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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information
An Ames test (Sokolowski, 2008) is available which is key study. This study showed that the test substance is not mutagenic.
Link to relevant study records
Reference
Endpoint:
in vitro gene mutation study in bacteria
Remarks:
Type of genotoxicity: gene mutation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From 17 December 2007 to 22 January 2008
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study run to a method comparable with current guidelines and to GLP
Qualifier:
according to
Guideline:
OECD Guideline 471 (Bacterial Reverse Mutation Assay)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Type of assay:
bacterial reverse mutation assay
Target gene:
Salmonella typhimurium: histidine
E. coli: tryptophan
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Species / strain / cell type:
E. coli WP2 uvr A
Metabolic activation:
with and without
Metabolic activation system:
S9 mix
Test concentrations with justification for top dose:
Pre-Experiment/Experiment I: 3, 10, 33, 100, 333, 1000, 2500 and 5000 μg/plate
Experiment II: 10, 33, 100, 333, 1000, 2500 and 5000 μg/plate
Vehicle / solvent:
- Vehicle(s)/solvent(s) used: DMSO
- Justification for choice of solvent/vehicle: The solvent was chosen because of its solubility properties and its relative non-toxicity to the bacteria.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
sodium azide
Remarks:
In the absence of S9 mix for strains TA 1535 and TA 100.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 4-nitro-o-phenylene-diamine
Remarks:
In the absence of S9 mix for strains TA 1537 and TA 98.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
methylmethanesulfonate
Remarks:
In the absence of S9 mix for strain WP2 uvrA.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
yes
True negative controls:
no
Positive controls:
yes
Positive control substance:
other: 2-aminoanthracene
Remarks:
In the presence of S9 mix for all strains.
Details on test system and experimental conditions:
Test System:
Salmonella typhimurium Strains and E. coli Strain

Storage:
The strain cultures were stored as stock cultures in ampoules with nutrient broth + 5 % DMSO in liquid nitrogen.

Precultures:
From the thawed ampoules of the strains 0.5 mL suspension was transferred into 250 mL Erlenmeyer flasks containing 20 mL nutrient medium. A solution of 20µL ampicillin (25 µg/mL) was added to the strains TA 98 and TA 100. This nutrient medium contains per litre: 8 g Nutrient Broth and 5 g NaCl.
The bacterial cultures were incubated in a shaking water bath for 4 hours at 37℃.

Selective Agar:
The plates with the selective agar were obtained.

Overlay Agar:
The overlay agar contains per litre:
For Salmonella strains: 6.0 g Agar Agar, 6.0 g NaCl, 10.5 mg L-Histidine.HCl.H2O and 12.2 mg Biotin.
For Escherichia coli: 6.0 g Agar Agar, 6.0 g NaCl and 2.5 mg Tryptophan.
Sterilisations were performed at 121℃ in an autoclave.
Evaluation criteria:
A test item is considered as a mutagen if a biologically relevant increase in the number of revertants exceeding the threshold of twice (strains TA 98, TA 100, and WP2 uvrA) or thrice (strains TA 1535 and TA 1537) the colony count of the corresponding solvent control is observed.

A dose dependent increase is considered biologically relevant if the threshold is exceeded at more than one concentration.

An increase exceeding the threshold at only one concentration is judged as biologically relevant if reproduced in an independent second experiment.

A dose dependent increase in the number of revertant colonies below the threshold is regarded as an indication of a mutagenic potential if reproduced in an independent second experiment. However, whenever the colony counts remain within the historical range of negative and solvent controls such an increase is not considered biologically relevant.
Statistics:
None stated
Species / strain:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Metabolic activation:
with and without
Genotoxicity:
negative
Cytotoxicity / choice of top concentrations:
cytotoxicity
Vehicle controls validity:
valid
Positive controls validity:
valid
Species / strain:
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:
Minor toxic effects, evident as a reduction in the number of revertants, occurred in nearly all strains.

No substantial increase in revertant colony numbers of any of the five tester strains was observed following treatment with the test substance at any dose level, neither in the presence nor absence of metabolic activation (S9 mix). There was also no tendency of higher mutation rates with increasing concentrations in the range below the generally acknowledged border of biological relevance.

Appropriate reference mutagens were used as positive controls and showed a distinct increase of induced revertant colonies.
Remarks on result:
other: all strains/cell types tested
Remarks:
Migrated from field 'Test system'.
Conclusions:
Interpretation of results (migrated information):
negative

The test substance is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.
Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

An Ames test was conducted according to OECD 471 using S. typhimurium strains and E. coli strain (Sokolowski, 2008). Key study. The test substance is considered to be non-mutagenic in this Salmonella typhimurium and Escherichia coli reverse mutation assay.


Justification for selection of genetic toxicity endpoint
This study was conducted according to OECD 471 under GLP.

Justification for classification or non-classification

Genetic toxicity: Ames test give negative result (Not mutagenic to S. typhimurium strains and E. coli strain).

Therefore in accordance with Regulation (EC) No. 1272/2008 Table 3.5.1 the substance is not classified for genetic toxicity endpoint.