The rationale for this work is that the Economic Cooperation and Development (OECD) recently revised guideline 305 for measuring bioconcentration factors of chemicals in fish by adding a dietary bioaccumulation testing protocol . The new testing protocol is a welcome addition to bioaccumulation testing and useful in improving insights into the bioaccumulation behaviour of industrial chemicals. However, more information and knowledge is required to correctly interpret the results from such tests in terms of (i) bioaccumulation metrics, (ii) their significance to bioaccumulation in field situations, including bioaccumulation in air-breathing terrestrial organisms and relative exposure routes and (iii) potential for ecotoxicological perturbations.
The OECD 305 guideline for testing of chemicals (2012) and an accompanying draft of the OECD 305 TG guidance document (2016) present the state of the art on the interpretation of data from dietary bioaccumulation tests. These documents include much information on the derivation of certain bioaccumulation metrics from dietary bioaccumulation tests. However, they also show that there is room for substantial improvement. Required improvements include:
(i) the development of a more realistic and refined toxicokinetic model for the dietary bioaccumulation test that enables the derivation of more and more relevant information from dietary bioaccumulation test data than is currently obtained from the OECD 305 guidance document. Specifically, a revised toxicokinetic model can be applied to the results of dietary bioaccumulation tests to obtain information on (i) somatic biotransformation rates; (ii) intestinal biotransformation rates; (iii) excretion and intestinal re-absorption; (iv) growth rate; (v) the biomagnification factor (BMF) under lab and field conditions; and perhaps most importantly (vi) the bioconcentration factor (BCF) because of its importance as the predominant bioaccumulation metric recognized in regulations throughout the world.
(ii) the development of methods for deriving bioaccumulation metrics (including the depuration rate constant, growth rate constant, BMF, BCF, somatic and intestinal biotransformation rates) from the results of dietary bioaccumulation tests that follow protocols described in the most recent OECD 305 (2012) guideline.
(iii) the development and testing of methods for assessing the bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests.
(iv) investigation of the assumption that highly hydrophobic substances are associated with “adverse” perturbations on individual and populations resulting from uptake and storage of the chemical irrespective of trophic magnification.
The purpose of this research is to fill these knowledge gaps and to improve the derivation of information from dietary bioaccumulation tests and to improve the interpretation of the results of dietary bioaccumulation tests.
Objectives of the Research:
1 – Development of a toxicokinetic modelling framework for the interpretation of dietary bioaccumulation test results.
2 – Development and testing of methods for deriving bioaccumulation metrics from the results of OECD 305 dietary bioaccumulation tests.
3 – Development and testing of methods for assessing the bioaccumulation exposure pathways for aquatic and terrestrial biota from the results of dietary bioaccumulation tests and field studies.
4 – Investigate the assumption that highly hydrophobic substances are associated with “adverse” perturbations on individuals and populations resulting from uptake and storage of the chemical regardless of trophic magnification.