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'Acceptable' Lead Levels Linked to Lower IQ Scores in Kids

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WebMD Health News

April 30, 2001 -- Many efforts have been made to remove lead from the environment, but lead poisoning continues to be a problem in children. A disturbing new study presented today at the Pediatric Academic Societies' Annual Meeting suggests even "safe" levels of lead in the blood are dangerous enough to severely damage IQ scores in developing children.

Long recognized as a serious public health threat, lead can damage the brain and nervous system, and even a low level of lead exposure can cause learning disabilities, hearing loss, speech, language, and behavior problems, and other serious health effects in children. Lead has also been associated with dental caries.

Lead in paint and gasoline is banned in the U.S., but it persists in the environment in ubiquitous house dust and paint chips, particularly in poorer neighborhoods. Lead-based paints were commonly used in the 1950s and '60s. One group, the Alliance to End Childhood Lead Poisoning, estimates that 30 million U.S. homes built before 1960 still have lead in them.

Although universal lead screening is not available, it is recommended that children at high risk for lead exposure be screened. Blood lead concentrations of 10 micrograms per deciliter of blood or less are considered to be safe and acceptable levels.

But are these levels really safe?

Researchers looked at a cross-section of 276 children in Rochester, N.Y., over a five-year period. They measured the blood lead levels of the children seven times between birth and age 5 and conducted standard IQ tests to see if the children were performing at the appropriate level of development.

But what primary researcher Bruce Lanphear, MD, MPH, found was that even children with the "safe" level of lead in their blood, as defined by the Environmental Protection Agency and the CDC, had significant brain damage.

Specifically, at age 5, the children experienced a 5.5-point drop in IQ for every jump of 10 micrograms of lead per deciliter in their blood. What's worse, says Lanphear, is that the biggest drop in IQ occurred with 73% of the children who had the very lowest lead levels. The deficit was as high as 11 IQ points from normal.

"If there really is a 10-point drop in IQ with the initial 10 microgram per deciliter [of lead in the blood], that's huge," says Lanphear of Children's Hospital Medical Center in Cincinnati. And once the IQ points are lost, Lanphear says they never come back.

Daniel Coury, MD, professor of clinical pediatrics at Ohio State University, believes that Lanphear's findings will encourage public health officials to rethink the lead issue. "Technically, Dr. Lanphear's data say, no lead is good lead," Coury says.

Lanphear believes that poor neighborhoods endure a disproportionate share of lead toxicity.

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