Long-Term Lead Exposure Linked to Heart Deaths
TUESDAY Sept. 8, 2009 -- Exposure to lead over a lifetime may increase the risk of dying from heart disease, new research shows.
Researchers analyzed lead concentrations in the blood and bones of 868 mostly white men from the Boston area who participated in a veterans' aging study.
The men, whose average age was 67 at the start of the study, had lead concentrations in their blood and the bones of the patella (kneecap) and tibia (shin) measured over a nine-year period. During the course of the study, 241 died.
Researchers found that men who had the highest concentrations of lead in their bones had a six times greater chance of dying from cardiovascular disease than men with the lowest concentrations.
Men with the highest levels of lead had a 2.5 times greater chance of dying from all causes than men with the lowest levels.
"Cumulative exposure to lead, even in an era when current exposures are low, represents an important predictor of cardiovascular death," said study author Marc Weisskopf, an assistant professor of environmental health and epidemiology at the Harvard School of Public Health in Boston. "The findings with bone lead are dramatic. It is the first time we have had a biomarker of cumulative exposure to lead, and the strong findings suggest that it is a more critical biomarker than blood lead."
The study appears in the Sept. 8 issue of Circulation.
Typically, lead exposure is measured through blood samples. For instance, the Occupational Safety and Health Administration (OSHA) and the National Health and Nutrition Examination Surveys use blood to measure lead.
But blood, because it has a half life of about 30 days, reveals recent exposure. To determine cumulative exposure, bone is the better method, according to the study.
Bone has a half life ranging from years to decades, including eight years in the knee cap and possibly decades in the shin. To determine bone lead concentration, researchers used a technique similar to a chest X-ray.
Researchers said the link to cardiovascular disease underscores the need for regulatory bodies and surveillance agencies to track potential sources of lead exposure.
"Researchers studying cardiovascular deaths worldwide have generally not considered lead as one of the risk factors that contributes to the risk of death from cardiovascular disease," Weisskopf said.
Overall, study participants had blood levels of lead that were slightly higher than the average of similar U.S. men.
While few if any participants in the study were occupationally exposed to lead, occupations such as construction and painting put men at higher risk.
The current OSHA standards, which are based on blood lead levels and permit up to 40 micrograms of lead per deciliter, are probably inadequate, Weisskopf said.
Before being banned in the mid-1990s, leaded gasoline was a major source of U.S. environmental lead exposure.
Current sources of exposure are chipping, flaking lead in paint in older homes, water pipes in older homes, lead in food and drinking water and hobbies that involve casting ammunition, toy soldiers, fishing weights, lead in solder for making stained glass and some ceramic glazes.
Posted: September 2009