In children, lead is a special cause for concern. Hyperactivity and learning disorders have been correlated with lead intoxication; children with these problems should be checked. Several studies have shown a relationship between lead levels and learning defects, including daydreaming, being easily frustrated or distracted, a decreased ability to follow instruction or a low persistence in learning, and general excitability and hyperactivity. There is also a recent correlation between sudden infant death syndrome (SIDS) and increased lead levels. This needs further research to implicate lead intoxication as a cause of death.

Amounts leading to toxicity: The average daily intake of lead, as estimated by weveral researchers, ranges from 200-400 mcg. Most of that, 80-90 percent, comes from food or contamination from car exhaust. Average absorption is about 5-10 percent, so most of us should be able to eliminate most of what we get. Actually, with proper function we can excrete many times more lead than that daily.

It is not clear what exposures or body levels of lead will actually produce functional difficulties or specific symptoms; this probably varies from person to person. In measurements of any nutrient or chemical in the body, there is an estimated normal, or reference, range, above which some problems or symptoms may appear. For the level of lead in hair, the reference range of the lab that my office uses is 0-30 ppm. Many authorities set lower levels, perhaps below 15-20 ppm, as a concern; Doctor's Data in Chicago uses 10 ppm. Even lower amounts, especially in children, may be a body burden and interfere with optimum brain and metabolic functions. For whole blood measurements, below .40 ppm is usually considered within the normal range; less than .20 ppm is probably ideal. In children, lower levels than that, even .10 ppm may be a concern.

Who is susceptible? There is a long list (hundreds) of industrial and other workers who have a higher than average potential for exposure to lead. Obviously, anyone who works directly with lead has more exposure. Working in zinc or vanadium mining can also increase lead exposure.

As stated, children are especially at risk for lead toxicity. For instance, teething children