Diacetoxydi-tert-butoxysilane

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Test method is designed as a new in vitro alternative. No data on GLP.

Principles of method if other than guideline:

Method: other: Luminiscent bacteria toxicity test (LBT) (Microtox). The test protocol was that published by Microbics Corporation (Bulich et al., 1981).

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Test substance was extracted in 2 % NaCl (Microtox Diluent) using 4 g of sample per 20 mL of saline.

Test organisms (species):

Photobacterium phosphoreum

Details on inoculum:

An LBT is accomplished using a suspension of luminescent bacteria prepared by hydrating a vial of the Microtox Reagent. The Reagent comprises a freeze-dried preparation of luminescent bacteria (Photobacterium phosphoreum).
Aliquots of 10 µL of the cell suspension are transferred to test vials containing 2% saline solution.

Test type:

static

Water media type:

freshwater

Total exposure duration:

15 min

Test temperature:

15 ºC

Nominal and measured concentrations:

No data

Details on test conditions:

TEST SYSTEM
- Test vessel: All luminescent bacteria assays were conducted using the Microtox Toxicity Analyzer System manufactured by Microbics Corporation (Carlsbad, CA).
The liquid reagents and freeze-dried bacterial reagent were those produced by Microbics.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): The toxicity is expressed as light lost. Light readings are taken for each test vial before and 15 minutes after sample addition. The amount of light lost per sample dilution is proportional to the toxicity of that sample (Microbics Corporation, 1988).

Reference substance (positive control):

not specified

Duration:

15 min

Dose descriptor:

EC50

Effect conc.:

11 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

other: light loss

Details on results:

Light loss was expressed as gamma value and is the ratio of light lost to the light remaining in each of the challenged test cuvettes containing the bacterial suspension. That concentration of test substance causing a 50% reduction in light after a 15-minute exposure was designated the EC50 value.

The EC50 of Acetic acid in the LBT testing was 11 mg/L.

Validity criteria fulfilled:

not specified

Remarks:

(No data on reference substance)

Conclusions:

The EC50 of Acetic acid in the LBT testing was 11 mg/L.

Executive summary:

The Luminescent bacteria toxicity test (LBT) was performed on the marine phosphorescent bacterium Photobacterium phosphoreum. This test was conducted using the Microtox Toxicity Analyzer System manufactured by Microbics Corporation (Carlsbad, CA). The test protocol was that published by Microbics Corporation (Bulich et al., 1981). The toxicity is expressed as light lost. Light readings are taken for each test vial before and 15 minutes after sample addition. The amount of light lost per sample dilution is proportional to the toxicity of that sample (Microbics Corporation, 1988).

The EC50 of Acetic acid in the LBT testing was 11 mg/L.

Reference 2

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

other: Test method is designed as a new in vitro alternative. No data on GLP.

Principles of method if other than guideline:

Method: other: Luminescent bacteria toxicity test (LBT) (Microtox). The test protocol was that published by Microbics Corporation (Bulich et al., 1981).

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Test substance was extracted in 2 % NaCl (Microtox Diluent) using 4 g of sample per 20 mL of saline.

Test organisms (species):

Photobacterium phosphoreum

Details on inoculum:

An LBT is accomplished using a suspension of luminescent bacteria prepared by hydrating a vial of the Microtox Reagent. The Reagent comprises a freeze-dried preparation of luminescent bacteria (Photobacterium phosphoreum).
Aliquots of 10 µL of the cell suspension are transferred to test vials containing 2% saline solution.

Test type:

static

Water media type:

freshwater

Total exposure duration:

15 min

Test temperature:

15 ºC

Nominal and measured concentrations:

No data

Details on test conditions:

TEST SYSTEM
- Test vessel: All luminescent bacteria assays were conducted using the Microtox Toxicity Analyzer System manufactured by Microbics Corporation (Carlsbad, CA).
The liquid reagents and freeze-dried bacterial reagent were those produced by Microbics.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): The toxicity is expressed as light lost. Light readings are taken for each test vial before and 15 minutes after sample addition. The amount of light lost per sample dilution is proportional to the toxicity of that sample (Microbics Corporation, 1988).

