The identification and scientific assessment of compounds that bioaccumulate in organisms and biomagnify in food webs are important aspects in the regulation of chemicals in several jurisdictions, such as Regulation (EC) No 1107/2009, the Regulation on classification, labelling and packaging of substances and mixtures, and the Regulation concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH).
Bioaccumulation also plays an important role in terms of evaluating secondary poisoning. To date, the vast majority of research on bioaccumulation has been conducted on aquatic organisms and uptake through the gills. Bioconcentration studies are commonly carried out according to the OECD Test Guideline (TG) 305. However, fish bioaccumulation studies are time consuming, expensive, and use many laboratory animals. Alternative methods that replace the use of fish for BCF testing would therefore be of value. The bioaccumulation of sediment-associated contaminants by benthic invertebrates can be assessed by using the bioaccumulation tests following technical guidance document OECD 315 (OECD, 2008). However, the test endpoint is defined as a bioaccumulation factor (BAF). A suitable method to deduce BCFs from BAFs derived from OECD 315 studies is still not available leading to a limited value of this test from the regulatory point of view. Bioconcentration data can be obtained by conducting flow-through tests with bivalve mollusks. However, an established test procedure for bioconcentration tests with freshwater bivalves is missing and would be difficult to implement regarding the selection of an appropriate test species on the basis of availability, ecological importance, past successful use, and ease of handling in the laboratory.
Hyalella azteca is an epibenthic amphipod which is widespread in North and Middle America and commonly used for ecotoxicity studies with and without sediment (Environment Canada, 2013). Several laboratory studies have been carried out with H. azteca to elucidate the bioconcentration potential of metals and organo-metals (e.g. Shuhaimi-Othman 2007; Norwood et al. 2007; Alves et al. 2009).
Investigations on the toxicokinetics and bioconcentration of organic compounds in H. azteca included compounds like chlorinated and polycyclic aromatic hydrocarbons, the insecticide DDT and the synthetic hormone 17α-ethinylestradiol (Lee et al. 2002; Landrum et al. 2004; Nuutinen et al. 2003; Lotufo et al. 2000). The water-only assays were usually carried out under static or semi-static conditions following no standardized protocol. In a recent study a range of compounds of different lipophilicity (log Kow 3.45-7.8) were tested under flow-through conditions. The results showed that bioaccumulation test with H. azteca could be an appropriate test to predict no B-vB classification (BCF < 2000) in the standard fish test (Schlechtriem et al. 2015).
The objectives of this project are:
The main objective of this project is to develop a validated test protocol for the use of H. azteca in aquatic BCF studies. For this, the following specific objectives will be addressed:
- To collate existing information as well as develop new data to compare biotransformation of xenobiotics in azteca and fish.
- To assess the usefulness of experimental elimination rate constants as test parameters that we can combine with our mechanistic knowledge on partition and transport processes in aquatic and terrestrial organisms in order to derive BCF and BMF values needed for chemical regulation
- To prepare a detailed test protocol for use of azteca in aquatic BCF studies for the ring-test.
- To have regular dialogue with regulatory agencies, such as UBA and ECHA, over the acceptability of azteca as an alternative, non-vertebrate test species for bioaccumulation assessment.
- To organise an inter -laboratory comparison (‘ring -test’) with known test compounds to validate the test protocol (at least six partners).