Trimethoxyvinylsilane

Toxicity to soil macroorganisms except arthropods

Administrative data

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not reported

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with acceptable restrictions. No GLP or analysis of exposure media and no description of the test substance.

Principles of method if other than guideline:

Not described

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

no data

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM

- Common name: Rainbow trout

- Source: Fender's Fish Hatchery

- Feeding during test: no data

ACCLIMATION

- Acclimation period: A minimum of two weeks

- Acclimation conditions: same as test

- Type and amount of food: not reported

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Soft water

Test temperature:

12ºC

pH:

no data

Dissolved oxygen:

no data

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control), 100, 320 and 1000 mg/l

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material: Polyethylene lined

- Aeration: no data

- Renewal rate of test solution (frequency/flow rate): no data

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 1

- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Reconstituted soft water (EPA 660/3-75-009)

- Culture medium different from test medium: no

- Intervals of water quality measurement: no data


OTHER TEST CONDITIONS

- Adjustment of pH: no data

- Photoperiod: no data

- Light intensity: no data


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): daily mortality


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 3.2

- Range finding study: no data

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

191 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 95% confidence interval 125-281 ppm

Details on results:

- Mortality of control: 10% (1 fish)

- Other adverse effects control: none

Reported statistics and error estimates:

The LC50 value was calculated by probit analysis based on Finney's Method (Statistical Methods in Biological Assay, 1952).

Sublethal observations / clinical signs:

Table 1. Test results

Nominal test concentration (mg/l)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	10	10
100	0	0	0	0
320	30	100	100	100
1000	90	100	100	100

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour L50 value of 191 mg/l and NOEC of 100 mg/l have been determined for the effects of the test substance on mortality of Oncorhynchus mykiss. It is likely that the test organism were primarily exposed to the hydrolysis product of the test substance.

Cross-reference 2

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1993-06-01 to 1993-06-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

The concentration of hydrolysis products in stock solution determined by Total Organic Carbon analysis. The stock solution concentration (464 mg/l equivalent to a test substance concentration of 1145 mg/L) was used as the basis for determining the concentrations in the test media.

Vehicle:

no

Details on test solutions:

- Method: Test media prepared by dilution of a 1000 mg/L stock solution prepared by mixing for 18 h followed by filtration. TOC concentration of stock solution determined.

- Treatments: Control and nominal test concentrations of 57, 80, 115, 160, 229, 321 and 458 mg/L.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM

- Common name: Daphnia magna

- Strain: Clone 5

- Source: Stock culture

- Age at study initiation (mean and range, SD): <24 h

- Method of breeding: Parthenogenetic reproduction

- Feeding during test: None


ACCLIMATION

- Acclimation conditions (same as test or not): yes

- Type and amount of food: sufficient to be consumed each day leaving no residue

- Feeding frequency: daily

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Post exposure observation period:

none

Hardness:

The sum of the Ca2+ and Mg2+ ions was 2.5 mmol

Test temperature:

20 ±1ºC

pH:

7.0 - 7.2

Dissolved oxygen:

6.5 - 8.1 mg/L

Salinity:

Not applicable

Nominal and measured concentrations:

Control and nominal test concentrations of 57, 80, 115, 160, 229, 321 and 458 mg/L.

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open

- Material, size, headspace, fill volume: glass cylinder containing 10 ml of test medium

- Aeration: none

- No. of organisms per vessel: 5

- No. of vessels per concentration (replicates): 4

- No. of vessels per control (replicates): 4


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Elendt M4 medium

- Intervals of water quality measurement: end of test


OTHER TEST CONDITIONS

- Photoperiod: Dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization after 24 and 48 h exposure

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.4


STATISTICS

EC50 and confidence interval determined by Probit analysis

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

297.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 223.9 - 224.2

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

168.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 126.9 - 224.2

Details on results:

- Mortality of control: 0

Results with reference substance (positive control):

- EC50: >0.9, <1.9 mg/L

Reported statistics and error estimates:

The EC50 value and its 95% confidence interval was calculated by Probit analysis.

Table 1. Test results

Nominal test substance concentration (mg/L)	Percentage immobile Daphnia after 24 hours	Percentage immobile Daphnia after 48 hours
0 (Control)	0	0
57	5	25
80	5	25
115	5	35
160	0	35
229	25	45
321	55	75
458	90	100

Validity criteria fulfilled:

yes

Conclusions:

A 48-h EC50 value of 168.7 mg/L has been determined for the effects of the test substance on mobility of Daphnia magna. A NOEC was not determined in the test. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Cross-reference 3

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

14 Feb - 17 Feb 2006

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Some observations associated with validity criteria in the equivalent OECD test guideline are not reported.

