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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

A bacterial mutagenicity study ( LPT Laboratory of Pharmacology and Toxicology, 2002) is the only genetic toxicity study available for dichloro(methyl)(phenyl)silane. Existing results for in vitro mammalian mutagenicity (Harlan Laboratories Ltd, 2010) and in vivo cytogenicity (micronucleus study, Dow Corning Corporation , 1991) have therefore been read across from the closely related structural analogues trichlorophenylsilane (CAS 98-13-5) and dimethoxy(methyl)phenylsilane (CAS 3027-21-2).

Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in all strains tested (OECD TG 471)
Mutagenicity in mammalian cells: negative in L5178Y mouse lymphoma cells (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:
04.03.2002 - 04.09.2002
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)
Version / remarks:
1992
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay
Target gene:
Histidine
Species / strain / cell type:
other: TA 1537, TA 102, TA 98, TA 1535, TA 100
Metabolic activation:
with and without
Metabolic activation system:
Aroclor induced rat liver S9
Test concentrations with justification for top dose:
Experiment 1: 10 - 1000 µg/plate; Experiment 2: 1 - 100 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Abs. ethylene glycol dimethylether
- Justification for choice of solvent/vehicle: Solvent was chosen because of its solubility properties and its relative non-toxicity to the bacteria.
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
TA 1535, TA 100 without metabolic activation conc 10 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
2-nitrofluorene
Remarks:
TA 98 without metabolic activation conc 10 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
TA 102 without metabolic activation conc 1300 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
9-aminoacridine
Remarks:
TA 1537 without metabolic activation conc 100 µg/plate
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-Anthracene amide 2 µg/plate
Remarks:
TA 98, TA 102, TA 1537 with metabolic activation
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
Remarks:
TA 100, TA 1535 with metabolic activation 1500 µg/plate
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation); preincubation

DURATION
- Preincubation period: 60 minutes
- Exposure duration: 48 hours

SELECTION AGENT (mutation assays): Histidine deficient agar

NUMBER OF REPLICATIONS: Triplicate plates: independent repeat experiment


DETERMINATION OF CYTOTOXICITY
- Method: other: Inhibition of background lawn and greater than 50% reduction in the number of revertants

Evaluation criteria:
A chemical is considered positive if it shows a statistically significant dose dependent and reproducible increase in the number of revertants relative to the solvent control.
Statistics:
Mann and Whitney U-test and Spearman's rank correlation coefficient
Key result
Species / strain:
other: TA98, TA100, TA102, TA1536, TA1537
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
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS
- Effects of pH:
- Effects of osmolality:
- Evaporation from medium:
- Water solubility:
- Precipitation: None
- Other confounding effects:



COMPARISON WITH HISTORICAL CONTROL DATA: The results for solvent and positive controls fall within the range of the historical controls

Plate incorporation test

Treatment µg/plate

       TA 98

 

TA 100

TA 102

TA 1535

TA 1537

- S9

+ S9

- S9

+ S9

- S9

+ S9

- S9

+ S9

- S9

+ S9

0

34.0

44.3

142.0

160.3

262.0

279.3

13.7

13.3

4.3

4.0

10

37.7

44.0

145.3

137.3

262.0

276.3

12.0

12.7

3.0

3.7

31.6

34.7

44.3

130.0

131.3

264.0

282.3

13.7

12.3

3.3

2.7

100

42.7

40.3

133.0

137.3

273.0

289.3

11.7

12.0

3.0

4.3

316

41.7

36.3

136.3

126.0

258.0

280.3

13.0

12.7

3.0

3.0

1000

39.7

47.7

151.0#

155.3

294.3

289.7

13.0

12.7

3.3

3.3

Pos con

1031.0

1032.7

1359.3

1345.7

1364.3

1363.3

620.3

995.7

1072.3

1072

 

 

 

 

Pre-incubation test

Treatment µg/plate

       TA 98

 

