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

(Group 2B)

VOL.: 79 (2001) (p. 569)

CAS No.: 8001-35-2
Chem. Abstr. Name: Toxaphene

5.  Summary of Data Reported and Evaluation

For definition of Groups, see Preamble Evaluation.

5.1 Exposure data

Toxaphene is a complex mixture of chlorinated hydrocarbons produced by the chlorination of camphene. Toxaphene was widely used from the late 1940s as an insecticide on crops and to control parasites on livestock. The use of toxaphene is presently banned or restricted in many countries. Occupational exposure to toxaphene has occurred during its production and application. Human exposure to toxaphene is still possible owing to its persistence in the environment and its consequent continuing occurrence in fish, milk and other foodstuffs. In those countries in which its use has been banned, dietary intake has probably decreased in recent years.

5.2 Human carcinogenicity data

One case–control study of non-Hodgkin lymphoma and one of leukaemia not otherwise specified in the same populations showed no significant increase in risk associated with exposure to toxaphene.

5.3 Animal carcinogenicity data

Toxaphene has been tested for carcinogenicity by oral administration in one study in mice and one study in rats. It increased the incidence of hepatocellular adenomas and carcinomas combined in male and female mice. In rats, it produced thyroid follicular-cell adenomas and carcinomas in both males and females and pituitary adenomas in females.

5.4 Other relevant data

Toxaphene is lipid-soluble and accumulates in animals. It is metabolized by dechlorination and excreted into the bile. Toxaphene is a well-known microsomal enzyme inducer that increases phase I and II drug-metabolizing enzymes, consistent with a phenobarbital-like effect. It also increases the size of the thyroid gland and thyroid-stimulating hormone concentrations.

Toxaphene produced hepatotoxicity and immunotoxicity in experimental animals.

No reproductive or developmental effects were seen in three multigeneration studies in rats.

An increased frequency of chromosomal aberrations was observed in the lymphocytes of workers exposed to toxaphene in one study. In mammalian cells in vivo, toxaphene did not bind to DNA or produce dominant lethal mutations. In vitro, toxaphene was mutagenic to bacteria but did not induce mutations in mammalian cells. It induced micronuclei in the only assay for this end-point performed in mammalian cells. It also induced sister chromatid exchange and inhibited gap-junctional intercellular communication in cultured mammalian cells.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of toxaphene.

There is sufficient evidence in experimental animals for the carcinogenicity of toxaphene.

Overall evaluation

Toxaphene is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 20 (1979) (p. 327); Suppl. 7 (1987) (p. 72)


Last updated: 25 September 2001

    See Also:
       Toxicological Abbreviations
       Toxaphene (FAO/PL:1968/M/9/1)