June 7, 2004 -- Even at levels well within federal limits, exposure to the metals lead and cadmium may dramatically increase the risk of a common form of blood vessel disease.
A new study shows people with the highest blood levels of lead and cadmium were nearly three times as likely to develop peripheral artery disease compared with those with the lowest levels -- although the highest blood levels were still within what is normally considered safe.
Common sources of lead and cadmium exposure include tobacco smoke, coal-fired power plants, lead dusts and soils, incinerators, certain foods (shellfish, liver, and kidney meats), and sometimes drinking water.
According to the American Heart Association, peripheral arterial disease (PAD) affects up to 12 million Americans. It occurs when fatty deposits build up within the arteries and interfere with blood circulation, particularly in arteries located in the legs and feet. It causes pain in the legs, especially with walking, and when severe, can lead to ulcers on the feet or toes and even gangrene.
The levels of lead and cadmium exposure found in the study were "well below the radar screen of current regulations," says researcher Eliseo Guallar, MD, DrPH, of the Johns Hopkins University Bloomberg School of Public Health, in a news release.
Guallar says these findings show that federal officials and health experts "need to think more carefully about this association" between metal exposure and PAD.
Metals Linked to Heart Disease Risks
In the study, which appears in the June 8 issue of Circulation: Journal of the American Heart Association, researchers looked at blood levels of lead and cadmium and peripheral arterial disease in a group of 2,125 adults over 40 years old.
Researchers found those with the highest blood levels of the two metals were nearly three times as likely to have PAD compared with those with the lowest levels.
People with PAD had blood lead levels that were about 14% higher than those who didn't have the condition. Blood cadmium levels were about 16% greater in those with PAD.
The study also showed that smokers were more than four times as likely to have PAD as people who never smoked. Smoking, high cholesterol, high blood pressure, and diabetes increase the risk of developing PAD.
Guallar says lead exposure has declined dramatically since leaded gasoline was banned two decades ago.
The average blood level of lead in the study was 0.10 micromoles per liter -- significantly under the safety standard of 1.93 micromoles per liter set forth by the Occupational Safety and Health Administration (OSHA). The average cadmium level was 4.3 nanomoles per liter -- far below the safety standard of 44.5 nanomoles per liter.
Researchers found people who were older, less educated, and smokers had higher blood levels of both lead and cadmium.