Octyl octanoate

Short-term toxicity to aquatic invertebrates

Description of key information

No toxic effects up to the limit of water solubility for Daphnia magna (EU-guideline 92/69/EWG)

Additional information

One short-term aquatic invertebrate study is available for octyl octanoate (CAS No. 2306-88-9). Due to potential methodological deficiencies in this study, leading to an uncertainty for the interpretation of the results, the assessment was supported by a study conducted with the structurally most similar category member, isopropyl myristate (CAS No. 110-27-0) as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Further justification is given within the endpoint summary 6.1 and within the category justification Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was entered into IUCLID. Nevertheless, as can be seen in the data matrix of the category justification in Section 13, all reliable data in the category support the hazard assessment for this endpoint, by showing a consistent pattern of results.

The key study with octyl oleate (CAS No. 2306-88-9) was performed according to the Appendix of the EU-guideline 92/69/EWG (Wierich, 2000). The test organism Daphnia magna was exposed to the test substance in a static system for 48 hours, at nominal test concentrations of 1.0, 3.0, 10, 30 and 100 mg/L. Only the water phase was used for testing, after separation of undissolved test material. The LC50 was reported to be >100 mg/L (i.e. greater than the water solubility). However, oil drops were observed on the water surface and the dissolved solution was pipetted off to test vessels however this automatically leads to the assumption that all test concentrations (as was particularly the case for 10mg/L) may have been contaminated to a certain degree. Additionally the measured solubility of the test substance at the highest test concentration indicated 23.6mg/L, which is far higher than the water solubility of the substance. This again indicates that some errors or super saturation may have occurred. Although the study is considered reliable (Klimisch score 2), due the uncertainty of the method used, the results should be treated with caution for read-across purposes.

The supporting study with isopropyl myristate (CAS No. 110-27-0) was performed as a limit test according to EU Method C.2 and GLP (Stelter, 1995). The test organism Daphnia magna was exposed to the test substance in a static system for 48 hours. Three different methods were used for the preparation of test solutions: 1) direct addition to 100 mg/L, 2) direct addition to 100 mg/L with removal of undissolved test substance and 3) 3-5 times saturation without separation of undissolved material. With the first method an oil film was observed at the surface, and up to 100% immobilisation occurred. With the two other methods, no oil film and no significant effect was observed. Based on the results, the observed immobilisation is most probably due to physical effects caused by undissolved test substance. It can therefore be concluded that the test substance had no significant toxic effect on the test organism up to the limit of water solubility. An EC50 of > 0.05 mg/L was reported. 

Thus, based on theabove mentioned result, and due to the structural and profile similarities of the two substances, as are explained with in the overall endpoint summary 6.1 it can be concluded that no toxicological short-term effects on aquatic invertebrates are expected up tothe limit ofwater solubility for octyl oleate (CAS No. 2306-88-9).