Sorbitan monolaurate, ethoxylated

Long-term toxicity to fish

Description of key information

The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the long-term toxicity to fish.

Additional information

There are no long-term fish studies available for Sorbitan monolaurate, ethoxylated (CAS No. 9005-64-5). However, short-term studies available for fish and algae and the long-term study with daphnia all indicate a low potential for aquatic toxicity. Additionally, based on the available results, fish is the least sensitive taxonomic group. According to the “Guidance on information requirements and chemical safety assessment Chapter R.7b: Endpoint specific guidance”, the most sensitive taxonomic group should be tested for chronic effects (ECHA, 2008). NOECs obtained from the algal growth study and daphnia reproduction study, are clearly above 1 mg/L (nominal).

Additionally, the aquatic concentrations of Sorbitan monolaurate, ethoxylated are expected to be very low. Due to its ready biodegradability and adsorption potential, it will be eliminated in sewage treatment plants to a high extent. If fractions of this chemical were to be released in the aquatic environment, the concentration in the water phase will be reduced by rapid biodegradation and potential of adsorption to solid particles and to sediment.

Furthermore, Sorbitan monolaurate, ethoxylated is expected to be metabolised by fish upon ingestion. Esters are known to hydrolyse into carboxylic acids and alcohols by esterases (Fukami and Yokoi, 2012). Carboxylesterase activity has been noted in a wide variety of tissues in invertebrates as well as in fish (Leinweber, 1987; Soldano et al, 1992; Barron et al., 1999, Wheelock et al., 2008). Therefore, it is expected that under physiological conditions, Sorbitan monolaurate, ethoxylated will hydrolyse to ethoxylated D-glucitol and the respective fatty acids. The hydrolysis of Sorbitan fatty acid esters occurs within a maximum of 48h for mono-, di- and tri-esters (Croda 1951, Mattson and Nolen 1972, Treon 1967, Wick and Joseph 1953). The resulting fatty acids are either metabolised via the β-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, 2002). D-glucitol was found to be relatively slowly absorbed from the gastro-intestinal tract of mammals, compared to glucose, and it can be metabolized by the intestinal microflora (Senti 1986). Once absorbed, D-glucitol is primarily metabolised in the liver. The first step involves oxidation by L-iditol dehydrogenase to fructose which is metabolised by the fructose metabolic pathway (Touster, 1975). D-glucitol does not enter tissues other than the liver and does not directly influence the metabolism of endogenous sorbitol in other tissues (Allison 1979). Sorbitol is naturally found in several berries and fruits as well as in seaweed and algae (FDA, 1972) and is thus assumed to be part of the natural diet of fish. In the case of Sorbitan monolaurate, ethoxylated, the sorbitol is ethoxylated. Using the OECD toolbox Vs. 2.3 for Sorbitan monolaurate, ethoxylated , the liver metabolism simulator provided 42 potential metabolites indicating that the ethoxylated part of the substance remains intact. Studies on genotoxicity (Ames test, chromosomal aberration and gene mutation in mammalian cells) were negative, indicating no reactivity of the test substance or its metabolites under the test conditions. Additionally, amounts of D-glucitol that will not be metabolised will mainly be excreted via urine, due the low molecular weight and the high water solubility of the substance. Ethoxylated units were shown to be excreted via bile, thereby the excretion linearly increases with the length of the ethoxylated unit (HERA 2009). Metabolic pathways in fish are generally similar to those in mammals. Lipids and their constituents, fatty acids, are in particular a major organic constituent of fish and play major roles as sources of metabolic energy in fish, for growth, reproduction and mobility, including migration (Tocher, 2003).

In conclusion, long-term exposure of fish to Sorbitan monolaurate, ethoxylated is expected to be very low (if any), due to efficient removal in sewage treatment plantes and ready biodegradation in natural waters. If taken up by fish, the substance will be digested through common metabolic pathways, providing a valuable energy source for the organism, as dietary fats and sugars. Additionally, chronic values for daphnia and algae, which were shown to be more sensitive, do not indicate a hazard to aquatic organisms. Long-term toxicity to fish is thus not to be expected.

 

References

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