Long-term temporal changes in the estrogenic composition of treated sewage effluent 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 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 lover 8 months), from between 36 and 308 ng/L and between <0.2 (detection limit) and 10.7 mu g/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.