Chelated lead in relation to lead in bone and ALAD genotype

In order to assess whether lead in bone is available for chelation by 2,3 m eso-dimercaptosuccinic acid (DMSA), 21 workers (10 active and 11 retired) f rom a secondary lead smeltery were studied. A morning urine sample was obta ined from all participants, followed by ingestion of 10 mg per kg body weig ht of the chelating agent DMSA. All urine produced during the following 24 h was collected in consecutive 6- and 18-h portions. Concentrations of lead in blood (B-Pb) and urine were determined by flameless atomic absorption s pectrometry (AAS), in plasma (P-Pb) by inductively coupled plasma mass spec trometry (ICP-MS), and in finger bone (Bone-Pb) by K X-ray fluorescence tec hnique (XRF), DMSA-chelatable lead excreted in the 24-h portion correlated well with the excretion in the 6-h portion (U-Pb-6h; r(s) = 0.95; P < 0.001 ), U-Pb-6h showed a nonlinear relationship to B-Pb (r(s) = 0.84; P < 0.001) and linear relationships to P-Pb (r(s) = 0.91; P < 0.001) and lead in morn ing urine (r(s) = 0.95; P < 0.001). In active workers, but not in retired o nes, P-Pb and U-Pb-6h showed some relationship to Bone-Ph. In alternative m ultiple regression models B-Pb or P-Pb were both significant predictors of U-Pb-6h, while Bone-Pb did not significantly improve the models. It can, th us, be concluded that DMSA-chelatable lead mainly reflects lead concentrati ons in blood, soft tissues, and possibly also trabecular bone. It is not a good index of total body burden and long-term exposure. For such estimation s cortical Bone-Pb is more valid, as it contains the major fraction of long -term accumulated lead in the body. Further, the mobilization test did not give better information than measurements of lead levels in blood, plasma, or urine without chelation. (C) 1999 Academic Press.