Dodecamethylcyclohexasiloxane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation (Bacterial reverse mutation assay / Ames test): negative with and without metabolic activation in Salmonella typhimurium strains TA1535, TA1537, TA100 and TA98 and Escherichia coli WP2 uvrA (OECD Test Guideline 471) (NOTOX, 1999f).
Cytogenicity in mammalian cells: not required: in vivo micronucleus study available
Mutagenicity in mammalian cells: negative with and without metabolic activation in mouse lymphoma L5178Y cells (OECD Test Guideline 476) (WIL Research, 2015a).

Link to relevant study records

Reference

Reference 1

Endpoint:

in vitro gene mutation study in bacteria

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

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Target gene:

histidine (s. typhimurium) or tryptophan (E. coli) operon

Species / strain / cell type:

bacteria, other: Salmonella typhimurium (TA1535, TA1537, TA100 and TA98) and Escherichia coli (WP2uvrA

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9.

Test concentrations with justification for top dose:

10, 33, 100, 333, and 1000 µg/plate

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:

sodium azide

Remarks:

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:

other: daunomycin

Remarks:

TA 98 without activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

TA 100 without activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

E coli WP2 uvrA without activation

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

All strains with activation

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation)

DURATION
- Exposure duration: 48 hours
- Expression time (cells in growth medium): 48 hours
- Fixation time (start of exposure up to fixation or harvest of cells): 48 hours

NUMBER OF REPLICATIONS: Triplicate plates, in each of two independent experiments

DETERMINATION OF CYTOTOXICITY
- Method: mitotic index; cloning efficiency; relative total growth; other: reduction in number of revertants and condition of bacterial lawn.

OTHER: Range finding study was conducted as part of first experiment - 8 concentrations of TA 100 and E coli WP2uvrA were tested in triplicate

ACTIVATION: Aroclor induced rat liver S9. S9 mix included co-factors: NADP and glucose-6-phosphate; sodium phosphate buffer and magnesium chloride and potassium chloride. S9 mix included S9 at 5% v/v for experiment I and 10% v/v for experiment II). 0.5 ml S9 mix was added to the top agar (total volume 2.7 ml) giving a final concentration of S9 of approximately 1% in experiment I and approximately 2% in experiment II.

Evaluation criteria:

A reproducible, dose-related increase by at least two fold in the number of revertants relative to the control was considered positive.

Key result

Species / strain:

bacteria, other: Salmonella typhimurium (TA1535, TA1537, TA100 and TA98) and Escherichia coli (WP2uvrA)

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity nor precipitates, but tested up to recommended limit concentrations

Remarks:

Tested to precipitating concentrations in experiment II and in some strains in experiment I.

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS

- Precipitation: occurred at concentrations of > 1000 µg/plate

RANGE-FINDING/SCREENING STUDIES: no toxicity observed

COMPARISON WITH HISTORICAL CONTROL DATA: Results of controls were within the ranges of historical controls

The test substance precipitated on the plates at 1000 µg/plate.  The bacterial background lawn was not reduced at all concentrations tested and no decrease in the number of revertants was observed. The test substance did not induce a
dose-related increase in the number of revertant (His+) colonies in each of the four tester strains (TA1535, TA1537,
TA98 and TA100) and in the number of revertant (Trp+) colonies in the tester strain WP2uvrA both in the absence
and presence of S9-metabolic activation.  These results were confirmed in an independently repeated experiment.

Table 1a Experiment II Number of revertants per plate (mean of 3 plates)

Strain	TA 1535			TA 1537			TA 98
Concentration µg/plate	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity
Positive control	283	354	-	244	372	-	124	895	-
Solvent control	19	16	-	6	10	-	13	16	-
10	15	16	no	8	8	no	15	12	no
33	16	19	no	5	6	no	13	14	no
100	16	19	no	9	7	no	12	14	no
333	17	16	no	7	7	no	12	16	no
1000*	18	22	no	6	5	no	12	14	no

* Precipitate

Table 1b Experiment I Number of revertants per plate (mean of 3 plates)

Concentration µg/plate	TA 100			E coli WP2uvrA
	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity
Positive control	964	1754	-	323	91	-
Solvent control	97	94	-	11	7	-
3	115	111	no	8	7	no
10	120	92	no	8	9	no
33	110	114	no	7	9	no
100	102	106	no	8	5	no
333	88	118	no	6	6	no
1000*	108	126	no	4	8	no
3330*	94	101	no	8	7	no
5000*	92	124	no	8	12	no

