1,1,3,3-tetramethyldisiloxane

Genetic toxicity: in vitro

Administrative data

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-09-09 - 2008-10-10

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1997

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

1,1,3,3-tetramethyldisiloxane

EC Number:

221-906-4

EC Name:

1,1,3,3-tetramethyldisiloxane

Cas Number:

3277-26-7

Molecular formula:

C4H14OSi2

IUPAC Name:

1,1,3,3-tetramethyldisiloxane

Method

Species / strain

Species / strain 1

Species / strain / cell type:

S. typhimurium TA 1535, TA 1537, TA 98 and TA 100

Species / strain 2

Species / strain / cell type:

E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Phenobarbital/β-Naphtholflavone induced rat liver S9

Test concentrations with justification for top dose:

Experiment 1 - 3, 10, 33, 100, 333, 1000, 2500 and 5000 µg/plate Experiment 2 - 33, 100, 333, 1000, 2500 and 5000 µg/plate

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: THF
- Justification for choice of solvent/vehicle: As agreed with the sponsor THF was chosen for its solubility properties and its relative non-toxicity to the bacteria.

Controls

Controls 1

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA100, TA1535 without metabolic activation 10 µg/plate

Controls 2

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-NOPD

Remarks:

TA98 10 µg/plate, TA1537 50 µg/plate, without metabolic activation

Controls 3

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

methylmethanesulfonate

Remarks:

WP2 uvrA without metabolic activation 3 µL/plate

Controls 4

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

TA1535, TA1537, TA98, TA100 - 2.5 µg/plate. WP2 uvrA - 10 µg/plate with metabolic activation

Details on test system and experimental conditions:

METHOD OF APPLICATION: in agar (plate incorporation); preincubation

ACTIVATION: S9 mix contained glucose-6-phospate and NADP as co-factors. S9 was 10% v/v in the cultures.
DURATION
- Preincubation period: 60 minutes at 37ºC
- Exposure duration: 48 - 72 hours at 37ºC

SELECTION AGENT (mutation assays): histidine deficient agar


NUMBER OF REPLICATIONS: triplicate plates, experiment repeated

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


OTHER:

Evaluation criteria:

A test item is considered as a mutagen if a biologically relevant increase in the mean number of revertants exceeding the threshold twice (strains TA98, TA100 and WP2 uvrA) or thrice (strains TA1535 and TA1537) the mean colony count of the corresponding solvent control is observed. A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration. An increase exceeding the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.

Statistics:

No statistical evaluation of the data required.

Results and discussion

Test results

Test results 1

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:

valid

Positive controls validity:

valid

Test results 2

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:

valid

Positive controls validity:

valid

Additional information on results:

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: none observed


ADDITIONAL INFORMATION ON CYTOTOXICITY: none observed

Any other information on results incl. tables

Summary results – Experiment I

Dose µg/plate	+/- metabolic activation	Average number of colony counts
		TA1535	TA1537	TA98	TA100	WP2 uvrA
Solvent control	-	11	7	27	123	44
Untreated control	-	9	9	23	119	44
3	-	15	8	28	116	40
10	-	13	11	25	111	44
33	-	13	9	31	128	51
100	-	14	13	35	115	48
333	-	8	8	19	101	40
1000	-	10	9	23	101	47
2500	-	16	12	25	108	50
5000	-	11	9	26	118	52
Positive control	-	1791	97	343	2013	1158
Solvent control	+	22	13	33	130	60
Untreated control	+	16	15	29	111	61
3	+	14	15	33	113	48
10	+	16	15	34	144	58
33	+	17	7	39	139	67
100	+	17	15	40	149	61
333	+	15	15	39	120	61
1000	+	15	13	38	138	56
2500	+	21	13	33	145	67
5000	+	17	12	39	145	65
Positive control	+	242	213	1452	1629	243

 

Summary results of Experiment II

Dose µg/plate	+/- metabolic activation	Average number of colony counts
		TA1535	TA1537	TA98	TA100	WP2 uvrA
Solvent control	-	15	13	32	142	49
Untreated control	-	17	19	30	166	40
33	-	18	12	28	144	54
100	-	14	12	37	123	52
333	-	15	10	27	139	46
1000	-	14	10	28	141	48
2500	-	14	11	32	146	47
5000	-	14	13	28	141	47
Positive control	-	2076	120	523	2172	275
Solvent control	+	19	13	32	156	63
Untreated control	+	18	13	35	160	59
33	+	18	13	34	156	59
100	+	15	14	31	157	69
333	+	22	13	32	162	65
1000	+	17	13	36	159	67
2500	+	19	10	36	161	58
5000	+	21	10	32	153	48
Positive control	+	302	210	1986	2372	266

Applicant's summary and conclusion

Conclusions:

1,1,3,3-Tetramethyldisiloxane has been tested for mutagenicity to bacteria, in a study which was conducted according to OECD Test Guideline 471, in compliance with GLP. No evidence of a test substance related increase in the number of revertants was observed with or without activation in Salmonella typhimurium strains TA 98, TA 100, TA 1535 and TA 1537 and E.coli WP2uvrA in the initial or the repeat experiments. Appropriate solvent and positive 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.