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Long-term toxicity to aquatic invertebrates

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Description of key information

A study according to OECD 211 for a similar read-across substance was technically not feasible due to substance characteristics.

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Additional information

Since no studies investigating the long-term toxicity to aquatic invertebrates of Fatty acids, C16-18, 2-octyldodecyl esters (CAS 96690-38-9) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to the structurally related category member 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) was conducted. The read-across substance is characterized by the same alcohol component (2-octyldodecan-1-ol) and a very similar fatty acid (C16-18 compared to C18iso (target)). This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the category 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 substances were used for the assessment. Nevertheless, as it can be seen in the data matrix of the category justification in section 13 and the overall summary, all reliable data in the category support the hazard assessment of each category member by showing a consistent pattern of results.

A statement from a laboratory is available indicating that the study with the read-across substance 2-octyldodecyl isooctadecanoate is technically not feasible due to substance characteristics (Bogers, 1998).Acute testing inDaphnia magnawas performed by exposing organisms to Water Accommodated Fractions (WAFs) (see NOTOX Project 227341 ‘Acute toxicity study inDaphnia magnawith [trade name]‘). 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 a water solubility below detection (< 0.05 mg/L) and a log Kow of > 7, it is not possible to prepare solutions that can be tested in a 21-day reproduction test withDaphnia 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.Based on the available result from one structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that the same result is expected when testing Fatty acids, C16-18, 2-octyldodecyl esters.