Fatty acids, C16-18, stearyl esters

Endpoint summary

Additional information

There is only limited data available on the environmental fate of the target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5). Therefore, a read-across approach was pursued to compile relevant data from two structurally and chemically related source substance in order to fulfill the standard information requirements laid down in Annex VIII of REACH Regulation (EC) No 1907/2006. Read-across was conducted in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5.

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 selected source substances, the target substance is expected to exhibit a similar environmental fate profile as the selected source substances. A detailed analogue approach justification is provided in IUCLID section 13 of the technical dossier.

The target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5) is characterized by a molecular weight of 242.44 - 565 g/mole, low water solubility (< 0.507 mg/L, 20 °C, OECD 105), low vapour pressure (< 0.0001 Pa, 20 °C, SPARC v4.6) and a high estimated log Koc (> 5.0, KOCWIN v2.00). Experimental results from standard biodegradation studies with two closely related source substances indicate that the target substance is readily biodegradable according to guideline criteria (68.1 – 71.1% in 29 d, OECD 301 B; 90% in 28 d, ISO 10708). Abiotic degradation via hydrolysis and phototransformation in air is therefore not a relevant environmental fate pathway due ready biodegradability and due to low vapour pressure, respectively.

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 into the aquatic environment through conventional STPs, if at all. Whatever fraction is released 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 via ingestion of particle bound substance, but the bioavailability of the substance is presumably very low based on the physico-chemical properties of the substance (i.e. strong binding).

Experimental data for bioaccumulation is not available for the target substanceFatty acids, C16-18, stearyl esters (CAS 85536-04-5)and the estimated log Kow is high (> 10.0, SPARC v4.6), which may be indicative of a potential for bioaccumulation. However, the log Kow presumably overestimates the true bioaccumulation potential of a substance since it does not take into account the environmental fate and metabolization of substances in living organisms. Moreover, based on current knowledge, a log Kow of 10.0 or above is taken as an indicator of reduced bioconcentration, according to the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7c: Endpoint specific guidance (ECHA, 2017).

In summary,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 preferentially distribute into the sediment compartment where the bioavailability of the substance is presumably very low based on the physico-chemical properties of the substance (i.e. strong binding properties).

Moreover, the available information on environmental behavior, metabolism and bioaccumulation provide evidence that the overall potential for bioaccumulation of the target substance is low. In conclusion, the available information is considered sufficient to cover the data requirements set out in Regulation (EC) No 1907/2006, Annex VIII.