=======================Electronic Edition========================
. .
. RACHEL'S ENVIRONMENT & HEALTH WEEKLY #490 .
. ---April 19, 1996--- .
. HEADLINES: .
. FLYING BLIND .
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OUR STOLEN FUTURE, PART 3: FLYING BLIND
OUR STOLEN FUTURE, the new book on hormone-disrupting
chemicals,[1] provides many lessons about our use of chemicals,
and about our reliance on science as a guide for public policy.
Here is a short discussion of the main lessons we find in the
book (numbers inside parentheses are page numbers from the book):
** Genes are not destiny. Many people seem to think that we may
be able to explain everything from cancer to homosexuality by
locating the responsible genes. But in a series of scientific
papers starting in 1980, Frederick vom Saal at University of
Missouri demonstrated that there are other powerful forces
shaping individuals--both females and males--before birth. Genes
are not the whole story. Before birth, levels of both male and
female sex hormones in the womb can affect the physical
characteristics and the behavior of mice, giving rise to great
variation in offspring that are genetically identical. By
examining human twins, scientists have now revealed similar
effects in humans.[2] Thus we now know that hormones are a way
that nature provides variation within a species. Profound
variation among individuals can be caused by miniscule hormone
differences in the womb, differences of a few parts per trillion.
(One part per trillion is a million times lower than one part
per million.) This is a degree of sensitivity to hormones that
approaches the unfathomable, a sensitivity, vom Saal says,
"beyond people's wildest imagination." This exquisite
sensitivity provides rich opportunities for creating varied
offspring from the same genetic stock. However, the dark side is
that this same sensitivity also makes the reproductive system
vulnerable to serious disruption if something interferes with
normal hormone levels. (pgs. 39-41)
** The exposure of a million American women to the drug, DES, in
the 1960s and 1970s showed that the human body could mistake a
synthetic (human-created) chemical for a natural hormone. (pg. 66)
** Another lesson from the work of vom Saal and others is that
hormones in the womb permanently program (and organize) cells,
organs, the brain, and behavior prior to birth, in many ways
determining an individual's course for life. (pgs. 39-40)
** The dose of hormones that an embryo receives is not the only
thing that matters; the TIMING of the dose --WHEN it occurs
during development in the womb --can be as important as the dose
itself. (pgs. 50-51)
** Birth defects may not be noticeable at birth. Serious effects
of hormones on the unborn and on the newborn may not be
recognizable for decades. (pg. 66)
** In fact, birth defects may never become visible at all, but
may involve cellular damage that undermines an organism's ability
to survive. For example, exposure to the drug DES, a synthetic
hormone, gave rise to a rare form of cancer in female children of
DES-exposed women. (pg. 66)
** Mice and humans share a common fate. To an astonishing
degree, evolution has retained through hundreds of millions of
years a basic strategy for embryonic development in vertebrates
[creatures with a backbone] which depends on hormones.
Regardless of whether the offspring is a human or a mouse, a
whale or a bat, a turtle or an alligator, hormones regulate its
development in fundamentally the same way. In the field of
cancer research, scientists argue that data gathered from
experiments on mice may not reveal anything useful about humans.
This uncertainty occurs because the underlying causes of cancer
are poorly understood. On the other hand, the working of
hormones is better understood, and knowledge gained from
experiments on non-humans CAN reveal useful information about
humans. "It is important to take the effects we see in animals
seriously," says Dr. Earl Gray, a senior research biologist with
U.S. Environmental Protection Agency [EPA]. (pg. 66)
** Industrial chemicals at exceedingly low levels can combine
together to produce additive effects. Dr. Ana Soto at Tufts
University combined 10 hormone disrupters, each at one-tenth of
the dose required to produce a minimal response; she found that
the combination produced a response.[3] Thus combinations of
chemicals must be taken into account when we try to learn how
much "effective exposure" we are getting to hormone-disrupting
chemicals.
** Testing hormones at high doses may reveal no effects whereas
testing the same hormones at low doses may reveal dramatic
effects. This is contrary to the traditional assumptions of
toxicology [study of poisons]. The dose-response curve for many
hormones is U-shaped: at low doses, the hormones cause effects
but at high doses the system becomes overwhelmed and shuts down.
This has profound implications for testing. Traditionally,
chemicals have been tested on laboratory animals at high doses;
now we know that tests must be conducted at low doses as well.
(pgs. 169-170)
** Up to now our concept of injury from toxic chemicals had
focused on two things: (a) whether a chemical attacks the DNA
inside cells, possibly causing cancer; or, (b) whether a chemical
damages and kills cells, the way poisons do. However,
hormone-disrupting chemicals may not kill or damage cells, and
they may not damage DNA. Thus they do not fit the definition of
"poisons" or "carcinogens" yet they may cause great harm by
disrupting normal growth and development of many organs and
tissues, including sex organs, the brain, the nervous system, and
the immune system. The key concept in thinking about this kind
of toxic assault is the disruption of chemical messages. (pgs.
203-204)
** The traditional approach to toxic chemicals is to look for
disease as a result of exposure. However, hormone-disrupting
chemicals may not cause "disease" at all: they may cause
diminished function --reduced IQ, poorer short-term memory,
diminished ability to pay attention, reduced sperm count. These
are not signs of "disease" yet they are toxic effects that can be
caused in some species by some hormone-disrupting chemicals.
