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Biodegradation in water: screening tests

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Description of key information

Biodegradation in water: screening tests: 2.2% in 28 days (O2 consumption, OECD 301F), based on read-across from a structurally-related substance. 

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

There are no reliable ready biodegradation data available for 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (CAS 3390-61-2), therefore good quality data for the structurally-related substance, 3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane (CAS No. 60111-47-9), have been read across.

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (CAS 3390-61-2) and 3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane (CAS No. 60111-47-9) are structurally-similar substances, both are siloxanes with phenyl functionality. The target substance 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (CAS 3390-61-2) is a linear siloxane containing three Si atoms linked by oxygen. The terminal silicon atoms are each substituted with one methyl group and two phenyl groups, and the central silicon atom is substituted with one methyl and one phenyl group. The source substance 3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane (CAS No. 60111-47-9) is a branched structure of four Si atoms,the longest siloxane chain contains three silicon atoms and two oxygen atoms, with a Si-O branch on the central silicon atom in the chain. The terminal silicon atoms are each substituted with two methyl and one vinyl group, whilst the central silicon atom has one phenyl group attached.

 

1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (CAS 3390-61-2) and 3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane (CAS No. 60111-47-9) are within the Siloxane Category of substances within which, in general, there is no evidence of any significant biodegradation.

The table below presents ready biodegradation data for substances within the Siloxane Category.

It is therefore considered valid to read-across the results for 3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane (CAS No. 60111-47-9)

to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2014i) attached in Section 13.

Table: Ready biodegradation data for substances within the Siloxane Category

CAS

Name

Readily biodegradable? Yes/no

Result: Biodegradation after 28 days (%)

Guideline

Test type

Reliability

107-46-0

Hexamethyldisiloxane

No

2%

OECD 301C

BOD

1c

107-51-7

Octamethyltrisiloxane

No

-3.70%

OECD 310

CO2

1a

540-97-6

Dodecamethylcyclohexasiloxane

No

4.5%

OECD 310

CO2

1a

541-02-6

Decamethylcyclopentasiloxane

No

0.14%

OECD 310

CO2

1a

541-05-9

Hexamethylcyclotrisiloxane

No

0.06%

OECD 310

CO2

1a

556-67-2

Octamethylcyclotetrasiloxane

No

3.70%

OECD 310

CO2

1a

1873-88-7

1,1,1,3,5,5,5-heptamethyltrisiloxane

No

0%

OECD 310/ ISO Guideline No 14593

CO2

1a

2627-95-4

1,1,3,3-tetramethyl-1,3-divinyldisiloxane

No

0%

OECD 301D

BOD

1a

17928-28-8

1,1,1,3,5,5,5-heptamethyl- 3-[(trimethylsilyl)oxy] trisiloxane

No

0%

OECD 301F

BOD

1a

17955-88-3

1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane

No

10 – 32 % after 25 d

OECD 301B

CO2

 1a

60111-47-9

3-[(dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane

No

2.20%

OECD 301F

BOD

1a

69304-37-6

1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane

No

0% (BOD); 100% (GC)

OECD 301C

BOD

1a

70940-00-0

1,1,7,7,-Tetramethyl-3,3,5,5,-Tetraphenyl-Tetrasiloxane

No

9.7 and 9.9%

OECD 301B

CO2

 1a

180073-46-5

Pentasiloxane, 1,1,9,9-tetramethyl-3,3,5,5,7,7-hexaphenyl-

No

5.2 and 4.4%

OECD 301B

CO2

 1a

352230-22-9

Siloxanes and Silicones, di-Ph, Ph (trimethylsilyl)oxy

No

0%

OECD 301F

BOD

1a

3-[(Dimethylvinylsilyl)oxy]-1,1,5,5-tetramethyl-3-phenyl-1,5-divinyltrisiloxane attained 2.2% biodegradation in 28 days (O2 consumption).

Reference: PFA 2014i. Peter Fisk Associates. Siloxane analogue report. PFA.300.005.008.R1.