The MMWR series is one of three scientific publications published by CDC and is regarded as CDC’s flagship publication. The publication’s primary audience is made up of professionals, including medical professionals, such as clinicians, and state and local public health officials, and the publication also reaches CDC’s federal partners, such as EPA and the Centers for Medicare & Medicaid Services (CMS). In addition to the weekly reports, the MMWR series also includes MMWR Recommendations and Reports, which contain in-depth articles that relay policy statements for prevention and treatment on all areas in CDC’s scope of responsibility, such as recommendations from CDC advisory committees. CDC can also issue articles that it calls Dispatches to allow for immediate publication of urgent public health information. The Dispatches are generally subsequently published in the MMWR. The April 2, 2004, MMWR weekly report included an article on the BLLs of District residents that was first published as a Dispatch on March 30, 2004. Lead is a dangerous contaminant commonly found in the environment that can affect almost every organ and system in the body. The main target for lead toxicity is the nervous system. In addition to causing behavior problems and learning disabilities in young children, elevated BLLs can cause such effects as damage to the brain and kidneys. In pregnant women, elevated BLLs may cause miscarriage. Drinking contaminated tap water is one way humans may be exposed to lead. While measures taken during the past two decades have greatly reduced exposures to lead in tap water, lead still can be found in some metal water fixtures, interior water pipes, or pipes connecting a house to the main water pipe in the street. Lead in tap water usually comes from the corrosion of older fixtures; lead service lines, including lead service pipes; or the solder that connects pipes. Federal law requires that blood lead screening tests be made available to all children enrolled in Medicaid. CMS’s State Medicaid Manual requires that these screenings be performed at ages 12 and 24 months and that all children aged 36 to 72 months who have not previously been screened also receive a blood lead test. The American Academy of Pediatrics agrees with these requirements for screening and has also stated that efforts must continue to test children who are at high risk for lead exposure. Beginning in 1995, elevated BLLs—the first noninfectious condition—were designated as a nationally notifiable condition reportable to CDC. The District (along with 36 states and the city of New York) has reported elevated BLLs of 10 micrograms per deciliter (μg/dL) of blood or higher for children to CDC. The District has reported this BLL information to CDC since 1997. The District’s Childhood Lead Poisoning Screening and Reporting Act of 2002 requires that each health care provider or facility in the District perform a blood test for lead poisoning as part of a well-child care visit for each child that they serve who is under the age of six and resides in the District. The test must occur between ages 6 months and 14 months, and a second test must occur between ages 22 months and 26 months. Both tests must be performed unless parental consent is withheld or an identical test has already been performed within the previous 12 months. If a child’s age exceeds 26 months and a blood lead screening has not been performed, the child must be screened twice before age 6. The District also requires health care providers or facilities to report the results of blood tests for lead poisoning on every child under age 6 who resides in the District to the child’s parents. As the nation’s public health agency, CDC has set levels of concern—the BLL that should prompt public health actions—for lead exposure since the 1960s. In 1991, CDC set the level of concern at 10 μg/dL of blood for children aged 6 months to 15 years and 25 μg/dL for adults. However, CDC has also recognized that a BLL of 10 μg/dL does not define a threshold for the harmful effects of lead—in other words, no safe blood lead level has been identified for children. The Lead Contamination Control Act of 1988 authorized CDC to initiate programs to eliminate childhood lead poisoning in the United States. As a result of this act, the CDC Childhood Lead Poisoning Prevention Program (CLPPP) was created. One of the program’s primary responsibilities is to educate the public and health care providers about childhood lead poisoning. CDC’s CLPPP also provides funding to state and local health departments to determine the extent of childhood lead poisoning by screening children for elevated BLLs. Since the inception of CDC’s lead program, nearly 60 state and local jurisdictions have received funding for their state and local CLPPPs. CDC’s efforts contribute to the Healthy People 2020 initiative, which includes an objective to eliminate elevated BLLs in children. As of 2007 to 2008, the latest years for which data were available, approximately 1.2 percent of children aged 1 to 5 years nationwide