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EC number: - | CAS number: 91744-35-3
Sediment toxicity
Administrative data
Link to relevant study record(s)
Description of key information
The chemical safety assessment according to Annex I of Regulation (EC) No. 1907/2006 does not indicate the need to investigate further the effects on sediment organisms.
Key value for chemical safety assessment
Additional information
No experimental data evaluating the toxicity to sediment organisms is available for Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates (CAS No. 97593-30-1). Since the substance is readily biodegradable, exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the maximum achievable concentration in test medium. In addition, available data indicate that Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetatesis not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.
Intrinsic properties and fate
Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetatesis readily biodegradable (83% biodegradation in 28 days; Weyers, 2007). 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, 2008). Therefore, after passing through conventional STPs, only low concentrations of these substances are likely to be (if at all) released into the environment.
Furthermore, the substance exhibits a log Koc value > 3.5. Therefore, once the substance enters conventional STPs, it is expected to be removed from the water column to a significant degree by adsorption to sewage sludge (Guidance on information requirements and chemical safety assessment, Chapter R.7a, (ECHA, 2008)) and the rest will be extensively biodegraded (due to ready biodegradability). Thus, discharged concentrations of these substances into the aqueous/sediment compartment are likely to be negligible.
Considering this, one can assume that the availability of Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates in the sediment environment is generally very low, which reduces the probability of exposure of sediment organisms in general.
Aquatic ecotoxicity data
Acute and chronic aquatic toxicity tests performed on fish, invertebrates, algae and microorganisms showed no adverse effects occurred up to the maximum achievable concentration in test medium. The obtained results indicate that Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates is likely to show no toxicity to sediment organisms as well.
Metabolism/Bioaccumulation
After uptake, Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetatesis expected to be enzymatically hydrolyzed by carboxylesterases. QSAR estimations using BCFBAF v3.01 support the expected rapid biotransformation of this substance with BCF/BAF values of 0.91 and 12.3 L/kg.
The metabolism of the main hydrolysis products: alcohol (i.e. glycerol) and fatty acids is well established and not of concern in terms of bioaccumulation. Glycerides, especially triglycerides, are the predominant lipid class in the diet of both marine and freshwater fish. Once ingested, they will be hydrolized into fatty acids and glycerol by a specific group of carboxylesterase (CaE) enzymes (lipases) as reported in different fish species (Tocher, 2003). In the case of Glycerides, C8-21 and C8-21 unsatd., mono- and di-, acetates (CAS No. 97593-30-1) the enzymatic hydrolysis is expected to result in C8-C21 (saturated and unsaturated) fatty acids, glycerol and acetic acid as transformation products. Part of the free fatty acids will be re-sterified once more with glycerol and partial acyl glycerols to form triglycerides, that will be stored as long-term energy reserves. 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).
Moreover, acetic acid is naturally present in living organisms. The combination of its ionized form (acetate) with coenzyme A (CoA) plays a major role as intermediate in the citric acid cycle (acetyl-CoA)(Lehninger, Nelson and Cox (1994)). The log Kow value reported for acetic acid is -0.17 (Hansch et al., 1995), indicating no potential for bioaccumulation. Therefore, acetic acid it is expected to be extensively metabolized and not bioaccumulated in aquatic organisms.
In conclusion, no potential for bioaccumulation is to be expected forGlycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates.
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 the high log Kow and adsorption potential, Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates 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 (0.91-12.3 L/kg). Furthermore, aquatic toxicity data show that no effects occur up to the maximum achievable concentration in test medium. Therefore,Glycerides, C8-21 and C8-21-unsaturated, mono- and di-, acetates is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.
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