Qualifier:

according to guideline

Guideline:

other: Circular on Test Methods of New Chemical Substances (Japan), Alga growth inhibition test

Deviations:

no

GLP compliance:

yes

Remarks:

according to the Japanese GLP Standard

Analytical monitoring:

yes

Details on sampling:

- Sampling method: sampled directly by each vessel and pre-treatment was not performed
- Sample storage conditions before analysis: no storage before analysis
- Methanol was measured, since the test item was quickly hydrolysed

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test item was measured and diluted in dilution water by stirring for 120 min

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: Alga
- Strain: ATCC22662
- Source (laboratory, culture collection): American Type Culture Collection
- Age of inoculum (at test initiation): after 4-day preculture
- Method of cultivation: on a shaker

ACCLIMATION
- Acclimation period: 4 days (2006-02-10 ~ 2006-02-14)
- Culturing media and conditions (same as test or not): same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

23.0 - 23.1 °C (23 ± 2 °C), measured at the study initiation, 24, 48 and 72 hours after exposure

pH:

8.0 - 9.9, measured at the initiation and at the end of the study.

Nominal and measured concentrations:

Nominal concentration: 100 mg/L
Measured concentration: 89 mg/L (time-weighted mean; the concentration was determined based on the measured concentration of the hydrolysis product, methanol)

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL Erlenmeyer-flask
- Type (delete if not applicable): closed
- Material, headspace, fill volume: glass, 490 mL, 100 mL
- Initial cells density: 5000 cells/mL
- Control end cells density: 855900 ± 20700 cells/mL
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: same medium

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no adjustment
- Photoperiod: continuously
- Light intensity and quality: 65 µE/m2/s

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: counting chamber; electronic particle counter;

TEST CONCENTRATIONS
- Range finding study: performed twice.
- Test concentrations: 1) 1, 10 and 100 mg/L, 2) 100 mg/L
- Results used to determine the conditions for the definitive study:
1) Inhibition rate was 16% (close system), -42% (open system) in 1 mg/L, 12% (close system), -44% (open system) in 10 mg/L, and 1% (close system), -36% (open system) in 100 mg/L, respectively.
2) Inhibition rate was -14% (close system) and 6% (open system). Measured concentration was 108 mg/L at the study initiation and 87 mg/L in a close system at the end of the study.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (analytical grade)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 89 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: the concentration was determined based on the measured concentration of the hydrolysis product, methanol

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 89 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: the concentration was determined based on the measured concentration of the hydrolysis product, methanol

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 89 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: the concentration was determined based on the measured concentration of the hydrolysis product, methanol

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 89 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: the concentration was determined based on the measured concentration of the hydrolysis product, methanol

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no abnormality was observed

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- EC50: 0.428 ± 0.0683 mg/L

Reported statistics and error estimates:

Student's t-test, subsequent to F test for homogeneity of variances.

Table 1. Calculated concentration of the test substance using methanol concentration

Nominal concentration (mg/L)	Mean measured concentration mg/L (Percent of nominal)				Mean measured Concentration (*), mg/L
	0 hour	24 hours	48 hours	72 hours
Control	< 0.03	< 0.03	< 0.03	< 0.03
100	105 (105)	100 (100)	75.3 (75)	80.2 (80)	89 (89)

*: Time-weighted mean measured concentration

Table 2. Growth inhibition (%)

Nominal conc. (mg/L) [Mean measured conc. *]	Inhibition rate (%) Growth rate	Inhibition rate (%) Biomass
Control	-	-
100 [89]	0.3	0.5

*: Time-weighted mean measured concentration

Conclusions:

A 72-hour NOEC value of >89 mg/l has been determined for the effects of the test substance on biomass and growth rate Pseudokirchneriella subcapitata. Due to the rapid rate of hydrolysis, the concentration was determined based on the measured concentration of the hydrolysis product, methanol.

