Reaction mass of 1,3-dimethyl-1,1,3,3-tetraphenyldisiloxane and 1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane and 1,3,3,5,5,7-hexamethyl-1,1,7,7-tetraphenyltetrasiloxane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

The mutagenic potential of the test item was determined with the Bacterial Reverse Mutation Test following OECD 471 and EU B.13/14.

Based on the results of this study it is concluded that the test item is not mutagenic in the Salmonella typhimurium test strains TA97a, TA98, TA100, TA102 and TA1535 in the absence and presence of metabolic activation under the experimental conditions in the present study.

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

June-July 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Qualifier:

according to guideline

Guideline:

EU Method B.13/14 (Mutagenicity - Reverse Mutation Test Using Bacteria)

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Species / strain / cell type:

S. typhimurium TA 98

Details on mammalian cell type (if applicable):

Salmonella typhimurium strains were obtained from TRINOVA BioChem GmbH (batch: TA98: 5136D)

Species / strain / cell type:

S. typhimurium TA 100

Details on mammalian cell type (if applicable):

Salmonella typhimurium strains were obtained from TRINOVA BioChem GmbH (batch: TA100: 5141D)

Species / strain / cell type:

S. typhimurium TA 102

Details on mammalian cell type (if applicable):

Salmonella typhimurium strains were obtained from TRINOVA BioChem GmbH (batch: TA102: 5145D)

Species / strain / cell type:

S. typhimurium TA 1535

Details on mammalian cell type (if applicable):

Salmonella typhimurium strains were obtained from TRINOVA BioChem GmbH (batch: TA1535: 5138D)

Species / strain / cell type:

S. typhimurium, other: 97a

Details on mammalian cell type (if applicable):

Salmonella typhimurium strains were obtained from TRINOVA BioChem GmbH (batch: TA97a: 5033D)

Metabolic activation:

with and without

Metabolic activation system:

S9 was obtained by Trinova Biochem GmbH, Gießen. Batch nos. 3913, 3833, 3837,
Specification produced from the livers of male Sprague-Dawley rats which were treated with 500 mg Aroclor 1254/kg body weight intraper-itoneally.

Test concentrations with justification for top dose:

plate incorporation method: 5 / 1.5 / 0.5 / 0.15 / 0.05 µL/plate
pre-incubation method: 5 / 2.5 / 1.25 / 0.63 / 0.31 / 0.16 µL/plate

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

Positive controls:

yes

Positive control substance:

sodium azide

benzo(a)pyrene

other: 4-Nitro-1,2-phenylene diamine; 2-Amino-Anthracene

Details on test system and experimental conditions:

Culture of Bacteria
Eight hours before the start of each experiment, one vial permanent culture of each strain was taken from the deep freezer and an aliquot was put into a culture flask containing nutri-ent broth. After incubation for eight hours at 37 ±1 °C, the cultures were used in the experiment. During the test, the cultures were stored at room temperature as to prevent changes in the titre.

Experimental Parameters
First Experiment
Concentrations tested 5 / 1.5 / 0.5 / 0.15 / 0.05 μL/plate
Incubation time 48 h
Incubation temperature 37 ±1 °C
Tested strains TA97a, TA98, TA100, TA102, TA1535
Method plate incorporation method

Second Experiment
Concentrations tested 5 / 2.5 / 1.25 / 0.63 / 0.31 / 0.16 μL/plate
Incubation time 48 h
Incubation temperature 37 ±1 °C
Tested strains TA97a, TA98, TA100, TA102, TA1535
Method pre-incubation method

Per bacteria strain and concentration, three plates with and three plates without metabolic activation (-S9) were used.

Evaluation criteria:

The colonies were counted visually and the numbers were recorded.
The mean values and standard deviations of each threefold determination was calculated as well as the increase factor f(l) of revertant induction (mean revertants divided by mean spontaneous revertants) of the test item solutions and the positive controls. Additionally, the absolute number of revertants (Rev. Abs.) (mean revertants less mean spontaneous re-vertants) was given.
A substance is considered to have mutagenic potential, if a reproducible increase of re-vertant colonies per plate exceeding an increase factor of 2 in at least one strain can be observed. A concentration-related increase over the range tested is also taken as a sign of mutagenic activity.

Key result

Species / strain:

S. typhimurium, other: TA97a, TA98, TA100, TA102 and TA1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Conclusions:

The test item showed no increase in the number of revertants in all bacteria strains in both experiments.
Nearly all negative and all strain-specific positive control values were within the laboratory historical control data ranges indicating that the test conditions were adequate and that the metabolic activation system functioned properly.
Based on the results of this study it is concluded that the test item is not mutagenic in the Salmonella typhimurium test strains TA97a, TA98, TA100, TA102 and TA1535 in the absence and presence of metabolic activation under the experimental conditions in the present study.

Executive summary:

Confirmation of the Criteria and Validity

All strains met the criterion of at least 10^9 bacteria/mL, and no inconsistencies were found in the sterility control. Nearly all determined values for the spontaneous revertants of the negative controls were in the normal range of the test laboratory. All positive controls (diagnostic mutagens) showed mutagenic effects with and without metabolic activation and were within the historical control data ranges.

Solubility and Toxicity

In the two experiment, the test item showed no precipitates on the plates in all tested concentrations.

No signs of toxicity towards the bacteria strains could be observed. The bacterial background lawn was visible and not affected. The number of revertant colonies was not reduced.

Mutagenicity

No increase of the number of revertant colonies in the treatments with and without metabolic activation could be observed. No concentration-related increase over the tested range was found.

Therefore, the test item is stated as not mutagenic under the conditions of this experiment.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

The test item is not mutagenic in the Salmonella typhimurium test strains TA97a, TA98, TA100, TA102 and TA1535 in the absence and presence of metabolic activation under the experimental conditions.