Expert Views :: Endocrine Disrupters and Biodiversity: What Should the Public Be Told?
Brian R. Shmaefsky, Ph.D.

How the Public Gets Its Science
Notoriety in the scientific research community does not necessarily equate to fame in the public eye. The most brilliant research studies usually make it no further to public attention than being cited in magazines or Web sites read by few people. Much of what the public learns about science comes from the general media. Online and traditional news sources are the predominant filter and the promulgator of science information for most people. Movies are another vehicle of science information. Much of what they portray is easily debatable in its scientific accuracy and realism.

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Media and movie attention to scientific findings can be a mixed blessing. The dangers of nuclear war and nuclear power were glossed virtually hidden from the public. Movies such as Godzilla (Figure 1) and Them (Figure 2) surprisingly provided momentum for stringent radiation safety policies in American and Japan. The diminishing natural resources problems plaguing almost every area of the United States gained public attention through movies such as Frogs (Figure 3) and Soylent Green (Figure 4) As unrealistic as they were, this genre of movies helped forge a public environmental sentiment. Global climate change was nothing more than an academic issue until the release of The Day After Tomorrow (Figure 5). Many scientists derided the movie because of its erroneous portrayal of global climate change. Nevertheless, organizations such as the Union of Concerned Scientists used the movie to catapult their campaign to reduce global warming. They believe the benefits derived by the public attention to global warming far outweighed the misinformation presented in the film.

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Science taught in school appears to have less impact than movies on instilling science awareness in the public. There have been dozens of environmental science programs used in kindergarten through college classrooms since the 1970s. Yet, there is little evidence they promoted an environmental ethic in a majority of people. Current surveys conducted throughout the United States show that people have a shallow knowledge of environmental issues. Much of what they do know was recalled from media coverage. The strategy of ?teaching them while they are young? also seems ineffectual. The information is somehow lost as the children progress through their education. It is very likely that every student in an earth science class heard about tsunamis. However, their current knowledge of tsunamis was almost wholly due to the in-depth media coverage given to the unfortunate event that recently occurred in the Indian Ocean. Their schooling about tsunamis might have faded into a distant memory if it was not for this current catastrophe.

Endocrine Disrupters: A Pending Environmental Issue
The universal nature of many hormone receptors makes it possible for the hormones of one organism to affect the cells of an unrelated life form. Under normal conditions it is unlikely to find the hormones of one creature entering the bloodstream of another. If this does occur it is most likely to happen to heterotrophs or organisms that feed upon others. Animal, microbial, and plant hormones are usually acquired from a meal. However, protein hormones taken in through the diet are usually deactivated or degraded if not protected from the extreme pH changes and enzymatic activities of the digestive system. The lipid hormones, mostly comprised of the sterols, are found in such miniscule amounts that they usually have no significant effect when ingested.

There are situations in which dietary hormones do impact the unsuspecting consumer. Many plants produce large amounts of isoflavones. These phytoalexins (hormones that help defend plants against invaders) produced in legumes (beans and peas) and other members of the Fabaceae/Leguminosaeare family bind to the estrogen receptors of many organisms. They are for the most part targeted at insects that feed upon plants. It is believed that large herbivores such as antelope and deer are also intentional subjects of these plant compounds. Biochanin A, coumestrol, daidzein, formononetin, genistein, and glycitein are the most common isoflavones monitored in human foods. Soy beans are most noted for their high isoflavone content. Plants produce isoflavones primarily to reduce predation by herbivores. These compounds interrupt the reproductive capabilities of the target species. In effect they act as a birth control agent that keeps the herbivore population in check. Thus in turn reduces the chance of being eaten into extinction by a burgeoning population of herbivores. Isoflavones have other functions, too, such as attracting beneficial bacteria to the roots.

However, there are insidious ways for organisms to take in exogenous hormones. Agricultural, commercial, and household activities introduce endocrine disrupting pollutants into the environment. These endocrine disrupting hormones have a variety of effects on organisms. This is not only known from the rigorous in vitro experimental studies documented on the e.hormone Web site. There is ample evidence correlating the presence of endocrine disrupters in the environment to developmental and sexual abnormalities of wildlife living in the polluted environments. Tyrone Hayes for sure provides the most contemporary compelling research that endocrine disrupters such as atrazine can do severe environmental harm.

Endocrine disrupters like many pollutants do not have the drastic lethal effects that cause public alarm. They do not outright kill hoards of animals as attributed to many pesticides and industrial chemicals. Their effects are subacute meaning that it can take years before any environmental distress is noted. Plus, they have a differential effect. Alligators are impacted differently from birds. Different levels and durations of exposure produce dissimilar effects within the same species. So, it is difficult to pinpoint the outcomes of an endocrine disruptor pollution event. It is easy to convince a person that endocrine disrupters will affect an organism and an environment; however, it is not easy to predict the long-term environmental ramifications.

Endocrine Disrupters and Biodiversity
Biodiversity is one term that mysteriously appeared in the scientific jargon. It was commonly used before a distinct definition was universally accepted. Probably the most comprehensive and consistent rendering of the meaning of biodiversity was developed by the US Environmental Protection Agency. They define biodiversity as:

The variety and variability among living organisms and the ecosystems in which they occur. Biodiversity includes the number of different items and their relative frequencies; these items are organized at many levels, ranging from complete ecosystems to the biochemical structures that are the molecular basis of heredity. Thus, biodiversity encompasses expressions of the relative abundances of different ecosystems, species, and genes.
This definition is an amalgamation of many uses of the term; basically, it keeps everybody happy. Biodiversity is regularly represented as a statistical value called the biodiversity index. It is used as a measure of environmental quality.

