31 March 2015

Mercury puts Arctic kids at risk

There is a long standing debate about the benefits of eating fish particularly for pregnant women and unborn children because of high levels of mercury in fish.
A recently published study shows how high intake of mercury is damaging brain development in Inuit children in the Arctic Quebec, Canada. Children’s IQ level was found to be linked to the intake of  marine animals with high mercury levels e.g. beluga whale, seal, walrus as well as fish.
Pregnant women in the Arctic have been urged to eat more Arctic Char as it is currently considered to be less contaminated.
The high exposure of mercury not only affects children’s IQ it can also effect attention, motor skills, heart rate and lead to respiratory problem and ear infections.

Jacobson JL, Muckle G, Ayotte P, Dewailly É, Jacobson SW. Relation of Prenatal Methylmercury Exposure from Environmental Sources to Childhood IQ. Environ Health Perspect; http://dx.doi.org/10.1289/ehp.1408554. Advance Publication: 10 March 2015
Background:
Although prenatal methylmercury exposure has been linked to poorer intellectual function in several studies, data from two major prospective, longitudinal studies yielded contradictory results. Associations with cognitive deficits were reported in a Faroe Islands cohort, but few were found in a study in the Seychelles Islands. It has been suggested that co-exposure to another contaminant, polychlorinated biphenyls (PCBs), may be responsible for the positive findings in the former study and that co-exposure to nutrients in methylmercury-contaminated fish may have obscured and/or protected against adverse effects in the latter.
Objectives:
To determine the degree to which co-exposure to PCBs may account for the adverse effects of methylmercury and the degree to which co-exposure to docosahexaenoic acid (DHA) may obscure these effects in a sample of Inuit children in Arctic Québec.
Methods:
IQ was estimated in 282 school-age children from whom umbilical cord blood samples had been obtained and analyzed for mercury and other environmental exposures.
Results:
Prenatal mercury was related to poorer estimated IQ after adjustment for potential confounding variables. The entry of DHA into the model significantly strengthened the association with mercury, supporting the hypothesis that beneficial effects from DHA intake can obscure adverse effects of mercury exposure. Children with cord mercury ≥ 7.5 μg/L were four times as likely to have an IQ score below 80, the clinical cut-off for borderline intellectual disability. Co-exposure to PCBs did not alter the association of mercury with IQ.
Conclusions:
To our knowledge, this is the first study to document an association of prenatal mercury exposure with poorer performance on a school-age assessment of IQ, a measure whose relevance for occupational success in adulthood is well established. This association was seen at levels in the range within which many U.S. children of Asian American background are exposed.

Full Article:  click here