Registration Dossier

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

All available key data for linear siloxanes have been included to the dataset for the registered substance, L5 (dodecamethylsiloxane, CAS 141-63-9) as weight of evidence to assess the genetic toxicity endpoint.

HMDS: Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2 (similar to OECD TG 471) (Hita Research Laboratories, 1994).

Cytogenicity in mammalian cells: negative in Chinese hamster lung fibroblasts (similar to OECD TG 473) ( Hita Research Laboratories, 1995). Mutagenicity in mammalian cells: negative in L5178Y mouse lymphoma cells (similar to OECD TG 476) (Litton Bionetics, 1978)

L3: Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in Salmonella typhimurium strains TA 98, 100, 1535, 1537 and E.coli WP2 uvrA (OECD TG 471) (Wagner, 2008).

Cytogenicity in mammalian cells: negative with and without metabolic activation in CHO cells (OECD TG 473) (Madraymootoo and Rao, 2008).

L4: Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without activation in Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 and Escherichia coli WP2 uvr A (OECD TG 471) (BioReliance, 2005).

Mutagenicity to mammalian cells: negative with and without activation in L5178Y cells (OECD 476) (Harlan, 2010).


L5: Cytogenicity in mammalian cells: negative with and without activation in Chinese hamster V79 cells (OECD TG 473) (Bioservice, 2014).

Link to relevant study records

Referenceopen allclose all

Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1994-03-24 to 1994-04-11
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
The restrictions were that duplicate plates were used, not triplicate, and 2-amino anthracene was the only control with metabolic activation. An authorised translation was available to the reviewer.
Qualifier:
according to guideline
Guideline:
JAPAN: Guidelines for Screening Mutagenicity Testing Of Chemicals
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
yes
Remarks:
only duplicate plates; 2-AA only control +MA
Principles of method if other than guideline:
E coli Reverse mutation assay
GLP compliance:
yes
Type of assay:
bacterial reverse mutation assay
Target gene:
histidine operon (Salmonella strains); tryptophan operon (E. coli)
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
Metabolic activation:
with and without
Metabolic activation system:
phenobarbital and 5,6-benzoflavone induced rat liver S9
Test concentrations with justification for top dose:
50 to 10000 µg/plate (range-finding);
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: acetone (dehydrated)
- Justification for choice of solvent/vehicle: insoluble in water
Untreated negative controls:
yes
Remarks:
sterility control
Negative solvent / vehicle controls:
yes
Remarks:
acetone
True negative controls:
no
Positive controls:
yes
Positive control substance:
furylfuramide
Remarks:
AF-2: TA98, TA 100 and E. coli WP2 uvrA without metabolic activation: 0.1 µg/plate (TA 98); 0.01 µg/plate (TA 100 and E. coli)
Untreated negative controls:
yes
Remarks:
sterility control
Negative solvent / vehicle controls:
yes
Remarks:
acetone
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
NaN3: TA 1535 without metabolic activation: 0.5 µg/plate
Untreated negative controls:
yes
Remarks:
sterility control
Negative solvent / vehicle controls:
yes
Remarks:
acetone
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-methoxy-6-chloro-9(3-(2-chloroethyl)-aminopropylamino) acridine 1µg/plate
Remarks:
ICR-191: TA 1537 without metabolic activation
Untreated negative controls:
yes
Remarks:
sterility control
Negative solvent / vehicle controls:
yes
Remarks:
acetone
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene: µg/plate: 0.5 (TA 98), 1 (TA 100), 2 (TA1535 and 1537) and 1 (E.coli)
Remarks:
2AA: all strains with metabolic activation
Details on test system and experimental conditions:
METHOD OF APPLICATION: preincubation

DURATION
- Preincubation period: 30 minutes
- Exposure duration: 48 hours

SELECTION AGENT (mutation assays): minimal agar

NUMBER OF REPLICATIONS: duplicate (triplicate for solvent controls); range-finding and main experiments evaluated.

DETERMINATION OF CYTOTOXICITY
- Method: other: condition of bacterial lawn; reduction in number of revertants

OTHER: ACTIVATION: S9 mix included glucose-6-phosphate, NADP and NADPH as cofactors, and 10% S9. 1.5 ml S9 mix was added to 0.3 ml of bacteria and 0.15 ml test substance -concentration of S9 was therefore approximately 7.5% during pre-incubation.
Evaluation criteria:
The test substance was judged positive if the number of revertants was more than twice the negative control, and the response was dose-dependent and reproducible.
Key result
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2
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:
valid
Positive controls validity:
valid

Table 1a Dose range finding test revertants per plate (mean of 2 plates)

Concentration µg/plate

TA 100

TA 1535

E. coli WP2 uvrA

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

0*

135

141

no

15

15

no

42

48

no

50

123

129

no

11

16

no

43

46

no

100

121

127

no

15

19

no

43

50

no

200

132

125

no

10

16

no

47

56

no

500

127

121

no

14

16

no

44

51

no

1000

118

117

no

13

19

no

47

53

no

2000

123

127

no

13

19

no

46

50

no

5000

129

108

no

9

19

no

39

49

no

10000

123

123

no

13

20

no

52

53

no

Positive control

539

1026

-

420

306

-

508

457

-

* Solvent control with acetone, mean of three plates

Table 1b Dose range finding test revertants per plate (mean of 2 plates)

Concentration µg/plate

TA 98

TA 1537

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

0*

27

31

no

11

19

no

50

26

29

no

8

18

no

100

28

31

no

8

16

no

200

27

33

no

10

19

no

500

33

27

no

6

19

no

1000

29

31

no

10

17

no

2000

24

32

no

11

13

no

5000

31

33

no

11

20

no

10000

32

32

no

9

12

no

Positive control

621

301

-

1581

203

-

* Solvent control with acetone, mean of three plates

Table 2a Main test revertants per plate (mean of 2 plates)

