Decyltrimethoxysilane

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:

From 30/08/2018 to 28/09/2018.

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

1992

Deviations:

yes

Remarks:

See 'principles of method if other than guideline'

Principles of method if other than guideline:

The test material was stated to be insoluble in water therefore a surfactant was used to emulsify the sample. To prepare the emulsion, 0.5023g of Decyltrimethoxysilane was intimately mixed with a 0.2502g of non-ionic surfactant (IGEPAL CA 630). The emulsion was gradually diluted by the addition of deionised water and then made up to volume (500ml).
Replicate standard BOD bottles were filled with the test concentration, prepared by addition of the emulsion stock solution to inoculated mineral medium (2.0ml/l). A series of test bottles were prepared with inoculated mineral medium only and used for the determination of "blank" DO losses.
To check the integrity of the test procedure a readily degradable reference chemical, sodium acetate, was tested at 5.00mg/l. A series of bottles containing dilution water plus IGEPAL CA 630 (dosed at the same concentration as used in the test treatment (1.0mg/l)), were run as a control and used as the blank correction values for the test material.
Initial dissolved oxygen (DO) concentrations were measured, using a YSI Model 58 dissolved oxygen meter. The bottles were incubated in the dark at 20.0 – 20.8C for the duration of the test period. Further measurements of dissolved oxygen concentration were made on bottles removed after 7, 14, 21 and 28 days.
The blank, control and reference vessels were shared with other studies and the data was recorded on the separate ‘common data’ lab-book.

Deviation from protocol / study plan:

The OECD 301D guideline states that bottles should be stoppered “ensuring that no air bubbles are enclosed”. During sampling on day 21, replicate 1 of the test treatment and on day 28, replicates 2 and 3 of the blank and replicate 2 of the test material contained notable gas head space. Although all bottles were filled to absolute volume at test initiation, poor stopper seals in the effected bottles allowed test media to evaporate during incubation. The presence of an airspace in a given bottle provides oxygen buffering capacity between the head space and aqueous phase, and may therefore introduce errors to the calculation of dissolved oxygen consumption by the inoculum. DO readings from the effected bottles in this study varied notably from uneffected bottles of the same treatment. For this reason, bottles found to contain a gas head space have not been considered in the calculation of results. In the opinion of the study director this action was required to provide an accurate assessment of the item under test and maintain the integrity of the study.
The inclusion of an additional replicate to each treatment later in the experimental period allows for the exclusion of compromised readings without greatly impairing an assessment of result reproducibility. Therefore, the removal of compromised vessels from the test and reference treatments did not have an effect on the ultimate outcome of the study or its validity.
Although the exclusion of two compromised replicates from the final blank results prevents an assessment of the reproducibility of the uncompromised value, it is the opinion of the study director that as degradation had achieved a plateau in both the reference and test treatments by approximately day 14, the lack of a reproducible final blank reading is not considered here to significantly influence or invalidate the ultimate result of this study. Therefore, this report is still considered to provide an accurate representation of the biodegradability of Decyltrimethoxysilane under the conditions of this study.

GLP compliance:

yes (incl. QA statement)

Remarks:

Currently unsigned.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum: Cambridge STW, Cowley Road, Cambridge
- Date collected: 30 August 2018
- Pretreatment: Filtered (Whatman No.54)
- Water filtered: yes
- Type and size of filter used: Whatman No. 54
- Temperature at start of test: 21.1°C
- Concentration of inoculum: 1ml/L

Duration of test (contact time):

28 d

Initial conc.:

2.01 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral nutrient stock solutions added to deionised water.
- Solubilising agent: non-ionic surfactant (IGEPAL CA 630) 1mg/l
- Test temperature: 22±2°C
- Aeration of dilution water: strongly for 20 minutes, letting it stand for 23 hours and 51 minutes and adding inoculum.
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: "standard BOD bottles"
- Method used to create aerobic conditions: medium inoculated with microorganisms and kept completely full, in darkness.
- Measuring equipment: YSI Model 58 dissolved oxygen meter
- Test performed in closed vessels due to significant volatility of test substance:
- Test performed in open system: No, glass BOD bottles were sealed.

SAMPLING
- Sampling frequency: 7 day intervals (0, 7, 14, 21, and 28)
- Sampling method: A dissolved oxygen meter (YSI Model 58) was used to measure dissolved oxygen.

CONTROL AND BLANK SYSTEM
- Inoculum blank: dilution water plus IGEPAL CA 630 (dosed at the same concentration as used in the test treatment (1.0 mg/L))

Reference substance:

acetic acid, sodium salt

Remarks:

referred to as "sodium acetate"

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

0 d

Parameter:

% degradation (O2 consumption)

Value:

46

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

44

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

48

Sampling time:

21 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

50

Sampling time:

28 d

Key result

Parameter:

ThOD

Value:

2 404 mg O2/g test mat.

Results with reference substance:

Sodium acetate exhibited 65% biodegradation after 28 days.