Cross-reference 4

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

29 Mar 19 Apr 2006

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 211 (Daphnia magna Reproduction Test)

Deviations:

no

GLP compliance:

yes

Remarks:

according to the Japanese GLP Standard

Analytical monitoring:

yes

Details on sampling:

- Sampling method: sampled directly by each vessel and pre-treatment was not performed
- Sample storage conditions before analysis: no storage before analysis
- Methanol was measured, since the test item was quickly hydrolysed

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: test item was measured and diluted in dilution water with stirring for 120 min

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: Incorporated Administrative Agency, National Institute for Environmental Studies, Tsukuba, Japan
- Age of parental stock (mean and range, SD): within 24 hours
- Feeding during test: yes
- Food type: Chlorella vulgaris
- Amount: 0.15 mgC/animal/day

ACCLIMATION
- Acclimation period: 2006-03-08 ~ 2006-03-29
- Acclimation conditions (same as test or not): similar to test (acclimation condition: water was changed three times a week, test condition: water was changed everyday)
- Type and amount of food:Chlorella vulgaris, 0.2 mgC/animal/day
- Health during acclimation (any mortality observed): < 5% during 2 weeks before exposure

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

21 d

Hardness:

240 - 250 (as CaCO3) mg/L, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.

Test temperature:

19.7 - 20.2 °C, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.

pH:

7.1 - 8.4, measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.

Dissolved oxygen:

4.4 - 8.8 mg/L (> 3mg/L), measured at day 0, 7, 14, 15 and 21 in the freshly prepared test solution and at day 1, 8, 15 and 21 in the old test solution before renewal.

Nominal and measured concentrations:

Nominal concentration: 12, 21, 38, 67 and 120 mg/L
Time-weighted mean: 7.2, 14.6, 28.1, 52.4 and 99.8 mg/L
The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL beaker
- Type (delete if not applicable): closed with a teflon sheet
- Material, fill volume: glass, 80 mL
- Aeration: no
- Renewal rate of test solution (frequency/flow rate): once a day
- No. of organisms per vessel: 1
- No. of vessels per concentration (replicates): 10
- No. of vessels per control (replicates): 10

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: same medium

OTHER TEST CONDITIONS
- Adjustment of pH: no adjustment
- Photoperiod: 16 hours in the light, 8 hours in the dark
- Light intensity: < 800 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
mortality and general condition (abnormal behaviour) of parental animals, cumulative number of juveniles and time to first brood production were observed everyday.

RANGE-FINDING STUDY
- Test concentrations: 120 mg/L (nominal concentration)
- Results used to determine the conditions for the definitive study: An acute toxicity test of daphnia magna was performed and EC50 for 48 hours was > 120 mg/L.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate (analytical grade)

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

28.1 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

cumulative number of juveniles per adult

Remarks on result:

other: The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis

Duration:

21 d

Dose descriptor:

LOEC

Effect conc.:

52.4 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks:

cumulative number of juveniles per adult

Remarks on result:

other: The measured concentration was calculated based on the concentration of methanol yielded on hydrolysis

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

119 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: (95% CL 104 - 149 mg/l; extrapolated from effects at conc. 14.6-99.8 mg/l).

Details on results:

- Mortality of parent animals: see Table 2
- No. of offspring produced per day per female: see Table 3
- Time to first brood release or time to hatch: Control: 8 - 9 days, 7.2 mg/L: 8 - 9 days, 14.6 mg/L: 8 - 13 days, 28.1 mg/L: 8 - 9 days, 52.4 mg/L: 8 - 9 days, 99.8 mg/L: 9 - 15 days

Results with reference substance (positive control):

- Results with reference substance valid? Yes
- Relevant effect levels: EC 50 was 0.75 ± 0.14 mg/L

Reported statistics and error estimates:

Logit test for EC50, Williams's multi-comparison test for NOEC and LOEC

Table 1. Calculated concentration of the test item using methanol concentration in test water

Nominal concentration (mg/L)		Measured concentration (mg/L)						TWM (*1) (% of nominal)
	Date	0 new	1 old	14 new	15 old	20 new	21 old
Control		<0.05	<0.05	<0.05	<0.05	<0.05	<0.05	-
12.0		10.1	10.5	9.75	7.21	10.3	0.32 (*2)	7.20 (60) (*3)
21.0		19.2	17.6	17.1	13.5	15.6	6.01	14.6 (70)
38.0		33.5	32.0	31.1	20.2	31.6	21.5	28.1 (74)
67.0		57.3	51.3	60.3	37.6	67.4	44.3	52.4 (78)
120		104	96.4	102	77.0	120	101	99.8 (83)

New: Freshly prepared test solution

Old: Old test solutions before renewal

*1: Time-weighted mean calculated concentration during 21 days

*2: This value is estimate because it is not within the range of the calibration curve.

