User Guide to Thresholds and Classification - Environmental ...

373User Guide for Thresholds and ClassificationsAppendix 19F: Globally Harmonized System of Classificationand Labelling of Chemicals – guidance on the bioconcentrationfactor19F.1 IntroductionThis appendix is largely the same as the Globally Harmonized System of Classification and Labelling ofChemicals, Annex 9.(United Nations, 2007) Section 19F.2 reflects Appendix III and section 19F.3 reflectsAppendix IV of Annex 9.19F.2 Basic principles of the experimental and estimation methods fordetermination of bioconcentration factor and n-octanol-water partitioncoefficient of organic substancesBioconcentration factorDefinitionThe bioconcentration factor (BCF) is defined as the ratio between the concentration of the chemical in biotaand the concentration in the surrounding medium, here water, at steady state. The BCF can be measuredexperimentally directly under steady-state conditions or calculated by the ratio of the first-order uptake andelimination rate constants, a method that does not require equilibrium conditions.Appropriate methods for experimental determination of bioconcentration factorDifferent test guidelines for the experimental determination of bioconcentration in fish have beendocumented and adopted; the most generally applied being the Organisation for Economic Cooperation andDevelopment (OECD) test guideline (OECD 305, 1996) and the ASTM standard guide (ASTM E 1022-94)(see Appendix 19A for sources of these guidelines). OECD 305 (1996) was revised and replaced theprevious version OECD 305A-E, (1981). Although flow-through test regimes are preferred (OECD 305,1996), semistatic regimes are allowed (ASTM E 1022-94), provided that the validity criteria on mortality andmaintenance of test conditions are fulfilled. For lipophilic substances (log KOW > 3, where KOW means then-octanol-water partition coefficient), flow-through methods are preferred.The principles of the OECD 305 and the ASTM guidelines are similar, but the experimental conditionsdescribed are different, especially concerning:the method of test water supply (static, semi-static or flow through);the requirement for carrying out a depuration study;the mathematical method for calculating BCF;sampling frequency: number of measurements in water and number of samples of fish;requirement for measuring the lipid content of the fish; andthe minimum duration of the uptake phase.January 2012 EPA0109