CTO

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

In two independent bacterial reverse mutation experiments (plate incorporation & preincubation) conducted on Cesium Tungsten Oxide, it concluded that the test item is not mutagenic in the "Salmonella typhimurium" strains TA97a, TA98, TA100, TA102 and TA1535 in the absence and presence of metabolic activation. Concentrations tested were 5000, 1500, 500, 150, 50 μg/plate in the first experiment and 5000, 2500, 1250, 625, 313, 156, 78 μg/plate in the second experiment.

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:

Jan 9, 2018 to Feb 1, 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)

Version / remarks:

1997

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Type of assay:

bacterial reverse mutation assay

Specific details on test material used for the study:

Test item name: Cesium Tungsten Oxide
Batch no.: B0345
Purity: >99%
Homogeneity: homogeneous

Species / strain / cell type:

S. typhimurium, other: TA97a

Details on mammalian cell type (if applicable):

Source: TRINOVA BioChem GmbH
Batch: 4997D

Species / strain / cell type:

S. typhimurium TA 98

Details on mammalian cell type (if applicable):

Source: TRINOVA BioChem GmbH
Batch: 5011D

Species / strain / cell type:

S. typhimurium TA 100

Details on mammalian cell type (if applicable):

Source: TRINOVA BioChem GmbH
Batch: 4996D

Species / strain / cell type:

S. typhimurium TA 102

Details on mammalian cell type (if applicable):

Source: TRINOVA BioChem CmbH
Batch: 4982D

Species / strain / cell type:

S. typhimurium TA 1535

Details on mammalian cell type (if applicable):

Source: TRINOVA BioCehm GmbH
Batch: 5012D

Metabolic activation:

with and without

Metabolic activation system:

S9 produced from livers of male Sprague-Dawley rats treated with Aroclor

Test concentrations with justification for top dose:

1st experiment: 5000 / 1500 / 500 / 150 / 50 μg/plate

2nd experiment: 5000 / 2500 / 1250 / 625 / 313 / 156 / 78 μg/plate

Justification for top dose: The test item showed precipitates were observed on the plates at the highest concentration only (5000 μg/plate)

Vehicle / solvent:

- Vehicle(s)/solvent(s) used: demineralized water
- Justification for choice of solvent/vehicle: Out of the three solvents tested (demin. water, DMSO, acetone), this solvent does not have any effects on the viability of the bacteria or the number of spontaneous revertants in the tested concentrations.

Negative solvent / vehicle controls:

yes

Remarks:

Dimethylsulfoxide (DMSO) and Demineralised water

Positive controls:

yes

Positive control substance:

sodium azide

benzo(a)pyrene

other: 4-Nitro-1,2-phenylene diamine, C6H7N3O2; CAS-No.: 99-56-9 2-Amino-anthracene, C14H11N; CAS-No.: 613-13-8

Details on test system and experimental conditions:

METHOD OF APPLICATION:
- First experiment: in agar (plate incorporation)
- Second experiment: preincubation

- Cell density at seeding (if applicable): 10^9 cells/mL

DURATION
- For the culture of bacteria prior to the start of the experiments: 8 hrs, overnight at 37 ± 1 °C
- For the second experiment (pre-incubation method) only: pre-incubated for 20 minutes at 37 ± 1 °C
- The titre was determined by dilution of the overnight culture using sodium chloride solution and placing 0.1 mL on maximal-soft agar. Incubation for 48 hours at 37 ±1 °C followed.


NUMBER OF REPLICATIONS: three plates with and three plates without metabolic activation (-S9) were used.

Evaluation criteria:

- colonies were counted visually and the numbers were recorded.
- a substance was considered to have mutagenic potential, if a reproducible increase of revertant colonies per plate exceeding an increase factor of 2 in at least one strain could be observed. A concentration-related increase over the range tested was also taken as a sign of mutagenic activity.

Statistics:

- 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 suspensions and the positive controls. Additionally, the absolute number of revertants (Rev. Abs.) (mean revertants minus mean spontaneous revertants) was given.

Species / strain:

S. typhimurium, other: TA97a

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 98

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

cytotoxicity

Remarks:

In the second experiment, the test item showed signs of toxicity towards the bacteria strain TA98 in both the absence and presence of metabolic activation at the highest concentration (5000 μg/plate).

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 100

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 102

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Species / strain:

S. typhimurium TA 1535

Metabolic activation:

with and without

Genotoxicity:

negative

Cytotoxicity / choice of top concentrations:

no cytotoxicity, but tested up to precipitating concentrations

Vehicle controls validity:

valid

Untreated negative controls validity:

valid

Positive controls validity:

valid

Additional information on results:

Concentrations of the test item are stated as nominal concentrations, as suspensions had to be tested due to the poor solubility of the test item. As no complete dissolution was possible, undissolved particles were visible on the plates, only at the highest concentrations.

Observations from the First experiment (plate incorporation method):

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. All determined values for the spontaneous revertants of the negative controls were in the normal range of the test laboratory (historical data of the laboratory). All positive controls showed mutagenic effects with and without metabolic activation and were within the historical control data ranges.

 

Solubility and Toxicity

In the first experiment, the test item showed precipitates were observed on the plates at the highest concentration only (5000 μg/plate). 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 significant 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.

 

Observations from the Second experiment (preincubation method):

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. All determined values for the spontaneous revertants of the negative controls were in the normal range of the test laboratory (historical data of the laboratory). All positive controls showed mutagenic effects with and without metabolic activation and were within the historical control data ranges.

 

Solubility and Toxicity

In the second experiment, the test item showed precipitates on the plates at the highest concentration. The bacterial background lawn was not reduced at any of the concentrations, but a relevant decrease in the number of revertants was observed in the bacteria strain TA98 at the highest concentration (5000 μg/plate), only. The test item showed signs of toxicity towards the bacteria strain TA98 in both the absence and presence of metabolic activation at the highest concentration (5000 μg/plate).

 

Mutagenicity

No significant 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.

Conclusions:

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

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Justification for classification or non-classification

In two independent bacterial reverse mutation experiments (plate incorporation & preincubation) conducted on Cesium Tungsten Oxide, it concluded that the test item is not mutagenic in the "Salmonella typhimurium" strains TA97a, TA98, TA100, TA102 and TA1535 in the absence and presence of metabolic activation . Therefore, the test substance does not meet the Regulation (EC) No 1272/2008 as amended criteria for Germ Cell Mutagenicity classification.