Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

No data are available for the submission substance, trimethoxy(octyl)silane (CAS 3069-40-7). However, reliable test data are available for the read-across substances trichloro(2,4,4-trimethylpentyl)silane (CAS 18379-25-4) and trichloro(phenyl)silane (CAS 98-13-5).  Both substances rapidly hydrolyse to substances that are analogous to the silanol hydrolysis product of the registered substance (see the ecotoxicological discussion). Reliable short-term toxicity test results are available for freshwater fish (Oncorhynchus mykiss) and algae (Pseudokirchneriella subcapitata). The relevant short-term values are:

Fish: (96 h) LC50 >100 mg/L, read across from trichloro(2,4,4-trimethylpentyl)silane (CAS 18379-25-4). This is equivalent to >78 mg/L when expressed in terms of the silanol hydrolysis product (2,4,4-trimethylpentyl)silanetriol.

Algae: (72 h) EC50 >100 mg/L and NOEC ≥100 mg/L, read across from trichloro(phenyl)silane (CAS 98-13-5). These are equivalent to >74 mg/L and ≥74 mg/L, respectively, when expressed in terms of the silanol hydrolysis product phenylsilanetriol.

No short-term data are available for toxicity to invertebrates. However, a 21-day NOEC of 32 mg/L has been determined for the effects of trichloro(2,4,4-trimethylpentyl)silane (CAS 18379-25-4) on mortality and reproduction of Daphnia magna. This is equivalent to 25 mg/L when expressed in terms of the silanol hydrolysis product (2,4,4-trimethylpentyl)silanetriol.

 

The very rapid hydrolysis of trichloro(2,4,4-trimethylpentyl)silane (CAS 18379-25-4) (half-life <1 minute at pH 7 and 25°C) means it is likely that the test organisms in each test were exposed primarily to the hydrolysis products, (2,4,4-trimethylpentyl)silanetriol and hydrochloric acid.

 

The very rapid hydrolysis of trichloro(phenyl)silane (CAS 98-13-5) (half-life <1 minute at pH 7 and 25°C) means it is likely that the test organisms in each test were exposed primarily to the hydrolysis products, phenylsilanetriol and hydrochloric acid.

 

An activated sludge respiration inhibition 3 hour EC50 value of >1000 mg/L and NOEC value of ≥1000 mg/L (loading rate) were determined in a reliable study, read-across from triethoxy(octyl)silane (CAS 2943-75-1).

 

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.