Bioaccumulation potential is a key parameter used in regulatory prioritization and chemicals management, e. g. in REACH. Currently, the OECD 305 fish bioconcentration test serves as the gold standard for substance-specific bioaccumulation assessment. However, this test is costly, involves maintaining relatively constant aqueous concentrations over long exposure durations and requires tissue measurements during both uptake and depuration phases which consume a large number of test organisms. For substances which have sufficient aqueous solubility, a simpler screening test would address a practical need for obtaining reliable information necessary to support decision-making in a less resource intensive manner.
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The objective of this proposal is to develop a shorter, more cost-effective bioconcentration test that uses much fewer fish. The development of such a test was recently concluded as a promising area for research based on the findings of an ILSE/HESI bioaccumulation workshop (Parkerton et al. 2008).
In support of this RfP, a training set of potential test compounds has been selected that investigators should consider in responding to this request for proposal (Table 1). These compounds were chosen to span a wide range of structural classes and physical properties (e. g. octanol-water partition coefficients) and susceptibility to bio¬transformation based on reliable aqueous BCF data that are available in the literature for either trout or carp (or both species). The bioaccumulative compounds chosen have been identified as bioaccumulative by the EU PBT Group. Most of the remaining substances in Table 1 are also being investigated in a separate research project that is focused on in-vitro methods for estimating fish biotransformation. Therefore, data from this project will complement efforts to validate in-vitro techniques that are intended to further limit animal use. The results of this research project should deliver BCF estimates using substance-specific analysis of parent compounds. It is recommended that either trout or carp be used as the fish test species.
Additional elements that should be considered in responding to this proposal are:
Advances in passive dosing techniques that can be used to improve delivery and maintenance of aqueous exposure concentrations under static test conditions (e.g. Mayer et al. 1999; Kiparissis et al. 2003; Gerofke et al 2004; Bopp et al. 2006)
Alternative experimental designs (e. g. short uptake phase and subsequent depuration phases in which fish tissue concentrations are measured at fewer time intervals, testing of multiple compounds simultaneously) that still allow steady-state BCFs to be reliably estimated
Experimental factors relevant to the test procedure (e.g. feeding) and endpoint interpretation (lipid content of fish, TOC concentration of exposure media) should be specified or determined
Short interim reports on progress are required at 3 to 6-monthly intervals. It is expected that the findings will be developed into a peer reviewed publication, following presentation at a suitable scientific conference.
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