INTRODUCTION carried out to determine the deleterious effects

INTRODUCTION

The immense number of pharmaceutical chemicals discharged into the environment in recent times have been found to mimic estrogen, the natural female hormone, through communication with the estrogen receptor found in mammals and other vertebrates (Pascoe, Carroll, Karntanut, & Watts, 2002). In the marine environment, estrogenic chemicals have been associated with irregular endocrine function in wild fish populations, resulting in feminization and altered gonadal development (Sumpter & Jobling, 1995).

According to Kidd et al., (2007), fish inhabiting aquatic environment receiving untreated or treated effluents from municipal wastewater treatment plants (MWTPs) are exposed to estrogenic compounds that alter their reproductive endocrine function. Research by Harris et al., (1997) illustrated that estrogen exposure of male fish downstream of wastewater outfalls resulted in the production of vitellogenin (VTG), which is associated with oocyte maturation in females and the formation of eggs in the testes of exposed males. This feminization has been linked to the presence of estrogenic substances, most especially 17?-ethinylestradiol (EE2) (Desbrow, Routledge, Sumpter, & Waldock, 1998). In multiple locations throughout the world, endocrine disrupting chemicals (EDCs) have been detected in surface waters near sewage treatment plants at concentrations ranging from 0.5 to 5.0 ng/L (Johnson, Befroid, & Corcia, 2000).

Though many studies have been carried out to determine the deleterious effects of estrogen compounds on aquatic organisms in the United States of America, little is known about the monitoring and the risk assessment of estrogen compounds in rivers around San Antonio, particularly those receiving treated wastewater effluent. The determination of existing estrogen levels in the Medina River, and Cibolo Creek, where treated wastewater is discharged, and San Marcos Spring, which does not receive treated wastewater will provide information on which, if any, estrogen compounds are present, and their concentrations. The objectives of this study are to: 1) determine the presence of estrogen compounds in San Marcos Spring, Medina River, and Cibolo Creek; and 2) determine the travel distance of the estrogen compounds above the detection limit from the point of discharge.

The presence of estrogen in these surface water receiving treated effluent will provide information on the current concentrations in relation to flow distance from the point of discharge, and potential health impacts.

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