Document Type


Date of Degree

Spring 2018

Degree Name

PhD (Doctor of Philosophy)

Degree In

Human Toxicology

First Advisor

Rohlman, Diane

First Committee Member

Wang, Kai

Second Committee Member

Doorn, Jonathan

Third Committee Member

Robertson, Larry

Fourth Committee Member

Ludewig, Gabriele

Fifth Committee Member

Olson, James


Organophosphates (OPs) and Pyrethroids (PYRs) are widely used pesticides in both agricultural and non-agricultural environments. In agricultural work settings, typically more than one pesticide is used in combination, or sequentially, to kill pests. There is currently a gap in research that looks at how exposures to multiple pesticides can impact human health – particularly among adolescents who work in these environments. The goal of this dissertation research was to examine the use of OP (chlorpyrifos, and profenofos) and PYR (λ-Cyhalothrin, α-Cypermethrin) pesticides across an application season and how exposure is associated with symptoms and cholinesterase enzyme activity, and to examine the impact of a sequential exposure to multiple OPs, and exposure to both OPs and PYRs. Urine and blood samples, questionnaire data, and a medical exam were collected over a 10-month period from adolescent pesticide applicators in Egypt. Overall, applicators had higher exposure than non-applicators to all four pesticides. The non-applicators were also exposed and had levels 4 times higher in urine metabolite levels than the general population in the U.S. In addition, these exposures caused increased symptoms and severity of symptoms among both applicators and non-applicators. In conclusion, adolescent agriculture workers in the Egyptian cotton fields are exposed to multiple pesticides and are susceptible to the impact of those exposures on their health.


Adolesecents, Agriculture, Biomarkers, Cholinesterase, Occupational Exposure, Pesticides


xx, 161 pages


Includes bibliographical references (pages 140-161).


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Copyright © 2018 Barbara C. Okeke

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