Oestrogenic effects in fish in English rivers with evidence of their causation

In the mid-1980s, effluents from sewage-treatment works discharging into rivers in England and Wales were found to be oestrogenic, due to their ability to induce the production of a female specific egg-yolk protein precursor, vitellogenin (VTG), in male fish. Subsequent field studies, in which caged rainbow trout (Oncorhynchus mykiss) were placed at varying distances downstream of STW effluent discharges, demonstrated that the oestrogenic activity persisted in some receiving waters for considerable distances (up to 5 km) downstream from the point of sewage effluent input. More recently, populations of wild fish inhabiting English rivers have been shown to be intersex (a manifestation of endocrine disruption which can be induced by exposure to oestrogen). In these fish, a direct association between the incidence (and degree) of intersexuality, and the level of exposure to sewage-treatment effluent, has been demonstrated. Chemical analysis of STW effluents has identified natural steroidal oestrogens (namely, oestradiol-17 beta and oestrone), and in some cases the synthetic oestrogen, 17 alpha-ethynyloestradiol, at concentrations sufficient to induce the oestrogenic responses observed in the caged trout studies. In STWs receiving influent from wool scouring mills, alkylphenolic chemicals (biodegradation products of alkylphenol polyethoxylates; APEOs) were found to be the major oestrogenic contaminants and they were present at concentrations high enough to induce feminising effects in fish (VTG induction and suppression of testis growth in males). This chapter documents the major findings on the research into the oestrogenic effects in fish in English rivers, and critically assesses the weight of evidence (from both field studies and in vivo laboratory studies) that support the contention that exposure to steroidal oestrogens and alkylphenolic chemicals may be responsible for the impairment of reproductive function in wild fish.