5.0 Qualitative Analysis
5.1 Source/Transport
5.2 Exposure/Impact
5.2 Qualitative Sensitivity Analysis of Exposure and Impact Components
Conducting the detailed qualitative sensitivity analyses of existing models for exposure and impact components of the four scenarios is not possible at this time due to significant lack of models available for use in these processes. This lack of adequate and/or appropriate models for use in estimating exposure and impact processes clearly points out the need for a broad range of research in this area.However, a few generalizations can be made which would apply to any physiologically-based pharmacokinetic or pharmacodynamic model. Any model using physiological parameters as its foundation will be sensitive to changes in values of those parameters; thus, the essential values for parameters used in model need to be as accurate as possible. The accuracy of physiological parameters will also aid in extrapolating from one species to another, or from one physiological state to another, i.e. non-pregnant to pregnant female. At this time it is not possible to develop defensible values for many physiological parameters. For instance, it is known that blood flow into and through the liver increases during pregnancy in mammalian species; however, accurate data for liver blood flow during pregnancy is not available for most species. Exposure and impact models are also sensitive to chemical specific parameters such as absorption coefficients and partition coefficients. The imprecise absorption coefficient for a compound to bloodstream will generate inaccurate values for all calculations downstream in the model, inaccuracies which may be further amplified when extrapolating from one species to next.