Concentration µg/plate

TA 100

TA 1535

E. coli WP2 uvrA

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

0*

128

133

no

16

17

no

46

52

no

313

122

128

no

14

11

no

50

46

no

625

129

129

no

13

12

no

43

48

no

1250

140

125

no

16

15

no

42

48

no

2500

124

121

no

11

13

no

38

49

no

5000

137

127

no

13

14

no

41

51

no

10000

144

133

no

13

16

no

40

50

no

Positive control

645

1042

-

445

273

-

547

492

-

* Solvent control with acetone, mean of three plates

Table 2b Main test revertants per plate (mean of 2 plates)

Concentration µg/plate

TA 98

TA 1537

-MA

+MA

Cytotoxic

-MA

+MA

Cytotoxic

0*

25

35

no

11

17

no

313

24

33

no

10

13

no

625

24

32

no

10

15

no

1250

26

31

no

12

14

no

2500

30

34

no

10

15

no

5000

22

40

no

10

10

no

10000

29

40

no

13

14

no

Positive control

627

318

-

1303

233

-

* Solvent control with acetone, mean of three plates

Conclusions:
Hexamethyldisiloxane has been tested according to a Japanese guideline that is similar to OECD 471 and under GLP, using the pre-incubation method. No evidence of test-substance induced increase in the number of revertants was observed in Salmonella typhimurium strains TA1535, TA1537, TA98, TA100 or E. coli WP2 uvrA, with or without metabolic activation, up a concentration exceeding current limit concentrations in either the dose finding test or the main assay. Appropriate solvent, positive and sterility 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 substance.
Endpoint:
in vitro gene mutation study in mammalian cells
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
The restrictions were that the test concentrations were not duplicated.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
yes
Remarks:
no duplicates
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:
0.0125, 0.025, 0.05, 0,1, 0.2 µl/ml
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethanol
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

SELECTION AGENT (mutation assays): BUdR

NUMBER OF REPLICATIONS: no replicates

DETERMINATION OF CYTOTOXICITY
- Method: other: loss of growth potential
Evaluation criteria:
A substance is considered mutagenic if there is a dose response relationship over 3 dose levels; minimum increase at high level of dose response is at least times greater than the solvent control value; solvent control data are within normal range of spontaneous background mutation rates.
Statistics:
No statistical analysis was carried out.
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
at 0.2 µl/ml, equivalent to approximately 200 µg/ml
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid
Additional information on results:
Preliminary cytotoxicity testing indicated toxicity at > 0.2 µl/ml
Several scattered increases were thought by the authors to be the result of spurious fluctuations and cytotoxicity.

Table 1 Summary of mouse lymphoma mutagenicity results

Test substance concentration µl/ml   Activation   Relative growth %    Mutant frequency x 10E-06
 Solvent control  -MA  100  23.7
 Negative control  -MA  87.7  17.2
 Positive control  -MA  20.3  515.5
 0.0125  -MA   86.8   18.5
 0.025  -MA  73.1  15.8
 0.05  -MA  92.3  22.3
 0.1  -MA  62.0  9.5
 0.2  -MA  29.5  28.1
 Solvent control  +MA  100  29.9
 Negative control  +MA  94.9  23.1
 Positive control  +MA  25.1  196.0
 0.0125  +MA  90.4  42.1
 0.025  +MA  68.4  26.3
 0.05  +MA  72.5  40.3
 0.1  +MA  90.4  21.1
 0.2  +MA  0.1  50.7
Conclusions:
Hexamethyldisiloxane has been tested for mutagenicity in L5178Y cells in a valid and reliable study according to a protocol that is similar to OECD TG 476. The test substance did not cause a biologically significant increase in the mutation frequency; solvent and positive controls gave expected results. It is concluded that the test substance is not mutagenic under the conditions of the test.
Endpoint:
in vitro gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2007-12-28 - 2008-01-23
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
GLP compliance:
yes (incl. QA statement)
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:
50, 150, 500, 1500 and 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Acetone
- Justification for choice of solvent/vehicle: none given
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene 1 µg/plate
Remarks:
TA98, TA100, TA1535 and TA1537 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 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:
2-nitrofluorene
Remarks:
TA98 without metabolic activation: 1 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 and TA1535 without metabolic activation: 1 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 10% S9, and glucose-6-phosphate and NADP as co-factors. 0.5 ml S9 mix was added to 2.0 ml top agar giving a final concentration of approximately 2% S9.
DURATION
- Exposure duration: 48 - 72 hours

NUMBER OF REPLICATIONS: experiment 1 - duplicate plates, experiment 2 - triplicate plates


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



Evaluation criteria:
A result is positive if the mean of each positive control exhibits 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 were required to evaluate assay data. Strains TA1535 and TA1537 were judged positive if there was a 3-fold increase in the number of revertants compared with the mean vehicle control value and a 2-fold increase for Salmonella typhimurium strains TA98, TA100 and E. coli WP2 uvrA.
Statistics:
None stated 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
Additional information on results:
TEST-SPECIFIC CONFOUNDING FACTORS


COMPARISON WITH HISTORICAL CONTROL DATA: Historical negative and positive control values included in report

ADDITIONAL INFORMATION ON CYTOTOXICITY: Cytotoxicity was not evident at any concentration

Plate incorporation – average number of revertants per plate (mean of 2 plates).

