Air Pollution's Other Victim: The Heart

Heart disease and stroke are the number 1 and number 3 killers worldwide. Together, they account for 35 percent of all U.S. deaths, according to the Centers for Disease Control and Prevention. But if you exercise, eat a healthy diet and don't smoke, you are doing all you can to reduce your risk of heart disease—right?

Maybe not. The evidence is mounting about another heart risk that may be harder to avoid: polluted air. In the last issue of The Green Guide, we reported the latest on dirty air's contribution to lung disease and low birth weights. But breathing air choked with particles, nitrogen oxides and other toxins can also increase the risk of dying from heart failure, several large-scale studies reveal. And, surprisingly, air pollution causes more cases of cardiovascular diseases than cases of respiratory diseases, says Joel Kaufman, an environmental-health professor at the University of Washington in Seattle. Last summer the Environmental Protection Agency named Kaufman as the lead researcher to study the issue and awarded the study a $30 million grant, its largest yet for scientific research.

Levels of pollution commonly found in major U.S. cities can trigger sudden heart attacks, contribute to hardening of the arteries or atherosclerosis, induce abnormal heart rhythms, cause inflammation of heart tissue and even thicken the blood, according to a review of the topic in the June 1, 2004, issue of the journal Circulation. All of these effects can eventually lead to death from cardiovascular causes such as heart attack.

Although the issue of "environmental cardiology" is gaining widespread attention among researchers, your doctor may still be in the dark. "It is something the American Heart Association (AHA) talked about for several years, but until recently, we didn't have the epidemiological and mechanistic studies to back it up," says Robert D. Brook, assistant professor of medicine in the Division of Cardiovascular Medicine at the University of Michigan and lead author of a statement on the issue by an AHA panel last June. "We felt we should inform the public," Brook adds.

Outdoor air pollution, which comes mainly from automobile tail pipes and industrial smokestacks, includes gases like carbon monoxide, sulfur dioxide and ozone, as well as particles of dust, ash, lead and other metals. At least two studies have found that spikes in outdoor PM10 (particles smaller than 10 microns in diameter) led to an immediate increase in cardiopulmonary deaths within the following 24 to 48 hours. Particles of less than 2.5 microns, or PM2.5, appear to be especially harmful. A study of approximately 500,000 people scattered across all 50 U.S. states found that increases of 10 micrograms PM2.5 per cubic meter of air led to a 12 percent increase in death from cardiovascular diseases. In other words, the more tiny particles you breathe, the greater your risk of death.