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Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information
The genotoxic potential of the test substance was assessed using a modified Ames test in which potential mutagens were screened using spot tests. The test substance was not found to be mutagenic under the conditions of the test, both with and without metabolic activation.
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:
supporting study
Study period:
The study was conducted in 1980.
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
other: Study is well conducted but its design is not sufficient to cover the endpoint.
Qualifier:
no guideline followed
Deviations:
not applicable
Principles of method if other than guideline:
Substances were assayed for mutagenicity towards four histidine-requiring mutants of Salmonella typhimurium (TA 98, TA 100, TA1535 and TA 1537). The test was performed with and without metabolic activation using a liver fraction (S-9) from Aroclor 1254 of methylchloanthrene induced rats using a modified Ames test. Due to the large number of compounds screened during the study potential mutagens were screened using spot tests which are less sensitive than quantitative experiments.
GLP compliance:
not specified
Type of assay:
bacterial reverse mutation assay
Target gene:
Histidine
Species / strain / cell type:
S. typhimurium TA 1535, TA 1537, TA 98 and TA 100
Additional strain / cell type characteristics:
not specified
Metabolic activation:
with and without
Metabolic activation system:
S9 mix
Test concentrations with justification for top dose:
3 µmol/plate
Vehicle / solvent:
Ethanol.
Untreated negative controls:
yes
Negative solvent / vehicle controls:
no
True negative controls:
no
Positive controls:
yes
Positive control substance:
N-ethyl-N-nitro-N-nitrosoguanidine
other: 2-aminoanthracene
Details on test system and experimental conditions:
Revertants were scored on glucosen minimal salts medium supplemented with 0.05 µmol histidine and 0.05 µmol biotin. Plates used for viable counts contained 10 µmol histidine (and 0.05 µmol biotin).

The following controls were made for each experiment
The viable count was determined.
The number of spontaneous revertants was measured.
The presence of the rfa-mutation was checked by crystal violet inhibition.
The presence of the plasmid pKM 101 in strains TA98 and TA100 was checked by resistance to ampicillin.
The response of the positive controls, N-methyl-N'-nitro-N-nitrosoguanidin (not requiring metabolic activation) and 2-aminoanthracene (requiring activation) was checked.
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:
no cytotoxicity
Vehicle controls validity:
not examined
Untreated negative controls validity:
not specified
Positive controls validity:
not specified
Additional information on results:
The test substance was not found to be mutagenic.
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 was not found to be mutagenic.
Executive summary:

The genotixic potential of the test substance was assessed using a modified Ames test in which potential mutagens were screened using spot tests. The test substance was not found to be mutagenic under the conditions of the test, both with and without metabolic activation.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (negative)

Additional information

Additional information from genetic toxicity in vitro:

Substances were assayed for mutagenicity towards four histidine-requiring mutants of Salmonella typhimurium (TA 98, TA 100, TA1535 and TA 1537). The test was performed with and without metabolic activation using a liver fraction (S-9) from Aroclor 1254 of methylchloanthrene induced rats using a modified Ames test. Due to the large number of compounds screened during the study potential mutagens were screened using spot tests which are less sensitive than quantitative experiments. 

The test substance was not found to be mutagenic under the conditions of the test.


Justification for selection of genetic toxicity endpoint
The study was conducted on the target substance in appropriate test species.

Justification for classification or non-classification

A mutation is a permanent change in the amount or structure of the genetic material in a cell. The term “mutation” applies to both heritable genetic changes that may be manifested at the phenotypic level and to the underlying DNA modifications when known, including specific base pair changes and chromosomal translocations. The term “mutagenic” and “mutagen” are used for agents giving rise to an increased occurrence of mutations in populations of cells or organisms.

The more generic terms “genotoxic” and “genotoxicity” apply to agents or processes which alter the structure, information content or segregation of DNA, including those which cause DNA damage by interfering with normal replication processes, or which in a non-physiological manner temporarily alter its replication. Genotoxicity test results are usually taken as indicators for mutagenic effects.

This hazard class is primarily concerned with substances that may cause mutations in the germ cells of humans that can be transmitted to the progeny. However, the results from mutagenicity or genotoxicity tests in vitro and in mammalian somatic and germ cells in vivo are also considered in classifying substances and mixtures within this hazard class.

To arrive at a classification, test results are considered from experiments determining mutagenic and genotoxic effects in germ and/or somatic cells of exposed animals and in in vitro tests.

The system is hazard based, classifying substances on the basis of their intrinsic ability to induce mutations in germs cells, and does not give a quantitative assessment of the risk.

An in vitro study was performed on the target substance and concluded that no significant increases in the frequency of revertant colonies were recorded for any of the bacterial strains, either with or without metabolic activation. The test substance is therefore not classified for genotoxicity.