2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane

Toxicity to microorganisms

Description of key information

Toxicity to microorganisms: 30 minute NOEC 100 mg/l (OECD 209), read-across from an analogous/structurally related substance.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

There are no reliable microorganism toxicity 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 are structurally similar and have the same silanol hydrolysis product, 2-(3,4-epoxycyclohexyl)ethylsilanetriol. Hydrolysis within the tests would not be significant.

The other hydrolysis products are methanol and ethanol respectively. Methanol and ethanol do not have adverse effects on microorganisms (OECD, 2004a and b).

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 significant toxicity to microorganisms. This analogue group for the toxicity to microorganisms 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 microorganism toxicity 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.

This result is supported by a second read-across within the same analogue group and main code: good quality data for the analogous/structurally-related substance, [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS 2530-83-8), have been read across. The use of a supporting value is useful in view that the key read across study uses a relatively short exposure duration. Both substances hydrolyse rapidly and have silanol hydrolysis products that share epoxide as a functional group. In view of the rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment. The other hydrolysis product is methanol.

Table: Microorganism toxicity data available for substances within the relevant sub-class III-12 of chemicals

CAS	Name	Main code	Result: E(I)C50 (mg/l)	Result: NOEC (or EC10/ EC20) (mg/l)	Guideline Number	Test method	Species	Duration	Reliability
010217-34-2	[2-(3,4-epoxycyclohexyl)ethyl]triethoxysilane	III-12		<10% inhibition at 100 mg/l	OECD 209	ASRI	-	30 minutes	1
002530-83-8	[3-(2,3-epoxypropoxy)propyl]trimethoxysilane	III-12	>100 mg/l		OECD 209	ASRI	-	3hr	1
002602-34-8	[3-(2,3-epoxypropoxy)propyl]triethoxysilane	III-12	>1000 mg/l	≥1000	OECD 209	ASRI	-	3hr	1

In the study with triethoxy-[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane (CAS 10217 -34 -2), an activated sludge respiration inhibition 30 -minute NOEC value of 100 mg/l was reported. 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).

In the study with [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS 2530-83-8), an activated sludge respiration inhibition 3h EC50 value of >100 mg/l was reported. 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, 2013j, Peter Fisk Associates, STP Microorganism toxicity Main Analogue Group report, PFA.300.003.006