For purposes of discussion, chemicals can be grouped into one of three categories: pesticides, drugs, or industrial chemicals. Pesticides are specifically designed to have certain toxicological characteristics and are commonly used to exterminate pesky organisms such as roaches, termites, weeds, molds, and destructive microorganisms. Drugs are also designed to demonstrate certain biological activity that can eliminate or control infectious agents and affect or regulate biological properties, among other characteristics. Because drugs and pesticides possess inherent biological activity, there are legitimate societal concerns regarding the undesirable effects arising from human or environment exposure to these chemicals. To ensure public safety, Congress passed laws (The Food, Drug, and Cosmetic Act of 1938) for controlling drugs and (The Federal Insecticide, Fungicide, and Rodenticide Act of 1972) pesticides. These laws give the Food and Drug Administration (FDA), in the case of drugs, and the Environmental Protection Agency (EPA), in the case of pesticides, both broad and specific authority

to regulate and/or control these chemicals. With the exception of items such as explosives and radiological materials, if a chemical is not a drug or pesticide it is considered an industrial chemical. This chapter will focus primarily on the role and evolution of toxicological screening as it relates to the evaluation of industrial chemicals.