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

(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 53 (1991) (p. 403)

CAS No.: 137-26-8
Chem. Abstr. Name: Tetramethylthioperoxydicarbonic diamide

5. Summary of Data Reported and Evaluation

5.1 Exposure data

The major use of thiram is as an accelerator and vulcanization agent in the rubber industry. It is also used as a fungicide on seeds and as a foliar fungicide on turf, fruit and vegetables. It has been in commercial use since 1925.

Thiram has been formulated for use as dusts, wettable powders and flowable suspensions and also in combination with other pesticides.

Exposure may occur during its production, its use in the rubber industry and its application as a fungicide, and, at much lower levels, from consumption of foods containing residues. Thiram is also an environmental degradation product of the two fungicides, ferbam and ziram.

5.2 Carcinogenicity in humans

No adequate data were available to the Working Group.

5.3 Carcinogenicity in experimental animals

Thiram was tested adequately for carcinogenicity by oral administration in one study in rats. No increase in incidence was seen for tumours at any site.

When thiram was administered orally to rats in combination with nitrite, a high incidence of tumours of the nasal cavity was observed in males and females.

5.4 Other relevant data

Thyroid abnormalities were observed in a group of subjects exposed occupationally to thiram.

Thiram marginally increased the frequency of enzyme-positive foci in rat liver. It decreased fertility in rats and caused embryolethality and embryotoxicity in rats and hamsters and malformations in mice and hamsters.

No data were available on the genetic and related effects of thiram in humans.

Thiram induced various kinds of chromosomal damage and altered sperm morphology in rodents in vivo. It induced unscheduled DNA synthesis and sister chromatid exchange in cultured human cells. It was genotoxic to insects, plants, fungi and bacteria.

5.5 Evaluation

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

There is inadequate evidence in experimental animals for the carcinogenicity of thiram.

Overall evaluation

Thiram is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 12 (1976) (p. 225); Suppl. 7 (1987) (p. 72)


Last updated: 21 November 1997

    See Also:
       Toxicological Abbreviations
       Thiram (ICSC)
       Thiram (FAO Meeting Report PL/1965/10/1)
       Thiram (FAO/PL:1967/M/11/1)
       Thiram (Pesticide residues in food: 1984 evaluations)
       Thiram (Pesticide residues in food: 1992 evaluations Part II Toxicology)