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

(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 73 (1999) (p. 329)

Chem. Abstr. Reg. No.: 108-78-1
Chem. Abstr. Name: 1,3,5-Triazine-2,4,6-triamine

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Exposure to melamine may occur during its production and use in the manufacture of synthetic resins with formaldehyde.

5.2 Human carcinogenicity data

No data were available to the Working Group.

5.3 Animal carcinogenicity data

Melamine has been studied for carcinogenicity in mice and rats of each sex by oral administration. It produced urinary bladder and ureteral carcinomas in male rats but only urinary bladder hyperplasia in male mice. The occurrence of urinary bladder tumours in male rats correlated strictly with calculus formation and exposure to high doses. The dose dependence was confirmed by subsequent studies in male rats in which concomitant administration of sodium chloride to increase urinary output resulted in a decreased tumour yield.

5.4 Other relevant data

There is no evidence that melamine undergoes biotransformation. The urinary bladder tumours seen in male rats exposed to high doses of melamine appear to be produced by a non-DNA-reactive mechanism involving epithelial hyperplasia secondary to the presence of melamine-containing bladder stones. Consequently, bladder tumours would not be expected in either rodents or humans except at doses that produce bladder calculi.

No data were available on the reproductive or developmental toxicity of melamine.

No data were available on the genetic and related effects of melamine in humans. It was not genotoxic in experimental systems.

5.5 Evaluation

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

There is sufficient evidence in experimental animals for the carcinogenicity of melamine under conditions in which it produces bladder calculi.

Overall evaluation

In making its overall evaluation, the Working Group noted that the non-DNA-reactive mechanism by which melamine produced urinary bladder tumours in male rats occurred only under conditions in which calculi were produced.

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

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 39 (1986); Suppl. 7 (1987) (p. 65)


Last updated: 30 September 1999

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       Toxicological Abbreviations