Experiment 1

Treatment µg/plate

TA98

TA100

TA1535

TA1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

Solvent control

 15

 13

147

164

 16

 13

   4

  8

 21

 18

1.5

 17

 13

160

147

 18

 12

   6

  6

 18

 18

5.0

 16

 14

164

175

 19

   9

   1

  8

 22

 24

15

 16

 17

140

120

 15

 11

   8

  4

 19

 14

50

 13

 14

177

156

 17

 13

   6

  5

 19

 21

150

 15

 18

155

156

 22

 12

   7

  6

 24

 24

500

 12

 15

172

171

 15

 12

   8

  9

 24

 18

1500

 14

 17

149

153

 11

   7

   4

  9

 23

 20

5000

 14

 16

179

175

 15

   9

   7

  5

 21

 21

Positive control

144

454

540

553

369

121

923

131

166

242

 

Plate incorporation – average number of revertants per plate (mean of 3 plates).

Experiment 2

Treatment µg/plate

TA98

TA100

TA1535

TA1537

WP2 uvrA

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

-S9

+S9

Solvent control

 31

  17

183

184

 20

 17

   10

   8

 23

 23

50

 18

  18

189

173

 16

 16

     6

 10

 21

 19

150

 28

  16

199

172

 16

 18

   11

 11

 27

 24

500

 24

  12

171

180

 12

 18

   11

   7

 25

 20

1500

 26

  17

189

193

 18

 16

     6

 10

 22

 25

5000

 28

  19

167

198

 16

 20

     6

 10

 20

 23

Positive control

194

 666

607

660

436

125

1154

185

127

278

 

Conclusions:
Octamethyltrisiloxane has been tested for mutagenicity to bacteria in a study which was conducted according to OECD 471, and in compliance with GLP. No evidence of a test substance related increase in the number of revertants was observed with or without activation in the initial or the repeat experiments with Salmonella typhimurium strains TA 98, 100, 1535, 1537 and E.coli WP2 uvrA. Appropriate positive and solvent controls were tested 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 gene mutation study in bacteria
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
2005-09-15 to 2005-10-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Version / remarks:
1998
Deviations:
no
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 induced rat liver S9
Test concentrations with justification for top dose:
50, 150, 500, 1500, 5000 µg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: Ethanol

- 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:
other: 2-aminoanthracene
Remarks:
All salmonella strains + WP2 uvrA (with activation)
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 activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
TA 100, TA 1535 (without activation)
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 activation)
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
WP2 uvrA (without activation)
Details on test system and experimental conditions:
METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Expression time (cells in growth medium): 48 - 72 hours

NUMBER OF REPLICATIONS: 3 plates for each test concentration

DETERMINATION OF CYTOTOXICITY
- Method: relative total growth; observation of background lawn density.

METABOLIC ACTIVATION: Aroclor induce rat liver S9; S9 mix included glucose-6-phophate and NADP as co-factors. 0.5ml of 10% S9 was added to 2 ml of top agar, 0.1 ml of tester strain and 0.05 ml of vehicle or test article giving a final concentration of approximately 2%.

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 WP2 uvrA and 3-fold of the solvent control for TA 1535 and TA 1537. There must be a dose related increase in the mean
revertants per plate of at least one tester strain over a minimum of 2 increasing concentrations of test article.

Cytotoxicity is defined as a reduction in the number of colonies by >50% compared with the solvent control and/or at least a moderate reduction in
the background lawn (background code 3, 4 or 5).
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

Table 2a:  Toxicity and mutagenicity assay - plate incorporation (mean of 2 plates)

 

TA98

TA100

TA1535

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

26

22

No

161

145

No

25

25

No

1.5

23

24

No

130

134

No

26

20

No

5

17

22

No

126

152

No

22

17

No

15

15

25

No

107

125

No

16

23

No

50

14

27

No

108

128

No

17

29

No

150

17

24

No

124

153

No

24

18

No

500

23

23

No

133

148

No

21

21

No

1500

16

20

No

115

129

No

27

20

No

5000

21

20

No

135

128

No

25

18

No

Positive Control

173

488

No

557

565

No

342

78

No

*solvent control with ethanol

Table 2b:  Toxicity and mutagenicity assay - plate incorporation (mean of 2 plates)

 

TA1537

WP2 uvrA

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

11

9

No

28

13

No

1.5

8

8

No

17

25

No

5

8

8

No

22

19

No

15

7

8

No

27

17

No

50

6

5

No

20

19

No

150

7

8

No

22

24

No

500

7

7

No

16

24

No

1500

9

6

No

18

17

No

5000

8

10

No

22

17

No

Positive Control

871

62

No

141

203

No

*solvent control with ethanol

Table 3: Experiment 2 - preincubation Number of revertants per plate (mean of 3 plates)

 

TA98

TA100

TA1535

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

 MA

+ MA

Cytotoxic
(yes/no)

MA

+ MA

Cytotoxic
(yes/no)

0*

18

24

No

84

84

No

16

21

No

50

15

19

No

80

72

No

17

20

No

150

15

26

No

51

97

No

15

19

No

500

17

21

No

78

81

No

19

24

No

1500

23

25

No

67

90

No

17

24

No

5000

15

24

No

80

103

No

20

21

No

Positive control

96

124

No

283

279

No

184

64

No

*solvent control with ethanol

Table 3: Experiment 2 - preincubation Number of revertants per plate (mean of 3 plates)

 

TA1537

WP2 uvrA

Conc.
µg/plate

— MA

+ MA

Cytotoxic
(yes/no)

— MA

+ MA

Cytotoxic
(yes/no)

