Transformation of a non-oestrogenic steroid metabolite to an oestrogenically active substance by minimal bacterial activity

The majority of oestrogenic material excreted from humans and wildlife, and therefore released into sewers, is in a conjugated form. However, the find ing of "free" oestrogens in sewage effluent suggests that these metabolites are somehow converted back into an active form, before or during passage t hrough a sewage treatment process. When male fathead minnows (Pimephales pr omelas) were continuously exposed to oestradiol-3-glucuronide, in a continu ous-flow system, it demonstrated no inherent oestrogenic activity. However, when fish were exposed to effluent generated from laboratory simulations o f sewage treatment processes, to which had been added oestradiol-3-glucuron ide, oestrogenic activity was observed, suggesting microbial activity was c apable of degrading the steroid metabolite into a more potent oestrogen. Oe strogenic potency was determined by measuring changes in plasma vitellogeni n (egg yolk precursor) concentrations and gonadosomatic index. The results suggest that inactive metabolites of steroids are very readily biotransform ed into biologically active oestrogens. (C) 1999 Elsevier Science Ltd. All rights reserved.