Reference substance (positive control):

not specified

Duration:

15 min

Dose descriptor:

EC50

Effect conc.:

22 500 mg/L

Nominal / measured:

not specified

Conc. based on:

test mat.

Basis for effect:

other: light loss

Details on results:

Light loss was expressed as gamma value and is the ratio of light lost to the light remaining in each of the challenged test cuvettes containing the bacterial suspension. That concentration of test substance causing a 50% reduction in light after a 15-minute exposure was designated the EC50 value.

The EC50 of Sodium acetate in the LBT testing was 22500 mg/L.

Validity criteria fulfilled:

not specified

Remarks:

(No data on reference substance)

Conclusions:

The EC50 of Sodium acetate in the LBT testing was 22500 mg/L.

Executive summary:

The Luminescent bacteria toxicity test (LBT) was performed on the marine phosphorescent bacterium Photobacterium phosphoreum. This test was conducted using the Microtox Toxicity Analyzer System manufactured by Microbics Corporation (Carlsbad, CA). The test protocol was that published by Microbics Corporation (Bulich et al., 1981). The toxicity is expressed as light lost. Light readings are taken for each test vial before and 15 minutes after sample addition. The amount of light lost per sample dilution is proportional to the toxicity of that sample (Microbics Corporation, 1988).

The EC50 of Sodium acetate in the LBT testing was 22500 mg/L.

Reference 3

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From January 13 to February 10, 2012

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

According to OECD 301 F. GLP study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Vehicle:

no

Test organisms (species):

activated sludge

Details on inoculum:

- Initial biomass concentration: 30 mg/L
- Source of inoculum/activated sludge: Aeration tank of Sewage Treatment Plant "Czajka" Warsaw.
- Storage conditions: The coarse particles were removed by filtration. Such prepared sludge was washed in the medium and was placed in laboratory-scale unit where the aerobic conditions were maintained by means of an intense aeration with compressor and aerators.
- Preparation of inoculum for exposure: The concentrated sludge was suspended in mineral medium to yield a concentration of 3-5 g suspended solids/l and it was aerated until application. After complete re-suspension was achieved, a sample was withdrawn just before use for the determination of the dry weight of the suspended solids.
- Pretreatment: Inocula was pre-conditioned to the experimental conditions. Pre-conditioning consisted of aerating activated sludge in mineral medium for 5 days at the test temperature of 22 ºC.
- Initial biomass concentration: 30 mg/L SS

Test type:

other: Readily biodegradability

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Test temperature:

22 ± 2 ºC.

pH:

6-8.5

Nominal and measured concentrations:

100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Closed WTW OxiTop OC 110 respirometer for BOD determination
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 164 ml volume
- Aeration: aerobic conditions
- No. of organisms per vessel: 30 mg/L SS activated sludge inoculum
- No. of vessels per concentration (replicates):
Test solution: 3 replicates, each containing 100 mg/L test item and 30 mg/L SS inoculum.
Inoculum blank: 3 replicates, each containing 30 mg/L SS inoculum.
Procedure control: 3 replicates, each containing 100 mg/L reference item (sodium acetate) and 30 mg/L SS inoculum.
Toxicity control: 3 replicates, each containing 100 mg/L test item, 100 mg/L reference item (sodium acetate) and 30 mg/L SS inoculum.

TEST MEDIUM / WATER PARAMETERS
- Preparation of test solutions:
The solutions of the test and reference items were prepared, in separate batches, in mineral medium equivalent to a concentration of 100 mg chemical/litre, using stock solutions. The pH values were adjusted to 7,4 ± 0,2. with 0.1N NaOH. The requisite volume of solutions of test and reference items, were introduced respectively, into triplicate flasks. 16.4 ml of stock solutions of test and reference items were introduced into the right flasks. Mineral medium only was added to further flasks (for inoculum controls). Potassium hydroxide solution (0.66 ml of 45% KOH) was added to each of the CO2-absorber compartments. The determined content of inoculum at the end of preconditioning was equal to 5.31 mg suspended solids/l. To give a concentration of suspended solids equal to 30 mg/l in each flask, 0.93 ml of preconditioned suspension of inoculum was added into each flask. The flasks were made up to 164 ml volume with prepared mineral medium.

