Isooctadecanoic acid, monoester with glycerol

Toxicity to aquatic algae and cyanobacteria

Description of key information

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

Additional information

Data on the short-term toxicity of Glycerol monoisostearate (CAS 66085-00-5) to aquatic algae are not available. The assessment was therefore based on studies conducted with the structurally similar substances, 1,2,3-propanetriyl trioleate (CAS 122-32-7) and Glycerides, C14-18 and C16-18-unsatd. mono-, di- and tri- (CAS 91052-28-7) 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 acute toxicity of 1,2,3-propanetriyl trioleate (CAS 122-32-7) to algae was conducted according to the US EPA Algal, Selenastrum capricornutum, growth test method 1003.0 (EPA 600/4-89/001) (Kamaya, 2003). Selenastrum capricornutum was exposed to the test substance at 24 ± 1°C for 96 hours. The cell concentrations were determined by means of a microscope and hemocytometer every 24 hours. Exponential growth in the control was maintained throughout all the testing period. After 96 hours of exposure, no inhibition of algal growth was observed in the treatment group compared to control values. Therefore, both IC50 (72 h) and IC50 (92 h) were determined to be > 5 mg/L (nominal concentration). Thus, no toxicity up to the limit of water solubility of 1,2,3-propanetriyl trioleate (< 0.05 mg/L) was observed. 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 (water solubility < 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. Thus, based on the above mentioned result, and due to the structural and profile similarities of the substances, as are explained with in the overall endpoint summary 6.1 it can be concluded that no toxicological effects on algae are expected up to the limit of water solubility for Glycerol monoisostearate (CAS 66085-00-5).