A Conceptual Approach to Multiple-Model Integration in Whole Site Risk Assessments

In the past, models have focused on one environmental compartment, a single organism, or specific process. All of these topics are limited in scope and often fail to take into account the more complex interactions of the real world. We have endeavored to change this practice by combining environmental transport models with an animal movement model and a physiologically based toxicokinetics (PBTK) model that has an embedded effects model. The example we will depict consists of a hypothetical contaminant plume within a lake and the impacts on the channel catfish (Ictalurus punctatus). We compared the PBTK output for the multiple-model approach to that of a single model PBTK using the maximum environmental concentration of 943 ppb as the inhaled dose. The multiple-model approach resulted in organ concentrations two orders of magnitude lower, indicating the maximum-dose approach may be overly conservative due to a simplified characterization of the study system. The greatest problems with multiple model integration are accurate data transfer and processing time. We believe we have arrived at solutions for both through the use of trilinear interpolation, compatible software, and the creation of meshing files.