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Description of key information

Based on all the available information, toxicity to sediment organisms is not expected to be of concern and further testing is not proposed.

Key value for chemical safety assessment

Additional information

 No experimental data is available for the assessment of the toxicity of Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) to sediment organisms. Only negligible releases into surface water from sewage treatment plants (STPs) are expected due to: a) the ready biodegradability and b) the high adsorption properties 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 acutely toxic to aquatic organisms up to the limit of water solubility. In addition, the available data indicates that the substance is not bioaccumulative (log Kow > 10, BCF = 0.893 L/kg). Based on all the available information, toxicity to sediment organisms is not expected to be of concern.

 Intrinsic properties and fate

Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) is readily biodegradable. According to the Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2017), readily biodegradable substances can be expected to undergo rapid and ultimate degradation in most environments, including biological STPs. Therefore, only low concentrations of this substance are expected to be released into the environment, if at all.

Furthermore, Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) has an estimated log Koc of > 5.0 and is poorly soluble in water (1.39 µg/L). The guidance on information requirements and chemical safety assessment, Chapter R7.b (ECHA, 2016) 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. Thus, discharge into the aqueous/sediment compartment is likely negligible and chronic exposure of sediment organisms is improbable.

Aquatic ecotoxicity data

According to the available short-term toxicity data for fish, aquatic invertebrates and algae, it can be expected that Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) will not cause acute toxicity in aquatic organisms up to the limit of water solubility (< 1.39 µg/L). Chronic effects on the reproduction of Daphnia magna were observed in a long-term toxicity test. However, the Chemical Safety Assessment does not indicate a need for further investigations. According to Annex XI, Section 3 of Regulation (EC) No 1907/2006 toxicity testing with sediment organisms is deemed not necessary. The release rates to wastewater during mthe life cycle of the substance are negligible. The environmental exposure assessment for the substance indicates no risk for the aquatic and sediment compartment (all RCR< 1; please refer to Chapter 9 and 10 of the Chemical Safety Report for detailed information). 

Metabolism/Bioaccumulation

After absorption by aquatic organisms, Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) is expected to be enzymatically hydrolyzed by carboxylesterases into the corresponding free fatty acid and alcohol components. The estimated BCF of 0.893 L/kg obtained by QSAR calculations using BCFBAF v3.01 support the expected rapid biotransformation of the substance. The metabolism of the hydrolysis products is well established and not of concern in terms of bioaccumulation (for further information, see chapter 5.3 of the technical dossier).

In consideration of all the available information, it is concluded that the potential for bioaccumulation is low.

 

Conclusion

Due to ready biodegradability and high adsorption, only negligible concentrations of the substance are expected to be discharged into environmental water bodies, if at all. Whatever fraction is released is expected to rapidly degrade or adsorb to particles of sediment and soil where sediment organisms are potentially exposed via feed and contact with suspended organic particles. However, based on the physico-chemical properties of the substance (i.e. strong binding behaviour), bioavailability is expected to be low. If uptake should occur, extensive and fast biotransformation of the substance and its metabolites is expected by the action of carboxlesterases. The estimated log Kow and BCF values further support that bioaccumulation is not of concern. Furthermore in accordance with Annex IX, column 2 of Regulation (EC) No 1907/2006, toxicity testing with sediment organisms does not need to be conducted as the Chemical Safety Assessment does not indicate a need for further investigations. According to Annex XI, Section 3 of Regulation (EC) No 1907/2006 toxicity testing with sediment organisms is deemed not necessary. The release rates to wastewater during the life cycle of the substance are negligible. The environmental exposure assessment for the substance indicates no risk for the aquatic and sediment compartment (all RCR< 1; please refer to Chapter 9 and 10 of the Chemical Safety Report for detailed information).