(pgs. 205-206)
** To screen for chemicals that cause diminished function, it
will be necessary to look for developmental effects across three
generations. The first generation (the generation that gets the
initial exposures) may not be affected at all. The second
generation may have diminished function (for example, diminished
ability to reproduce) but the actual effects may not be apparent
until the third generation (the grandchildren of the exposed
generation). (pg. 207)
** We are flying blind. (pgs. 243, 246) We cannot know whether
the ominous shape looming into view is a cloud bank or a
mountain. If anything is certain, it is that we must expect more
unpleasant surprises. We are flying blind; we can never know
that new chemicals are safe (though, if we chose to, we could do
a much more thorough job of testing them than we've done in the
past).
To show that we are flying blind, OUR STOLEN FUTURE relies on the
evidence of hormone-disrupting chemicals and of depletion of the
earth's ozone shield by human-created chemicals (see REHW #246,
#259, #285). But there is much additional evidence that could
have been cited as well. For example, during just the past 25
years, we have been surprised by:
** Global warming brought on by combustion of fossil fuels (REHW
#467, #466);
** Mercury build-up to toxic levels in the bodies of fish
(chiefly from burning coal, oil, and municipal solid waste) (REHW
#291);
** Increasing birth defects in American children. Of 38 kinds of
birth defects for which the Centers for Disease Control maintains
records, 29 have increased during the past 20 years (REHW #410,
#411);
** Steadily increasing cancers, particularly of the reproductive
system (prostate; testicles; female breast) and nervous system
(brain) (REHW #412, #447, #462);
** The astonishing toxicity of a family of chemicals called
dioxins and furans (including some PCBs, or polychlorinated
biphenyls), which now contaminate the entire planet from the
depths of the oceans to the polar ice caps (REHW #390, #391,
#414);
** The accelerated loss of species, which, according to the
fossil record, is now occurring at rates 10 to 1000 times as fast
as natural background rates that were occurring before humans
appeared on the scene (REHW #441);
** Acid rain damaging lakes, killing trees, stunting forests, and
washing nutrients from soils across much of the northeastern
U.S., southern Canada, and northern Europe (REHW #476); **
Rapidly increasing immune system disorders such as asthma (REHW
#374) and diabetes (REHW #417);
** Epidemics of disease among marine mammals (seals, dolphins,
etc.), apparently related to chemical contamination and to blooms
of toxic algae caused by excesses of nutrients (chiefly nitrogen
and phosphorus) in near-shore marine ecosystems (REHW #466);
** Diminished IQ and reduced ability to concentrate among 1.7
million American children and 300 to 400 thousand fetuses (at any
given moment in time), as a result of exposures to the toxic
metal, lead (REHW #369);
** Disappearance or decline of some frog and other amphibian
populations worldwide (REHW #380, #441);
** Steep declines or near-total depletion of fish stocks at 13 of
the world's 17 major fisheries (REHW #399).
** Decline of 50% in sperm among men in industrial countries
(REHW #432, #446, #448), and a significant loss of sperm quality
during the same period.
** A 60% increase in the rate of migraine headaches among
Americans during the period 1980 to 1990. Most (71%) of the
increase occurred among people aged less than 45 years.[4]
This does not exhaust the evidence, but represents a fair sample
of the kinds of problems that have suddenly loomed into view
since 1970. Have we encountered the last of such unsuspected and
unlooked-for problems? Certainly not. No, there doesn't seem to
be any doubt about it: we are rushing forward at high speed with
no sure way to learn what hazards lie ahead. We really are
flying blind. To us, this seems the most important lesson of OUR
STOLEN FUTURE.
Under such circumstances, can science provide us with adequate
guidance? Next week.
--Peter Montague
===============
[1] See REHW #485 and #486, reviewing Theo Colborn, Dianne
Dumanoski and John Peterson Myers, OUR STOLEN FUTURE (N.Y.:
Dutton, 1996).
[2] F. vom Saal and F. Bronson, "Sexual Characteristics of Adult
Female Mice Are Correlated with Their Blood Testosterone Levels
During Prenatal Development," SCIENCE Vol. 208 (1980), pgs.
597-599. And see: M. Clark and others, "Hormonally Mediated
Inheritance of Acquired Characteristics in Mongolian Gerbils,"
NATURE Vol. 364 (1993), pg. 712. Hormones have also been shown to
affect humans exposed in the womb: D. McFadden, "A Masculinizing
Effect on the Auditory Systems of Human Females Having Male
Co-Twins," PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCE Vol. 90
(1993), pgs. 11900-11904.
[3] Reported in Ana M. Soto and others, "The Pesticides
Endosulfan, Toxaphene, and Dieldrin Have Estrogenic Effects on
Human Estrogen-Sensitive Cells," ENVIRONMENTAL HEALTH
PERSPECTIVES Vol. 102, No. 4 (April 1994), pgs. 380-383.
[4] "Prevalence of chronic migraine headaches -United States,
1980-1989," MORBIDITY AND MORTALITY WEEKLY REPORT Vol. 40, No. 20
(May 24, 1991), pgs. 331-333.
Descriptor terms: endocrine disrupters; hormones; our stolen
future; des; diethylstilbestrol; frederick vom saal; ana soto;
science; oceans; marine mammals; global warming; mercury; fish;
wildlife; birth defects; cancer; dioxins; furans; pcbs; species
loss; acid rain; lead; migraine headaches; theo colborn; john
peterson myers; dianne dumanoski;
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--Peter Montague, Editor
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