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Toxicity to aquatic algae and cyanobacteria

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Description of key information

No toxic effects on aquatic algae up to the limit of water solubility, read across.

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Data on the short-term toxicity of 1,2,3-propanetriyl triisooctadecanoate (CAS 26942-95-0) to aquatic algae are not available. The assessment was therefore based on studies conducted with the structurally similar substances, Glycerides, C14-18 and C16-18-unsatd. mono-, di- and tri- (CAS 91052-28-7) and Glycerides, C16-18 and C18 unsatd (CAS 67701-30-8) as part of a read across approach, which is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Further justification is given within the overall summary chapter 6.1 and within the analogue justification section 13.

The toxicity of Glycerides, C14-18 and C16-18 unsaturated, mono-, di- and tri- (CAS No. 91052-28-7) to algae was tested according to OECD Guideline 201, under GLP conditions (Salinas, 2013). Desmodesmus subspicatus was exposed for 72 hours to the test substance at test concentrations of 3.2, 10, 32, 100 and 320 mg/L (nominal, loading rate). Chlorophyll-a fluorescence (pulsed excitation with light flashes having a wavelength of 430 nm) was the measured test parameter. Nevertheless, cell density was also determined in order to derive the linear correlation between both parameters. After 72 hours of exposure, effects on algal growth rate were observed at concentrations of 100 mg/L and 320 mg/L, leading to an ErL10 of 172 mg/L and a NOELR of 32 mg/L (nominal, loading rate). The ErL50 was determined to be > 320 mg/L (nominal, loading rate). The reported effects are well above the water solubility of the substance (WS <0.05 mg/L) and therefore, they could be caused by physical interference or adsorption between algae and the test substance. Nevertheless, stock solutions were reported to be colourless and clear, and therefore, effects due to toxicity cannot be discarded.

The study with the source substance Glycerides, C16-18 and C18-unsatd. (CAS 67701-30-8) was conducted according to EU Method C.3 (Algal Inhibition test) (GLP) with the freshwater algae Scenedesmus subspicatus (Rieche, 1996). The test was performed with additional consideration of the VCI concept for poorly soluble substances. Thus, two different test solutions with a nominal substance concentration of 100 mg/L were prepared. The first solution was prepared by directly weighing the test substance into the test vessel; the undissolved substance was not removed. The second solution was prepared by separating any undissolved test substance through filtration. After 72 hours of exposure, effects on algal growth rate were observed at concentrations of 100 mg/L in the unfiltered test solution. Whereas no effect on the growth rate of Scenedesmus subspicatus was observed in the filtrated solutions. The observed effects were most probably due to physical effects by undissolved test substance. Thus, it can be stated that no effect up to the limit of the water solubility of the test substances occurred under conditions tested.

Based on these results from structurally related source substances (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which are characterized by a similar ecotoxicological profile, toxicological effects on aquatic algae are not expected up to the limit of water solubility for 1,2,3-propanetriyl triisooctadecanoate (CAS 26942-95-0).