Les perturbations hormonales
Les produits chimiques trouvés dans lenvironnement accroissent les cas
dinfertilité et affectent la croissance des organismes sauvages au Canada. À long
terme, la croissance de lêtre humain en sera de même accablée. En plus
daffecter le système de reproduction, les produits toxiques peuvent endommager nos
Les hormones produites par le système endocrinien, de pair avec le système nerveux,
commandent le comportement des cellules. Ces hormones sont de puissants produits chimiques
qui accomplissent leur fonction à de basses concentrations. À de très basses
concentrations, certains produits synthétiques imitent le rôle des hormones et agissent
sur les cellules en leur commandant de se comporter de façon dysfonctionnelle, doù
en résultent des conséquences qui varient dans leur degré de gravité.
« Le rêve séduisant selon lequel "les produits chimiques veillent à la
vie" se transforme en un cauchemar où des hormones imposteurs détournent le
comportement de nos cellules, affectent nos facultés intellectuelles, provoquent
linfertilité et le cancer. »
"The seductive dream
a better life through chemicals
a nightmare in which rogue hormones hijack our cells, triggering learning disabilities,
(Aziz 1998: 48)
Lia A. Daborn
Conservation Council of New Brunswick
in the environment are sabotaging fertility and development of wildlife in Canada and, in
the long run, in humans. Developing children and fetuses are most vulnerable to the
effects of toxic chemicals known as hormone mimics or endocrine disruptors.
These chemicals disrupt the normal hormonal messages that tell a body when and how to
The effect of toxic contaminants in the environment first came to
public attention in 1962 through biologist Rachel Carsons book, Silent Spring,
in which she described the potentially fatal effects on wildlife resulting from use of
DDT. However, more than a quarter-century later, chemicals may still be undermining our
ability to reproduce, to learn and to think.
How does hormone disruption work?
The endocrine system is one the bodys three integrating networks.
It is made up of glands, hormones, and target cells that comprise a complex network of
chemical signals and messages controlling many immediate and lifelong bodily responses and
functions. Hormones produced by the endocrine system act as messengers, working with the
nervous system to tell cells how and when to:
maintain the bodys internal steady
state (nutrition, metabolism, excretion, water and salt balance);
react to stimuli from outside the body;
regulate growth, development and
produce, use and store energy.
In order to send messages, hormones lock into receptors and, like a key
in a lock, send the required signal. At very low concentrations, synthetic compounds that
mimic hormones can insert themselves into the receptor and either turn on cell activity at
the wrong time, or block the appropriate activity by occupying the receptor site (see
Hormones are very potent chemicals that operate at low concentrations.
Estradiol, for instance, is a natural hormone that can cause a response in the parts per
trillion (ppt) range. This sensitivity allows for variations in offspring from the same
genetic code. However, it also makes the endocrine system vulnerable to serious disruption
if something interferes with normal hormone levels.
Interference with hormone functions is particularly dangerous to
developing embryos and newborn babies. Such interference may emerge later in life as lower
sperm counts, cancers, miscarriages and tubal pregnancies, impaired learning ability,
reduced immunities and behavioural disorders such as hyperactivity. The most dramatic and
troubling sign that hormone disruptors may already be taking a toll is found in reports
that human male sperm counts have plummeted over the past century (Carlsen et al.,
Children are most vulnerable to the potential effects of hormone
disrupting chemicals due to the high level of hormonal activity taking place during
development. Prior to birth the process of sexual differentiation is highly dependent on
hormones to take the unisex embryo and guide its development into a male or a female.
Hormonal cues delivered at the right moment guide the expression of the cells as tissues
make "now or never" choices about the direction of development.
Damage by hormone disruption is trans-generational (can affect
offspring); it may be apparent at birth, but often emerges later in life. The exposed
mother may be completely unaffected, but her children may have trouble producing the next
The timing rather then the level of exposure is crucial. For example,
exposure to one very low dose of a hormone disrupting substance during a critical stage of
embryonic development can cause permanent damage. The damage caused by hormone disrupting
chemicals is cumulative (tending to accumulate or increase) and synergistic (tending to
combine to even greater amounts). This makes it impossible to generalize what the effect
of human exposure to a chemical may be. (For more about the process and effects of hormone
disruption on humans and wildlife, see Colborn et al., 1996.)
"unless the environmental load of synthetic hormone disruptors is abated and
controlled, large scale dysfunction at the population level is possible."
(The Wingspread Consensus Statement
 is signed by 21 scientists. Reprinted in
Colborn et al., 1996.)
Research into hormone imposters has increased, and reveals threatening
information. Recent reports of PCB levels in breast milk of northern native populations
demonstrate that no place on earth is safe from chemical contamination. To date,
scientists have identified more than 50 chemicals that act as hormone disruptors (Aziz,
1998). Environmental estrogens are the most commonly discussed, but chemicals can also act
as androgens (male hormones) and thyroid hormones (regulating metabolism and growth). Such
chemicals will most drastically affect the reproductive organs, brain, thyroid, liver,
kidney and immune system (Aziz 1998).
Despite the studies and research findings, some still do not believe
that changes in populations and reproduction are related to chemical contamination in the
environment. The problem is that there is no hard and fast proof that these effects are
directly linked to one specific combination of chemicals or to one specific episode.
Therein lies the real threat: how long do we have to wait before realizing there is a
problem and attempting to do something about it? How many generations have to be affected
before concrete action is taken to incorporate precaution into the everyday use of
chemicals and increase the testing of chemicals, both before and while they are in common
everyday usage? The longer we wait, the greater the implications will be, not only for
wildlife populations but human as well.
ON THIS TOPIC:
Aziz, L. 1998. "The Endpoint", in Equinox April/May pp
Colborn, Theo, Dianne Dumanoski and John Peterson Myers. 1996.
"Our Stolen Future" (A Dutton Book)
Carlsen, E., A. Giwercman, N. Keiding, and N. Shakkebaek. 1992.
"Evidence of Decreasing Quality of Semen During Past 50 years." British Medical
Carson, R. 1962. Silent Spring.
Environmental Health Perspectives, vol.106 No.1, Jan. 98
Jacobson, J., S. Jacobson, P. Schwartz, G Fein, and J Dowler. 1984.
"Prenatal Exposure to Environmental Toxin: A Test of the Multiple Effects
Model," Developmental Psychology 20 (4): 523-32
Mausberg, B. and P. Muldoon. 1997. "A Taste of Canada"
Canadian Environmental Law Association, April
The Environmental Working Group. n.d. The Pesticide Data Program. US.
Dept. of Agriculture
US Natural Resources Defense Council. 1989. "Intolerable Risk:
Pesticides in our Childrens Food"
("Worst First: High Risk Insecticides,
Childrens Foods and Safer Alternatives")
(Rachels Environment and Health Weekly)
(PANUPS: Pesticide Action Network North America Updates Service)
(Endocrine Disruption Information)