Hair Manganese and Hyperactive Behaviors: Pilot Study of School-Age Children Exposed through Tap Water

TLDR

Neurotoxic effects are known to occur with inhalation of manganese particulates, but very few data are available on exposure to Mn in water. The study aimed to test whether greater manganese exposure through drinking water would increase hair manganese levels and be linked to higher hyperactive behaviors. A pilot study of 46 children in Quebec compared hair manganese and behavioral ratings between homes supplied by two wells with differing manganese concentrations, using the Revised Conners’ Rating Scale. Children from the high‑Mn well had significantly higher hair manganese and higher oppositional and hyperactivity scores, with all children scoring ≥65 on these subscales having hair manganese above 3.0 µg/g.

Abstract

BackgroundNeurotoxic effects are known to occur with inhalation of manganese particulates, but very few data are available on exposure to Mn in water. We undertook a pilot study in a community in Québec (Canada) where naturally occurring high Mn levels were present in the public water system. Our objective was to test the hypothesis that greater exposure to Mn via drinking water would be reflected in higher Mn content in hair which, in turn, would be associated with increased level of hyperactive behaviors.MethodsForty-six children participated in the study, 24 boys and 22 girls, 6–15 years of age (median, 11 years). Their homes received water from one of two wells (W) with different Mn concentrations: W1: mean 610 μg/L; W2: mean 160 μg/L. The Revised Conners’ Rating Scale for parents (CPRS-R) and for teachers (CTRS-R) were administered, providing T-scores on the following subscales: Oppositional, Hyperactivity, Cognitive Problems/Inattention, and ADHD Index.ResultsChildren whose houses were supplied by W1 had higher hair Mn (MnH) than those supplied by W2 (mean 6.2 ± 4.7 μg/g vs. 3.3 ± 3.0 μg/g, p = 0.025). MnH was significantly associated with T-scores on the CTRS-R Oppositional (p = 0.020) and Hyperactivity (p = 0.002) subscales, after adjustment for age, sex, and income. All children with Oppositional and Hyperactivity T-scores ≥ 65 had MnH > 3.0 μg/g.ConclusionsThe findings of this pilot study are sufficiently compelling to warrant more extensive investigations into the risks of Mn exposure in drinking water.