It should be somewhat obvious that endocrine disrupters would have negative impacts on biodiversity. The inability for animals and plants to breed surely interferes with the intraspecific and interspecific interactions needed to maintain the biodiversity of an environment. However, it is difficult "proving" that the problem is a real one. Again, the damage caused by endocrine disrupters is not acute. It is a slow process that is not readily measurable in a short-term experiment. So, it is a hard sell very much like the global climate change issue. Groups like the World Wildlife Fund are petitioning various governments to reduce endocrine disruptor pollution before any biodiversity damage does occur. The problem is that they cannot point to a pond or forest and vehemently declare that endocrine disrupters created biodiversity decay in that environment. They can state that certain amphibians and fish have reduced abilities to produce offspring. But, they cannot blame the downfall of biodiversity on these individual events.

Making a Public Sentiment
The sciences of biodiversity and endocrine disrupters are still a mystery to most of the public. This is obviously not due to a dearth of scientific research on the topics. Nor is it due to a lack of magazine articles and Web sites about these topics A wealth of evidence laid out in a "matter of fact" approach does not sell scientific issues to the public. This is true even if the information is presented in exacting classroom sessions. The anonymity of biodiversity and endocrine disrupters is very likely due to the lack of melodramatic media coverage. But, the scientists knowing the dangers of endocrine disrupters on biodiversity are hesitant about taking an advocacy stand. They are rightfully afraid of diminishing the credibility of their research by sensationalizing their data. Plus, some of the organizations promulgating this issue are seen as "too extreme" by much of the public. These groups predominantly "preach to the choir." Maybe there needs to be a hit movie about the potential dangers of unchecked endocrine disruptor pollution. After all, movies seem to have a greater impact on public sentiment than sound scientific evidence (Figure 6). Really, there needs to be some "emotional selling" by credible researchers. Edward O. Wilson is doing this with biodiversity. Where is the public spokesperson for environmental endocrine disrupters?

  1. Andersen ME, Conolly RB, Faustman EM, Kavlock RJ, Portier CJ, Sheehan DM, et al. 1999. Quantitative mechanistically based dose-response modeling with endocrine-active compounds. Environ Health Perspect 107(Suppl 4):631-638.
  2. Bergeron JM, Crews D, McLachlan JA. 1994. PCBs as environmental estrogens: Turtle sex determination as a biomarker of environmental contamination. Environ Health Perspect 102:780-781.
  3. Bladergroen MR, Spaink HP. 1998. Genes and signal molecules involved in the rhizobia-leguminoseae symbiosis. Curr Opin Plant Biol 1:353-359.
  4. Cheek AO, Vonier PM, Oberdorster E, Colins Burow B, McLachlan JA. 1998. Environmental signaling: A biological context for endocrine disruption. Environ Health Perspect 106(Suppl 1):5-10.
  5. Colborn T and Clement C., eds. 1992. Chemically-Induced Alterations in Sexual and Functional Development: The Wildlife Connection. Princeton Scientific Publishing: New Jersey.
  6. Daniel O, Meier MS, Schlatter J, Frischknecht P. 1999. Selected phenolic compounds in cultivated plants: Ecologic functions, health implications, and modulation by pesticides. Environ Health Perspect 107(Suppl 1):109-114.
  7. Freemark K and Boutin C. 1995. Impacts of agricultural herbicide use on terrestrial wildlife in temperate landscapes: A review with special reference to North America. Agriculture, Ecosystems, and Environment 52:67-91.
  8. Heinz GH, Percival HF, Jennings ML. 1991. Contaminants in American alligator eggs from Lake Apopka, Lake Griffin, and Lake Okeechobee. Environ Monit Assess 16:277-285.
  9. Koes RE, Quattrocchio F, Mol JNM. 1994. The flavonoid biosynthetic pathway in plants: Function and evolution. BioEssays 16:123-132.
  10. Kurzer MS and Xu X. 1997. Dietary phytoestrogens. Annu Rev Nutr 17:353-381.
  11. Levin S. 1999. Fragile Dominion: Complexity and the Commons. Philadelphia, PA; Perseus Books.
  12. Lubchenco J. 1998. Entering the century of the environment: A new social contract for science. Science 279: 491-7.
  13. McLachlan JA. 2001. Environmental signaling: What embryos and evolution teach us about endocrine disrupting chemicals. <I>Endocr Rev</I> 22:319-341.
  14. Nguyenle T, Wang E, and Cheung AP. 1995. An investigation on the extraction and concentration of isoflavones in soy-based products. J. Phamaceutical and Biomedical Analysis 14:221-232.
  15. Rolland R, Gilbertson M and Colborn T, eds. 1995. Environmentally induced alterations in development: A focus on wildlife. Environ Health Perspect 103(Suppl 4): 3-5.
  16. Smith J. 2000. The Daily Globe: Environmental Change, the Public, and the Media. London, UK; Earthscan Publications, Ltd.