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Reliable short-term toxicity tests results are available for freshwater fish (Oncorhynchus mykiss), invertebrates (Daphnia magna) and algae (Pseudokirchneriella subcapitata) for 3-(trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate (CAS 163802-53-7).

The relevant short-term values are:

Fish: LC50 (96 h): 23 mg/l; NOEC: 6.5 mg/l or LC50 19 mg/l when expressed in terms of concentration of the hydrolysis product 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

Daphnia: EC50 (48 h): >26 mg/l; NOEC: 12 mg/l or EC50 >22 mg/l when expressed in terms of concentration of the hydrolysis product 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

If expressed in terms of nominal concentration, the EC50value is >85 mg/l as 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

Algae: EC50 (72 h): >90 mg/l; NOEC: 90 mg/l or EC50 >76 mg/l and NOEC 76 mg/l mg/l when expressed in terms of concentration of the hydrolysis product 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

If expressed in terms of nominal concentration, the EC50 value is >85 mg/l as 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

A reliable long-term test for effects of 3-(trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate (CAS 163802-53-7) to Daphnia magna is available.

The relevant long-term values are:

EC10 (21-d): 9.4 mg/l based on survival

EC10 (21-d): 2.3 mg/l based on reproduction or EC10 1.9 mg/l when expressed in terms of concentration of the hydrolysis product 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

If expressed in terms of nominal concentration, the EC10 value lies between 5.3 mg/l to 11 mg/l as 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate.

EC10 (21 -d): 7.6 mg/l based on length

NOEC (21 -d): 6.9 mg/l

The toxicity of the substance to microorganisms was assessed based on a toxicity control test in a ready biodegradation study: A 28 day NOEC value of 20 mg/l (nominal) were determined in a reliable study, for effects on growth inhibition.

The rapid hydrolysis of 3-(trimethoxysilyl)propyl-(2E,4E)-hexa-2,4-dienoate (CAS 163802-53-7) (half-life 4.7 h at pH 7, 25 °C) means it is likely that the test organisms in the flow-through fish test were exposed primarily to the parent substance, as the pH remained neutral. The pH during the short-term and long-term Daphnia tests were around pH 8, or slightly greater. At this pH, hydrolysis half-life is expected to be approximately 5-10 time faster than at pH 7, therefore the Daphnia are likely to have been predominantly exposed to the hydrolysis products, 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate and methanol. During the algae test it is likely that the organisms were predominantly exposed to the hydrolysis products 3-(trihydroxysilyl)propyl-(2E,4E)-2,4-hexadienoate and methanol.

Refer to the Ecotoxicological Information section for further discussion of the approach to chemical safety assessment.

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