Lead in bone: implications for toxicology during pregnancy and lactation

Advances in understanding the distribution and retention of lead in mineralized tissues are important for two reasons: first, bone lead may be a more accurate dosimeter of integrated absorption associated with chronic exposures, and second, bone lead may be a source of internal exposure to the host organism. Little attention has been paid to this second aspect, the remobilization of lead from bone. Mobilization of lead from bone is likely to occur during periods of altered mineral metabolism; since calciotropic factors determine the uptake and storage of lead in this compartment, changes in calcium-related regulatory factors are likely to affect lead compartmentation. Calcium metabolism changes drastically in humans during pregnancy and lactation; although relatively little is known of lead kinetics during these critical periods, it is likely that bone lead is mobilized and transferred to the more bioavailable compartment of the maternal circulation, with potential toxic effects on the fetus and the mother.