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WSU researchers discover mercury exposure affects children's IQs

Study adds weight to connection between seafood consumption, mental ability

April 6, 2015


DETROIT - Prenatal exposure to foods contaminated with brain-damaging mercury has adverse effects on the IQs of schoolchildren in remote Arctic villages, where mothers regularly eat beluga whale, fish, seal and walrus, all traditional foods that are now contaminated with mercury.

The study is the first to link prenatal mercury exposure to poor performance on an IQ test for schoolchildren, and adds considerable weight to the connection between seafood consumption and reduced mental ability in children. Sandra Jacobson, Ph.D., and Joseph Jacobson, Ph.D., both Wayne State University professors of Psychiatry and Behavioral Neurosciences, conducted the research with scientists at Laval University in Quebec.

"One of the real values of our research is that it addresses some of those differences in a completely independent study population and helps to reduce the degree of controversy," Dr. Sandra Jacobson told National Geographic for a recent article.

"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" appears in the March 2015 issue of Environmental Health Perspectives, the journal of the National Institute of Environmental Health Sciences.

The scientists reported that the effect on IQs may have been stronger, but the brain-benefiting fatty acids in the marine diet could be obscuring adverse effects. According to the study, the Nunavik population is among the most highly exposed to polychlorinated biphenyls, or PCBs, and mercury on earth because of long-range transport of the compounds by atmospheric and ocean currents. The compounds accumulate in the area's fish and sea mammals. Nunavik is a large Inuit territory in the northernmost part of the Canadian province.

In the study, the IQs of 282 Nunavik children 8 to 14 years old were compared with the amounts of mercury in their umbilical cord blood. Nearly eight of every 10 women of childbearing age in some Nunavik villages have blood mercury levels exceeding Canada's health guideline. On the IQ tests, the children with the highest mercury levels in their cord blood scored, on average, 4.8 points lower than children with lower levels, according to the study. Children with the highest levels were four times more likely to have an IQ below 80, the clinical cutoff for a learning disability.

The Jacobsons have studied the effects of in utero exposures to environmental contaminants on infant and child development for more than 30 years, including in the United States and Michigan. PCBs have been banned here since the 1970s, but in the 1990s WSU scientists found that in utero exposure to PCBs in the Great Lakes was linked to memory and attention problems, abnormally weak reflexes in newborns, developmental delays, poorer visual and intellectual function, and more.

The current study supports public health recommendations aimed at limiting consumption of highly contaminated traditional foods, especially among women of childbearing age. Because of their low contaminant levels and high fatty acids concentrations, finfish species, such as Arctic char, are good substitutes for these foods.

The research was supported by grants from the National Institutes of Health National Institute of Environmental Health Sciences (R01-ES007902), Northern Contaminants Program, Indian and Northern Affairs Canada, Health Canada, Hydro-Qu├ębec (Environmental Child Health Initiative) and the State of Michigan Lycaki-Young Fund.

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