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Toxicity to aquatic algae and cyanobacteria

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Description of key information

According to Regulation (EC) No. 1907/2006, Annex VII, 9.1.2, toxicity testing on algae species does not need to be conducted.

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Additional information

According to Regulation (EC) No. 1907/2006, Annex VII, 9.1.2, toxicity testing on algae species does not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur, for instance if the substance is highly insoluble in water or if the substance is unlikely to cross biological membranes. Fatty acids, C18 unsaturated, trimers, 2-ethylhexyl esters (CAS No. 173832-46-7) is poorly soluble in water (water solubility < 1 mg/L). Significant concentrations in the water phase are thus not expected to be reached, and the substance is not expected to be bioavailable for algae. Additionally, since the algal test (OECD 201) is a static test, the low water solubility and high adsorption potential (log Kow > 10) may critically hinder the technical feasibility of the study. Highly hydrophobic and adsorptive substances tend to adsorb to the walls of the test vessels and to the surface of algae cells, often causing effects on biomass and growth by direct physical interaction with the algae (e.g. hindering the access to light and nutrients, whereas dissolved concentrations in the test medium are actually close to zero (OECD Guidance document No. 23, OECD, 2000)). Furthermore, the high molecular molecular weight (973.62 to 11184 g/mol) and log Kow value > 10 are factors that significantly hinder the capacity of a moleculate to cross biological membranes (Guidance on information requirements and chemical safety assessment, Chapter R.11 (ECHA, 2012)).

Based on the technical difficulties associated to the performance of an algae study with Fatty acids, C18 unsaturated, trimers, 2-ethylhexyl esters, its low solubility in water and the low potential to cross biological membranes, algae testing for this substance is not deemed necessary.

References

European Chemicals Agency (ECHA, 2012). Guidance on information requirements and chemical safety assessment, Chapter R11: PBT Assessment

 

Organisation for Economic Co-operation and Development (2000). Guidance document on aquatic toxicity testing of difficult substances and mixtures. Environmental Health and Safety Publications, Series on Testing and Assessment No. 23., Paris, France.