* Precipitate

Table 2a Experiment II Number of revertants per plate (mean of 3 plates)

Concentration µg/plate	TA 1535			TA 1537			TA 98
	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity
Positive control	152	277	-	575	247	-	132	924	-
Solvent control	5	10	-	4	4	-	15	21	-
10	11	12	no	3	7	no	14	25	no
33	11	11	no	4	8	no	16	22	no
100	11	12	no	3	4	no	15	26	no
333	10	9	no	4	7	no	16	23	no
1000*	11	9	no	5	6	no	15	28	no

* Precipitate

Table 2b Experiment II Number of revertants per plate (mean of 3 plates)

Concentration µg/plate	TA 100			E coli WP2uvrA
	- S9	+ S9	Cytotoxicity	- S9	+ S9	Cytotoxicity
Positive control	965	1722	-	386	152	-
Solvent control	84	95	-	7	9	-
10	93	109	no	9	10	no
33	85	97	no	9	14	no
100	83	106	no	8	8	no
333	83	109	no	10	12	no
1000*	73	101	no	6	8	no

* Precipitate

Conclusions:

Dodecamethylcyclohexasiloxane has been tested in a reliable study conducted in accordance with OECD Test Guideline 471 and in compliance with GLP. No evidence of test substance induced increase in the number of revertants was observed when the substance was tested in the presence and absence of metabolic activation in Salmonella typhimurium strains TA1535, TA1537, TA100 and TA98 and Escherichia coli WP2uvrA, in either the initial or the independent repeat experiment. Appropriate solvent and positive controls were included and gave expected responses. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

Reference 2

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:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 476 (In Vitro Mammalian Cell Gene Mutation Test)

Version / remarks:

1997

Qualifier:

according to guideline

Guideline:

EU Method B.17 (Mutagenicity - In Vitro Mammalian Cell Gene Mutation Test)

Version / remarks:

2008

Qualifier:

according to guideline

Guideline:

other: International Workshop on Genotoxicity Tests Workgroup published in Clive et al. 1995, Moore et al., 1999, 2000, 2002, 2003, 2006 and 2007

GLP compliance:

yes (incl. QA statement)

Type of assay:

mammalian cell gene mutation assay

Target gene:

thymidine kinase

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

Source: American Type Culture Collection, (ATCC, Manassas, USA) (2001).

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital (80 mg/kg body weight) and ß-naphthoflavone (100 mg/kg) (100 mg/kg) induced rat liver S9

Test concentrations with justification for top dose:

0.056, 0.18, 0.55, 1.7, 5.4, 17, 52 and 164 μg/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethanol
- Justification for choice of solvent/vehicle: A solubility test was performed in culture medium, dimethyl sulfoxide and ethanol. The substance was soluble in ethanol.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

-MA

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

cyclophosphamide

Remarks:

+MA

Details on test system and experimental conditions:

ACTIVATION:
Concentration of S9-fraction in the exposure medium was 4% (v/v)

METHOD OF APPLICATION: in medium

DURATION
- Preincubation period: none
- Exposure duration: 3 hours at 37±1.0°C (experiment 1), 24 hours at 37±1.0°C (experiment 2)
- Expression time (cells in growth medium): 2 days
- Selection time (if incubation with a selection agent): 11-12 days

SELECTION AGENT (mutation assays): trifluorothymidine (TFT).

NUMBER OF REPLICATIONS: single cultures; initial experiment (3 h exposure +/- MA) repeated (24 hour exposure -MA)

NUMBER OF CELLS EVALUATED: Cells treated: 8 x 10⁶ cells (10⁶ cells/ml for 3 hours treatment) or 5 x 10⁶ cells (1.25 x 10⁵ cells/ml for 24 hours treatment). Cloning efficiency: 1 cell was added per well (2 x 96-well microtiter plates/concentration) in non-selective medium.
Mutagenicity evaluation: 9.6 x 10⁵ cells/concentration were plated in five 96-well microtiter plates, each well containing 2000 cells in selective medium (TFT-selection)

DETERMINATION OF CYTOTOXICITY
- Method: cloning efficiency; relative total growth

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

Evaluation criteria:

A test substance is considered positive in the mutation assay if it induces a MF of more than MF(controls) + 126 in a dose-dependent manner.

