[Cognitive and performance capacity among adolescents living near a lead and zinc smelter].

To estimate potential early adverse effects on the Central Nervous System (CNS) due to very low exposure to inorganic lead, the Intelligence Quotient (IQ) of adolescents with present blood lead concentrations (PhB) generally below 10 micrograms/dl was measured. We analyzed blood lead concentration and individual IQ of 32 Sardinian adolescents living in Portoscuso, a town 2 Km far from a lead smelter, and of other 32 controls living in S. Antioco, a town about 15 Km far from the same smelter. The Wechsler Intelligence Scale for Children Revised (WISC-R) was administered. The relation between IQ and blood lead concentration was estimated by linear multivariate models adjusting for several potential confounders, such as the educational and socio-economic level of the parents. The blood lead concentration was in average significantly higher in the Portoscuso group compared to controls. The linear model applied to the total population studied (n 64) showed that the blood lead concentration was inversely and significantly associated with IQ, with an extrapolated decline of 1.29 points in total IQ for each microgram/dl increase of blood concentration. According to the recent scientific literature on this topic, results of our pilot study suggest the need to further lower the definition of an elevated blood lead concentration for children to a threshold significantly below 10 micrograms/dl, value till now considered "safe" for the children's CNS.