Fatty acids, C8-10, octyl esters

Long-term toxicity to fish

Description of key information

Fatty acids, C8 -10, octyl esters (CAS 91031-90-0) will be mainly taken up by ingestion and digested through common metabolic pathways, providing a valuable energy source for the organism, as dietary fats. Long-term toxic effects on fish are therefore not to be expected. Based on this information and for reasons of animal welfare, long-term testing on fish is not proposed.

Additional information

There are no studies available investigating the long-term toxicity of Fatty acids, C8 -10, octyl esters (CAS 91031-98-0) to fish. However, short-term studies for all three trophic levels (fish, daphnia and algae) as well as long-term studies for daphnia and algae are available for read across substances, which adequately reflect the hazard potential of the target substance. All of these studies indicate no toxicity to aquatic organisms up to the limit of water solubility. Since the available data do not indicate that fish is more sensitive than algae and invertebrates this assessment is also considered to be true for long-term toxicity to fish.

Furthermore an chronic toxicity test on Daphnia magna available for the structurally similar substance isopropyl myristate (CAS 110-27-0) indicates no chronic toxicity of the substance.

Additionally, the aquatic concentration of the substance is expected to be very low. Since the substance is considered to be readily biodegradable and highly adsorptive (log Koc 4.1, MCI method, KOCWIN v2.00), it will be eliminated in sewage treatment plants to a high extent. In the aquatic environment, the concentration in the water phase will be reduced by biodegradation and adsorption to solid particles and to sediment.

Food ingestion is likely to be the main uptake route of Fatty acids, C8 -10, octyl esters in fish, since the substance will be adsorbed to solid particles potentially ingested by fish. In the case of ingestion, the substance is predicted to undergo metabolism. 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 Volpenheim (1972). Measured rates of enzyme catalysed hydrolysis varied between 2 and 5 µeq/min/mg enzyme for the different chain lengths. Thus the substance is expected to be hydrolysed by lipases.

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). Metabolic pathways in fish are generally similar to those in mammals. Lipids and their constituents, fatty acids, are in particularly a major organic constituent of fish and play major roles as sources of metabolic energy (Tocher 2003).

In conclusion, Fatty acids, C8 -10, octyl esters (CAS 91031-98-0) will be mainly taken up by ingestion and digested through common metabolic pathways, providing a valuable energy source for the organism, as dietary fats. Long-term toxic effects on fish are therefore not to be expected. Based on this information and for reasons of animal welfare, long-term testing on fish is not proposed.

 

References:

Berg, J.M., Tymoczko, J.L. and Stryer, L., 2002, Biochemistry, 5th edition, W.H. Freeman and Company

Mattson, F.H. and Volpenheim, R.A. (1972): Relative rates of hydrolysis by rat pancreatic lipase of esters of C2-C18 fatty acids with C1-C18 primary n-alcohols, Journal of Lipid Research, 10, 1969

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