Lead in Fingerbone: A Tool for Retrospective Exposure Assessment

Abstract

Exposure to inorganic lead may cause many adverse health effects. When absorbed, lead is accumulated in large part in bone. In this study, we investigated the relationship between lead concentration in fingerbone, exposure time, and lead in blood. We also sought to design a model that made it possible to use fingerbone lead as an indicator of earlier exposure. The study comprised 137 active workers from a secondary lead smeltery. Workers had undergone regular determinations of blood lead (i.e., up to 6 times/y) for up to 24 y. In addition, during the period 1979–1992, workers underwent up to four fingerbone lead assessments via noninvasive x-ray fluorescence. We calculated cumulative blood lead, adjusted for time-related reduction of bone lead according to a transfer of lead from bone to blood, for each worker. We obtained the best fit of bone lead to cumulative adjusted blood lead when we assumed a 14-y half-time for the transfer coefficient. This half-time was similar to the terminal half-time for lead in bone in retired smelters, whom we studied earlier by longitudinal in vivo measurements. We described models for the accumulation of bone lead on blood lead and exposure time. The combined data on bone lead and exposure time may be used to estimate a mean blood lead during previous exposure. Such estimates will be valuable in epidemiological studies aimed at evaluating the toxic effects of long-term lead exposure in lead workers for whom data on previous blood lead levels are lacking.