But analysis of prenatal/infant mercury exposures is needed to assess causation.
A study published online Oct 19 in the peer-reviewed journal Environmental Health Perspectives found that 2- to 5-year-old children diagnosed with autism or autism spectrum disorders (AU/ASD) had blood mercury levels similar to those of typically developing control children after adjusting for a variety of sources.
The study was conducted through Childhood Autism Risks from Genetics and the Environment (CHARGE), an ongoing study to identify and understand factors contributing to childhood AU/ASD and developmental delays. [To read the free full text of the article “Blood Mercury Concentrations in CHARGE Study Children with and without Autism,” click here.]
Mercury has drawn particular attention in terms of AU/ASD because of its known neurotoxicity.
The objective of this study was:
• To compare blood mercury concentrations in typically developing children to concentrations in children with AU/ASD or developmental delay without autism,
• And to analyze whether differences in mercury sources such as fish consumption explained any differences in blood mercury levels among these groups.
The authors also examined dental, medical (including vaccinations) and pharmaceutical sources of mercury exposure.
The authors reported that:
• Consumption of tuna, other ocean fish and freshwater fish was the primary predictor of total blood mercury for both typically developing children and those with AU/ASD or developmental delay.
• Higher blood mercury was also seen in children with amalgam dental fillings who ground their teeth and/or chewed gum.
• Children with AU/ASD were less likely to consume tuna, other ocean fish and freshwater fish,
• And these children’s blood mercury was significantly reduced compared with that of typically developing controls when differences in fish intake were not accounted for.
This case-control study represents the most rigorous examination to date of differences in circulating blood mercury associated with AU/ASD. However, it did not address whether mercury could be a causative factor in AU/ASD.
Analysis of specimens taken before diagnosis will be needed to assess the role of prenatal or early-life mercury exposures in the etiology of autism.
Authors of the paper included Irva Hertz-Picciotto, Peter G. Green, Lora Delwiche, Robin Hansen, Cheryl Walker and Isaac N. Pessah. This work was supported by the National Institutes of Health/National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency through the Science to Achieve Results (STAR) program, and the Medical Investigations of Neurodevelopmental Disorders (MIND) Institute.
Source: Environmental Health Perspectives journal news release, Oct 19, 2009