Long-term temporal changes in the estrogenic composition of treated sewageeffluent and its biological effects on fish

Sewage treatment works (STW) effluents throughout the U.K. have been shown to be estrogenic, inducing vitellogenin (VTG) synthesis in caged and wild f ish 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 nece ssarily be representative of thresholds for estrogenic responses in wild fi sh living in rivers that contain STW effluent. In addition, very little is known about the long-term fluctuations in the concentrations of the estroge nic components of STW effluents. In this paper, it was established that the concentrations of natural steroid estrogens and xenoestrogens (alkylphenol ic chemicals)in a treated sewage effluent fluctuated temporally lover 8 mon ths), from between 36 and 308 ng/L and between <0.2 (detection limit) and 1 0.7 mu g/L, respectively. Long-term exposure of maturing adult roach to a g raded concentration of this effluent (0, 9.4, 17.5, 37.9, and 100% v/v) dem onstrated that the vitellogenic response was both dose and time dependent. After 1 month exposure, the response threshold was 37.9 +/- 2.3% treated se wage effluent, whereas after 4 months exposure, a significant induction of VTG occurred at an effluent concentration of 9.4 +/- 0.9%. The data present ed suggests that estrogenic responses in wild fish living in U.K, rivers ca nnot necessarily be predicted from short-term exposures using caged fish. T he functional significance and/or ecological consequences of induction of v itellogenin resulting from exposure to STW effluent has yet to be determine d in wild fish.