Science & Technology: Risks From Occupational Lead Exposure Last a Lifetime, Pitt Study Finds

Issue Date: 
June 9, 2008

Combination of age and early exposure to lead significantly increases risk

Older workers with past occupational exposure to lead face increased risk for recirculation of lead into their bloodstreams later in life, according to a study by University of Pittsburgh researchers published in the current issue of Archives of Environmental and Occupational Health.

“The neurotoxic effects of lead have been documented for over a century,” noted lead author Lisa A. Morrow, a Pitt psychiatry and psychology professor. “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 constituting safe exposure have continued to be lowered 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.

The Pitt researchers studied 58 men with prior workplace exposure to lead. The study group ranged in age from 40 to 76 and had not worked with lead, on average, for the preceding 10 years. The workers were then divided by age into three groups. Correlations between blood lead and bone lead were highest in the older age groups, 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. Recent studies have shown impairment in both children and adults at concentrations previously thought to be safe,” said Morrow. “Lead attacks many systems in the body. 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.”

Coauthors of the study include Herbert Needleman, professor of psychiatry and pediatrics in the Pitt School of Medicine; research associates Christine McFarland, in the Pitt psychiatry department, and Kim Metheny, in the Pitt neurology department; and biotechnology consultant Michael Tobin.

Funding from the National Institute for Occupational Safety and Health supported the research.