School-age lead exposures most harmful to IQ
High concentrations in children’s blood also linked to brain-tissue losses and future criminality
By Janet Raloff
Testing for lead only in infants and toddlers may be a mistake, a new study suggests. Pediatricians routinely test very young children because this is the age when blood concentrations of the neurotoxic heavy metal tend to be highest. But older children can face significant lead exposures, and lead’s ability to lower IQ, the new study shows, is much greater for exposures in early school-age children than in toddlers.
The study, which will appear in an upcoming Environmental Health Perspectives, also finds that the later childhood exposures correlate more strongly than earlier ones with an exaggerated risk of incurring future criminal arrests for violent behavior.
The new data “get at a key concept in environmental health: that there may be some windows of vulnerability — stages of development — that are more vulnerable than others,” notes environmental epidemiologist Howard Hu of the University of Michigan in Ann Arbor. If school-age brains are more susceptible to lead toxicity than younger ones, “that’s important to know, from a public health perspective,” he says. Looking for lead in older children would be a first step in identifying families that need counseling on reducing sources of lead in and around the home.