Chapter 41 - The Influence of Age on Pesticide Toxicity

Abstract

This chapter discusses the factors that cause age-related differences in pesticide toxicity. Age-related differences in sensitivity to pesticides can occur for a wide variety of reasons. Toxicokinetic differences among different age groups can contribute to differential sensitivity, with differences in biotransformation often being a major factor. In other instances, toxicodynamic differences may exist that lead to age-related differences in sensitivity. Moreover, the relative contributions of toxicokinetic and toxicodynamic factors in age-related sensitivity may differ markedly among the various classes of pesticides, and even among members of the same class of toxicants. Exposures to pesticides are often age-related, based on age-specific behaviors, diets, or other factors. Thus, the nature of age-related differences in sensitivity to pesticides is complex, and broad-based generalities are typically unjustified. Differences in rates or extent of absorption can contribute to differential sensitivity among age groups. Once absorbed, differences in tissue distribution or rates of elimination between age groups can contribute to differential sensitivity. Older animals (and people) typically have a higher fat content than younger individuals, which can have an important effect on distribution, accumulation, and storage of highly lipophilic pesticides. Changes in biotransformation during maturation and aging can often contribute to age-related differences in sensitivity. Immature and very old animals generally have lower biotransformation capacities.