Sorbitan, (Z)-9-octadecenoate (2:3)

Toxicity to aquatic algae and cyanobacteria

Description of key information

No effects up to a loading rate of 100 mg/L (ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum), Skeletonema costatum)

Additional information

One saltwater study is available on the toxicity of Sorbitan, (Z)-9-octadecenoate (2:3) (CAS No. 8007-43-0) to algae. Since a NOEC could not be derived from this study, a read-across to Sorbitan stearate (CAS No. 1338-41-6) was additionally used for the assessment. This read across approach is in accordance with Regulation (EC) No 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Both substances consist mainly of Sorbitan esters of C18 fatty acids. Although Sorbitan stearate is saturated and Sorbitan, (Z)-9-octadecenoate (2:3) is unsaturated, the substances are expected to have similar behaviour, based on data available on solubility, ready biodegradability and toxicity to aquatic organisms.

The key study conducted with Sorbitan, (Z)-9-octadecenoate (2:3) (CAS No. 8007-43-0) was performed according to the guideline ISO 10253 (Water quality - Marine Algal Growth Inhibition Test with Skeletonema costatum and Phaeodactylum tricornutum). The test organism Skeletonema costatum was exposed to the test substance in a static system for 72 hours, at the nominal test concentrations of 320, 1000, 3200, 5600 and 10000 mg/L. All test concentrations were far above the solubility limit of the substance. Although the test was performed as water accommodated fractions (WAF), the presence of undissolved material cannot be excluded. Inhibition was observed already at the lowest test concentration, and a NOEC could thus not be determined. An EL50 of 1916 mg/L was derived. 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.

The key study conducted with Sorbitan stearate (CAS 1338-41-6) was performed according to the Circular on Test Methods of New Chemical Substances (Japan), Alga Growth Inhibition test and GLP (Ministry of the Environment, Japan, 2005). The test organism Pseudokirchnerella subcapitata was exposed to the test substance in a static system for 72 hours, at the nominal test concentrations of 100, 180, 320, 560 and 1000 mg/L. The test solutions were prepared as water accommodated fractions (WAF), but the reported measured concentrations far above the solubility limit of this substance indicate that undissolved material was present. Significant inhibition was only observed at 1000 mg/L, and NOEC and EL50 values of 560 mg/L and > 1000 mg/L, respectively were reported. 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. The results are also reported in measured concentrations as NOEC = 100 mg/L and EC50 > 122 mg/L. However, since these concentrations are far above the water solubility of the test substance, and because the substance is a UVCB, the assessment was based on the nominal concentrations.