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No IQ gain found in lead
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
"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
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
Susan FitzGerald's e-mail address is firstname.lastname@example.org.