Lead Poisoning

Lead poisoning has been termed the "stealth disease" because of the way it occurs and the devastating neurologic 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 the Bronx, 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."

The difficulty of detecting lead poisoning means that blood lead levels are used to identify children with dangerous amounts of lead. In October, 1991, concluding a lengthy study, the federal government's Centers for Disease Control (CDC) redefined toxicity as blood lead levels at or above 10 micrograms per deciliter (mg/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 mg/dL.

Many experts believe that when a child's blood lead level exceeds 10 mg/dL, there is a high probability of permanent neurological damage. Even at these relatively low exposures, 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. For example, lead interferes with bone formation by blocking absorption of calcium, which affects memory storage and the differentiation of cells in the nervous system. Lead is stored in the bone, matrix, and in pregnant women, this lead can be passed on to the unborn child.

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, causes decrease in muscle strength and at high doses, the syndromes of the wrist-drop and the foot-drop.

Lead accumulates in the kidneys, causing kidney disease and having far-reaching endocrinologic effects. There is a major impact on the enzymatic functions of the liver and on the immune system function of the spleen. It results in 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.