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Toxicity to terrestrial arthropods

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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 toxicity to terrestrial arthropods. 

Key value for chemical safety assessment

Additional information

In accordance with Regulation (EC) No. 1907/2006, Annex X, Column 2, 9.4 further studies on the effects on terrestrial organisms do not have to be conducted since the chemical safety assessment indicates that there is no need. No experimental data on toxicity to terrestrial arthropods are available for the Sorbitan esters. Based on calculated estimation, larger Sorbitan esters (all triesters, diesters from fatty acid chain length C12 and monoesters with C18 fatty acids) show high adsorption potential (log Koc 3.3 - >10). Smaller Sorbitan mono- and diesters (fatty acid chain length <C18 and <C12, respectively) have lower calculated adsorption potential (log Koc 1.0 - 2.8). However, all Sorbitan esters have surface active properties, which is not taken into account by the model calculation, and further increases the adsorption potential of the substances. Therefore, tests with soil-dwelling organisms that feed on soil particles are most relevant for these substances.

The terrestrial toxicity of Sorbitan esters has been tested on the earthworm Eisenia fetida with the test substances Sorbitan, octanoate (2:3) (CAS No. 91844-53-0) and Anhydro-D-glucitol trioleate (CAS No. 26266-58-0). No mortality was observed during the 14-day exposure period at the test concentration of 1000 mg/kg dw. With these two test substances, low terrestrial toxicity was demonstrated in both ends of the category, and interpolation of the results is possible for other category members. Therefore, there is no reason to expect effects for other category members. Testing the toxicity on earthworm evaluates the exposure to the test substance via soil pore water, surface contact as well as by ingestion of soil particles. This is of particular importance as one should focus on the pathway of exposure (ECHA, 2012). As such one can thus assume that earthworms would be highly exposed to toxicants in soil and hence are sensitive to the potential adverse effects of the substance.

Based on the available data, the terrestrial toxicity of Sorbitan esters is very low. Also, no effects on reproduction were observed in the chronic aquatic studies with Daphnia magna. Additionally, the substances are not expected to remain in the terrestrial environment, due to ready biodegradation. Bioaccumulation is not likely due to rapid metabolism. 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). 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.

Based on this information, toxicity to terrestrial arthropods is not expected to be of concern, and consequently, no further testing is required.


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