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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Taking all available information into account the substance is unlikely to pose a risk for aquatic algae.

Key value for chemical safety assessment

Additional information

Since no studies investigating the toxicity of Fatty acids, rape-oil, mixed esters with 1,4:3,6-dianhydro-d-glucitol, sorbitan and sorbitol (CAS 93334-10-2) to aquatic invertebrates are available, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5 a read across to the structurally related analogue substances sorbitane stearate (CAS 1338-41-6) and Sorbitan, (Z)-9-octadecenoate (2:3) (CAS 8007-43-0) was conducted.
This read-across is justified as all substances share a comparable structure. Based on the specification the target substance Fatty acids, rape-oil, mixed esters with 1,4:3,6-dianhydro-d-glucitol, sorbitan and sorbitol is characterized by the alcohol components sorbitol, sorbitan and 1,4:3,6-dianhydro-d-glucitol esterified as mono (mainly), -di- or tri-ester with mainly fatty acids of C18 and C18 unsaturated. The source substance sorbitan stearate (CAS 1338-41-6) is characterized as a mono-, di- and tri-ester of sorbitan with C16-C18 fatty acids. Sorbitan, (Z)-9-octadecenoate (2:3) (CAS 8007-43-0) is an ester (mono, di and tri) of sorbitan, sorbitol and 1,4:3,6-dianhydro-d-glucitol with C18 unsaturated fatty acid. Further justification is given within the endpoint summary 6.1 and within the analogue justification in section 13.

The first key study conducted with the source substance 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 Pseudokirchneriella subcapitata was exposed to the test substance in a static system for 72 hours, at 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 of growth was only observed at nominal 1000 mg/L, and NOELR 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 NOELR (72 h) 100 mg/L and EL50 (72 h) > 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.

The second key study with the source substance Sorbitan, (Z)-9-octadecenoate (2:3) (CAS 8007-43-0) was performed according to ISO 10253 (Hudson, 2003). The test organism Skeletonema costatum was exposed to the test substance in a static system for 72 h at nominal loading rates of 320, 1000, 3200, 5600 and 10000 mg/L. All loading rates were far above the solubility limit of the substance. Although the test was performed using 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 (72 h) 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.

Based on the result from one structurally related read-across substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) it can be concluded that Fatty acids, rape-oil, mixed esters with 1,4:3,6-dianhydro-d-glucitol, sorbitan and sorbitol will not exhibit effects to aquatic algae up to the limit of water solubility.