Dichloro(dimethyl)silane

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 activation in all strains tested (equivalent to OECD TG 471) (Pharma, 1987).
Cytogenicity in mammalian cells: ambiguous without activation in L5178Y cells (similar to OECD TG 473) (Litton Bionetics, 1978).
Mutagenicity in mammalian cells: negative with and without activation in L5178Y mouse lymphoma cells (similar to OECD 476) (Litton Bionetics, 1978).

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

Study period:

1987-06-03 to 1987-07-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Principles of method if other than guideline:

other: Ames et al. 1973

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

other: Salmonella typhimurium: TA 98, TA 100, TA 1535, TA1537, TA1538 and Escherichia coli WP2uvrA

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced rat liver S9

Test concentrations with justification for top dose:

See table 1.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: acetone

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:

2-nitrofluorene

Remarks:

TA 98, TA 1538 (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: N-Methyl-N-nitro-N-nitrosoguanidine

Remarks:

WP2uvrA (without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

Remarks:

All strains (with 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:

ACTIVATION: Male Sprague Dawley rats (200-300g) were dosed with 500 mg/ kg bw Aroclor 1254 5 d before sacrifice. Livers from 5-6 animals were polled and used to prepare S9 homogenate. S9 mix included 10% v/v S9, 8 mM MgCl2, 33 mM KCl, 5mM glucose-6-phosphate, 4 mM NADP+ and 100 mM phosphate buffer pH 7.4. 0.5 ml of S9 mix were added to 2 ml top agar, 0.1 ml bacterial culture and 0.1 ml test substance solution (total volume 2.7 ml) giving a final concentration of S9 of approximately 2%.

METHOD OF APPLICATION: in agar (plate incorporation)


DURATION
- Exposure duration:

SELECTION AGENT (mutation assays):
SPINDLE INHIBITOR (cytogenetic assays):
STAIN (for cytogenetic assays): 48-72 hours

NUMBER OF REPLICATIONS: 3 plates per test concentration. The experiment was repeated.

DETERMINATION OF CYTOTOXICITY

- Method: other: Background lawn assessment

Evaluation criteria:

Mutagenicity of the test substance is indicated by an increase in the number of revertant colonies.

Statistics:

Statistical methods: Responses (numbers of revertants) to the test substance were compared to concurrent negative and positive 
controls, as well as to historical data.

Species / strain:

other: Salmonella typhimurium: TA 98, TA 100, TA 1535, TA1537, TA1538 and Escherichia coli WP2uvrA

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: >1500 µg/plate

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

The test compound was toxic to most of the bacterial strains and precipitate was observed at doses greater than or equal to 2500 ug/plate, both with and without metabolic activation.  Final mutagenicity testing was conducted with 5000 ug/plate as the top dose.  The results of the tests conducted on the test substance in the absence or presence of a metabolic activation system were all negative.
Revertants per plate for positive control substances ranged from 18- 680, depending on the agent and strain.

 

Table 2 : Exp 1 : Mutagenicity assay for all strains with and without metabolic activation (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*	25	30	No	158	175	No	13	12	No
4	21	29	No	153	159	No	12	11	No
20	19	28	No	148	174	No	11	12	No
100	23	28	No	152	181	No	12	10	No
500	27	24	No	148	187	No	14	12	No
2500	18	23	No	166	174	No	8	14	No
10,000	-	3	Yes	-	-	Yes	6	2	Yes
Positive Control	364	437	No	554	611	No	404	119	No

*solvent control with Acetone

 

Table 2 : Exp 1 : Mutagenicity assay for all strains with and without metabolic activation (mean of 3 plates)

	TA1537			TA1538			WP2uvrA
Conc. (µg/plate)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	12	8	No	17	17	No	47	52	No
4	9	8	No	16	20	No	43	51	No
20	7	8	No	13	20	No	44	53	No
100	7	9	No	16	22	No	40	48	No
500	8	5	No	16	24	No	46	57	No
2500	8	6	No	16	11	No	43	41	No
10,000	-	0	Yes	4	1	Yes	-	12	Yes
Positive Control	155	84	No	591	547	No	241	174	No

*solvent control with Acetone

 

