Registration Dossier

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Data are available from reliable in vitro studies of bacterial mutagenicity and cytogenicity to mammalian cells for methylsilanetriyl triacetate. No further information is available for the registered substance, however, data are available for the closely related substances triethoxy(methyl)silane (CAS number 2031-67-6) and trichloro(methyl)silane (CAS number 75-79-6) from in vitro assays on mutagenicity to mammalian cells.
Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without metabolic activation in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 and Escherichia coli WP2 uvrA (OECD TG 471) (BioReliance, 2002a).
Cytogenicity in mammalian cells: negative in CHO cells (OECD TG 473) (BioReliance, 2002b).
Mutagenicity in mammalian cells: read-across from analogous substance trichloro(methyl)silane (CAS 75-79-6): negative in mouse lymphoma L5178Y cells (similar to OECD 476) (Litton Bionetics, 1978b).
Mutagenicity in mammalian cells: read-across from analogous substance triethoxy(methyl)silane (CAS 2031-67-6): negative in mouse lymphoma L5178Y cells (similar to OECD 476) (Litton Bionetics, 1978a).

Link to relevant study records

Referenceopen allclose all

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001-10-24 - 2001-11-28
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
Aroclor 1254 induced rat liver S9
Test concentrations with justification for top dose:
100, 333, 1000, 3333 and 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: Sponsor's request due to compatibility with the target cells. A fresh bottle, containing less that 0.1% water, to be opened and used once for each phase of the study.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene 10 µg/plate
Remarks:
WP2 uvrA with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene 1.0 µg/plate
Remarks:
TA98, TA100, TA1535, TA1537 with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
TA98 without metabolic activation 1.0 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
TA100, TA1535 without metabolic activation 1.0 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
TA1537 without metabolic activation 75 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
WP2 uvrA without metabolic activation 1000 µg/plate
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

ACTIVATION: S9 mix contained glucose-6 phosphate and NADP as co-factors, and 10% S9. 0.5 ml of S9 was added to 2 ml top agar, 100 µl tester strain and 50 µl of test solution giving a final concentration of 1% S9.

DURATION

- Exposure duration: 48 - 72 hours at 37±2°C


SELECTION AGENT (mutation assays): histidine-deficient agar

NUMBER OF REPLICATIONS: triplicate plates, experiment repeated


DETERMINATION OF CYTOTOXICITY
- Method: other: condition of background lawn



Evaluation criteria:
The mean of each positive control must exhibit at least a 3 fold increase in the number of revertants over the mean value of the respective vehicle control. A minimum of three non-toxic dose levels is required to evaluate assay data. A dose level is considered toxic if one or both of the following criteria are met: (1) A >50% reduction in the mean number of revertants per plate as compared to the mean vehicle control value. This reduction must be accompanied by an abrupt dose-dependent drop in the revertant count. (2) A reduction in the background lawn. Data sets will be judged positive if the increase in mean revertants at the peak dose response is equal to or greater than 2 times the mean negative control value.
Statistics:
None shown in report
Key result
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid

 Experiment 1 Plate incorporation - Number of revertants per plate (mean of three plates)

Treatment µg/plate

TA98

TA100

TA1535

TA1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

0*

15

 18

154

181

 14

 12

  4

 7

11

 11

100

11

 21

170

161

 13

 10

  3

 5

10

  8

333

11

 16

155

196

   9

 13

  4

 6

 9

  6

1000

11

 17

140

178

 13

 11

  3

 5

 9

  8

3333

15

 18

166

152

 21

 8

  6

 4

10

 12

5000

20

 21

149

159

 20

 14

  5

 5

10

  8

Positive control

92

365

479

584

215

102

633

 58

71

296

*solvent control with DMSO

 Experiment 2 Plate incorporation - Number of revertants per plate (mean of three plates)

