A generic BAF model for fish.

BAF-QSAR v1.1 provides estimates of the bioaccumulation factor (BAF) for generic fish species in lower, middle and upper trophic levels of aquatic food webs. The BAF predictions are considered generic in that they are not considered to be for a particular species of fish. The model is essentially a quantitative structure-activity relationship (QSAR) requiring only the octanol-water partition coefficient (KOW) of the chemical and the metabolic transformation rate constant (if available) as input parameters. BAF-QSAR v1.1 is derived from the parameterization and calibration of a mechanistic bioaccumulation model to a large database of evaluated empirical BAFs from Canadian waters. The empirical BAFs are for chemicals that are poorly metabolized and are grouped into lower, middle and upper trophic levels of fish species. The model is calibrated to each trophic level of measured BAF values thus providing estimates that are in agreement with empirical BAFs. The model predictions can include the effect of metabolic transformation and trophic dilution on the BAF if a reliable estimate of the chemicals metabolic transformation rate in fish is available. The BAF-QSAR reflects the current understanding for the mechanisms of bioaccumulation in aquatic organisms including chemical uptake from the water and the diet and chemical elimination from the gills, feces, growth and metabolic transformation (BAF-QSAR 1.0; Arnot and Gobas 2003). The model is coded in a Microsoft EXCEL workbook and is freely available for download. The model can be run for a large number of chemicals.

Intended Uses

The model is intended to estimate the bioaccumulation factor (BAF) of non-ionic organic chemicals in three general trophic levels of fish (i.e., lower, middle and upper). Thus it provides generic estimates in absence of site-specific measurements or estimates. The model can be used to predict dietary concentrations for higher trophic level predators (e.g., birds and mammals) including human exposure concentrations from fish in their diet. The model has been used to categorize chemicals for their potential to bioaccumulate in aquatic food webs. The BAF-QSAR can also be used in the derivation of water quality guidelines and total maximum daily loadings by relating internal concentrations of organic chemicals in upper trophic fish species to corresponding concentrations in the water.