Hydrogen [2,4-dihydro-4-[(2-hydroxy-4-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)][2,4-dihydro-4-[(2-hydroxy-5-nitrophenyl)azo]-5-methyl-2-phenyl-3H-pyrazol-3-onato(2-)]chromate(1-)

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Gene mutation assays in bacteria: An AMES test is in progress and expected to be negative. Another AMES test on similar Substance resulted negative.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (negative)

Genetic toxicity in vivo

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information

Mutagenicity testing strategy is reported in ECHA Guidance Chapter R.7a: Endpoint specific guidance, Version 4.0 – July 2015.

A preliminary assessment of mutagenicity should normally includes data from a gene mutation test in bacteria unless existing data for analogous substances indicates this would be inappropriate.

When the result of the bacterial test is positive, it is important to consider the possibility of the substance being genotoxic in mammalian cells.

In order to ensure the necessary minimum level of information is provided, at least a further test is required in addition to the gene mutation test in bacteria. This should be an in vitro mammalian cell test capable of detecting both structural and numerical chromosome aberrations. A suitable option is in vitro chromosome aberration test (OECD guideline 473), i.e. a cytogenetic assay for structural chromosome aberrations using metaphase analysis.

An in vitro gene mutation study in mammalian cells (OECD guideline 476) is the second part of the standard information set usually required, when the results of the bacterial gene mutation test and the first study in mammalian cells (i.e. an in vitro chromosome aberration test or an in vitro micronucleus test) are negative. This is to detect in vitro mutagens that give negative results in the other tests.

Substances for which mammalian cell tests are negative while bacterial test is positive should be evaluated for any further testing on a case-by-case basis. If available, an in vivo test may be used in the assessment.

In general, substances that are positive in the gene mutation test in bacteria, negative in in vitro tests of chromosome aberration or micronucleus and negative in an in vivo test, e.g. micronucleus test, are considered to be non-genotoxic.

An amest test in progress on the target substance and expected to be negative. Another AMES test on a similar substance 01 is available.

Target substance and read across substances are chromium complexes with 2 ligands. In all cases, the 2 ligands have the same chemical structure, i.e. a phenyl ring connected via diazo bond to a phenyl pyrazole. These ligands show minor differences in the position of substituents, i.e. hydroxy and nitro groups, in both read across substances.

All information about the read across choice is inserted in section 13.

The read across substance was evaluated for the potential mutagenic activity in the plate incorporation AMES assay. . In particular, 5 different strains, namely TA 98, TA 100, TA 1535, TA 1537 and TA 1538, were tested in the plate incorporation test in presence and in absence of metabolic activation (S9 mix). Tested doses were 1.58, 5, 15.8, 50, 158, 500, 1580 and 5000 µg/plate and each of them, including controls, was tested in triplicate. Positive and negative control results were valid. No toxic effects were noted up to the highest concentration.

In this study, no sign of mutagenic activity of test substance was reported.

In summary, the assessement on the genotoxic potential test substance was found to be:

- negative, as for gene mutation in bacteria

Justification for classification or non-classification

According to the CLP Regulation (EC 1272/2008), Annex I, Part 3, substances which cause concern for humans owing to the possibility that they may induce heritable mutations in the germ cells of humans are classified in Category 2. This classification is based on positive evidence obtained in:

— somatic cell mutagenicity tests in vivo, in mammals; or

— other in vivo somatic cell genotoxicity tests which are supported by positive results from in vitro mutagenicity assays.

Note: substances which are positive in in vitro mammalian mutagenicity assays, and which also show chemical structure activity relationship to known germ cell mutagens, shall be considered for classification as Category 2 mutagens.

In vitro mutagenicity tests are the following:

— in vitro mammalian chromosome aberration test;

— in vitro mammalian cell gene mutation test;

— bacterial reverse mutation tests.

The overall assessement on the genotoxic potential of test substance was based on: negative outcomes in bacterial reverse mutation assay (AMES test) on similar substance 01 and expected negative outcome on the target substance based on the AMES test in progress.

All studies were conducted according to OECD guidelines and have a high reliability. Differences with respect to current versions of guidelines, do not significantly influence the overall evaluation, which was thus taken as valid and reliable.

Based on these results, which fulfil the mutagenicity testing strategy required by Annex VII and VIII of the REACH Regulation (EC 1907/2006), the test susbstance was considered as non genotoxic and it was not classified within the CLP Regulation (EC 1272/2008).