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Interdisciplinary approaches to endocrine disruption : effects of dietary exposure of 4-nonylphenol on smoltification of juvenile coho salmon (oncorhynchus kisutch) and how risk effects are perceived

University of British Columbia

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.

Thesis/Dissertation

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2009-08-12

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http://hdl.handle.net/2429/12114

Resource Management and Environmental Studies

University of British Columbia

UBCV

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