ABSTRACT
Lethality tests are designed to determine the dosages that cause death in the model species of choice. It is acute toxicity testing with death as the single end point, and no other variables are examined or other data collected. This practice of using such narrowly defined protocols has come under criticism as being wasteful of resources, from a practical point of view, and immoral, from an animal rights point of view. These issues have been extensively examined in a variety of different forums and need not be revisited here (Rowan, 1981; Zbinden and Flury-Roversi, 1981; Zbinden, 1986; Sperling, 1976). We agree that there is considerably more to defining an acute toxicity profile than determining the median lethal dosage (LD50) and that there are only uncommon situations in which solely an LD50 is needed. Even in these situations, a so-called “precise” LD50 is not warranted. There are occasions, however, when lethality data is needed for narrowly defined regulatory or labeling purposes. Substances may be legally classified as poisons on the basis of acute lethality data (Table 22). Clearly, the dosages which cause death are legitimate regulatory concerns for chemicals in commerce. In other cases, preliminary lethality data are required to plan a more extensive definitive study. Protocol designs which gather more of the extensive data necessary for profiling acute systemic toxicity are similar in design to lethality tests and are considered in detail in Chapter 9.
