Cortical bone, lead distribution

Children absorb lead from the diet with greater efficiency than adults (WHO, 2000). After absorption and distribution in blood, where most lead is found in erythrocytes, it is initially distributed to soft tissues throughout the body. Subsequently, lead is deposited in the bone, where it eventual accumulates. The half-life of lead in blood and other soft tissues is 28-36 days. Lead that is deposited in physiologically inactive cortical bones may persist for decades without substantially influencing the concentrations of lead in blood and other tissues. On the other hand, lead that is accumulated early in life may be released later when bone resorption is increased, e.g., as result of calcium deficiency or osteoporosis. Lead that is deposited in physiologically active trabecular bones is in equilibrium with blood. The accumulation of high concentrations of lead in blood when exposure is reduced may be due to the ability of bones to store and release lead. 

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