B-compass Rat

Bioaccumulation assessment initially focused on aquatic organisms. However, over the past few years, consensus has emerged that bioaccumulation assessment will also have to be extended to air-breathing species because aquatic bioaccumulation cannot represent terrestrial bioaccumulation. This is due to the fact that uptake mainly occurs via food in terrestrial organisms and there is no such efficient clearance with water via ventilation/urination as compared to aquatic organisms. A suitable regulatory endpoint for assessing terrestrial bioaccumulation could be the so-called biomagnification factor (BMF) which corresponds to the steady-state fugacity ratio between an organism and its diet. To reduce the need for animal testing, the application of predictive models as screening tools or lower tier assessments for evaluation of a chemical’s biomagnification potential is desirable.

With B-compass rat we offer a calculation tool that is conceptually analogue to B-compass fish. B-compass rat allows prediction of biomagnification factors under consideration of in vitro biotransformation data from assays with cells, S9 fraction or microsomes. The in vitro biotransformation data is extrapolated to the corresponding in vivo rates (in vitro-in vivo extrapolation) and then used in the BMF prediction model. B-compass rat allows not only hepatic biotransformation to be considered but also extrahepatic biotransformation in lung, gastro-intestinal tract (GIT) or kidney can be represented. The partition information needed in B-compass rat are the octanol-water and the octanol-air partition coefficient of the chemical. An alternative approach that derives the needed partition data from poly-parameter free energy relationships is also feasible and could be implemented in future if demanded. Again, two models of different complexity are implemented in the calculation tool: a simple model and a more complex model. The more complex model considers blood flow limitation as well as the potential first-pass effect in GIT/liver. The results of both models are provided simultaneously without any additional efforts for the user and allow for direct comparison.

Please cite as
Krause, S. and K.-U. Goss, B-compass Rat_Kow Version 1.0, Leipzig, Germany, Helmholtz Centre for Environmental Research, 2022