現代人每天在日常生活中接觸到的一些化學物質中，少數已被證實是具有類似於生物體內荷爾蒙之作用，此物質我們俗稱為環境荷爾蒙物質(environmental hormones, EHs)。其中包括一些殺蟲劑、多氯聯苯、戴奧辛以及作為食品包裝、油漆、化妝品等之原料化合物如烷基酚類、雙酚A。由於這些物質大多無法被傳統的污水處理設備所去除，所以釵h工業及都市污水處理廠放流水中皆可發現含有這些物質的存在。因此，污水處理廠放流水也是其排放至水環境中的重要污染源之一。本研究主要目的為探討污水處理廠放流水對本土吳郭魚(Tilapia spp.)的雌激素活性。我們將魚暴露於取自污水處理廠之放流水，並以連續流(continuous flow system , CFS)之方式暴露連續達21天，其暴露濃度為稀釋50%或全放流水。雌激素活性反應評估則以魚體血清中卵黃蛋白前質(vitellogenin, VTG)的濃度來判定。另外，我們並以生殖腺體重比(gonadsomatic index, GSI)及肝臟體重比(hepatosomatic index, HSI)指數觀察魚類個體是否同時出現生理之變化。本研究結果發現：雌魚暴露在稀釋50%以及100%放流水經7天後其VTG含量可被提升；而雄魚在冬季時，暴露於稀釋50%放流水的第7天後以及暴露於春季時，100%放流水的第14天後，開始有VTG的反應。無論是雌魚或雄魚，VTG誘導的濃度皆在21天後始達到最高量，且與控制組比較後有顯著的差異。在GSI及HSI方面，暴露時期為冬、春兩季之雌魚，其GSI皆有些微增加之現象，而與控制組比較後的雄魚GSI則有顯著減小之現象；另外，暴露於各濃度放流水之雌魚或雄魚的HSI都高於對照組。由上述研究可推論污水處理廠放流水中含有具雌激素活性的化學物質，而其濃度足以誘導魚體內VTG的提升以及生理組織之變化。 A large number of substances in daily use are known to mimic natural hormones in animals. These chemicals known as environmental hormones (EHs) or endocrine disrupting chemicals (EDCs) include some pesticides, PCBs, components of food packaging materials and certain alkylphenolic substances which arise from alkylphenol polyethoxylates (APEOs) commonly used in detergents, paints and cosmetics. Sewage treatment plants (STPs) received natural and synthetic EHs from urban and industrial discharge. These compounds can not be completely removed by treatment processes of STPs and can ultimately discharged be released into the aquatic environment. Therefore, effluent from STP is an important source of EHs. The purpose of this study was to examine the effects of effluent on an indigenous freshwater fish, tilapia (Tilapia spp.). Effluent samples were collected during winter and spring and test fish were raised in aquariums and exposed to either tap water (control), half strength (50% dilution) or whole effluent for 21 days. A flow rate of 5 mL/min was applied to a continuous flow system (CFS). Estrogenic responses were evaluated based on the expression of serum vitellogenin (VTG) using western blots and quantified by an imaging analysis system. In addition, we also measured gonadosomatic index (GSI) and hepatosomatic index (HSI) to observed physiological and reproductive effects of the fish. The results showed that a short-term exposure (7 days) of the effluent at both concentrations could increase VTG levels in female during winter and spring. Male tilapia exposed to effluent at concentration of 50% dilution after 7th day has a VTG induction during winter, but during spring, male exposed to the whole effluent only after the 14th day did VTG levels elevate. The VTG levels in both male and female fish were highest at the 21th day. At the 21th day, fish were sacrificed and GSI and HSI were measured. The GSI of female fish were slightly increased, while GSI of male fish were statistically significantly smaller than control. The HSI of both female and male fish were higher than control for both experiments, but not statistically different. This study indicates that estrogenic compounds are present in STP effluents which resulting VTG induction. Concentrations of these chemicals in STP effluent were high enough to be responsible for the VTG induction and physiological alteration observed in tilapia.
