Methyl-tris acetonoximo-silane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

No data is available for the target substance Methyl-tris acetonoximo-silane. Thus, available data from the source substance WASOX-MMAC2 was used in a read-across approach.

In a reverse gene mutation assay in bacteria (OECD 471) strains of S. typhimurium (TA97a, TA98, TA100, TA102 and TA1535) were exposed to WASOX-MMAC2 in DMSO at concentrations of 5000, 1667, 556, 185 and 62 µg/plate in the presence and absence of mammalian metabolic activation. There was no evidence of induced mutant colonies over background. This study is classified as acceptable. This study satisfies the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

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:

2004-09-10 to 2004-12-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 471 (Bacterial Reverse Mutation Assay)

Version / remarks:

adopted 21 July 1997

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

- Name: "WASOX-MMAC2"
- Batch No.: 1000024854
- Purity: The test substance is a mixture of mainly 3 components:
MMAC2 (range: 45-80% w/w), accurately 55.0% (GC-% w/w),
MM2AC (range 2-30% w/w), accurately 11.7% (GC-% w/w) and
MAC3 (range 5-30% w/w),accurately 24.0% (GC-% w/w) plus by-products and impurities.
The 3 components act uniformly as hardeners for silicone sealing masses. They polymerise, triggered bv hydrolysis.
- CAS No. (main component): 72122-57-7
- Solubility in water: Poorly soluble. A polymeric, insoluble in water, is formed by hydrolysis. Rapid onset of hydrolysis.
- Solubility in other solvents: Easily soluble in toluene and methylcyclohexane
- Appearance: Solid and liquid parts at room temperature.Yellowish brownish colour.
- Melting point: 30 - 35 °C.
- Conditions of storage: Storage under a nitrogen atmosphere, as the substance reacts with water, even from air humidity. Ambient temperature (theoretically up to approx. 40 °C possible), protected against light (handling without protection against light is acceptable).
- Handling precautions: Exothermic reaction with water or humidity from the air.
- Date of expiry: December 2005

Target gene:

Histidine

Species / strain / cell type:

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

Details on mammalian cell type (if applicable):

CELLS USED
- Source of cells: Prof. Bruce N. Ames, Berkeley, California, USA

Metabolic activation:

with and without

Metabolic activation system:

S9 metabolising system

Test concentrations with justification for top dose:

The concentrations for the first experiment were set according to a preliminary toxicity test, The test substance was not toxic up to 5000 µg/petri dish. It was therefore decided to use 5000 µg/plate as the highest eoneentration which is the limit concentration according to the guidelines. Each of the other 4 concentrations was 1/3 of the preceding one. The number and intervals of the concentrations are in accordance with the guidelines.

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: Dimethylsulfoxide
- Justification for choice of solvent/vehicle: The test substance hydrolyses rapidly in water. DMSO is a common vehicle for the Ames test.

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-NOPD

Remarks:

TA97a (10 µg/plate), without S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

2-nitrofluorene

Remarks:

TA98 (2 µg/plate), without S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

sodium azide

Remarks:

TA100 (2 µg/plate), TA1535 (1 µg/plate), without S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: t-Butyl-hydroperoxide

Remarks:

TA102 (50 µg/plate), without S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

7,12-dimethylbenzanthracene

Remarks:

TA97a (10 µg/plate), with S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSo

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

TA98 (1 µg/plate), TA100 (2 µg/plate), TA1535 (2 µg/plate), with S9

Untreated negative controls:

no

Negative solvent / vehicle controls:

yes

Remarks:

DMSO

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 1,8-Dihydroxy-anthraquinone

Remarks:

TA102 (50 µg/plate), with S9

Details on test system and experimental conditions:

METHOD OF APPLICATION: Plate incorporation assay
The exposure was performed according to the 'Plate Incorporation Assay', in which bacteria, test substance (and microsomes) are in contact on the plate without preceding incubation in the liquid state. The number of viable cells in the overnight-cultures is in the range of 2 x 10^8 cells per mL. For each sample the following solutions were combined:
- 0.1 mL of the overnight culture of the bacteria,
- 0.5 mL of S9-mix (or phosphate buffered saline for samples without metabolite activation),
- 0.1 mL of the appropriate test- or reference substance solution and
- 2 mL of top agar.
The combined solutions were mixed and spread over a plate with minimal agar (9 cm diameter). After the top agar had solidified, the plates were incubated at 37 °C until the colonies were visible (2 days).

