Date of Award

January 2025

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

Krystal J. Godri Pollitt

Second Advisor

Jonathan Chevrier

Abstract

Environmental influences impact health, often with enhanced susceptibility for theyoung. Understanding the sources of these environmental factors is critical for mitigating exposures. Globally, children are exposed to many sources that differ by policy, urbanization, and socioeconomic conditions. Specifically, urbanization creates variation in exposure sources that differ in rural (refuse combustion, cooking biomass combustion, indoor residual spray) and urban areas (vehicle combustion, industrial activity). Differences in policy further shape these exposure patterns by regulating pollution sources, chemical use, and environmental protections across countries. This thesis evaluated environmental exposures of children living in United States, South Africa, and Singapore contributing to a broader understanding of children’s exposomes. The Fresh Air Wristband, a passive wearable sampler, was used to characterize the exposome of 538 children from five cohorts. Eighty-six children resided in New Haven, CT, and Boston, MA; 301 children from Singapore; and 151 children from the Limpopo province of South Africa. This study utilizes ongoing research from the (1) Short-Term Longitudinal Study of the Brain Mechanisms of Childhood Irritability (fMRI), (2) Very Early Onset Inflammatory Bowel Disease (VEOIBD): Precision Molecular Diagnoses to Targeted Therapies study, (3) Venda Health Examination of Mothers, Babies, and their Environment (VHEMBE) study, (4) Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study, and (5) Singapore Preconception Study of Long-Term Maternal and Child Outcomes (S-PRESTO) study. Using the Fresh Air Wristbands, 68 chemicals were detected across cohorts, including phthalates, polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs). Across all cohorts, 12 compounds were detected with a detection frequency greater than 50%. Higher concentrations of ii PAHs and phthalates were found in both the South Africa and Singapore cohorts compared to the United States cohort (FDR adjusted p value <0.05). Age-related variation in exposure was further analyzed by cohort. In the Singapore cohort, exposure profiles were consistent despite the wide range in participant age (4-to 6-year- olds compared to 13- to 14-year-olds). The United States cohort exhibited notable age-related differences in exposure, with high variation observed between younger (8 to 13 years old) and older (primarily 10 to 18 years old)(FDR adjusted p value <0.05). Additionally, a brief analysis of environmental and chemical regulatory policies was conducted focusing on organochlorine pesticides (OCPs), flame retardants and phthalates. Phthalates, particularly those associated with plastics, were more consistently detected across the cohorts and presented differences in policy, especially regarding waste management. Both OCPs and flame retardants had detection frequencies below 50%, but the comparison across cohort provided additional insight into policy-related differences in exposure. This study explored cross-country differences in children’s exposomes and assessed the impact of geographical variation in exposure profiles, emphasizing how children’s exposures are shaped by geographic differences.

Comments

This is an Open Access Thesis.

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