Chelatable lead versus lead in human trabecular and compact bone.

In active and retired lead workers there was a close correlation between urinary excretion of lead during 6 h after intake of a single oral dose of 0.5 g penicillamine, and the excretion during 24 h. In chelation tests it is thus sufficient to collect urine for only a few hours. There was a close correlation between the amount of chelatable lead and the blood-lead level, as well as the lead level in biopsies of trabecular bone from vertebrae, but there was no association with lead in compact bone, as measured in finger-bone by in vivo X-ray fluorescence. The chelatable lead probably mainly reflects the soft tissue lead pool and a fraction of the trabecular bone lead pool, which has a relatively rapid turnover. It is not a valid indicator of the pool of lead which has slowly accumulated in the compact bone, and it is thus not useful as a time-integrated index of the exposure over a long period of time.