TOOTH LEAD LEVELS AND IQ IN SCHOOL-AGE-CHILDREN - THE PORT-PIRIE COHORT STUDY

The relation between lead concentration in deciduous central upper inc isor teeth and intellectual functioning was examined in 262 children w ho were followed from birth to age 7 years in the lead smelter town of Port Pirie, South Australia, and its environs. Intellectual functioni ng of the children was assessed over the 3-year period from 1986-1989 with the revised Wechsler Intelligence Scale for Children (WISC-R) whi le each child was in his or her eighth year. There was an inverse rela tion between tooth lead concentration and intellectual development; th e intelligence quotient declined by 2.6 points (90% confidence interva l (CI) 0.13-4.9) for each natural-log unit increase in tooth lead conc entration, expressed in parts per million. Some WISC-R subscales were more strongly associated with lead exposure than others. In particular , tooth lead was significantly negatively associated with scores for t he ''Block Design'' test (partial regression coefficient -1.25 points per unit of natural-log tooth lead; 90% CI -0.61 to -1.89). No statist ically significant interaction between a child's sex and tooth lead co ncentration was found for any of the WISC-R scales. These findings are in agreement with previously published results from this cohort for w hich serial blood lead concentrations were used to estimate lifetime l ead burden.