CARCINOGENIC AND CO-CARCINOGENIC STUDIES OF THIRAM ON MOUSE SKIN

Thiram (tetramethyl thiuram disulfide), a carbamate fungicide, is used in the rubber processing industry as an accelerator and vulcanizing a gent. Previous studies evaluated the tumorigenic potential of thiram i n rodents, but failed to provide conclusive results. In the present st udy the tumorigenic potential of thiram was evaluated in Swiss albino mice by a two-stage initiation-promotion protocol and a long-term in v ivo bioassay for carcinogenicity. Results revealed that following tumo ur initiation with thiram and promotion with 12-O-tetradecanoyl phorbo l 13-acetate, skin tumours developed, mostly at the site of treatment (dorsal skin) in single and multiple dose-initiated animals. Similarly , papillomatous growths were observed on the dorsal skin of the mice i nitiated with a single subcarcinogenic dose of dimethylbenzanthracene and promoted with thiram. Thiram failed to provoke tumorigenesis when tested as a complete carcinogen for up to 52 wk and thereafter the stu dy was terminated due to increased mortality. It is concluded that thi ram has both tumour initiating and tumour-promoting potential in both sexes of Swiss albino mice following topical exposure at the tested do se level.