Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

Biodegradation in water, screening tests: 0% degradation in 28 days (OECD Guideline 301A), 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 chloro(dimethyl)vinylsilane (CAS 1719-58-0), therefore good quality data for the structurally-related substance, dichloro(methyl)(vinyl)silane (CAS 124-70-9), have been read across. Both substances hydrolyse very rapidly and have structurally similar silanol hydrolysis products, dimethyl(vinyl)silanol and methyl(vinyl)silanediol, respectively. In view of the very rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment.

The other hydrolysis product is hydrogen chloride for both substances. Hydrogen chloride is inorganic and biodegradation is not relevant.

Chloro(dimethyl)vinylsilane (CAS 1719-58-0) and dichloro(methyl)(vinyl)silane (CAS 124-70-9) are within an analogue group of substances within which,in general, there is 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 (based on structure/functionality) with different main codes (used to represent the different sub-classes). However, read-across is carried out between substances with the same main code in most cases.

The table below presents ready biodegradation data for substances within the sub-class (I-2) of alkoxysilanes, silanols, acetoxysilanes and chlorosilanes, etc, where the Si part is of low-biological reactivity, once any hydrolysis is accounted for. Chloro(dimethyl)vinylsilane (CAS 1719-58-0) and dichloro(methyl)(vinyl)silane (CAS 124-70-9) are members of this sub-class.

It is therefore considered valid to read-across the results for dichloro(methyl)(vinyl)silane (CAS 124-70-9) 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 5 dossier.

Table Ready biodegradation data available for substances within the relevant sub-class (I-2) of chemicals

CAS

Name

Readily biodegradable? Yes/no

Result: Biodegradation after 28 day

Guideline

Reliability

Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for[1]

01066-40-6

Hydroxytrimethylsilane

No

0%

OECD 310 and ISO Guideline N 14593

1a

0

013154-25-1

Chlorotri(3-methyl-propyl)silane

No

0%

OECD 301B

1a

0

139147-73-2

Silane, dichlorodicyclopentyl-

No

0.80%

OECD 301D

2b

1

000098-12-4

Cyclohexyltrichlorosilane

No

0%

OECD 301C

1a

0

000124-70-9

Dichloro(methyl)(vinyl)silane

No

-6.78% (0%)

OECD 301 A

1a

0

017865-32-6

Cyclohexyldimethoxymethylsilane

No

15-17%

OECD 301D

1a

-5

126990-35-0

Dicyclopentyldimethoxysilane

No

12%

OECD 301C

1

-5

None46

t-butoxycyclopentyldimethoxysilane

No

15% BOD; 25% TOC; 100% GC

OECD 301C

1a

7

017689-77-9

Triacetoxyethylsilane

Yes

74% in 21 days

EC C4-A

1a

-1

017980-47-1

Triethoxyisobutylsilane

Yes

75%

OECD 301D

1a

15

002943-75-1

Triethoxyoctylsilane

No

31.50%

OECD 301D

1a

-11

035435-21-3

Triethoxy(2,4,4-trimethylpentyl)silane

No

13%

OECD310

1a

-30

016415-13-7

Triethoxyhexadecylsilane

No

43% by BOD; 74% by HPLC

MITI

1c

16

001067-25-0

Trimethoxypropylsilane

No

54%

Annex V C4-A

1a

4

087135-01-1

1,6-Bis(trimethoxysilyl)hexane

yes but not meeting 10-day window

74%

OECD 301B

1a

24

None45

Mixture of 1,1- and 1,2-bis(trimethoxysilyl)ethane

Yes

93% BOD; 78% TOC; 100% GC (ethanol?)

"Biodegradation study of chemical substances by microorganisms and the like"[2]

1a

18

018395-30-7

Trimethoxy(2-methylpropyl)silane

No

36 - 47%

OECD 301B

1a

4

002768-02-7

Trimethoxyvinylsilane

No

51%

OECD 301F

1a

-9

142877-45-0

Silane, trimethoxy(1,1,2-trimethylpropyl)-

No

31%

OECD 301D

1a

-2

 

In the study with dichloro(methyl)(vinyl)silane (CAS124-70-9), 0% (-6.78%) biodegradation was observed in 28 days. The study was conducted according to OECD 301A and is considered to be reliable. This is selected as the key study.

The study is considered to be reliability 1 (reliable without restrictions); the read across of the result is considered to be reliability 2 (reliable with restrictions).

[1]The negative values in this column are where the biodegradation rate observed in the test is less than that expected assuming only alkoxy/acetoxy parts biodegrade. This could be due to low solubility of parent substance or low rates of hydrolysis. These values should in effect be considered as zero.

 

[2]Stipulated in "Testing Method for New Chemical Substances etc." (Kanhogyo No.5, Yakuhatsu 615, 49Kikyoku No.392, July 13, 1974 )

References:

PFA, 2013f, Peter Fisk Associates, Biodegradation Main Analogue Group report, PFA.300.005.007