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Justification for read-across

Data on the aquatic toxicity of 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) are not available. The assessment of aquatic toxicity was therefore based on studies conducted with analogue (source) substance, branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3), as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. This read across is justified, as both source and target substances are characterized by equal fatty acid moieties (3,5,5 trimethylhexanoic acid) and/or similar alcohol moieties (C9 iso alcohol with varying branching options). A detailed justification for the analogue read-across approach is provided in the technical dossier (see IUCLID Section 13).

For the source substance branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3) no aquatic toxicity was observed up to the limit of water solubility in the available studies. An acute study with freshwater fish did not cause any mortality up to the water solubility limit. Moreover, a chronic study with Daphnia magna resulted in no effects on reproduction and mobility. Toxicity testing on algae does not need to be conducted since there are mitigating factors indicating that algae toxicity is unlikely to occur, as the substance is highly insoluble in water. Significant concentrations in the water phase are thus not expected to be reached, and the substance is not expected to be bioavailable for algae. Moreover, the algae test according to OECD 201 is a static test limiting the possibility to maintain exposure concentrations of a highly insoluble and adsorbing substance at a constant level.

Furthermore, branched-nonyl 3,5,5 trimethylhexanoate did not cause inhibition of respiration in a study according to OECD 209 with activated sludge microorganisms (NOEC (3 h) ≥ 1000 mg/L). Thus, the overall potential to cause inhibition of activated sludge microorganisms is low and significant inhibition of the subsequent degradation process in sewage treatment plants is not expected.

Based on the results from the structurally related source substance ( branched-nonyl 3,5,5 trimethylhexanoate (EC 701-133-3)), it can be concluded that 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) does not pose a hazard to aquatic organisms.