Glycerides, mixed C8-10 and succinyl

Endpoint summary

Additional information

The acute toxicity studies conducted with Glycerides, mixed C8-10 and succinyl on fish and aquatic invertebrates showed no effects of the substance up to the limit of its water solubility (1-2 mg/L), with LL50 and EL50 values > 70 mg/L and > 100 mg/L (loading rates), corresponding to measured concentrations > 2.0 mg/L and > 10.7 mg/L, respectively. Effects on growth rate were reported on the test conducted with algae, resulting in an EL50 (72 h) of 67.7 mg/L (loading rate) and a NOEC (72 h) of 20.9 mg/L (loading rate, corresponding to a mean measured concentration of 1.7 mg/L). Nevertheless, the report states that the possibility of physical effects (due to disturbance of algae cells by emulsified test substance) cannot be excluded. The test material was reported to be sparingly soluble and therefore Water Accomodated Fractions (WAFs) were prepared. The WAFs were stirred for 48 hours and thereafter left for sedimentation for a period of 1 hour. After the sedimentation period, the WAFs were not completely clear. Filtration of the WAFs for the preparation of final test solutions was not performed. The observed effects occurred above the water solubility of the substance (WS 1-2 mg/L), nevertheless the NOEC based on measured mean concentration is 1.7 mg/L, within the water solubility range. Therefore, this value is used for PNEC derivation as a worst-case approach.

 

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, mixed C8-10 and succinyl contains mixed C8-10 fatty acids mono-, di- and triester and formation of microemulsions in test solutions is therefore possible. The only test conducted with this substance showing effects was the algae test, in which the WAFs were reported to be not completely clear, even though suspended particles could not be directly observed. This is considered as an indication of a microemulsion-formation phase, showing that the observed effects in the algae test might indeed be due to physical interference with emulsified test material. The chances of microemulsion formation under chronic exposure to this substance are very high. Due to the prolonged testing period for these long-term toxicity tests, microemulsions can cause physical effects on fish (e.g gill clogging) and aquatic invertebrates (e.g. physical entrapment). Therefore, obtaining reliable chronic values out of such tests is technically difficult. Furthermore, based on the results of the acute tests, there is no indication showing that Glycerides, mixed C8-10 and succinyl is toxic to fish and aquatic invertebrates, whereas a NOEC value is available for the species showing the highest sensitivity (algae). Therefore, long-term toxicity testing is not deemed necessary for this substance.

Toxicity to aquatic microorganisms is not anticipated for Glycerides, mixed C8-10 and succinyl. The substance is readily biodegradable (81.7% biodegradation in 28 days). According to the Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012), the assumption that a certain substance is not inhibitory of microorganisms activity is implicit in ready biodegradability tests. If a compound degrades well in such a test, or does not inhibit the biodegradation of a positive control at a certain concentration, this concentration can be used as NOEC value. The toxicity control, containing 45.5 mg/L test material showed 78.7% biodegradation within 14 days, clearly indicating lack of toxicity to activated sludge microorganisms.