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Chronic Neuroimmune Diseases
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Last updated January 1, 2014

Part I.     Introduction | Omens
Part II.    The DES Paradigm: Crossing the tolerance threshold
Part III.    Here, There, Everywhere: Chasing the plastic impostors
Part IV.  Altered Destinies: Up against evolution
Part V.   Carson Redux: Theo Colborn creates her own legacy

Part VI: Altered Destinies: Up against evolution
Because our knowledge of hormone receptors has grown rapidly since they were first identified in the mid-1960s, we are now beginning to understand why synthetic chemicals have such dramatic effects across an astonishing range of species. Classic accounts of evolution tend to emphasize innovation and change, but there has also been a strong conservative streak in the history of life on Earth.

As scientists have explored hormone chemistry in various animals, they have marveled at the lack of change over millions of years of evolution. Whether in a turtle, a mouse, or a human, the endocrine system produces a chemically identical form of estrogen--estradiol--that binds to an estrogen receptor. The discovery of similar estrogen receptors in animals as different as turtles and humans argues for an endocrine system that arose early in the evolution of vertebrates.

Although research has demonstrated that imposter chemicals bind with the estrogen receptor, it has not yet illuminated why the receptor readily accepts them. The similar effects of DDT and DES led scientists to suspect a common structural feature, but to their bewilderment, they found that the receptor binds to chemicals with strikingly different structures.

The problem is large, and it is by no means restricted to environmental estrogens. Other classes of chemicals affect different parts of the endocrine system, such as thyroid- and testosterone-mediated processes. Still others inhibit the body's ability to produce steroid hormones in the first place.

The pressing question is whether humans are already suffering damage from half a century of exposure to endocrine-system disrupters. Have these chemicals already altered individual destinies by scrambling the chemical messages that guide development? Many of those familiar with the scientific case believe the answer is yes. But whether hormone-disrupting compounds are also having a broad impact across the human population is difficult to assess and even harder to prove. This is so because of the nature of the contamination, the transgenerational effects, and the long lag time before damage becomes evident.

The chemical age has created products, institutions, and cultural attitudes that require synthetic chemicals to sustain them. The task that confronts us over the next half century is one of redesign. We must find safer ways to meet human needs. As we work to create a future where children can be born free of chemical contamination, our scientific knowledge and technological expertise will be crucial. Nothing, however, will be more important to human well-being and survival than the wisdom to appreciate that however great our knowledge, our ignorance is even greater.

Part V: Carson Redux: Theo Colborn creates her own legacy
When Theo Colborn arrived in the District of Columbia In 1985, a fifty-eight-year-old grand-mother with a brand new Ph.D. in zoology, she bad no particular interest in biological effects of synthetic chemicals. She had been a pharmacist in New Jersey and a sheep rancher in Colorado before she decided to fulfill a long-held desire--to go to graduate school to study ecology. Through a life-long passion for watching birds, she had been drawn into the growing environmental movement and had spent years working as a volunteer on western water issues. Although some male advisers had been skeptical about investing energy in a fifty-something graduate student, Colborn persisted and won a slot as a congressional fellow at the Office of Technology Assessment.

Colborn next joined a project at the Conservation Foundation, a nonprofit think tank in the District of Columbia, to assess the health of the Great Lakes. Although the lakes' waters had improved markedly thanks to environmental regulation, Colborn's search through the scientific literature led her to believe that serious problems remained. Blinded like others by a preoccupation with cancer--which in the past three decades has become synonymous with the worth "toxic chemicals"--Colborn at first missed important clues.

Gradually, however, she began to see patterns emerging from the studies. The animals with the greatest problems proved to be top predators, such as lake trout, snapping turtles, and bald eagles. And although adult animals often appeared to be doing fine, their off-spring had myriad problems--primarily matters of derailed development.

Colborn then began to investigate the human-made contaminants found in the tissues of troubled wildlife. She found evidence in the scientific literature to confirm her hunch that many of these contaminants were disrupting hormones that regulate the body's vital processes and guide development. Seven years later, Colborn is still on the trail of hormonally active chemicals, exploring the implications of such contamination for wildlife and human health. -Dianne Dumanoski

Back to Part I

Colborn, T., D. Dumanoski, J. P. Myers. 1996. Hormonal Sabotage. This article and the ones linked to it was originally published in Natural History, March 1996, 105(3):42-49. Excerpted from the book Our Stolen Future.

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