Graduation Date

Summer 8-12-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Environmental Health, Occupational Health, and Toxicology

First Advisor

Eleanor Rogan, Ph.D.

Second Advisor

Peter Iwen, Ph.D.

Third Advisor

Shannon Bartelt-Hunt, Ph.D.

Fourth Advisor

Jesse Bell, Ph.D.

Abstract

Objectives: This research was conducted to (1) determine the concentrations of atrazine, and nitrate, in Nebraska watersheds and counties; (2) calculate the incidence of pediatric cancers and prevalence of birth defects in Nebraska counties and watersheds, respectively; (3) assess the relationship between the contaminant levels and the incidence rate of pediatric cancers and birth defects prevalence.

Methods: Pediatric cancers and birth defects data were obtained from the Nebraska Department of Health and Human Services. Water quality data were collected and retrieved from the Water Quality Portal and the Nebraska Groundwater Quality Clearinghouse. Geospatial and statistical analyses were conducted at the watershed and county levels.

Results: The age-adjusted incidence for pediatric brain and other central nervous system (CNS) cancers in Nebraska was 4.42 per 100,000 population between 1987 and 2016, which was higher than the national average of 3.16, and the difference was statistically significant (p=0.004). All the watersheds with nitrate concentrations above 10 mg/L in surface and groundwater also had pediatric CNS cancer incidence above the national average. Moreover, an association was found between atrazine concentrations > 0.0002 µg/L and nitrate concentrations > 2 mg/L and an increased incidence rate of pediatric cancers (brain and other CNS, leukemia, and lymphoma) across Nebraska counties. Furthermore, birth defect prevalence in Nebraska was 9 per 100 live births which was more than the national average of 5 per 100 live births. A positive association was observed between higher levels of nitrate in drinking water (> 6.94 mg/L) and birth defects prevalence. Similarly, watersheds with atrazine levels above 0.00 µg/L had a higher prevalence of birth defects.

Conclusions: While these findings do not indicate a causal relationship, they suggest that atrazine and nitrate may pose a risk relative to the occurrence of birth defects and pediatric cancers. They also suggest that chronic exposure to nitrate and atrazine concentrations even below the maximum contaminant levels may result in birth defects or pediatric cancers. Prospective cohort studies are recommended to support these findings so that regulations can be implemented in the form of continuous monitoring of water in private wells and improvement of agricultural practices.

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