o-toluidine

Endpoint summary

Additional information

There are several publications available in which the test of o-toluidine respective its hydrochloride for gene mutations in bacteria (Ames test, OECD TG 471) are reported. The following species and strains were used: Salmonella typhimurium TA 98, TA100, TA1535, TA1537, TA102, TA104, and Escherichia coli WP2urA, WP2urA/pKM101 without S9-mix and with S9-mix prepared from hamster or rat livers (e.g. JETOC 1997, Rexroat 1985, Zeiger 1985 und 1992). o-Toluidine did not reveal mutagenic activity neither with nor without a metabolic activation system, except in S typh TA 100 in the presence of 30% S9-mix prepared from hamster liver. Regarding gene mutation tests in mammalian cell systems (HPRT, MLA; e.g. Kuroda 1985, Fox 1985, Myhr 1985, Amacher 1985) the available results are inconsistent: Kuroda and Myhr observed mutagenic activity in the HPRT- resp MLA-test in the absence of a metabolic activation system whereas Fox and Amacher evaluated o-toluidine as non-mutagenic in the HPRT- resp MLA- test in both, with and without an activation system.

o-toluidine was also tested for its ability to induce chromosomal aberrations in Chinese hamster ovary cells in vitro (Gulati 1985) and in an in vitro MNT test in human lymphocytes (Vian 1993), both in the presence and in the absence of a metabolic activation system. o-Toluidine showed clear clastogenic activity in vitro in both protocols. However, regarding the in vivo tests for clastogenic activity these results cannot be confirmed as seen in the publications e.g. of NcFee 1989 and Nakai 1994 in which negative results in an in vivo MNT and in vivo Chromosome aberration tests are reported.

Thus, the described in vitro and in vivo tests show the genotoxicity test results typical for the class of aromatic amines. o-Toluidine shows positive and negative results in point mutation assays and clear clastogenic activity in vitro which could not be confirmed by the respective in vivo tests. This evaluation is in line with the evaluation of the OECD /SIDS of o-toluidine, published by UNEP in 2006.

Justification for selection of genetic toxicity endpoint
No special test is selected because there are reliable publications reporting valid studies for all three types of in-vitro mutagenicity tests as required by REACH : Mutagenicity tests in bacteria and in mammalian cell systems and chromosome aberration tests in mammalian cell systems. All these tests are therfore evaluated with Klimisch Score 2. However, there are positive and negative results in each test system reflecting the typical situation with aromatic amines.

Short description of key information:
The described in vitro and in vivo tests show the genotoxicity test results typical for the class of aromatic amines. o-Toluidine shows positive and negative results in point mutation assays and clear clastogenic activity in vitro which could not be confirmed by the respective in vivo tests. This evaluation is in line with the evaluation of the OECD /SIDS of o-toluidine, published by UNEP in 2006

Endpoint Conclusion: Adverse effect observed (positive)

Justification for classification or non-classification

the described in vitro and in vivo testsshow the genotocicity test results typical for the class of aromatic amines o-Toluidine itself was tested positive for mutagenicity in an in vitro mammalian cell gene mutation assay with L5178Y (TK+/TK-) mouse lymphoma cells. o-Toluidine showed positive results tests with mammalian cell systems (HPRT, micronucleus in lymphocyte, chromosome aberration).

Therefore it is suggested to classify o-toluidine as Category 3 (DSD-DPD) and Category 2 (GHS) Mutagen.