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Environmental fate & pathways

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There is only limited data available on the environmental fate of 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8). Therefore, a read-across approach was pursued to compile relevant data from structurally and chemically related substances in order to fulfill the standard information requirements laid down in Annex VIII, 1.5, of the REACH Regulation (EC) No 1907/2006. According to Article 13 (1) of this regulation, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” With regard to the general rules for grouping of substances and the read-across approach, the regulation specifies (Annex XI, Item 1.5) that substances may be predicted as similar provided that their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

Based on the high degree of structural similarity as well as similar physico-chemical properties of the target and source substance, the target substance is expected to have a similar environmental fate profile. A detailed analogue approach justification is provided in IUCLID section 13 of the technical dossier.

The target substance 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8) is characterized by high molecular weight (> 500 g/mol), low water solubility (< 0.05 mg/L), a low estimated vapor pressure (< 0.0001 Pa), a high estimated log Kow (> 10, KOWWIN v1.68) and a high estimated log Koc (> 5, KOCWIN v2.00, MCI). Experimental results from a standard biodegradation study with the closely related source substance Isohexadecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 97338-28-8) indicate that the target substance can be expected to be readily biodegradable (86.0% in 28 d, OECD 301 F). Thus, abiotic degradation via hydrolysis and evaporation into the atmospheric compartment are presumably not relevant removal pathways.

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, 2017). Due to ready biodegradability and high potential for adsorption, the substance can be effectively removed in conventional STPs by biodegradation and sorption to biomass. Furthermore, the Guidance also 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 come into contact with activated sludge microorganisms. Therefore, only negligible concentrations of the substance are likely to be released (if at all) into the environment through conventional STPs. Whatever fraction is released into the aquatic environment will undergo extensive biodegradation and will preferentially distribute into the sediment compartment through sorption to organic matter, leading to a rapid reduction of the bioavailability of the substance in the water column. Thus, the relevant route of uptake in aquatic organisms is expected to predominantly occur by ingestion of particle bound substance, but the bioavailability of the substance is presumably very low based on the physico-chemical properties of the substance. Experimental data for bioaccumulation is not available for the target substance 2-octyldodecyl 12-[(1-oxooctadecyl)oxy]octadecanoate (CAS 90052-75-8) and the estimated log Kow is high (> 10), which may be indicative of a potential for bioaccumulation. However, based on current knowledge, a calculated log Kow of 10 or above is taken as an indicator of reduced bioconcentration, as stated in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7c: Endpoint specific guidance (ECHA, 2017).

In case of absorption by aquatic organisms, long chain aliphatic esters are expected to be enzymatically hydrolyzed by carboxylesterases, yielding the corresponding alcohol and fatty acid. Both hydrolysis products are expected to be satisfactorily metabolized in aquatic organisms. The metabolization 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 summary, the substance is expected to be rapidly hydrolyzed to the respective fatty acid and fatty alcohol and the potential for bioaccumulation of both the substance as well as its metabolites is low.

Overall, the available information on environmental behavior and metabolism, in combination with QSAR estimates, provide enough information to cover the data requirements set out in Regulation (EC) No 1907/2006, Annex VIII.