Search

We identified 24 modern studies of childhood exposures to lead in relation to IQ. From this population, 12 that employed multiple regression analysis with IQ as the dependent variable and lead as the main effect and that controlled for nonlead covariates were selected for a quantitative, integrated review or meta-analysis. The studies were grouped according to type of tissue analyzed for lead. There were 7 blood and 5 tooth lead studies. Within each group, we obtained joint P values by two different methods and average effect sizes as measured by the partial correlation coefficients. We also investigated the sensitivity of the results to any single study. The sample sizes ranged from 75 to 724. The sign of the regression coefficient for lead was negative in 11 of 12 studies. The negative partial r's for lead ranged from -.27 to -.003. The power to find an effect was limited, below 0.6 in 7 of 12 studies. The joint P values for the blood lead studies were less than .0001 for both methods of analysis (95% confidence interval for group partial r, -.15 +/- .05), while for the tooth lead studies they were .0005 and .004, respectively (95% confidence interval for group partial r, -.08 +/- .05). The hypothesis that lead impairs children's IQ at low dose is strongly supported by this quantitative review. The effect is robust to the impact of any single study. [ABSTRACT FROM AUTHOR]

Historians have suggested that US president Andrew Jackson (1767-1845) experienced lead and mercury poisoning following his therapeutic use of calomel (mercurous chloride) and sugar of lead (lead acetate). To evaluate these claims, we performed direct physical measurement of 2 samples of Jackson's hair (1 from 1815, 1 from 1839). Following pretreatment and acid digestion, mercury was measured using cold vapor generation techniques, while lead levels were measured by electrothermal atomic absorption spectrophotometry. Mercury levels of 6.0 and 5.6 ppm were obtained from the 1815 and 1839 hair specimens, respectively. Lead levels were significantly elevated in both the 1815 sample (mean lead level, 130.5 ppm) and the 1839 sample (mean lead level, 44 ppm). These results suggest that Jackson had mercury and lead exposure, the latter compatible with symptomatic plumbism in the 1815 sample. However, Jackson's death was probably not due to heavy metal poisoning. [ABSTRACT FROM AUTHOR]