Student Research: Ed Doran

, , 2000
Faculty Advisor: Richard A. Fenske

Measuring and Modeling Dermal Absorption of Pesticide Residues


This thesis contains analyses of new statistical, computational, and optical tools that can be used to estimate the time course of dermal absorption after a pesticide residue is deposited on the skin. Chapter 1 contains a statistical model that was designed to determine how dermal residence time on the skin influences the absorbed dose. Hygienic behaviors that limit the amount of time that residues are allowed to rest on the skin (e.g., hand washing) were found to be associated with a significant reduction in the total absorbed dose. Chapter 2 determined the influence of dermal residence time on the mechanics of dermal absorption. Specifically, the analyses suggest that explicitly including the time course of dermal loading results in more representative estimates of daily absorbed dose. Chapter 3 evaluated the predictive accuracy, uncertainty, and variability of the novel dermal absorption model. Although the model underestimated the variability, it generated representative estimates of absorbed dose for the majority of workers. The data in vivo trial presented in Chapter 4 suggests that formulations and co-exposure to multiple compounds increased the variability of dermal absorption. It was also noted that occlusive contact with a contaminated surface could result in rapid uptake of pesticide residues. Chapter 5 demonstrated the ability of Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR) to detect pesticide residues on surfaces and skin. Chapter 6 documented the kinetics of dermal absorption for azinphos-methyl and captan residues during contact with a contaminated surface. The data suggest that ATR FTIR can identify dermal exposure to both pure, formulations, or mixtures of azinphos-methyl and captan. Chapters 7 analyzed the effect of formulation, simultaneous exposure, and loading on the time course of dermal absorption. The data suggests that the magnitude and pattern of dermal absorption is a function of both the compound and the components of the formulation.