Sodium bis[1-[(2-hydroxy-5-nitrophenyl)azo]-2-naphtholato(2-)]chromate(1-)

Genetic toxicity: in vivo

Administrative data

Endpoint:

in vivo mammalian somatic cell study: gene mutation

Type of information:

other: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

Not yet defined

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Justification for type of information:

NON-CONFIDENTIAL NAME OF SUBSTANCE:
- Name of the substance on which testing is proposed to be carried out: analogue substance 01

CONSIDERATIONS THAT THE GENERAL ADAPTATION POSSIBILITIES OF ANNEX XI OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION
This part refers to the available studies on the target substance Acid Black 63:2 (EC: 260-616-2):
- Available GLP studies:
In vitro gene mutation study in bacteria (OECD TG 471) – NR-deficient strains.
- Available non-GLP studies: not available.
- Historical human data: not available.
- (Q)SAR: not available.
- Weight of evidence: not available.
- Grouping and read-across:
In vitro gene mutation study in bacteria (OECD TG 471) – Read-Across on analogue substance 01.
In vitro gene mutation in mammalian cells (OECD TG 476) – Read-Across on analogue substance 01.
In vitro cytogenicity/micronucleus study (OECD TG 487) – Read-Across on analogue substance 01.

CONSIDERATIONS THAT THE SPECIFIC ADAPTATION POSSIBILITIES OF ANNEXES VI TO X (AND COLUMN 2 THEREOF) OF THE REACH REGULATION ARE NOT ADEQUATE TO GENERATE THE NECESSARY INFORMATION:
Under Annex VIII Section 8.4., column 2 of REACH, further mutagenicity studies must be considered in case of a positive result in an in vitro gene mutation study in bacteria.
Guidance on information requirements R7a, section 7.7.6 (2017), states that regarding Annex VIII, when both the mammalian cell tests are negative but there was a positive result in the bacterial test, it will be necessary to decide whether any further testing is needed on a case-by-case basis. For example, suspicion that a unique positive response observed in the bacterial test was due to a specific bacterial metabolism of the test substance could be explored further by investigation in vitro. Alternatively, an in vivo test may be required.
The submitted dossier contains results for the in vitro gene mutation study in bacteria, following the OECD TG 471 with nitro-reductase deficient strains, which raises the concern for in vivo gene mutation, since the influence of the nitro-reductase is demonstrated but needs further evidence.
In particular, annex VIII, Column 2 requires the registrant to consider appropriate mutagenicity in vivo studies already at the Annex VIII tonnage level, which involves studies mentioned in Annex IX (among OECD TG 474 Mammalian Erythrocyte micronucleus test, OECD TG 488 Transgenic Rodent Mutation Assay, OECD TG 489 In vivo mammalian Alkaline Comet Assay and OECD TG 486 Unscheduled DNA Synthesis).

CONSIDERATIONS ON THE IN VIVO STUDIES INSERTED IN THE DOSSIER AND EXPERT ASSESSMENT ON TESTING PROPOSAL
There are no in vivo studies conducted on the target substance or on similar substances, submitted with the present dossier.

Therefore, in order to further and completely assess its gene mutation properties in different tissues of the animal, a Comet Assay, OECD TG 489, on analogue substance 01 was presented as testing proposal and it will be also used in read across for assessing the in vivo potential gene mutation properties of the target substance Acid Black 63:2 (EC: 260-616-2).
Analogue substance 01 is, in fact, considered as representative of the mutagenic behavior of Acid Black 63:2 (EC: 260-616-2) as specified in the read-across section.
OECD TG 489 allows to measure DNA strand breaks, that may result from direct interactions with DNA, alkali labile sites or as a consequence of incomplete excision repair. Therefore, the alkaline comet assay recognizes primary DNA damage that would lead to gene mutations and/or chromosome aberrations, but will also detect DNA damage that may be effectively repaired or lead to cell death. The comet assay can be applied to almost every tissue of an animal from which single cell or nuclei suspensions can be made, including specific site of contact tissues.

Therefore, a confirmation by the Comet assay (for azo dyes the intestinal tract is the site of major metabolism and dye/metabolites absorption) would be sufficient to assess the genotoxic potential of the substance.

Finally, as reported in literature, from the analysis of 91 chemicals with published data from Comet Assay and Transgenic rodent mutation assay (TGR), the comet assay appears to yield similar results to the TGR assay in liver and gastrointestinal tract (predominantly stomach and colon data) and, hence, can be confidently performed to confirm in vivo gene mutation activity in terms of genotoxicity in general.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 489 (In vivo Mammalian Alkaline Comet Assay)

GLP compliance:

yes

Type of assay:

mammalian comet assay

Test material

Test material information

Constituent 1

Reference substance name:

Similar Substance #1

IUPAC Name:

Similar Substance #1

Test material form:

solid: particulate/powder

Results and discussion

Test results

Sex:

not specified

Genotoxicity:

other: to be performed

Remarks on result:

other: the test is in read-across from a submitted testing proposal still under evaluation.