Statistics:

The cloning efficiency was obtained using the Poisson distribution

Key result

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

In the absence of metabolic activation, 3 hour treatment, an increase was observed at the dose level of 52 µg/ml but is not considered to be biologically relevant, as the increase was only two-fold and not above the Global evaluation factor (GEF) of 195 , MF(controls) + 126. Furthermore this increase is related to the unexplainable low cloning efficiency day 2 (42%) of this dose level (incidental finding) and no dose-related effect is seen. In addition, no effect was observed in the 24 hour treatment

COMPARISON WITH HISTORICAL CONTROL DATA: The spontaneous mutation frequencies in the solvent-treated control cultures were within the minimum and maximum value of the historical control data range.

Table 1: Experiment 1: Cytotoxic and mutagenic response of the test substance in the mouse lymphoma L5178Y test system (3 hours treatment)

Dose (µg/ml)	Relative Total Growth (%)		Induced mutation frequency
	-MA	+MA	-MA	+MA
Ethanol	100	100	1.0	1.0
0.056	99	115	0.9	0.7
0.18	91	78	0.8	0.9
0.55	118	77	0.9	1.6
1.7	86	79	1.2	1.1
5.4	105	62	1.0	1.2
17	117	76	0.4	0.9
52	53	59	2.0	1.1
164*	87	68	1.4	1.1
Positive control	56	10	10.8	15.7

* the test substance precipitated in the exposure medium

Table 2: Experiment 2: Cytotoxic and mutagenic response of the test substance in the mouse lymphoma L5178Y test system (24 hours treatment)

Dose (µg/ml)	Relative Total Growth (%)	Induced mutation frequency
	-MA	-MA
Ethanol	100	1.0
0.056	96	0.7
0.18	116	0.8
0.55	126	0.7
1.7	120	0.7
5.4	131	0.7
17	117	0.6
52	107	0.6
164*	106	0.6
Positive control	58	11.2

* the test substance precipitated in the exposure medium

Conclusions:

Dodecamethylcyclohexasiloxane has been tested for mutagenicity in mouse lymphoma cells L5178Y/TK⁺′⁻-3.7.2C cells in a reliable study conducted according to OECD Test Guideline 476, in compliance with GLP. No cytotoxicity was observed, and no increase in mutant frequency above the Global Evaluation Frequency plus 126 was observed in either the absence or presence of exogenous metabolic activation when tested up to concentrations limited by the solubility of the test substance. Appropriate solvent and positive controls were included and 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

Description of key information

Mouse micronucleus assay study (ip administration): Negative (OECD Test Guideline 474) (BioReliance, 2009).

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:

2008-09-18 to 2009-02-06

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 474 (Mammalian Erythrocyte Micronucleus Test)

Version / remarks:

(1998)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ICH S2A (1996) and ICH S2B (1997)

Deviations:

no

GLP compliance:

yes

Type of assay:

micronucleus assay

Species:

mouse

Strain:

ICR

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Harlan, Frederick MD
- Age at study initiation: 6-8 weeks
- Weight at study initiation: range finding: males 30.1-33.5 g, females 24.8-26.7 g); definitive micronucleus study: males 28.6-33.4 g, females 23.8-26.3 g.
- Assigned to test groups randomly: under following basis: according to a computer-generated program, which is based on distribution according to body weight.
- Fasting period before study: no
- Housing: up to five per rodent Micro-Barrier cage
- Diet : ad libitum
- Water : ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22
- Humidity (%): 50 ± 20%
- Air changes (per hr): at least 10 changes of fresh HEPA-filtered air every hour.
- Photoperiod (hrs dark / hrs light): 12 hour light/12 hour dark


IN-LIFE DATES: no information

Route of administration:

intraperitoneal

Vehicle:

- Vehicle(s)/solvent(s) used: corn oil
- Justification for choice of solvent/vehicle: based on good solubility/workability of the test article in the vehicle and compatibility with the test system and route of administration.
- Concentration of test material in vehicle: Stock solution 100 mg/ml diluted to appropriate doses: 25, 50, 100 mg/ml for definitive assay
- Lot/batch no. (if required): 3783J

Frequency of treatment:

Single treatment

Post exposure period:

24 and 78 hours

Dose / conc.:

25 other: mg/ml (nominal)

Remarks:

analysis of dosing solutions showed 85-115% of target solution

Dose / conc.:

50 other: mg/ml (nominal)

Remarks:

analysis of dosing solutions showed 85-115% of target solution

Dose / conc.:

100 other: mg/ml (nominal)

Remarks:

analysis of dosing solutions showed 85-115% of target solution

No. of animals per sex per dose:

5 (low and mid dose, and positive control); 10 (vehicle control); 15 (high dose)

Control animals:

yes, concurrent vehicle

Positive control(s):

- cyclophosphamide
- Justification for choice of positive control(s): none given in report - standard positive control substance
- Route of administration: intraperitoneal
- Doses / concentrations: concentration 2.5 mg/ml, dose 50 mg/kg bw

Tissues and cell types examined:

Femoral bone marrow

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: Based on preliminary toxicity study.

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

DETAILS OF SLIDE PREPARATION: (slides) were prepared and stained with May-Gruenwald-Giemsa stain

METHOD OF ANALYSIS: Using a light microscope and a medium magnification (400X), an area of acceptable quality was selected such that the cells were well spread and stained. Using oil immersion (1000X), the following cell populations and cellular components were evaluated and enumerated:
Polychromatic erythrocytes (PCEs)
PCEs stain bluish. PCEs are young erythrocytes (early stage of erythropoiesis) and are the target cells for evaluation of the test article clastogenicity. Two-thousand PCEs per mouse were scored for the presence of micronuclei resulting in evaluation of a total of 10,000 PCEs per each treatment group.
Normochromatic erythrocytes (NCEs)
NCEs stain pink (reddish). NCEs are mature erythrocytes (red blood cells) and are the final cell population formed during erythropoiesis. The number of NCEs and micronucleated NCEs (MNCEs) in the field of 1000 total erythrocytes (ECs) was determined for each animal in order to determine the proportion of polychromatic erythrocytes to total erythrocytes (PCEs/ECs). The incidence of MNCEs per 2000 PCEs was enumerated for each animal, but the results were not presented in the report
Micronuclei (M)
Micronuclei are round, darkly-staining nuclear (chromosome) fragments with a sharp contour and diameters usually from 1/20 to 1/5 of an erythrocyte. Micronuclei may occur in PCEs (MPCEs) or NCEs (MNCEs).
The proportion of polychromatic erythrocytes to total erythrocytes was also recorded per 1000 erythrocytes per each animal (PCEs/ECs ratio).

Evaluation criteria:

A dose-dependent increase in the incidence of micronucleated polychromatic erythrocytes and one or more doses statistically elevated relative to the vehicle control would be considered a positive result.

Statistics:

Kastenbaum-Bowman Tables (binomial distribution, p ≤ 0.05)

Key result

Sex:

male/female

Genotoxicity:

negative

Toxicity:

yes

Remarks:

piloerection (1000 and 2000 mg/kg), lethargy (2000 mg/kg); reductions in PCE/EC ratio (up to 11%) were observed in some test article groups relative to the vehicle control group.

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

RESULTS OF RANGE-FINDING STUDY
- Dose range: 1, 10, 100, 1000 and 2000 mg/kg bw
- Solubility: no information
- Clinical signs of toxicity in test animals: lethargy and piloerection at top and top two doses respectively
- Evidence of cytotoxicity in tissue analyzed: none
- Rationale for exposure: up to limit dose
- Harvest times: 3 days

RESULTS OF DEFINITIVE STUDY
- Induction of micronuclei (for Micronucleus assay): none
- Ratio of PCE/CE (for Micronucleus assay): reductions of up to 22% observed in some test article groups. Reduction of this magnitude without a dose response suggests that the test article did not inhibit erythropoiesis.
- Appropriateness of dose levels and route: appropriate dose levels and route
- Statistical evaluation: appropriate statistical evaluation of results
- The number of micronucleated PCEs in the vehicle control groups did not exceed the historical vehicle control range.