*3: This value is given for reference because of containing the estimate value.

Table 2. Mortality of parental Daphnia

Nominal concentration (mg/L)	Mean measured concentration (mg/L)	Cumulative Number of Dead (Percent Mortality)
		Day 1	2	4	7	14	21
Control	-	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
12.0	7.20	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
21.0	14.6	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
38.0	28.1	0 (0)	1 (10)	1 (10)	1 (10)	1 (10)	1 (10)
67.0	52.4	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
120	99.8	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)
12.0	7.20	0 (0)	0 (0)	0 (0)	1 (10)	1 (10)	1 (10)

Table 3. Cumulative number of juveniles produced per adult alive for 21 days

Nominal Conc., mg/L	Calculated Cnc., mg/L	Mean Cumulative Numbers of Juveniles ± S.D.	Inhibition Rate (%)	Significant difference
Control	-	107.8 ± 13.8
12.0	7.20	123.7± 8.1	-14.7	-
21.0	14.6	124.5 ± 18.9	-15.5	-
38.0	28.1	108.0 ± 19.4	-0.2	-
67.0	52.4	95.7 ± 17.2	11.2	**
120	99.8	69.8 ± 16.5	35.5	**

-: indicates no significant difference

**: indicates a significant difference (a = 0.01) from the control.

Validity criteria fulfilled:

yes

Conclusions:

A 21 day NOEC value of 28.1mg/L has been determined for the effects of the test substance on reproduction of Daphnia magna. Due to the rapid rate of hydrolysis the concentration was calculated using the measured concentration of the non-silanol hydrolysis product, methanol.

Cross-reference 5

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Endpoint:

partition coefficient

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Justification for type of information:

See attached QMRF/QPRF

Principles of method if other than guideline:

The result was obtained using an appropriate QSAR method (see attached QMRF and QPRF for details).

The model is an adaptation of the existing SRC model KOWWIN v1.67, which is a component of the EPIWIN Suite. The model is based on fragment values. That is, the chemical structure is broken down into its constituent functional groups, and the contribution of each group toward the overall partition coefficient is calculated. The constants used within KOWWIN have been derived by SRC from a wide range of organic chemicals. Whilst this method is good in principle, the model was developed using a wide range of organic chemicals and only a few organosilicon compounds. Therefore, a validation procedure was undertaken to assess the applicability of the model to alkoxysilane compounds. It was noted that the model under-predicted log Kow for alkoxysilanes; therefore, a correction factor is applied when this structural feature is present. The adapted model applies to di- and tri-alkoxysilanes.

Partition coefficient type:

octanol-water

Key result

Type:

log Pow

Partition coefficient:

1.1

Temp.:

20 °C

pH:

ca. 7

Conclusions:

A log Kow value of 1.1 at 20°C was obtained for the substance using an accepted calculation method. The result is considered to be reliable.

Cross-reference 6

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Adsorption/desorption [trimethoxy(vinyl)silane]: Low potential for adsorption due to very rapid hydrolysis in contact with water

Log Koc for silanol hydrolysis product = -0.02 (predicted).

The substance hydrolyses very rapidly to substances which have low log K_ow values (<3) and thus have low potential for adsorption, and the requirement for testing is waived.

For environmental exposure assessment, adsorption is predicted for the silanol hydrolysis product using the‘non-hydrophobics’ log K_ow-based prediction method for log K_oc developed by Sabljic and Güsten (1995) for the European Commission, and recommended in EU Guidance.

The relevant equation is:

Log K_oc= 0.52 log K_ow+ 1.02

Therefore, log K_oc for silanol hydrolysis product, vinylsilanetriol = -0.02.

Reference:

Sabljic A and Güsten H (1995) QSARs for soil sorption. in: overview of structure-activity relationships for environmental endpoints. Hermens JLM (ed), report prepared within the framework of the project "QSAR for prediction of fate and effects of chemicals in the environment", an international project of the Environmental Technologies RTD programme (DG XII/D-1) of the European Commission under contract number EV5V-CT92-0211.

Cross-reference 7

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Bioaccumulation: terrestrial: Low potential for bioaccumulation

No data are available for terrestrial bioaccumulation. The substance is not expected to bioaccumulate, due to its very rapid hydrolysis in water and the low K_ow values of the hydrolysis products.

