ORCID ID

0009-0008-8774-3996

Graduation Date

Summer 8-9-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Medical Sciences Interdepartmental Area

First Advisor

Eleanor G Rogan, Ph.D.

Second Advisor

Cheryl L Beseler, Ph.D.

Third Advisor

Muhammad Zahid, Ph.D.

Fourth Advisor

Shannon Bartelt-Hunt, Ph.D.

MeSH Headings

"pesticide mixtures", "pediatric cancer", "birth defects", "gWQS", "pesticide index", "IPCC risk mapping", "environmental justice"

Abstract

Human exposure to environmental contaminants is associated with various pediatric health outcomes. Agrichemicals are a significant environmental risk factor for childhood cancers and congenital anomalies, and reduced exposure could improve pediatric health outcomes. Previous studies in Nebraska have explored the association between single pollutants and pediatric cancers and birth defects. However, it is important to estimate the overall effect of the agrichemical mixture on these pediatric health outcomes. In addition to environmental risk factors, several social vulnerability factors also contribute to increased agrichemical exposure and show disparities in pediatric cancers and birth defects. The objectives of this dissertation are to (i) create a pesticide and social vulnerability index of the most-applied pesticides in the contiguous US counties and identify counties with high pesticide exposure and high social vulnerability, (ii) estimate the joint association between agrichemical mixture with pediatric cancer and birth defects adjusting for neighborhood-level social vulnerability factors in Nebraska counties, and (iii) identify the Nebraska counties with high pesticide exposure and high pediatric cancer and birth defects rate.

This dissertation quantified the pediatric health outcomes associated with environmental exposures (agrichemicals) using pediatric cancer and birth defects surveillance databases. The environmental exposures in this dissertation are ascertained using the United States Geological Survey (USGS) Pesticide National Synthesis Project (PSNP) pesticide application per county measurements. We followed the environmental mixture analysis (principal component analysis and generalized weighted quantile sum regression) design to assess the joint associations and minimize the multicollinearity issues of the pesticides. We applied this strategy in these cases: 1. Pesticide and social vulnerability index, 2: pediatric cancer, 3. Birth defects. We estimated that the regression models fitted assuming a Poisson distribution and using the pediatric population as an offset term for pediatric cancer outcomes and live births as an offset term for birth defects.

In the first case, we created a pesticide index for the frequently used pesticides and a social vulnerability index using factors influencing pesticide exposure in the contiguous US counties. In the second case, we estimated the joint association between agrichemical mixtures and pediatric cancer rates and identified potential chemicals contributing to higher weights associated with pediatric cancer rates. In the third case, we also estimated the joint association between agrichemical mixtures and birth defects rate. We identified potential chemicals contributing to higher weights associated with birth defects rate. The findings from this dissertation aim to enact public health policy change, providing evidence-based results to allocate increased funding to support active-ascertainment birth defects surveillance programs, improving access to care in Nebraska counties, and supporting environmental health literacy among communities.

Our results do not imply causal or dose-response relationships due to the study design and unmeasured biases that influenced our results. Future studies using biomonitoring programs to measure the level of pesticides in humans to determine exposures and also using novel biospecimens, such as newborn dried blood spots to assess genetic and epigenetic factors, as well as early life exposures are recommended as they might increase the knowledge of these pediatric health outcomes.

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Available for download on Tuesday, July 22, 2025

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