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No IQ gain found in lead removal

By Susan FitzGerald
INQUIRER STAFF WRITER

A drug treatment that removes lead from the body does not undo the damage already done on a child's intelligence, a new study has found.

Researchers had hoped children with moderately elevated levels who got this lead-lowering treatment would show improvements in IQ scores, but that did not happen.

An editorial accompanying the study in today's New England Journal of Medicine said the results suggested lead's effects on the brain were irreversible, even when the lead was removed from the body.

"The more children's exposure to lead can be prevented, the better," said Carla Campbell, medical director of the lead-poisoning program at Children's Hospital of Philadelphia.

The primary source of children's lead exposure is dust from flaking and deteriorating lead paint, which can get onto the hands and into the mouths of babies and children. Exposure to even low levels of lead can cause subtle but significant changes in a child's ability to learn. Lead can lower IQ, interfere with speech and hearing development, and cause attention and behavioral problems.

The process for removing lead is called chelation and is recommended for children with lead levels of 45 micrograms per deciliter of blood or higher.

Researchers at the National Institute of Environmental Health Sciences and four teaching hospitals set out to test whether an oral chelation drug called succimer would benefit children with lower blood lead levels - 20 to 44 micrograms.

Previous research has shown that there is reason for concern at those levels and lower.

A child can drop two to three IQ points when lead levels go from 10 micrograms to 20 micrograms.

This latest study involved 780 children, some in Philadelphia and Newark, who were between ages 1 and 3 and lived in deteriorating urban housing. They were given either succimer or dummy capsules for 26 days.

The drug did work to lower lead levels in the blood, but it had no effect on intelligence. Three years after treatment, the children who got the chelation drug generally fared no better than the children who took the placebo on tests to assess such things as intelligence and behavior.

The researchers said the results indicated there was little reason to recommend chelation therapy for children with lead levels under 45 micrograms.

But, "it's fairly clear that getting levels down when it's over 45 is important," said Donald Schwarz, an attending physician at Children's Hospital who was a study researcher.

Richard Tobin, with the Philadelphia Department of Public Health, said that although blood lead levels had dropped significantly among city children in recent years, exposure remained a problem in deteriorating housing.