Physiologically Based Toxicokinetic (PBTK) Modeling in Ecotoxicology

Physiologically based toxicokinetic [(PBTK), or alternatively referred to as physiologically based pharmacokinetic (PBPK)] models are quantitative descriptions of absorption, distribution, metabolism, and excretion of chemicals in biota. PBTK models are increasingly being used as an effective tool for designing toxicology experiments and for conducting extrapolations essential for risk assessments. This chapter describes the basic concepts, equations, parameters, and software essential for developing PBTK models. QSAR methods for estimating input parameters as well as data sources containing relevant parameters for model development in rats, mice, cattle, birds, and fish are summarized. Model templates for creating PBTK models in fish and terrestrial species are presented. Several examples of model simulations are presented along with a brief discussion of how PBTK models can be applied to make significant advances in ecotoxicology and ecotoxicological risk assessments.