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

HEXACHLOROCYCLOHEXANE
(TECHNICAL HCH AND LINDANE)

VOL.: 20 (1979) (p. 195)

5. Summary of Data Reported and Evaluation

5.1 Experimental data

a-HCH was tested in several experiments in mice by oral administration: it produced benign and malignant liver tumours in animals of both sexes; a treatment of 16 weeks was sufficient to produce tumours. Two feeding experiments in rats, one of which suggested a carcinogenic effect on the liver, were considered to be inadequate.

b-HCH was tested in four experiments in mice by oral administration: two were inadequate, and another was inadequately reported but suggested hepatocarcinogenicity; in the fourth study, b-HCH induced benign and malignant liver tumours in animals of both sexes. Two feeding experiments in rats were considered to be inadequate.

Lindane was tested in six experiments in mice by oral administration: it produced benign and malignant liver tumours in animals of both sexes in two experiments, one of which involved only small groups of animals. The results of a third experiment suggested hepatocarcinogenicity but were inadequately reported. The results of a fourth experiment also suggested hepatocarcinogenicity but were considered inadequate because of the low number of control animals used. The other experiments were considered inadequate for an evaluation of carcinogenicity. Lindane was also tested in three feeding studies in rats: two were considered inadequate; in the other a slight excess of thyroid tumours was observed in females. Lindane was tested inadequately in mice by skin application and by subcutaneous and intraperitoneal administration.

Experimental data on the long-term effects of the d- and e-isomers were considered to be inadequate.

Technical HCH was tested in three experiments in mice by oral administration, producing liver tumours. A feeding experiment in rats was considered to be inadequate.

Lindane is embryotoxic. a- and b-HCH and lindane, when tested individually and/or as a mixture, were not mutagenic in bacteria, yeast or Drosophila. Lindane induces chromosome aberrations, polyploidy and mitotic arrest in a number of plant systems. It also induced chromatid breaks in human lymphocytes in vitro.

5.2 Human data

Several case reports indicate a relationship between exposure to HCH or lindane and the occurrence of aplastic anaemia. Two cases of acute myeloid-type leukaemia in cousins exposed to lindane and one case of acute myelomonocytic leukaemia, secondary to aplastic anaemia, that was associated with dermal exposure to a lindane/toxaphene mixture have also been reported.

The only epidemiological study related to possible carcinogenic effects of HCH or lindane in humans involved exposure to many pesticides; the Working Group was thus unable to draw any conclusion specific to HCH or lindane.

The extensive production of HCH and lindane and their use in veterinary, agricultural and consumer products since the early 1950s indicate that widespread human exposure occurs. This is confirmed by many reports of their occurrence in the general environment and by reports of their presence in body fluids and tissues, both in the general population and in exposed workers.

5.3 Evaluation

There is sufficient evidence that a-HCH, lindane and technical HCH are carcinogenic in mice; there is limited evidence that b-HCH is carcinogenic in mice.

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluation: Vol. 5 (1974)

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 31 March 1998 






























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