Reaction products of [3-(2,3-epoxypropoxy)propyl]trimethoxysilane and triacetoxyvinylsilane.

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1999-03-23 to 1999-04-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: A sample of activated sludge was taken on 1999-03-03 from an oxidation ditch in the municipality of Berkel en Rodenrijs, the Netherlands.

- Preparation of inoculum for exposure: The sludge suspension and the water used to prepare the medium were each aerated with CO2-free air overnight before use.

- Concentration of sludge: 30mg/L

Duration of test (contact time):

28 d

Initial conc.:

47 mg/L

Based on:

test mat.

Initial conc.:

20 other: mg carbon per litre

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: A medium with a higher nitrogen content than that specified in the guideline was used, in order to prevent nutrient limitation during the course of the degradation study.

- Test temperature: 20 ± 2°C

- Aeration of dilution water: yes

TEST SYSTEM

- Culturing apparatus: Two-litre glass bottles closed with plastic screw caps. A 20 mL glass vial containing the CO2 absorbing fluid (5 mL of 0.4M NaOH solution) was suspended from the screw cap of each bottle.

- Number of culture flasks/concentration: Three

- Details of trap for CO2 and volatile organics if used: 5 mL of 0.4M NaOH solution


SAMPLING

- Sampling frequency: The carbon dioxide traps were removed and replaced on the following test days: 1, 3, 6, 10, 14, 17, 21, and 28

- Sampling method: CO2 absorbed was determined by titration of the sodium hydroxide with 0.1M HCl using a Metrohm 686 Titroprocessor

CONTROL AND BLANK SYSTEM

- Inoculum blank: Yes, reference substance sodium acetate

- Abiotic sterile control: Yes

- Toxicity control: Yes, reference substance sodium acetate

STATISTICAL METHODS:
The mineralisation data (% degradation) were fitted to various production equations using non-linear regression.

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

50

Sampling time:

28 d

Details on results:

Reference substance:
Toxicity control indicated no inhibition

Table 1: CO₂ evolved (mg/L) and calculated % biodegradation for inoculum blank, test substance, reference substance and toxicity control

Type of suspension	1d		3d		6d		10d		14d		17d		21d		28d
	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg	CO2evolved (mg/l)	(%) biodeg
Inoculum Blank (mean of three replicates)	1.7	-	4.5	-	9.0	-	13.4	-	16.2	-	17.7	-	19.2	-	20.9	-
Test substance (mean of three replicates)	4.3	6	12.1	17	23.4	32	29.2	40	32.6	45	33.5	46	34.7	47	35.9 (36.7 including CO­2in the medium released by acidification)	49 (50)
Reference substance (mean of two replicates)	4.4	6	20.1	28	36.5	50	45.9	63	51.8 (56.9 including CO­2in the medium released by acidification)	71 (78)	54.2	74	56.3	77	58.9 (62.6 including CO­2in the medium released by acidification)	81 (86)
Toxicity control (mean of two replicates)	6.8	5	30.4	21	55.9	38	71.3	49	81.3	56	84.8	58	88.3	60	92.7 (96.6 including CO­2in the medium released by acidification)	63 (66)

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Biodegradation of 50% in 28 days (CO2 evolution) was determined in a reliable study according to an appropriate test protocol and in compliance with GLP.

Description of key information

Biodegradation in water: screening tests: 50% in 28 days (OECD Method 301B (CO₂ evolution, modified Sturm test)). The silanol hydrolysis products, [3-(2,3-epoxypropoxy)propyl]silanetriol and vinylsilanetriol, are not expected to biodegrade to any significant extent.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

A reliable biodegradation study is available with the registration substance and is selected as the key study. The study was conducted according to OECD Test Guideline 301B, and gives a biodegradation result of 50% degradation in 28 days.

The constituents of the registration substance hydrolyse rapidly (half-life <12 hours at pH 7 and 25°C) to [3-(2,3-epoxypropoxy)propyl]silanetriol, vinylsilanetriol, acetic acid/acetates and methanol. The biodegradation observed in the studies is attributable to the biodegradation of acetic acid and methanol, which are readily biodegradable. Neither [3-(2,3-epoxypropoxy)propyl]silanetriol nor vinylsilanetriol are expected to biodegrade to any significant extent.