Mixed Metals Toxicity more than the Sum of its Parts?

摘要

Most toxicologic studies focus on one chemical or toxicant at a time, although in the real world people are exposed to multiple substances at once. Metals, for example, are commonly found in combinations in air, water, and food. Now researchers have conducted a prospective epide-miologic study to examine neurodevelopmental effects of manganese-lead coexposure [EHP 120(l):126-131; Glaus Henri et al.].The study included 455 children enrolled at birth in a Mexico City longitudinal cohort study, who were followed until 36 months of age. The researchers measured blood levels of lead and manganese at 12 and 24 months of age. Cognitive, motor, and language development were assessed every 6 months from 12 to 36 months of ge using the Bayley Scales of Infant Development-II. Both lead and manganese exert their toxic effects on child development primarily through the central nervous system.Exposure to manganese and lead simultaneously was associated with greater deficits in both mental and psychomotor development than expected based on the estimated effects of exposure to either metal alone; this is consistent with a synergistic effect on neuro-development. Associations were greatest at 12 months, where Mental Development Index scores were 2.16 points lower per 1-unit increase in blood lead among children with high manganese compared with children with midrange manganese.