PARTITION OF CIRCULATING LEAD BETWEEN SERUM AND RED-CELLS IS DIFFERENT FOR INTERNAL AND EXTERNAL SOURCES OF LEAD

Serum lead, whole blood lead and lead in both tibia and calcaneus were measured in each of 49 active lead workers. Serum lead correlated mor e strongly with both in vivo bone lead measurements than did whole blo od lead. The ratio of serum lead to whole blood lend varied from 0.8% to 2.5% and showed a positive correlation with tibia, and an evert str onger correlation with calcaneus lead. This implies that lead released from bone (endogenous exposure) results in a higher proportion of who le blood lead being in serum than is the case for exogenous exposure. This observation needs to be confirmed, and the relationships amongst the parameters must be studied further, particularly in former or reti red lead workers. If confirmed since at least a portion of lead in ser um is readily diffusible and thus toxicologically more immediately sig nificant than lend bound so red cells, the health implications of endo genous exposure may have to be reassessed. (C) 1996 Wiley-Liss, Inc.