Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Public Health

Major Professor

Russell Kirby, Ph.D.

Co-Major Professor

Foday Jaward, Ph.D.

Committee Member

Marie Bourgeois, Ph.D.

Committee Member

Henry Alegria, Ph.D.

Keywords

Breast Milk, Dust, NHANES, PAHs, Pesticides, Phthalates

Abstract

Environmental chemicals are ubiquitous and can contribute to human exposure. These exposures can result in long-term health consequences if they occur in early life. However, exposures to environmental chemicals are not evenly distributed throughout childhood. As a result, there exists variation in the levels of chemical exposure depending on the developmental stages, pathways of exposure, and broader systemic factors. However, in early life, limited research exists on exposures to environmental chemicals, particularly phthalates, pesticides, and polycyclic aromatic hydrocarbons (PAHs). In addition, environmental exposures to phthalates, pesticides, and PAHs, considering life stages, have not been fully explored. Hence it is imperative to characterize exposures to environmental chemicals such as phthalates, pesticides, and PAHs depending on children's life stages.

The overarching goal of this dissertation is to characterize exposures to phthalates, pesticides, and PAHs in children at important developmental life stages. To this end, three broad life stages were identified, and exposures to phthalates, pesticides, and PAHs were evaluated. Thus, this study aims to (a) determine the levels of pesticides and PAHs in donor breastmilk and identify exposures to infants, (b) quantify the levels of phthalates, pesticides, and PAHs in dust and estimate exposures in infants and children, and (c) identify the associations of socioeconomic factors, specifically, income and race on levels of phthalates, pesticides, and PAHs among children and adolescents. Each objective was explored as separate entities in this work, as addressed below.

Breastmilk was identified as the source of pesticide and PAH exposure in neonates and infants due to their restricted interactions with their surroundings. Breast milk was extracted and measured to determine the pesticide and PAH levels. Following that, probabilistic approaches were used to quantify the exposure to pesticides and PAHs. This study found that girls were more exposed than boys. In addition, pesticide and PAH exposure peaked in the first month of birth. Further, girls exposed to PAHs during the first month of life had a higher cancer risk than boys at the same age. Other life stages were also investigated to understand exposure to these substances as children grow.

The second section of this study focused on toddlers and young children, as well as their interactions and behaviors. According to studies, young children spend significant time on the floor and engage in mouthing habits. As a result, dust was chosen as the appropriate medium of exposure, and the levels of phthalates, pesticides, and PAHs were measured. Furthermore, probabilistic methods were employed to quantify children's phthalate, pesticide, and PAH exposures through dust ingestion. Girls were shown to be more exposed to these contaminants than boys, with the most significant exposure occurring during the first year of life.

Finally, the last section of this study explored social factors, particularly income and race, and their effects on the levels of phthalates, pesticides, and PAHs in children and adolescents in the US. The findings suggest that specific urinary metabolites of phthalates, PAHs, and pesticides have increased in children and adolescents. Further, there was an association between income and urinary metabolites that were increasing among children and adolescents in the US. Furthermore, increasing metabolites were more prevalent among Blacks, Hispanics, and multi/other races.

Overall, the findings indicate that life stage-specific analysis gives comprehensive information on phthalate, PAH, and pesticide exposure characteristics. Furthermore, these data show that early life exposure may contribute to an elevated risk of health effects. However, more research is needed to understand the exposure processes using a multifactorial approach. In addition, the underlying molecular mechanisms of health effects caused by phthalates, PAHs, and pesticides must be investigated.

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