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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: 0 % in 28 days (OECD 310)

Key value for chemical safety assessment

Additional information

There are no reliable ready biodegradation data available for dichloro(diphenyl)silane, therefore good quality data for the structurally-related substance, trichloro(phenyl)silane (98-13-5), have been read across. Both substances hydrolyse to structurally-related silanol hydrolysis products, phenylsilanetriol and diphenylsilanediol. The other hydrolysis products of dichloro(diphenyl)silane (80-10-4) is hydrochloric acid and biodegradation is not relevant for hydrochloric acid as it is inorganic. Both substances are expected to hydrolyse within the timescale of a ready biodegradation test. Both dichloro(diphenyl)silane and trichloro(phenyl)silane are within a wider analogue group, than thedichloro(diphenyl)silaneanalogue group discussed in Section 1.4. Substances within this wider analogue group, in general, exhibit no evidence of any significant biodegradation once hydrolysis and subsequent biodegradation of alkoxy/acetoxy groups has been taken into account.

 

This wider analogue group for the ready biodegradability endpoint consists of a number of sub-classes of substances. However, read-across is carried out between substances with the same sub-class in most cases. Table 4.1.4 presents ready biodegradation data within the sub-class (III-22) of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where greater functional group(s) in side chain after any very rapid hydrolysis has been accounted for. Both trimethoxyphenylsilaneand trichloro(phenyl)silaneare members of this sub-class.

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

 

Table 4.1.4: Ready biodegradation data available for substances within the sub-class (III-22) of chemicals.

CAS

Name

Readily biodegradable? Yes/No

Result: Biodegradation after 28 days

Guideline

Reliability

000098-13-5

Hydroxytrimethylsilane

No

0%

OECD 310

1a

None1

Trimethyl(octadecyloxy)silane

No

8%

OECD 301B

1a

 

In the study 0% biodegradation was observed in 28 days. The study was conducted according to OECD guideline 310 and is considered reliable. This is selected as the key study.