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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

Aquatic bioaccumulation [parent substance]: not relevant due to very rapid hydrolysis

Aquatic bioaccumulation [silanol hydrolysis product]: BCF values of 10-22 and 11-35 at two different test concentrations

Key value for chemical safety assessment

Additional information

In contact with water, tri(isopropyl)silyl acrylate reacts very rapidly by read-across from structural analogue; (half-life of <<1 h at pH 7 and 25°C) to produce tris(1-methylethyl)silanol and acrylic acid. Therefore, requirements for testing of bioaccumulation from water for the substance are waived on the basis of instability in water.

A study of bioconcentration in fish (C. carpio) using the MITI standard method is available for 1,3-dihydroxy-1,1,3,3-tetraisopropyldisiloxane. 1,3-Dihydroxy-1,1,3,3-tetraisopropyldisiloxane has some structural features in common with tris(1-methylethyl)silanol (silanol features and isopropyl groups attached to silicon atoms) and has similar physicochemical properties (molecular weight 278.54 g/mol and 174.36 g/mol respectively, water solubility 310 mg/l and 60 mg/l respectively). The tested substance, 1,3-dihydroxy-1,1,3,3-tetraisopropyldisiloxane has a log Kow of 5.4, yet the bioconcentration factor was found to be very low (BCF values 10-22 and 11-35 at two different test concentrations).

Tris(1-methylethyl)silanol has a lower log Kow of 3.9 so would be expected to have a lower bioconcentration factor than that of 1,3-dihydroxy-1,1,3,3-tetraisopropyldisiloxane.

For these reasons, the read-across is considered to be acceptable and conservative. While the study does have some methodological deficiencies (use of dispersant; no definite confirmation of steady state; no depuration period) the result is taken as indicative of low potential for tris(1-methylethyl)silanol to bioconcentrate in fish.