TA 100

TA 102

TA 1535

TA 1537

- S9

+ S9

- S9

+ S9

- S9

+ S9

- S9

+ S9

- S9

+ S9

0

42.7

53.3

160.7

172.0

275.7

299.3

13.3

15.0

6.0

6.3

1

34.3

41.3

174.7

157.7

261.0

281.0

14.3

13.0

7.0

7.7

3.16

54.7

39.3

168.7

168.3

284.7

271.7

14.0

14.3

6.3

6.7

10

30.3

42.3

169.7

146.7

267.7

256.0

12.0

16.3

6.3

7.3

31.6

36.3

50.3

181.7

155.0

278.0

272.7

13.7

12.7

7.0

6.3

100

26.0#

0.0#

153.3#

177.7#

269.0#

298.0

14.7#

13.7#

5.0#

8.0#

Pos con

758.7

969.7

1284.3

1324.0

1267.0

1236.3

327.3

347.7

353.3

350.7

 

# = scarce background lawn

Conclusions:
Dichloro(methyl)(phenyl)silane has been tested in a reliable bacterial mutagenicity assay according to OECD TG 471 and under GLP. The test substance did not induce an increase in the number of revertants in either the initial plate incorporation assay or the repeat pre-incubation assay. Solvent and positive controls gave the expected results. It is concluded that the test substance is negative for mutagenicity to bacteria 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
Study period:
2009-09-18 to 2009-11-09
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)
Version / remarks:
2008
Deviations:
no
GLP compliance:
yes
Type of assay:
mammalian cell gene mutation assay
Target gene:
Thymidine kinase
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
Phenobarbital/beta-naphthoflavone-induced rat liver S9
Test concentrations with justification for top dose:
200 to 900 µg/ml (4h + S9, 24h -S9); 300 to 1000 µg/ml (4 h -S9)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: tetrahydrofuran
- Justification for choice of solvent/vehicle: none given in report
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
without activation 400 and 150 2 µg/ml for 4 and 24 h exposure
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
Remarks:
with activation 2 µg/ml
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: none
- Exposure duration: 4h (with and without activation); 24 hours (without activation)
- Expression time (cells in growth medium): 2 days
- Selection time (if incubation with a selection agent): 10-14 days

SELECTION AGENT (mutation assays): 5 trifluorothymidine
STAIN: blue tetrazolium bromide (MTT) was used to assist the scoring of the TFT mutant colonies.

NUMBER OF REPLICATIONS: duplicate treatments

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth; other: 2 day viability

OTHER EXAMINATIONS:
- Other: number of small and large colonies
Evaluation criteria:
A statistically significant increase in the induced mutant frequency (IMF) over the concurrent vehicle control was considered positive if it exceeded the control mutant frequency by the global evaluation factor (GEF Moore et al 2003) of 126 x 10 E-06. Such a response was only considered positive if it was also dose related and reproducible. Judgement was used if a reproducible increase was less than the GEF.
Statistics:
The experimental data was analysed using a dedicated computer program which follows the statistical guidelines recommended by the UKEMS.
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
900 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: reduction of 3 pH units was observed in solubility test at 2116 µg/ml., so maximum dose was 1058 µg/ml.
- Effects of osmolality: no increase.
- Precipitation: observed at and above 600 µg/ml in 24 hour exposure group.

RANGE-FINDING/SCREENING STUDIES: reduction in relative total growth was observed in screening study.

COMPARISON WITH HISTORICAL CONTROL DATA: solvent controls were within the range of historical control data.

ADDITIONAL INFORMATION ON CYTOTOXICITY: There was no evidence of any significant reductions in (%V) viability in either the absence or presence of metabolic activation, therefore indicating that no residual toxicity had occurred. Optimum levels of toxicity were achieved in both the absence and presence of metabolic activation. Acceptable levels of toxicity were seen with both positive control substances .

Table 1 Preliminary toxicity test

Dose

(µg/ml)

%(-S9)

4-Hour Exposure

%(+S9)

4-Hour Exposure

%(-S9)

24-Hour Exposure

0

100

100

100

4.13

88

90

108

8.27

91

107

93

16.53

99

102

120

33.06

98

85

114

66.13

91

106

111

132.25

91

96

105

264.5

86

104

107

529

93

82

67

1058

2

3

0

RSG Relative suspension growth

Table 2 Main Experiment, 4 hour treatment

Treatment

(µg/ml)

4-Hours-S-9

Treatment

(µg/ml)

4-Hours+S-9

 

%

RTG

MF

 

%

RTG

MF

0

100

1.00

115.75

0

100

1.00

108.95

300

98

 

