Salon investigates  the U.S. Centers for Disease Control and Prevention's recent work on urban water quality:
A 2004 CDC report  found that water contamination "might have contributed a small increase in blood lead levels." The study has been influential. School officials in New York and Seattle  have used the CDC report as justification for not aggressively responding to high levels of lead in their water, and other cities have cited the report to dispel concerns about lead in tap water.
But the results of thousands of blood tests that measured lead contamination in children were missing from the report, potentially skewing the findings and undermining public health. Further, the CDC discovered in 2007 that many young children living in D.C. homes with lead pipes were poisoned by drinking water and suffered ill effects. Parents wondered whether the water could have caused speech and balance problems, difficulty with learning, and hyperactivity. Yet the health agency did not publicize the new findings or alert public health authorities in D.C. or other federal agencies that regulate lead, such as the U.S. Environmental Protection Agency or Housing and Urban Development.
"This is a disaster of accountability from CDC's point of view," says John Rosen, a pediatrician and national expert on lead poisoning at Montefiore Medical Center in New York City.