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Long-term toxicity to aquatic invertebrates

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Description of key information

No effects up to the limit of water solubility.

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Since no studies investigating the long-term toxicity of 2-octyldodecyl myristate (CAS 22766-83-2) to aquatic invertebrates are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related source substances 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) and Fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) was conducted. The source substances are representative to evaluate the long-term toxicity of the target substance to aquatic invertebrates. The target substance is characterised as an ester of C18 iso branched fatty acid esterified with 2-octyldodecan-1-ol. The two source substances are structurally very similar to the target substance. 2-octyldodecyl isooctadecanoate (CAS 93803-87-3)is characterised by a longer fatty acid chain length (C18 iso branched) and by the same alcohol component (2-octyldodecan-1-ol) whereas Fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) is a UVCB substance consisting of mainly C8-C10 fatty acids esterified with C12-C18 alcohol. The substance is smaller based on its molecular weight and thus expected to exhibit a higher solubility in water and represents a worst case since bioavailability is increased. This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.
No experimental studies investigating the long-term toxicity with the source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) to aquatic invertebrates are available. A statement from a laboratory is available indicating that the study is technically not feasible due to substance characteristics (Bogers, 1998). Acute testing in Daphnia magna was performed by exposing organisms to Water Accommodated Fractions (WAFs). However, it is not common practice to use this approach in a prolonged toxicity test. The use of a column generator with the test substance coated on an inert carrier (glass beads or celite) is not possible as the test substance is a liquid. The testing in a flow-through system is also no possible alternative, since the hydrophobic character of the test substance hampers any way of mixing with the dilution water. Based on the high hydrophobicity, there is no analytical method sensitive enough to detect concentrations of the test substance in water samples. As a result, it is not possible to give any analytical support to the reproduction test with Daphnia magna. This analytical support is essential to meet the acceptability criterion for evidence that the actual concentration had been maintained within a 20% window during the total test period. Owing to the fact that the test substance is a liquid with water solubility below detection limit (< 0.05 mg/L) and a log Kow of > 7, it is not possible to prepare solutions that can be tested in a 21 d reproduction test with Daphnia magna. Further, these characteristics support the expectation that it will not be very likely that bioavailable concentrations of the test substance will ever occur in the water phase, i.e. concentrations high enough to induce any acute or chronic effects in aquatic organisms. Thus, no chronic test with aquatic invertebrates was conducted.

The study with the second source substance fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) was performed according to OECD 211 (GLP) (Salinas, 2013). Daphnia magna was exposed to a nominal loading rate of 10 mg/L (Water Accommodated Fraction). Chemical analysis of the test substance concentrations was not possible since no suitable analytical method could be developed to detect the test substance. No effects on reproduction of D. magna were observed up to the water solubility limit (< 0.05 mg/L) resulting in a NOELR (21 d) ≥ 10 mg/L.
Based on the available results from structurally related read-across substances (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterised by a similar ecotoxicological profile and comparable structure, it can be concluded that 2-octyldodecyl myristate will not exhibit long-term effects to aquatic invertebrates up to the limit of water solubility.