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Environmental fate & pathways

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Reaction mass of N-(1-oxooctadecyl)sarcosine and N-hexadecanoyl-N-methylglycine (EC 947-850-7) is an ionisable multi-constituent substance characterized by a water solubility of 2.86 mg/L (OECD 105), a vapour pressure of 7.10E-05 Pa (20 °C, OECD 104) and ready biodegradability (85.2% in 28 d, OECD 301 B, activated sludge). Since there is only limited experimental data available for the environmental fate of the substance, QSAR calculations were performed to estimate the dissociation constant (pKa), the log Koc values and the log D values of the two main constituents of the substance, i.e. Stearoyl sarcosine (CAS 142-48-3) and Palmitoyl sarcosine (CAS 2421-33-2).

The low vapour pressure indicates that the substance is not volatile and that evaporation to air and subsequent transport through the atmosphere to other environmental compartments is not likely.

The calculated pka values of both molecules is 3.96 (SPARC v4.6), indicating that the ionized, charged anionic forms will predominate at environmentally relevant pH values in the range of 4 to 9. The SPARC model predicts that the acid form constitutes 47.4% at pH 4, 0.1% at pH 7 and 0% at pH 9, at which point the molecules completely dissociate into the corresponding anionic form.

The estimated log Koc (ChemProp v6.5, Franco, Fu & Trapp for ionizable substances) is 4.08 at pH 4, 2.31 at pH 7, and 2.17 at pH 9, indicating a moderate potential for adsorption to particles present in soil and sediment in neutral to basic environments and a moderate potential for adsorption in more acidic environments. Thus, based on the water solubility and predicted log Koc values, only low concentrations of the substance are expected in water with moderate mobility at environmentally relevant pH values of around 7.

Reaction mass of N-(1-oxooctadecyl)sarcosine and N-hexadecanoyl-N-methylglycine (EC 947-850-7) has predicted log D values of 2.40 to 3.40 at pH 7 and 1.53 to 2.54 at pH 9 (SPARC v4.6), indicating a moderate to low lipophilicity at environmentally relevant pH ranges of 7 and above. The predicted BCF values provide evidence that the potential for bioaccumulation in aquatic organisms is likely low. The predicted BCF values range from 10 to 421.7 L/kg 10 L/kg wet-wt (BCFBAF v3.01, VEGA, CAESAR v2.1.14, Meylan v1.0.3 and KNN/RA v1.10) and are thus well below the threshold value of 2000 L/kg for bioaccumulative substances, as laid down by the REACH regulation (EC) No 1907/2006, section 1 of Annex XIII. In addition, toxicokinetic considerations with regard to absorption, distribution, metabolisation and excretion of the substance provide further evidence for a low bioaccumulation potential.

Moreover, the substance is readily biodegradable based on a standard biodegradation study with a structurally and chemically closely related source substance (85.2% in 28 d, OECD 301 B, activated sludge). Consequently, abiotic degradation via hydrolysis is not a relevant degradation pathway. 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 (ECHA, 2016). Hence, chronic exposure, bioavailability, and uptake by aquatic organisms are expected to be low due to low solubility on the one hand and minimal release and persistence due to ready biodegradability on the other hand.