Biochemical oxygen demand

The DO measurements and calculated BOD values for the test substance and reference material

are given below:

	Incubation period (days)
	0	7		14		21			28
Incubator temperature (°C)	20.3	20.3		20.2		20.4			20.4
Average blank - DO (mg/l)	8.68	7.91		7.61		7.79			7.22
Average control - DO (mg/l)	8.58	7.65		6.91		7.15			6.97
Replicate number	1	1	2	1	2	1	2	3	1	2	3
Test substance – DO (mg/l)	8.59	5.73	5.17	5.19	4.4	0	5.34	4.36	4.44	0	4.68
Test substance - BOD (mgO2/g)	-	960	1239	861	1254	*	905	1393	1264	*	1144
Reference material – DO (mg/l)	8.66	5.25	5.42	3.95	5.05	4.67	5.01	4.84	4.83	4.79	4.35
Reference material – BOD (mgO2/g)	-	523	489	721	503	614	547	580	469	477	564

* Headspace present – replicates excluded

Degradation

The calculated percent degradation values for the test substance and reference material are given

below:

Replicate number	Incubation period (days)
	7		14		21			28
	1	2	1	2	1	2	3	1	2	3
Test substance (%)	40	52	36	52	*	38	58	53	*	48
Average degradation (%)	46		44		48			50
Reference material (%)	67	63	92	64	79	70	74	60	61	72
Average degradation (%)	65		78		74			65

* Headspace present – replicates excluded.

ThOD of sodium acetate 780mgO2/g.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Remarks:

Not readily biodegradable under the conditions of this test.

Conclusions:

Decyltrimethoxysilane is not readily biodegradable under the conditions of this test.

Executive summary:

The ready biodegradability of Decyltrimethoxysilane was evaluated during a GLP-compliant study performed in accordance with the OECD Testing Guideline 301D. The Closed Bottle Test method was used.

Sodium acetate was used as reference substance.

Secondary effluent from domestic sewage treatment plant was used for the purpose of this study. Oxygen consumption was evaluated on Day 0, 7, 14, 21 and 28.

Validation criteria were met.

After 7 days the O2 consumption indicated a biodegradation of 46% of the test substance. At the end of the study, on Day 28, the biodegradation of Decyltrimethoxysilane was 50%.

It is concluded that Decyltrimethoxysilane is not ready biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

From 01 February 2018 to 05 April 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Deviations:

no

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: Cambridge STW, Cowley Road, Cambridge
- Pretreatment: Filtered using Whatman no.54 (or equivalent) filter papers prior to addition to the mineral media.
- Concentration of sludge: 0.5 mL to 5 mL (typically 1 mL).

Duration of test (contact time):

28 d

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: As per OECD TG 301D.
- Test temperature: 22±2ºC

SAMPLING
- Sampling frequency: 0, 7, 14, 21, 28

Reference substance:

acetic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

55

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

55

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

36

Sampling time:

7 d

Details on results:

Control was valid only until Day 21.

see attached background document.

Validity criteria fulfilled:

yes

Remarks:

Validity criteria fulfilled until Day 21

Interpretation of results:

not readily biodegradable

Conclusions:

Decyltrimethoxysilane is not ready biodegradable.

Executive summary:

The ready biodegradability of Decyltrimethoxysilane was evaluated during a GLP-compliant study performed in accordance with the OECD Testing Guideline 301D. The Closed Bottle Test method was used.

Sodium acetate was used as reference substance.

Secondary effluent from domestic sewage treatment plant was used for the purpose of this study. Oxygen consumption was evaluated on Day 0, 7, 14, 21 and 28.

Validation criteria were not met on Day 28 of the study. Therefore only results until Day 21 were taken into account.

On Day 14 Decyltrimethoxysilane was degraded at 55% based on oxygen consumption. Same result was obtained on Day 21. Therefore no significant evolution of the biodegradation of the substance is expected at Day 28.

It is concluded that Decyltrimethoxysilane is not ready biodegradable.

Description of key information

The ready biodegradability of Decyltrimethoxysilane was evaluated during a GLP-compliant study performed in accordance with the OECD Testing Guideline 301D. The Closed Bottle Test method was used.

Sodium acetate was used as reference substance. Secondary effluent from domestic sewage treatment plant was used for the purpose of this study. Oxygen consumption was evaluated on Day 0, 7, 14, 21 and 28. Validation criteria were not met on Day 28 of the study. Therefore only results until Day 21 were taken into account. On Day 14 Decyltrimethoxysilane was degraded at 55% based on oxygen consumption. Same result was obtained on Day 21. Therefore no significant evolution of the biodegradation of the substance is expected at Day 28. It concluded that Decyltrimethoxysilane is not ready biodegradable.

Due to the validation criteria not being met, the study was repeated using the same method. Validation criteria were met during this repeated study. After 7 days the O2 consumption indicated a biodegradation of 46% of the test substance. At the end of the study, on Day 28, the biodegradation of Decyltrimethoxysilane was 50%. It is concluded that Decyltrimethoxysilane is not ready biodegradable. The results of the two studies are consistent.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater