Published in the journal, Environmental Health Perspectives on Monday, the study, Intellectual Impairment in School-Age Children Exposed to Manganese from Drinking Water examined the link between manganese, groundwater and children’s intellect; finding a very strong correlation. The research results are free to access and are available as a pdf.
In a press release announcing the report, the researchers stated
“… children exposed to high concentrations of manganese in drinking water performed less well in tests of intellectual skills that children are less exposed.
… The neurotoxic effects of manganese exposure are well known in the workplace. Present in the soil, this metal is also found naturally in groundwater. Several regions in Quebec, Canada and around the world have naturally high levels of manganese in the groundwater. Are there dangers? What may be its effect on children’s health? This is the first study to focus on potential risks of exposure to manganese in drinking water in North America.”
After accounting for manganese from food, the ingestion of other metals found in the drinking water, and many other factors that might impact findings, such as maternal depression and smoking; the researchers noted the association between levels of manganese from groundwater and intellect held. Most alarmingly, the study found
“… a very significant reduction of intelligence quotient (IQ) of children has been observed in connection with the presence of manganese in drinking water, and that at concentrations of manganese currently considered low, and without risk to health.”
The impacts of those low levels of maganese were quite striking.
“The children in whom the concentration of manganese in water was 20% in the highest had an average IQ of 6 points lower than children whose water does not contain manganese.”
The researchers also concluded that humans metabolize manganese from water differently than from food.
Small amounts of manganese, like many other metals, are needed for human health, but too much manganese can create a host of health problems. Too much manganese becomes a neurotoxin for the human brain.
Some municipalities already filter out metals from drinking water. For those living in communities that do not filter out metals, study co-author Benoit Barbeau recommends
“… the use of filtering pitchers that contain a mixture of resin and activated carbon. Such devices can reduce the concentration of manganese 60-100% depending on the level of filter usage and characteristics of the water to be treated.”
The research project used hair clippings and water testing to determine how much manganese the 362 children, aged between 6 and 13 years, had taken in over time through drinking water.
Health Canada has estimated the average Canadian ingests, through a variety of sources, about 4.7 mg of manganese daily. Health Canada goes on to state
“… The Recommended Daily Intake (RDI) of manganese for Canadians has yet to be established. In a recent comprehensive literature survey of studies of manganese metabolism in humans, it was concluded that previous estimates for a safe and adequate daily dietary allowance for manganese (2.5-5.0 mg/d) were too low, and a new range of 3.5-7.0 mg/d was recommended for adults.(31) A statistical analysis of the metabolic studies showed that a daily manganese intake of approximately 5 mg is required to consistently maintain a positive balance.”
However, the Quebec study demonstrated that lower levels of manganese ingested through drinking water provided sufficient accumulation in children so as to impair with brain functioning. The researchers also noted that Canada has no guidelines for manganese levels in drinking water, and manganese levels are thus not regulated.
The report concludes
“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.”