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

(Group 2B)

For definition of Groups, see Preamble Evaluation.

VOL.: 60 (1994) (p. 347)
CAS No.: 100-40-3
Chem. Abstr. Name: 4-Ethenylcyclohexene

5. Summary of Data Reported and Evaluation

5.1 Exposure data

4-Vinylcyclohexene is produced by catalytic dimerization of 1,3-butadiene. 4-Vinylcyclohexene has been used as a chemical intermediate for production of flame retardants, flavours and fragrances, in the manufacture of polyolefins, as a solvent and in the manufacture of its diepoxide. Low levels of occupational exposure have been measured during the production and use of 1,3-butadiene.

5.2 Human carcinogenicity data

No data were available to the Working Group.

5.3 Animal carcinogenicity data

4-Vinylcyclohexene was tested for carcinogenicity in one experiment in mice and in one experiment in rats by gastric intubation and in two skin application studies in mice. Administration of 4-vinylcyclohexene by gastric intubation produced granulosa-cell and mixed tumours of the ovary and adrenal subcapsular tumours in female mice. In male mice, there was an increase in the incidence of lymphoma and of lung tumours. Following gastric intubation in rats, increased incidences of squamous-cell tumours of the skin in males and of clitoral gland tumours in females were observed. The studies by skin application were inadequate for evaluation.

5.4 Other relevant data

4-Vinylcyclohexene is distributed mainly to adipose tissue in rodents. The ethylene carbons are eliminated mainly in urine and expired air. Metabolism primarily involves oxidation to 4-vinylcyclohexane-1,2-epoxide, which is formed 13 times faster by liver microsomes from mice and twice as fast by those from rats than by human microsomes. 4-Vinyl-1,2-epoxycyclohexane, 4-epoxyethylcyclohexene and, particularly, the diepoxide are more toxic to mouse oocytes than 4-vinylcyclohexene itself. Treatment with 4-vinylcyclo-hexene decreased the number of oocytes in mice but not in rats. The difference seemed to be due to the reduced ability of the rat to metabolize 4-vinylcyclohexene to epoxides.

No data were available on the genetic and related effects of 4-vinylcyclohexene in humans.

4-Vinylcyclohexene and its mono-epoxide metabolites were not mutagenic to Salmonella typhimurium. 4-Vinyl-1,2-epoxycyclohexane induced micronuclei but not hprt mutations in cultured Chinese hamster cells.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of 4-vinylcyclohexene.

There is sufficient evidence in experimental animals for the carcinogenicity of 4-vinyl-


Overall evaluation

4-Vinylcyclohexene is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluation: Suppl. 7 (1987) (p. 73)


Last updated 08/26/1997

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       Toxicological Abbreviations