Toxicity Of Lead In Children--Clinical Trial

Environmental Health Sciences

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Abstract

In a randomized clinical trial of succimer, an oral chelating agent that lowers blood lead concentration, children with blood leads of 20 ? 44 micrograms per deciliter were given succimer or placebo and followed with cognitive and behavioral testing. We reported previously that, despite lower blood lead levels during treatment, children given succimer were no different that children given placebo on their test results at age 5 years. This year, we extended follow-up to 7 years of age, but still see no salutary effect of chelation treatment. Prospective data from multiple studies in several countries show that lead exposure insufficient to produce symptoms still results in cognitive deficits in young children. Peak blood lead level, which is usually achieved around two years of age, is associated with lower scores on IQ tests administered at age 4 years and later. It was not known whether such effects can be reduced or prevented once exposure has taken place. To answer this question, we designed and supported the Treatment of Lead-exposed Children Trial (TLC), which was a 780 child, randomized trial in which children were given succimer, a drug that lowers blood lead level quickly, or placebo, and then followed for three to five years until they were 5 and 7 years old. In 2001, we reported that treating the children with succimer lowered their lead levels but did not produce better scores on tests designed to test cognitive, behavioral, and neuropsychological function at age 5 years. We have now followed the children to age 7, and administered a much more sophisticated battery of psychological test suited to the school age child, but still find no salutary effect of treatment. Children tested at age 7 years who had elevated blood lead concentrations at age 2 years have the same results whether their blood lead was lowered with the chelating drug succimer or they were given placebo.