Exposure to Lead in Children — How Low Is Low Enough?

Encephalopathy in childhood due to lead poisoning was described more than 100 years ago, and cognitive sequelae after recovery were reported in 1943. During the past three decades, epidemiologic studies have demonstrated inverse associations between blood lead concentrations and children's IQs at successively lower lead concentrations. In response, the Centers for Disease Control and Prevention (CDC) repeatedly lowered its definition of an elevated blood lead concentration, which now stands at 10 μg per deciliter (0.483 μmol per liter) (see Figure). Since the removal of lead from gasoline, the median blood lead concentration in U.S. children has fallen from 15 μg . . .