| Summary: | 碩士 === 嘉南藥理科技大學 === 環境工程與科學系碩士班 === 92 === 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.
|
|---|
