Endocrine Disrupters

Ralph Ryder Ralph at tcpub.demon.co.uk
Thu Apr 10 13:10:13 EST 1997

Several people have asked for the references from this article, so I am
reposting it now.

Endocrine disruptors, also called "environmental hormones," are man-made
chemicals that act like hormones, especially estrogen’s, and interfere
with the normal functions of the bodies hormone system.

        Evidence exist that many common chlorinated substances such as
PCBs, dioxin, and many pesticides act as endocrine disruptors.

        Over the last fifty years the chemical industry has showered the
world with between 70,000 to 100,000 new chemicals compounds. Many of
these chemicals were intended to have a biological effect and are now
having a diverse range of devastating effects on human health. The
operative syllable in the word "pesticide" is ‘cide’, Latin for "kill,"
so it would not be unreasonable to concluded they could poise a threat
to human health.(1)

An Oversight?
        For years scientists, when talking about the toxicity of
chemicals, have only been concerned in determining whether a chemical
was capable of causing cancer. Was it purely an oversight not
considering other dangers to human health? Or was it down to industrial
economics and political interests suppressing science with devastating
consequences for us all? If we look at a few facts we will see the
evidence of some chemicals ability to cause more than cancer has been
staring us in the face for decades.

        The first evidence chemicals were able to affect animals in
other ways besides killing them is generally believed to have been in
the 1950s. It was then that  the ability of industrial chemicals to
damage the reproductive systems of wildlife was generally believed to
have  first been observed. But it was in the early 1930s that
researchers discovered that increasing the bodies natural level of the
hormone estrogen in pregnant rats, caused sexual abnormalities in their
offspring. Twenty years later Burlington & Lideman suggested that some
synthetic chemicals were indeed "hormonally" active.(2)

        Rachel Carson warned the world in the 1960s that "...something
more sinister than straight forward poisoning was occurring - the actual
destruction of the birds ability to reproduce", when writing about
pesticides and their effects on wildlife.(3)

        In the early 1970s John McLachlan set up a group of researchers
at the National Institute of Environmental Health Sciences at Research
Triangle Park, North Carolina, to investigate the effects of
diethylstilbestrol (DES) on mice. This was after reports between 1966-69
that seven out of eight young women (aged between 15 & 22) treated for
vaginal adenocarcinoma (a clear-cell cancer of the vagina), had mothers
who had taken the ‘wonder drug’ DES during the first three months of
pregnancy. Cancer of the reproductive tract is extremely rare in such
young women, and clear-cell adenocarcinoma is rare even in women over
50, in whom it is normally seen. (17)
        Dosage levels of DES taken by the mothers’ varied widely ranging
from 1.5 to 150mg/day. Because of variations in the time during which
DES was administered, total doses ranged from 135 to 18,200 mg. No
consistent relationship between daily or total doses has been
identified, other than that exposure must occur before the eighteenth
week of gestation. (As of February/March 1976, 244 cases of DES-
associated clear-cell adenocarcinoma of the vagina had been

        In 1975 McLachlan and his colleagues published their findings in
the journal ‘Science,’ detailing the damage done to male mice exposed to
this synthetic estrogen before birth. McLachlan kept in close touch with
Dr. Arthur Haney who was studying the effects of DES on sons born to
women who had taken the drug. Time and time again they would find
something in a mouse and discover the same problem in humans as well.
McLachlan’s team warned of the problem of undescended testicles three
years before the same problem was reported in the sons of mother exposed
to DES.(4)

Fish, Wildlife, Humans
        The Wingspread Conference in July 1991, attended by 21 leading
experts in various fields of wildlife research, issued a statement that
        "...many compounds introduced into the environment were capable
of disrupting the endocrine system of animals, including fish, wildlife
and humans."  
They estimated 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."(5)

Hot Topic
        Research in the field of endocrine disruptors is one of the
hottest topics within the scientific community. To date researchers have
discovered at least 51 synthetic chemicals that disrupt the endocrine
system in one way or another. These included the large family of 209
compounds classified as PCBs, the 75 dioxins and the 135 furans which
have an abundance of documented disruptive effects.(4)
        The pesticides include chlorinated organic chemicals such as
DDT, toxaphene and kepone, but all organic chemical compounds have the
potential to disrupt, damage, and destroy the routine function of
organic systems.

