An evaluation of toxicity extrapolation methods used to develop toxicity reference values for ecological risk assessments

The objective of this thesis was to review and comment on the various methods available for the extrapolation of laboratory toxicity data and to determine which extrapolation method (for a select number of species and chemicals) most accurately represents available wildlife toxicity data. To do this, wildlife and laboratory toxicity data were complied for one organic and two inorganic chemicals (i.e., methylmercury, selenium and cadmium). Toxicity reference values (TRVs) for each of these chemicals were derived for a variety of species using species-specific toxicity data (i.e., data from toxicity studies conducted on the wildlife species of interest). TRVs were also derived for a variety of wildlife species using non-species-specific laboratory data (e.g., toxicity data on laboratory rodents) and by applying either the uncertainty factor or allometric scaling approach to extrapolate toxicity data from one species to another. The species-specific TRVs were then compared to the laboratory-derived wildlife TRVs to observe how well the wildlife TRVs were predicted by the toxicity extrapolation methods. (Abstract shortened by UMI.)...