Water Manganese Exposure and Children’s Intellectual Function in Araihazar, Bangladesh

TLDR

Manganese exposure through drinking water is poorly understood, yet many domestic wells exceed the EPA’s 300 μg Mn/L advisory level. This cross‑sectional study examined whether long‑term consumption of tube‑well water with an average of 793 μg Mn/L affects the intellectual function of 142 ten‑year‑old children in Araihazar, Bangladesh. Children underwent medical exams, completed Wechsler Intelligence Scale for Children‑III tests, and provided urine and blood samples to measure manganese, arsenic, lead, and hemoglobin levels. Higher water manganese concentrations were dose‑dependently associated with lower Full‑Scale, Performance, and Verbal IQ scores, while arsenic had no effect, indicating that children in both Bangladesh and the United States are at risk for manganese‑induced neurotoxicity.

Abstract

Exposure to manganese via inhalation has long been known to elicit neurotoxicity in adults, but little is known about possible consequences of exposure via drinking water. In this study, we report results of a cross-sectional investigation of intellectual function in 142 10-year-old children in Araihazar, Bangladesh, who had been consuming tube-well water with an average concentration of 793 μg Mn/L and 3 μg arsenic/L. Children and mothers came to our field clinic, where children received a medical examination in which weight, height, and head circumference were measured. Children's intellectual function was assessed on tests drawn from the Wechsler Intelligence Scale for Children, version III, by summing weighted items across domains to create Verbal, Performance, and Full-Scale raw scores. Children provided urine specimens for measuring urinary As and creatinine and were asked to provide blood samples for measuring blood lead, As, Mn, and hemoglobin concentrations. After adjustment for sociodemographic covariates, water Mn was associated with reduced Full-Scale, Performance, and Verbal raw scores, in a dose–response fashion; the low level of As in water had no effect. In the United States, roughly 6% of domestic household wells have Mn concentrations that exceed 300 μg Mn/L, the current U.S. Environmental Protection Agency lifetime health advisory level. We conclude that in both Bangladesh and the United States, some children are at risk for Mn-induced neurotoxicity.