0*

9

9

No

25

20

No

50

7

7

No

18

26

No

150

5

9

No

23

21

No

500

8

5

No

20

16

No

1500

7

3

No

21

18

No

5000

8

7

No

20

17

No

Positive control

505

29

No

124

104

No

*solvent control with ethanol

Conclusions:
Decamethyltetrasiloxane has been testing in a reliable study conducted according to OECD 471 1998 and under GLP up to limit concentrations. No increase in the number of revertants was observed at any concentration with and without metabolic activation in Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2 uvrA in either the initial plate incorporation assay or the independent repeat experiment which used the pre-incubation method. It is considered that the test substance was 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:
weight of evidence
Study period:
11 August 2009 to 14 September 2009
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Type of assay:
mammalian cell gene mutation assay
Species / strain / cell type:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Metabolic activation system:
phenobarbital and beta-naphthoflavone-induced rat liver S9
Test concentrations with justification for top dose:
12.5-200 µg/ml (4h) and 1.56-50 µg/ml (24h)
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: ethanol;
- Justification for choice of solvent/vehicle: none given in study report
Untreated negative controls:
no
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
without metabolic activation: 400 µg/ml (4 h exposure), 150 µg/ml (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 metabolic activation: 2 µg/ml
Details on test system and experimental conditions:
METHOD OF APPLICATION: in medium

DURATION
- Exposure duration: 4 h (with and without metabolic activation); 24 h (without metabolic 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

NUMBER OF REPLICATIONS: duplicate cultures

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

OTHER EXAMINATIONS:
- Other: number of small and large colonies

OTHER: a preliminary toxicity assay was conducted up to a concentration of 3107 µg/ml (10 mM)
Evaluation criteria:
For a test material to demonstrate a mutagenic response it must produce a reproducible and dose-dependent statistically significant increase in the induced mutant frequency (IMF) over the concurrent vehicle mutant frequency value, exceeding the Global Evaluation Factor (GEF) value of 126 E10-06.
Statistics:
UKEMS statistical package used.
Key result
Species / strain:
mouse lymphoma L5178Y cells
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Remarks:
RTG 16% at 37.5 µg/ml (24h))
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: no marked change in pH was observed
- Effects of osmolality: did not increase by more than 50 mOsm
- Precipitation: a non interfering precipitate of the test material observed at and above 100 μg/ml in the absence of metabolic activation, and at and above 150 μg/ml in the presence of metabolic activation.
- Other confounding effects: none

RANGE-FINDING/SCREENING STUDIES: No dose-related toxicity was observed following 4 h exposure; marked toxicity was observed in the 24 h exposure group.

COMPARISON WITH HISTORICAL CONTROL DATA: Control results were within the range of historical controls

TOXICITY: The toxicity observed in the main experiment differed from that in the preliminary cytotoxicity test. No explanation of this is given in the report.

Table 1 Preliminary toxicity test

Concentration (μg/ml)

 

% RSG (-S9)

4-Hour Exposure

 

% RSG (+S9)

4-Hour Exposure

 

% RSG (-S9)

24-Hour Exposure

 

0

100

100

100

12.14

74

96

72

24.27

90

96

26

48.55

83

84

0

97.09

100

68

0

194.19

95

82

1

388.38

94

102

1

776.75

108

98

1

1553.5

100

102

4

3107

97

82

39

%RSG= Relative Suspension Growth

 

Table 2 Summary of results from main experiment, 4 h exposure

Treatment

(μg/ml)

 

4-Hours-S-9

Treatment

(μg/ml)

 

4-Hours+S-9

 

%RSG

RTG

MF

%RSG

RTG

MF

0

100

1.00

89.99

0

100

1.00

114.53

12.5

112

1.29

89.46

12.5

113

1.04

91.57

25

111

1.28

82.23

25

106

1.20

95.58

50

121

1.42

89.78

50

102

1.05

101.72

100 P

110

1.28

79.77

100

105

1.09

93.79

150 P

109

1.28

86.92

150 P

104

1.10

88.74

200 P

122

1.38

86.12

200 P

106

1.17

98.22

Linear trend NS

Linear trend NS

Positive control

94

0.81

710.52

2

65

0.29

935.61

P Precipitate observed at the end of the exposure period.

* Not plated for viability or 5-TFT resistance

%RSG = Relative Suspension Growth

RTG = Relative Total Growth

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

 

Table 3 Summary of results from main experiment, 24 h exposure

Treatment

(μg/ml)

 

24-Hours-S-9

%RSG

RTG

MF

0

100

1.00

96.68

1.56 *

109

 

 

3.13

102

0.95

108.38

6.25

101

1.29

76.85

12.5

104

1.21

113.47

18.75

89

1.02

93.93

25

59

0.69

89.82

37.5

16

0.14

141.03

50 *

9

 

 

Linear trend NS

Positive control

92

0.69

992.94

* Not plated for viability or 5-TFT resistance

%RSG = Relative Suspension Growth = [(dose SG x dose Day 0 Factor)/vehicle control SG] x 100

