How meaningful is the bioconcentration factor for risk assessment?

Although bioconcentration factors (BCFs) of a chemical may vary considerably due to different species, laboratories, lipid content, and test conditions it is generally agreed that high BCFs are cause for concern whereas low BCFs signalise no risk. Results of bioaccumulation studies with phenol and two other chemicals are compared demonstrating that low BCFs may be obtained by testing with high concentrations and vice versa, the differences covering 2 – 3 orders of magnitude. However, when compared on the basis of body burden concentrations, differences are in the same order. Since the BCF directly influences classification, labelling of dangerous substances and environmental risk assessment, low BCFs due to high test concentrations may be misleading and underestimating the risk. Hence the consideration of the complexity of bioaccumulation processes including investigations on metabolism, organ-specific bioconcentration and bound residues, and relating these data to critical body burden concentrations for the respective ecotoxicological end point will be a better approach for risk assessment than consideration of the BCF alone.