OTHER TEST CONDITIONS
- Adjustment of pH: yes, pH was adjusted to 7.54 with 0.1N NaOH.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Biodegradation % based on oxygen consumption.

TEST CONCENTRATIONS
- Test concentrations: 100 mg/L

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: readily biodegradability

Details on results:

The NOEC of methyltriacetoxysilane was determined to be 100 mg/L since the substance degrades well (79.5% of biodegradation at 28 days) and did not inhibit the degradation in the toxicity test (83.9% of biodegradation after 28 days) up to 100 mg/L.

Table: Sample oxygen uptake: biodegradability

		time, days
		3	5	7	9	12	14	16	18	21	23	25	28
Test item O2uptake, mg/dm^3	a1	72.4	89.6	101.5	107.5	114.0	117.2	118.0	119.0	121.5	124.7	127.2	129.6
	a2	68.1	83.3	92.3	98.9	106.1	111.3	113.6	114.8	117.0	119.2	121.5	123.7
	a3	65.6	81.6	91.7	98.5	107.0	110.1	112.9	114.0	115.3	118.8	121.6	123.5
	am. avg	68.7	84.8	95.1	101.6	109.0	112.9	114.8	115.9	117.9	120.9	123.4	125.6
Blank test O2uptake. mg/dm^3	b1	8.7	13.8	17.5	20.2	28.6	32.1	37.0	39.8	42.5	42.2	44.7	45.8
	b2	5.0	9.3	11.4	14.5	21.6	30.9	31.2	33.3	34.9	35.2	37.2	38.8
	b3	8.4	12.2	13.4	16.9	27.7	34.2	36.2	39.7	42.8	42.5	43.2	45.5
	bm. avg	7.4	11.8	14.1	17.2	26.0	32.4	34.8	37.6	40.0	40.0	41.7	43.4
Referencet item O2uptake. mg/dm^3	w1	53.1	67.0	74.7	79.8	87.6	90.5	93.3	96.3	100.9	101.0	104.0	106.7
	w2	59.7	71.0	79.6	85.5	91.8	95.2	97.1	98.5	101.0	101.0	103.7	104.0
	w3	59.8	75.6	83.0	89.4	95.9	98.3	100.8	101.0	104.0	105.6	107.0	110.5
	wm. avg	57.5	71.2	79.1	84.9	91.8	94.6	97.1	98.6	102.0	102.5	104.9	107.0
Toxicity control O2uptake. mg/dm^3	tox1	110.6	132.1	143.5	152.0	162.2	167.6	170.8	175.9	180.6	186.4	189.8	195.4
	tox2	131.8	155.0	166.0	172.6	179.0	182.4	185.7	189.3	191.8	195.3	198.0	202.7
	tox3	116.8	139.1	154.4	163.7	172.0	174.0	177.0	180.6	183.0	185.0	186.0	188.7
	toxm. avg	119.7	142.1	154.7	162.8	171.1	174.7	177.9	181.9	185.2	188.9	191.3	195.6
Corrected BOD. mg/dm^3	(a1-bm)	65.0	77.8	87.4	90.3	88.1	84.8	83.2	81.4	81.4	84.8	85.5	86.2
	(a2-bm)	60.7	71.6	78.2	81.7	80.1	78.9	78.8	77.2	76.9	79.3	79.8	80.3
	(a3-bm)	58.3	69.8	77.6	81.3	81.0	77.7	78.1	76.4	75.3	78.8	79.9	80.1
test item % degradation ThOD = 103.4 mgO2/l	R1(a1)	62.9	75.3	84.5	87.3	85.2	82.1	80.4	78.7	78.7	82.0	82.7	83.4
	R2(a2)	58.7	69.2	75.6	79.1	77.5	76.3	76.3	74.6	74.4	76.7	77.2	77.7
	R3(a3)	56.3	67.5	75.1	78.6	78.4	75.2	75.5	73.9	72.8	76.2	77.3	77.5
	R. avg	59.3	70.7	78.4	81.7	80.3	77.8	77.4	75.7	75.3	78.3	79.0	79.5
reference item % degradation ThOD = 78.0 mgO2/l	R1(tox1)	58.6	70.8	77.7	80.3	79.0	74.5	75.0	75.3	78.0	78.3	79.9	81.1
	R2(tox2)	67.1	75.9	84.0	87.6	84.5	80.5	79.9	78.1	78.1	78.3	79.5	77.7
	R3(tox3)	67.2	81.8	88.4	92.5	89.7	84.5	84.6	81.3	82.0	84.2	83.8	86.0
	Rtoxavg	64.3	76.2	83.3	86.8	84.4	79.8	79.8	78.2	79.4	80.2	81.0	81.6
toxicity control % degradation ThOD = 181.4 mgO2/l	R1(tox1)	56.9	66.3	71.4	74.3	75.1	74.6	75.0	76.2	77.5	80.7	81.6	83.8
	R2(tox2)	68.6	79.0	83.8	85.7	84.4	82.7	83.2	83.6	83.7	85.6	86.2	87.8
	R3(tox3)	60.3	70.2	77.4	80.8	80.5	78.1	78.4	78.9	78.8	80.0	79.6	80.1
	Rtoxavg	61.9	71.8	77.5	80.3	80.0	78.4	78.9	79.6	80.0	82.1	82.5	83.9