Cross-reference 8

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

Hydrolysis: 0.04 h at pH 4, 0.1 h at pH 7 and 0.004 h at pH 9 and 20-25°C (QSAR)

Hydrolysis half-lives at 20 -25°C of 0.04 h at pH 4, 0.1 h at pH 7 and 0.004 h at pH 9 were determined for the substance using a validated QSAR estimation method. Also, in a preliminary study conducted in accordance with OECD 111, hydrolysis half-lives of <10 minutes at pH 4, <2.4 h at pH 7 and <10 minutes at pH 9 and 50°C were determined for the substance. Both results were considered to be reliable and used as weight of evidence. A half-life of 0.24 h at pH 7 and 23°C, from a study of non-assignable reliability adds further weight of evidence to the very rapid hydrolysis potential of the submission substance.

As the hydrolysis reaction may be acid or base catalysed, the rate of reaction is expected to be slowest at around pH 7 and increase as the pH is raised or lowered. For an acid-base catalysed reaction in buffered solution, the measured rate constant is a linear combination of terms describing contributions from the uncatalyzed reaction as well as catalysis by hydronium, hydroxide, and general acids or bases.

k_obs = k₀ + k_H3O+[H3O⁺] + k_OH^-[OH^-] + k_a[acid] + k_b[base]

At extremes of pH and under standard hydrolysis test conditions, it is reasonable to suggest that the rate of hydrolysis is dominated by either the hydronium or hydroxide catalysed mechanism.

Therefore, at low pH:

k_obs ˜ k_H3O+[H3O⁺]

At pH 4 [H₃O⁺] = 10^-4 mol dm^-3 and at pH 2 [H₃O⁺] = 10^-2 mol dm^-3; therefore, k_obs at pH 2 should be approximately 100 times greater than k_obs at pH 4.

The half-life of a substance at pH 2 is calculated based on:

t_1/2(pH 2) = t_1/2(pH 4) / 100

The calculated half-life of the substance at pH 2 is therefore less than 2 seconds. However, it is not appropriate or necessary to attempt to predict accurately when the half-life is less than 5-10 seconds. As a worst-case it can therefore be considered that the half-life of the substance at pH 2 and 20-25°C is approximately 5 seconds.

Reaction rate increases with temperature therefore hydrolysis will be faster at physiologically relevant temperatures compared to standard laboratory conditions. Under ideal conditions, hydrolysis rate can be recalculated according to the equation:

DT₅₀(XºC) = DT₅₀(T) * e^(0.08.(T-X))

Where T = temperature for which data are available and X = target temperature.

Thus, for trimethoxy(vinyl)silane the hydrolysis half-life at 37.5ºC and pH 7 (relevant for lungs and blood) is approximately 2 minutes. At 37.5ºC and pH 2 (relevant for conditions in the stomach following oral exposure), it is not appropriate to apply any further correction for temperature to the limit value and the hydrolysis half -life is therefore approximately 5 seconds.

The hydrolysis products in this case are vinylsilanetriol (CAS 143-48-6) and methanol (CAS 67-56-1; EC No. 200-659-6).

The hydrolysis data for substances used in this dossier for read-across purposes for other endpoints are now discussed.

Hydrolysis of the read-across substance trichloro(vinyl)silane (CAS 75-94-5; EC No. 200-917-8)

Data for the substance, trichloro(vinyl)silane (CAS 75-94-5) are read-across to the submission substance trimethoxy(vinyl)silane for toxicity to microorganisms endpoint. The silanol hydrolysis product and the rate of hydrolysis of the two substances are relevant to this read-across, as discussed in the appropriate section for the endpoint.

For trichloro(vinyl)silane, hydrolysis half-lives at 1.5°C of <1 minute at pH 4, pH 7 and pH 9 were read-across from trichloro(methyl)silane in accordance with OECD Test Guideline 111 (Dow Corning Corporation 2001).

The hydrolysis products are vinylsilanetriol and hydrochloric acid.

Hydrolysis of the read-across substance diethoxy(dimethyl)silane (CAS 78-62-6; EC No. 201-127-6)

Data for the substance, diethoxy(dimethyl)silane (CAS 78-62-6) are read-across to the submission substance trimethoxy(vinyl)silane for basic toxicokinetics endpoint. The rate of hydrolysis of the two substances are relevant to this read-across, as discussed in the appropriate section for the endpoint.

For diethoxy(dimethyl)silane, hydrolysis half-lives at 20-25°C of 0.3 hours at pH 4, 5.5 hours at pH 7 and 0.3 hours at pH 9 were determined using validated QSAR estimation methods.

The hydrolysis products are dimethylsilanediol and ethanol.