Under the HMCS pre-screening scheme the potential for a substance to bioaccumulate is assessed according to its Log Pow. It is not appropriate to determine Log Pow values for surfactants with the standard OECD test methods (OECD 107 Shake Flask and OECD 117 HPLC). This is due to the intrinsic properties of surfactants (surface binding, accumulation at interfaces, emulsion formation) and their resulting inability to partition between two phases.
The HOCNF also allows the BCF for a substance to be reported. This value is determined experimentally in a full bioconcentration test utilising either fish or a bivalve mollusc (OECD 305 and ASTM E1022). Conducting these tests with surfactants is technically challenging but may be possible in many cases by applying the guidance in the following OECD documents:
- OECD series on testing and assessment No. 27: Guidance document on the use pf the harmonised system for the classification of chemicals which are hazardous for the aquatic environment
- OECD series on testing and assessment No. 23: Guidance document on aquatic toxicity testing of difficult substances and mixtures.
In the absence of any relevant scientifically robust data on a substance from the standard OECD tests described above, Cefas will apply the precautionary principle assuming the substance will bioaccumulate. However, if there is robust scientific evidence (for example from biodegradation studies, toxicokinetic studies, including metabolism, residue or monitoring studies) that indicates a substance is unlikely to bioaccumulate, Cefas will evaluate these data and apply expert judgement.