According to a new study, children who drink water containing high concentrations of manganese seem to have lower IQs than kids who are not exposed to the naturally occurring metal that’s commonly found in ground water. The study, which was published online today in the journal Environmental Health Perspectives, found that kids who drank water in the upper 20 percent of manganese concentration had average IQ scores six points below kids whose tap water contained little to no manganese. Researchers examined 362 kids aged 6 to 13 in an area of Quebec where manganese levels are particularly high, and communities get drinking water from municipal wells that aren’t specifically treated for manganese.

While manganese is an essential nutrient, in excess it can damage the nervous system. “The findings from the present study support the hypothesis that low-level, chronic exposure to manganese from drinking water is associated with significant intellectual impairments in children,” said the study’s lead author, Maryse Bouchard of the University of Quebec at Montreal’s Centre for Interdisciplinary Studies in Biology, Health, Society and Environment. “I studied mercury, lead, PCBs, and usually the associations we see are more in the range of one IQ point, two, maybe three IQ points,” she said. “But this is a very strong effect,” she told CBC News.

Manganese levels in drinking water are not regulated in Canada or the US, but the World Health Organization gives a recommendation for maximum levels of 400 micrograms per liter. What’s particularly concerning is that the manganese-contaminated tap water drank by 96 percent of the children in this study fall within these safe guidelines.

“Because of the common occurrence of this metal in drinking water and the observed effects at low manganese concentration in water, we believe that national and international guidelines for safe manganese in water should be revisited,” Bouchard said.

What You Can Do

If your family drinks water from a well, have your water tested for manganese. It can be removed through filtering processes, so there is no need to drink water with high levels of manganese. You can do the same for your tap water — filter it to remove manganese and other potential toxins that can wind up in ground water.

+ Read the full study from Environmental Health Perspectives: Intellectual Impairment in School-Age Children Exposed to Manganese from Drinking Water
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