Sorbitan C16-18 (even numbered) fatty acid esters, ethoxylated (1-6.5 moles ethoxylated)

Endpoint summary

Additional information

In order to fulfil the standard information requirements a read-across from three structurally related substances was conducted in accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006. According to Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular for aquatic toxicity, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across).

Having regard to the general rules for grouping of substances and read-across approach laid down in Annex XI, Item 1.5, of Regulation (EC) No 1907/2006 whereby substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

The target substance belongs to the family of ethoxylated sorbitan fatty acid esters, also called polysorbates. Polysorbates are produced by partial esterification of sorbitan with a fatty acid followed by polymerization with ethylene oxide. Polysorbates differ in the number of ethoxy groups and the number and types of fatty acid moieties (EPA, 2005). The source substances belonging to this family and being considered suitable a structural analogue based on the presence of common functional groups is polysorbate 21 (CAS 9005-64-5, sorbitan monolaurate, ethoxylated, a shorter chain (C12 fatty acid) analogue). The remaining two source substances belong to the family “sorbitan fatty acid esters”, which are generally produced via esterification of sorbitan with a fatty acid to give the respective mono-, di-, tri- and n-esters as products of esterification (JECFA, 1973; Gennaro, 1990; Canterbery, 1997). They are non-ethoxylated analogues of respective ethoxylated substances involved, i.e. stearates and laurate: sorbitan monostearate (CAS 1338-41-6) and sorbitan monolaurate (CAS 1338-39-2).

Aquatic toxicity

The endpoints short-term toxicity to fish, short-term toxicity to aquatic invertebrates, long-term toxicity to aquatic invertebrates, toxicity to algae as well as toxicity to microorganisms were covered by the suitable read-across substances sorbitan stearate (CAS 1338-41-6), sorbitan laurate (CAS 1338-39-2) and sorbitan monolaurate, ethoxylated (CAS 9005-64-5).

The short-term toxicity to fish was investigated in one study according to Circular on Test Methods of New Chemical Substances (Japan, MoE, 2005) with the source substance sorbitan stearate (CAS 1338-41-6). A limit test with a nominal Water Accommodated Fraction (WAF) of 1000 mg/L was tested. No mortality of the test organism Oryzias latipes was recorded after 96 h resulting in a LL50 (96 h) of > 1000 mg/L. A further study on fish toxicity of the source substance sorbitan laurate (CAS 1338-39-2) led to similar results. The study was performed as a limit test, with Danio rerio as the test organism according to OECD guideline 203 and GLP (Teigeler, 2012). The fish were exposed to the nominal loading rate of 100 mg/L, prepared as water accommodated fractions (WAF) and no mortalities were observed at the test concentration, during the 96 h test period resulting in a LC50 > 100 mg/L (nominal, WAF). A further study with Danio rerio exposed to 100 mg/L (nominal, WAF) of the source substance sorbitan monolaurate, ethoxylated (CAS 9005-64-5) led to the same result (LC50 (96 h) > 100 mg/L). 

The short-term toxicity to aquatic invertebrates was investigated in one study with the source substance sorbitan stearate (CAS 1338-41-6) and Daphnia magna. The study was performed according to the Circular on Test Methods of New Chemical Substances (Japan, MoE, 2006). The test organism was exposed to nominal test concentrations between 100 and 1000 mg test item/L for 48 h. No immobilisation was observed at any of the test concentrations and the EL50 (48 h) was found to be > 1000 mg/L (nominal). A further study with the source substance sorbitan laurate (CAS 1338-39-2) and marine aquatic invertebrates was performed according to the ISO proposal (1990) for ISO 14669 (1999) water quality-determination of acute lethal toxicity to marine copepods (Hudson, 1999). Acartia tonsa was exposed to the test substance in a static system for 48 h, at nominal loading rates between 32 and 3200 mg/L. The test solutions were prepared as water accommodated fractions (WAF), but the presence of undissolved material cannot be excluded at such high loadings. Effects were observed and resulted in an LL50 (48 h) of 452.84 mg/L (nominal, WAF). These effects are most likely related to physical effects.

Since sorbitan C16-18 (even numbered) fatty acid esters, ethoxylated (1-6.5 moles ethoxylated) is poorly soluble, long-term testing with aquatic invertebrates was considered to be meaningful. The available long-term study with the read-across substance sorbitan stearate (CAS 1338-41-6) was conducted according to OECD 211 (GLP) with the water flea Daphnia magna (MoE, 2006). At the three higher concentrations, 100% mortality of the parental Daphnia occurred. The NOELR (21 d) was determined to be ≥ 16 mg/L based on reproduction. Above this loading rate 100% mortality was observed. It was reported that undissolved test material was present in the solutions which probably have caused the effects. A further 21 d study conducted with the source substance sorbitan monolaurate, ethoxylated (CAS 9005-64-5) and Daphnia magna exposed to loading rates between 1 and 100 mg/L (nominal, WAF) showed effects on parental body length, effects on reproduction and 60% parental mortality at the loading rate of 32 mg test item/L (Schlechtriem, 2012). 100% mortality of the parent animals was observed at the 100 mg/L loading rate. Based on these results NOELR (21 d) for reproduction was determined to be 10 mg/L.

Toxicity testing with aquatic algae was conducted according to Circular on Test Methods of New Chemical Substances (Japan), Alga Growth Inhibition test and GLP with the freshwater algae Pseudokirchneriella subcapitata and the read-across substance sorbitan stearate (CAS 1338-41-6) (MoE, 2005). The test organism was exposed to the test substance in a static system for 72 h, at the nominal loading rates of 100 and 1000 mg/L. NOELR (72 h) and EL50 (72 h) values of 560 mg/L and > 1000 mg/L (nominal, WAF), respectively, were determined. It is, however, very likely that the effect at the highest tested concentration was due to the turbidity of the test solution, caused by the undissolved test material. A further study with the source substance sorbitan laurate (CAS 1338-39-2) and Skeletonema costatum, performed according to the ISO 10253, EPA/600/4-85/013 and GLP is available (Hudson, 1999). The test organism was exposed to the test substance in a static system for 72 h, at nominal loading rates (prepared as water accommodated fractions) between 3.2 and 320 mg/L. An EL50 (72 h) of 17.89 mg/L (nominal, WAF) and a NOELR of ≥ 10 mg/L (nominal, WAF) was derived. A further study with the read across substance sorbitan monolaurate, ethoxylated (CAS 9005-64-5) and Pseudokirchneriella subcapitata exposed to loading rates between 1 and 100 mg/L (nominal, WAF) resulted in ErL50 and ErL10 values of 58.84 mg/L and 19.05 mg/L, respectively (Wenzel, 2012).

The degradation process in sewage treatment plants (STP) is not considered to be inhibited based on the result of a toxicity control with activated sludge microorganisms from a commercial STP according to OECD 209 and GLP (Desmares-Koopmans, 2010). The study was performed with the suitable source substance sorbitan monolaurate (CAS 1338-39-2). No inhibition of degradation was observed up to a limit concentration of 100 mg/L resulting in an EC50 (3 h) > 100 mg/L.

In summary, based on experimental data from suitable read-across substances, the target substance is of low toxicity to aquatic organisms.

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