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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

No effects up to a loading rate of 100 mg/L of the test substance for Pseudokirchnerella subcapitata (Circular on Test Methods of New Chemical Substances (Japan)); read-across

Key value for chemical safety assessment

Additional information

No studies are available on the toxicity of Sorbitan tristearate (CAS No. 26658-19-5) to algae. The assessment was, therefore, based on a study conducted with the structurally similar category member Sorbitan stearate (CAS No. 1338-41-6), as part of a read-across approach. This is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Grouping of substance and read across approach. Sorbitan tristearate and Sorbitan stearate are both Sorbitan esters of saturated C18 fatty acids. Since Sorbitan stearate mainly consists of monoesters, it can be considered a worst case read-across to Sorbitan tristearate, which is expected to be less bioavailable due to its molecular size (MW 879-982). 

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.