2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

Biodegradation in water: screening tests

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 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (CAS 3388-04-3), therefore good quality data for the structurally-related substance, [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2), have been read across. Both substances hydrolyse in the time scale of the test and have a structurally identical silanol hydrolysis products, 2-(3,4-epoxycyclohexyl)ethylsilanetriol.

The other hydrolysis products are methanol and ethanol respectively. Methanol and ethanol are readily biodegradable (OECD 2004a and 2004b).

2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (CAS 3388-04-3) and [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2) 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 III-12 of epoxyalkyl alkoxysilanes. 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (CAS 3388-04-3) and [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2) are members of this sub-class.

It is therefore considered valid to read-across the results for [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2) 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 III-12 of chemicals

CAS	Name	Main code	Readily biodegradable? Yes/no	Result: Biodegradation after 28 day		Guideline	Reliability	Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for
010217-34-2	[2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane	III-12	No		28%	OECD 301D	1	-15
002530-83-8	[3-(2,3-epoxypropoxy)propyl]trimethoxysilane	III-12	no		37%	Annex V C4-A	1	4
002602-34-8	[3-(2,3-epoxypropoxy)propyl]triethoxysilane	III-12	no		53%	OECD 301F	1	3

In the study with [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2), 28% biodegradation was observed in 28 days. [2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane (CAS 10217-34-2) hydrolyses within the timescale of the ready biodegradation study to [2-(3,4-epoxycyclohexyl)ethyl]silanetriol and ethanol. The biodegradation observed in the study is attributable to the biodegradation of the ethanol hydrolysis product. Ethanol is readily biodegradable (OECD, 2004b). No significant biodegradation is expected for the silanol hydrolysis product. The study was conducted according to OECD 301D and is considered 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).

References:

OECD (2004a): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.

OECD (2004b): SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 19-22 October 2004, Ethanol, CAS 64-17-5.

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