Neuropsychological studies in children with elevated tooth-lead concentrations

Abstract

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.

Bone lead content assessed by L-line x-ray fluorescence in lead-exposed and non-lead-exposed suburban populations in the United States.

“…Mean tibial Pb levels in each of the three age groups of Throop, where all residents lived within 1 mile of the factory, were significantly higher than baseline. The bone Pb levels reported here for both suburban communities were comparable to those in other studies of normally and excessively exposed children (6,(26)(27)(28), in teenagers (16,29), and in adults (18,19,30,31) measured by KXRF and by atomic absorption spectroscopy (AAS). For instance, Pb concentrations of 2-5 ppm (wet weight), measured by AAS, have been reported in the whole teeth of normally exposed children (6), compared with values of 12-18 ppm in smelter-exposed children (27,28).…”

“…The bone Pb levels reported here for both suburban communities were comparable to those in other studies of normally and excessively exposed children (6,(26)(27)(28), in teenagers (16,29), and in adults (18,19,30,31) measured by KXRF and by atomic absorption spectroscopy (AAS). For instance, Pb concentrations of 2-5 ppm (wet weight), measured by AAS, have been reported in the whole teeth of normally exposed children (6), compared with values of 12-18 ppm in smelter-exposed children (27,28). Somervaille et al (18), using the KXRF technique, reported a bone Pb content of 9 + 2 ppm (mean + SD) in 20 normally exposed adults, in contrast to a value of 18 ± 2 ppm in adult workers in each of two Pb-processing factories in England.T Average LXRF-estimated bone Pb values in Throop residents approximated those of the KXRF estimates for occupationally exposed English workers (18).…”

Developmental aspects of environmental neurotoxicology: Lessons from lead and polychlorinated biphenyls

“…In most studies lead in blood (PbB), either measured at one point in time or, as is true for prospective studies, measured sequentially from birth until time of testing, is taken as a marker of individual exposure to lead. Some studies have also used tooth lead concentrations as markers of long-term cumulative lead uptake [8,9], but for both analytical and practical reasons this measure has not replaced blood lead concentrations as markers of exposure.…”

Effect of Chronic Lead Exposure on Pro-Apoptotic Bax and Anti-Apoptotic Bcl-2 Protein Expression in Rat Hippocampus In Vivo

“…The entry of lead into the central nervous system is facilitated in young animals and children, because the blood-brain barrier is not completely mature (Goldstein 1993(Goldstein , 1994. The symptoms of lead neurotoxicity in children include, a reduction in IQ (Bellinger et al 1991(Bellinger et al , 1992Winneke and Kramer 1997), impairment of auditory and language function (Lansdown et al 1986;Schwartz and Otto 1997;Bleecker et al 2005), impaired neuropsychological functioning (Canfield et al 2004) and disturbances of learning and memory (Winneke et al 1983;Canfield et al 2004;Bleecker et al 2005). In spite of several decades of knowledge and research on lead neurotoxicity, the precise mechanisms by which lead exerts its neurotoxic effects, is still unknown.…”