In vivo X-ray fluorescence (XRF) analysis of lead in finger bone; extended lead exposure range

Abstract: This work shows a contribution to a long-term study of lead in smelter workers where the objectives were to assess the historical lead (Pb) exposure and to study the relationships between lead concentrations in finger bone (Bone-Pb), whole blood (B-Pb), plasma (P-Pb), urine (U-Pb) and the duration of employment in workers at a secondary lead smelter. Moreover, results were compared with previous studies of populations with a wide range of lead exposure.In 39 workers (29 active, 10 retired), recruited from those with the highest lead exposure at a German secondary lead smelter, levels of Bone-Pb was determined by the Malmö in vivo X-ray fluorescence (XRF) technique. The setup uses two 57Co sources (-energy 122 and 136 keV) to generate photoelectric absorption in the K-shell of finger bone lead atoms (binding energy 88.005 keV). A high purity germanium (HPGe) detector detects subsequent characteristic lead X-rays and a large background from mainly incoherently scattered photons. The net number of registered characteristic pulses, in relation to phantom measurements and bone size, gives the Bone-Pb of the measured subject. The Department of Occupational and Environmental Medicine in Lund determined B-Pb, P-Pb and U-Pb by inductively coupled plasma mass spectrometry (ICP-MS). Results were compared with data from a similar previous study on workers with lower exposure, from a Swedish secondary lead smelter.The median values in the active/retired German lead workers were: age 44/59 years, duration of employment 20/38 years and Bone-Pb 71/150 µg/g. Bone-Pb increased with duration of employment by 4.2 µg/g per year for German workers and by 1.6 µg/g per year for Swedish workers. The median Bone-Pb was three times higher in both active and retired German workers than in Swedish smelter workers with essentially the same age distribution and duration of employment.In this work the in vivo XRF technique is being demonstrated as a valuable and manageable instrument when contributing to a larger collaborative study of lead. The high Bone-Pb values recorded for the German smelters implied a historical lead exposure of considerable magnitude. A long-term high lead exposure was also revealed in the B-Pb levels for both active and retired workers, which should be leading to the implementation of necessary industrial safety measures in order to respond to biological threshold limits.