Endocrine Abstracts

Detailed surveys of wild fish in English rivers have shown that endocrine disruption is a widespread phenomenon. Feminization of males is the effect most commonly observed. In one species of fish, the roach, 40% of the fish thought to be males show signs of endocrine disruption to varying degrees, with the evidence at different sites ranging from very low to 100%. The severity of endocrine disruption also varies, and ranges from fish with feminized reproductive ducts but no other obvious effect through to severely affected intersex fish in which the 'testes' contain large numbers of oocytes. The cause of this endocrine disruption is exposure of the fish to to oestrogenic chemicals entering rivers in effluents from sewage treatment works (STW). These oestrogenic chemicals are very variable in nature. Those primarily responsible for feminizing fish in English rivers appear to be the natural oestrogens 17beta-oestradiol and oestrone, and the synthetic oestrogen ethinyl oestradiol. The former originate primarily from the urine and faeces of women, and the latter from uses of the contraceptive pill. In a few specific locations xenoestrogens, rather than natural or synthetic steroidal oestrogens, appear to play a causative role in the endocrine disruption. In particular, nonylphenol, a degradation product of one group of surfactants, has been shown to be the major oestrogenic chemical in areas where textile mills are located. Finally, phytoestrogens may play a major role in some locations. Although this group of chemicals has not been considered as a cause of endocrine disruption in English rivers, it has been shown to be the major oestrogenic chemical in some STW effluents in Japan; these receive the phytoestrogens, such as genistein, in waste from the food industry. Probably the two biggest challenges now are to understand how these chemicals interact within mixtures, and what the long-term, population-level effects are of endocrine disruption.