Recently, the scientific community has been concerned about the potential of exposing
organisms to natural estrogens and xenobiotic compounds that can interfere with normal
endocrine functions in these organisms. Indeed, over the past decade, it has been recognized that
there is a need to conduct more research that involves studying the effects of exposure of
organisms to endocrine disrupting compounds in order to understand their implications for
human and ecosystem health. Accordingly, the objective of this thesis was to contribute to our
knowledge of this societal concern.
This thesis approaches the endocrine disruption hypothesis from two streams of knowledge. The
first half of the thesis describes the results of a controlled experiment to investigate the effect of
dietary exposure of juvenile coho salmon (Oncorhynchus kisutch) to 4-nonylphenol with respect
to their ability to complete smoltification and grow well during early marine residency. I
hypothesized that dietary exposure of juvenile coho salmon to 4-nonylphenol during the
freshwater phase immediately prior to parr-smolt transformation would adversely affect their
subsequent growth, survival and growth performance upon transfer to seawater. A randomized
block experiment using duplicate groups of coho salmon exposed to four broad range dietary
concentrations of 4-nonylphenol, one positive estrogen control and one negative control was
conducted to test this hypothesis. The results of the experiment did not support the hypothesis
under these particular experimental conditions. However, important information regarding the
degree of ubiquitous contamination of 4-nonylphenol was gained. Chemical analyses
determined the presence of 4-nonylphenol in significant concentrations in the marine oil that was
incorporated in the diets and in the commercially prepared krill coating that was used to make
the diets more palatable. Therefore, relative responses of the fish to the diet treatments are only
possible since there was no negative control diet without 4-nonylphenol. Subtle differences in
retention of parr marks after seawater transfer were observed between fish given the treatments
although no chemical analyses were performed to substantiate these observations.
The second half of the thesis was concerned with the examination of the nature of the perceived
risk posed by endocrine disrupting compounds from a social scientific perspective. Using a
conceptual framework built around the condition of "risk society", some key issues involving
risk communication and the perception of the risk are described. To apply qualitative research
methods to investigate the perception of endocrine disrupting compounds as a risk to human and
ecosystem health, a questionnaire was designed to examine public awareness of the EDC issue. I
hypothesized that physicians would represent "intermediary experts" whose scientific
background and familiarity with the concerns of the public at large would give an indication of
public perception of risk that exposure to EDCs would pose to human or ecosystem health. The
response to the survey that was provided to the physicians was extremely poor within the six-week
period of study and the questionnaire provided no significant new knowledge upon which
informed decisions could be made for constructing a future comprehensive survey.
The thesis concludes with a discussion of the integration of the two pathways to examine the
endocrine disruption hypothesis. Some specific recommendations for further research are
proposed in the context of integrated approaches to assessing the effects and perception of risk of
exposure to endocrine disrupting compounds.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/12114 |
| Date | 05 1900 |
| Creators | Keen, Patricia Lynn |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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