The international journal Science of the Total Environment has just published a compelling study from the Republic of Korea, where autism prevalence is high. The study identifies a strong relationship between prenatal and early childhood exposure to mercury and autistic behaviors in five-year-olds.

Lead author Jia Ryu and coauthors acknowledge mercury's potential for neurotoxicity straight away but choose to characterize previous findings on the mercury-autism relationship as "inconsistent." They attribute the seeming lack of consistency, in part, to methodological issues, especially flagging problematic cross-sectional study designs that measure autistic behaviors and mercury levels (in either blood or hair) at a single point in time. To rectify these methodological weaknesses, Ryu and coauthors report on data from a multi-region longitudinal study in the Republic of Korea called the Mothers and Children's Environmental Health (MOCEH) study.

The ongoing MOCEH study examines environmental exposures during pregnancy and childhood and their effects on children's growth and development. A unique feature is that it includes five different blood samples: maternal blood from early and late pregnancy; cord blood; and samples from children at two and three years of age. In addition, the study asks mothers to complete three follow-up surveys and—when their child reaches age five—the 65-item Social Responsiveness Scale (SRS), which assesses autistic behaviors.

Key Results

Ryu and colleagues present available data for 458 (26%) of the 1,751 mother-child pairs originally recruited into the MOCEH study. What are their key findings?