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Relationship between prenatal methylmercury exposure and IQ: a meta-analysis
Leonid Kopylev1, Michael Dzierlenga1, Yu-Sheng Lin1
1Office of Research and Development, US Environmental Protection Agency, 1200 Pennsylvania Ave, Washington DC, NW, 20460, USA.
Exposure and Health
|August 1, 2026
Summary
Methylmercury (MeHg) exposure in pregnancy can harm child development. This study found lower IQ scores in children exposed to MeHg, impacting neurodevelopment and future economic analyses.
Area of Science:
- Environmental Health
- Neuroscience
- Toxicology
Background:
- Methylmercury (MeHg) is a known developmental neurotoxicant.
- Previous research indicated IQ decrements in children exposed to high MeHg levels.
- Recent studies have investigated MeHg's effects at lower exposure levels, but findings remain unsynthesized.
Purpose of the Study:
- To systematically synthesize findings from recent epidemiological studies on the relationship between prenatal MeHg exposure and child IQ.
- To update previous meta-analyses by including data from lower exposure levels.
- To provide updated estimates for economic cost-benefit analyses.
Main Methods:
- A comprehensive literature search was conducted for studies published between 1998 and 2025.
- Studies were evaluated for risk of bias and sensitivity.
- Quantitative findings from high or medium confidence studies were extracted and standardized.
- A meta-analysis was performed on seven populations from five new cohorts using the R package Metafor.
Main Results:
- The meta-analysis included studies with prenatal MeHg exposure levels ranging from 0.60 to 12.8 μg/L maternal blood.
- A decrement of 0.407 IQ points (95% CI: -0.962, 0.147) per μg/L MeHg in maternal blood was observed in recent cohorts.
- IQ was measured in children between 3.5 and 12 years of age.
Conclusions:
- Prenatal methylmercury exposure is associated with decreased IQ in children, even at lower exposure levels.
- This updated meta-analysis provides crucial data for refining risk assessments and economic evaluations.
- Further research and updated cost-benefit analyses should consider these findings.
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