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 an irregular endocrine function in wild
fish populations, resulting in feminization and altered gonadal development
(Sumpter & Jobling,
1995).

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According to Kidd et al.,
(2007), fish inhabiting aquatic environment receiving untreated or treated
effluents from public wastewater treatment plants (WWTPs) 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 responsible for oocyte maturation in females and the development 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.