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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

Toxicity to microorganisms: 3hr EC50 >100 mg/l (activated sludge respiration inhibition, OECD 209), read-across from an analogue substance.

Key value for chemical safety assessment

Additional information

There are no reliable microorganism toxicity data available for tetramethyl orthosilicate, therefore good quality data for the analogue substance, tetraethyl orthosilicate (CAS 78 -10 -4), have been read across. Both substances share the same hydrolysis product, silicic acid

; the other hydrolysis products being methanol and ethanol, respectively. Methanol and ethanol do not have adverse effects on microorganisms.

Both tetramethyl orthosilicate and tetraethyl orthosilicate are within an analogue group of substances that exhibit no evidence of significant toxicity to microorganisms

It is therefore considered valid to read-across the results for tetraethyl orthosilicate to fill the data gap for the registered substance.Additional information is given in a supporting report (PFA, 2013j) attached in Section 13 of the IUCLID 5 dossier.

A 3hr EC50value of >100 mg/l (nominal) was determined for tetraethyl orthosilicate.

The study is considered to be reliability 1 (reliable without restrictions); the read across of the result is considered to be reliability 2 (reliable with restrictions).

The hydrolysis rate for tetraethyl orthosilicate is 4.4 hours at pH7 and 25°C, and so it would be hydrolysed to a lesser extent than tetramethyl orthosilicate in the timescale of the test. Therefore, microorganisms toxicity data for Silicic acid (H4SiO4), tetraethyl ester, hydrolyzed (CAS 68412-37-3), which is a member of the same analogue group, has been used as supporting data for the read-across. Microorganism toxicity data from a non-standard oxygen consumption study with Pseudomonas putida is available for Silicic acid (H4SiO4), tetraethyl ester, hydrolyzed. The test procedure was in accordance with generally accepted scientific standards and described in sufficient detail and in compliance with GLP, with acceptable restrictions. The restrictions were that a reference substance was not used to check the sensitivity of the microorganisms, and an emulsifier was used which could have affected the results.