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Description of key information

The chemical safety assessment according to Annex I does not indicate the need to conduct a test on sediment organisms.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the toxicity to sediment organisms is available for Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4). Since the substance is readily biodegradable, exposure of sediment organisms is the aquatic environment is unlikely. Furthermore, the substance showed no toxicity to fish up to the limit of water solubility. Effects were observed in the tests conducted with aquatic invertebrates and algae, but they are expected to be physical, due to interference of emulsified substance with test organisms. In addition, available data indicate that Glycerides, C12-18 di- and tri- is not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

 

Intrinsic properties and fate

Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) is readily biodegradable.According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b, readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological Sewage Treatment Plants (STPs)(ECHA, 2012). Therefore, after passing through conventional STPs, only low concentrations of this substance are likely to be (if at all) released into the environment.

The water solubility of Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) was determined to be 4-7 mg/L. On the other hand, the estimated log Koc values (≥ 4.8) indicate that the substance has potential for adsorption to solid particles. Therefore, besides being extensively biodegraded in STPs (due to its ready biodegradability), a significant degree of removal of this substance from the water column due to adsorption to sewage sludge can be expected (Guidance on information requirements and chemical safety assessment, Chapter R.7a (ECHA, 2012)). Discharged concentrations into the aquatic compartment are therefore likely to be low.

 

Considering the above information, the availability of Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) in the sediment environment is expected to be very low, which reduces the probability of sediment organisms exposure.

 

Aquatic toxicity

The acute toxicity test performed on fish showed no adverse effects occurred in the range of the water solubility of the substance (4-7 mg/L). Effects were observed in the tests conducted with aquatic invertebrates and algae. However, the WAFs in these two tests, in which effects were observed later on, were reported to be turbid. The WAFs were not filtered for the final tests.Therefore, physical effects due to interference with emulsified test substance with daphnids and algae cannot be excluded.

 

The obtained results indicate that Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) is likely to show no or only low toxicity to sediment organisms as well.

 

Metabolism/Bioaccumulation

After uptake, Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) is expected to be enzymatically hydrolyzed by carboxylesterases. QSAR estimations using BCFBAF v3.01 support the expected rapid biotransformation of this substance with BCF/BAF ranging from 0.89 to 1.3 L/kg.

 

Rapid metabolization of Glycerides, C12-18 di- and tri- in aquatic organisms is expected. Enzymatic hydrolysis is expected to result in C12-18 fatty acids and glycerol as transformation products. Part of the free fatty acids will be re-esterified with glycerol and partial acyl glycerols to form triglycerides that will be stored as long-term energy reserves (Tocher, 2003). Glycerol is naturally present in animal and vegetable fats, rarely found in free state (mostly combined with fatty acids forming triglycerides)(ed. Knothe, van Gerpen and Krahl, 2005). If freely available in aquatic organisms, it will not bioaccumulate in view of its log Kow value of -1.76 (OECD SIDS, 2002). Especially in periods in which the energy demand is high (reproduction, migration, etc.), glycerides are mobilized from the storage sites as source of fatty acids. Fatty acid catabolism is the most important energy source in many species of fish, resulting in the release of acetyl CoA and NADH (throughβ-oxidation) and eventually, via the tricarboxylic cycle, the production of metabolic energy in the form of ATP. This fatty acid-catabolism pathway is the predominant source of energy related to growth, reproduction and development from egg to adult fish. A similar metabolic pathway is observed in mammals (see section 7.1.1 Basic toxicokinetics). According to the Guidance on information requirements and chemical safety assessment, Chapter R.7c (ECHA, 2012), even though ready biodegradability does not per se preclude bioaccumulation potential, generally (depending on exposure and uptake rates) ready biodegradable substances are likely to be rapidly metabolised, and therefore, concentrations stored in aquatic organisms will tend to be low.

 

In conclusion, low bioaccumulation potential of Glycerides, C12-18 di- and tri- (CAS No. 91744-28-4) is expected.

 

Conclusion

Due to its readily biodegradable nature, extensive degradation of this substance in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Once present in the aquatic compartment, further biodegradation will occur and, due to its adsorption potential, Glycerides, C12-18 di- and tri- will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. After uptake by sediment species, extensive and fast biotransformation of the substance by carboxylesterases into fatty acids and glycerol is expected. The supporting BCF/BAF values estimated with the BCFBAFv3.01 program, Arnot-Gobas model including biotransformation, also indicate that this substance will not be bioaccumulative (0.89-1.3 L/kg). Furthermore, based on the aquatic toxicity data, the toxicity to aquatic organisms is expected to be low (if observed at all). Therefore, Glycerides, C12-C18, di- and tri- is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.

 

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR.