Associations of Metals and Neurodevelopment: a Review of Recent Evidence on Susceptibility Factors

• Published in: Current epidemiology reports 2020-12, Vol.7 (4), p.237-262
• Main Authors: Bauer, Julia A., Fruh, Victoria, Howe, Caitlin G., White, Roberta F., Claus Henn, Birgit
• Format: Article
• Language: English
• Subjects: Environmental Epidemiology (F Laden and J Hart; Epidemiology; Medicine; Medicine & Public Health; Section Editor; Topical Collection on Environmental Epidemiology
• ISSN: 2196-2995; 2196-2995
• DOI: 10.1007/s40471-020-00249-y

Purpose of Review Epidemiologic evidence exists that many metals are associated with adverse neurobehavioral effects in young children, including lead (Pb), methylmercury (meHg), manganese (Mn), and arsenic (As) (Antunes dos Santos et al. J Trace Elem Med Biol. 38:99–107; Tolins et al. Ann Glob Health. 80(4):303–14; Vollet et al. Curr Environ Health Rep. 3(4):392–404; Bellinger Curr Opin Pediatr. 20(2):172–7). Importantly, chemical insult can vary depending on host factors and exposure circumstance. This systematic review summarizes the recent literature investigating modifying factors of the associations between metals and neurodevelopment, including immutable traits (sex or genetics) or exposure conditions (timing or co-exposures). Recent Findings Of the 53 studies included in this review, the number investigating the modification of exposure effects was as follows: 30 for sex, 21 for co-exposures, 12 for timing of exposure, and six for genetic modifiers. Sex-specific effects of metal-neurobehavioral associations were inconclusive for all metals, likely due to the heterogeneity of outcome domains assessed and the exposure time points measured. Seven studies evaluated both sex and exposure timing as modifying factors using deciduous teeth or other biomarkers with repeated measures to characterize metals exposure over time. Only five studies used statistical methods for mixtures to evaluate associations of more than two metals with neurobehavioral domains. Summary Despite the expansion of research on susceptibility to the neurodevelopmental effects of metals exposure, considerable gaps remain. This work remains critical, as characterizing susceptible subpopulations can aid in identifying biological mechanisms and is fundamental for the protection of public health.