 

200

105

 

 

400

101

0.93

106.73

300

99

 

 

500

96

0.92

103.74

400

91

0.90

130.49

600

92

0.90

88.67

500

85

0.81

128.14

700

89

0.89

95.54

600

68

0.71

109.32

800

62

0.54

89.91

700

79

0.81

102.91

900

16

0.19

113.22

800

71

0.68

116.23

1000

1

 

 

900

21

0.22

140.40

Linear trend

ns

Linear trend

NS

EMS

 

 

 

CP

 

 

 

400

91

0.67

931.52

2

60

0.36

1238.85

Table 3 Main Experiment, 24 h treatment

Treatment

(µg/ml)

24-Hours-S-9

 

%

RTG

MF

0

100

1.00

104.29

200

102

1.03

116.21

300

93

0.99

110.28

400

77

0.84

129.29

500

61

0.50

108.65

600

9

0.10

110.97

700

9

0.10

91.37

800

0

 

 

900

0

 

 

Linear trend

 

NS

EMS

 

 

 

150

84

0.66

1165.73

RSG Relative Suspension Growth

RTG Relative Total Growth

MF 5-TFT resistant mutants/106viable cells 2 days after treatment

EMS Ethylmethanesulphonate

CP Cyclophosphamide

NS Not significant

Conclusions:
Trichloro(phenyl)silane has been tested in a reliable study according to OECD TG 476 and under GLP. No increase in mutant frequency was observed at any concentration with and without activation (4 hours treatment) and without activation (24 hours treatment). Expected results were obtained with positive and negative controls. It is concluded that trichloro(phenyl)silane is negative for the induction of mutations in L5178Y cells under the conditions of the test.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

A bacterial mutagenicity study ( LPT Laboratory of Pharmacology and Toxicology, 2002) is the only genetic toxicity study available for dichloro(methyl)(phenyl)silane. Existing results for in vitro mammalian mutagenicity (Harlan Laboratories Ltd, 2010) and in vivo cytogenicity (micronucleus study, Dow Corning Corporation , 1991) have therefore been read across from the closely related structural analogues trichlorophenylsilane (98-13-5) and dimethoxy(methyl)phenylsilane (CAS 3027-21-2).

Mammalian Bone Marrow Chromosome Aberration Test (ip study) in rat (OECD TG 413 with additional micronucleus investigations)

Link to relevant study records
Reference
Endpoint:
in vivo mammalian somatic cell study: cytogenicity / erythrocyte micronucleus
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1991-05-07 to 1991-05-27
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The restrictions were that less detail was given than is usual in a standard micronucleus study, and there was no positive control.
Qualifier:
according to
Guideline:
other: OECD 413
Deviations:
no
Principles of method if other than guideline:
Micronucleus data were gathered as part of a 14-day repeated-dose inhalation study, no positive control was included.
GLP compliance:
yes
Type of assay:
micronucleus assay
Species:
rat
Strain:
Sprague-Dawley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS

- Source: not stated

- Age at study initiation: 5 - 7 weeks

- Weight at study initiation: 100 - 160 g

- Assigned to test groups randomly: yes, under following basis: using Xybion ASLECT program

- Housing: suspended, steel, wire mesh bottom cages.

- Diet (e.g. ad libitum): ad libitum

- Water (e.g. ad libitum): ad libitum

ENVIRONMENTAL CONDITIONS

- Temperature (°F): 68 - 73 °F

- Humidity (%): 30 - 70 %

- Air changes (per hr): 12 - 15

- Photoperiod (hrs dark / hrs light): 12 hours dark / 12 hours light
Route of administration:
inhalation: vapour
Details on exposure:
TYPE OF INHALATION EXPOSURE: whole body

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION

- Exposure apparatus: 450 litre stainless steel whole body exposure chambers

- Source and rate of air: filtered room air

- Method of conditioning air: filtered with hepa and charcoal filters

- System of generating particulates/aerosols: test material introduced into chambers via special designed glass J-tubes, metered with FMI lab pumps. Glass beads and heating tape were used to help vaporize the test material.

