Health Disparities in Exposures to Chemicals and Pollutants Affecting Neurodevelopment: A Hybrid Systematic-Scoping Review

Abstract

Background: One in six children in the United States have a developmental disability, and widespread exposures to toxic chemicals can increase the risks for cognitive, behavioral, and social impairment in children. Project TENDR (Targeting Environmental Neuro-Development Risks) is an alliance of more than 50 leading scientists, health professionals and advocates focused on preventing exposures to toxins that harm brain development, and to eliminating disproportionate exposures to children of color and low-income children. We initiated this systematic-scoping review to map the epidemiologic literature regarding increased exposure and biological susceptibility to neurotoxic chemicals among pregnant women and children living in the U.S. who face health disparities related to social, economic or environmental disadvantage.Methods: Eligible literature included observational studies published in English, measuring neurotoxic exposures (combustion-related air pollution, lead, mercury, organophosphate pesticides, polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) or phthalates) in children aged 0-18 or pregnant women living in the U.S., and examining a social, economic or environmental health disparity. PubMed, Web of Science and CINAHL were searched in July 2019 and gray literature was evaluated. Articles were categorized by population, exposure, health disparity comparator and neurodevelopmental outcome.Results: 199 studies met the review eligibility criteria and assessed neurodevelopmental measures. The most common exposures examined were lead (37%) and combustion-related air pollution (35%), while PBDEs were the least common (1%). Neurodevelopmental outcomes included neural tube defects, Autism Spectrum Disorder, Attention-Deficit/Hyperactivity Disorder, and academic, behavioral, cognitive, intellectual and learning outcomes. Common health disparities examined included race, ethnicity, socioeconomic status, and urban or rural populations.Conclusions: The review revealed a notable gap in literature on Native American populations. Additional research on exposures to mercury, phthalates, PCBs and PBDEs may benefit our knowledge of the neurodevelopmental effects of combined exposures to neurotoxic chemicals and social, economic and environmental factors that stratify health outcomes.