Table 3 : Exp 2 : Repeat Assay 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*	19	32	No	168	205	No	16	13	No
4	27	40	No	153	234	No	17	13	No
20	23	36	No	180	2335	No	17	13	No
100	26	35	No	182	197	No	15	12	No
500	24	27	No	141	207	No	11	16	No
2500	24	29	No	183	207	No	16	16	No
5000	-	25	Yes	119	167	No	13	16	No
Positive control	249	377	No	483	628	No	308	76	No

*solvent control with Acetone

 

Table 3 : Exp 2 : Repeat Assay Number of revertants per plate (mean of 3 plates)

	TA1537			TA1538			WP2uvrA
Conc. (µg/plate)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)	— MA	+ MA	Cytotoxic (yes/no)
0*	12	9	No	14	23	No	48	75	No
4	8	9	No	13	26	No	61	68	No
20	9	8	No	13	26	No	59	58	No
100	9	7	No	15	20	No	63	52	No
500	8	7	No	12	23	No	50	35	No
2500	9	10	No	16	19	No	39	37	No
5000	4	6	Yes	14	18	No	23	26	Yes
Positive control	94	91	No	458	515	No	365	304	No

*solvent control with Acetone

 

 

Conclusions:

Dichlorodimethylsilane has been tested for mutagenicity to bacteria according to a protocol similar to the current guideline. The test substance did not demonstrate genetic activity in any of Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA1537, TA1538 and Escherichia coli WP2uvrA, up to cytotoxic concentration, with or without metabolic activation. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is not mutagenic to bacteria under the conditions of the test.

Reference 2

Endpoint:

in vitro cytogenicity / chromosome aberration study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1980-01-28 to 1980-03-27

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The restrictions were that only 50 cells were scored.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 473 (In Vitro Mammalian Chromosome Aberration Test)

Deviations:

yes

Remarks:

50 cells/dose counted, guideline requires 200

GLP compliance:

not specified

Type of assay:

in vitro mammalian chromosome aberration test

Species / strain / cell type:

mouse lymphoma L5178Y cells

Details on mammalian cell type (if applicable):

- Type and identity of media: Fischer's medium

- Properly maintained: yes

Metabolic activation:

with and without

Metabolic activation system:

Aroclor induced mouse liver S9

Test concentrations with justification for top dose:

0.2, 0.4, 0.8, 0.16, 0.32, 0.64 µl/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: ethanol

Untreated negative controls:

yes

Remarks:

medium only

Negative solvent / vehicle controls:

yes

Remarks:

ethanol (1% of final volume)

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

- MA

Untreated negative controls:

yes

Remarks:

medium only

Negative solvent / vehicle controls:

yes

Remarks:

ethanol (1% of final volume)

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: Dimethylnitrosamine

Remarks:

+ MA

Details on test system and experimental conditions:

METHOD OF APPLICATION: in medium


DURATION

- Preincubation period: none

- Exposure duration: 4 hours

- Expression time (cells in growth medium): 24

- Fixation time (start of exposure up to fixation or harvest of cells): 28


SPINDLE INHIBITOR (cytogenetic assays): colcemid (concentration 2 * 10^-7 M)


STAIN (for cytogenetic assays): 5% Giemsa


NUMBER OF REPLICATIONS: 1


NUMBER OF CELLS EVALUATED: 50 per dose


DETERMINATION OF CYTOTOXICITY

- Method: toxicity was measured in a preliminary study, no further details reported.


OTHER EXAMINATIONS:

- Determination of polyploidy: yes

- Determination of endoreplication: no

Evaluation criteria:

Gaps were not counted as significant aberrations, open breaks were considered indicators of genetic damage, as were configurations resulting from the abnormal repair of breaks such as multiradials, rings and multicentrics. Pulverised cells and chromosomes were not included in the count since the number of aberrations is unknown. The estimated number of breaks involved in production of the different aberrations of cells observed, the frequency of cells with more than one aberration, and any evidence for increasing amount of damage with increasing dose, were taken into account in order to establish if the test substance is considered clastogenic.

Statistics:

Student t-test and blind scoring of aberrations.

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

not specified

Remarks:

toxicity was measured but the results not reported.

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS

- Water solubility: measured, but not reported.

- Other confounding effects: no


RANGE-FINDING/SCREENING STUDIES: a screening test was conducted however the details were not reported.


COMPARISON WITH HISTORICAL CONTROL DATA: the negative control data falls within the an acceptable range of the historical control data.


