The active synthetic constituent of oral contraceptives 17α- ethinylestradiol (EE2)
and its natural steroidal estrogen analogues are being released into the aquatic
environment mainly via wastewater treatment plants (WWTPs). Although steroidal
estrogens have been frequently reported in very low concentrations in the environment,
they have been placed at the top of the list of endocrine disrupting chemicals (EDCs) for
their high estrogenic activity in non-target aquatic species like fish and frogs. Almost 30
years worth of intensive research has moved the problem of endocrine disruption in the
aquatic environment from being a hypothesis to a well-known cause-and-effect story.
However, the fate and effects of many pharmaceuticals, including EE2, remain poorly
understood. Thus, the main objective of this thesis was to investigate EE2
bioaccumulation in fish by field and laboratory studies.
An optimized sample preparation and analytical method protocol was achieved to
detect EE2 in its biologically active form in whole fish tissue at trace levels (ng/g).
Shorthead redhorse suckers (ShRHS) (Moxostoma macrolepidotum) collected in
proximity to a WWTP in the St. Clair River have significantly accumulated EE2 with an
average of 1.5 ng/g. EE2 bioaccumulation was limited to fish exhibiting intersex and with
induced vitellogenin (VTG). EE2 was absent in fish from a reference site. Positive
correlations between EE2 and lipid content as well as "15N supported the hypothesis of
EE2 bioaccumulation in wild ShRHSs. A wider survey was carried out to explore
patterns of EE2 bioaccumulation in the pelagic and benthic food-wed of the St. Clair
IV
River, Ontario. In the WWTP effluents and nearby surface waters, EE2 levels were
extremely low and below our method detection limits. All of the seven sampled species
from different trophic levels and the sediment samples collected from the impacted sites
and the reference sites did not have any measurable EE2 concentrations. A laboratory
controlled study where male goldfish (Carassius auratus) were exposed to EE2 via water
versus food demonstrated that fish can rapidly accumulate EE2 by both routes of
exposure. The uptake constant for water was 45 h-1 and the bioconcentration factor for
EE2 in fish was 377. The fast uptake rate of EE2 via water coincided with a much slower
elimination rate constant of 0.0786 h-1. The assimilation efficiency of 0.106 for EE2 by
goldfish was determined by EE2 dietary exposure, which was used to predict EE2
accumulation under different exposure scenarios. The work presented here was the first
demonstration of EE2 bioaccumulation in wild fish and the first to model EE2
bioaccumulation from water and dietary exposure in laboratory-exposed fish.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OOU./en#10393/22684 |
| Date | 04 April 2012 |
| Creators | Al-Ansari, Ahmed |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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