CONSEQUENCES OF LEAD-EXPOSURE AND IRON SUPPLEMENTATION ON CHILDHOOD DEVELOPMENT AT AGE 4 YEARS

For a prospective study of lead exposure and early development, we rec ruited pregnant women from a smelter town and a nonlead-exposed town i n Yugoslavia and followed them and their children through age 4. For 3 32 children seen at age 4, mean scores on the McCarthy Scales General Cognitive Index (GCI) in the exposed and nonexposed towns were 81.3 an d 86.6, respectively; geometric mean blood lead concentrations (BPb) w ere 39.9 and 9.6 mug/dl, respectively. Potential confounders included the quality of the HOME environment; maternal age, intelligence, educa tion, and language; birthweight and gender. These showed predictable a ssociations with 4-year intelligence, accounting for 42.7% of the vari ance in GCI. Following adjustment for these variables and for concurre nt Hgb, we found significant independent adverse associations between GCI and BPb's, measured at 6-month intervals since birth. At age 4, BP b accounted for an incremental 3.5% of the variance in GCI, such that the estimated loss in GCI associated with an increase in BPb from 10-2 5 mug/dl was 3.8 points. The Perceptual-Performance subscale of the Mc Carthy was most sensitive to Pb exposure, a result consistent with fin dings from prospective studies in Boston and Port Pirie.