Registration Dossier

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (Bacterial reverse mutation assay / Ames test): S. typhimurium TA 1535, TA 1537, TA 98, TA 100, and TA 102: negative with and without metabolic activation (according to OECD 471)

No data about mammalian mutagenicity or mammalian cytogenicity are available with the trimethoxy(2,4,4 -trimethylpentyl)silane. Reliable read across data from triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) and triethoxyoctylsilane (CAS 2943-75-1) were used.

Mammalian cytogenicity (Chinese hamster V79 cell chromosome aberration assay, RA from CAS 35435 -21 -3): negative with and without metabolic activation (according to OECD 473)
Mammalian Mutagenicity (Mouse Lymphoma Assay (TK locus), RA from CAS 2943-75-1): negative with and without metabolic activation (according to OECD TG 476)

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:
09 April 2002 to 01 July 2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1998
Deviations:
no
GLP compliance:
yes (incl. certificate)
Remarks:
FREIE UND HANSESTADT HAMBURG, BEHÖRDE FÜR ARBEIT, GESUNDHEIT UND SOZIALES, Hamburg (Germany)
Type of assay:
bacterial reverse mutation assay
Target gene:
his-operon
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
- Test 1: 100, 316, 1000, 3160 and 5000 µg/plate (plate incorporation test)
- Test 2: 3.16, 10, 31.6, 100 and 316 µg/plate (preincubation test)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethylene glycol dimethylether
- Justification for choice of solvent/vehicle: Solubility properties and relative non-toxicity to bacteria
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
2-nitrofluorene
sodium azide
cyclophosphamide
methylmethanesulfonate
other: +S9: 2-anthracene amide (TA 98, TA 102, TA 1537; 2µg/plate)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION
- Preincubation period: 60 minutes
- Expression time (cells in growth medium): 48 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration in 2 independent experiments

DETERMINATION OF CYTOTOXICITY
- Method: Background lawn assessment, revertant colony counts (only TA 100)

ACTIVATION: Aroclor induced rat liver S9 had a protein content of 32.92 mg/ml. the S9 mix included 5% S9 and glucose-6-phosphate and NADP as co-factors. 0.5 ml S9 mix was added to 2 ml top agar, 0.1 ml of cell suspension and 0.1 ml test material (or solvent or positive control), giving a final concentration of approximately 1% S9
Evaluation criteria:
A result is positive if the number of revertants is significantly increased compared with the solvent control to at least 2-fold of the solvent control for TA 98, TA 100 and TA 102 and 3-fold of the solvent control for TA 1535 and TA 1537 in both experiments.

Positive results have to be reproducible and the histidine independence of the revertants has to be confirmed by streaking on histidine-free agar plates.

Cytotoxicity is defined as a reduction in the number of colonies by >50% compared with the solvent control and/or a sparse background lawn.
Statistics:
MANN and WHITNEY and Spearman’s rank.

Species / strain:
S. typhimurium, other: S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and TA 102
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
from 100 µg/plate in TA 100 ±S9, and 316 µg/plate in TA 98 and TA 100 ±S9 and in TA 1535 and TA 1537 -S9.
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
COMPARISON WITH HISTORICAL CONTROL DATA: Results were within range of historical control data

Table 1: Dose range-finding study: number of revertants per plate (2 plates)

 

TA 100

Conc.
(µg/plate)

Plate 1

Plate 2

Cytotoxic
(yes/no)

0*

132

175

No

0.316

150

195

No

1

127

125

No

3.16

169

152

No

10

138

135

No

31.6

164

149

No

100

128

133

No

316

154

126

No

1000

133

174

No

3160

151

140

No

5000

163

167

Yes

*solvent control with Ethylene glycol dimethylether

Table 2: Experiment 1 Plate incorporation: number of revertants per plate (mean of 3 plates)

 

TA 98

TA 100

TA 102

Conc.
(
µg/plate)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

0*

26.7±7.6

30.3±4.5

No

123.3±10.1

167.7±7.4

No

302.0±8.7

287.3±14.8

No

100

24.0±2.6

47.7±5.5

No

151.7±19.7

147.3±8.0

No

240.3±17.6

245.7±9.9

No

316

30.7±8.5

34.7±2.1

No

150.7±9.3

151.0±2.6

No

234.7±6.4

225.0±19.1

No

1000

20.3±3.8

34.0±3.0

No

159.3±1.2

144.7±3.2

No

226.3±29.9

245.7±17.9

No

3160

26.0±7.0

35.3±4.7

No

204.0±7.2

158.7±4.5

No

248.7±35.6

224.0±22.3

No

5000

24.0±6.2

28.7±3.2

No

192.7±15.9

173.3±10.4

Yes

259.3±23.9

206.3±20.6

Yes

Positive control

331.3±23.7

343.7±2.5

No

1091.3±37.8

1061.3±14.4

No

1087.7±12.0

1159.3±70.9

No

*solvent control with ethylene glycol dimethylether

Table 2: Experiment 1 Plate incorporation: number of revertants per plate (mean of 3 plates)

