4-chloroaniline

Endpoint summary

Additional information

The genotoxicity data in vitro are inconsistent. p-Chloroaniline is mainly negative in the Salmonella/microsome test up to the concentration of 1000 µg/plate. The same applies to the reversion test in E.coli. Other genotoxicity tests (Pol A test in Escherichia coli, mitotic recombination in Saccharomyces cerevisiae and reversion tests in Aspergillus nidulans) have sometimes been positive and sometimes negative. In rat hepatocytes in vitro UDS tests, p-chloroaniline has shown both positive and negative results,. p-Chloroaniline is positive in the mouse lymphoma assay. No clear results have been obtained in test for chromosome aberrations and sister chromatid exchange in Chinese hamster ovary (CHO) cells.

In vivo a valid micronucleus assay in mice with a single oral dose of 180 mg/kg bw revealed a negative response (key study). Another micronucleus assay in mice with limited documentation confirmed the lack of increase of micronuclei at oral doses of up to three daily doses of 200 mg/kg, whereas a positive response was mentioned at the high dose of 300 mg/kg bw administered for three days. For the assessment of this positive result at three daily doses of 300 mg/kg bw it needs to be considered that this dose is in the range of the acute oral LD50. For a substance with methemoglobinemia as a primary mechanism of toxicity and related changes secondary to hemolysis (e.g. regenerative anemia) it is highly likely that at such a high dose the result is confounded by the systemic toxicity. Therefore based on the two available micronucleus assays that both revealed a negative result up to a dose around half of the LD50 it is concluded that there is no evidence of a relevant clastogenic potential in vivo.

A positive response was described in an early exploratory Comet assay in vivo in mice that was not performed according to current test guideline at the high single dose tested (200 mg/kg). However, as the study is of limited reliability and the Comet assay is an indicator test with local organ toxicity as a known confounder this study is of limited relevance for the overall assessment. No DNA adducts were observed in the rat after oral dosing.

Overall, considering all data together it can be concluded, that there is evidence of a weak p-chloroaniline related genotoxicity in vitro. However, based on the available in vivo studies and in line with the data available for structurally related substances (e.g. aniline) there is no evidence of DNA binding and a primary genotoxic activity in vivo, but the effects observed in vivo are judged to be secondary high dose effects. For comparison: the NOAEL in a 13 week study in rats with p-chloroaniline was < 5 mg/kg bw/day based on dose dependent methemoglobinemia and secondary anemia as well as increased spleen weight and histopathological effect in the bone marrow (hyperplasia), spleen (hematopoiesis, hemosiderosis, congestion) and kidney (hemosiderosis) (NTP 1989). In the two year study in male rats the NOAEL for non-neoplastic lesions in the spleen (fibrosis) was < 2 mg/kg, whereas sarcoma of the spleen were increased at 18 mg/kg.

Also the tumour response in the available long term studies does not point to a genotoxic mode of action. Tumours were observed mainly in the spleen and the adrenals and are regarded to be related to secondary mechanisms as a result of the hematotoxic activity. Reactive Oxygen Species might play a major role for the secondary tumour response.

Short description of key information:
In vitro:
Gene mutation (Bacterial reversion assay/Ames test): S. typhimurium TA 98 positive with metabolic activation, S. typhimurium TA 100 in the presence of hamster S9 only.

Mouse lymphoma L5178Y cells, TK+/- assay: positive

CHO cells, chromosome aberration: positive
In vivo: A valid micronucleus assay in mice with a single oral dose of 180 mg/kg bw revealed a negative response (key study). Another micronucleus assay in mice with limited documentation confirmed the lack of increase of micronuclei at oral doses of up to three daily doses of 200 mg/kg, whereas a positive response was mentioned at the high dose of 300 mg/kg bw administered for three days. No DNA adducts were observed in the rat after oral dosing.


Overall conclusion: p-chloroaniline is not a primary gentoxic substance in vivo.

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

p-Chloroaniline is positiv in some in-vitro assays but there is no evidence of a primary genotoxic activity in vivo.