Isooctadecyl isooctadecanoate

Long-term toxicity to aquatic invertebrates

Description of key information

No effects up to the limit of water solubility (OECD 211).

Additional information

Since no studies investigating the long-term toxicity to aquatic invertebrates of isooctadecyl isooctadecanoate (CAS 41669-30-1) 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 (Z)-octadec-9-enyl oleate (CAS 3687-45-4) was conducted. The source substance 2-octyldodecyl isooctadecanoate is characterized by the same fatty acid chain length (isooctadecanoic acid) and a similar branched alcohol component (2-octyldodecanol compared to isohexadecanol/isooctadecanol for the target substance). (Z)-octadec-9-enyl oleate is characterized by a similar fatty acid chain length (oleic acid compared to isooctadecanoic acid) and a similar alcohol component (oleyl alcohol compared to isooctadecanol). This read-across is justified in detail in the overall summary (IUCLID Section 6.1) and within the analogue justification in IUCLID Section 13.

A statement from a laboratory is available indicating that the study with the source substance 2-octyldodecyl isooctadecanoate 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) (see NOTOX Project 227341 ‘Acute toxicity study in Daphnia magna with [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 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. This is further confirmed in one GLP Guideline study according to OECD 211 performed with the source substance (Z)-octadec-9-enyl oleate (CAS 3687-45-4). The study was performed with the water flea Daphnia magna under semi-static conditions. Due to the very low water solubility (< 0.05 mg/L) a limit test with a Water Accommodated Fraction (WAF) of nominal 100 mg/L was performed. No effects on reproduction and mortality were recorded after 21 d resulting in a NOELR (21 d) of ≥ 100 mg/L. 0% mortality was recorded in the control whereas 5% mortality was observed in the treatment. This mortality is regarded as natural and tolerated by the test guideline. The chemical analysis resulted in concentrations below the analytical detection limit of 0.0423 mg/L reflecting the very low water solubility of the test item. Based on the result it can be concluded that (Z)-octadec-9-enyl oleate will not exhibit chronic effects on aquatic invertebrates up to the limit of water solubility.

Based on the available result from two structurally related read-across substances (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 isooctadecyl isooctadecanoate.