Manganese in wells tied to low IQ21st September 2010
Children who grow up drinking water contaminated with manganese may end up much less intelligent than children who do not, according to a recent Canadian study.
The researchers found that even small amounts of manganese in drinking water could have big consequences for the developing brains of children.
Lead researcher Maryse Bouchard, adjunct professor at the University of Quebec in Montreal, said that her team found significant IQ deficits in children exposed to manganese in drinking water, even though the quantities were below national limits.
The researchers are urging national and international bodies to review their guidelines for manganese safety, as well as encouraging people to use water filters in their own homes.
For the study, the researchers used hair samples, water tests, and questionnaires to examine 362 children who lived in Quebec homes.
All of the children lived in houses supplied by groundwater which contained various metallic elements, including iron, copper, lead, zinc, arsenic, and magnesium.
Using a questionnaire about eating habits, the researchers were able to probe the amount of manganese that made its way into the children's food and drink.
After the initial assessment, the children were given a test meant to measure IQ.
The researchers found the lowest IQs in children with the highest manganese exposures, six points below children whose water did not contain manganese.
Manganese in food did not seem to play a statistical role, however.
Study co-author Donna Mergler, also a professor at the University of Quebec, said that few environmental contaminants had shown such a strong correlation with IQ development as manganese.
Manganese occurs naturally in soil and air, and is widely used in industry. In Canada, ground wells are often a source of manganese
Bouchard said that people still did not know if it was possible to reverse the effects of manganese.
She has applied for a grant that would allow her to keep studying the same children as they progress through life.
The tests were done in the Eastern Townships region of Central Quebec, as well as in the Lotbiniere region of the country.
After the researchers had concluded their study, they told each household how much manganese was in the water, and held town meetings with municipal administrators.
In Quebec, the issue of manganese mainly applies to people who live in the countryside, because Montreal's municipal supply of water is free of manganese.
Lise Chabot, of the Montreal department of public health, said that manganese was not a problem there.
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