Glycerides, mixed coco, decanoyl and octanoyl

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErL50 (72 h) > 320 mg/L (nominal, loading rate) for Desmodesmus subspicatus (OECD 201)
NOELR (72 h) = 32 mg/L (nominal, loading rate) for Desmodesmus subspicatus (OECD 201)

Additional information

No experimental data evaluating the acute toxicity of Glycerides, mixed coco, decanoyl and octanoyl (CAS No. 68606-18-8) to fish species are available. Therefore, toxicity data from analogue category members, propane-1,2,3-triyl trisheptanoate (CAS No. 620-67-7), 1,2,3-propanetriyl trioleate (CAS No. 122-32-7) and Glycerides,C14-18 and C16-18 unsaturated, mono-, di- and tri- (CAS No. 91052-28-7), are used as read-across in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Glycerides, mixed coco, decanoyl and octanoyl is mainly a triglyceride formed by the combination of fatty acids of different C-chain lengths (C6 to C18 unsaturated) and glycerol. Propane-1,2,3-triyl trisheptanoate (CAS No. 620-67-7) and 1,2,3-propanetriyl trioleate (CAS No. 122-32-7) are also triglycerides with fatty acid chain lengths of C7 and C12 to C18 unsaturated respectively. For Glycerides,C14-18 and C16-18 unsaturated, mono-, di- and tri- (CAS No. 91052-28-7) the triester content is lower than for the other three substances (up to 15%), with a predominant monoester content. The lower degree of esterification might have an effect in the bioavailability to aquatic organisms, due to a reduced size of the molecules, the potential to cross biological membranes is expected to increase. Therefore, Glycerides,C14-18 and C16-18 unsaturated, mono-, di- and tri- can be regarded as a worst-case read-across substance.The behaviour of these four substances in the water phase is expected to be very similar based on low water solubility values (< 0.05 mg/L for all) and log Pow (> 4). The three read-across substances cover the whole fatty acid C-chain range present in Glycerides, mixed coco, decanoyl and octanoyl. Therefore, they are considered to give a reliable indication of the toxicity of this substance to aquatic organisms, and the read-across is justified.

One study evaluating the toxicity of propane-1,2,3-triyl trisheptanoate (CAS No. 620-67-7) to algae is available (Scholz, 1993). This test was conducted according to the Algal Inhibition Test described in the EU Directive 88/302, under GLP conditions. Desmodesmus subspicatus was exposed for 72 hours to the test substance at 24 ± 2°C and cell concentrations were recorded photometrically every 24 hours. During the 72 hours of exposure, no adverse effects in algal growth were observed in the treatment groups compared to control values. Therefore, the EC50 (72 h) was determined to be > 1.8 mg/L (nominal concentration). A publication evaluating the toxicity of 1,2,3-propanetriyl trioleate (CAS No. 122-32-7) to algae is available (Kamaya, 2003). This test was conducted according to the US EPA Algal, Selenastrum capricornutum, growth test method 1003.0 (EPA 600/4-89/001). Selenastrum capricornutum was exposed for 96 hours to the test substance at 24 ± 1°C and 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). On the other hand, a test evaluating the toxicity of Glycerides,C14-18 and C16-18 unsaturated, mono-, di- and tri- (CAS No. 91052-28-7) to algae was performed by Salinas (2013).This test was conducted according to OECD Guideline 201, under GLP conditions. 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.

 

Based on the results obtained for the structurally related analogues (in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5), Glycerides, mixed coco, decanoyl and octanoyl (CAS No. 68606-18-8) could exhibit low toxicity to algae.