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There are no reliable aquatic toxicity data available for 1,2-bis[dichloro(methyl)silyl]ethane (CAS 3353-69-3), therefore good quality data for the structurally-related substance 1,6-bis(trimethoxysilyl)hexane (CAS 87135-01-1), have been read across.

 

The rapid hydrolysis of 1,6-bis(trimethoxysilyl)hexane (CAS 87135-01-1) (half-life 5.2 h at pH 7 and 25°C) means it is likely that the test organisms in each test were exposed to a mixture of the test substance and the hydrolysis products only at the beginning of the test, and after this it is likely to be predominantly the hydrolysis products, 1,6-bis(trihydroxysilyl)hexane and methanol. The observations in the studies with fish, invertebrates and algae are attributed to the presence of 1,6-bis(trihydroxysilyl)hexane in the test system.

Reliable short-term toxicity tests results are available for freshwater fish (Oncorhynchus mykiss) for 1,6-bis(trimethoxysilyl)hexane (CAS 87135-01-1). The relevant short-term values are:

Fish: LC50 (96 h): >74 mg/l (expressed in terms of concentration of the hydrolysis product,1,6-bis(trihydroxysilyl)hexane)

Invertebrates: EC50 (48 h): >74 mg/l (expressed in terms of concentration of the hydrolysis product,1,6-bis(trihydroxysilyl)hexane)

Algae: ErC50 (72 h): >74 mg/l (expressed in terms of concentration of the hydrolysis product,1,6-bis(trihydroxysilyl)hexane)

 

An activated sludge respiration inhibition study is available reporting a 3 hour EC50 value of >742 mg/l and NOEC value of ≥ 742 mg/l (nominal) (expressed in terms of concentration of the hydrolysis product,1,6-bis(trihydroxysilyl)hexane).

Toxicity to algae data have also been read-across from 4,4,7,7-tetraethoxy-3,8-dioxa-4,7-disiladecane (CAS 16068-37-3) and used as supporting data:

72 h ErC50 >100 mg/l and ErC10 92.9 mg/l (exposure to a mixture of parent substance and hydrolysis product).

 

Refer to IUCLID Section 6 endpoint summary (CSR Section 7.0) for further discussion of the approach to chemical safety assessment and justification for read across.

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