Fatty acids, C8-10, octyl esters

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, read across)

Additional information

Since no study assessing the short-term toxicity of Fatty acids, C8 -10, octyl esters (CAS 91031-98-0) to aquatic invertebrates is available, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances, a read-across to the main component octyl octanoate (CAS 2306-88-9) and the structurally similar isopropyl myristate (CAS 110-27-0) was conducted. Further justification of the read-across approach is given within the endpoint summary 6.1 and the analogue justification document in section 13.

The key study with octyl oleate (CAS 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 48h-EL50 is determined 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 10 mg/L) may have been contaminated to a certain degree. Additionally the measured solubility of the test substance at the highest test concentration indicated 23.6 mg/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. Therefore, an additional study is used to support the result of the key study.

The supporting study with isopropyl myristate (CAS 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. ^Thus the 48h-EC50 is determined to be > 0.05 mg/L. 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.

Based on the above mentioned results, and due to the structural and profile similarities of the target and the source substances, it can be concluded that no toxicological short-term effects on aquatic invertebrates are expected up to the limit of water solubility for Fatty acids, C8 -10, octyl esters (CAS 91031-98-0).