Trimethoxy(2,4,4-trimethylpentyl)silane

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-01-27 to 2009-02-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): sewage sludge micro-organisms obtained from the secondary treatment stage of Severn Trent Water Plc treatment plant at Loughborough, Leicestershire, UK. (primarily domestic sewage)

- Preparation of inoculum for exposure: filtered and sparged with CO2

Duration of test (contact time):

28 d

Initial conc.:

32.9 mg/L

Based on:

test mat.

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

CO2 evolution

Parameter followed for biodegradation estimation:

DOC removal

Remarks:

for blank and reference vessels on day 0 and 28

Details on study design:

TEST CONDITIONS

- Test temperature: 20±1°C

TEST SYSTEM

- Culturing apparatus: 125 ml glass Wheaton bottles sealed with Teflon lined silicon septa and aluminium crimp caps.

- Number of culture flasks/concentration: One hundred and four (104): Innoculum blank: thirty three (33) vessels, test substance: twenty nine (29) vessels, Reference substance: thirty three (33) vessels, Toxicity control: nine (9) vessels

SAMPLING

- Sampling frequency: 0, 2, 6, 8, 14, 16, 21 and 28 days for blank, test and reference substances. Sampling of toxicity control took place on days 0, 8 and 14.

- Sampling method: acidification of the test vessel then sampling of the headspace gas.



CONTROL AND BLANK SYSTEM

- Inoculum blank: yes

- Toxicity control: yes

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

13

Sampling time:

28 d

Details on results:

Biodegradation of the reference substance was >60% after 14 days (100%) (83% degradation after 28 days).

The toxicity control attained 49% degradation after 14 days.

 Table 1: Total Inorganic Carbon (TIC), % Biodegradation values and Direct Organic Carbon (DOC) values

Day	Inoculum Blank							Reference Substance										Test Substance						Toxicity Control
	TIC (mg)					DOC (mg C/l)		TIC (mg)					%Biodeg by TIC	DOC (mg C/l)		% Biodeg by DOC		TIC (mg)					%Biodeg.	TIC (mg)			%Biodeg.
	R1	R2	R3	R4	R5	R1	R2	R1	R2	R3	R4	R5	Mean	R1	R2	R1	R2	R1	R2	R3	R4	R5	Mean	R1	R2	R3	Mean
0	0.12	0.10	0.09	-	-	1.24	1.31	0.10	0.10	0.12	-	-	0	20.98	20.97	-	-	0.09	0.10	0.10	-	-	0	0.11	0.12	0.10	0
2	0.13	0.12	0.13	-	-	-	-	1.63	1.67	1.74	-	-	72	-	-	-	-	0.16	0.14	0.15	-	-	1	-	-	-	-
6	0.09	0.16	0.10	-	-	-	-	1.96	1.79	2.02	-	-	84	-	-	-	-	0.14	0.12	0.13	-	-	0	-	-	-	-
8	0.09	0.17	0.10	-	-	-	-	2.08	2.12	2.29	-	-	95	-	-	-	-	0.17	0.14	0.14	-	-	1	2.03	2.11	2.12	46
14	0.11	0.17	0.16	-	-	-	-	2.31	2.38	2.21	-	-	100	-	-	-	-	0.19	0.19	0.17	-	-	1	2.22	2.25	2.26	49
16	0.13	0.13	0.14	-	-	-	-	2.39	2.12	2.20	-	-	99	-	-	-	-	0.21	0.29	0.25	-	-	6	-	-	-	-
21	0.09	0.12	0.14	-	-	-	-	1.98	1.96	1.96	-	-	86	-	-	-	-	0.32	0.33	0.33	-	-	10	-	-	-	-
28	0.12	0.14	0.14	0.16	0.14	1.51	1.01	1.90	1.92	1.88	2.06	1.88	83	1.10	2.12	100	96	0.29	0.43	0.51	0.50	0.52	13	-	-	-	-

Validity criteria fulfilled:

yes

Interpretation of results:

other: under test conditions no significant degradation was observed

Conclusions:

A biodegradation result of 13% in 28 days was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

2009-01-27 to 2009-02-24

Justification for type of information:

Please refer to the attached justification for grouping of substances provided in IUCLID Section 13.

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (CO2 evolution)

Value:

13

Sampling time:

28 d

Description of key information

Not readily biodegradable (13% biodegradation after 28 days, OECD 310, RA to CAS No. 35435-21-3)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

There is no reliable ready biodegradation data available for the parent substance trimethoxy(2,4,4-trimethylpentyl)silane (CAS No. 34396-03-7) or its silanol hydrolysis product, therefore good quality data has been read across from the structurally analogue substance triethoxy(2,4,4-trimethylpentyl)silane (CAS No. 35435-21-3). Both parent substances share the same silanol hydrolysis product (2,4,4-trimethylpentyl)silanetriol, the other hydrolysis products being methanol (target) and ethanol (source). The two alcohol hydrolysis products are both known to be readily biodegradable (OECD, 2004a and b). The source substance is expected to show a slower hydrolysis rate under environmental conditions than the target substance with an estimated DT50 of 43 h at pH 7 and 20-25 °C (QSAR). However, both substances are expected to hydrolyse well within the timescale of a ready biodegradation test (28 days) and therefore the hydrolysis products can be expected to be the predominant forms, which are present during the study.

Additional information is given in an analogue justification attached in Section 13 of the IUCLID dossier.

In a test to investigate the biodegradation in water according to OECD guideline 310 (Harlan, 2009a) and GLP conditions activated sludge was exposed to 32.9 mg/l of triethoxy(2,4,4-trimethylpentyl)silane. A biodegradation of 13% in 28 days based on CO2 evolution was determined. This biodegradation is due to the biodegradation of the ethanol hydrolysis product, which biodegrades rapidly (OECD SIDS, 2004). The methanol hydrolysis product formed by the target substance trimethoxy(2,4,4-trimethylpentyl)silane is also readily biodegradable (OECD SIDS, 2004). Hence, no significant biodegradation is expected for the silanol hydrolysis product and it can not be regarded as readily biodegradable.

References:

OECD SIDS, 2004a. Ethanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.

OECD SIDS, 2004b. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.