P(0) = number of negative wells/total wells plated

2 day viability %V = (-lnP(0) x 100)/number of cells/well

RCE = Relative Cloning Efficiency = (%V/mean solvent control %V)x100%

RTG = Relative Total Growth = (RCE x RSG)/100%

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

Conclusions:
Decamethyltetrasiloxane has been tested according to OECD TG 476 and under GLP conditions for mutagenicity to mouse lymphoma L5178Y cells up to cytotoxic concentrations. No increase in mutant frequency was detected at any concentration after 4h exposure with and without metabolic activation and 24 h exposure without metabolic activation. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of mutations in L5178Y cells 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
Study period:
8 February 2012 to 5 November 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)
Version / remarks:
1997
Qualifier:
according to guideline
Guideline:
EU Method B.10 (Mutagenicity - In Vitro Mammalian Chromosome Aberration Test)
Version / remarks:
2008
Qualifier:
according to guideline
Guideline:
EPA OPPTS 870.5375 - In vitro Mammalian Chromosome Aberration Test
Version / remarks:
1998
GLP compliance:
yes (incl. QA statement)
Type of assay:
in vitro mammalian chromosome aberration test
Species / strain / cell type:
Chinese hamster lung fibroblasts (V79)
Details on mammalian cell type (if applicable):
- Type and identity of media:
MEM medium supplemented with:
10 % foetal bovine serum (FBS)
100 U/100 µg/mL Penicillin/Streptomycin solution
2 mM L-glutamine
0.25 mg/mL Amphotericin
25 µM HEPES

- Properly maintained: yes
- Periodically checked for Mycoplasma contamination: yes
- Periodically checked for karyotype stability: no data
- Periodically "cleansed" against high spontaneous background: no data
Metabolic activation:
with and without
Metabolic activation system:
phenobarbital and β naphthoflavone induced rat liver S9
Test concentrations with justification for top dose:
0-10 mM
Vehicle / solvent:
ethanol
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
ethylmethanesulphonate
Remarks:
without metabolic activation
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
cyclophosphamide
no
Remarks:
with metabolic activation
Details on test system and experimental conditions:
ACTIVATION: Phenobarbital (80 mg/kg bw) and β naphthoflavone (100 mg/kg bw) induced rat liver S9 was included in the S9 mix to a final protein concentration of 0.75 mg/ml. Cofactors were added to the following concentrations: 8 mM MgCl2; 33 mM KCl; 5 mM Glucose-6-phosphate; 5 mM NADP.

METHOD OF APPLICATION: in medium;

DURATION

- Exposure duration: 4 hours (Experiment I, +/- MA, Experiment II +MA); 20 hours (Experiment II -MA).

- Expression time (cells in growth medium): 20 hours (Experiment I +/- MA and Experiment II +MA).

SPINDLE INHIBITOR (cytogenetic assays): Colcemid

STAIN (for cytogenetic assays): Giemsa

NUMBER OF REPLICATIONS: Experiments I and II: Stock cultures in exponential growth were seeded into Quadriperm dishes containing at four slides. Two days after seeding the culture medium was replaced with test item suspension (with S9 mix as appropriate). The slides were divided into sets of two and at least one slide from each set was counted. The experiment was repeated. In experiment III duplicate cultures were treated at each concentration and 100 metaphases were scored per culture.

NUMBER OF CELLS EVALUATED: At least 200 well spread metaphases (100 per slide), containing 22+/- 1 centromeres, per concentration and validity controls were scored for cytogenetic damage.

NUMBER OF CELLS EVALUATED: At least 200 well spread metaphases (100 per slide in experiments I and II, 100 per culture in experiment III), containing 22+/- 1 centromeres, per concentration and validity controls were scored for cytogenetic damage.

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; relative cell density

OTHER EXAMINATIONS:
- Determination of polyploidy: yes
Evaluation criteria:
A positive result is determined by: a clear and dose-related increase in the number of cells with aberrations; a biologically relevant response for at least one of the dose groups, which is higher than the laboratory negative control range (0.0% - 4.0% aberrant cells)
Species / strain:
Chinese hamster lung fibroblasts (V79)
Metabolic activation:
with and without
Genotoxicity:
negative
Remarks:
increased percentage of cells with aberrations, not dose dependent or reproducible
Cytotoxicity / choice of top concentrations:
no cytotoxicity nor precipitates, but tested up to recommended limit concentrations
Remarks:
some reduction in Mitotic index observed at limit concentration
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
Positive controls validity:
valid

