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Long-term toxicity to fish

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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.

Key value for chemical safety assessment

Additional information

There are no long-term fish studies available for the category of Sorbitan esters. However, short-term studies are available for all three trophic levels, fish, daphnia and algae, which generally indicate a low potential for aquatic toxicity. Effects at concentrations below 100 mg/L were only observed with the smallest substances, Sorbitan, octanoate (2:3) (CAS No. 91844-53-0) and sorbitan laurate (CAS No. 1338-39-2). However, since this substance is readily biodegradable, it will be quickly removed from the environment and potential effects will be localised and of short duration. The substance is thus not classified as dangerous for the environment (Guidance on the application of CLP criteria v3.0, 2012). Moreover, effects were only observed with Daphnia and algae, and therefore, fish is considered as the least sensitive organism. 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, 2012). NOECs obtained from algal growth studies and daphnia reproduction studies are clearly above 1 mg/L (nominal) for the soluble Sorbitan, octanoate (2:3) or above the limit of water solubility for the poorly soluble category members.

Additionally, the aquatic concentrations of these substances are expected to be very low. Since the substances are readily biodegradable they will be eliminated in sewage treatment plants to a high extent. For the larger category members, high adsorption potential further promotes rapid removal from waste water. 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.

Food ingestion is likely to be the main uptake route for Sorbitan esters category members in fish, since the substance will be adsorbed to solid particles potentially ingested by fish. Also for sediment-dwelling organisms the main uptake route will be ingestion of contaminated sediment. In the case of ingestion, Sorbitan esters category members are predicted to undergo metabolism or be excreted. 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, members of the Sorbitan esters category will hydrolyse to 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-ester but decreases with the number of esterified fatty acid so that no hydrolysis of hexa-ester occurs (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 is primarily metabolised in the liver. The first step of its metabolism involves oxidation by L-iditol dehydrogenase to fructose, which is metabolised by the fructose metabolic pathway (Senti, 1986). D-glucitol is naturally found in several berries and fruits as well as in seaweed and algae (US FDA, 1972). 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 in fish for growth, reproduction and mobility, including migration (Tocher, 2003). Larger sorbitan fatty acid esters that will not be hydrolysed, such as hexaesters, are unlikely to cross biological membranes due to their high molecular weight.

In conclusion, Sorbitan esters category members will be mainly taken up by ingestion and are digested through common metabolic pathways, providing a valuable energy source for the organism, as dietary fats and fructose. Long-term toxic effects on fish are therefore not to be expected.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within CSR.