 

TA 1535

TA 1537

Conc.
(
µg/plate)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

0*

19.0±4.4

16.3±1.5

No

9.3±1.5

11.7±0.6

No

100

17.7±5.9

14.3±4.0

No

9.7±2.1

11.7±3.8

No

316

19.0±7.0

15.0±4.6

No

7.7±3.1

12.0±2.0

No

1000

17.3±3.2

17.3±2.3

No

11.0±1.0

13.7±1.5

No

3160

17.7±0.6

19.3±5.7

No

9.0±2.0

15.0±2.6

No

5000

19.0±1.7

15.3±6.7

No

11.3±2.5

14.0±3.6

No

Positive control

387.0±7.2

393.7±1.2

No

1000.0±5.2

986.0±3.5

No

*solvent control with ethylene glycol dimethylether

Table 3: Experiment 2 Preincubation: number of revertants per plate (mean of 3 plates)

 

TA 98

TA 100

TA 102

Conc.
(
µg/plate)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

0*

26.7±9.0

34.7±2.5

No

125.0±14.8

119.3±8.7

No

291.0±7.5

280.3±13.3

No

3.16

31.3±2.1

31.7±11.4

No

133.0±12.1

117.3±15.9

No

291.3±1.5

267.7±27.4

No

10

28.7±2.5

30.7±5.5

No

186.7±3.1

127.3±8.5

No

263.7±11.2

260.7±7.4

No

31.6

39.3±16.2

31.7±4.5

No

155.7±8.1

106.0±9.6

No

265.3±0.6

278.0±28.6

No

100

28.3±5.0

31.0±4.0

No

144.3±15.5

124.0±2.6

No

0.0±0.0

270.3±16.3

Yes

316

33.7±3.5

30.0±1.0

Yes

113.7±7.5

112.7±8.4

Yes

0.0±0.0

0.0±0.0

Yes

Positive control

855.7±22.7

924.0±54.7

No

1003.0±7.5

926.0±119.7

No

1165.3±6.1

1200.7±77.6

No

*solvent control with ethylene glycol dimethylether

Table 3: Experiment 2 Preincubation: number of revertants per plate (mean of 3 plates)

 

TA 1535

TA 1537

Conc.
(
µg/plate)

- MA

+ MA

Cytotoxic
(yes/no)

- MA

+ MA

Cytotoxic
(yes/no)

0*

12.0±1.0

14.7±2.1

No

5.7±3.8

10.0±1.0

No

3.16

14.0±3.6

15.0±1.7

No

6.7±2.5

6.7±1.5

No

10

14.7±0.6

12.3±4.2

No

7.3±3.2

10.3±1.5

No

31.6

14.0±4.0

15.0±2.6

No

5.3±1.2

9.3±2.1

No

100

12.3±1.5

12.7±2.1

No

6.3±1.5

7.7±1.5

No

316

16.0±1.0

0.0±0.0

Yes

10.3±1.5

0.0±0.0

Yes

Positive control

632.0±6.1

581.7±46.3

No

617.0±4.6

423.3±86.4

No

*solvent control with ethylene glycol dimethylether

Conclusions:
Interpretation of results: negative with and without metabolic activation

The test item has been tested in a reliable study conducted according to the OECD TG 471 and in compliance with GLP. No test-substance related increase in the number of revertants was observed when tested with and without metabolic activation up to cytotoxic concentration in Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100 and TA 102 in either the initial plate incorporation assay or the independent repeat experiment using the pre-incubation method. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.
Endpoint:
genetic toxicity in vitro, other
Remarks:
chromosome aberration in mammalian cells; gene mutation in mammalian cells
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the attached justification
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
500 μg/ml (exp 2, 20 h treatment without activation)
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
with S9: growth inhibition starting at 1 mM (I) and 2.0 mM (II), but not dose-dependent; without S9: concentration related increase starting at 1.0 mM (I) and 0.1 mM (II)
Vehicle controls validity:
valid
Untreated negative controls validity:
not applicable
Positive controls validity:
valid
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

No data about in vivo genetic toxicity is available with the trimethoxy(2,4,4 -trimethylpentyl)silane. Reliable read across data from triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) was used.

