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Similar effects for the substances causing

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Unformatted text preview: ge treatment plant discharges (Sumpter and Jobling 1995), where the human derived hormones estrone and 17β -estradiol appear to be the causative agents ( Matthiessen et al. 1996). What the implications of these responses are at the population level is uncertain but, from current observations, the effects have not caused gross perturbations of populations or communities and may be subtle enough that they are of minor consequence 3.3.5.3 WILDLIFE AS SENTINELS FOR HUMANS It has been suggested that wildlife organisms can be sentinels of effects in other organisms, such as humans. It is true that some species o f wildlife are uniquely positioned to act in this role. This is particularly so in the case of the organisms at the top of the food chain where they can be exposed to much greater concentrations of persistent and bioaccumulative substances. This also applies to organisms, such as fish, that occupy environments that allow continuous exposure to endocrine modulating substances. These situations are unique with respect to most other organisms because of the large exposures that result. Given that many of t he wildlife species that were previously affected by persistent and bioaccumulative substances are showing recovery, the question of the relevance of this to humans needs to be critically assessed. While humans have longer reproductive cycles than most wi ldlife, by analogy, they would be expected to show slower recovery, if they were affected in the first place. However, because of their position on the food chain, most humans are also not subjected to the large exposures that wildlife are now seen to be r ecovering from. Human health risk assessment endpoints are different from those used in the ecosystem but there is little reason to believe that humans have experienced anywhere close to the level of responses seen in wildlife. With the exception of responses to exceptionally large doses of endocrine modulating drugs, epidemiological studies in humans have failed to show consistent evidence of adverse effects that can be ascribed to environmental exposures to endocrine modulating substances. The recovery of wildlife populations, coupled with the lack of identifiable effects of endocrine modulating substances in humans, strongly suggests that future risks from environmental exposures to endocrine modulating substances will decrease to even smaller concentrati ons than humans are currently exposed to. There is considerable scientific research focus on endocrine modulating substances at this time. In our haste to address some of these new problems there is a real risk that we will direct our limited resources t oward solving non-problems. Responses observed in wildlife should direct us away from persistent bioaccumulative substances as these are, in most instances, already addressed through national and international regulations. Regulatory actions in the Great Lakes have resulted in recovery of wildlife populations and similar responses will occur elsewhere when equivalent regula...
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