Early-life Lead Exposure and Neurodevelopmental Disorders in Children: An Umbrella Review of Systematic Reviews

Introduction: Lead is a systemic toxicant, producing widespread adverse health effects in both adults and children. Lead has proven to be particularly harmful to the developing brains/nervous systems of infants, toddlers, and children because their bodies absorb lead more readily than that of their adult counterparts. Approximately 500,000 children had elevated blood lead levels (BLLs) above 5.0 µg/dL in 2017 and nearly 50% had concentrations >1 μg/dL. Objective: This umbrella review appraised systematic reviews examining the relationship between lead exposure in children with the development of neurodevelopmental disorders (NDDs). Methods: Systematic reviews published between January 2000-March 2022 were reviewed. The exposure of interest was lead for children/pregnant persons/fetuses, and the outcome was development of NDDs. A search of lead exposure and childhood neurodevelopmental outcomes was performed in Ovid. Results: The review yielded 122 studies. After removing duplicates, 118 studies remained, of which 38 passed abstract screening and 11 passed full-text screening. Three included reviews focused on lead-associated Autism Spectrum Disorder (ASD), where two of the three studies agreed that lead plays a role in the development of ASD. Four studies concentrated on Attention-Deficit/Hyperactivity Disorder (ADHD), where all observed a connection between lead exposure and ADHD diagnosis/symptoms. The remaining four reviews mentioned lead’s impact on intellectual disability, learning disorders, fine motor skills, or executive functioning outcomes. Three of the four reviews assessed lead’s impact on intellectual disability/cognitive function, where each concluded that lead contributed to neurodevelopmental impairments. Conclusion: There is overall agreement that lead exposure creates adverse health outcomes in children and is realized even at low BLLs. Findings from this review highlight the need for improved understanding of mechanisms underpinning lead exposure during periods of critical vulnerability in children and development of NDDs. Public Health Significance: Childhood lead exposure and poisoning is a major public health concern across numerous countries, including the U.S. NDDs in children also constitute a significant public health concern as prevalence rates are rising. As lead is a known neurotoxicant and has been implicated in the development of NDDs, this review was conducted to summarize and synthesize available systematic reviews on this growing public health concern