ADDITIONAL INFORMATION ON CYTOTOXICITY: toxicity was determined as mitotic index - reported in tables below.

Table 1a: Results of chromosome analysis, without metabolic activation (total of 50 cells).

 

Concentration (µl/ml)	Number and type of aberrations	Cells with >1 aberration (%)	Mitotic index
Negative control	1 tb	0	4.8
Solvent control	15	0	6.4
Positive control	1f, 1af	0	1.1
0.2	2tb	0	6.8
0.4	3tb 2f 1t	1	7.2
0.8	2af	0	7.6
0.16	1af	0	7.0
0.32	2tb, 2f, 2af, 1min	1	5.4
0.64	TOXIC	-	-

 Where the negative control is medium, solvent control is ethanol and the positive control is ethylmethanesulfonate (0.5 μl/ml)

Table 1b: Results of chromosome analysis, with metabolic activation (total of 50 cells).

Concentration (µl/ml)	Number and type of aberrations	Cells with >1 aberration (%)	Mitotic index
Negative control	3tb, 1f, 1af	0	6.0
Solvent control	0	0	4.7
Positive control	6tb, 6f, 7t, 1tr, 1qr, 1min	4	3.3
0.2	2tb, 3f, 4af	2	4.5
0.4	2tb	1	7.2
0.8	3tb, 3f, 3af	1	7.3
0.16	3tb, 3af	1	6.0
0.32	0	0	0.4
0.64	2tb, 1f, 2af, 1t	1	4.7

 Where the negative control is medium, solvent control is ethanol and the positive control dimethylnitrosamine (0.3 μl/ml).

Abbreviations of aberration type: af = acentric fragment; t = translocation; tb = chromatid break; f = fragment; qr = quadriradial; min = minute chromosome.

Conclusions:

Dichloro(dimethyl)silane was tested in mouse lymphoma cells with and without metabolic activation according to a protocol similar to OECD 473 and induced an elevated number of structural chromosomal aberrations, though there was no increase in the number of cells with two or more aberrations. Appropriate positive and solvent controls were included and gave expected results. Therefore it is concluded that the test material is ambiguous for cytogenicity under the conditions of the test.

Reference 3

Endpoint:

in vitro gene mutation study in mammalian cells

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

no duplicates though test repeated. Concurrent positive controls did not stain

Principles of method if other than guideline:

The procedure used is a modification of that reported by Clive and Spector (Mutation Research, 31:17-29, 1975).

GLP compliance:

no

Type of assay:

mammalian cell gene mutation assay

Species / strain / cell type:

other: mouse lymphoma (L5178Y)

Metabolic activation:

with and without

Metabolic activation system:

Mouse Liver S9

Test concentrations with justification for top dose:

without activation was 0.02 - 0.32 µl/ml; with activation the dose range used was 0.04 - 0.64 µl/ml

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Ethanol

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

ethylmethanesulphonate

Remarks:

(without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

N-dimethylnitrosamine

Remarks:

(with activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

(without activation)

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

benzo(a)pyrene

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

NUMBER OF REPLICATIONS: 3 plates per concentration

DETERMINATION OF CYTOTOXICITY

- Method: loss in growth potential of cells (relative total growth)

Evaluation criteria:

The test substance was evaluated for its ability to induce point mutations.

Toxicity is defined by a 50 % or greater reduction in growth compared with the solvent control.

Statistics:

Cells counted. Relative suspension growth (% of control), total mutant and viable clones, relative cloning efficiency, % relative growth and mutant frequency calculated.

Species / strain:

mouse lymphoma L5178Y cells

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

other: 0.64 µl/ml with activation

Vehicle controls validity:

valid

Untreated negative controls validity:

not applicable

Positive controls validity:

valid

Additional information on results:

COMPARISON WITH HISTORICAL CONTROL DATA: Positive controls were within range of historical control data

Table 2 : Results of Mammalian Mutagenicity assay  with L5178Y Mouse Lymphoma cells

Concentration µl/ml	Mutant* Frequency	Mutant* Frequency	%Relative  Growth.	%Relative  Growth.	Cytotoxicity (yes/no)
	— MA	+ MA	— MA	+ MA	-
Solvent Control	13.3	38.8	100	100	No
Negative Control	21.7	12.5	113.2	113.8	No
0.02	16.2	-	114.8	-	No
0.04	29.6	24.6	55	87.5	No
0.08	26.1	27.2	102.7	99.1	No
0.16	14.2	33.7	67	91	No
0.32	23.1	26.3	79.4	103.8	No
0.64	-	21.7	-	23.9	Yes
Positive Control	508.5	221.5	25.7	28.2	Yes

