A Quebec study of manganese levels in drinking water from municipal wells in eight communities along the St. Lawrence River between Montreal and Quebec City has found , as reported on the CBC, that manganese significantly lowers children's IQ levels:
The water came from municipal wells and wasn't specially treated for manganese.
"We found significant deficits in the intelligence quotient (IQ) of children exposed to higher concentration of manganese in drinking water," 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.
"Yet, manganese concentrations were well below current guidelines," she added in a release.
The average IQ of children whose tap water was in the upper 20 per cent of manganese concentration was six points below children whose water contained little or no manganese, the researchers found.
The study looked at 362 children aged six to 13. The amount of manganese from tap water and food was estimated, based on the results of a questionnaire.
Each child was also assessed with a range of tests of cognition, motor skills and behaviour.
Factors such as family income, maternal intelligence, maternal education and the presence of other metals in the water were taken into account.
Even then, few environmental contaminants have shown such a strong link with intellectual ability as manganese, said study co-author Donna Mergler, also at UQAM.
Intellectual disabilities, as reported by authorities such as the Canadian Psychological Association and the US CDC, are present in 75-80% of persons with Autistic Disorder and 41-44% of all persons with Autism Spectrum Disorders generally. It would seem worthwhile to research and explore the possible relationship between manganese and autism disorders.