Medical Effects of Lead Poisoning
Lead poisoning has been termed the "stealth disease" because
of the way it occurs and the devastating neurological damage
it causes in children at doses that do not cause outward physical
signs of poisoning. Poisoning occurs when children eat tiny paint
chips or inhale harmful leaded dust. Chalking lead paint creates
dust that settles on toys and other objects. The dust is ingested
by the young child in normal hand-to-mouth activity. Leaded house
dust that is inhaled even in the smallest amounts is just as
lethal as that which is ingested. One paint chip the size of
a thumbnail, ingested by a young child, can cause permanent brain
damage.
Dr. John Rosen, a pediatrician responsible for treating lead
poisoned children at Montefiore Medical Center in New York states: "Lead
at remarkably low concentrations has the unique capability of
robbing kids of such skills as reading, writing, concentration
and abstract thinking. The set of things that are required for
academic success and employment success can be lost forever,
and all of that comes at a remarkable societal cost."
Because there are no initial symptoms from lead poisoning, blood
lead levels are used to identify children with dangerous amounts
of lead. In October, 1991, concluding a lengthy study, the Centers
for Disease Control (CDC) redefined toxicity as blood lead levels
at or above 10 micrograms per deciliter, (ug/dL), the level at
which some adverse health effects have been observed. No lowest
threshold has been identified for the harmful effects of lead,
although some studies have suggested harmful effects at levels
even lower than 10 ug/dL.
Many experts believe that when a child's blood lead level exceeds
10 ug/dL, there is a high probability of permanent neurological
damage. Even at these relatively low blood levels, decreased
intelligence, short-term memory loss, reading under-achievement,
impairment of visual-motor function, loss of auditory memory,
poor perceptual integration, poor classroom behavior and impaired
reaction time occur in children.
Virtually every part of the body is affected by lead. Lead has
no biological value and competes with metals that are essential
to the body, such as zinc, iron and calcium. Lead interferes
with bone formation by blocking absorption of calcium. This affects
memory storage and the differentiation of cells in the nervous
system.
Lead's effect on the brain results in less ability to store
information and draw upon past information and less ability to
inhibit responses to environmental stimuli. Lead also attacks
the peripheral nervous system, which controls the muscles and
organs outside the brain. It causes a decrease in muscle strength
and at high doses, wrist-drop and foot-drop.
Lead accumulates in the kidneys, causing kidney disease, which
has far-reaching endocrinological effects. There is a major impact
on the enzymatic functions of the liver and on the immune system
function of the spleen. It causes anemia by interfering with
the synthesis of hemoglobin. Lead affects the reproductive functions
of both men and women by interference with enzymes that process
testosterone and other androgens. Lead is stored in the bone
matrix and can be passed on to an unborn child by a pregnant
mother.
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