Results of chromosome aberration assay

Concentration mM Set  cells scored Chromatid types Chromosome types Polyploid cells (mean) MI % (mean) mean aberrant cells
b f d ex if id cx inc gaps exc gaps
Experiment I, without metabolic activation; 4h treatment, 20 h fixation
Negative control 1 100 2 0 0 0 1 0 0 0.5 100 3.5 3
2 100 1 0 0 0 0 0 2
Solvent control 1 100 1 0 0 0 0 0 0 0.5 100 1.5 0.5
2 100 0 0 0 0 0 0 0
2.5 1 100 0 1 0 0 0 0 0 1 90 2 1.5
2 100 0 0 0 0 0 0 1
5* 1 100 2 1 1 0 0 0 0 0 89 5 3.5
2 100 1 0 1 0 0 0 1
10 1 100 1 0 0 0 0 0 1 0.5 98 3.5 1.5
2 100 0 0 1 0 0 0 0
Positive controls 1 100 6 0 0 1 0 0 0 0.5 72 10 8
2 100 6 0 1 3 0 0 0
Experiment I, with metabolic activation; 4h treatment, 20 h fixation
Negative control 1 100 2 0 0 1 0 0 0 1 96 3 2
2 100 0 0 1 1 0 0 0
Solvent control 1 100 1 0 0 0 0 0 0 2.5 100 1.5 1
2 100 0 0 0 0 0 0 1
2.5 1 100 0 0 0 0 0 0 0 0 78 1 0
2 100 0 0 0 0 0 0 0
5 1 100 0 0 0 0 0 0 0 0 85 4 1.5
2 100 3 0 0 1 0 0 0
10 1 100 0 0 0 0 0 0 1 0 76 1.5 1
2 100 1 0 0 0 0 0 0
Positive controls 1 100 7 0 0 5 0 0 0 0.5 79 10.5 10
2 100 16 0 0 4 0 0 0
Experiment II, without metabolic activation; 20h treatment, 20 h fixation
Negative control 1 100 2 1 0 0 1 0 0 0.5 111 6.5 3
2 100 2 0 0 0 0 0 0
Solvent control 1 100 0 0 0 0 0 0 0 0 100 3.5 0.5
2 100 1 0 0 0 0 0 0
0.125 1 100 3 0 0 0 0 0 0 0 95 5 2
2 100 0 0 1 0 0 0 0
7.5 1 200 1 0 1 1 0 0 0 0.5 103 3.5 2.3
2 200 5 0 1 0 0 0 0
10 1 200 4 3 1 2 1 0 0 0.75 108 4.3 3.3
2 200 2 11 0 0 0 0 0
Positive controls** 1 100 9 1 0 2 0 0 1 0.5 88 12.5 10.5
2 100 4 1 0 6 0 0 0
Experiment II, with metabolic activation; 4h treatment, 20 h fixation
Negative control 1 100 1 1 0 0 0 0 0 0 96 5.5 2.5
2 100 2 0 0 0 0 0 1
Solvent control 1 100 2 0 0 0 0 0 0 1 100 2.5 1
2 100 0 0 0 0 0 0 0
4 1 100 7 0 0 1 0 0 0 0 72 8.5 6
2 100 4 0 0 0 0 0 1
7 1 200 6 0 0 0 0 0 0 0.75 83 5.8 3.3
2 200 4 1 2 0 1 0 0
10* 1 200 7 0 0 0 0 0 0 0.5 84 6.8 4.8
2 200 11 2 0 1 0 0 0
Positive controls 1 100 5 0 0 9 0 0 0 0.5 88 12.5 11
2 100 4 1 0 4 0 0 0

Experiment III, with metabolic activation; 4h treatment, 20 h fixation

Negative control

1

100

0

0

0

0

0

0

0

0

69

4.0

1.0

2

100

4

0

0

1

0

0

0

Solvent control

1

100

0

0

0

1

0

0

0

0

63

2.5

1.0

2

100

1

0

0

0

0

0

0

2.5

1

100

1

0

0

0

0

0

0

0

81

3.5

1.0

2

100

1

0

0

0

0

0

0

5.0

1

100

1

0

0

0

0

0

1

0

75

3.0

1.5

2

100

1

0

0

0

0

0

0

10

1

100

0

0

1

1

0

0

0

0

67

3.0

1.5

2

100

0

0

1

0

0

0

0

Positive controls**

1

100

4

1

0

1

0

0

0

0

90

9.0

7.5

2

100

6

0

0

4

0

0

0

* one cd at this concentration; ** one ma at this concentration; *** one ib at this concentrationb/ib break/isobreak f/if fragment/isofragment d/id deletion/isodeletion ex chromatid exchange cx chromosome exchange cd chromosome deletion ma multiple aberration (>4 events including gaps)

Conclusions:
Dodecamethylpentasiloxane has been tested according to OECD 473 and in compliance with GLP. An increase in the number of aberrations was observed in the second experiment with metabolic activation but the response was not clearly dose related or reproducible. In a third experiment with metabolic activation there was no increase in the number of aberrations. Therefore, dodecamethylpentasiloxane was considered to be non-clastogenic under the conditions of the test.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Genetic toxicity in vivo

Description of key information

HMDS: Mammalian Bone Marrow Chromosome Aberration Test in rat (ip study) (similar to OECD TG 475): Negative (Dow Corning Corporation, 1982).

Link to relevant study records
Reference
Endpoint:
in vivo mammalian somatic cell study: cytogenicity / bone marrow chromosome aberration
Type of information:
experimental study
Adequacy of study:
weight of evidence
Study period:
1980-11-26 to 1981-09-28
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
It was not compliant with GLP.
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)
Deviations:
yes
Remarks:
only male animals used. Number of cells counted for determination of mitotic index not indicated - probably ca. 100, should be 1000
Principles of method if other than guideline:
The test was performed according to the Rodent Bone Marrow Cytogenetic Assay as recommended by the Ad Hoc Committee on Chromosome Methodologies in Mutagen Testing (Toxicology and Applied Pharm 22: 269-275, 1972) with modifications per the EPA Gene-Tox Program Cytogenetics Committee (12/3 to 12/5, 1980, Washington D.C.).
GLP compliance:
not specified
Type of assay:
chromosome aberration assay
Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals or test system and environmental conditions:
TEST ANIMALS

- Age at study initiation: 14 - 16 weeks

- Weight at study initiation: 250 - 280 g for range finding. 290 - 430 g for cytogenetic study

- Housing: 6 per cage

- Diet (e.g. ad libitum): Charles River Agway

ENVIRONMENTAL CONDITIONS

- Temperature (°C): 68 ± 3 F

- Humidity (%): approx 50
Route of administration:
intraperitoneal
Vehicle:
- Vehicle(s)/solvent(s) used: paraffin oil

- Lot/batch no. (if required): A7M02

- Purity: Laboratory Grade
Duration of treatment / exposure:
single treatment
Frequency of treatment:
Single IP injection
Post exposure period:
6, 24 and 48 hours
Dose / conc.:
255 mg/kg bw/day (nominal)
Dose / conc.:
515 mg/kg bw/day (nominal)
Dose / conc.:
1 030 mg/kg bw/day (nominal)
No. of animals per sex per dose:
5 males/dose
Control animals:
yes, concurrent vehicle
Positive control(s):
cyclophosphamide, positive control agent, was included in the 24-hour group.  