        Many of these chemicals are extremely persistent in the
environment lasting for decades, sometime centuries. They are not
metabolised by bacteria or humans, and do not degrade in the
environment. The only major route of elimination is photodegradation
(break down due to sunlight), which is slow and occurs only in the air
or at the surface of water and soil under the right conditions. When
these chemicals bind tightly to organic matter in soil and sediments,
they will settle out and remain in the soil and sediments for
decades.(6) Some of these chemicals can alter sexual development, some
undermine intelligence and behaviour, others damage the immune system
and make children’s bodies less able to fight infections and diseases.
Although exposure took place in the womb, sometimes the effects don’t
appear until puberty or afterwards,  sometimes even in the next

Target Organs
        The endocrine system is that part of the body which produces
internal secretions or hormones. Hormones are very potent biologically
active substances that act as chemical messengers. They are released by
the brain, thyroid or other glands and are carried through the
bloodstream to ‘target’ organs where they trigger a response. These
responses direct and regulate critical functions of the body including
behaviour, development and reproduction. Body growth, organ development,
metabolism, and regular body processes such as kidney function, body
temperature, and calcium regulation are generally controlled by the
endocrine system. Hormones are also responsible for maintaining blood
pressure and reproductive cycling.(6)

Three Classes
        There are different ways that these chemicals can interfere
with, or disrupt, normal hormone activity and these can be put into
three classes: mimics, blockers and triggers.(6)

Mimics are chemicals that act like normal hormones in the body. An
excellent example of this type is DES. "DES for ALL pregnancies," said a
drug ad in 1957, boasting it produced "bigger and stronger babies." DES
was used to suppress milk production after childbirth, to treat symptoms
of the menopause, acne, prostate cancer and venereal disease in
children. It was even given to girls who had become ‘unfashionably’
tall.(4) The effects were not apparent at birth but came to light years
later with the development of vaginal adenocarcinoma (which led to
McLachlan’s studies) and an increased risk of endometriosis in daughters
of women who had taken the drug. 
        Sons born to these women have an increased frequency of
undescended testes, an increased risk of genital birth defects,
hypospadias (a defect where the urethra that carries urine does not
extend to the end of the penis) and a decreased adult sperm count.(4-6)

        The second group of disruptors are hormone "blockers." These
interfere with how naturally occurring hormones function. They often
bind to the same protein receptors as the real hormone. They do not
stimulate any action but just sit in the way of the natural hormone like
testosterone, preventing it doing the job nature intended. This can
result in problems in the reproductive development of males.(6)

        The third category of disruptors is the "triggers." These
include chemicals that interfere with natural hormones by attaching to
protein receptors and triggering an abnormal action. The abnormal action
may be growth at the wrong time (perhaps the cause of children as young
as four developing breasts and pubic hair?), an alteration of
metabolism, or the synthesis of a different product. The best known of
this "trigger" type of disruptor is dioxin and dioxin-like chemicals.
Dioxin acts through the hormone-like process, but neither mimics nor
blocks natural hormones. It initiates entirely new responses.(6)

Six Years Before
        Sons of Taiwanese women who were accidentally contaminated by
PCBs have developmental delays, symptoms suggesting attention deficit
disorder, and shortened penises at puberty. These effects were seen even
though the mothers’ exposures took place at least six years prior to the

        These, the DES results, and the effects of the drug thalidomide
on children of women who took perhaps only 2 or 3 tablets at 5 to 8
weeks into their pregnancy, (the critical time for the development of
arms and legs), tell us that it is not the dose of the drug or chemical,
but the timing that is crucial.(4)

The Fetus
        The unborn are undoubtedly the most vulnerable to the effects of
endocrine disruptors. Fetal development is the stage of life where
chemical messengers have the most impact at the lowest level. Adults can
be completely unaffected by regular exposure to an endocrine disruptor,
but the developing fetus can have its future completely changed.(7-8)

Windows of Development
        A variety of chemical exposures early in life can lead to
profound and irreversible abnormalities in the brain development of a
fetus. This has specific and narrow "windows of development," during
which exposure to endocrine disruptors can cause permanent damage. When
a particular window closes, any damage that might have occurred remains
and is irrepairable, the child carries that damage throughout its

