Sewage treatment works (STW) effluents throughout the U.K. have been shown to be estrogenic, inducing vitellogenin (VTG) synthesis in caged and wild fish for considerable distances (up to several kilometers) downstream of the effluent discharge. Thresholds for vitellogenin induction in caged fish in those studies have been derived from shortterm exposures, and may not necessarily be representative of thresholds for estrogenic responses in wild fish living in rivers that contain STW effluent. In addition, very little is known about the long-term fluctuations in the concentrations of the estrogenic components of STW effluents. In this paper, it was established that the concentrations of natural steroid estrogens and xenoestrogens (alkylphenolic chemicals) in a treated sewage effluent fluctuated temporally (over 8 months), from between 36 and 308 ng/L and between <0.2 (detection limit) and 10.7 µg/L, respectively. Long-term exposure of maturing adult roach to a graded concentration of this effluent (0, 9.4, 17.5, 37.9, and 100% v/v) demonstrated that the vitellogenic response was both dose and time dependent. After 1 month exposure, the response threshold was 37.9 ( 2.3% treated sewage effluent, whereas after 4 months exposure, a significant induction of VTG occurred at an effluent concentration of 9.4 ( 0.9%. The data presented suggests that estrogenic responses in wild fish living in U.K. rivers cannot necessarily be predicted from short-term exposures using caged fish. The functional significance and/or ecological consequences of induction of vitellogenin resulting from exposure to STW effluent has yet to be determined in wild fish.
Wild roach (Rutilus rutilus) have been found with intersex gonads in rivers throughout the United Kingdom. The incidence of intersexuality is strongly correlated with discharges of estrogenic treated sewage effluent into those rivers, and this has led to the hypothesis that estrogenic chemicals in effluents are feminizing wild male fish. In this study, early-life stage roach (50 days post hatch, dph) were exposed for 150 days to a graded concentration (0%, 12.5%, 25%, 50%, and 100%) of treated sewage (primarily domestic) effluent to examine the effects of exposure on sexual differentiation and development. Measurement of steroid estrogens and alkylphenolic chemicals in the effluent and a resulting dose-dependent induction of vitellogenin (VTG; a female-specific, estrogen-dependent plasma protein) confirmed that the fish had been exposed and responded to "estrogen" in the effluent. Exposure to treated sewage effluent induced feminization of the reproductive ducts in "male" roach in a dose-dependent manner (in full-strength effluent, 100% of the fish had feminized ducts), indicating that the disruption of the gonad ducts seen in wild roach is the result of exposure to treated sewage effluents during early-life stages. There were no effects of treated sewage effluent exposure on germ cell development; therefore, no oocytes occurred in the testes of the feminized male roach. Subsequent, depuration of the effluent exposed fish in "clean" water for 150 days resulted in a reduction in plasma VTG but no alteration of the feminized ducts, indicating that the effect of the treated sewage effluent on reproductive duct development was permanent. The causality of oocytes in the testes of wild male roach therefore remains to be elucidated.
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