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Studies investigating the terrestrial toxicity of Fatty acids, C8 -10, octyl esters (CAS 91031-90-0) are not available. Therefore, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 Grouping of substances, read-across to the structurally similar substances isopropyl myristate (CAS 110-27-0) and Fatty acids, C16-18 and C18-unsaturated, 2-ethylhexyl esters (CAS 85049-37-2) was conducted.

The target and source substance are monoesters of primary and secondary alcohols and linear C8 –C17 fatty acids. The target substance fatty acids, C8 -10, octyl esters is an UVCB substance comprising linear C8-10 fatty acids esterified with octanol. The two source substances isopropyl myristate (CAS 110-27-0) and Fatty acids, C16-18 and C18-unsatd., 2-ethylhexyl esters (CAS 85049-37-2) are linear saturated and unsatured fatty acids with a chain length of C14 - C18. The fatty acid chains are esterified with a primary alcohol. The target and source substances are characterised by similar physico-chemical properties. All substances are readily biodegradable, poorly soluble in water (WS <0.05 mg/L) and are not volatile (VP <0.1 Pa). The log Kow of target and source substances is generally high (>6.5) and increases with fatty acid chain length. The similarities in the physico-chemical properties indicate that soil is the main target compartment for target and and source substances. The available results on the aquatic toxicity of the source substances are furthermore indicative for a similar toxicilogial profile. For a detailed review of the data matrix please refer to the analogue justification attached in section 13 in IUCLID.

Due to their low solubility and high adsorption potential, Fatty acids, C8-10, octyl esters isexpected to mostly sorb to soil natural organic matter, in terrestrial systems. Concentrations in soil pore water are expected to be low, also due to ready biodegradation. The substance will therefore be relevant for uptake mainly for soil dwelling organisms feeding on soil organic matter, such as earthworms.

The assessment of the toxicity to terrestrial macroorganisms is based on data available for the source substance isopropyl myristate (CAS 110-27-0). The toxicity of isopropyl myristate to Eisenia fetida was tested in a study following OECD 207. No mortality was observed during the 14-day exposure period at the test concentration of 20,000 mg/kg. Additionally, data is also available for the toxicity of the source substance Fatty acids, C16-18 and C18-unsaturated, 2-ethylhexyl esters (CAS 85049-37-2) to terrestrial plants. The 21-day NOEC value is determined to be 100 mg/kg for all plants tested, and EC50 values between 390 and 600 mg/kg are reported.

Based on the available data, the terrestrial toxicity of the source substances is indicated to be very low. Since both the source substances and the target substance are poorly soluble in water, have high adsorption potential and a high log Kow, their behaviour in the terrestrial compartment is expected to be similar. The available earthworm study can therefore be used as part of a read-across approach for Fatty acids, C8-10, octyl esters.

Furthermore, Fatty acids, C8-10, octyl estersis expected to be metabolised by organisms after ingestion, which is considered to be the main uptake route. Esters of primary alcohols, containing from 1 to 18 carbon atoms, with fatty acids, containing from 2 to 18 carbon atoms, have shown to be hydrolysed by pancreatic lipases in a study by Mattson and Volpenhein (Mattson and Volpenhein 1972). Measured rates of enzyme catalysed hydrolysis varied between 2 and 5 µeq/min/mg enzyme for the different chain lengths. The resulting free fatty acids and alcohols are absorbed from the intestine into the blood stream. The alcohols are metabolised primarily in the liver through a series of oxidative steps, finally yielding carbon dioxide (Berg et al. 2002). Fatty acids are either metabolised via the beta-oxidation pathway in order to generate energy for the cell or reconstituted into glyceride esters and stored in the fat depots in the body (Berg et al. 2002).

Based on the available information, toxicity of Fatty acids, C8-10, octyl esters (CAS 91031-98-0) to terrestrial organisms is not expected to be of concern, and consequently, no further testing is proposed.

 

References:

Berg JM, Tymoczko JL, Stryer L. 2002. Biochemistry, 5thedition, W.H. Freeman and Company

Mattson FH, Volpenhein RA. 1969. Relative rates of hydrolysis by rat pancreatic lipase of esters of C2-C18 fatty acids with C1-C18 primary n-alcohols, J Lipid Res 10: 271-276

Tocher DR. 2003. Metabolism and functions of lipids and fatty acids in teleost fish.Rev Fisheries Sci 11(2): 107-184