Development and application of an In Vivo test for estimating biotransformation rate constants and bioconcentration factors of hydrophobic organic chemicals in fish

Bioconcentration factors (BCFs) are the most commonly used metric by regulatory agencies to assess the bioaccumulation of chemicals in fish. However, due to logistical and economic constraints to laboratory testing, there is limited empirical BCF data. In addition, there are no accepted in vivo methods to measure biotransformation rates of hydrophobic organic chemicals (HOCs) in fish. This study presents a method for measuring in vivo biotransformation rate constants and BCFs of HOCs in aqueous bioconcentration tests. BCF tests were conducted for the test chemicals; methoxychlor, pyrene, cyclohexyl salicylate and 4-n-nonylphenol using a sorbent phase as a dosing reservoir. A co-exposure using non-biotransformed reference chemicals was used to derive biotransformation rates of the test chemicals. The tests were successful for measuring depuration and biotransformation rate constants (kT, kM), and BCFs in fish that will contribute empirical data for evaluating predictive models (e.g., in vitro to in vivo extrapolation; IVIVE) and in vitro kMs.