A Critique of the Use of Distribution-Based Extrapolation Models in Ecotoxicology

A fundamental unanswered question in ecotoxicology concerns the extent to which ecosystem-level effects of pollutants can be understood or predicted from tests at lower levels of organization (Forbes Van Leeuwen et al. 1992). All these presume an underlying interspecific distribution of sensitivities to a toxicant. We suggest that the rational use of these models as ecotoxicological tools for environmental regulation requires additional basic knowledge in two areas. The first concerns the relationship between structure and function in ecosystems. The second involves the nature of the statistical distribution of toxicity end-points in natural assemblages of species. Because of deficiencies in basic knowledge in these areas, statistical extrapolation does not presently offer an improvement over much simpler arbitrary assessment factors. We conclude that the added complexity inherent in their use is not outweighed by the benefits obtained.