Chemicals and the Brain, Part 2
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. CHEMICALS AND THE BRAIN, PART 2 .
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CHEMICALS AND THE BRAIN, PART 2
(Continued from RACHEL'S #499.)
Here we continue our presentation of the Erice Statement, a
consensus statement issued May 30, 1996, by an international
group of scientists and physicians, including U.S. government
scientists. (The signers were listed and identified in RACHEL'S
#499.) The statement expresses great concern about the effects
of hormone-disrupting chemicals on the brain and central nervous
system. The Erice Statement resulted from a workshop held
November 5-10, 1995 at Erice, Italy.
Hormones are chemical messengers that travel in the blood stream,
turning on and off critical bodily functions to maintain health
and well being. Hormones control growth, development, and
behavior in birds, fish, reptiles, amphibians, and mammals,
including humans. In humans, 100 different hormones have been
identified. Taken together, the tissues and organs that produce,
and respond to, hormones are called the endocrine system. In
1991, an international group of 23 scientists issued a consensus
statement, expressing great concern that many synthetic
(human-created) industrial chemicals can interfere with hormones
in wildlife and humans. (See REHW #263, #264). The 1991
statement focused on the ability of industrial chemicals to
interfere with sexual development and behavior in wildlife and
humans. The Erice Statement issued last month focuses attention
on industrial chemicals that can interfere with the development
of the brain and other parts of the central nervous system. The
statement is definitely not easy reading, but it is important, so
we present it verbatim, with our explanations inside square
brackets [].
CONSENSUS STATEMENT (continued from Rachel's #499)
2. We estimate with confidence that:
** Every pregnant woman in the world has endocrine disruptors in
her body that are transferred to the fetus. She also has
measurable concentrations of endocrine disruptors in her milk
that are transferred to the infant.
** There may not be definable thresholds for responses to
endocrine disruptors [in other words, any amount may cause some
effect]. In addition, for naturally occurring hormones, too much
can be as severe a problem as too little. Consequently, simple
(monotonic) dose-response curves for toxicity do not necessarily
apply to the effects of endocrine disruptors. [See REHW #490.]
** Because certain PCBs and dioxins are known to impair normal
thyroid function, we suspect that they contribute to learning
disabilities, including attention deficit hyperactivity disorder
and perhaps other neurological abnormalities. In addition, many
pesticides affect thyroid function and, therefore, may have
similar consequences.
** Some endocrine disruptors or their breakdown products are
nearly equipotent to [as powerful as] natural hormones. Even
weak endocrine disruptors may exert potent effects because they
can bypass the natural protection of blood binding proteins for
endogenous [natural] hormones. Some disruptors also have a
substantially longer biological half-life than naturally produced
hormones because they are not readily metabolized, and as a
result are stored in the body and accumulate to concentrations of
concern. Some man-made chemicals that appear non-toxic are
converted by the liver to more toxic compounds. Also, compounds
that are not toxic in the mother may be toxic to her developing
embryo, fetus or newborn. The exquisite vulnerability of the
fetal brain to methylmercury and lead are prime examples of this
principle.
** Functional deficits are not as easily measured as physical
anomalies or clinical disease, in part because they are typically
expressed as continuous measures, such as IQ, rather than the
number of cases in a population. Consequently, conventional
population surveys may overlook the extent of such deficits.
Moreover, because such surveys tend to express their findings as
shifts in mean [average] values even when they are based on
appropriate measures, they tend to obscure influences on the more
susceptible members of the population.
** Large amounts of man-made chemicals capable of disrupting the
endocrine and nervous systems are sold to, or produced and used
in, third world countries that lack the resources or technology
to properly monitor and control exposure levels. Insufficient
and improper training in handling chemicals and ignorance
concerning health effects and monitoring strategies leads to the
likelihood of very high levels of exposure.
3. There are many uncertainties in our understanding because:
** No one is exposure-free, thus confounding [confusing] studies
to determine what is normal. Everyone is exposed at any single
time and throughout life to large numbers of man-made chemicals.
Relatively few of the man-made chemicals found in human tissue
have been identified. Lack of funding has seriously constrained
testing these chemicals for their potential to disrupt natural
systems.
