Relation of cumulative exposure to inorganic lead and neuropsychological test performance

Abstract

Objectives - To determine if measures reflecting chronic occupational lead exposure are associated with performance on neuropsychological tests. Method - 467 Canadian male lead smelter workers (mean (SD) age 43.4 (11.00) years, education 9.8 (3.18) years, years of employment 17.7 (7.43), and current blood lead concentration (B-Pb) 27.5 (8.4) μg dl-1) were given a neuropsychological screening battery. Time weighted average (TWA) and time integrated blood levels (IBL) were developed from B-Pb records obtained through regular medical monitoring (mean (range) TWA 40.1 (4.0-66.4) μg dl-1, mean IBL 765.2 (0.6-1625.7) μg-y dl-1). 14 neuropsychological variables were included in three multivariate analyses of covariance, with each exposure variable as the grouping variable (high, medium, and low) and age, education, score on a measure of depressive symptoms, and self reported alcohol use as the covariates. Groups did not differ in history of neurological conditions. Results - Neither the B-Pb, TWA, nor IBL was significant by multivariate analyses of covariance (MANCOVA). When years of employment, a suppressor variable, was included as a covariate, IBL exposure groups differed significantly on digit symbol, logical memory, Purdue dominant hand, and trails A and B. Conclusions - A dose-effect relation was found between cumulative exposure (IBL) and neuropsychological performance at a time when current B-Pb concentrations were low and showed no association with performance.