ABSTRACT
In order to utilize LD50 studies to provide a meaningful comparative ranking of chemicals, it has been the practice to study one standard species, the rat. While the LD50 does provide a measure of the amount needed to kill rodents, the values
cannot be extrapolated to provide an estimate of how much of the material would kill 50% of the humans exposed to it. However, it is useful in predicting relative toxicity in humans and thus for assigning chemicals to broad classes for purposes of regulation. Pesticide labels, for example, contain signal words which reflect the relative LDso5 of the active ingredients. The words Danger-Poison designate the most toxic class; Warning indicates the pesticides of intermediate toxicity; and Caution those of lowest relative toxicity. Table 6.2 shows how these categories are defined.
