Evidence provided to support these claims of human and wildlife harm is largely from laboratory studies in which large doses are fed to test animals, usually rats or mice, and field studies of wildlife species that have been exposed to the chemicals mentioned above. In laboratory studies, high doses are required to give weak hormone activity. These doses are not likely to be encountered in the environment. However the process of bioaccumulation can r

esult in top-level predators such as humans to have contaminants at levels many million times greater than the environmental background levels (Guilette 1994). In field studies, toxicity caused by endocrine disruption has been associated with the presence of certain pollutants. Findings from such studies include: reproductive disruption in starfish due to PCBs, bird eggshell thinning due to DDT, reproductive failure in mink, small penises in alligators due to DDT and dicofol (Guillette 1994, Colburn et al 1996). In addition, a variety of reproductive problems in many other species are claimed to be associated with environmental contamination although the specific causative agents have not been determined. One recent discovery that complicates the situation is that there are many naturally occurring "phytoestrogens", or chemicals of plant origin that exhibit weak estrogenic properties.

Begley, Sharon and Daniel Glick. 1994. The estrogen complex. Newsweek-76-77.

Guillette, Louis J. Jr., Crain, D. Andrew, Rooney, Andrew A. and Daniel B. Pickford. 1995. Organisation versus Activation: The role of Endocrine-disrupting Contaminants (EDCS) during Embryonic Development in wildlife. Environmental Health Perspective's. 103 (Suppl 7): 157-164.

Kamrin, M. unknown. Environmental Hormones. Internet Reference www.ace.orst.edu

The detrimental effects of endocrine disruptors and particularly estrogenic mimics on the reproductive fitness can be seen at all developmental stages of an animal's life. The most dramatic effects occur while the animal is in utero and before puberty while the tissues are maturing and differentiating. Many of the damaging effect of endocrine disruptors on the reproductive and development processes of an organisms may not be evident until the animal reaches puberty, a time when sex hormones levels increase and formally dormant cells become active. Due to this factor it is difficult for researchers to study the direct effect of many of these chemicals. The fact that responses of animal subjects and humans alike to these chemicals parallel each other indicates that this problem will have far reaching and devastating consequences.

Sharpe, Richard M. and Niels Skakkebaek. 1993. Are oestrogens involved in falling sperm counts and disorders of the male reproductive tract? Lancet

Some common words found in the essay are:
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Approximate Pages = 7 (250 words per page double spaced)