Neuropsychological studies in children with elevated tooth-lead concentrations. II. Extended study

Results from neuropsychological tests, collected under double-blind-precautions, were evaluated for 115 schoolage children (mean age: 9.4 years) living in a lead smelter area (Stolberg, FRG). Tooth-lead concentrations (PbT) from shed incisor teeth as measures of longtime lead-exposure were available for these children (mean = 6.16 ppm; range: 1.9-38.5 ppm), and for 83 of them blood-lead concentrations (PbB) were available as well (mean = 14.3 micrograms/dl; range: 6.8-33.8 micrograms/dl). The following functional capacities were tested: intelligence (German WISC), perceptual-motor integration (Göttinger Formreproduktionstest = GFT, Diagnosticum for Cerebralschädigung = DCS), reaction performance (Wiener Determinationsgerät), finger-wrist tapping-speed, and repetitive cancellation-performance (Differentieller Leistungstest). In addition standardized behavior ratings were obtained by the examiners, the mothers, and the teachers. Multiple stepwise regression-analysis (forced solution) was calculated for outcome-variables and Pb-tooth, including age, sex, duration of labor, and socio-hereditary background as covariates. Significant (P less than 0.05) or near-significant (P less than 0.1) association was established between Pb-tooth and GFT-performance (errors), reaction-performance (false reactions), and four behavioral dimensions as rated by the mothers, namely distractability, restlessness, lack of information, and wasting of time; the proportion of explained variance never exceeded 6%, however. No significant association was found between PbT and WISC verbal-IQ after the effects of "socio-hereditary background" had been eliminated, although there was still a tendency for high level-children (PbT greater than 10 ppm) to be inferior to low level-children (PbT less than or equal to 4 ppm) by 4.6 IQ-points after correction for confounding. There was a near-significant, inverse relationship between finger-wrist tapping-speed and Pb-blood. The results are discussed within the framework of attention-deficit disorder, and compared to neurobehavioral Pb-effects from animal-experiments, which provide suggestive evidence for a causal relationship between developmental lead-exposure and certain neurobehavioral deficits.