Dehydrated sorbitol, C18 (unsaturated) fatty acid esters, ethoxylated

Long-term toxicity to aquatic invertebrates

Description of key information

NOELR (21 d): 10 mg/L based on reproduction of Daphnia magna (OECD 211)

Additional information

Since no experimental studies investigating the long-term toxicity ofsorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated)(CAS 9005-65-6) to aquatic invertebrates are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read-across to the structurally related substance sorbitan monolaurate, ethoxylated (1-6.5 moles ethoxylated) (CAS 9005-64-5) was conducted. Both substances are considered to be similar based on their chemical structure. The target substance is characterized as a monoester of sorbitan and a C18 unsatd. fatty acid (degree of ethoxylation: 3 and 5) whereas the source substance consists of sorbitan monoesterified with C12 and C14 fatty acids (degree of ethoxylation: 1 - 6.5). The smaller fatty acid chain length of the source substance should increase the water solubility and therefore the bioavailability in the water phase. The water solubility is negatively correlated with the C-chain length of the fatty acid (Lide, 2005). Therefore, it is possible to extrapolate from a source substance with a higher water solubility since it has an increased bioavailability in the water phase (ECHA, 2012). Sorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated)is expected to be poorly soluble in water. Two studies according to OECD 105 (flask method) (Frischmann, 2014a & 2014b) resulted in a water solubility of > 500 g/L (at 20 °C, pH 8.29 - 9.39). However, the water solubility was estimated by visual inspection only with the result of increasing viscosity of solution while adding test substance to the water. Due to the fact, that the formation of the gel is a continuous process, no discrete point could be identified at which dissolution in water switches to gelling. For poorly soluble surface active substances a CMC measurement can help to define a limit value for water solubility taking into account the concentration of substance in solution, when micelles begin to form. The CMC of two batches of the test substance was difficult to achieve as the samples were poorly water soluble (Humphrey, 2014). Therefore, only approximate CMC curves and values could be obtained (approx. 100 mg/L (literature value 33.7 mg/L). The lower water solubility value and the difficulties during measurement of the CMC give clear evidence that the substance is poorly water soluble. This is supported by the structurally similar substance sorbitan monolaurate, ethoxylated (1 - 6.5 EO) (CAS 9005-64-5) which has a water solubility value of < 0.2 mg/L (20 °C, pH = 6.3 - 7.9, EU method A.6). Finally a water solubility value of approx. 100 mg/L is taken for assessment. This read-across is justified in detail in the overall summary (IUCLID section 6.1) and within the analogue justification in IUCLID Section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

The available study with the source substance sorbitan monolaurate, ethoxylated (1-6.5 moles ethoxylated) was conducted according to OECD 211 (GLP) with the water flea Daphnia magna (Schlechtriem, 2012). The test organism Daphnia magna was exposed to the test substance under semi-static conditions, at nominal test concentrations of 1.0, 3.2, 10.0, 32.0 and 100 mg/L during 21 days. The test solutions were prepared as water accommodated fractions (WAF). At 32 mg/L, a significant effect on reproduction was observed. Also the body length of parent animals was affected by the treatment at this concentration, and 60% parental mortality occurred. At 100 mg/L, 100% mortality of the parent animals was observed. Therefore, reproduction could not be evaluated for this concentration. The NOELR (21 d) for reproduction was thus determined to be 10 mg/L.

Based on the available result from one structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that the effects ofsorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated)(CAS 9005-65-6) will be in the same order of magnitude.