Metabolites of diethylstilboestrol induce sister chromatid exchange in human cultured fibroblasts

Diethylstilboesterol (DES) is one of the few substances for which a clear association with carcinogenicity has been established in man. Nevertheless, it is still widely used, mainly as a cheap oestrogen to increase the slaughter weight of beef, but in spite of this it is not known if residues in the meat or metabolites excreted by the cattle are hazardous to man. It is also unknown whether there is a threshold dose below which DES is harmless. A threshold might be expected if a hormonal mechanism of carcinogensis rather than metabolic activation to an electrophically reactive species operats. This possibility was supported by the observations that DES, in contrast to most other carcinogens,…