LIFETIME EXPOSURE TO ENVIRONMENTAL LEAD AND CHILDRENS INTELLIGENCE AT11-13 YEARS - THE PORT PIRIE COHORT STUDY

Objective-To examine the association between environmental exposure to lead and children's intelligence at age 11-13 years, and to assess th e implications of exposure in the first seven years of life for later childhood development. Design-Prospective cohort study. Subjects-375 c hildren born in or around the lead smelting town of Port Pirie, Austra lia, between 1979 and 1982. Main outcome measure-Children's intelligen ce quotient (IQ) measured at 11-13 years of age. Results-IQ was invers ely associated with both antenatal and postnatal blood lead concentrat ions, Verbal, performance, and full scale IQ were inversely related to blood lead concentration with no apparent threshold, Multivariate ana lyses indicated that after adjustment for a wide range of confounders, the postnatal blood lead concentrations (particularly within the age range 15 months to 7 years) exhibited inverse associations with IQ, St rong associations with IQ were observed for lifetime average blood lea d concentrations at various ages. The expected mean full scale IQ decl ined by 3.0 points (95% confidence interval 0.07 to 5.93) for an incre ase in lifetime average blood lead concentration from 0.48 to 0.96 mu mol/l (10 to 20 mu g/dl). Conclusions-Exposure to environmental lead d uring the first seven years of life is associated with cognitive defic its that seem to persist into later childhood.