N-sodiohexamethyldisilazane

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Link to relevant study records

Reference

Endpoint:

in vitro gene mutation study in bacteria

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP compliant guideline study, available as unpublished report, no restrictions, fully adequate for assessment

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)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.5100 - Bacterial Reverse Mutation Test (August 1998)

GLP compliance:

yes (incl. QA statement)

Remarks:

Experimental Toxicology and Ecology BASF SE, 67055 Ludwigshafen, Germany

Type of assay:

bacterial reverse mutation assay

Target gene:

- S. typhimurium: His-locus
- Escherichia coli: Trp-locus

Species / strain / cell type:

other: S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2 uvr A

Metabolic activation:

with and without

Metabolic activation system:

Liver S9 fraction of phenobarbital/β-naphthoflavone - induced rats

Test concentrations with justification for top dose:

- 1st experiment: Standard plate test: 0, 20, 102, 510, 2550, 5100 µg/plate
- 2nd experiment: Preincubation test: 0, 318.8, 637.5, 1275, 2550, 5100 µg/plate
- 3rd experiment: Preincubation test: 0, 4, 20, 100, 500, 1000 µg/plate (TA 1535, TA 1537and TA 98 with and without S9 mix;
TA 100 and E. coli without S9 mix) and 0, 8, 40, 200, 1000, 2000 µg/plate (TA 100 and E. coli with S9 mix)
- 4rd experiment: Preincubation test: 0, 31.3, 62.5, 125, 250, 500, 750, 1000 µg/plate (TA 100 and TA 1537 without S9 mix) and 0, 62.5, 125, 250, 500, 1000, 1500, 2000 µg/plate (TA 100 with S9 mix)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: Due to the limited solubility of the test item in water, DMSO was used as vehicle, which had been demonstrated to be suitable in bacterial reverse mutation tests and for which historical control data are available.

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 2-aminoanthracene

Remarks:

with metabolic activation

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: N-methyl-N'-nitro-N-nitrosoguanidine

Remarks:

TA 1535, TA 100; without metabolic activation

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

other: 4-nitro-o-phenylenediamine

Remarks:

TA 98; without metabolic activation

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

9-aminoacridine

Remarks:

TA 1537; without metabolic activation

Untreated negative controls:

yes

Negative solvent / vehicle controls:

yes

True negative controls:

no

Positive controls:

yes

Positive control substance:

4-nitroquinoline-N-oxide

Remarks:

E. coli WP2 uvrA; without metabolic activation

Details on test system and experimental conditions:

-> 1st EXPERIMENT:
METHOD OF APPLICATION: in agar (plate incorporation)
DURATION
- Exposure duration: 48-72 hours
NUMBER OF REPLICATIONS:
-Three plates per condition
DETERMINATION OF CYTOTOXICITY
- Method: other: Toxicity detected by a decrease in the number of revertants, clearing or diminution of the background lawn (= reduced his- or trp- background growth), or reduction in the titer

-> 2nd, 3rd and 4rd EXPERIMENT:
METHOD OF APPLICATION: preincubation
DURATION
- Preincubation period: 20 minutes
- Exposure duration: 48-72 hours
NUMBER OF REPLICATIONS:
- Three plates per condition
DETERMINATION OF CYTOTOXICITY
- Method: other: Toxicity detected by a decrease in the number of revertants, clearing or diminution of the background lawn (= reduced his- or trp- background growth), or reduction in the titer

Evaluation criteria:

- The test chemical is considered positive in this assay if the following criteria are met: A dose-related and reproducible increase in the number of revertant colonies, i.e. about doubling of the spontaneous mutation rate in at least one tester strain either without S9 mix or after adding a metabolizing system.
- A test item is generally considered non-mutagenic in this test if the number of revertants for all tester strains were within the historical negative control range under all experimental conditions in at least two experiments carried out independently of each other.

Species / strain:

other: S. typhimurium TA 1535, TA 1537, TA 98, TA 100 and E. coli WP2 uvr A

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

ADDITIONAL INFORMATION ON CYTOTOXICITY:
- A weak bacteriotoxic effect (reduced his- or trp- background growth, slight decrease in the number of his+ or trp+ revertants, reduction in the titer) was observed in the standard plate test depending on the strain and test conditions from about 2 550 μg/plate onward.
- In the preincubation assay bacteriotoxicity (reduced his- or trp- background growth, decrease in the number of his+ or trp+ revertants, reduction in the titer) was observed depending on the strain and test conditions from about 500 μg/plate onward.

TEST-SPECIFIC CONFOUNDING FACTORS
- Precipitation: No precipitation was found with and without S9 mix.

Remarks on result:

other: all strains/cell types tested

Remarks:

Migrated from field 'Test system'.

Conclusions:

Interpretation of results (migrated information):
negative

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

Ames Test

The test item did not lead to a relevant increase in the number of revertant colonies either without S9 mix or after adding a metabolizing system in three experiments carried out independently of each other (standard plate test and preincubation assay). Besides, the results of the negative as well as the positive controls performed in parallel corroborated the validity of this study, since the values fulfilled the acceptance criteria of the study. In this study with and without S9 mix, the number of revertant colonies in the negative controls was within the range of the historical negative control data for each tester strain. In addition, the positive control items both with and without S9 mix induced a significant increase in the number of revertant colonies within the range of the historical positive control data or above.

Thus, under the experimental conditions, it can be concluded that Na-Hexamethyldisilazane is not a mutagenic test item in the bacterial reverse mutation test in the absence and the presence of metabolic activation. [BASF, 2009]

Justification for classification or non-classification

Dangerous Substance Directive (67/548/EEC)

The available Ames Test is considered reliable and suitable for classification purposes under 67/548/EEC. As a result the substance is not considered to be classified for genetic toxicity under Directive 67/548/EEC, as amended for the 31st time in Directive 2009/2/EG.

Classification, Labelling, and Packaging Regulation (EC) No 1272/2008

The available experimental test data is reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. As a result the substance is not considered to be classified for genetic toxicity under Regulation (EC) No 1272/2008, as amended for the sixth time in Regulation No 605/2014.