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EC number: 246-377-7 | CAS number: 24636-31-5
Biodegradation in water: screening tests
Administrative data
Link to relevant study record(s)
Description of key information
Biodegradation in water (screening tests): 69% in 28 days (OECD 301F), read-across from a structurally related substance.
Once the biodegradation of the alkoxy groups is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent (calculated as 39%) and this value is expected to be more representative of the registration substance. The silanol hydrolysis product would not be considered as readily biodegradable.
Key value for chemical safety assessment
- Biodegradation in water:
- readily biodegradable but failing 10-day window
Additional information
There are no reliable ready biodegradation data available for 3-(chlorodimethylsilyl)propyl methacrylate (CAS No. 24636-31-5), therefore good quality data for the structurally-related substance, 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0), have been read across.
3-(Chlorodimethylsilyl)propyl methacrylate (CAS No. 24636-31-5) has hydrolysis half-lives of <1 minute at pH 4, pH 7 and pH 9 and 25°C (based on read-across from chlorotrimethylsilane (CAS No. 75-77-4)), to form 3-[hydroxy(dimethyl)silyl]propyl methacrylate and hydrochloric acid. Similarly, 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0) has measured half-lives of 0.018 h at pH 4, 1.87 h at pH 7, and 0.068 h at pH 9 and 20°C to form 3-trihydroxysilylpropyl methacrylate and methanol. Extensive or complete hydrolysis in the course of the 28 day ready biodegradation study is to be expected for these surrogate substances and the registered substance. In view of the rapid hydrolysis, it is the silanol hydrolysis product that is relevant for environmental risk assessment.
Methanol is readily biodegradable (OECD 2004).
Hydrochloric acid is inorganic and biodegradation is not relevant.
3-(Chlorodimethylsilyl)propyl methacrylate (CAS No. 24636-31-5) and 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0) are within an analogue group of substances within which substances are readily biodegradable failing the 10-day window. The conclusion is based on reliable data available for three substances, all of which are organosilicon substances with methacrylate groups. Once the biodegradation of the alkoxy groups is taken into account there is evidence that the methacrylate side-chain is biodegrading to some extent. However, the silanol hydrolysis product would not be considered as readily biodegradable.
The table below presents ready biodegradation data for substances within the analogue group III-2 (Substances (chlorosilanes, silanes, alkoxysilanes or siloxanes) containing acrylate functionality in the hydrocarbon chain attached to Si (i.e. remote from the Si)). 3-(Chlorodimethylsilyl)propyl methacrylate (CAS No. 24636-31-5) and 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0) are members of this analogue group.
It is therefore considered valid to read-across the results for 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0) to fill the data gap for the registered substance. Additional information is given in a supporting report (PFA 2013h) attached in Section 13.
Table: Ready biodegradation data available for substances within the relevant III-2 analogue group of chemicals
CAS |
Name |
Readily biodegradable? Yes/no |
Result: Biodegradation after 28 day |
Guideline |
Reliability |
Corrected % biodegradation once alkoxy/acetoxy biodegradation is accounted for |
|
5577-72-0 |
2-Propenoic acid, 2-methyl-, (triethoxysilyl)methyl ester |
yes but not meeting 10-day window |
73% |
OECD 301F |
1 |
18 |
|
2530-85-0 |
3-trimethoxysilylpropyl methacrylate |
yes but not meeting 10-day window |
69% |
OECD 301F |
1 - Key |
39 |
|
3978-58-3 |
2-Propenoic acid,2-methyl-, (diethoxymethylsilyl)methyl ester |
yes but not meeting 10-day window |
73% |
OECD 301F |
1 |
29 |
|
In the study with 3-trimethoxysilylpropyl methacrylate (CAS No. 2530-85-0), 69% biodegradation was observed in 28 days.
The study was conducted according to OECD 301F and is considered reliable (Grutzner 2002). This result is selected as the key study because it was the study conducted most recently.
Another study conducted according to EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test) gave a result of 74% biodegradation in 28 days (not passing the 10-day window) (Enste-Diefenback 1995). This is used as a supporting study.
References:
OECD (2004). SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.
PFA (2013h). Peter Fisk Associates, Biodegradation III-2 Analogue Group report, PFA.300.005.005
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