*Per 10⁴ surviving cells

Solvent control with Ethanol

Conclusions:

Dichloro(dimethyl)silane did not induce point mutations at any dose level, with or without metabolic activation when tested for mutagenicity to mammalian cells according to a protocol that is similar to OECD TG 476. Appropriate positive, solvent and test medium controls were included and gave expected results. The test substance is considered to be 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

Negative in rat chromosome aberration assay (US EPA guideline test, similar to OECD 475) (Bioassay systems 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:

key study

Study period:

1981-02-04 to 1981-12-21

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

mitotic index was determined in only 500 cells per animal, results are not presented in compliance with current guideline.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 475 (Mammalian Bone Marrow Chromosome Aberration Test)

Deviations:

yes

Remarks:

number of cells evaluated; only male animals used

Qualifier:

according to guideline

Guideline:

other: EPA TAP 22: 269-275, 1972 modified 12/3 to 12/5 1980

Deviations:

not specified

GLP compliance:

yes

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
- Source: Gofmoor Farms, Westboro, MA (range-finding study); Charles River, Wilmington, MA USA (main study)
- Age at study initiation: 10-14 weeks
- Weight at study initiation: 200-250 g
- Assigned to test groups randomly: not reported
- Fasting period before study:
- Housing: 5 per cage
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: not reported


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20
- Humidity (%): 50

Route of administration:

intraperitoneal

Vehicle:

- Vehicle(s)/solvent(s) used: paraffin oil
- Justification for choice of solvent/vehicle: none given
- Concentration of test material in vehicle: not reported
- Purity: laboratory grade

Duration of treatment / exposure:

single injection

Frequency of treatment:

Once

Post exposure period:

sacrifice at 6, 24 and 48 hours after exposure.

Dose / conc.:

5 mg/kg bw/day

Remarks:

Criteria for selection of MTD based on the results of a range-finding study

Dose / conc.:

11 mg/kg bw/day

Remarks:

Criteria for selection of MTD based on the results of a range-finding study

Dose / conc.:

22 mg/kg bw/day

Remarks:

Criteria for selection of MTD based on the results of a range-finding study

Dose / conc.:

32 mg/kg bw/day

Remarks:

Criteria for selection of MTD based on the results of a range-finding study

No. of animals per sex per dose:

5

Control animals:

yes, concurrent vehicle

Positive control(s):

- cyclophosphamide;
- Justification for choice of positive control(s): none given
- Route of administration: not reported
- Doses / concentrations: 22 mg/kg

Tissues and cell types examined:

Bone marrow

Details of tissue and slide preparation:

CRITERIA FOR DOSE SELECTION: Based on range finding study

TREATMENT AND SAMPLING TIMES ( in addition to information in specific fields):

DETAILS OF SLIDE PREPARATION: Cells were centrifuged and resuspended three times in fixative (3:1 methanol:acetic acid). Aliquots of suspended cells were air dried. Slides of acceptable quality were stained with 5% Giesma, and photographed using x100 objective.

METHOD OF ANALYSIS: Negatives were projected onto a white counter and examined for chromosomal breaks or gaps, chromatid breaks or gaps, complex rearrangements, pulverised cells or chromosomes, acentric fragments, polyploidy and large translocations or deletions.

Evaluation criteria:

None given in report

Statistics:

Chi squared test and Wilcoxon test.

Sex:

male

Genotoxicity:

negative

Toxicity:

yes

Remarks:

deaths at 22 mg/kg and above

Vehicle controls validity:

valid

Negative controls validity:

not applicable

Positive controls validity:

valid

Table 1: Results of range-finding studies   Dose level mg/kg Number dead/number animals 54 3/10 43 5/10 32 0/10 22 2/10 11 0/10 5 0/10

Table 2: Results of chromosome analysis in bone marrow(5 animals per dose, approx 110 cells per animal evaluated)

 