Counting of colonies
The plates with less than about 50 revertant colonies, i.e. the plates of TA98 and TA1535 with the exception of the positive controls, were counted visually by marking the colonies with a felt tipped pen. The other plates were photographed with a video camera and the picture files were scanned for colonies by a computer program.

Determination of the toxicity
Additionally, to the counting of colonies the bacterial background of the plates was inspected visually. The following signs of toxicity, if present, were recorded:
- A reduced bacterial background lawn (mottled instead of homogeneous).
- Microcolonies of bacteria instead of a homogeneous background lawn.
- No background lawn.
- Clearly reduced numbers of revertant colonies.

NUMBER OF REPLICATIONS: Triplicate repetitions were run for each dose group in each of the two separate experiments that were conducted, for the control groups six-fold repetitions were run.

Evaluation criteria:

The criteria for a positive result are:
A reproducible increase of the number of revertants to more than the following threshold values for at least one of the concentrations:
- For the strains with a low spontaneous revertant rate i.e. TA98 and TA1535: The 2~fold of the amount of the spontaneous revertants.
- For the strains with a high spontaneous revertant rate i.e. TA97a, TA100 and TA102: The 1.66-fold of the amount of the spontaneous revertants.
These threshold values were derived from the variations in the control sampies of our historic data of the Ames test.

Statistics:

Means and standard deviations were calculated for the number of mutants in every concentration group.

Key result

Species / strain:

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

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

not examined

Positive controls validity:

valid

Additional information on results:

Positive Control Substances:
All positive contral substances increased the mutation frequency to more than the threshold values. As 2-aminoanthracene, 1,8-dihydroxy-anthraquinone and 7,12-dimethyl-benzanthracene require metabolie activation for mutagenicity, the results of these substances demonstrate also the efficiency of the metabolising system.

Solubility:
No precipitation of the test substance was seen in any of the concentration groups.

Toxicity:
In the preliminary test and in the main test no toxicity was seen up to 5000 µg/plate.

Mutagenicity:
There was increase in the number of mutants in any of the tested bacterial strains at any of the tested concentrations. The addition of an external metabolising system did not change these results.

Conclusions:

The test item is not genotoxic in the bacterial reverse gene mutation assay in the presence and absence of mammalian metabolic activation.

Executive summary:

In a reverse gene mutation assay in bacteria (OECD 471) strains of S. typhimurium (TA97a, TA98, TA100, TA102 and TA1535) were exposed to WASOX-MMAC2 in DMSO at concentrations of 5000, 1667, 556, 185 and 62 µg/plate in the presence and absence of mammalian metabolic activation. The positive controls did induce the appropriate responses in the corresponding strains. There was no evidence of induced mutant colonies over background. 

This study is classified as acceptable. This study satisfies the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

No data is available for the target substance Methyl-tris acetonoximo-silane. Thus, available data from the source substance WASOX-MMAC2 was used in a read-across approach.

In a reverse gene mutation assay in bacteria (OECD 471) strains of S. typhimurium (TA97a, TA98, TA100, TA102 and TA1535) were exposed to WASOX-MMAC2 in DMSO at concentrations of 5000, 1667, 556, 185 and 62 µg/plate in the presence and absence of mammalian metabolic activation. There was no evidence of induced mutant colonies over background. This study is classified as acceptable. This study satisfies the requirement for Test Guideline OECD 471 for in vitro mutagenicity (bacterial reverse gene mutation) data.

Justification for classification or non-classification

Based on the available data from a suitable read-across partner, the target substance Methyl-tris acetonoximo-silane is considered to be non-mutagenic and no classification is warranted in accordance with CLP Regulation 1272/2008.