Background
When addressing the safety of chemicals, exposure of organisms, including man, via the food-chain is a key part of the assessment. This assessment is a tiered process and starts with the measurement of a chemical's bioaccumulation potential using the fish bioconcentration factor (BCF) test (e.g. OECD 305) and an assessment of potential toxicity derived from a previously conducted test on a mammalian or avian species. Using the output from a BCF test, transfer up the food-chain is modelled and those modelled concentrations are compared to an extrapolated no effect concentration derived from the toxicity test. It has become a standard part of such assessments to assume that chemicals with BCFs of over 2000 are of particular concern and require special treatment. The standard tests conducted in the laboratory to address uptake by aquatic organisms are based on relatively simple protocols which are not designed to replicate environmental conditions. Amongst those factors that make extrapolation of laboratory derived data to field conditions difficult, are the presence of dissolved and particulate organic matter, temperature, animal growth and species differences. The object of this project is to investigate how the physical-chemical parameters in a laboratory test impact the test data and their extrapolation to field behaviour of chemicals. The project should also include relevant, well designed studies to test the predictions of field bioaccumulation and biomagnification
Scope
- Based on existing literature reviews identify the key properties and parameters impacting BCF measurements and field BAF assessments. Review the literature for substances produced in high tonnages to identify those that have laboratory data indicating a BCF > 2000 (the focus on such substances is because these often have a high exposure potential to the environment).
- Design relevant laboratory and ”field” studies that test predictions, based on laboratory studies, of how chemicals will behave and test the current working hypothesis that substances with BCFs > 5000 exhibit food web magnification while BCFs < 5000 exhibit equilibrium partitioning or trophic dilution. Chemicals tested should include highly hydrophobic chemicals and metabolisable chemicals. It is not expected that new regulatory tests (OECD 305) will be conducted.
- Use these test designs as input to a 2008 SETAC Workshop addressing the evaluation of laboratory and field data and refine the proposed studies.
- Conduct the studies and report the data comparing field bioaccumulation potential to lab bioaccumulation potential to assess validity of lab-field extrapolation. Address issues including how many chemicals should be assessed and the type of groups of such chemicals.
It is expected that the findings will developed into a peer reviewed publication, following presentation at a suitable scientific conference. Short interim reports on progress are required at 3 to 6-monthly intervals.
