ABSTRACT
The task of selecting the most appropriate species, strain or test system for predicting health effects in humans is not an easy one. There are a number of scientific, statutory and sociological difficulties, including scientific uncertainty, statutory inflexibility and lack of confidence in public health policy. Science has made great strides in clarifying the questions involved in extrapolating risk among species. Indeed, much of the present ferment surrounding the process of risk assessment comes from the realization that the scientific bases underlying risk assessment are open to experimental attack. The question of extrapolation is intimately involved in applying weight-of-evidence and exposure in estimating risk, where judgement and reason are applied to characterize the presence of real risk. In implementing the rational selection of species, it should be recognized that confidence in the choice is an important question of public health policy which should involve all segments of the society.
