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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.
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