Decamethyltetrasiloxane

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:

2005-09-15 to 2005-10-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2005

Report date:

2005

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

1997

Deviations:

no

GLP compliance:

yes

Type of assay:

bacterial reverse mutation assay

Test material

Test material information

Constituent 1

Reference substance name:

Decamethyltetrasiloxane

EC Number:

205-491-7

EC Name:

Decamethyltetrasiloxane

Cas Number:

141-62-8

Molecular formula:

C10H30O3Si4

IUPAC Name:

2,2,4,4,6,6,8,8-octamethyl-3,5,7-trioxa-2,4,6,8-tetrasilanonane

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:

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

Controls

Controls 1

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)

Controls 2

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)

Controls 3

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)

Controls 4

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)

Controls 5

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).

Results and discussion

Test results

Test results 1

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

Test results 2

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

Any other information on results incl. tables

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

Applicant's summary and conclusion

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.