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Long-term toxicity to aquatic invertebrates

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Description of key information

21 d NOEC: ≥4 mg/l nominal concentration, reproduction of Daphnia magna.

21 d NOEC: ≥0.127 mg/l geometric mean measured concentration of tris(1-methylethyl)silanol, reproduction of Daphnia magna.

21 d NOEC: ≥0.119 mg/l geometric mean measured concentration of acrylic acid, reproduction of Daphnia magna.

Key value for chemical safety assessment

Additional information

Tri(isopropyl)silyl acrylate hydrolyses very rapidly in solution. The silanol hydrolysis product has low solubility in water and relatively high log Kow. The limiting concentration in water is low due to expected tendency to dimerise in solution. Some aquatic toxicity is to be expected and it is possible that short term testing may not have fully captured the potential for chronic effects.

A long-term toxicity to aquatic invertebrates has therefore been conducted using a pre-hydrolysed sample of the registration substance. The test was conducted in compliance with OECD guideline 211. The results are as follows:

No adverse effects were observed at the nominal loading limit concentration of 4 mg/l after 21 days. At this loading, the geometric mean measured concentration of the silanol hydrolysis product tris(1-methylethyl)silanol was 0.127 mg/l, and the geometric mean measured concentration of the non-silanol hydrolysis product acrylic acid was 0.119 mg/l.

A 21 day NOEC value of ≥4 mg/l (highest concentration tested) has been determined for the effects of the test substance on reproduction of Daphnia magna, based on nominal concentrations of the registration substance tri(isopropyl)silyl acrylate. This loading corresponds with geometric mean measured concentrations of parent substance of 0.166 mg/l calculated from the degradation product tris(1-methylethyl)silanol with the molar factor 1.310, and 0.377 mg/l calculated from the degradation product acrylic acid with the molar factor 3.170.

A 21 day geometric mean NOEC value of ≥0.127 mg/l (highest concentration tested) has been determined for the effects of the silanol hydrolysis product of the test substance tris(1-methylethyl)silanol, on reproduction of Daphnia magna.

A 21 day geometric mean NOEC value of ≥0.119 mg/l (highest concentration tested) has been determined for the effects of the non-silanol hydrolysis product of the test substance acrylic acid, on reproduction of Daphnia magna.

A 21 day NOEC(maternal toxicity) of 7 mg/l (measured) for the non-silicon containing hydrolysis product, acrylic acid (CAS 79-10-7) from a semi-static test is reported in the EU Risk Assessment Report (EC, 2002). The 21 day NOEC(reproductive effects) was 12 mg/l (measured) in the same test.

Reference:

EC, 2002. European Union Risk Assessment Report acrylic acid CAS No: 79-10-7 EINECS No: 201-177-9 Series: 1st Priority List Volume: 28, European Commission – Joint Research Centre Institute for Health and Consumer Protection European Chemicals Bureau (ECB).