CHEMICALS AND THE BRAIN, PART 1 .

[Guest guest]

CHEMICALS AND THE BRAIN, PART 1 .

JoAnn Guest

Oct 21, 2004 09:43 PDT

 

RACHEL'S ENVIRONMENT & HEALTH WEEKLY #499 .

http://www.monitor.net/rachel/r499.html .

 

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CHEMICALS AND THE BRAIN, PART 1 .

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CHEMICALS AND THE BRAIN, PART 1

 

 

An international group of scientists and physicians --including U.S.

government scientists --issued a consensus statement May 30,

996, expressing great concern about the effects of

hormone-disrupting chemicals on the brain and central nervous

system. The new statement resulted from a workshop Nov. 5-10,

1995 at Erice, Italy. Therefore, we will refer to this as the

Erice Statement.

 

 

 

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 not easy reading, but it is important, so we present

it verbatim.

 

 

 

The Erice Statement begins with a paragraph labeled " background, "

which says, in part:

 

 

 

Research since 1991 has reinforced concerns over the scope of the

 

problems posed to human health and ecological systems by

 

endocrine-disrupting [hormone-disrupting] chemicals. New

 

evidence is especially worrisome because it underscores the

 

exquisite sensitivity of the developing nervous system to

 

chemical perturbations [disturbances] that result in functional

 

abnormalities. Moreover, the consequences of these perturbations

 

depend upon the stage of development during which exposure occurs

 

and are expressed in different ways at different times in life,

 

from birth through to advanced age. This work session was

 

convened because of the growing concern that failure to confront

 

the problem could have major economic and societal implications.

 

 

 

CONSENSUS STATEMENT

 

 

 

The following consensus was reached by participants at the

 

[Erice] workshop.

 

 

 

1. We are certain of the following:

 

 

 

** Endocrine-disrupting chemicals can undermine neurological and

 

behavioral development and subsequent potential of individuals

 

exposed in the womb or, in fish, amphibians, reptiles, and birds,

 

the egg. This loss of potential in humans and wildlife is

 

expressed as behavioral and physical abnormalities. It may be

 

expressed as reduced intellectual capacity and social

 

adaptability, as impaired responsiveness to environmental

 

demands, or in a variety of other functional guises. Widespread

 

loss of this in nature can change the character of human

 

societies or destabilize wildlife populations. Because profound

 

economic and social consequences emerge from small shifts in

 

functional potential at the population level, it is imperative to

 

monitor levels of contaminants in humans, animals, and the

 

environment that are associated with disruption of the nervous

 

and endocrine systems and reduce their production and release.

 

 

 

** Because the endocrine system is sensitive to perturbation, it

 

is a likely target for disturbance. In contrast to natural

 

hormones found in animals and plants, some of the components and

 

by-products of many manufactured organic compounds that interfere

 

with the endocrine system are persistent and undergo

 

biomagnification in the food web, which makes them of greater

 

concern as endocrine disruptors.

 

 

 

** Man-made endocrine-disrupting chemicals range across all

 

continents and oceans. They are found in native populations from

 

the Arctic to the tropics, and, because of their persistence in

 

the body, can be passed from generation to generation. The

 

seriousness of the problems is exacerbated by the extremely low

 

levels of hormones produced naturally by the endocrine system

 

which are needed to modulate [change] and induce [cause]

 

appropriate responses. In contrast, many endocrine disrupting

 

contaminants, even if less potent than the natural products, are

 

presented in living tissue at concentrations millions of times

 

higher than the natural hormones. Wildlife, laboratory animals,

 

and humans exhibit adverse health effects at contemporary

 

environmental concentrations of man-made chemicals that act as

 

endocrine disruptors. New technology has revealed that some

 

man-made chemicals are present in tissue at concentrations

 

previously not possible to measure with conventional analytical

 

methods, but at concentrations which are biologically active.

 

 

 

** Gestational exposure to persistent man-made chemicals reflects

 

the lifetime of exposure of females before they become pregnant.

 

[Gestation is the period of development, from conception through

 

birth; in the case of eggs, it is the incubation period.] Hence,

 

the transfer of contaminants to the developing embryo and fetus

 

during pregnancy and to the newborn during lactation is not

 

simply a function of recent maternal exposure. For some

 

egg-laying species, the body-burden of the females just prior to

 

ovulation [egg production] is the most critical period. For

 

mammals, exposure to endocrine disruptors occurs during all of

 

prenatal and early postnatal development because they are stored

 

in the mother.

 

 

 

** The developing brain exhibits specific and often narrow

 

windows during which exposure to endocrine disruptors can produce

 

permanent changes in its structure and function. The timing of

 

exposure is crucial during early developmental stages,

 

particularly during fetal development when a fixed sequence of

 

structural change is occurring and before protective mechanisms

 

have developed. A variety of chemical challenges [exposures] in

 

humans and animals early in life can lead to profound and

 

irreversible abnormalities in brain development at exposure

 

levels that do not produce permanent effects in adults.

 

 

 

** Thyroid hormones are essential for normal brain functions

 

throughout life. Interference with thyroid hormone function

 

during development leads to abnormalities in brain and behavioral

 

development. The eventual results of moderate to severe

 

alterations of thyroid hormone concentrations, particularly

 

during fetal life, are motor dysfunction of varying severity

 

including cerebral palsy, mental retardation, learning

 

disability, attention deficit hyperactivity disorder,

 

hydrocephalus, seizures and other permanent neurological

 

abnormalities. Similarly, exposure to man-made chemicals during

 

early development can impair motor function [ability to move],

 

spatial perception, learning, memory, auditory development, fine

 

motor coordination [for example, coordinating movement of the

 

hands and eyes], balance, and attentional processes; in severe

 

cases, mental retardation may result.

