SHORT COMMUNICATION Tumour-promoting ability of mancozeb, a carbamate fungicide, on mouse skin

'To whom correspondence should be addressed In this study the tumour-promoting activity of a carbamate fungicide, mancozeb, has been observed following topical application on mouse skin in a two-stage initiation—promotion protocol for carcinogenesis. Female Swiss albino mice were initiated with a single subcarcinogenic dose (52 /tg) of 7,12-dimethylbenz[a]anthracene painted on the interscapular region. Seven days after initiation the mice underwent topical application of mancozeb (100 mg/kg body wt) three times per week as promoter. Development of tumours was observed after 12 weeks of mancozeb application in 1/14 animals and 100 % tumorigenesis was recorded after 17 weeks of mancozeb application. On histological examination, these tumours were found mostly to be benign in nature, e.g. squamous cell papillomas and keratocanthomas. Mancozeb is a protective fungicide and a polymeric complex of ethylene bis (dithiocarbamate) manganese with zinc salt. It is reported to be a skin irritant in rats after topical application (1) and considered by the International Agency for Research on Cancer (Lyon, France) as one of the high priority chemicals to be tested for its tumorigenic activity (2). In earlier studies mancozeb was found by our group to act as a tumour initiator and co-initiator on mouse skin in a two-stage protocol of study for its carcinogenic potential (3, N.K.Mehrotra, S.Kumar and Y.Shukla, unpublished results). In view of these reports and its increasing demand in India as a fungicide, mancozeb (technical grade, minimum purity 95%) has been tested by us and reported in the present study for its tumour-promoting ability in a two-stage initiation-promotion protocol on mouse skin (4). Mancozeb (technical grade) was obtained from Bharat Pulveriz