- Route of administration: IP Injection

- Doses / concentrations: 22 mg/kg bw
Tissues and cell types examined:
Bone marrow from femur
Details of tissue and slide preparation:
CRITERIA FOR DOSE SELECTION: Based on two range finding studies conducted to determine the maximum dose the animals could tolerate.


Range finding studies: Range finding study 1: Animals Injected intraperitoneally with 1676, 504, 168 and 50 mg/kg and observed once a day for 7 days for signs of toxicity. Range finding study 2: 10 animals injected with 3911, 1825, 521, 183 and 52 mg/kg. In main study animals were sacrificed at 6, 24 and 48 hours


DETAILS OF SLIDE PREPARATION: Approximately 4 slides were prepared for each animal.  The chromosomes were prepared by standard methods and Giemsa stained.


TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):
6h group: Stock solution of 321 mg/ml; volumes injected were 1.0, 0.5 and 0.25 ml, resulting in the following doses calculated from body weight: 1030 mg/kg +/- 3.2%; 515 mg/kg +/- 5.6%; 255 mg/kg +/- 1.2%

24 hour group: animals were injected with 1.0 or 0.5 ml of 321 mg/ml stock solution, or 1.0 ml of 91 mg/ml stock solution, resulting in the following doses calculated from body weight: 1030 mg/kg +/- 0.8%; 515 mg/kg +/- 5.6%; 255 mg/kg +/- 3.1%

48 hour group: animals were injected with 1.0 or 0.45 ml of 426 mg/ml stock solution, or 1 ml of 102 mg/ml stock solution. This resulted in the following doses calculated from body weight: 1030 mg/kg +/- 3.1%; 515 mg/kg +/- 9.3%; 255 mg/kg +/- 2.4%

METHOD OF ANALYSIS: metaphase cells analysed by projecting the negatives with a darkroom enlarger onto a white counter

OTHER:
Evaluation criteria:
In general, a minimum of 100 metaphase cells from each animal were scored for incidence of chromosomal aberrations.
Statistics:
Statistical methods: Chi2 test for comparison of expected and observed distribution of the number of breaks; Wilcoxon test was used as a nonparametric test.
Key result
Sex:
male
Genotoxicity:
negative
Remarks:
on mitotic index
Toxicity:
no effects
Vehicle controls validity:
valid
Negative controls validity:
not applicable
Positive controls validity:
valid
Additional information on results:
RESULTS OF RANGE-FINDING STUDY

- Dose range: Exp 1: 1676, 504, 168, 50 mg/kg. Exp 2: 3911, 1825, 521, 183, 52 mg/kg

- Clinical signs of toxicity in test animals: No deaths observed in initial study. In second study 3 of 10 animals dosed with 3911 mg/kg died, while all the other animals survived till terminal sacrifice.

- Harvest times: 7 days exp 1, 14 days exp 2.

- High dose with and without activation: 1676 exp 1, 3911 exp 2

RESULTS OF DEFINITIVE STUDY

See table 1

Negative controls: frequencies of breaks were 0.54%, 2.49% and 1.47% at sacrifice at 6, 24 and 48 hours respectively.

Table 1:Results of chromosome analysis in rat bone marrow cells: test substance (total number of aberrations observed)

 

Low dose (255 mg/kg bw)

Mid dose (515 mg/kg bw)

High dose (1030 mg/kg bw)

Sampling time (h)

6

24

48

6

24

48

6

24

48

Number of cells evaluated

 500 approx

 500 approx

 500 approx

 500 approx

 500 approx

 500 approx

 500 approx

 500 approx

 500 approx

Toxicity,specify effects

 

 

 

 

 

 

 

 

 

Chromosome aberrations

Gaps

6

11

3

3

6

25

 2

 12

 14

Breaks

 5

 2

 9

 10

 15

 6

 5

 6

 7

Other aberrations

 0

 0

 0

 0

 0

 0

 0

 0

Mitotic index (% range)

 2 – 5

2 - 5

1 - 4

 2 - 4

 2 - 5

 4 - 7

 1 - 6

 3 - 5

 2 - 5

Polyploidy

N.R

N.R

N.R

N.R

N.R

N.R

N.R

N.R

N.R

Endo reduplication

N.R

N.R

N.R

N.R

N.R

N.R

N.R

N.R

N.R

 N.R = Not Reported

Table 2 Results of chromosome analysis in rat bone marrow cells: control substances (total number of aberrations observed)

 

Vehicle control

Positive control

Sampling time (h)

6

24

48

48

Number of cells evaluated

 500 approx

 450 approx

 500 approx

 250 approx

Chromosome aberrations

Gaps

6

19

15

ND

 

Breaks

3

12

8

145

 

Other aberrations

0

0

0

4 quad, 6 tri, 5 del

Mitotic index (% range)

 

2-7

1-4

3-4

2-4

 N.R = Not Reported

quad = quadriradial tri = triradial del = deletion

Conclusions:
Hexamethyldisiloxane has been tested for the induction of chromosome aberrations in rat bone marrow cells in a valid study conducted according to a protocol that is similar to OECD 475. There was no evidence of induction of chromosomal damage in the bone marrow cells of rats following intraperitoneal injection. The test substance is considered to be non-clastogenic (negative for the induction of chromosome aberrations) in rat bone marrow cells under the conditions of the test.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

All available key data for linear siloxanes have been included to the dataset for the registered substance, L5 (dodecamethylsiloxane, CAS 141-63-9) as weight of evidence to assess bacterial and mammalian mutagenicity endpoints. There are key mammalian cytogenicity data available for L5, therefore data for the other linear siloxanes have been included as supporting for consistency and to support read across justifications.

