SETAC North America 2024 -- Fish bioconcentration studies are carried out to determine whether substances have the potential to bioaccumulate or to bio-magnify throughout different trophic levels. As the requirements to conduct these studies on a broad variety of industrial chemicals, pharmaceuticals and crop protection products increase across the globe, so does the numbers of fish needed to fulfil these investigations. Prior to the revision to the OECD Test Guideline (OECD 305: 2012), the preferred method of testing required three doses of chemical (including a control) with up to 100 fish per dose. Latterly, there is now the option to test on one concentration and the control only, providing there is scientific justification. This has the potential to decrease the numbers of fish used in these tests by one third (100 fish per study). Here we present our approach to assess the selection of positive controls to be used in these assays using pyrene, the reference chemical stated in the guidelines, together with testosterone and diclofenac as both undergo Phase I hydroxylation reactions in the presence of S9 and hepatocytes, similar to pyrene.

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