Lead and Cadmium Levels Not as Safe as Previously Thought

Eliseo Guallar, MD, DrPH

Researchers from the Johns Hopkins Bloomberg School of Public Health have found a link between levels of lead and cadmium -- both toxic and carcinogenic metals -- in the blood and peripheral arterial disease (PAD). The levels of lead and cadmium studied were well below the current U.S. safety standards.

Eliseo Guallar, MD, DrPH, the study’s senior author, explained that the general public can be exposed to lead and cadmium in ambient air near industrial and combustion sources, in certain foods, through smoking and sometimes in drinking water.

Although the cardiovascular effects of chronic exposure to low doses of lead and cadmium are not well understood, past studies have shown that lead exposure is linked to elevated blood pressure and to increased cardiovascular mortality. In this study, Johns Hopkins researchers focused on PAD, a condition characterized by reduced blood flow to the legs due to atherosclerosis. A typical symptom is pain in the legs during activity.

The researchers studied 2,125 adults and found that those with the highest blood concentrations of lead or cadmium were 2.8 times more likely to develop PAD.

In addition, the investigators observed that the odds of developing PAD for current smokers compared to people who never smoked changed from 4.13 to 3.38 after adjusting for blood lead, and to 1.84 after adjusting for blood cadmium. This led Dr. Guallar to speculate that the cadmium contained in cigarette smoke may damage the lining of blood vessels and becomes a major contributor to smoking-related PAD.

Dr. Guallar, an assistant professor in the School’s Department of Epidemiology, said, “We don’t need any more reasons to argue that smoking is bad, but it is important to know what are the mechanisms of the problems associated with smoking. We need to know if there is something about cigarette smoke that makes it more specific to PAD than other vascular diseases.”

“The levels of the toxins found in the study participants were below the current standards, which have been steadily lowered over the past few years. Scientists need to think more carefully about the association between metals and PAD. More experiments with cadmium and lead at lower doses need to be done to determine what exposures might be problematic in terms of risk for cardiovascular disease,” said Dr. Guallar.

“Lead, Cadmium, Smoking and Increased Risk of Peripheral Arterial Disease” was published online on June 8, 2004, and will appear in the June 29, 2004, issue of Circulation, the journal of the American Heart Association.

Ana Navas-Acien, MD, MPH, Elizabeth Selvin, MPH, A. Richey Sharrett, MD, DrPH, Emma Calderon-Aranda, PhD, MD, and Ellen Silbergeld, PhD, co-authored the study.

The study was supported the American Heart Association and the National Heart, Lung and Blood Institute.