Glycerides, C8-18

Short-term toxicity to fish

Description of key information

No toxicity up to the limit of water solubility (WS 2-3 mg/L)

Additional information

No experimental data evaluating the acute toxicity of Glycerides, C8-18 (CAS No. 85536-06-7) to fish species are available. Therefore, toxicity data from structurally related category members (castor oil, hydrogenated (CAS No. 8001-78-3),Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) and Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) are used as read-across according to Regulation (EC) No. 1907/2006, Annex XI, 1.5. All four substances are esters formed from the combination of fatty acids and glycerol. The target substance contains fatty acids with C-chain lengths ranging from C8 to C18, and >80% triester content. The three read-across substances cover the fatty acid C-chain range of the target substance, being C8-10 for CAS No. 85536-07-8, C12-18 for CAS No. 91052-49-2 and C18 (hydrogenated) for CAS No. 8001-78-3. Castor oil, hydrogenated (CAS No. 8001-78-3) is predominantly a triglyceride (> 80% triester content). The triester content of Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) and Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) is < 15%, being predominantly mono- and diesters. Due to differences on the degree of esterification of these two substances with respect to Glycerides, C8-18 (CAS No. 85536-06-7), a higher bioavailability to aquatic organisms can be expected for the read-across substances (CAS No. 85536-07-8 and CAS No. 91052-49-2). Generally, a higher degree of esterification will result in an increase of molecular size and weight of the substance. At higher molecular size and weight, the potential to cross biological membranes tends to decrease (Guidance on information requirements and chemical safety assessment, Chapter R.11 (ECHA, 2012). Considering this information, reading across from Glycerides, C8-C10, mono- and di- (CAS No. 85536-07-8) and Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) represents a worst-case scenario for the target substance and therefore it is justified.

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 with this substance. In the algae test, the physical nature of the reported effects is clear.

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.

 

One study evaluating the acute toxicity of Glycerides, C12-18 mono- and di- (CAS No. 91052-49-2) to fish species is available (Hafner, 2012). This test was conducted according to OECD 203, under GLP conditions. Danio rerio was exposed for 96 hours in a limit test to a nominal loading rate of 20 mg/L (Water Accomodated Fraction (WAF)). This concentration was chosen based on the results obtained in the tests conducted on algae and aquatic invertebrates, which resulted in EL50 values of 13 mg/L and 36.5 mg/L, respectively (loading rates). This approach is in accordance with the OECD Guidance document No. 126 “Threshold approach for acute fish toxicity” (2010).The Water Accommodated Fraction (WAF) was prepared by adding the test material into water, stirring for a period of 48 hours, followed by a sedimentation period of about 70 minutes. After the sedimentation period, the WAF was clear. Very small crumbs of test item were however, observed on the surface and at the bottom of the beakers. The test solution was prepared without a further filtration step. Analytical measurements of the test concentration were performed via TOC and DOC analysis at the start and at the end of the test. The initial concentration was determined to be 1.8 mg/L, whereas 1.9 mg/L were reported at the end of the test (DOC). The latter value corresponds to a measured test concentration of 2.7 mg/L test material. After 96 hours of exposure to the test substance, no mortality was reported in control or treatment group and therefore, the LL50 (96 h) was determined to be > 20 mg/L (nominal, loading rate) and > 2.7 mg/L (measured final test material concentration).

A study was conducted with castor oil hydrogenated (CAS No. 8001-78-3) according to ISO 7346-1. Fish (Danio rerio) were exposed for 96 hours to the test substance within a semi-static water regime, at nominal concentrations of 1000, 3000 and 10000 mg/L. No mortality was observed at any of the tested concentrations and therefore the LC50 (96 h) was determined to be > 10,000 mg/L (nominal concentration).

                                                               

Although the effect values of the study conducted with Glycerides, C8-10, mono- and di- (CAS No. 85536-07-8) are to be taken with caution, due to probable physical effects, it can be concluded that no mortality occurred up to a nominal loading rate of 50 mg/L. This value is well above the water solubility limit of Glycerides, C8-18 (CAS No 85536-06-7), 2-3 mg/L. Considering this information and that no toxicity up to the limit of water solubility was observed in the tests conducted with the other read-across substances, no toxicity of Glycerides C8-18 (CAS No 85536-06-7) to fish species up to the limit of the water solubility is expected.