At 28 days of test performance:

- The aerobic biodegradation of methyltriacetoxysilane attained 79.5% of biodegradability (77.6% at 10 -day window).

- The aerobic biodegradation of the toxicity test reached 83.9% of biodegradation.

- The aerobic biodegradation of reference item sodium acetate reached 81.6% of biodegradability.

- The oxygen uptake of the inoculum blank was equal to 43.4 mg/dm3.

Validity criteria fulfilled:

not applicable

Conclusions:

The NOEC (28d) for microorganism toxicity of the test item methyltriacetoxysilane was determined to be 100 mg/L (based on biodegradation).

Executive summary:

A ready biodegradability manometric respirometry test was perfomed according to OECD Guideline 301 F. Test item methyltriacetoxysilane was incubated for 28 days at a concentration of 100 mg/L with 30 mg/L SS activated sludge inoculum under aerobic conditions in a mineral medium. Additionally, to check the possible inhibitory effect of the test item, a toxicity test run in parallele (100 mg/L test item with 100 mg/L reference substance and 30 mg/L SS activated sludge inoculum) at same conditions. The NOEC (28d) of methyltriacetoxysilane was determined to be 100 mg/L since the substance degraded well (79.5% of biodegradation at 28 days) and did not inhibit the degradation in the toxicity test (83.9% of biodegradation after 28 days) up to 100 mg/L.

Reference 4

Endpoint:

toxicity to microorganisms, other

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
The analogue Methyltriacetoxysilane which shares the same functional group with Diacetoxydi-tert-butoxysilane, also has comparable values for the relevant molecular properties for toxicity to microorganism.
See attached the reporting format.

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

132.76 mg/L

Conc. based on:

other: (read-across approach from analogue methyltriacetoxysilane)

Basis for effect:

other: (read-across from analogue methyltriacetoxysilane. Basis for effect: % biodegradation)

Details on results:

Based on the experimental results on analogue substance methyltriacetoxysilane where NOEC (28d) was determined to be 100 mg/L (based on biodegradation), the read-across approach was applied and NOEC (28 d) for diacetoxydi-tert-butoxysilane was calculated to be 132.76 mg/L.

Validity criteria fulfilled:

not applicable

Conclusions:

Based on the experimental results on analogue substance methyltriacetoxysilane, the read-across approach was applied and NOEC (28 d) for diacetoxydi-tert-butoxysilane was calculated to be 132.76 mg/L.