        "It was only recently that scientists discovered we need thyroid
in the human embryo from the moment of conception and during the first
twelve weeks of development. They didn’t believe it was necessary until
then because the amounts in the body were so low they couldn’t detect
them. It is now known that if the thyroid is interfered with it can
affect the way the brain is wired and the intelligence and behaviour of
the child," said Theo Colborn.(9)

        Day 56 is the day sexual differentiation sets in, a crucial day
in all our lives. Yet as children we are still vulnerable for many years
as the development of the secondary sexual organs are not completed
until puberty, especially in the male.(9)

Impenetrable Shield
        For decades medicine had been dominated by the belief the
placental barrier was some kind of wonderful "impenetrable" shield,
protecting the developing fetus from harm from everything except
radiation. Yet from the very beginning the warning about increasing the
bodies natural balance of hormones were clear and ominous.

Scrambled Messages
        In the early 1930s researchers at the Northwestern University
Medical School gave an extra dose of estrogen to pregnant rats. At birth
their young showed abnormalities stemming from disrupted sexual
development. The females pups suffered structural defects of the uterus,
vagina and ovaries. The males had stunted penises and other genital
deformities. These tests showed that adding estrogen upset the natural
hormone balance, scrambled the chemical messages, and derailed sexual

Unique Species
        Unfortunately this information about the dark side of hormone
therapy was dismissed as being "irrelevant" to humans and only something
that happens to rodents. 
        This scepticism is not unusual among physicians who believe (and
industrialists would like the public to believe) that humans are a
unique species on the tree of life. Members of the medical and
scientific community now seem to be accepting what some animal
researchers had been trying to tell them for decades:
        "Chemicals can cause birth defects in humans as well as in

        The findings of research on behavioural and reproductive
differences related to hormone exposure in mice by Frederick Vom Saal, a
biologist at the University of Missouri, has opened a window on the
powerful role hormones have in the development of both sexes. It also
revealed the extreme sensitivity of developing mammals to just a slight
shift in hormone levels in the womb.(4)

One Drop
        Hormones are exceptionally potent and operate at parts per
         "like one drop of gin in a train load of 660 tankers," said
Theo Colborn,
        "...these concentrations are so low they can only be measured
using the most sensitive analytical methods."
        As little as one-tenth of a part of a trillion of estrogen is
capable of altering the course of development in the womb. This degree
of sensitivity, according to vom Saal: "...is beyond peoples wildest

        Surely given the extremely low levels of natural hormones
produced by the endocrine system to induce appropriate changes within
the body, there can be no level at which dioxin and other hormone
mimicking chemicals have no effect?  Yet the British government,
industry, and the Ministry of Agriculture, Fisheries and Food (MAFF)
talk of "insignificant amounts"- "safe doses" and "normal background
levels" in the range of 0.04 to 0.27 nanogrammes TEQ of dioxin for milk
in the UK. 

Breast Feeding
        It is not only while in the womb that children are at risk from
endocrine disruptors. Doing the most natural thing in the world for a
mother, breast feeding, carries a high risk for the child. In just six
months a breast fed baby in Europe and the United States gets the
maximum recommended lifetime dose of dioxin. Its average daily intake is
at least ten times higher than the average daily intake for an adult.
The same baby gets five times the allowable daily level of PCBs set by
the international health standards for a 150 pound adult.(4) More
alarming than this is the fact that after one year of nursing the daily
intake for breast fed infants is ten times the US Environmental
Protection Agencies ‘safe’ dose which is based on a lifetime of

        Should a women breast feed or not?
        "The fact that we may have to decide that or not tells us we
have gone way too far?" says Tom Webster (Department of Environmental
Health, Boston University).(10)
        While Dr. Paul Connett (St. Lawrence University) believes: 
        "When you tell a women to limit breast feeding you are looking
at the beginning of the end of mankind."(11)

Immune Protection
        Breast feeding not only strengthens the mother-baby bond, it
also provides the baby with important immune protection and substances
that enhance development. At the same time it exposes the child to a
number of chemical contaminates which include known hormone disruptors.
        "We know too little to judge how the undeniable benefits of
breast-feeding, balance against the risks of transferring hormonally
active contaminates. While it is of great concern, it is premature to
advise women against breast-feeding," believes Theo Colborn (4)

