International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 27 (1982) (p. 155)

CAS No.: 95-53-4
Chem. Abstr. Name: Benzenamine, 2-methyl-

ortho-Toluidine hydrochloride
CAS No.: 636-21-5
Chem. Abstr. Name: Benzenamine, 2-methyl-, hydrochloride

5. Summary of Data Reported and Evaluation

5.1 Experimental data

ortho-Toluidine hydrochloride was tested in several experiments, but only two experiments in mice and two experiments in rats by oral administration were adequate. It was carcinogenic in mice, producing hepatocellular carcinomas or adenomas in females and haemangiosarcomas at all sites in males of one strain and haemangiosarcomas and haemangiomas of abdominal viscera in animals of both sexes of another strain. It was carcinogenic in rats: in animals of one strain it produced sarcomas of multiple organs in animals of both sexes, fibromas of the subcutaneous tissue and mesotheliomas in males; and sarcomas of the spleen, transitional-cell papillomas and carcinomas of the urinary bladder and mammary gland fibroadenomas and adenomas in females. In male rats of another strain it produced subcutaneous fibromas and fibrosarcomas as well as a slight increase in the incidence of multiple tumours, including transitional-cell carcinomas of the urinary bladder.

ortho-Toluidine gave positive results in Escherichia coli DNA-repair and phage-induction assays, but it was not mutagenic in Salmonella typhimurium unless tested in the presence of both norharman and a metabolic activation system. Urine concentrates from rats treated with ortho-toluidine were mutagenic for S. typhimurium with metabolic activation.

5.2 Human data

ortho-Toluidine has been produced commercially since 1880. Its use as an intermediate in the manufacture of dyes and other chemicals as well as its occurrence as an impurity in some formulated corrosion inhibitors could result in occupational exposure.

The epidemiological studies available to the Working Group dealt only with workers who had been exposed to ortho-toluidine in combination with other chemicals. The majority were case reports and did not provide estimates of the population at risk. In one follow-up study, five cases of bladder cancer (0.08 expected) occurred in 53 men exposed to ortho-toluidine and to other possibly carcinogenic agents in the manufacture of Fuchsine and Safranine T.

5.3 Evaluation

There is sufficient evidence for the carcinogenicity of ortho-toluidine hydrochloride in experimental animals.

An increased incidence of bladder cancer has been observed in workers exposed to ortho-toluidine, but as all were exposed to other possibly carcinogenic chemicals, ortho-toluidine cannot be identified specifically as the responsible agent.

ortho-Toluidine should be regarded, for practical purposes, as if it presented a carcinogenic risk to humans.

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluation: Vol. 16 (1974)

Subsequent evaluation: Suppl. 7 (1987); Vol. 77 (2000)

Synonyms for ortho-Toluidine

Synonyms for ortho-Toluidine hydrochloride

Last updated: 8 April 1998

    See Also:
       Toxicological Abbreviations