It has no biological use in the human body, even in trace amounts. When introduced into the body by ingestion or inhalation, the lead pigments are separated and the body is fooled into accept- accepting them as normal, healthy elements like calcium and iron. The lead pigment then changes form and becomes an improper part of the body's biochemistry, inhibiting the ability of various body organs to perform their normal function. Often cells die and are not replaced, and the entire body deteriorates. Hence a person may suffer initial exposure during childhood, which then may be compounded in adulthood by living in a contaminated residence, working in a hazardous environment, or by eating contaminated food.
Lead paint becomes harmful when inhaled as dust or ingested as paint chips.
Of these two ways, dust is the less obvious, yet more common, mode of poisoning. As our lead-painted architecture ages, the dust problem increases, as does lead exposure. The lead paint which previously covered wood surfaces is now wearing, flaking, and peeling off. The dust of this worn-off paint may be carried into the home by the wind, where it can become imbedded in fabric, in rugs or cracks in floors. Dust may also accumulate on window sills or other such exposed areas.