Treatment µg/plate

TA98

TA100

TA1535

TA1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

0 *

16

 20

134

154

 19

 12

  8

   7

12

 12

100

10

 19

138

165

 21

 15

  5

 10

14

 13

333

15

 23

152

163

 17

 19

  5

 10

12

 17

1000

15

 28

137

181

 19

 14

 13

   9

12

 16

3333

15

 25

136

145

 21

 16

  9

  6

10

 14

5000

13

 22

124

151

 18

 16

  7

  4

10

 13

Positive control

67

495

441

690

203

124

352

137

84

291

 *solvent control with DMSO

Conclusions:
Methylsilanetriyl triacetate has been tested for mutagenicity to bacteria in a study which was conducted according to the OECD TG 471, and in compliance with GLP. No evidence of a test substance related increase in the number of revertants was observed with or without metabolic activation in the initial or the repeat experiments. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.
Endpoint:
in vitro cytogenicity / chromosome aberration study in mammalian cells
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
in vitro mammalian chromosome aberration test
Species / strain / cell type:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
275, 550, 1100, 2200 µg/ml
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: information from the sponsor and compatibility with the target cells.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
mitomycin C
Remarks:
without metabolic activation 10 and 20 µg/ml
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
Remarks:
with metabolic activation 1 and 2 mg/ml
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: none
- Exposure duration: 4 hours (with and without metabolic activation) and 20 hours (without metabolic activation)
- Expression time (cells in growth medium): 20 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 20 hours

SPINDLE INHIBITOR (cytogenetic assays): Colcemid
STAIN (for cytogenetic assays): Giesma

NUMBER OF REPLICATIONS: duplicate cultures

NUMBER OF CELLS EVALUATED: 200 cells were examined for chromosome aberrations

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; other: cell growth inhibition

OTHER EXAMINATIONS:
- Determination of polyploidy: yes
- Determination of endoreplication: yes
Evaluation criteria:
A result was considered positive when there was a dose-dependent and statistically significant increase in the number of cells with aberrations.
Statistics:
Fischer's exact test was used to compare the percent aberrant cells of each treatment group with the solvent control.
Key result
Species / strain:
Chinese hamster Ovary (CHO)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
15% and 2200 µg/ml
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH: none - pH was adjusted to approximately 7.0 by addition of 1N NaOH
- Effects of osmolality: none

Summary of results

Treatment time (hours)

Recovery time (hours)

Harvest time (hours)

Metabolic activation

Toxicity at highest dose scored (µg/ml)

Mitotic reduction

Structural abnormalities observed

Numerical abnormalities observed

4

16

20

-

None

None

None

None

20

0

20

-

None

None

None

None

4

16

20

+

None

13%

None

None

Conclusions:
Methylsilanetriyl triacetate has been tested according to OECD 473 and under GLP. No increase in the number of chromosome aberrations per cell or the number of cells with aberrations was detected at any concentration with and without metabolic activation in Chinese hamster ovary cells. Solvent and positive controls gave expected results. It is considered that the test substance is negative for the induction of chromosome aberrations under the conditions of the test.
Endpoint:
in vitro gene mutation study in mammalian cells
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
yes
Remarks:
non-activated mouse liver S9 mix used for activation; positive control toxicity expt 2 +MA was lower than required by current guideline
Principles of method if other than guideline:
Method: Litton Bionetics standard procedure: Screening Program for the Identification of Potential Mutagens and Carcinogens. Protocol Number : DMT 100
GLP compliance:
no
Type of assay:
mammalian cell gene mutation assay
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
Mouse liver S9
Test concentrations with justification for top dose:
0.01, 0.02 0.04, 0.08, 0.16, and 0.32 µL/ml, equivalent to approximately 10, 20, 40, 80, 160 and 320 µg/ml
Vehicle
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethanol

- Justification for choice of solvent/vehicle: It is assumed by the reviewer that the solvent was chosen based on solubility properties and relative non-toxicity to L5178Y cells.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
(without activation)
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
N-dimethylnitrosamine
Remarks:
(with activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION

- Exposure duration: 4 hours

- Expression time (cells in growth medium): 3 days

- Selection time (if incubation with a selection agent): 10 days

- Fixation time (start of exposure up to fixation or harvest of cells): 3 days 4 hours


SELECTION AGENT (mutation assays): THMG (thymidine, hypoxanthine, methoxotrexate, glycine)

NUMBER OF REPLICATIONS: 3 plates for each test concentration, assay repeated

DETERMINATION OF CYTOTOXICITY

- Method: relative total growth
Evaluation criteria:
A compound is considered mutagenic if:

- A dose response relationship is observed over three of the four dose levels employed

- The minimum increase at the high level of the dose response curve is at least 2.5 times greater than the solvent control value

- The solvent control data are within the normal range of spontaneous background for the TK locus.
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
other: 0.32 µl/ml, equivalent to 320 µg/ml
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
The test substance did not induce mutation at the thymidine kinase locus with or without activation. Because there was very little toxicity observed in the non activation tests, the study was repeated. The repeat study produced greater levels of toxicity but was still negative for inducing mutations.

Table 2 :Results of Mammalian Mutagenicity assay (Test 1) with L5178Y/TK+/Mouse Lymphoma cells

Concentration µg/ml

Mutant* Frequency

Mutant* Frequency

%Relative Growth.

%Relative Growth.

Cytotoxicity
(yes/no)

- MA

+ MA

- MA

+ MA

-

Solvent control

10.6

12.2

100

100

-

Negative control

12.2

10.3

123

64.1

-

Positive control

511.0

368.1

18.5

5.8

yes

0.1

8.0

-

134.2

-

no

0.02

10.8

23.1

140

72.5

no

0.04

7.3

10.5

134.1

99.1

no

0.08

11.3

14.1

118.1

101.2

no

0.16

18.1

17.6

112.4

94.1

no

0.32

-

12.9

-

45.7

yes

*Per 106surviving cells

Solvent control with Ethanol

Table 3 : Results of Mammalian Mutagenicity assay (Test 2) with L5178Y/TK+/ Mouse Lymphoma cells

Concentration µg/ml

Mutant* Frequency

Mutant* Frequency

%Relative Growth.

%Relative Growth.

Cytotoxicity
(yes/no)

 

— MA

+ MA

— MA

+ MA

-

Solvent Control

14

17

100

100

No

Negative Control

25.3

15.8

83.1

89.2

No

Positive Control

385

514

27

2.8**

No

0.04

-

15.4

-

87.8

No

0.08

26.9

22.1

65.7

75.6

No

0.16

27.5

16.5

60.1

48

Yes

0.24

16.5

-

58.6

-

No

0.32

26.6

58

0.2

0.1

Yes

*Per 106surviving cells

Solvent control with Ethanol

**It is noted that this level of toxicity is lower than acceptable under current guidelines.

Conclusions:
Trichloro(methyl)silane was tested for mutagenicity in mammalian cells in a reliable and reproducible assay according to a protocol that is similar to OECD 476. Appropriate concurrent negative and positive controls were included and the expected responses were observed, though the cytotoxicity observed with the positive controls in the with activation experiments was high (2.8% and 5.8%). No test-substance related increase in mutant frequency was observed. It is concluded that trichloro(methyl)silane is negative for the induction of mutation in mammalian cells under the conditions of the test.
Endpoint:
in vitro gene mutation study in mammalian cells
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The restrictions are that the experiment did not include replicate culture, and mouse liver S9 was used for metabolic activation.
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
yes
Remarks:
Insufficient test concentrations / no duplicates
GLP compliance:
no
Type of assay:
mammalian cell gene mutation assay
Target gene:
Thymidine kinase operon
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
mouse liver S9
Test concentrations with justification for top dose:
+/- MA 0.1, 0.2, 0.4, 0.8, 1.6 µl/ml
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethanol
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
(without activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: Dimethylnitrosamine
Remarks:
(with activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: none
- Exposure duration: four hours
- Expression time (cells in growth medium): 3 days
- Selection time (if incubation with a selection agent): 10 days

