Mercury Exposure During Pregnancy Doesn’t Cause Autism
A new study has concluded there is no link between fish consumption during pregnancy and risk of autism. Most people are aware that the prevalence of autism spectrum disorders (ASD) has dramatically increased in the past few decades. This once rare disorder, characterized by impaired social interaction and communication, and repetitive behaviors, is now frighteningly common. Estimates vary, but the latest statistics published by the United States Centers for
Disease Control suggest the rate is as high as one in 88 children.
No one knows for sure why ASD is on the rise, but that hasn’t stopped people from speculating. The rapid escalation in diagnoses suggests a possible environmental factor, such as increased exposure to mercury. Mercury contamination in the environment is primarily due to industrial pollution, from activities like burning coal for energy.
Although a mercury-containing preservative in old vaccines was once suspected of causing autism, that link has been thoroughly debunked (Jenny McCarthy notwithstanding). But it’s true that mercury is a nerve poison, and some women have worried that eating mercury-tainted fish during pregnancy may contribute to increased risk of ASD. After all, pregnant women and children are warned by the government to limit their intake of certain species of fish, due to legitimate concerns about mercury ingestion. Methylmercury, the form present in fish, is especially toxic.
Certain top-of-the-food-chain fish species, such as sharks, tuna and swordfish, tend to concentrate the metallic element in their flesh, posing a risk to people who eat lots of these fish. For the present study, researchers studied women and children living in the Seychelles, an island nation where fish consumption is high. The women had consumed up to 12 fish meals per week during pregnancy. “This study shows no consistent association in children with mothers with mercury levels that were six to ten times higher than those found in the U.S. and Europe,” said the principal investigator. “This is a sentinel population and if it does not exist here than it probably does not exist.”
Autism and Developmental Disabilities Monitoring Network Surveillance Year 2008 Principal Investigators; Centers for Disease Control and Prevention. Prevalence of autism spectrum disorders--Autism and Developmental Disabilities Monitoring Network, 14 sites, United States, 2008. MMWR Surveill Summ. 2012 Mar 30;61(3):1-19.
Stephen J. Blumberg, Ph.D., et al.. Changes in Prevalence of Parent-reported Autism Spectrum Disorder in School-aged U.S. Children: 2007 to 2011–2012. National Health Statistics Reports. March 2013;(65).
Edwin van Wijngaarden, Philip W. Davidson, Tristram H. Smith, Katie Evans, Kelley Yost, Tanzy Love, Sally W. Thurston, Gene E. Watson, Grazyna Zareba, Christine M. Burns, Conrad F. Shamlaye, Gary J. Myers. Autism Spectrum Disorder Phenotypes and Prenatal Exposure to Methylmercury. Epidemiology, 2013; : 1 DOI: 10.1097/EDE.0b013e31829d2651