Boucher O, G Muckle, JL Jacobson, RC Carter, M Kaplan-Estrin, P Ayotte, É Dewailly, SW Jacobson. 2014. Domain-specific effects of prenatal exposure to PCBs, mercury, and lead on infant cognition: Results from the Environmental Contaminants and Child Development Study in Nunavik. Environmental Health Perspectives. http://dx.doi.org/10.1289/ehp.1206323.
|The Inuit are among the most contaminated people on Earth. They eat marine mammals, high on food webs, that are contaminated by industrial chemicals.|
Babies in Arctic Canada are at risk of specific effects on their mental abilities, depending on which contaminants they are exposed to in the womb, according to a new study.
While lead, methylmercury and polychlorinated biphenyls (PCBs) all are linked to neurological effects, each seems to have a different effect on infants, the scientists concluded. For example, PCBs seemed to impair the babies’ ability to recognize things they have seen.
The study involved 94 Inuit infants and their mothers from Nunavik, in northern Quebec. PCBs, mercury and other pollutants hitchhike north via prevailing winds and currents from industrialized areas, and then accumulate in food webs, predominantly in the eastern Arctic. Because the Inuit in Canada and Greenland eat top predators such as beluga whales and seals, they are among the world’s most contaminated human beings.
The scientists measured the babies’ prenatal exposure to the three contaminants by testing cord blood, and then administered standard mental development tests at 6.5 months and 11 months. The tests involve retrieving toys from under cloth covers, recognizing photographs and performing tasks related to motor skills.
The research was designed to pinpoint the exact damage inflicted on developing brains, which will help experts determine which effects to look for when the children reach school age.
“Each contaminant was independently associated with impairment of distinct aspects of cognitive function with long-term implications for cognitive development – PCBs with visual recognition memory, methylmercury with working memory and an early precursor of executive function, lead with processing speed – deficits that can already be detected during the first year of life,” the authors wrote.
For the research, scientists at Quebec’s Centre de Recherche du CHUQ, who have been studying effects of contaminants on Inuit children for two decades, teamed up with Wayne State University scientists who conducted groundbreaking work in the Great Lakes linking PCBs to reduced IQs in the 1990s.
“This specificity is consistent with our previous findings suggesting that the recognition memory deficit is specific to prenatal PCB exposure and different from effects of other neurotoxicants, including alcohol and cocaine,” the authors wrote.
Similar findings have been reported for children in Michigan, Oswego, N.Y., the Faroe Islands and Taiwan – all areas where many babies are highly exposed to PCBs or mercury from their mothers’ consumption of fish or marine mammals.
“These data provide compelling evidence for the utility of narrow band measures of infant cognition in studies of neurotoxic pollutants,” the researchers wrote.
They added that their findings support efforts in Nunavik to reduce consumption of marine mammals. Pregnant women there are urged to eat Arctic char and other finfish instead.