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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): 37% in 28 days (EU Method C.4-A), read-across from an analogous substance. No significant biodegradation of the silanol hydrolysis product is expected.

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 [3-(2,3-epoxypropoxy)propyl]dimethoxy(methyl)silane (CAS No. 65799-47-5), therefore good quality data for the structurally-related substance, [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8), have been read across. Both substances hydrolyse in the time scale of the test and have structurally similar silanol hydrolysis products, [3-(2,3-epoxypropoxy)propyl]methylsilanediol and [3-(2,3-epoxypropoxy)propyl]silanetriol respectively.

The other hydrolysis product is methanol in both cases. Methanol is readily biodegradable (OECD 2004).

[3-(2,3-Epoxypropoxy)propyl]dimethoxy(methyl)silane (CAS No. 65799-47-5) and [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8) 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. [3-(2,3-epoxypropoxy)propyl]dimethoxy(methyl)silane (CAS No. 65799-47-5) and [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8) are members of this sub-class.

It is therefore considered valid to read-across the results for [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA, 2013f) attached in Section 13.

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

10217-34-2

Triethoxy-[2-(7-oxabicyclo[4.1.0]hept-3-yl)ethyl]silane

III-12

No

28%

OECD 301D

1

-15

2530-83-8

[3-(2,3-Epoxypropoxy)propyl]trimethoxysilane

III-12

no

37%

Annex V C4-A

1

4

2602-34-8

[3-(2,3-Epoxypropoxy)propyl]triethoxysilane

III-12

no

53%

OECD 301F

1

3

In the study with [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8), 37% biodegradation was observed in 28 days.

[3-(2,3-Epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8) hydrolyses within the timescale of the ready biodegradation study to [3-(2,3-epoxypropoxy)propyl]silanetriol and methanol. The biodegradation observed in the study is attributable to the biodegradation of the methanol hydrolysis product.

Methanol is readily biodegradable (OECD 2004).

No significant biodegradation is expected for the silanol hydrolysis product.

There is a less reliable study available for [3-(2,3-epoxypropoxy)propyl]trimethoxysilane (CAS No. 2530-83-8) (Prost, 1983) which reports a much higher biodegradation of 90% in 7 days (ISO 7827; DOC). However, the source of inoculum is not stated in the study report, and it is possible that the bacteria were acclimated to the test substance.

References:

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

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