N,N'-diphenyl-p-phenylenediamine

Endpoint summary

Key value for chemical safety assessment

Genetic toxicity in vitro

Description of key information

Three in vitro genetic toxicity tests were performed by BASF SE: an Ames test (OECD TG 471, study no. 40M0045/16M145, 2016), a chromosome aberration test (OECD TG 473, study no. 32M0045/16M004, 2017) and a gene mutation test in mouse lymphoma cells (OECD TG 476, study no. 52M0045/16M005, 2017). These studies are reported as key studies.

In the Ames test, a relevant and dose-dependent increase in the number of his+ revertants exceeding a factor of 3 compared to the concurrent vehicle control was observed in the presence of S9 mix in salmonella tester strain TA 1537. A single increase at one concentration was found in TA 1535 with S9 mix. The test compound was considered mutagenic in the presence of metabolic activation based on these findings.

In the chromosome aberration test, the test substance caused a statistically significant and dose-dependent increase in the number of structurally aberrant metaphases incl. and excl. gaps in the absence of metabolic activation. Based on these findings, the test substance was considered to have a clastogenic potential under in vitro conditions without metabolic activation.

Finally, a clear, statistically significant and dose-dependent increase in mutant frequences either with or without metabolic activation was found in test-substance treated L5178Y TK+/- cells in the mammalian cell gene mutation test.

Evidence supporting these results is available from a GLP-compliant mammalian cell gene mutation test in mouse lymphoma cells published by US EPA (OTS0545453, 1987), where an increased mutant frequency of at least twice the mean mutant frequency in solvent controls was observed in the absence of metabolic activation. In a GLP-compliant published chromosome aberration test in CHO cells (US EPA, OTS0545526, 1988), a significant increase in chromosome aberrations was observed. Due to the statistically significant increase in structural aberrations at a single concentration at each of the harvest times (12 hour nonactivated study and 24 hour S-9 activated study) and the fact that at many of the concertation’s tested less than 100 cells were located for chromosome evaluation due to severe mitotic inhibition, the results from this study are considered equivocal.

Zeiger et al. (1992) reported that DPPD caused increased mutant frequencies in the Ames test in salmonella strains TA98 and TA100 in the presence of S9 mix. Sofuni et al. (1990) reported increased frequencies of aberrant cells in a chromosome aberration test in CHL cells without metabolic activation. No evidence of chromosomal aberration was found in CHO cells the same publication.

Justification for classification or non-classification

Based on the positive findings in bacterial and mammalian cell gene mutations tests and chromosome aberration tests in mammalian cell culture, a classification into Muta. Cat. 2 (H341) is proposed. This classification proposal is supported, in addition to the in vitro test findings, by the structural similarity of DPPD to known genotoxins, as demonstrated by QSAR predictions for chromosomal aberration and bacterial mutagenicity, as well as protein binding alerts for chromosomal aberration by OASIS v1.2, identified via the OECD toolbox (see chapter 13 for attache ddocuments).