Gradually during recent years a new body of knowledge has developed
showing that some chemicals in food and water can mimic hormones and
disrupt the development of living things like fish, birds, and mammals,
including their sexual development.
In some cases, the effects on wildlife have been dramatic. For example,
male herring gulls on Lake Ontario, exposed to DDT and other
organochlorine compounds, developed female sex organs. Female-female
pairing has been observed in herring gulls on Lake Michigan and on
Santa Barbara Island, California. Because humans share the same basic
mechanisms of growth and development as wildlife, an increasing number
of scientists has become concerned that humans may already be affected
without recognizing it.
In July of this year an international group of 21 scientists met at
Wingspread in Racine, Wisconsin to assess what is known about these
matters. They have now released a "consensus statement" containing
information and opinions about the nature and possible causes of these
problems. The five-page statement is called "Chemically Induced
Alterations in Sexual Development: The Wildlife/Human Connection."
Hormones are produced by the endocrine system--a bodily system
consisting of specialized cells, tissues, and organs that create and
secrete (usually into the blood) organic chemicals called hormones,
which then regulate other kinds of cells in the body. Particular
hormones only affect particular cells that contain "receptors" for
those hormones. A small amount of a hormone attaches to a "receptor
site" and the hormone-receptor pair then initiates a cascade of
chemical changes, often with major and far-reaching consequences.
The endocrine system shares with the nervous system the job of
adjusting the body's response to a changing external environment. The
nervous system copes with environmental changes on an immediate basis,
whereas the endocrine system copes with environmental changes on a
sustaining basis. For example, when the body gets cold, the nervous
system causes shivering, which raises the body's temperature. But each
month it is the endocrine system that starts the human female menstrual
cycle. In a developing fetus, it is the endocrine system that regulates
cell division and organ differentiation. The endocrine system regulates
pattern and timing of bird migration and of hibernation in mammals.
Examples of endocrine glands in humans include the adrenal gland,
pancreas, thyroid, pituitary, ovaries and testes.
The scientists gathered at Wingspread last July focused on the sex
hormones--the androgens that make males look and act like males and the
estrogens that make females look and act like females. The Wingspread
Statement begins, "Many compounds introduced into the environment by
human activity are capable of disrupting the endocrine system of
animals, including fish, wildlife, and humans. The consequences of such
disruption can be profound because of the crucial role hormones play in
"The following consensus was reached by participants at the workshop.
". We are certain of the following:
"A large number of man-made chemicals that have been released into the
environment, as well as a few natural ones, have the potential to
disrupt the endocrine system of animals, including humans. Among these
are the persistent, bioaccumulative, organohalogen compounds that
include some pesticides (fungicides, herbicides, and insecticides) and
industrial chemicals, other synthetic products, and some metals.
"Many wildlife populations are already affected by these compounds. The
impacts include thyroid dysfunction [impaired or abnormal functioning]
in birds and fish; decreased fertility in birds, fish, shellfish, and
mammals; decreased hatching success in birds, fish and turtles; gross
birth deformities in birds, fish and turtles; metabolic abnormalities
[impaired or abnormal use of energy, manufacture of tissue, or handling
of resulting wastes] in birds, fish, and mammals; behavioral
abnormalities in birds; demasculinization and feminization in male
fish, birds, and mammals; defeminization and masculinization of female
fish and birds; and compromised [impaired] immune systems in birds and
"The patterns of effects vary among species and among compounds. Four
general points can nonetheless be made: (1) the chemicals of concern
may have entirely different effects on the embryo, fetus, or perinatal
[meaning "near the time of birth," from the 28th week of pregnancy
through the first week of life, in humans] organism than on the adult;
(2) the effects are most often manifested in offspring, not in the
exposed parent; (3) the timing of exposure in the developing organism
is crucial in determining its character and future potential; and (4)
although critical exposure occurs during embryonic development [from
conception through the end of the second month of pregnancy], obvious
manifestations [effects] may not occur until maturity.
"Laboratory studies corroborate the abnormal sexual development
observed in the field and provide biological mechanisms to explain the
observations in wildlife.
