Glycerides, C12-18 mono- and di-

Short-term toxicity to aquatic invertebrates

Description of key information

No effects up to the limit of water solubility (WS 3.3 mg/L)

Additional information

The acute toxicity of Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) to aquatic invertebrates is available (Hafner, 2012). This test was performed according to OECD 202, under GLP conditions. Daphnia magna was exposed to the test substance for a period of 48 hours at nominal loading rates ranging from 6.25 mg/L to 100 mg/L (WAF). The test was performed under static water conditions. Analytical measurement of the highest (100 mg/L), middle (25 mg/L) and the lowest (6.25 mg/L) loading rates was performed via TOC and DOC analysis. Mean measured concentrations were determined to be 1.7 mg/L (6.25 mg/L nominal), 4.3 mg/L (25 mg/L nominal) and 14.8 mg/L (100 mg/L nominal).

 

After the exposure period, 95% and 100% immobilization were reported at the highest loading rates of 50 and 100 mg/L, respectively. No immobilization was observed in any other treatment group. The resulting EL50 (48 h) was determined to be 36.2 mg/L (based on loading rate) and 5.6 mg/L (based on measured test concentration).

 

Nevertheless, the observed effects are above the water solubility (WS 3.3 mg/L) of the substance and might be caused by direct physical interference of test substance particles with test organisms (i.e. physical entrapment), rather than intrinsic toxicity. For this test, Water Accommodated Fractions (WAFs) were prepared by adding the test material into a defined volume of test medium, stirring for a period of 48 hours, followed by a sedimentation period of 1 hour. After the sedimentation period, the WAF with the highest loading rate appeared to be inhomogeneous and presented cloudy cords. The next two lower loading rates were turbid. The test solutions were prepared without a filtration step.

 

Scientific evidence showed that aquatic toxicity testing of this type of Glycerides is technically very difficult. In an article by Prajapati et al. (2012)(see IUCLID section 6.1.4), the phase behaviour of lipid/surfactant/water phases was investigated, where medium-chain (C8-10) mono-, di- and triglycerides represent the lipid. Phase boundaries between lipids (monoglycerides, diglycerides, triglycerides), surfactant (PEG-35 castor oil) and water were established by visual inspection after an equilibration period, and the results expressed in phase diagrams. Viscosity and particle size distribution were measured. The mixtures with monoglyceride displayed two predominant phases: microemulsion and emulsion phases, whereas di- and triglycerides showed additionally a gel phase. Mixtures of monoglycerides and diglycerides, and of monoglycerides and triglycerides seemed to promote an increase of the microemulsion phase (in the 4 phases equilibrium). Particle size in these mixtures was found to be much smaller than in the monoglyceride sample alone. Microemulsions are solutions with an average particle size < 0.2 µm. This particle size would not be intercepted by a standard filter used in an aquatic toxicity test (generally, pore size of 0.45 µm). Due to their small size, based on visual inspection, clear or translucent solutions might be observed even when these microemulsions are present. Glycerides, C12-18 mono- and di- contains 40-70% C12 fatty acids and formation of microemulsions in test solutions is therefore possible for this substance.

 

Based on the available information, no toxicity of Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) to aquatic invertebrates up to the limit of the water solubility is expected.