Chapter 1 – Dose and Time Determining, and Other Factors Influencing, Toxicity

Publisher Summary This chapter is intended as an introduction to the toxicity of pesticides and an evaluation of methods for their study. Toxicity is the manifestation of an interaction between molecules constituting some form of life and molecules of exogenous chemicals or physical insults. Consequences of molecular interactions or physical insults may propagate, through causality chains, all the way to the organismic level. Therefore, a more appropriate definition of the scope of toxicology would be that it is the science that elucidates the causality chain of interactions and their time course (exposure) between biological entities (subjects) of different intrinsic susceptibility and chemical and physical entities (agents) of different intrinsic potency. At least three major independent factors—compound, dosage, and duration of dosing—and a separately measurable dependent factor—storage—are involved in what is often lumped with misleading simplicity under the term “chronic toxicity.” The word “dosage” is properly applied to any rate or ratio involving a dose. The dosage-response relationship is the most fundamental single principle in toxicology. It extends to all kinds of injurious effects and implies the existence of a threshold dosage for each compound below which, under defined conditions, no harmful effect is produced. The maximal observed variation in effect associated with different factors is as follows: dosage and time-essentially infinite (health versus death) compounds.