-	Positive control	Vehicle control			11mg/kg			22 mg/kg			32 mg/kg
Sampling time (h)	24	6	24	48	6	24	48**	6	24	48	6	24	48
Gaps	46-60	0-4	0-6	0-4	2-6	1-7	0-1	1-5	0-4	0-2	2-10	1-7	1-5
Breaks	ND	0-4	0-2	0-3	0-5	0-7	0-2	0-2	0-2	0-2	1-5	0-5	1-2
Other	3-<23	0-2*	0-1*	0-1*	0	0-2*	0-2*	0	3	0-2*	0	0-2*	0
Mitotic index %	1.3-3.1	1.7-5.0	1.4-3.7	1.2-4.9	0.8-5.8	2.1-5.8	1.0-4.3	2.0-4.7	1.8-5.8	1.4-3.6	2.3-4.5	1.8-4.3	1.7-3.4
Polyploidy	0	0	0		0	0	0	0	0	0	0	0	0
Endo reduplication	0	0	0		0	0	0	0	0	0	0	0	0

Numbers in table represent the range of the mitotic index or the total number of gaps, breaks or other aberrations recorded for each test animal

ND Not determined

* deletions

** 7 animals used at this dose and time, 2 with under 50 analysable cells.

Conclusions:

Dichloro(dimethyl)silane has been tested according to a protocol similar to OECD TG 475. The test substance did not induce chromosome aberrations when tested in male rats by ip injection at doses up to 32 mg/kg bw. Appropriate positive and vehicle controls were included and gave expected results. It is concluded that the test substance is not genotoxic under the conditions of the test.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Data are available for dichloro(dimethyl)silane for all the required endpoints for in vitro genetic toxicity. Most of the studies gave negative results. The exception was an in vitro cytogenicity study (similar to OECD 473) which gave an equivocal result (Litton Bionetics, 1978). The possibility of cytogenetic effects in vivo has been examined in an in vivo chromosome aberration study which gave a negative result.

Dichloro(dimethyl)silane has been tested for mutagenicity to bacteria according to a protocol similar to OECD TG 471 (Pharma, 1987). The test substance did not demonstrate genetic activity in any of Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA1537, TA1538 and Escherichia coli WP2uvrA, up to cytotoxic concentration, with or without metabolic activation. Appropriate positive and solvent controls were included and gave expected results. It is concluded that the test substance is not mutagenic to bacteria under the conditions of the test. The result is supported by negative results in a study using Salmonella typhimurium strains TA 98, TA 100, TA 1535, TA1537 and TA 1538 (Dow Corning Corporation, 1977; Litton Bionetics, 1978), and in a study that tested Salmonella typhimurium strain TA 98, TA 100, TA 1535 and TA 1537 (Bayer, 1984).

Dichloro(dimethyl)silane was tested in mouse lymphoma cells with and without metabolic activation according to a protocol similar to OECD TG 473 and induced an elevated number of structural chromosomal aberrations, though there was no increase in the number of cells with two or more aberrations (Litton Bionetics, 1978). Appropriate positive and solvent controls were included and gave expected results. Therefore it is concluded that the test material is ambiguous for cytogenicity under the conditions of the test. An ambiguous result was also reported in an in vitro sister chromatid exchange assay, also conducted in mouse lymphoma L5178Y cells (Litton Bionetics, 1978).

Dichloro(dimethyl)silane did not induce point mutations at any dose level, with or without metabolic activation when tested for mutagenicity to mammalian cells according to a protocol that is similar to OECD TG 476 (Litton Bionetics, 1978). Appropriate positive, solvent and test medium controls were included and gave expected results. The test substance is considered to be negative for mutagenicity in mouse lymphoma (L5178Y) cells under the conditions of the test.

Dichloro(dimethyl)silane has been in vivo tested according to a protocol similar to OECD TG 475 (Bioassay systems corporation, 1982). The test substance did not induce chromosome aberrations when tested in male rats by ip injection at doses up to 32 mg/kg bw. Appropriate positive and vehicle controls were included and gave expected results. It is concluded that the test substance is not genotoxic under the conditions of the test.

It is considered that as the ambiguous results obtained in the in vitro cytogenicity (chromosome aberration and sister chromatid exchange) assays were not confirmed in the in vivo chromosome aberration assay, the registered substance is not clastogenic and further in vivo testing is not required.

Justification for classification or non-classification

Based on the available in vitro and in vivo information for genetic toxicity, dichloro(dimethyl)silane is not classified for mutagenicity according to Regulation (EC) No 1272/2008.