Eliseo Guallar, M.D., Dr.PH.“Safe” levels of lead and cadmium may raise risk of peripheral artery disease
Even at levels currently considered safe, two metals lead and cadmium may increase the risk of peripheral artery disease, according to research published by Eliseo Guallar, M.D., Dr.PH., an assistant professor of epidemiology at the Johns Hopkins University Bloomberg School of Public Health in Baltimore.
People can be exposed to lead and cadmium through cigarette smoke, in ambient air near industrial and combustion sources, in certain foods and sometimes in drinking water.
In peripheral artery disease (PAD), fatty deposits build up in artery walls and reduce blood circulation, mainly in arteries to the legs and feet. In its early stages, a common symptom is cramping or fatigue in the legs and buttocks during activity. Such cramping subsides when the person stands still. PAD affects 8 to 12 million Americans, according to the AHA.
Funded by the American Heart Association and the National Heart, Lung, and Blood Institute, the study of 2,125 adults found that those with the highest blood concentrations of lead or cadmium were almost three times more likely to develop PAD than those with the lowest levels of the two metals. Yet the highest levels were well within what isconsidered safe,Guallar said. Both metals are well-known toxins, he said, but the levels found in the subjects “are well below the radar screen of current regulations.”
Peripheral artery disease is strongly associated with smoking, which this study confirmed -- the odds of PAD for current smokers compared to people who never smoked was 4.13. The odds were reduced to 3.38 after adjustment for blood lead and to 1.84 after adjustment for blood cadmium. This led Guallar to theorize that the cadmium contained in cigarette smoke may damage the lining of blood vessels and may be a major factor in smoking-associated PAD.
In general, subjects who were older, less educated and smokers had higher levels of both lead and cadmium. Concentrations of both metals were highest in smokers, but smoking was more strongly associated with cadmium, Guallar 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,” he said.
People with the highest cadmium levels were 2.82 times more likely to develop PAD than people with the lowest levels. For those with the highest lead levels, the odds ratio for developing PAD was 2.88 compared to those with the lowest levels.
Subjects with PAD had 13.8 percent higher levels of lead on average than people without PAD, Guallar said. Likewise, the cadmium levels were about 16.1 percent higher in persons with PAD than in those without PAD.
Guallar said that as research has uncovered more information about the true dangers of lead, regulators steadily lowered the threshold for so-called “safe” levels. “A decade ago, what was considered a safe level for lead was much higher than it is today,” he said.
The new finding suggests that epidemiologists as well as basic scientists “need to think more carefully about this association and do more experiments with cadmium and lead at lower doses to determine what exposures [to the metals] might be problematic in terms of risk for cardiovascular disease.”