7 January 2015. Manganese contamination of drinking water can stain the laundry and result in an unpleasant taste, although thought to be of doubtful health significance. As late as 2011, the World Health Organization (WHO) decided to discontinue its guideline for maximal manganese in drinking water (400 µg/L, an excessive level). Because “this health-based value is well above concentrations of manganese normally found in drinking water, it is not considered necessary to derive a formal guideline value,” WHO concluded. New research suggests that this decision needs urgent revision.
Researchers from the University of Montreal examined 375 Quebec children aged 6-13 years and measured manganese in home tap water and the children’s hair. After adjustment for other factors affecting children’s neurodevelopment, manganese concentrations on both water and hair showed strong negative associations with the children’s scores on memory and attention tests. Children exposed to the highest 20% of water manganese concentrations had a decline of 8% in memory function compared to children exposed to the lowest levels of manganese. These findings suggest that chemical brain drain can result from manganese exposures at concentrations commonly encountered worldwide – much below the (former) WHO concentration limit.
The study adds important support to existing evidence that manganese contamination of drinking water is a health hazard. Other new research further adds to the concern. Two newly published studies from Brazil also showed signs of neurotoxic effects in school children from communities close to a polluting ferromanganese plant. One report focused on behavioral problems and found that girls in particular had greater problems with inattention at higher manganese exposures. The second study relied on neuropsychological tests and reported IQ deficits and other adverse findings in highly exposed children. Manganese is already considered a chemical brain drainer. The new data show adverse effects at elevated manganese concentrations that commonly occur worldwide, whether from industrial pollution or leaching from soil minerals. Inexpensive methods are available to remove manganese from the water. No matter the WHO inaction, developing brains must be protected against manganese toxicity.