SELECTION AGENT (mutation assays): medium containing thymidine kinase, hypoxanthine, methotrexate and glycine

NUMBER OF REPLICATIONS: single doses, triplicate counts

DETERMINATION OF CYTOTOXICITY
- Method: cloning efficiency
Evaluation criteria:
A compound is considered mutagenic if there is an increase in the mutant frequency relative to the control, showing a dose response relationship over three of the doses employed, with a minimum increase at the highest dose at least 2.5 times greater than the solvent control value, which should be within the normal range for the TK locus.
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid

Table 1 Mutagenicity in L5178Y cells (mutant frequencies are the mean of three counts)

Concentration µl/ml

-MA

+MA

Mutant frequency

% growth

Mutant frequency

% growth

Solvent control*

3.3

100

6.5

100

Negative control

4.2

80.3

3.0

84.4

0.1

10.9

103.7

12.1

75.0

0.2

15.5

71.1

8.3

64.7

0.4

6.4

58.5

13.6

68.1

0.8

3.9

80.2

14.4

89.6

1.6

4.9

51.5

7.5

50.7

Positive control

485.6

12.9

643.9

2.9

* Solvent control with ethanol

Conclusions:
Triethoxy(methyl)silane has been tested according to a protocol that is similar to OECD 476, without replication. No increase in mutant frequency was observed at any concentration with or without metabolic activation. The solvent and positive controls gave expected results. It is concluded that the test substance is negative for mutagenicity in mouse lymphoma L5178Y cells under the conditions of the test.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Data are available from reliable in vitro studies of bacterial mutagenicity and cytogenicity to mammalian cells for methylsilanetriyl triacetate. No further information is available for the registered substance, however, data are available for the closely related substances triethoxy(methyl)silane (CAS number 2031-67-6) and trichloro(methyl)silane (CAS number 75-79-6) from in vitro assays on mutagenicity to mammalian cells.

Methylsilanetriyl triacetate has been tested for mutagenicity to bacteria in a study which was conducted according to the OECD TG 471, and in compliance with GLP (BioReliance, 2002a). No evidence of a test substance related increase in the number of revertants was observed with or without metabolic activation in the initial or the repeat experiments. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Methylsilanetriyl triacetate has been tested according to OECD 473 and under GLP (BioReliance, 2002b). No increase in the number of chromosome aberrations per cell or the number of cells with aberrations was detected at any concentration with and without metabolic activation in Chinese hamster ovary cells. Solvent and positive controls gave expected results. It is considered that the test substance is negative for the induction of chromosome aberrations under the conditions of the test.

The structural analogue triethoxy(methyl)silane has been tested according to a protocol that is similar to OECD 476, but without replication (Litton Bionetics, 1978a). No increase in mutant frequency was observed at any concentration with or without metabolic activation. The solvent and positive controls gave expected results. It is concluded that the test substance is negative for mutagenicity in mouse lymphoma L5178Y cells under the conditions of the test.

A second structural analogue, trichloro(methyl)silane, was tested for mutagenicity in mammalian cells in a reliable and reproducible assay according to a protocol that is similar to OECD 476 (Litton Bionetics, 1978b). Appropriate concurrent negative and positive controls were included and the expected responses were observed, though the cytotoxicity observed with the positive controls in the experiments with activation was high (2.8% and 5.8%). It is noted by the reviewer that the toxicity of the positive control in the experiments with activation was greater than is acceptable under current guidelines. No test-substance related increase in mutant frequency was observed. It is concluded that trichloro(methyl)silane is negative for the induction of mutation in mammalian cells under the conditions of the test.

No evidence for genetic toxicity was observed in the in vitro studies, so it is considered that in vivo testing is not required.

Justification for classification or non-classification

Based on the available in vitro genotoxicity data, methylsilanetriyl triacetate is not classified for mutagenicity according to Regulation (EC) No 1272/2008.