Chapter 32 - The Influence of Age on Pesticide Toxicity

Abstract

This chapter is devoted to understanding the differential sensitivity of the nervous system based on the developmental stage of exposure. Age-related differences in sensitivity to pesticides can be attributed to both toxicokinetic and toxicodynamic principles. It is clear from review of both experimental and clinical data that there is no hard-and-fast rule regarding age-related differences in sensitivity to pesticides. While neonates may be more sensitive to the acute toxicity of some pesticides, adults may be more sensitive to others. Even when a single pesticide is considered, age-related differences in sensitivity may change qualitatively depending on the conditions of exposure or the endpoint measured. While maturational differences in biotransformation capacity may be limiting in some cases, e.g., with acute, high-level exposures where detoxification enzymes could become saturated, such metabolic differences may be of lesser importance with repeated, lower levels of exposure to the same pesticides. Similarly, differences in the ability to recover following pesticide exposure may be much more important when repeated exposures occur than following acute exposures. Relative sensitivity can be expressed in one of two ways, i.e., a subpopulation exhibits differences in sensitivity to a particular form of toxicity or a subpopulation exhibits qualitatively different forms of toxicity to the same pesticide. Risk assessments are typically performed using a “critical” endpoint, generally the most sensitive endpoint to the toxicant in question derived from a series of toxicity studies.