 

 

 

** Sexual development of the brain is under the influence of

 

estrogenic (female) and androgenic (male) hormones. Not all

 

endocrine disruptors are estrogenic or anti-estrogenic. For

 

example, new data reveal that DDE, a breakdown product of DDT,

 

found in almost all living tissue, is an anti-androgen in

 

mammals. Man-made chemicals that interfere with sex hormones

 

have the potential to disturb normal brain sexual development.

 

Wildlife studies of gulls, terns, fishes, whales, porpoises,

 

alligators and turtles link environmental contaminants with

 

disturbances in sex hormone production and/or action. These

 

effects have been associated with exposure to sewage and

 

industrial effluents, pesticides, ambient ocean and freshwater

 

contamination, and the aquatic food web.

 

 

 

** Commonalties across species in the hormonal mechanisms

 

controlling brain development and function mean that adverse

 

effects observed in wildlife and in laboratory animals may also

 

occur in humans, although specific effects may differ from

 

species to species. Most important, the same man-made chemicals

 

that have shown these effects in mechanistic studies in

 

laboratory animals also have a high exposure potential for humans.

 

 

 

** The full range of substances interfering with natural

 

endocrine modulation of neural and behavioral development cannot

 

be entirely defined at present. However, compounds shown to have

 

endocrine effects include dioxins, PCBs, phenolics, phthalates,

 

and many pesticides. Any compounds mimicking or antagonizing

 

actions of, or altering levels of, neurotransmitters, hormones,

 

and growth factors in the developing brain are potentially in

 

this group.

 

 

 

[The Erice Statement continues; we will present the remainder in

 

a future issue of REHW.]

 

--Peter Montague

 

(National Writers Union, UAW Local 1981/AFL-CIO)

 

===============

 

[1] The Erice Statement was signed by: Dr. Enrico Alleva (Head,

 

Section of Behavioral Pathophysiology; Institute of Neurobiology;

 

Rome, Italy); Dr. John Brock (Chief -PCBs and Pesticides

 

Laboratory; Center for Environmental Health; Centers for Disease

 

Control; Atlanta, Georgia); Dr. Abraham Brouwer (Associate

 

Professor and Toxicology and Research Coordinator; Department of

 

Toxicology; Agricultural University; Wageningen, The

 

Netherlands); Dr. Theo Colborn (Senior Program Scientist;

 

Wildlife and Contaminants Project; World Wildlife Fund;

 

Washington, D.C. Dr. M. Cristina Fossi (Professor, Department

 

of Environmental Biology; University of Siena; Siena, Italy); Dr.

 

Earl Gray (Section Chief; Developmental and Reproductive

 

Toxicology Section; U.S. Environmental Protection Agency [EPA]

 

Research Triangle Park, North Carolina); Dr. Louis Guillette

 

(Professor; Department of Zoology; University of Florida;

 

Gainesville, Florida); Peter Hauser, M.D. (Chief of Psychiatry

 

Service [116A]; Baltimore Veterans Administration Medical Center;

 

10 North Greene Street; Baltimore, Maryland); Dr. John

 

Leatherland (Professor, Chair; Department of Biomedical Sciences;

 

Ontario Veterinary College; University of Guelph; Guelph,

 

Ontario, Canada); Dr. Neil MacLusky (Professor; Director of Basic

 

Research; Division of Reproductive Science; Toronto Hospital;

 

Toronto, Ontario, Canada); Dr. Antonio Mutti (Professor;

 

Laboratory of Industrial Toxicology; University of Parma Medical

 

School; Parma, Italy); Dr. Paola Palanza (Researcher; Department

 

of Biology and Physiology; University of Parma; Parma, Italy);

 

Dr. Susan Porterfield (Associate Professor and Associate Dean of

 

Curriculum; Medical College of Georgia; Augusta, Georgia); Dr.

 

Risto Santti (Associate Professor; Department of Anatomy;

 

Institute of Biomedicine; University of Turku; Turku, Finland);

 

Dr. Stuart A. Stein (Associate Professor of Neurology, Medicine,

 

Pediatrics, OB-GYN, and Molecular and Cellular Pharmacology;

 

University of Miami School of Medicine; Miami, Florida; and Chief

 

of Neurology Children's Hospital of Orange County, Orange,

 

California); Dr. Frederick vom Saal (Professor; Division of

 

Biological Sciences, University of Missouri; Columbia, Missouri);

 

Dr. Bernard Weiss (Professor, Department of Environmental

 

Medicine; University of Rochester School of Medicine and

 

Dentistry; Rochester, New York).

 

 

 

Descriptor terms: hormones; endocrine disrupters; brain; central

 

nervous system; erice statement; wildlife; human health; thyroid;

 

cerebral palsy; mental retardation; learning disability;

 

attention deficit hyperactivity disorder; hydrocephalus;

 

seizures; sexual development; estrogen; androgen; sewage;

 

pesticides; pcbs; phenolics; phthalates;

 

 

 

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_________________

 

JoAnn Guest

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