Home > Environment, Health > Manganese in well water linked to lower IQ scores

Manganese in well water linked to lower IQ scores


Children whose drinking water contains high amounts of manganese appear to have lower IQ scores on average than children not exposed to the metal, Canadian researchers have found.

The study of more than 350 children in Quebec communities who regularly drank well water found a striking link between manganese levels in the water and IQ scores.

The study doesn’t prove cause and effect, but as the first research to focus on the potential risks of manganese in drinking water in North America, it raises important concerns.

Manganese occurs naturally in the soil, leaching slowly from minerals and rocks. There are elevated levels of the metal in several pockets of Quebec and Canada.

“Manganese is mostly a problem for people who use groundwater,” Bouchard told CTV News Channel, noting that only about 20 per cent use of Quebec residents get their water from groundwater aquefirs; the rest get water from lakes and rivers.

She added that it’s well known that exposure to manganese in the workplace can cause toxic effects to the brain and nervous system.

“Although we know that a little dose of manganese is essential for human health, in higher doses, manganese has neurotoxic effects; it negatively impacts brain functions,” Bouchard said.

Yet the effects of long-term exposure to the metallic elelment from drinking water has been unclear.

For this study, a team of researchers from the Université du Québec à Montréal and Ecole Polytechnique de Montreal tested the tap water of 251 families from eight communities between Montreal and Quebec City. All the families drank well water.

The researchers examined 362 children from the homes, who were between the ages of 6 and 13. They measured the concentration of manganese in tap water from their home, as well as levels of iron, copper, lead, zinc, arsenic, magnesium and calcium.

Since small amounts of manganese are also found in a variety of fruits, vegetables and grains, the researchers also estimated manganese intake from diet, using a food questionnaire (In the end, the authors found that the manganese in food showed no relationship to the children’s IQ).

Finally, each child was assessed with a battery of tests assessing verbal skills, visual-spacial skills, motor skills, and behaviour.

“We found significant deficits in the intelligence quotient (IQ) of children exposed to higher concentration of manganese in drinking water,” lead author Maryse Bouchard said in a news release.

“Yet, manganese concentrations were well below current guidelines.”

Among kids whose tap water was in the upper 20 per cent of manganese concentration, their average IQ was six points below that of children whose water contained little or no manganese.

The researchers say they took into account various factors that may have affected the results, such as maternal intelligence, maternal education, and the presence of other metals in the water.

“This is a very marked effect; few environmental contaminants have shown such a strong correlation with intellectual ability,” said co-author Donna Mergler.

The results are published in the scientific journal Environmental Health Perspectives.

Manganese levels in drinking water are not regulated in Canada or the United States. The authors say that because of how common the metal is in drinking water, they think that the creation of guidelines should be considered.

The authors also note that some of the municipalities where the study was conducted have filtration systems in place on their public well systems, which removes manganese from the water.

According to Benoit Barbeau, one of the other co-authors of the study, a good solution is to filter well-drawn water with filtering pitchers that use activated carbon and resins.

“Such devices can reduce the concentration of manganese by 60 to 100 per cent depending on filter use and the characteristics of the water,” he says.

He also advises families that use well water to have their water tested for manganese.

CTV.ca News Staff

Updated: Mon. Sep. 20 2010 2:04 PM ET

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Categories: Environment, Health
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