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September 20, 2006

Environmental Lead Levels Related to Increased Death

Blood lead levels currently thought to be safe by the U.S. government, the World Health Organization and many other authorities are associated with an increased risk of heart attack and stroke, according to researchers from the Johns Hopkins Bloomberg School of Public Health and Tulane University. Study results demonstrate that environmental lead exposure remains a major public health problem in the United States. The study was published today in the online version of Circulation: Journal of the American Heart Association.

The researchers evaluated the association between blood lead levels and mortality in 13,946 adult study participants, who were part of the Third National Health and Nutrition Examination Survey. Initially recruited in 1988-1994, they were followed for up to 12 years. The mean blood lead level of the study participants was 2.58 µg/dL, which is well below levels currently considered safe by the U.S. government. Blood lead levels above 2 µg/dL were associated with an increased risk of heart attack and stroke mortality.

“We saw an increased risk of death from all causes and cardiovascular death in all sub-groups—non-Hispanic whites, non-Hispanic blacks and Mexican Americans,” said Eliseo Guallar, MD, DrPH, co-author of the study and an associate professor in the Bloomberg School of Public Health’s Department of Epidemiology.

Exposure of the U.S. population continues to come from old lead-based paint and the residues of automobile emissions from the decades of lead use in gasoline; the residues remain in dusts and soil. Some adults may also be exposed in their place of work. Drinking water can also be a source of lead exposure due to the presence of lead pipes and solders. Unsafe consumer products, such as folk medicines, cosmetics and toys, may also contain lead.

The U.S. Occupational Safety and Health Administration defines high blood lead in adults as higher than 40 µg/dL. The Centers for Disease Control and Prevention recommend that women of childbearing age keep blood lead levels below 10 µg/dL.

“In our data, the association of blood lead with cardiovascular mortality was evident at levels as low as 2 µg/dL. As 38 percent of U.S. adults had lead levels above 2 µg/dL, the public health implications of these findings are substantial,” said Paul Muntner, PhD, corresponding author of the study and an associate professor at Tulane University’s School of Public Health and Tropical Medicine.

“Blood lead below 0.48 µmol/L (10 µg/dL) and mortality among U.S. adults” was co-authored by Andy Menke, Paul Muntner, Vecihi Batuman, Ellen K. Silbergeld and Eliseo Guallar.

The study was supported by a National Institutes of Health grant from the COBRE Program of the National Center for Research Resources.

Public Affairs media contacts for the Johns Hopkins Bloomberg School of Public Health: Kenna Lowe or Tim Parsons at 410-955-6878 or paffairs@jhsph.edu.