Glycerides, C8-10 mono- and di-

Short-term toxicity to fish

Description of key information

No toxicity up to the limit of water solubility (WS 46 mg/L)

Additional information

The acute toxicity of Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) to fish species was investigated by Hafner (2013). Danio rerio was firstly exposed to the test substance in a preliminary limit test at 100 mg/L (loading rate). Six out of seven test organisms died after 48 hours. Therefore, for the definitive test, a range of nominal loading rates from 6.25 to 100 mg/L were prepared. Analytical measurement of the highest (100 mg/L) and middle (25 mg/L) concentrations was performed via TOC and DOC analysis. Initial concentrations in these two vessels resulted in values of 21.9 mg/L and 11.5 mg/L (DOC). Nevertheless, inconsistent results were obtained when comparing start and final concentrations and, according to the authors, should be taken with caution.

 

Danio rerio was exposed to the test substance for 96 hours within a static water regime. After the exposure period, 100% mortality was reported at the highest loading rate of 100 mg/L, whereas no mortality was observed in any other treatment group, leading to a LL50 (96 h) of 75 mg/L (nominal, loading rate).

 

Nevertheless, the observed effects occurred above the water solubility of the substance, and seem to be caused by direct physical interference of test material particles with fish, rather than due to toxicity. For both preliminary and final tests Water Accommodated Fractions (WAFs) were prepared by adding the test material into water, stirring for a period of 48 hours, followed by a sedimentation period of 1 hour. After the sedimentation period, the 100 mg/L loading rate appeared to be turbid, containing visible oil drops. The test solutions were prepared without a filtration step. According to the reported results information, fishes in this vessel were strongly affected already after 24 h, swimming slowly and laying in the bottom of the aquarium. One fish also swam on the surface and gasped. Considering the above information, undissolved test material present at this loading rate could be responsible for the observed effects (via gill clogging). This statement is supported by the observations made in the acute tests conducted with aquatic invertebrates and algae, for which physical effects cannot be excluded either.

 

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, C8-10 mono- and di- contains mixed mono and diester C8-10 fatty acids and formation of microemulsions in test solutions is therefore possible for this substance.

 

Although the effect values of the study are to be taken with caution, due to probable physical effects, it can be concluded that no mortality occurred up to a concentration of 50 mg/L, which is above the water solubility limit of the substance. Therefore, no toxicity of Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) to fish species up to the limit of the water solubility is expected.