Past occupational exposure to lead: association between current blood lead and bone lead.

Mobilization of lead from bone is known to increase with age. The authors performed the current study to determine whether there was an association between current blood lead and bone lead in workers with no current exposure but with significant past workplace exposure. The authors assessed 58 men, aged 40 to 76 years, who had earlier exposure to lead and determined both current blood lead levels and bone lead levels. At the time of the current assessment, the average blood lead level was 10.9 microg/dL and tibia bone lead concentrations ranged from -12.5 to 223.3. The authors divided workers into 3 groups by age (40-49, 50-59, and 60-76). Correlations between blood lead and bone lead were highest in the 2 oldest age groups (.49 and .75, respectively). Hierarchical regression analysis was significant for an interaction between bone lead and age in predicting blood lead (the combination of age and bone lead significantly predicted an increase in current blood lead levels). The results support the hypothesis that lead stored in bone is a significant source of blood lead later in life. Older workers with past occupational exposure may face a particular risk for recirculation of lead in blood with advancing age.