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Sediment toxicity

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Description of key information

Taking all available information into accounFatty acids, C18-unsatd., dimers, 2-ethylhexyl esters is unlikely to pose a risk for sediment organisms and testing is thus omitted.

Key value for chemical safety assessment

Additional information

No experimental data evaluating the toxicity to sediment organisms is available for Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters (CAS No. 68334-05-4). Since the substance is readily biodegradable, chronic exposure of sediment organisms is unlikely. Furthermore, the substance is not toxic to aquatic organisms up to the limit of water solubility. In addition, available data indicate, that the test substance is not bioaccumulative. Based on the available information, toxicity to sediment organisms is not expected to be of concern.

Intrinsic properties and fate

Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters (CAS No. 68334-05-4) 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 these substances are likely to be (if at all) released into the environment.

Furthermore, the substance exhibits a log Koc value of > 5 and is poorly water soluble (< 1 mg/L). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2012) states that once insoluble chemicals enter a standard STP, they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Nevertheless, once this contact takes place, these substances are 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, 2012)) 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 Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters in the sediment environment is generally very low, which reduces the probability of chronic exposure of sediment organisms in general.

Aquatic ecotoxicity data

Aquatic toxicity tests of the substance to fish, invertebrates, algae showed no adverse effects occurred in the range of the water solubility of the substance (< 1 mg/L). Furthermore, long-term data for algae and fish show no chronic effects in the range of the water solubility. The obtained results indicate that Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters is likely to show no toxicity to sediment organisms as well.

Metabolisms/Bioaccumulation

Bioaccumulation in sediment organisms is not expected for Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters. Based on the molecular weight (673 g/mol), size and structural complexity of the substances, which reduces significantly the absorption due to steric hindrance to cross biological membranes, uptake from medium into sediment organisms is considered to be low (e.g. Dimitrov et al., 2002).

The supporting BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation (BCF and BAF values of 0.89 L/kg and 0.89 L/kg, respectively), also indicate that this substance will not be bioaccumulative (all well below 2000 L/kg).

Conclusion

Due to its readily biodegradable nature, extensive degradation of the substance in conventional STPs will take place and only low concentrations are expected to be released (if at all) into the environment. Absorption of Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters is not expected due to the molecular weight (673 g/mol), size and structural complexity of the molecules. Therefore, the potential for bioaccumulation is low. Furthermore, aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, the Fatty acids, C18-unsatd., dimers, 2-ethylhexylesters is unlikely to pose a risk for sediment organisms in general and testing is thus omitted.