HMDS

Bacterial mutagenicity

HMDS (hexamethyldisiloxane, CAS 107-46-0) has been tested according to a Japanese guideline that is similar to OECD Test Guideline 471 and in compliance with GLP, using the pre-incubation method (Hita Research Laboratories, 1994). The study is considered to be reliability 2 as duplicate not triplicate plates were used. No evidence of test-substance induced increase in the number of revertants was observed in Salmonella typhimurium strains TA1535, TA1537, TA98, TA100 or E.coli WP2 uvrA, with or without metabolic activation, up to a concentration exceeding current limit concentrations, in either the dose finding test or the main assay. Appropriate solvent, positive and sterility 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 substance.

In vitro cytogenicity

HMDS (hexamethyldisiloxane, CAS 107-46-0) has been tested in compliance with GLP in a valid Japanese guideline study according to a protocol that is similar to OECD Test Guideline 473 (Hita Research Laboratories, 1995). The test substance did not induce any chromosome aberrations with or without metabolic activation. There were no marked differences between replicate flasks. Expected results were obtained from vehicle and positive controls. It is concluded that the test substance is non-clastogenic (does not induce chromosome aberrations) in Chinese hamster lung cells under the conditions of the test.

Mutagenicity to mammalian cells

HMDS (hexamethyldisiloxane, CAS 107-46-0) has been tested for mutagenicity in L5178Y cells in reliability 2 study conducted according to a protocol that is similar to OECD Test Guideline 476 but prior to GLP implementation (Litton Bionetics, 1978). The test substance did not cause a biologically significant increase in the mutation frequency; solvent and positive controls gave expected results. It is concluded that the test substance is not mutagenic under the conditions of the test.

In vivo

The conclusion reached from the in vitro results is confirmed by the negative result obtained when L2 (hexamethyldisiloxane, CAS 107-46-0) was tested in vivo in a rat bone marrow chromosome aberration assay conducted according to a protocol that is similar to OECD Test Guideline 475 using intraperitoneal administration. The test substance was considered to be non-clastogenic (negative for the induction of chromosome aberrations) in rat bone marrow cells under the conditions of the test (Dow Corning Corporation, 1982). In addition, hexamethyldisiloxane does not include structural alerts for genetic toxicity (Benigni et. al., 2008). It is concluded that the available data does not indicate a potential for germ cell mutagenicity.

L3

Bacterial mutagenicity

L3 (octamethyltrisiloxane, CAS 107-46-0) has been tested for mutagenicity to bacteria in a study which was conducted according to OECD Test Guideline 471 and in compliance with GLP (BioReliance, 2008a). No evidence of a test substance related increase in the number of revertants was observed with or without activation in the initial or the repeat experiments with Salmonella typhimurium strains TA 98, 100, 1535, 1537 and E.coli WP2 uvrA. Appropriate positive and solvent controls were tested and gave expected results. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Mammalian cytogenicity

Information on the potential of L3 (octamethyltrisiloxane, CAS 107-46-0) for clastogenicity to mammalian cells is available from a reliable in vitro cytogenetic assay conducted according to OECD Test Guideline 473 and in compliance with GLP (BioReliance, 2008b). The test substance did not induce statistically and biologically significant increases in the chromosomal aberration frequency in CHO cells. 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 in vitro (is not clastogenic) under the conditions of the test.

L4

Bacterial mutagenicity

L4 (decamethyltetrasiloxane, CAS 141-62-8) has been testing in a reliable study conducted according to OECD Test Guideline 471 (1998) and in compliance with GLP up to cytotoxic concentrations. The original study was considered reliability 1. Read-across to the registered substance is considered scientifically justified and is reliability 2. No increase in the number of revertants was observed at any concentration with and without metabolic activation in Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA 1537 and E. coli WP2 uvrA in either the initial plate incorporation assay or the independent repeat experiment which used the pre-incubation method. It is considered that the test substance was negative for mutagenicity to bacteria under the conditions of the test (BioReliance, 2005).

Mammalian mutagenicity

L4 (decamethyltetrasiloxane, CAS 141-62-8) has been tested according to OECD Test Guideline 476 and in compliance with GLP conditions for mutagenicity to mouse lymphoma L5178Y cells up to cytotoxic concentrations (Harlan, 2010). No increase in mutant frequency was detected at any concentration after 4h exposure with and without metabolic activation and 24 h exposure without metabolic activation. Appropriate solvent and positive controls were included and gave expected results. It is concluded that the test substance is negative for the induction of mutations in L5178Y cells under the conditions of the test.

L5

Mammalian cytogenicity

L5 (dodecamethylpentasiloxane, CAS 141-63-9) has been tested according to OECD TG 473 and in compliance with GLP (Bioservice, 2014). The final draft report was available to the reviewer. An increase in the number of aberrations was observed in the second experiment after 4 hours exposure with metabolic activation but the response was not clearly dose related or reproducible. In a third experiment, following a 4 hour exposure with metabolic activation, there was no increase in the number of aberrations. Appropriate solvent and positive controls were included and gave expected results. It is concluded that dodecamethylpentasiloxane is non-clastogenic in Chinese hamster V79 cells under the conditions of the test under the conditions of the test.


Justification for classification or non-classification

Based on the available data for dodecamethylpentasiloxane and the read-across substances hexamethyldisiloxane (HMDS; CAS 107-46-0), octamethyltrisiloxane (L3; CAS 107-51-7) and decamethyltetrasiloxane (L4; CAS 141-62-8), dodecamethylpentasiloxane does not require classification for mutagenicity according to Regulation (EC) No. 1272/2008.