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Long-term toxicity to aquatic invertebrates

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Description of key information

No toxic effects up to the limit of water solubility for Daphnia magna (OECD 211); read-across

Key value for chemical safety assessment

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No studies are available on the long-term toxicity of Reaction products resulting from the esterification of Sorbitol with C8-18 (even) and C18unsaturated fatty acids in the ratio 1:1 (EC 931-434-7) to aquatic invertebrates. The assessment was, therefore, based on studies conducted with the structurally similar category members Sorbitan octanoate (CAS No. 91844-53-0), Sorbitan stearate (CAS No. 1338-41-6) and Sorbitan, (Z)-9-octadecenoate (2:3) (CAS No. 8007-43-0). This read across approach is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. These substances are UVCBs of Sorbitan esters with partly overlapping compositions. The Sorbitan C18 saturated and unsaturated fatty acid esters present in Sorbitan laurate are main constituents of the tested substances Sorbitan stearate and Sorbitan, (Z)-9-octadecenoate (2:3), respectively. The read-across substance Sorbitan octanoate (C8-10 fatty acid ester) is used as a worst case assessment to cover the smallest constituent of Sorbitan laurate, 12C fatty acid ester. Sorbitan octanoate is expected to be more bioavailable due to high water solubility and smaller molecular size.

The key study conducted with Sorbitan stearate (CAS 1338-41-6) was performed according to OECD guideline 211 and GLP (Ministry of the Environment, Government of Japan, 2006). The test organism Daphnia magna was exposed to the test substance in a semi-static system for 21 days, at nominal concentrations of 5, 16, 50, 160 and 500 mg/L. The test concentrations 5 and 16 mg/L were prepared using tetrahydrofuran as pre-solvent. Before the test, the solvent was removed and the solution was filtered. The higher concentrations were prepared without solvent as water accommodated fractions (WAF). Since a solvent was used, the lower concentrations are not actual loading rates and these test concentrations cannot be evaluated as WAF. No inhibition of reproduction was observed during the test, in fact, the number of juveniles produced at 5 and 16 mg/L was higher than in the control. At the three higher concentrations, 100% mortality of the parental daphnia occurred, and reproduction could not be evaluated. The reported measured values for the three highest concentrations (4.65, 11.9, 17.1 mg/L) were significantly above the water solubility of the substance. Therefore, it can be assumed that undissolved test material was present and probably caused the mortality observed at the higher concentrations. Due to the methodological deficiencies in this test, the reported NOEC and EC50 need to be taken with caution. Nevertheless, at nominal concentration of 16 mg/L the test solution was reported to be clear and colourless during the test period, and no adverse effects occurred. The corresponding measured concentration 1.44 mg/L is clearly above the water solubility of Sorbitan stearate (0.01 mg/L) and was probably only attained due to the use of solvent. Therefore, 16 mg/L is used as NOELR. Sorbitan stearate is thus not expected to have adverse effects on the reproduction of daphnia magna up to the limit of water solubility.

The key study conducted with Sorbitan octanoate (CAS No. 91844-53-0) was performed according to OECD guideline 211 and GLP (Schlechtriem, 2012). The test organism Daphnia magna was exposed to the test substance in a semi-static system for 21 days, at nominal concentrations of 1.0, 3.2, 10.0, 32.0 and 100 mg/L. At the three highest concentrations, the experimental cohort completely died out. Nevertheless, no effects on reproduction were observed at the lower concentrations, and a NOEC of ≥ 10 mg/L was determined.

The key study conducted with Sorbitan, (Z)-9-octadecenoate (2:3) (CAS No. 8007-43-0) was performed according to OECD guideline 211 and GLP (Parr, 2013). The test organism Daphnia magna was exposed to the test substance in a semi-static system for 21 days, at nominal concentrations of 10, 18, 32, 56 and 100 % v/v. Since the test concentrations declined during the exposure period, the results were based on time-weighted mean concentrations. For 100 % v/v the time-weighted mean was 0.11 mg/L. Since no effects occurred at this concentration, the NOEC was determined to be ≥ 0.11 mg/L.