        Is the human population already suffering major problems as a
result of synthetic chemical contamination? Many scientists believe so.
Laboratory experiments, wildlife studies, the human DES experience, and
a great number of pediatricians from the US and Europe, are pointing to
the increasing frequency of genital abnormalities in children such as
undescended testicles, extremely small penises, hypospadias, and the
reduction in sperm count as being caused by hormone disrupting
chemicals.(4) (see also ‘Toxcat’ Vol. 2 No 2  Spring 1996) 

100% Proof
        Despite overwhelming evidence that something serious is
happening now, the British government and industrial scientists want to
 ...which individual chemicals cause the
....at what level of exposure?
 ...for how long?
 ...during which period of development?
 ...by what mechanism does the damage
occur?...before taking decisive action to reduce the amount of these
chemicals being released into the environment?

        Dr. Linda Birnbaum (USEPA) has stated: "...the mechanism of
[dioxin] action is much more complicated than we thought".(12)
        While Dr. Rall (MD, Ph.D.), (speaking of dioxin) believes:
"...we’re never going to know the mechanism."(13)

180 Years 
        To test the most commonly used 1,000 toxic chemicals in unique
combinations of three would require at least 166 million different
experiments, and this disregards the need to study varying doses. Even
if each experiment took just one hour to complete, with 100 laboratories
working round the clock seven days a week, testing all possible unique
three - way combinations, it would take over 180 years to

No Regulations
        When it’s a case of a chemical causing cancer, regulations turn
to a linear model which assumes that "no level is safe." Immune system
and reproductive effects through dioxin contamination appear to occur at
body burdens 100 times lower than those associated with cancer,(16) yet
endocrine disrupting chemicals are not included in regulations for
emissions from industrial facilities.

        Dr Barry Commoner, keynote speaker at the "2nd Citizens
Conference on Dioxin" in St Louis, MO (1994) told concerned community
activists’ that perhaps they should to look towards others, including
the food industry, to exert pressure on the chemical industry to
eliminate dioxin. Evidence shows that some sections of this industry are
no ‘knights in shinning armour’ rushing to protect the health of
        In Britain, farmers knowingly  allowed BSE infected cattle to
enter the food chain simply because the government was slow in
implementing a scheme to compensate them for infected cattle losses.
Abbatoir workers continued putting banned sections of cattle (spinal
cord) into the food chain until as late as 1996. Indeed, through the
pressure of agricultural economics, this section of the food industry
are deliberately contaminating the food chain with cancer causing -
hormone disrupting chemicals on a huge scale. DES, despite the problems
it has caused in the past, has been used for many years as an animal
feed supplement to promote growth in the United States. It was estimated
in 1994 that banning the use of DES (or equivalent levels of other
estrogens) in the U.S. would force farmers to spend £500,000,000 each
year in additional feed to produce the same amount of meat.
        In 1973 DES was conclusively shown to be a human carcinogen. It
is not disputed that the continued use of DES in livestock feed means
there will be low-level residues, in the parts per billion range, in
liver and perhaps occasionally in muscle meat. (17)
        Opponents to this practice argue it is hazardous to health as
there is no [safe] threshold level of a carcinogen, and exposure to DES-
treated meat increases the risk of estrogen-induced cancer in the
general population. Proponents use the long established industrial
argument that since DES acts purely as an estrogen, it is as safe as
natural estrogens. However,   it is considerably more stable than
natural estrogens, both in organisms and the environment, (17) and given
the persistence of man-made chemicals and the sensitivity of mammals to
just a slight shift in hormone levels, this side of the argument can no
longer be valid.
        "Man-made hormones (as produced by hormone-mimicking chemicals)
are different from natural hormones," said Dr Vyvyan Howard (Fetal &
Infant Toxico-Pathology Unit, Liverpool University). "They are
persistent.  Natural hormones will be destroyed within the body in half
an hour. Man-made hormones stay in the body for years switching on
enzyme systems." (7) 
        "We have had a very long time to adjust to natural estrogens",
said Dr. Carlos Sonnenschein (Tufts University School of Medicine,
Boston) "Most chemical manufactures have alternative inexpensive
chemicals they could use. When we discover a product contains estrogen
disruptors we should stop and look to alternatives." (18)

