Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters

Sediment toxicity

Description of key information

Taking all available information into account, Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters (CAS 68440-06-2)  is unlikely to pose a risk for sediment organisms and testing is thus omitted.

Additional information

No experimental data evaluating the toxicity to sediment organisms are available for Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters (CAS 68440-06-2). Only negligible releases into surface waters from sewage treatment plants are expected to take place due to the high adsorption potential of this substance, resulting in an effective removal in sewage treatment plants. Therefore, 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 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, hydrogenated, 2-ethylhexyl esters is not readily biodegradable but shows a good degradation of 49% after 28 d. A plateau was not reached and it is likely that the substance reaches the trigger value of 60% within 60 d. Therefore, after passing through conventional STPs, the concentration of the substance is likely to be less compared to the influent and biodegradation occurs to a certain extent.

Furthermore, the substance exhibits a log Koc value of > 5 and is poorly water soluble (16 ± 7 µg/L at 20 °C, pH 6.3). The Guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2014b) 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, 2014a)). 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, hydrogenated, 2-ethylhexyl esters in the sediment environment is very low, which reduces the probability of chronic exposure of sediment organisms in general.

 

Aquatic ecotoxicity data

Available acute data with fish, aquatic invertebrates and algae as well as chronic aquatic toxicity tests aquatic algae showed that no adverse effects occurred in the range of the water solubility (16 ± 7 µg/L at 20 °C, pH 6.3). Moreover, no toxic effects on activated sludge microorganisms were observed. The results obtained indicate that the substance is likely to show no toxicity to sediment organisms as well. It is not expected that results from additional studies with sediment organisms will lie out of the overall ecotoxicological profile of the substance.

 

Bioaccumulation

Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters (CAS 68440-06-2) is characterized by a low water solubility (16 ± 7 µg/L at 20 °C, pH 6.3), high log Kow (> 10) and high molecular weight (789.34 g/mol). Based on the physico/chemical properties such as low water solubility and high potential for adsorption a reduced availability in water is expected. The high molecular weight of the substance significantly reduces the absorption due to steric hindrance to cross biological membranes. It can be concluded that the bioaccumulation potential of Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters is negligible. BCF/BAF values estimated by QSAR (BCFBAF v3.01) also support this assumption (BCF values all well below 2000 L/kg). For a detailed overview on bioaccumulation please refer to IUCLID section 5.3.1.

Conclusion

Due to its high potential for adsorption to sewage sludge 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 the substance will mainly partition to the sediment particles due to the low water solubility and high adsorption potential. Thus, the substance will be bioavailable to sediment organisms mainly via feed and contact with suspended organic particles. Moreover, thehigh molecular weight of the substance significantly reduces the absorption due to steric hindrance to cross biological membranes.The supporting BCF/BAF values estimated with the BCFBAF v3.01 program, Arnot-Gobas model including biotransformation, also indicate that this substance will not be bioaccumulative (all well below 2000). Furthermore, all available aquatic toxicity data show that no effects occur up to the limit of water solubility. Therefore, Fatty acids, C18-unsatd., dimers, hydrogenated, 2-ethylhexyl esters is unlikely to pose a risk for sediment organisms and testing is thus omitted.

A detailed reference list is provided within CSR.