had BLLs exceeding 10 µg/dL. In addition, the Advisory Committee on Childhood Lead Poisoning Prevention advises and guides CDC regarding new scientific knowledge and technical developments and their practical implications for childhood lead poisoning prevention efforts. In November 2010, the advisory committee initiated a work group to recommend new approaches, terminology, and strategies for defining elevated BLLs among children. Under the Safe Drinking Water Act, EPA is responsible for regulating contaminants that may pose a public health risk and that are likely to be present in public water supplies, including lead. EPA’s Lead and Copper Rule established a 15 parts per billion (ppb) lead action level as a regulatory standard for water utilities in an effort to prevent and mitigate the adverse health consequences resulting from elevated lead levels in drinking water. Water systems must sample tap water at locations that are at high risk of lead contamination, generally because they are served by lead service lines or are likely to contain lead solder in the household plumbing. If more than 10 percent of the samples at residences contain lead levels over 15 ppb, the water systems must take action to lower these levels, such as replacing lead service lines in the distribution system or treating water to reduce its corrosion of the service lines, and notify EPA and residents. The District’s Water and Sewer Authority owns and operates a system that delivers water—produced by the U.S. Army Corps of Engineers Washington Aqueduct—to customers in the District. In 2000, the Washington Aqueduct began to use chloramine instead of chlorine in its disinfection process. This change likely contributed to elevated water lead levels. By late 2001, the Water and Sewer Authority became aware that the levels of lead in the District’s tap water were above EPA’s limit of 15 ppb, and it notified EPA of that fact in August 2002. Beginning in 2002, the Water and Sewer Authority notified its customers of the elevated water lead levels by issuing notices, distributing educational brochures, and holding public meetings. In the fall of 2003, the Water and Sewer Authority requested assistance from DCDOH in responding to District residents’ inquiries about the health effects of the elevated water lead levels. District residents, including infants and children, would have been exposed to elevated levels of lead in tap water during this period if they used unfiltered water for drinking, cooking, or preparing infant formula or juice. Staff from NCEH, along with individuals from DCDOH and the U.S. Public Health Service, contributed to CDC’s investigation on the effect of lead in the District’s tap water on the BLLs of residents, which was presented in the April 2, 2004, MMWR article. The 2004 MMWR article reported the results of two analyses from CDC’s investigation, which was conducted in February and March 2004. (See app. I for a copy of the 2004 MMWR article.) The first analysis was conducted to identify trends in BLLs in District residents before and after the changes in the water disinfection process. The second analysis was conducted to determine whether residents in homes with the highest water lead levels (300 ppb or greater) had BLLs at or above CDC’s level of concern of 10 μg/dL. The summary statement of the 2004 MMWR article’s findings noted that the elevated water lead levels might have contributed to a small increase in BLLs among District residents. The article’s Editorial Note section opened with a sentence that incorrectly stated the results of the first analysis. The sentence read, “The findings in this report indicate that although lead in tap water contributed to a small increase in BLLs in D.C., no children were identified with BLLs ≥ 10 μg/dL, even in homes with the highest water lead levels.” The statement that “no children were identified with BLLs ≥ 10 μg/dL” was incorrect, relative to the first analysis. Since the 2004 MMWR article was published, CDC officials have said that in its first analysis some children were identified with BLLs ≥ 10 μg/dL, which is CDC’s level of concern for children. The last part of the statement indicating that none of the children in homes with the highest water lead levels had BLLs > 10 μg/dL was correct, in that none of the 30 children in the second analysis had BLLs that reached CDC’s level of concern, according to CDC officials. While the 2004 MMWR article discussed some limitations to its findings, it did not discuss other limitations that addressed how information in the 2004 MMWR article could be used. For example, it did not state that the article should not be used to make conclusions about the contribution of lead in tap water to BLLs in the District. The statement in the 2004 MMWR article that incorrectly links the results of the two analyses in the same editorial note and the incomplete description of the limitations to the article’s findings have resulted in this information being interpreted in the press and by others in ways other than as CDC intended.