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There are no reliable aquatic toxicity data available for 3-[3,3,3-trimethyl-1,1-bis[(trimethylsilyl)oxy]disiloxanyl]propyl methacrylate; CAS No. 17096-07-0, therefore a combination of QSAR prediction for the substance and good quality experimental data for structurally-related substances have been used to fulfil the data requirements for registration.

 

3-[3,3,3-Trimethyl-1,1-bis[(trimethylsilyl)oxy]disiloxanyl]propyl methacrylate undergoes hydrolysis in water (half-lives of 3.6 h at pH 4, 2.3 h at pH 5, 631 h at pH 7 and 5.3 h at pH 9 and 20-25°C are predicted by QSAR. The low solubility (5.8E-05 mg/L at 20°C (QSAR)) could limit the rate of the reaction at higher loadings in water. The hydrolysis products under dilute conditions in solution are 3-(trihydroxysilyl)propyl methacrylate and trimethylsilanol, Aquatic ecotoxicity data are available for 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0), which also undergoes hydrolysis in water to form the same silanol hydrolysis product as the registration substance. Aquatic ecotoxicity data are also available for trimethylsilanol (CAS No. 1066-40-6). These are included as read across data for completeness, although in view of the slow hydrolysis rate under neutral conditions, the chemical safety assessment for the environment focuses on the parent substance.

 

Reliable predicted short-term toxicity for invertebrates (Daphnia magna) and green algae are available. The relevant short-term values are:

Daphnia: EC50 (48 h): >limit of solubility in water

Algae: EC50 (72 h): >limit of solubility in water

In view of the physicochemical properties of the registration substance, the potential for long-term effects has also been considered qualitatively. Long-term aquatic effects would not be expected to be expressed below the limit of solubility, based on the very high value of log Kow.