Sex Difference of Pre- and Post-Natal Exposure to Six Developmental Neurotoxicants on Intellectual Abilities: A Systematic Review and Meta-Analysis of Human Studies

Objective: To examine sex-specific effects of exposure to developmental neurotoxicants on IQ in a systematic review and meta-analysis.

Method: We screened abstracts published before December 31, 2021, for empirical studies of six neurotoxicants (lead, mercury, polychlorinated biphenyls, polybrominated diphenyl ethers, organophosphates, and phthalates) that (1) used an individualized biomarker; (2) measured exposure during the prenatal period or before age six; and (3) provided effect estimates on general, nonverbal, and/or verbal IQ by sex. We performed separate random effect meta-analyses by sex with subgroup analyses by neurotoxicant.

Results: Fifty-one studies were included in the systematic review and 22 in the meta-analysis. Prenatal exposure to neurotoxicants was associated with decreased general and nonverbal IQ in males, especially for lead. No significant effects were found for females or verbal IQ.

Conclusion: During fetal development, males may be more vulnerable than females to general and nonverbal intellectual deficits from neurotoxic exposures, especially from lead.