A healthy body depends on individual systems to assure
it serves each of us well: cardiovascular, circulatory,
digestive, endocrine, excretory, lymphatic, muscle, nervous, reproductive,
and skeletal.
However, the nervous system is so important it
could be considered the master control unit inside your
body. It is responsible for sending, receiving, and processing
nerve impulses throughout the body. All the organs and muscles inside
your body rely upon these nerve impulses to function. Cells of the
nervous system, called nerve cells or neurons,
are specialized to carry "messages" through an electrochemical
process. The main organ of the central nervous system is the brain.
The first sign of the developing nervous system can be seen at
about the 16th day of development continuing to grow for a few years
after birth. Every cell is precisely in its place, every link between
neurons carefully organized. Nothing is random, nothing
arbitrary — the unfolding of brain development is like a precisely
choreographed dance.
By the age of 2 years old, the brain is about 80% of the adult
size. The brain continues to develop and change throughout childhood,
adolescence, adulthood, and old age. When a substance interferes
with these clearly-defined dance steps, problems can occur.
All of our bodily systems require chemicals in order to grow and
develop properly. Those chemicals that occur naturally are called
metabolites; those chemicals which are artificially introduced
into our bodies and cause harm are called toxins.
Every day we are exposed to thousands of chemicals,
including hundreds known to cause serious harm to people and the
environment. The National Academy of Sciences reported in 1984 that
15,000 of the chemicals registered for commercial use with the Environmental
Protection Agency had moderate to high potential for human exposure.
Less than half of these had been tested for toxicity at all, and
fewer than 20% had been tested for toxicity in developing
organisms.1
Children are much more susceptible to the risks of exposure
to dangerous environmental toxins than adults because of
their smaller size and closeness to the floor, their increased metabolic
rate, and their hand-to-mouth behavior.
When toxic substances affect the nervous system specifically, they
are identified as being “neurotoxicants.”
Examples of some of the most common neurotoxicant
substances are
1 Commission on Life Sciences, National Academy of Sciences,
Toxicity Testing: Strategies to Determine Needs and Priorities.
National Academy Press, Washington DC 1984.
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