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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), 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 tetradecamethylhexasiloxane (L6), therefore good quality data for the structurally-related substance, octamethyltrisiloxane (L3, CAS No. 107-51-7), have been read across. L6 and L3 are structurally-similar substances, both are linear siloxanes.

L3 is a linear siloxane chain with three silicon atoms, connected by two oxygen atoms. All silicon atoms present are fully substituted with methyl groups. L6 is a structurally related linear siloxane, with six silicon atoms and five oxygen atoms.

 

L3 and L6 are within an analogue group 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 analogue group (I-3) of siloxanes (alkyl, vinyl, aryl or hydrogen substituted).

It is therefore considered valid to read-across the results for L3 to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2015i) attached in Section 13.

Table 4.5: Ready biodegradation data for substances within the siloxane analogue group (I-3) of chemicals

CAS

Name

Readily biodegradable? Yes/no

Result: Biodegradation after 28 days (%)*

Guideline

Test type

Reliability

107-46-0

Hexamethyldisiloxane

No

2%

OECD 301C

BOD

1

107-51-7

Octamethyltrisiloxane

No

-3.70%

OECD 310

CO2

1

540-97-6

Dodecamethylcyclohexasiloxane

No

4.5%

OECD 310

CO2

1

541-02-6

Decamethylcyclopentasiloxane

No

0.14%

OECD 310

CO2

1

541-05-9

Hexamethylcyclotrisiloxane

No

0.06%

OECD 310

CO2

1

556-67-2

Octamethylcyclotetrasiloxane

No

3.70%

OECD 310

CO2

1

1873-88-7

1,1,1,3,5,5,5-Heptamethyltrisiloxane

No

0%

OECD 310/ ISO Guideline No 14593

CO2

1

2627-95-4

1,1,3,3-Tetramethyl-1,3-divinyldisiloxane

No

0%

OECD 301D

BOD

1

17928-28-8

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

No

0%

OECD 301F

BOD

1

17955-88-3

1,1,1,3,5,5,5-Heptamethyl-3-octyltrisiloxane

No

10 – 32 % after 25 d

OECD 301B

CO2

 1

60111-47-9

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

No

2.20%

OECD 301F

BOD

1

69304-37-6

1,3-Dichloro-1,1,3,3-tetraisopropyldisiloxane

No

0% (BOD); 100% (GC)

OECD 301C

BOD

1

70940-00-0

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

No

9.7 and 9.9%

OECD 301B

CO2

 1

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

 1

352230-22-9

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

No

0%

OECD 301F

BOD

1

In the study with L3, 0% biodegradation was observed in 28 days.

The study was conducted according to OECD 310 and is considered reliable. This is selected as the key study.

References: PFA. (2015i). Peter Fisk Associates. Siloxane analogue report. PFA.404.005.008.R2