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Biodegradation in water: screening tests

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Description of key information

Biodegradation in water: screening tests: 20% biodegradation in 28 days (OECD 301F)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The substance attained 20%degradation in 28 days in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP. 4,4,13,13-Tetraethoxy-3,14-dioxa-8,9-dithia-4,13-disilahexadecane (S2) hydrolyses within the timescale of the ready biodegradation study to (3-{[3-(trihydroxysilyl)propyl]disulfanyl}propyl)silanetriol and ethanol. The biodegradation observed in the study is attributable to the biodegradation of the ethanol hydrolysis product.

Ethanol is readily biodegradable (OECD, 2004) and no significant biodegradation is expected for the silanol hydrolysis product.

The biodegradation rate is slightly lower than expected based on consideration of the chemical structure (biodegradable ethanol/ethoxy groups accounting for nearly 60% of the parent structure by weight). The toxicity control showed a slight bacterial inhibition (9.3%), which may explain the lower rate. Also, the insolubility of the test substance may have had an effect.

A second high reliability study is available which gave a similar result to the key study, 10 -12% in 28d. It was not chosen as the key study because a less standard method was used.


OECD (2004): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.