Mercury exposure and childhood outcomes: An overview of systematic reviews

The objective of this review was to summarize recent and relevant systematic reviews (SRs) that assessed relationships between mercury (Hg) exposure during pregnancy, lactation, and childhood and child outcomes.

Three electronic databases were searched for SRs published between January 2018 to December 2024 about Hg exposure (of any form or source, including seafood), during pregnancy, lactation or childhood and child outcomes including: anthropometrics, neurodevelopment, attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD), exposure biomarkers, cardiometabolic health, immunity, and birth outcomes. All articles were screened at title/abstract and full-text levels by two independent reviewers. A MeaSurement Tool to Assess systematic Reviews (AMSTAR) 2 critical appraisal tool was used to assess the methodological quality of the included SRs.

Twenty-nine SRs of observational studies were identified that assessed Hg during pregnancy (n = 19) and/or childhood (n = 17). During pregnancy, results from the SRs suggested that higher Hg may be associated with higher risk of birth defects, pre-term birth, ADHD, ASD, and low birth weight, length, and head circumference. Results varied for neurodevelopment outcomes in the child, likely due to co-exposure with seafood during pregnancy, variation in response by sex of the child, and etiological differences among developmental domains. During childhood, SRs suggested that higher Hg may be associated with higher risk of ADHD and adverse neurodevelopment, growth, and body composition outcomes. Also, Hg concentrations were higher in children with ASD than those without in case-control studies but longitudinal data were lacking. Evidence on methylmercury exposure from seafood during pregnancy and childhood was limited and inconclusive.

Mercury exposure during pregnancy and childhood is recognized as a major public health concern. However, more research is needed that specifically examines methylmercury from seafood to better inform future dietary recommendations.