** Sensitive parameters, including neurological abnormalities,
behavioral and neuropsychiatric disorders, and neuroanatomical,
neurochemical, and neurophysiologic endpoints need to be
investigated. Most important, criteria at the population level
need to include the social and economic costs of impairment
because the true costs to society of such problems can be
significant, e.g., the costs of a 5 point IQ loss across a
population. Investigation of potential toxicity typically
includes laboratory, population and field studies, clinical
reports, and accident reports. However, developmental
neurotoxicants produce a spectrum of effects that are not
typically evaluated, such as the progression and latency of
behavioral and neurological changes. In addition, alteration of
other systems can produce subsequent cognitive, behavioral, and
neurological dysfunction; i.e. diseases of other organ systems
that influence the brain; non-CNS [central nervous system] drugs;
other foreign substances such as air pollutants; and immune
system involvements that alter behavior.
** Trade secret laws afford industry confidentiality, depriving
the consumer and public health authorities of the right to know
the components of commercial products so they can be tested.
4. Our judgment is that:
** The benefits of reduced health care costs could be substantial
if exposure to endocrine-disrupting chemicals were reduced.
** A trivial amount of governmental resources is devoted to
monitoring environmental chemicals and health effects. The
public is unaware of this and believes that they are adequately
protected. The message that endocrine disruptors are present in
the environment and have the potential to affect many people over
a lifespan has not effectively reached the general public, the
scientific community, regulators, or policy makers. Although
this message is difficult to reduce to simple statements without
over- or under-stating the problem, the potential risks to human
health are so widespread and far-reaching that any policy based
on continued ignorance of the facts would be unconscionable.
** The outcome of exposure is inadequately addressed when based
just on population averages. Instead, risk should be based on
the range of responses within a population --that is, the total
distribution. The magnitude of the problem can be better
determined by knowing the distribution of responses to endocrine
disruptors by individuals within subsets of the population most
at risk, such as pregnant women, developing embryos, fetuses, and
newborns, teens, the aged, the ill or those with pre-existing
endocrine disorders. The magnitude of the risks also depends
upon the endpoint [health effect] under consideration. For
example, a variety of motor, sensory, behavioral, and cognitive
functions, endpoints which are more sensitive than cancer, must
be considered when assessing neurological function. This holds
for wildlife and domestic animals, as well as human populations.
** Wildlife have been effective models for understanding
endocrine disruption at the molecular, cellular, individual,
population, and ecosystem levels. Future research to examine
diverse wildlife species at all levels of biological organization
must be broadened and adequately supported.
** Those responsible for producing man-made chemicals must assure
product safety beyond a reasonable doubt. [See REHW #491.]
Manufacturers should be required to release the names of all
chemicals used in their products with the appropriate evidence
that the products pose no developmental health hazard.
** Current panels of scientists who determine the distribution of
public research funds often have a narrow scope of expertise and
are thus ill-equipped to review the kind of interdisciplinary
research that is necessary in this field. Funding institutions
should be encouraged to increase the scope of representation on
review panels and to develop more appropriate mechanisms for
interdisciplinary reviews. Governmental agencies should also
increase funding for multidisciplinary extramural projects for
surveillance of wildlife and human populations where neurological
damage is suspected and follow any leads with laboratory
research. In addition, populations of animals consuming the
contaminated foods also eaten by humans should be studied for
developmental health effects. It is important to observe a
variety of vertebrate species through multigenerational studies.
** Strategies for increasing interdisciplinary communication and
collaborations to optimize resources and future research are
needed. Studies should be designed more economically to include
the sharing of material among many collaborators.
Interdisciplinary teams should explore neurological and other
types of damage at all levels of biological organization from
molecular through biochemical, physiological, and behavioral.
** A concerted effort should be undertaken to deliver this
consensus statement to the public, key decision makers, and the
media. In addition, specially designed messages should be
developed for family physicians and others responsible for public
health who are often unaware of the possible role of occupational
and environmental chemical pollutants as agents underlying or
constituting risk factors for "primary" human diseases.
Physicians must be trained in medical school about often latent
effects of pollutants on human development and health. This
training is currently inadequate. A coordinated speakers bureau
and on-line systems such as a site on the World Wide Web for
endocrine-disruptors should be established. [End of consensus
statement.]
The consensus statement developed at Erice has been all but
blacked out by the U.S. media. The LOS ANGELES TIMES and the
SACRAMENTO (CAL.) BEE reported it May 31, but other papers
ignored it entirely. Perhaps the statement challenges too many
of our pet assumptions about the safety of our children in this
chemically-altered world.
--Peter Montague
(National Writers Union, UAW Local 1981/AFL-CIO)
Descriptor terms: erice statement; hormone disrupters; hormones;
brain; central nervous system; dose-response; pcbs; dioxin;
attention deficit disorder; add; thyroid; development;
methylmercury; mercury; lead; iq; third world; developing
countries; trade secrecy; risk assessment; wildlife; burden of
proof; right to know;
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--Peter Montague, Editor
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