Study Shows No Link In Low Mercury Exposure, Autism

ROCHESTER, N.Y.Prenatal mercury exposure is not associated with autism-like behaviors in children, according to a study published in the journal Epidemiology.

The impact of exposure to low levels of mercury on the developing brain, particularly by women consuming fish during pregnancy, has been thought by some to be associated with behavioral disorders like autism. The debate over fish consumption has long created a dilemma for expecting mothers and physicians. Despite the fact that the developmental consequences of low level exposure of mercury remain unknown, some organizations, like the U.S. Food and Drug Administration (FDA), recommend that pregnant women limit their consumption of fish. However, findings from this study contribute to the growing body of literature that suggests exposure to mercury does not play a role in the onset of these behaviors," said Edwin van Wijngaarden, Ph.D., associate professor in the University of Rochester Medical Center's (URMC) Department of Public Health Sciences and lead author of the study. "This study shows no evidence of a correlation between low level mercury exposure and autism spectrum-like behaviors among children whose mothers ate, on average, up to 12 meals of fish each week during pregnancy," he added.

The Seychelles Child Development Study, a partnership between URMC, the Seychelles Ministries of Health and Education and the University of Ulster in Ireland, was created in the mid-1980s to specifically study the impact of fish consumption and mercury exposure on childhood development. The republic of Seychelles has proven to be an ideal location to examine the potential health impacts of persistent low level mercury exposure, as the nation's residents consume fish at a rate 10 times greater than the population of the United States and Europe. The program is one of the largest ongoing epidemiologic studies of its kind.

The study involved 1,784 children, adolescents and young adults and their mothers. Researchers determined the level of prenatal mercury exposure by analyzing hair samples that had been collected from the mothers around the time of birth, a test that can approximate mercury levels found in the rest of the body including the growing fetus. Researchers then used two questionnaires to determine whether or not the study participants were exhibiting autism spectrum-like behaviors. The Social Communication Questionnaire was completed by the children's parents and the Social Responsiveness Scale was completed by their teachers. The tests, which include questions on language skills, social communication and repetitive behaviors, do not provide a diagnosis, but are widely used in the U.S. as an initial screening tool. Mercury levels of the mothers were matched with the test scores of their children, and finding show there was no correlation between prenatal exposure and evidence of autism-like behaviors.

These results are similar to those found in previous studies of the nation's children which have measured language skills and intelligence and have not observed any adverse developmental effects. Further, the study lends evidence to an emerging belief that the "good" may outweigh the possible "bad" when it comes to fish consumption during pregnancy. If in fact mercury does adversely influence child development at these levels of exposure, then the benefits of the nutrients found in the fish, like selenium, vitamin E and omega-3 fatty acids, may counteract or supersede the potential negative effects of mercury. Although, other studies have shown higher omega-6 intake during pregnancy can result in fatter children.

"This study shows no consistent association in children with mothers with mercury levels that were six to 10 times higher than those founds in the U.S. and Europe," said Philip Davidson, Ph.D., principal investigator of the Seychelles Child Development Study and professor emeritus in Pediatrics at URMC. "This is a sentinel population and if it does not exist here than it probably does not exist."