Fatty acids, C16-18, isotridecyl esters

Toxicity to aquatic algae and cyanobacteria

Description of key information

No effects up to the limit of water solubility based on available data (OECD 201; EU Method C.3)

Additional information

Since no studies investigating the toxicity to algae of Fatty acids, C16-18, isotridecyl esters (CAS 95912-88-2) are available for this endpoint, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read across to the two structurally related category members 2-ethylhexyl oleate (CAS 26399-02-0) and dodecyl oleate (CAS 36078-10-1) was conducted.

Both read-across substances are characterized by a similar fatty acid (C18 unsatd. compared to C16-18 (target)) and an alcohol component of C8 and C12, respectively. The target substance is characterized by a C16 - C18 fatty acid and isotridecanol which is very similar to the composition of both read-across substances. The smaller alcohol chain length increases the water solubility and therefore the bioavailability in the water. Water solubility is negatively correlated with the C-chain length of the fatty alcohol and fatty acid (Lide, 2005). Therefore, it is possible to extrapolate from a category member with higher water solubility since it has an increased bioavailability in the water phase (ECHA, 2012). This read-across is justified in detail in the overall summary (IUCLID chapter 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 substance was 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.

The study with the read-across substance 2-ethylhexyl oleate was performed according to EU Method C.3 with Scenedesmus subspicatus under GLP conditions (Rieche, 1995). Two approaches were included in the study. In the first approach the insoluble particles were not removed, whereas they were separated in the second approach. No effects on the growth rate were observed at a limit concentration of 100 mg/L when separating the insoluble particles resulting in an EC50 (72 h) of > 100 mg/L (nominal). Effects on the growth rate were observed while not removing the insoluble particles. Thus, these effects are related to physical effects on growth.

The second study with the read-across substance dodecyl oleate (CAS 36078-10-1) was performed according to OECD 201 under GLP conditions (Hafner, 2012). Desmodesmus subspicatus was exposed to the loading rates of five concentrations up to 100 mg/L. Analytical measurements resulted in concentrations below the detection limit (< 0.005 mg/L). The growth of algae was not inhibited resulting in a NOELR (72 h) ≥ 100 mg/L (nominal) and an EL50 (72 h) > 100 mg/L (nominal) based on the growth rate and yield.

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 are characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that fatty acids, C16-18, isotridecyl esters will not exhibit effects on algae up to the limit of water solubility.