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Environmental fate & pathways

Endpoint summary

Administrative data

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Additional information

There is only limited data available for the environmental fate of the target substance fatty acids, C14-22, C16-24-alkyl esters (CAS 92797-30-3). Thus, a read-across approach was followed to compile relevant data from structurally and chemically related substances in order to fulfill the standard information requirements laid down in Annex XI, 1.5 of the REACh Regulation (EC) No 1907/2006. According to Article 13 (1) of the 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.” In 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 physico-chemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity.

The target substance fatty acids, C14-22, C16-24-alkyl esters (CAS 92797-30-3) is a long-chain aliphatic ester and a UVCB composed of three main constituents with carbon chain lengths of 38 and 40 formed through the reaction of C20 and C22 fatty acids with C16 and C18 fatty alcohols (C22 acid/C16 alcohol, C20 acid/C18 alcohol, and C22 acid/C18 alcohol). The endpoint for biodegradation was covered by the two source substances docosyl docosanoate (CAS 17671-27-1) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3). Furthermore, QSAR calculations were conducted for the estimation of biodegradation (VEGA v1.1.3, Ready biodegradability model v1.0.9) and adsorption/desorption (EPI Suite v4.11, KOCWIN v2.00).

The source substance docosyl docosanoate (CAS 17671-27-1) is a UVCB consisting of even numbered esters of carbon chain lengths 38, 40 and 44, derived from C20 – C22 fatty acids and C18 – C22 fatty alcohols. The source substance 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) is a UVCB composed of differently branched C38 esters of isostearic acid (C18) and 2-octyldodecanol (C18). Thus, the source substances are of similar chain lengths as the target substance and are therefore considered suitable representatives for the assessment of the ready biodegradability of the target substance. The carbon chain length is a critical factor for biodegradability and larger molecules are considered worst-case for the prediction of the biodegradability of a substance. Based on the high degree of similarity between the structural and physico-chemical properties of the target and source substances, the target substance is expected to have a similar environmental fate profile as the selected source substances. A detailed read-across justification is provided in IUCLID section 13 of the technical dossier.

The target substance fatty acids, C14-22, C16-24-alkyl esters (CAS 92797-30-3) is characterized by low water solubility (< 2.5 µg/L, 20 °C, pH 6.3, OECD 105), a high estimated log Kow (> 10.0, Vega v1.1.3, AlogP v1.0.0, Meylan/Kowwin v1.1.4, MlogP v1.0.0) and a high estimated log Koc (> 5.0, EPI Suite v4.11, KOCWIN v2.00), indicating lipophilicity and a potential for adsorption to soil and sediment particles. The substance has a low estimated vapor pressure (< 0.0001 Pa, 20 °C, SPARC v4.6) and experimental results from a standard biodegradation study with the closely related source substances docosyl docosanoate (CAS 17671-27-1) and 2-octyldodecyl isooctadecanoate (CAS 93803-87-3) indicate that the target substance can be expected to be readily biodegradable (68 – 71.7% in 29 d, OECD 301 B). Thus, abiotic degradation via hydrolysis and evaporation into the atmospheric compartment are presumably not relevant removal pathways.

Due to the ready biodegradability and high potential for adsorption, the substance can be effectively removed in conventional sewage treatment plants (STPs) by biodegradation and by sorption to biomass. Therefore, only negligible concentrations of the substance are likely to be released into the environment through conventional STPs, if at all and whatever fraction is released will undergo extensive biodegradation or sorption to organic matter. Consequently, the bioavailability of the substance in the water column will be rapidly reduced and the relevant route of uptake by aquatic organisms is expected to predominantly occur by ingestion of particle bound substance. However, based on the physico-chemical properties (i.e. high sorption), its bioavailability to sediment organisms is presumably also low.