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Short-term toxicity to aquatic invertebrates

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Description of key information

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

Key value for chemical safety assessment

Additional information

One study evaluating the acute toxicity of Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) to aquatic invertebrates is available (Hafner, 2013). 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 5.8 mg/L to 300 mg/L (WAF, according to the results of a non-GLP range-finding test). The test was performed under static water conditions. Analytical measurement of the highest (300 mg/L), two middle (62 and 28.2 mg/L) and the lowest (5.8 mg/L) loading rates was performed via TOC and DOC analysis. After the exposure period, 100% immobilization was reported at the 300 mg/L loading rate, whereas no immobilization was observed in any other treatment group. The resulting EL50 (48 h) was determined to be 218.2 mg/L (based loading rate) and 102.6 mg/L (based on measured test concentration).

 

Nevertheless, the observed immobilization seems to be caused by direct physical interference of test substance particles with the daphnids, rather than due to toxicity. The measured concentration at which effects were reported (102.6 mg/L) is well above the water solubility of the substance (WS 46 mg/L). 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 WAFs with the highest loading rates appeared to be slightly 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, 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 136.4 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 aquatic invertebrates up to the limit of the water solubility is expected.

 

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