Chromosome aberration (micronucleus assay, RA from CAS 35435-21-3): negative (according to OECD 474)

Link to relevant study records
Reference
Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the attached justification
Reason / purpose:
read-across source
Sex:
male/female
Genotoxicity:
negative
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Information is available from a bacterial mutagenicity study on trimethoxy(2,4,4-trimethylpentyl)silane (CAS 34396-03-7). No further information is available for the registered substance, however, reliable data are available for the closely related substances, triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) and triethoxyoctylsilane (CAS 2943-75-1). The silicon-containing products of hydrolysis are close structural analogues: both trimethoxy(2,4,4-trimethylpentyl)silane (CAS 34396-03-7) and triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) hydrolyse to (2,4,4-trimethylpentyl)silanetriol; the second analogous substance triethoxyoctylsilane (CAS 2943-75-1) hydrolyses to octylsilanetriol. All three substances hydrolyse very rapidly: hydrolysis is expected to occur during testing and following exposure. The further products of hydrolysis are methanol and ethanol, respectively. It is therefore considered appropriate to read-across the in vitro mammalian mutagenicity from triethoxyoctylsilane (CAS 2943-75-1) and, in vitro mammalian cytogenicity and in vivo micronucleus results from triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) to the registered substance.

In vitro genotoxicity

In the available key study trimethoxy(2,4,4-trimethylpentyl)silane has been tested for bacterial mutagenicity according to the OECD TG 471, and in compliance with GLP (LPT, 2002). No test-substance related increase in the number of revertants was observed when tested with and without metabolic activation up to cytotoxic concentration in Salmonella typhimurium strains TA 1535, TA 1537, TA 98, TA 100, and TA 102 in either the initial plate incorporation assay or the independent repeat experiment using the pre-incubation method. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test. Appropriate solvent and positive controls were included and gave expected results.

This result is supported by two further reliable bacterial mutagenicity studies (RCC, 1998 and General Laboratory, 2004). Negative results were obtained in both of these studies with and without metabolic activation.

 

In the available key study triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) has been tested for cytogenicity according to the OECD TG 473, and in compliance with GLP (Bioservice, 2001). The test substance did not induce structural chromosomal aberrations in the V79 Chinese hamster cell line with and without metabolic activation up to limit concentrations. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of chromosome aberrations under the conditions of the test.

 

In the available key study triethoxyoctylsilane (CAS 2943-75-1) has been tested for mammalian mutagenicity according to the OECD TG 476, and in compliance with GLP (Bioservice, 2012). The test substance did not induce gene mutation (thymidine kinase locus) in mouse lymphoma L5178Y cells with and without metabolic activation. 2 experiments (4 and 24 h exposure) were performed with and without metabolic activation. Tetrahydrofurane was used as vehicle. No increase in mutant frequency was seen at any concentration compared to the negative controls (solvent and sterility controls). Dose-related cytotoxicity was observed from 1 mM and 0.1 mM (experiment I and II, respectively) without metabolic activation. With metabolic activation cytotoxicity was seen from 1 mM or 2 mM (experiment I and II, respectively) but was not dose-related. The positive controls (ethylmethanesulfonate, methylmethanesulfonate, -S9; benzo[a]pyrene, +S9) gave the expected values. No indication for potential clastogenic effects and/or chromosomal aberrations was seen.

 

In vivo genotoxicty

In the available key study triethoxy(2,4,4-trimethylpentyl)silane (CAS 35435-21-3) has been tested in the in vivo mouse micronucleus assay according to the OECD TG 474, and in compliance with GLP (Bioservice, 2001). No statistically significant increase in the number of cells with micronuclei was observed after oral administration of the limit dose of 2000 mg/kg bw. Appropriate positive and vehicle controls were included and gave expected results. The PCE / NCE ratio was slightly affected in treated males, indicating that the test item was of low toxicity to the target tissue. It is concluded that the test substance is negative for the induction of micronuclei under the conditions of the test.

Justification for classification or non-classification

The available in vitro and in vivo genotoxicity data are reliable and suitable for classification. Based on this data, classification for mutagenicity according to Regulation 67/584/EEC and (EC)1272/2008 is not warranted.