Détermination de la concentration de manganèse dans l’eau potable associée à des déficits cognitifs chez l’enfant
Manganese (Mn) is an essential nutrient but can induce neurotoxic effects elevated exposure levels. Recent studies have reported that exposure to Mn in drinking water could be associated with a decrease in cognitive abilities in children. However, the concentration at which these effects appear has not been estimated in previous studies. Therefore, the objective of my master’s thesis was to estimate the concentration of Mn in drinking water associated with different predefined levels of cognitive deficits in children. To achieve this, data from two cross-sectional studies from Canada were pooled resulting in a sample of 630 children from ages 5-14 years. The intelligence quotient (IQ) of each child was assessed and the concentration of Mn was measured from the tap water of their residence. We used the software Bayesian Benchmark Dose Analysis to estimate the benchmark concentrations of water Mn associated with a 1%, 2% and 5% decrease in IQ, as well as the lower limits of the 95% credible interval (LL95%CI). Our results show that the concentration of Mn in water associated with a 1% decrease in IQ was 121 μg/L (LL95%CI, 70 μg/L), while those for a decrease of 2% and 5% points were 241 μg /L (LL95%CI, 141 μg/L) and 611 μg/L (LL95%CI, 367 μg/L) respectively. Since the results suggest that the association between Mn in water and IQ is different between the sexes, we also conducted sex-stratified analyses. The concentration of Mn in water associated with a 1% decrease in IQ was 169 μg/L (LL95%CI, 68 μg/L) in boys and 73 μg/L (LL95%CI, 8 μg/L) in girls.  As there is currently no established health-based guideline for Mn in drinking water in Canada, these results can guide decision-makers in developing a guideline aimed at protecting children from neurotoxicity from this metal.
Environmental epidemiology Drinking water Manganese Children Neurotoxicity IQ Benchmark concentration