Executive summary:

A ready biodegradability manometic respirometry test was perfomed according to OECD Guideline 301 F on analogue methyltriacetoxysilane and 28 day-NOEC was determined to be 100 mg/L since the substance was readily biodegradable (79.5% of biodegradation at 28 days) and did not inhibit the degradation of the toxicity test (83.9% of biodegradation after 28 days) up to 100 mg/L under aerobic conditions. Based on these results, the read-across approach was applied and 28 day-NOEC for diacetoxydi-tert-butoxysilane was calculated to be 132.76 mg/L under test conditions.

Reference 5

Endpoint:

toxicity to microorganisms, other

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable.
See attached the reporting format.

Reason / purpose for cross-reference:

read-across source

Duration:

15 min

Dose descriptor:

EC50

Effect conc.:

26.76 mg/L

Remarks on result:

other: (Read-across approach from acetic acid effect concentration based on test material and basis for effect: light loss)

Details on results:

Based on the experimental results obtained with the supporting substance acetic acid for Photobacterium phosphoreum (15 min EC50 = 11 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for Diacetoxydi-tert-butoxysilane is calculated to be 26.76 mg/L.

Validity criteria fulfilled:

not applicable

Conclusions:

Based on the experimental results obtained with the supporting substance acetic acid for Photobacterium phosphoreum (15 min EC50 = 11 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for Diacetoxydi-tert-butoxysilane is calculated to be 26.76 mg/L.

Executive summary:

Based on the experimental results obtained with the supporting substance acetic acid for Photobacterium phosphoreum (15 min EC50 = 11 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for Diacetoxydi-tert-butoxysilane is calculated to be 26.76 mg/L.

Reference 6

Endpoint:

toxicity to microorganisms, other

Type of information:

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

Adequacy of study:

supporting study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
Diacetoxydi-tert-butoxysilane undergoes rapid hydrolysis in aqueous to acetic acid and the corresponding trisilanols. Trisilanols undergo continuous condensation reactions to produce higher molecular weight siloxanes which are considered biologically unavailable. Therefore, the observed toxicity is likely due to the acetic acid and their values are comparable. Acetic acid and its salts are grouped together because of their close structural relationship (US EPA officially recognises acetic acid and acetates as a subcategory). Therefore, sodium acetate has comparable values with acetic acid and the target substance diacetoxydi-tert-butoxysilane.
See attached the reporting format.

Reason / purpose for cross-reference:

read-across source

Duration:

15 min

Dose descriptor:

EC50

Effect conc.:

40 102.55 mg/L

Remarks on result:

other: (Read-across approach from sodium acetate effect concentration based on test material, basis for effect: light loss)

Details on results:

Based on the experimental results obtained with the supporting substance sodium acetate for Photobacterium phosphoreum (15 min EC50 = 22500 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for diacetoxydi-tert-butoxysilane is calculated to be 40102.55 mg/L.

Validity criteria fulfilled:

not applicable

Conclusions:

Based on the experimental results obtained with the supporting substance sodium acetate for Photobacterium phosphoreum (15 min EC50 = 22500 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for diacetoxydi-tert-butoxysilane is calculated to be 40102.55 mg/L.

Executive summary:

Based on the experimental results obtained with the supporting substance sodium acetate for Photobacterium phosphoreum (15 min EC50 = 22500 mg/L, basis for effect: light loss), the read-across approach is applied and the 15 min EC50 for diacetoxydi-tert-butoxysilane is calculated to be 40102.55 mg/L.

Description of key information

Key study: Based on the experimental results on analogue substance methyltriacetoxysilane (OECD 301F and GLP), the read-across approach was applied and NOEC (28 d) for diacetoxydi-tert-butoxysilane was calculated to be 132.76 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

132.76 mg/L

Additional information

Key study: Read-across from experimental data on analogue substance Methyltriacetoxysilane:

In the ready biodegradability test perfomed according to OECD Guideline 301 F on analogue methyltriacetoxysilane the 28 day-NOEC was determined to be 100 mg/L since the substance degraded well and did not inhibit the degradation of the toxicity test. Based on these results, the read-across approach was applied and 28 day-NOEC for diacetoxydi-tert-butoxysilane was calculated to be 132.76 mg/L under test conditions.