"The neurotoxic effects of lead have been documented for over a century," said Lisa Morrow, Ph.D., lead author and associate professor of psychiatry and psychology at the Western Psychiatric Institute and Clinic of University of Pittsburgh Medical Center. "Our study found that even workers with no current workplace exposure to lead – but who have had considerable past exposure – show increasing levels of lead in their blood as they age."
While state and federal standards that constitute safe exposure have lowered limits over the last decade or so, lead exposure continues to be widespread in the United States, with more than 1.4 million industrial workers having potential lead exposure.
Previous studies have shown that the amount of lead in the body increases throughout the life span, with 90 to 95 percent of that lead stored in the bones. With aging, bones demineralize and stored lead can be recirculated into the bloodstream.
Morrow's team studied 58 men, ranging from 40 to 76, with prior workplace exposure to lead. On average, none had worked with lead for the preceding 10 years. The older workers had the highest lead levels, meaning the combination of age and bone lead significantly predicted an increase in current blood lead levels. This suggests that lead from the bones is an important source of lead circulating in the blood. Older workers with prior exposure to lead may therefore face an additional neurotoxic hazard long after exposure has ended.
"Lead is a powerful neurotoxin that affects people of all ages,” Morrow said. “The most important target is the central nervous system. Increased measures to prevent exposure will be necessary to achieve the optimal goal of zero blood lead in the U.S. in the next decade.”
Morrow's study was supported by funding provided by the National Institute for Occupational Safety and Health.