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Even small excess of lead harms growing brains
How much lead is dangerous to a child's brain? According to new research by Bruce Lanphear
and colleagues, even blood lead levels just over 5 micrograms per deciliter-half the level
considered allowable by the federal government-can cause reduced IQ, a serious risk factor for
criminality.
Lanphear et al. regularly tested the blood lead levels of 276 children followed from infancy to
age 5, and tested the children's IQs at 60 months of age. Their study controlled for other factors
that might influence IQ scores, such as parental IQ.
The researchers report that IQ levels in their subjects declined as blood lead rose, even in
children with blood lead concentrations lower than 10 micrograms per deciliter-the level the
government currently considers safe. "This indicates that millions more children in the United
States than previously thought endure the detrimental effects of lead exposure," Lanphear says.
In fact, the researchers say, the drop in IQs as lead level rises is steeper in children with lower
lead levels. "Among all children studied, there was on average a 5.5 point reduction in IQ for
every 10 micrograms per deciliter increase in blood lead," Lanphear says. "But for children who
had blood lead less than 10 micrograms per deciliter, there was an 11.1 point reduction in IQ for
the initial 10 microgram per deciliter increase in blood lead."
The new research supports earlier findings by the same research group
(see related article, Crime Times, 2000, Vol. 6, No. 3, Page 2)
which revealed that children's math and reading scores begin to decline at lead levels as low as
2.5 micrograms per deciliter. Based on their findings, the researchers call for reducing the level of
blood lead considered acceptable to 5 micrograms per deciliter, and for increased efforts to
identify and eliminate environmental lead sources.
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"Blood lead levels below 'acceptable' value linked with IQ deficits, according to new study,"
press release, Pediatric Academic Societies,
http://www.oea.umaryland.edu/pediatric/0430_lanphear.htm. Lanphear et al.'s findings presented
at the annual meeting of the Pediatric Academic Societies, Cincinnati, April 30, 2001.
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