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Environmental fate & pathways

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3-(Triethoxysilyl)-N-[3-(triethoxysilyl)propyl]-1-propanamine (CAS No. 13497-18-2) has an estimated water solubility of 23 mg/L at 20-25°C (QSAR) and a predicted log Kow of 3.1 (QSAR). Furthermore, it is characterized by a low vapour pressure (1.8E-04 Pa at 25 °C, QSAR), indicating low volatility. Therefore, photodegradation is not an important degradation pathway. Nevertheless, if emitted into the air, it will rapidly photodegrade (estimated half-life for indirect photodegradation: 3.04 h, OH-radicals).

The substance is not readily biodegradable. However, once in the water phase or when exposed to humid environments, the substance hydrolyses rapidly (DT50 = 11.9 h at pH 7 and 20 °C) which contributes significantly to its degradation in the aquatic environment. The resulting transformation products are the silanol hydrolysis product 3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine and the alcohol hydrolysis product ethanol (CAS No. 64-17-5).

The ECHA guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016). The ECHA guidance R.16 also suggests that in cases where the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity."

Thus, the environmental fate assessment in this dossier is based on the hydrolysis products3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine and ethanol.


Silanol hydrolysis product 3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine

The silanol hydrolysis product 3-(trihydroxysilyl)-N-[3-(hydroxysilyl)propyl]-1-propanamine is characterized by a high, estimated water solubility of 1.0E06 mg/L (QSAR). There is no evidence of any significant biodegradation. However, its potential for bioaccumulation and its affinity to soil and sediment is low based on its low log Kow (-4.0, QSAR) and its low, estimated log Koc (0.5, QSAR), respectively.


Alcohol hydrolysis product ethanol

The alcohol hydrolysis product ethanol is well characterized in the public domain. In the environment, it is expected to distribute into air (57%), water (34%) and soil (9%). It is fully water miscible at ambient temperatures and is characterized by a low partition coefficient (log Kow = -0.31) and a low adsorption coefficient (Koc = 1) and is considered to have a low overall environmental hazard profile (OECD SIDS, 2004).



OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.