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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Biodegradation in water: screening tests: 98% degradation (DOC removal) in 28 days (EU C.4-A), read-across from an analogous substance. The silanol hydrolysis product silicic acid is inorganic and so is not biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

There are no reliable ready biodegradation data available for tetramethyl orthosilicate, therefore good quality data for the analogous substance, tetraethyl orthosilicate (CAS 78-10-4), have been read across. Both substances share the same silanol hydrolysis product, (poly)silicic acid; the other hydrolysis products being methanol and ethanol, respectively, both of which are readily biodegradable.

Both tetramethyl orthosilicate and tetraethylorthosilicate are part of an analogue group of substances within which, in general,the substances arereadily biodegradable. All carbons in the structure are associated with alkoxy/acetoxy groups, which hydrolyse and biodegrade within the timescale of the ready biodegradability tests.

 

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, 2013g) attached in Section 13 of the IUCLID 5 dossier.

Tetraethyl orthosilicate attained 98% biodegradation in 28 days. This biodegradation is attributable to the biodegradation of the ethanol hydrolysis product, which is readily biodegradable. 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).

Biodegradation is not relevant for the inorganic silanol hydrolysis product, (poly)silicic acid; it is the water soluble form of inorganic silicon and will enter the natural biogeochemical cycle for silicon.