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#753 - The Latest Hormone Science, Part 4; Disrupting Life's Messages, 02-Oct-2002

[In this series, we have been reviewing studies published during
the past two years in ENVIRONMENTAL HEALTH PERSPECTIVES, a
peer-reviewed journal published by the U.S. National Institutes
of Health. Our purpose has been to discover whether mainstream
scientists believe that industrial chemicals, released into the
environment, can interfere with the hormones of wildlife and
humans, leading to widepsread harm. It is abundantly clear that
they do. To keep abreast of the torrent of new studies of hormone
disruption appearing in dozens of journals, check in regularly at
http://www.ourstolenfuture.org.

Now the question becomes, "What does all this information about
hormone disruption mean?" One person eminently qualified to
comment on that question is Dr. J.P. Myers, a zoologist and
co-author (with Theo Colborn and Dianne Dumanoski) of OUR STOLEN
FUTURE, the book that pushed "hormone disruption" to the top of
the international environment-and-health agenda. The following
essay first appeared in the February, 2002, issue of OUR PLANET,
the journal of environmental sustainability published by the
United Nations Environment Program. See http://www.ourplanet.com.
We added the footnotes.]

Disrupting Life's Messages

by John Peterson Myers*

A revolution in scientific understanding of the impacts of
contamination on health is under way. As it unfolds, it is likely
dramatically to alter our understanding of the consequences of
pollutants for human well-being, and to require fundamental
changes in how chemicals are regulated. The revolution arises
from scientific discoveries which establish that many chemicals
both from the natural world and synthesized in laboratories
interfere with the natural chemical messaging systems that direct
the biological development of plants and animals, including
humans.

Virtually all biological development is under the control of
various chemical messaging systems that convey instructions from
the genes to their targets, thereby directing development.
Hormones, neurotransmitters and growth factors, among others, are
key elements of these message systems. Their successful
transmission of genetic instructions is vital to normal healthy
development, as they control almost if not every aspect of the
process from what sex a baby will become to how many fingers it
will have, to whether its brain is capable of intelligent
reasoning or whether its immune system will be able to resist
disease.

Science has now established that a wide array of chemicals can
disrupt these genetically based messages without damaging the
genes themselves. Much attention has focused on disruption of
hormonal signalling, which has become known as endocrine
disruption.

The roots of research in this arena go back to the 1930s, but it
has burgeoned in the last ten years because of very significant
investments of funds by European, Japanese and North American
governments. New results are published virtually every week.
These new findings are rich in detail, fascinating in what they
reveal about biological mechanisms, and sometimes breathtaking in
their implications.

For example, a study published in July 2001 by the United States
Centers for Disease Control reported a strong relationship
between DDT contamination in mothers and the likelihood of
pre-term birth of their infants.[1] Using biological samples
stored since the 1960s, the authors report that their findings
indicate that the United States experienced an epidemic of
pre-term birth during the hey-day of DDT use, and that this
persistent pollutant may have caused up to 15 per cent of infant
mortality in America during that period.

Several important broad trends in the pattern of research
findings can be identified from the thousands of studies on
endocrine disruption published since the early 1990s.

First, the research confirms that contamination by hormonally
active compounds is globally ubiquitous. No one is unexposed,
even in the womb. The same is true for most, if not all living
organisms, especially those higher in ecological food chains and
thus consuming foods in which the contaminants have become
concentrated by bioaccumulation. Contamination is partly so
widespread because of the global redistribution of pollutants
transported through air and water. The inadvertent but pervasive
inclusion of hormonally active compounds in consumer products
such as many cosmetics and plastics also contributes.

Empirical confirmation

Second, effects of exposure can be observed at levels
dramatically lower than those thought relevant to health a decade
ago. Scientists are measuring the endocrine-disruption impacts of
contaminants like arsenic, dioxin and bisphenol A (a basic
component of polycarbonate plastic) in the low parts-per-billion.
This was unmeasurable two decades ago (scientific instruments
simply were not that accurate) and highly controversial until
recent review and empirical confirmation.

Third, the findings indicate that virtually all chemical
messaging systems are vulnerable, in principle, to message
disruption. Work in this area focused for decades on interference
with oestrogen. As the focus has expanded to other hormones, one
or more disrupting contaminants have been discovered for every
system studied carefully, including the thyroid system (crucial
for brain development), the retinoid system (involved in very
basic control of development), and the glucocorticoids (important
for metabolism and tumour suppression, among other things). In
the summer of 2001, new results reinforced this trend
dramatically, with a report that the ecological symbiosis between
leguminaceous plants like beans and the bacteria responsible for
nitrogen fixation is vulnerable to disruption by contaminants.[2]
This symbiosis, mediated by chemical communication between the
plant and the bacteria, is a vital component of the global
nitrogen cycle.