        Recent research has shown that many  chemicals considered
harmless as individual compounds, can act as a catalyst and magnify the
hormone disrupting powers of other chemicals. Combinations of two or
three pesticides can become 160 to 1,600 times more toxic than in their
individual form.(15)

Too Many Interests
        Under the present regulatory system the management and lobbyist
for the chemical industries have too much say. They already hold many
prominent positions on the newly formed Environment Agency (EA) and lost
no time in having cosy talks behind closed doors. Taking this into
account, plus the fact that many politicians have financial interests
with the industries causing the damage, it seems the problems caused by
endocrine disrupting chemicals will continue to increase for our future

        Blind to anything other than profit, industry continues to
release millions of tonnes of endocrine disrupting chemicals into the
environment. They can be found everywhere, from the sediments of the sea
bed, to the top of uninhabited mountain peaks - in the living tissues of
wildlife in regions as remote from industry as Antarctica and the Sahara
Desert. Each compound is theoretically capable of affecting living
creatures in totally unpredictable, devastating ways, either as
individual chemicals, or when combined with others. This proliferation
of synthetic chemicals and their organic link with living creatures mean
that every plant, insect, fish, animal and human being, is swimming
blindfolded in a sea of chemicals with frightening consequences.(1)

        Will the damage from these chemicals have to reach epidemic
proportions before governments and the general public, wake up to the
fact that the chemical industry has become much too powerful - a law
unto itself? Unborn children are paying a terrible price to keep
shareholders happy and profit margins high. 

1) "Toxic Nation" Fred Setterberg & Lonny Shavelson. John Wiley & Sons
Inc. ISBN 0-471-57545-3 
2) Burlington & Lindeman study: published in Proceedings of the Society
of Experimental Biology and Medicine 1950 
3) "Silent Spring" Rachel Carson. 1992.
4) "Our Stolen Future". Theo Colborn, John Peterson Myers, Dianne
Dumanski. Dutton Press 1996 ISBN 0 316 87546 5.
5) Chemically Induced Alterations in Sexual and Functional Development:
The Wildlife-Human Connection: The Wingspread Conference, July 26-28
Racine, Wisconsin 1991.
6) "Endocrine Disruptors" by Peter de Fur (Virginia Commonwealth
University) & Carolyn Raffensperger (Director of the Science and
Environmental Health Network). Rewritten for "Taking Action," Strategy
Recommendations from the 3rd Citizens Conference on Dioxin and Other
Synthetic Hormone Disruptors, Baton Rouge, Louisiana, March 15-17 1996.
7) Dr. Vyvyan Howard. Senior Lecturer, Fetal and Infant Toxico-
Pathology, Liverpool University. Presentation on "Endocrine Disruptors."
Communities Against Toxics/Greenpeace Conference: Ellesmere Port,
Cheshire, June 1996.
8) Rachel’s Environment & Health Weekly #499.
9) Theo Colborn "Hormone Copy Cats." WWF video. 1996.
10) Tom Webster Interview: ‘Toxcat’ ISSN 1355-5707 Vol. 1 No 3 Autumn
11) Paul Connett Interview: ‘Toxcat’ ISSN 1355-5707 Vol. 1 No 2 Spring
12) Dr. Linda Birnbaum (USEPA) Presentation to the Great Lakes Water
Quality Board 102nd Meeting, Chicago Illinois, July 15 1993.
13) Dr. Rall (M.D., Ph.D.) Presentation on Human Health Consequences of
Dioxin. Dioxins and Health: Truth or Consequences. Physicians for Social
Responsibility Conference, Salem Public Library, Salem, Oregon. 13 April
14) Rachel’s Environment & Health Weekly #447.
15) Rachel’s Environment & Health Weekly #498.
16)USEPA 1994.
17) "Toxic Substances In The Environment" B. Mangus Francis John Wiley &
Sons, Inc. ISBN 0-471-50781-4
18) Lecture, Liverpoool University 7 May 1996.

Copyright R Ryder: TC Publishing. 1996 All Rights Reserved

Taken from ToxCat ISSN 1355 5707

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