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Diss Factsheets

Administrative data

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Non mutagenic

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

Genetic toxicity in vivo

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

Justification for classification or non-classification


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.

Category 1: Substances known to induce heritable mutations or to be regarded as if they induce heritable mutations in the germ cells of humans. Substances known to induce heritable mutations in the germ cells of humans.

Categoty 2: Substances which cause concern for humans owing to the possibility that they may induce heritable mutations in the germ cells of humans.

Classification for heritable effects in human germ cells is made on the basis of well conducted, sufficiently validated tests as In vitro mutagenicity tests such as these indicated in

- in vitro mammalian chromosome aberration test;

- in vitro mammalian cell gene mutation test;

- bacterial reverse mutation tests

The test item resulted to be positive in the Ames test, but negative in the mutation assay in mammalian cells and in the chromosomal aberration one. This positive effect in the bacterial mutation assay is a bacteria-specific effect due to bacterial nitro-reductases, which are highly effective in these bacterial strains, but not in mammalian cells. It is well-known for aromatic nitro compounds to be positive in the Ames assay resulting from metabolism by the bacteria-specific enzyme nitro-reductase [Tweats et al. 2012]. However, it has been demonstrated in various publications that this is a bacteria-specific effect and that these Ames positive substances are not mutagenic in mammalian assays. The nitroreductase family comprises a group of flavin mononucleotide (FMN)- or flavin adenine dinucleotide (FAD) -dependent enzymes that are able to metabolize nitroaromatic and nitroheterocyclic derivatives (nitrosubstituted compounds) using the reducing power of nicotinamide adenine dinucleotide (NAD(P)H). These enzymes can be found in bacterial species and, to a lesser extent, in eukaryotes. The nitroreductase proteins play a central role in the activation of nitrocompounds [de Oliveira et al. 2010]. That the reduction of these nitro-compounds to mutagenic metabolites is a bacteria-specific effect has demonstrated in the past for two compounds pharmaceutical compounds AMP397 and fexinidazole as well as for a number of dye chemicals harvesting one or more nitro-groups within their chemical structure.

In conclusion, based on these data and the common mechanism between the reduction of these nitro-compounds, which is widely explored in literature [de Oliveira et al. 2010], it is concluded, that the mutagenic effects observed in the Ames test is a bacteria specific effect and not relevant to mammalians. Therefore the test substance is Not classified.