Metal Exposure as a Mixture and Intellectual Function in Adolescence in Bangladesh

Abstract

Background: Exposure to inorganic arsenic (As) is associated with modest deficits in intellectual function in young children. Few studies have examined associations in adolescence or whether co-exposure to other metals such as manganese (Mn), lead (Pb), cadmium (Cd), and selenium (Se) affects the association.Objective: We evaluated whether concurrent exposure to As (as creatinine-adjusted urinary As (UAs/Cr)), the afore-listed metals in blood, and maternal UAs/Cr at baseline, a proxy for peri-natal As exposure, were associated with adolescent intellectual function.Methods: The sample comprises 726 14-16-year-olds whose mothers are participants in the Bangladesh Health Effects of Arsenic Longitudinal Study (HEALS). We used a culturally modified version of the Wechsler Intelligence Scale for Children (WISC-IV) to measure Full Scale raw scores and Bayesian Kernel Machine Regression (BKMR) to investigate the joint effects of the metals mixture on these scores. BKMR uses a flexible kernel function to identify important mixture members while accounting for the correlated exposure structure, to estimate potentially nonlinear exposure-response functions, and to evaluate complex and potentially non-additive interactions.Results: Adolescent UAs/Cr, followed by Cd, were the two most important metals in the mixture, with posterior inclusion probabilities of 95.2% and 83.2%, respectively. Both adolescent UAs/Cr and Cd were significantly associated with decreased Full Scale scores. No significant interactions between metals were observed. The overall mixture (i.e., simultaneous exposure to all metals) was consistently significantly associated with decreased Full Scale scores.Conclusion: Our findings indicate that adolescent exposure to the metals mixtures, and predominantly to As and Cd, may be neurotoxic and deserves more attention.