- Air change rate: 12 - 15 air changes per hour
Duration of treatment / exposure:
Six hours/day
Frequency of treatment:
daily, 5 days a week for 2 weeks.
Post exposure period:
None
Dose / conc.:
50 ppm (nominal)
No. of animals per sex per dose:
5
Control animals:
yes, concurrent no treatment
Positive control(s):
none
Tissues and cell types examined:
Bone marrow
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: limit dose

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields): no further information

DETAILS OF SLIDE PREPARATION: centrifuged cells were suspended in a thin layer of serum, and a small drop was smeared on a slide and air dried overnight. The cells were fixed in methanol for 5 minutes.

METHOD OF ANALYSIS: microscopic examination. 2000 PCE scored for the incidence of polychromatic erythrocytes with micronuclei.

Statistics:
% Micronucleated PCE'S mean of 2000 per animal and mean ratio of PCE:NCE calculated with standard deviation. Data was analysed by a two-sided Welch trend test. If a significant overall trend was detected, then all follow up tests were one-sided and in the same direction as the overall trend. All tests were conducted at the 0.05 level of significance.
Key result
Sex:
male/female
Genotoxicity:
negative
Toxicity:
yes
Remarks:
reduction in PCE:NCE ratio relative to control
Vehicle controls validity:
valid
Negative controls validity:
valid
Positive controls validity:
not examined

Table 3: Results of in vivo micronucleus test with Dow X2-2614

Exposure concentration (ppm)

0

50

Number of cells evaluated

2000

2000

Sampling time (d)

14 d

14 d

Number of erythrocytes

normo­chromatic

NR

NR

poly­chromatic

2000

2000

% Micronucleated PCE’S (mean of 2000 per animal)

Male

 0.07

Female 0.15

Male

0.12

Female

0.05

Ratio of erythro­cytes

polychromatic / normochromatic

Male

1.8

Female

3.28

Male

1.12

Female

0.98

polychromatic with micro­nuclei / normochromatic

NR

NR

 

Conclusions:
The substance was tested in an in vivo micronucleus assay in rat (performed as part of a 14-day repeat dose inhalation toxicity study to OECD 413 and in compliance with GLP. It was not genotoxic under the conditions of the test.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

An in vitro bacterial mutagenicity study ( LPT Laboratory of Pharmacology and Toxicology, 2002) is the only genetic toxicity study available for dichloro(methyl)(phenyl)silane. Existing results for in vitro mammalian mutagenicity (Harlan Laboratories Ltd, 2010) and in vivo cytogenicity (micronucleus study, Dow Corning Corporation, 1991) have therefore been read across from the closely related structural analogues trichlorophenylsilane (CAS 98-13-5) and dimethoxy(methyl)phenylsilane (CAS 3027-21-2). In all studies results were negative, both with and without metabolic activation where relevant.

Dichloro(methyl)(phenyl)silane (CAS 149-74-6) has been tested in a reliable bacterial mutagenicity assay according to OECD TG 471 and under GLP. The test substance did not induce an increase in the number of revertants in either the initial plate incorporation assay or the repeat pre-incubation assay. Solvent and positive controls gave the expected results.  It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Trichloro(phenyl)silane (CAS 98-13-5) has been tested in a reliable study according to OECD TG 476 and under GLP. No increase in mutant frequency was observed at any concentration with and without activation (4 hours treatment) and without activation (24 hours treatment). Expected results were obtained with positive and negative controls. It is concluded that trichloro(phenyl)silane is negative for the induction of mutations in L5178Y cells under the conditions of the test.

Trichloro(phenyl)silane (CAS 98-13-5) was also concluded to be negative for mutagenicity to bacteria when tested with or without metabolic activation (Dow Corning Corporation, 1985).

Dimethoxy(methyl)phenylsilane (CAS 3027-21-2) was tested in an in vivo micronucleus assay in rat (performed as part of a 14-day repeat dose inhalation toxicity study to OECD 413 and in compliance with GLP.  It was not genotoxic under the conditions of the test.

Dimethoxy(methyl)phenylsilane (CAS 3027-21-2) was also concluded to be negative for mutagenicity to bacteria when tested with or without metabolic activation up to cytotoxic concentrations (Dow Corning Corporation, 1997).

Justification for classification or non-classification

Based on the available in vitro and in vivo genotoxicity data, dichloro(methyl)(phenyl)silane is not classified for mutagenicity according to Regulation (EC) No 1272/2008.