Abstract
The toxic potential of a chemical is largely dependent on the nature of enzymes present in the living organism at the time of exposure. If these favor activation, high levels of reactive intermediates will be generated, largely in the liver, overwhelming the deactivation mechanisms and provoking toxicity Reactive intermediates may also be transported to other tissues, distant to the site of their formation, to manifest toxicity/carcinogenicity. The levels of these enzyme systems in animals and humans are genetically determined but are also modulated by exposure to environmental chemicals, many of which are derived from the diet. It is now possible, using sophisticated computer-assisted techniques, to predict whether a chemical is likely to form a reactive intermediate, thus enabling the safety evaluation of chemicals at the earliest stage of development, before chemical synthesis is undertaken (Ioannides et al., 1993). © 1997 Elsevier B.V. All rights reserved.