Fourth, the health effects of concern have expanded dramatically
beyond those of the traditional focus for toxicology. Laboratory
studies unequivocally demonstrate effects on disease resistance,
cognitive function and fertility resulting from low-level
exposures.

These findings should be of deep concern to people, organizations
and agencies focused on human economic development and equity. It
is clear, for example, that background levels of contamination
can make children less resistant to infectious agents. Further
research in this area may force a radical reassessment of the
toll of contamination, as this implies that many deaths and
diseases would have been avoided had contaminants not reduced
resistance.

Similarly, the research suggests that widespread exposure to
neurologically active contaminants as might occur, for example,
in agricultural areas in the developing world with intensive
pesticide use may lead to community-wide erosion of cognitive
abilities. In a world in which information is a key economic
currency, this contamination burden could consign those affected
to the economic margins forever. ab Conceptual shifts

These emerging trends are forcing toxicologists toward several
conceptual shifts that will lead to fundamental changes in the
ways that chemicals are managed. The most important of these
involves a change in the way that toxicologists think about what
is relevant to human health.

Traditional toxicology focuses on damage, such as cell death,
mutations, cancer or genotoxicity. Message disruption can cause
these, but the effects may also be of a very different, but
equally important, nature. Most challenging to traditional
toxicology, message disruption does not work by overwhelming the
body's (or the cell's) defences. It works by hijacking the
developmental process, adding to or subtracting from the body's
own control mechanisms at remarkably low levels of exposure. By
subtly (or blatantly) altering the path of development, message
disruption leads the victim to a different future. The difference
may be small, as in the loss of a few IQ points, or it may be
large, as in a completely dysfunctional immune system.

Toxicology has focused traditionally on the impact of high levels
of exposure on small numbers of people. This new approach
requires considering widespread, low-level exposures experienced
by many people -- exposure levels that many had come to write-off
as "background" and, by implication, irrelevant.

Taken together, these new scientific findings add to growing
pressure to change the basic rules of chemical regulation. Once
again, we have been blind-sided. Our ability to synthesize
chemicals got far ahead of our scientific understanding of their
impacts.

Traditional risk assessment allowed them to be commercialized and
distributed, causing pervasive contamination. Risk assessment's
partner in developing protective standards, epidemiology, by
definition works only after an epidemic. Even then, its tools are
remarkably insensitive in studies of the effects of endocrine
disruption, and strongly biased toward negative results even when
there are real effects.

The answer, still imperfect, lies in implementing precautionary
measures that impose far more stringent requirements on old and
new products alike. As the Swedish Chemicals Policy Committee has
recognized, certain attributes should be knock-out criteria.[3]
Persistent bioaccumulative compounds, for example should be
eliminated from use even without demonstrating toxicological
risk. Endocrine-disrupting materials should be removed from
consumer products and their environmental release should be
phased out. More generally, the demonstration of potentially
harmful biological impacts in laboratory studies should reverse
the burden of proof in developing regulations from one in which
harm must be demonstrated before a product is withdrawn, to an
approach where safety is ensured beyond reasonable doubt before
widespread deployment is allowed. These steps will help ensure
that the benefits we all enjoy from modern chemistry do not come
back to haunt us. -- Peter Montague

======

* John Peterson Myers, co-author of OUR STOLEN FUTURE (hard
cover: Dutton, 1996; ISBN 0525939822; paperback: Plume, 1997;
ISBN 0452274141), is Senior Advisor to the United Nations
Foundation and Senior Fellow, Commonweal.

[1] M.P. Longnecker, M.A. Klebanoff, H. Zhou, J.W. Brock,
"Association between maternal serum concentration of the DDT
metabolite DDE and preterm and small-for-gestational-age babies
at birth, " THE LANCET Vol. 358 (2001), pgs. 110-114.

[2] J.E. Fox, M. Starcevic, K.Y. Kow, M.E. Burow and J.A.
McLachlan, "Nitrogen fixation: Endocrine disrupters and flavonoid
signalling," NATURE Vol. 413 (2001), pgs. 128-129.

[3] Swedish chemicals policy recommendations were reported in
Lotta Fredholm, "Chemical Testing: Sweden to Get Tough on
Lingering Compounds," SCIENCE Vol. 290, No. 5497 (Dec. 1, 2000),
pgs. 1663-1666.