in tap water usually comes from the decay of old lead-based pipes, fixtures or from leaded solder that connects drinking water pipes.

Most of CDC’s work related to lead in water has occurred in the District of Columbia (DC), where approximately 23,000 homes have lead-based water service pipes. As part of its lead-in-water testing program, DC Water and Sewer Authority (WASA) expanded testing to include homes with lead service pipes extending from the water main to the house. By late January 2004, results of the expanded water testing indicated that most of the homes tested had water lead levels that were above the U.S. Environmental Protection Agency’s (EPA) action level of 15 parts per billion (ppb). The action level indicates that utilities must take certain steps to correct the problem and notify citizens of the situation. On February 16, DC Department of Health (DCDOH) requested CDC’s help in reviewing health effects of elevated lead levels in residential tap water.

An analysis of available blood lead surveillance data was published in an April 2004 edition of Morbidity Mortality Weekly Review (MMWR). CDC reported that the percentage of test results >10 µg/dL, CDC’s blood lead level of concern, as well as the percentage of test results >5 µg/dL were higher at addresses with lead service pipes than at addresses without lead service pipes.

However, a large number of test results from blood samples collected from DC-area children in 2003 were unavailable and not included in the analysis published in the 2004 MMWR. In 2009, CDC acquired all known 2003 test results and completed a reanalysis of blood lead levels that involved over 23,000 blood lead tests to determine if the addition of the missing test results changed the previously reported results. This included 9,765 tests that were used in the original analysis, and 1,753 tests reported in surveillance data after the MMWR was published. An additional 12,168 tests that had not been included in the surveillance files were also part of the reanalysis. The addition of the missing test data led to an overall decrease in the percent of children with elevated blood lead levels ≥ 5 µg/dL and ≥ 10 µg/dL in 2003, regardless of the type of service line supplying water to the home. These results support CDC’s original conclusions that the percentage of test results >10 µg/dL, as well as the percentage of test results >5 µg/dL were higher at addresses with lead service pipes than at addresses without lead service pipes. CDC reiterates a key message from the 2004 MMWR: No safe blood level has been identified and 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.