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Last updated January 1, 2014

Hormonal Sabotage

Synthetic chemicals in the environment may be wreaking havoc with the endocrine systems of humans and animals

Excerpted from Our Stolen Future, by Theo Colborn, Diane Dumanoski, John Peterson Myers. Dutton Signet, 1996

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

Part I: Introduction - Omens
In July 1991, a group of scientists-including Theo Colborn, then a fellow at the W. Alton Jones Foundation, and John Peterson (Pete) Myers, the foundation's director, gathered at the Wingspread conference center near Racine, Wisconsin, to discuss their concerns about hormone-disrupting chemicals in the environment. They were disturbed by mounting evidence that synthetic compounds found in pesticides and industrial chemicals were wreaking havoc with endocrine systems.

The scientists shared information on a broad range of species with problems that ranged from thyroid dysfunction, decreased fertility, and gross birth deformities to feminization of males, masculinization of females, and compromised immune systems. Many of the chemical compounds under discussion had an affinity for estrogen receptors in particular and their effects on wildlife paralleled those seen in humans exposed to the synthetic estrogen DES (diethylstilbestrol). Although environmental hormone disrupters were known mainly for their effects on wildlife, the scientists at the Wingspread meeting concluded that the substances had the potential to cause large-scale dysfunction in humans as well.

In Our Stolen Future, a new book excerpted here, Theo Colborn and Pete Myers have joined forces with environmental science writer Dianne Dumanoski to survey the problem. They have found that hormone-disrupting chemicals are ubiquitous and that the pathologies they cause may result even from extremely low levels of exposure. Although many synthetic chemicals have been tested for carcinogenic effects, few have been scrutinized for their impact on the human endocrine system. As the authors of Our Stolen Future observe, if such substances are causing wide-scale disruption of the hormones that enable us to grow and reproduce, we may be witnessing an evolutionary tragedy in the making. -Bruce Stutz, Editor in Chief, Natural History

OMENS

The late 1940s: Gulf Coast, Florida
Charles Broley began his study of Florida's bald eagles in 1939 at the suggestion of the National Audubon Society. In the early 1940s, Broley followed 125 active nests along the peninsula's west coast from Tampa to Fort Myers and banded some 150 young eaglets each year. In 1947 the picture suddenly changed. The number of eaglets began dropping sharply and in the succeeding years, Broley witnessed bizarre behavior in many of the eagle pairs. At nesting sites he had visited for thirteen years, two-thirds of the adult birds appeared indifferent to nesting, courtship, and mating. As Broley continued his work through the mid-1950s, he became convinced that 80 percent of Florida's bald eagles were sterile.

The late 1950s: England
Although otters were no longer as plentiful as in earlier times, the traditional sport of otter hunting continued relatively unchanged into the mid-twentieth century. To the sounds of horns and baying hounds, hunters still pursued their prey; by the end of the 1950s, however, they began to have trouble finding otters to hunt. When conservationists finally took note of the problem, some suspected the pesticide dieldrin, but later work pointed to another synthetic chemical.

The mid-1960s: Lake Michigan
The mink industry that had grown up around the Great Lakes because of the ready supply of cheap fish had begun to falter because of the animals' mystifying reproductive problems. Females weren't producing pups. Michigan State University researchers eventually linked the reproductive failure to PCBs (polychlorinated biphenyls), a family of synthetic chemicals used to insulate electrical equipment. Curiously, a decade earlier, other mink herds in the Midwest had crashed after the animals were fed scraps from chickens that had been given the growth-promoting drug DES. Although the symptoms were strikingly similar to those of the Michigan incident, the second crash of fish-fed mink could not be linked to DES.

The early 1970s: Channel Islands, Southern California
Working on San Nicolas Island in 1968, Ralph Schreiber, of the Los Angeles County Natural History Museum, spotted some gull nests with unusually large numbers of eggs. Since gulls rarely incubate more than three eggs at a time, Schreiber immediately suspected that more than one female was laying in these nests. Four years later, George and Molly Hunt, of the University of California at Irvine, noticed the same phenomenon on Santa Barbara Island. They also saw thinning eggshells in the gull colony, leading them to expect the birds were suffering from DDT exposure. Over the next two decades, nesting female pairs would be found among the herring gulls in the Great Lakes, glaucous gulls in Puget Sound, and roseate terns off the coast of Massachusetts. Were the females sharing nests because of a shortage of males?

The 1980s: Lake Apopka, Florida
Surveys showed that in some Florida lakes, 90 percent of alligator eggs hatched, but at Lake Apopka the hatching rate barely reached 18 percent. Even worse, half of those that hatched died within ten days. Louis Guillette, a University of Florida reptile biologist, felt there was little question that the problems were linked to a 1980 chemical spill, after which more than 90 percent of the alligators disappeared. But why, after the waters were again clear, were researchers still finding hatching problems, and why did at least 60 percent of the males have abnormally tiny penises?

1990s: Copenhagen, Denmark
Over the years, Niels Skakkebaek, a reproductive researcher at the University of Copenhagen, had seen more and more human sperm abnormalities, as well as a drop in the typical sperm count. At the same time, Denmark's rate of testicular cancer had tripled. Skakkebaek also noticed low sperm counts and unusual cells in the testes of men who developed this type of cancer. Were the findings connected? He and his colleagues eventually reviewed sixty-one studies, most from the a United States and Europe, but also from Asia, South America, and Africa. They were stunned to find that average human male sperm counts had dropped by almost 50 percent between 1938 and 1990.

Next...

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.