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

Endpoint summary

Additional information

Based on an experimental study, Sorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated)(CAS 9005-65-6) is readily biodegradable according to the OECD (2006) criteria (61% biodegradation after 28 d). Therefore, the substance is not persistent in the environment. The degradation via abiotic hydrolysis is not considered to be a relevant degradation pathway in the environment since QSAR calculations using HYDROWIN v2.00 resulted in DT50 > 1 yr at pH 7. Evaporation into air and the transport through the atmospheric compartment is not expected based on the low vapour pressure (< 0.0001 Pa at 20 °C), thus also degradation by indirect photolysis is considered not to be a relevant environmental fate process.

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.

The substance is expected to adsorb to solid soil/sediment particles. Although the log Koc values estimated by QSAR are relatively low (2.9 - 3.1, KOCWIN v2.00, MCI), the substance has surface active properties, which increases the adsorption potential, but is not taken into account by the model (Chu and So, 2001; Laha et al., 2009). Consequently, the main environmental target compartments forSorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated)are the soil and sediment. However, the substance is expected to be eliminated extensively in sewage treatment plants, due to ready biodegradability and adsorption to sewage sludge. Release to surface waters and sediment, is therefore very unlikely. If the substance were to be released in the environment, it is expected to be rapidly degraded by microorganisms in both aquatic and terrestrial compartments.

Bioaccumulation is not expected forSorbitan monooleate, ethoxylated (1-6.5 moles ethoxylated), based on low calculated BCF values of 12.6 - 14.6 L/kg ww (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic). Moreover, the exposure via water is expected to be very low (low solubility and ready biodegradation) and the substance is expected to be digested by common metabolic pathways (Berg et al., 2002; Wick, 1953; Tocher, 2003).