Food Toxicology 2(2+0)

Lesson 8 : Factors That Influence Toxicity

Species

It is appropriate to consider the kinds of differences that can exist between animals from different species. This consideration is important in toxicology because the use of animal surrogates for humans is an important toxicological strategy and is the basis for almost all toxicological predictions. A completely accurate evaluation of the toxicity of a toxicant in a particular species can only be obtained by conducting toxicological studies in the desired species. For humans, such situations seldom occur, except for accidental poisoning or industrial exposures, and for ethical reasons the deliberate exposure of humans is out of the question. Even if the ethical considerations are overlooked, animals are still required to characterize the environmental hazard of the toxicant and its probable mechanism of action. As one ascends through the different taxonomic levels, it can be assumed for comparison that the more closely related the surrogate species, the more likely it is that the test will be predictive for humans.

Mechanisms responsible for diversity include differences in metabolism, differences in renal and biliary excretion, plasma protein binding, tissue distribution, and response of target (receptor) sites. Understanding why there are differences can be important in the designing of toxicity studies to account for such differences.