A model for estimating the potential biomagnification of chemicals in a generic food web:: Preliminary development

Goal, Scope and Background. Bioaccumulation and biomagnification of organic pollutants have been increasingly assessed and modeled during the last years. Due to the complexity of these processes and the large variability of food webs, setting generic assessments for these parameters is really difficult. Equilibrium models, based on a compound's lipophylicity, are the main tool in regulatory proposals, such as for identifying Persistent, Bioaccumulative and Toxic Substances (PBTs), although a refinement has been claimed by the scientific community. Toxicokinetic studies offer an alternative for these estimations, where biomagnification is modeled as a succession of bioaccumulation processes, each one regulated by toxicokinetic parameters. Methods. A review of kinetic models covering species belonging to different trophic levels and with different ecological behavior has been conducted. The results were employed for setting a conceptual model for estimating the biomagnification potential in a generic food web, which was mathematically implemented through system dynamic models developed under data sheet software. Crystal Ball was then employed for allowing Monte Carlo based probabilistic calculations. Bioaccumulation laboratory assays have been performed to estimate toxicokinetic parameters in mussels (Mytilus edulis) with two PAHs (chrysene and benzo[a]pyrene). The contamination was delivered via food. The exposure period lasted more than one month followed then by a deputation phase. The contaminant content was determined on an individual basis on five replicates. Results and Discussion. The reviewed information suggested the development of a tiered conceptual biomagnification model, starting with a simplified food chain which can be refined to more realistic and complex models in successive levels. Conclusions. The mathematical implementation of the conceptual model offers tools for estimating the potential for bioaccumulation and biornagnification of chemicals under very different conditions. The versatility of the model can be used for both comparative estimations and for validating the model. Recommendations and Perspectives. Since bioaccumulation and biornagnification processes are crucial elements for a proper risk assessment of chemicals, their estimation by mathematical models has been widely tested. However, in regulatory assessments, too simplistic models are still being used quite often. The biornagnification model presented in this study should be a more accurate alternative to these models. In comparison to other previously published biornagnification models, the present one covers the time variation of bioaccumulation using just a few toxicokinetic parameters.