"Humans have been affected by compounds of this nature, too. The
effects of DES (diethylstilbesterol), a synthetic therapeutic agent,
like many of the compounds mentioned [in footnote 1] are estrogenic
[meaning they act like estrogen, a family of female sex hormones].
Daughters born to mothers who took DES now suffer increased rates of
clear cell adenocarcinoma [cancer], various genital tract
abnormalities, abnormal pregnancies, and some changes in immune
responses. Both sons and daughters exposed in utero [while in the
uterus] experience congenital anomalies of their reproductive system
and reduced fertility. The effects seen in in utero DES-exposed humans
parallel those found in contaminated wildlife and laboratory animals,
suggesting that humans may be at risk to those same environmental
hazards as wildlife."
The Wingspread Statement goes on:
". We estimate with confidence that:
"Some of the developmental impairments reported in humans today are
seen in adult offspring of parents exposed to synthetic hormone
disruptors (agonists and antagonists) released in the environment. The
concentrations of a number of synthetic hormone agonists and
antagonists measured in the U.S. human population today are well within
the range and dosages at which effects are seen in wildlife
populations. [An agonist is a chemical that is not a hormone but mimics
a natural hormone; an antagonist interferes with a natural hormone.] In
fact, experimental results [in animals] are being seen at the low end
of current environmental concentrations [in humans].
"Unless the environmental load of synthetic hormone disruptors is
abated and controlled, large scale dysfunction at the population level
is possible. The scope and potential hazard to wildlife and humans are
great because of the probability of repeated and/or constant exposure
to numerous synthetic chemicals that are known to be endocrine
". Current models predict that:
"... Both exogenous (external source) and endo-genous (internal source)
androgens (male hormones) and estrogens (female hormones) can alter the
development of brain function.
"Any perturbation [disturbance] of the endocrine system of a developing
organism may alter the development of that organism: typically these
effects are irreversible. For example, many sex- related
characteristics are determined hormonally during a window of time in
the early stages of development, and can be influenced by small changes
in hormone balance. Evidence suggests that sex- related
characteristics, once imprinted, may be irreversible."
The Wingspread statement then gives three reasons why these predictions
are subject to "many uncertainties:" (1) effects of exposure of humans
are not well understood, especially exposure of embryos; (2) data on
reproductive problems in wildlife exist but data on behavior changes
are not so readily available; (3) the potency of many synthetic [human-
created] estrogenic chemicals is not well known.
The British publisher, Elsevier Applied Science, will publish a book on
this subject by next fall. Until then, the best source of information
is Theodora E. Colborn and others, GREAT LAKES GREAT LEGACY? available
for $20.00 (plus $2.00 shipping) from: World Wildlife Fund, P.O. Box
4866, Hampden Post Office, Baltimore, MD 21211; phone (301) 516-6951.
For $3.00 plus stamped, self-addressed envelope, we can send you the
Wingspread statement itself.
[More on this subject coming soon.]
 A footnote on page 1 of the Wingspread Statement says, "Chemicals
known to disrupt the endocrine system include: DDT and its degradation
products, DEHP (di(2-ethylhexyl)phthalate), dicofol, HCB
(hexachlorobenzene), kelthane, kepone, lindane and other
hexachlorocyclohexane congeners, methoxychlor, octachlorostyrene,
synthetic pyrethroids, triazine herbicides, EBDC fungicides, certain
PCB congeners, 2,3,7,8-TCDD and other dioxins, 2,3,7,8-TCDF and other
furans, cadmium, lead, mercury, tributyltin and other organo-tin
compounds, alkyl phenols (non-biodegradable detergents and anti-
oxidants present in modified polystyrene and PVCs), styrene dimers and
trimers, soy products, and laboratory animal and pet food products."
Descriptor terms: endocrine disrupters; racine, wi; wi; wildlife;
sexual development; endocrine system; fish; birds; herring gulls;
mammals; humans; reproductive hazards; reproductive disorders; ddt;
des; pesticides; herbicides; insecticides; fungicides; theo colborn;