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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

In a study according to OECD TG 471 under GLP conditions, the read-across source substance was not mutagenic in five strains (TA98, TA100, TA1535, TA1537 (all Salmonella typhimurium) and WP2 uvrA (E. coli)) with and without metabolic activation (S9) (reference 7.6.1 -1).

Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in bacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to section 13 for the read-across justification.
Reason / purpose for cross-reference:
read-across source
Key result
Species / strain:
S. typhimurium TA 98
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
True negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
True negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1535
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
True negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
S. typhimurium TA 1537
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
True negative controls validity:
not applicable
Positive controls validity:
valid
Key result
Species / strain:
E. coli WP2 uvr A
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
no cytotoxicity
Vehicle controls validity:
valid
Untreated negative controls validity:
valid
True negative controls validity:
not applicable
Positive controls validity:
valid
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

No study data with the test item is available for genetic toxicity. Therefore, a read-across to the read-across source substance with a very similar chemical structure and comparable physico-chemical parameters is used to evaluate the genetic toxicity potential of the test item.


A study according OECD TG 471 was performed with regard to a potential mutagenic activity using the Bacterial Reverse Mutation Assay. The experiments were carried out using histidine-requiring auxotroph strains of Salmonella typhimurium (Salmonella typhimurium TA98, TA100, TA1535 and TA1537), and the tryptophan-requiring auxotroph strain of Escherichia coli (Escherichia coli WP2uvrA) in the presence and absence of a post mitochondrial supernatant (S9) prepared from livers of Phenobarbital/β-naphthoflavone-induced rats.


The study included a Preliminary Solubility Test, a Preliminary Range Finding Test (Informatory Toxicity Test), an Initial Mutation Test (Plate Incorporation Test), and a Confirmatory Mutation Test (Pre-Incubation Test). Based on the results of the Solubility and the Range Finding Tests the test item was dissolved in ultrapure water (ASTM Type 1). This vehicle was compatible with the survival of the bacteria and the S9 activity. Based on the results of the preliminary Range Finding Test the following concentrations of the test item were prepared and investigated in the Initial and Confirmatory Mutation Tests: 5000; 1600; 500; 160; 50 and 16 μg/plate. In the preliminary experiments the pH of the aqueous test item solution (50 mg/mL) was found as 3.47. Extremes of pH could have influencing effect on the mutagenicity results, therefore in the Initial and Confirmatory Mutation Tests the pH of the test item stock solution (prepared for the highest concentration of 50 mg/mL) and additionally the pH of the overlay (top agar-phosphate buffer-test item system (at 50 mg/mL)) was checked and recorded. The pH values of the test item stock solutions (50 mg/mL) were 3.50 and 3.52. The pH of the test item containing overlays was ~7 in both experiments. In this study the acidic test item solutions had only slight effect on the buffered overlay system. Unequivocal negative results were obtained and the additional information about the pH conditions was not involved into the mutagenicity result interpretation.


No precipitation of the test item was observed on the plates in the examined bacterial strains at any examined concentration level (±S9 Mix) throughout the study.


The test item did not show inhibitory, cytotoxic effects in the performed experiments. The colony and background lawn development was not affected in any case; the obtained revertant colony number decreases (compared to the revertant colony numbers of the vehicle control) remained within the biological variability range of the applied test system.


The revertant colony numbers of vehicle control (ultrapure water) plates with and without S9 Mix demonstrated the characteristic mean number of spontaneous revertants that was in line with the corresponding historical control data ranges. The reference mutagen treatments (positive controls) showed the expected, biological relevant increases in induced revertant colonies in all experimental phases, in all tester strains, thus, showing the expected reversion properties of all strains and good metabolic activity of the S9 mix used.


No biologically relevant increases were observed in revertant colony numbers of any of the five test strains following treatment with the substance at any concentration level, either in the presence or absence of metabolic activation (S9 Mix) in the performed experiments.


The reported data of this mutagenicity assay show that under the experimental conditions applied, the test item did not induce gene mutations by base pair changes or frameshifts in the genome of the bacterium tester strains used.


In conclusion, the test item has no mutagenic activity on the applied bacterium tester strains under the test conditions used in this study.


Based on the data from the read-across source substance, the target substance is determined to have no mutagenic activity on bacterium tester strains.

Justification for classification or non-classification

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


The available test data are reliable and suitable for classification purposes under Regulation (EC) No 1272/2008. Thus, the test item is considered not to be classified for genotoxicity under Regulation (EC) No 1272/2008, amended for the fifteenth time in Regulation (EU) 2020/1182.