Table 1: Summary of Bone Marrow Micronucleus Analysis Following a Single Intraperitoneal Administration of Dodecamethylcyclohexasiloxane (D6) in ICR Mice

Treatment (20 ml/kg)	Sex	Time (hr)		Number of Animals		PCE/Total Erythrocytes (Mean +/- SD)	Change from Control (%)	Number of MPCE/1000 PCE (Mean +/- SD)	Number of MPCE/PCE Scored
Corn Oil	M	24		5		0.426 ±0.05	-	0.1 ± 0.22	1/10000
	F	24		5		0.396 ± 0.08	-	0.1 ± 0.22	1/10000
Dodecamethylcyclohexasiloxane (D6)
500 mg/kg bw	M	24	5		0.387 ± 0.04		-9	0.2 ± 0.27	2/10000
	F	24	5		0.370 ± 0.09		-7	0.2 ± 0.27	2/10000
1000 mg/kg bw	M	24	5		0.380 ± 0.03		-11	0.01 ± 0.22	1/10000
	F	24	5		0.393 ± 0.07		-1	0.01 ± 0.22	1/10000
2000 mg/kg bw	M	24	5		0.462 ± 0.02		8	0.04 ± 0.22	4/10000
	F	24	5		0.449 ± 0.07		13	0.02 ± 0.27	2/10000
	M	48	5		0.484 ± 0.03		-9	0.2 ± 0.27	2/10000
	F	48	5		0.489 ± 0.15		-11	0.2 ± 0.27	2/10000
Cyclophosphamide 50 mg/kg	M	24	5		0.336 ± 0.04		-21	11.9 ± 1.43	*119/10000
	F	24	5		0.348 ± 0.04		-12	10.9 ± 1.29	*109/10000
	M	24	5		0.530 ± 0.03		-	0.2 ± 0.27	2/10000
Corn Oil	F	24	5		0.550 ± 0.03		-	0.2 ± 0.27	2/10000

*Statistically significant increase, p </= to 0.05 (Kastenbaum-Bowman Tables)

Conclusions:

Dodecamethylcyclohexasiloxane (D6) has been tested in a reliable in vivo micronucleus assay in ICR mice conducted according to OECD Test Guideline 474 and in compliance with GLP. No statistically significant increase in the incidence of micronucleated polychromatic erythrocytes relative to control was observed in any test substance group up to limit concentrations at 24 and 48 hours after intraperitoneal administration of the test substance. Reductions in PCE/EC ratio (up to 11%) were observed in some test article groups, indicating that the test article had reached the target tissue. Administration of cyclophosphamide (the positive control) induced marked increases in micronucleated polychromatic erythrocytes. It is concluded that the test substance is negative for the induction of micronuclei in vivo under the conditions of the test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Information is available for mutagenicity to bacterial and mammalian cells from in vitro studies, and for cytogenicity from an in vivo micronucleus assay.

Dodecamethylcyclohexasiloxane (D6) has been tested in a reliable study conducted in accordance with OECD Test Guideline 471 and in compliance with GLP (NOTOX, 1999f). No evidence of test substance induced increase in the number of revertants was observed when the substance was tested in the presence and absence of metabolic activation in Salmonella typhimurium strains TA1535, TA1537, TA100 and TA98 and Escherichia coli WP2uvrA, in either the initial or the independent repeat experiment. Appropriate solvent and positive controls were included and gave expected responses. It is concluded that the test substance is negative for mutagenicity to bacteria under the conditions of the test.

In vitro cytogenicity testing is not required as there is a reliable in vivo micronucleus assay available.

Dodecamethylcyclohexasiloxane (D6) has been tested for mutagenicity in mouse lymphoma cells L5178Y cells in a reliable study conducted according to OECD Test Guideline 476 and in compliance with GLP (WIL Research, 2015a). No cytotoxicity was observed, and no increase in mutant frequency above the Global Evaluation Frequency was observed in either the absence or presence of exogenous metabolic activation when tested up to concentrations limited by the solubility of the test substance. Appropriate solvent and positive controls were included and 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.

Dodecamethylcyclohexasiloxane (D6) has been tested in a reliable in vivo micronucleus assay in ICR mice conducted according to OECD Test Guideline 474 and in compliance with GLP (BioReliance, 2009). No statistically significant increase in the incidence of micronucleated polychromatic erythrocytes relative to control was observed in any test substance group up to limit concentrations at 24 and 48 hours after intraperitoneal administration of the test substance. Reductions in PCE/EC ratio (up to 11%) were observed in some test article groups, indicating that the test article had reached the target tissue. Administration of cyclophosphamide (the positive control) induced marked increases in micronucleated polychromatic erythrocytes. It is concluded that the test substance is negative for the induction of micronuclei in vivo under the conditions of the test.

 

Justification for classification or non-classification

Based on reliable in vitro and in vivo data, D6 does not require classification for mutagenicity according to Regulation (EC) No 1272/2008.