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EC number: 229-929-1 | CAS number: 6843-66-9
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Dimethoxydiphenylsilane (CAS 6843-66-9) ist not readily biodegradable in water (1 % in 28 d) based on read across from CAS 98-13-5
Key value for chemical safety assessment
Additional information
No reliable ready biodegradation data are available for Dimethoxydiphenylsilane (CAS 6843-66-9), therefore good quality data from Trichloro(phenyl)silane (CAS 98-13-5), have been read across. Both substances hydrolyse to the structurally-related silanol hydrolysis products, Diphenylsilanediol and Phenylsilanetriol, respectively. Both substances are expected to hydrolyse within the timescale of a ready biodegradation test.
Both Dimethoxydiphenylsilane (CAS 6843 -66 -9) and Trichloro(phenyl)silane are within a wider analogue group. 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 analogue group for the ready biodegradability endpoint consists of a number of sub-classes of substances. Read-across is predominantly carried out between substances with the same sub-class. Table 4.1.4 depicts the available data on ready biodegradability within the sub-class (III-22) of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc. where the Si part, resulting after hydrolysis, is of low-biological reactivity. Both Dimethoxydiphenylsilane and Trichlorophenylsilane are members of this sub-class. It is therefore considered appropriate to read-across the results from Trichloro(phenyl)silane to fill the data gap of the target substance. Additional information is given in a supporting report (PFA, 2016) 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 |
Trichloro(phenyl)silane |
No |
1% |
OECD 310 |
1a |
None1 |
3-(3-Chloro-4-fluorophenyl)propyldimethylchlorosilane |
No |
8% |
OECD 301B |
1a |
The available study (2009) investigating the biodegradation of the analogue substance Trichloro(phenyl)silane (CAS 98-13-5) was conducted according to OECD guidance 310.The inoculum (activated sludge from a sewage treatment plant) was exposed for 60 d to 740 mg test item/L and biodegradation was determined based on CO2 evolution. No biodegradation was observed after 60 daysand therefore, the substance is not considered as readily biodegradable.
Based on the results of the analogue substance, Dimethoxydiphenylsilane (CAS 6843-66-9) is not considered to be readily biodegradable.
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