Air Pollution Ups Heart Disease Risk, Deaths

June 1, 2004 -- Air pollution increases the risk of heart disease, fatal heart attack, and abnormal heart rhythms (arrhythmias). For people at high risk, a heart attack could occur just a few hours after exposure, according to an expert panel.

The researchers' scientific statement, published by the American Heart Association, appears in the current issue of the journal Circulation: Journal of the American Heart Association. It is intended to provide doctors and regulatory agencies (including the Environmental Protection Agency or EPA) with a comprehensive review of the effects that air pollution has on heart disease.

Indeed, during the last decade, a growing body of evidence has led to heightened concern about the health effects of air pollution, writes researcher Robert D. Brook, MD, a professor of cardiovascular medicine at the University of Michigan at Ann Arbor.

Carbon monoxide, nitrous oxide, sulfur dioxide, ozone, lead, and particulate matter have all been linked with increased hospitalizations and deaths caused by heart disease, he says.

One recent analysis was based on data from 90 large U.S. cities - showing air pollution caused a 21% increased death rate overall, with 31% of increased deaths from heart and lung disease, Brook reports. This and other studies show that air pollution may accelerate the development of atherosclerosis, or hardening of the arteries -- the underlying process that causes heart disease.

Some of these effects, such as atherosclerosis, occur over time. These effects from pollution may also happen abruptly, as with an irregular heartbeat or heart attack, he writes.

The Evidence

"There are several hundred published epidemiological studies linking air pollution with human illness," writes Brook. "During the past 15 years, the magnitude of evidence and number of studies linking air pollution to [heart disease] has grown substantially."

Among the evidence of harmful long-term effects:

• A 16-year Harvard study of 8,111 adults living in six large cities found that overall death rate in the most polluted city was 12% higher than in the least polluted city. Cardiovascular disease was the No. 1 cause of death in this group. Cardiovascular diseases include conditions such as heart disease, heart attack, stroke, and arrhythmias.
• A 16-year study of 500,000 adults in all 50 states linked chronic exposure to air pollution with 6% increased deaths from heart- and lung-related conditions and 8% more lung cancer-related deaths. That study was conducted by the American Cancer Society.

About the short-term health risks:

• A nationwide study of all 50 million people in the 20 largest U.S. cities showed higher death rates -- from heart and lung disease as well as other causes -- on the day following the worst pollution days.

Regarding exposure to high levels of particle pollution, the panel concluded:

• Prolonged exposure is a factor in reducing overall life expectancy by a few years.
• Short-term exposure is associated with increased risk of death caused by a heart-related event such as heart attack or heartbeat irregularity.
• Elderly people with pre-existing, chronic lung disease, heart disease, or heart failure may be at especially high risk during high-pollution days.
• Smoking clearly increased the risk of death caused by heart failure and heart attack.

The toxins in air pollution put stress on a host of body systems -- sending damaging "free radicals" throughout the body and triggering inflammation in the heart, blood vessels, and lungs, Brook explains. This inflammation damages the body systems, causing cancer and heart disease.

SOURCE: Brook, R. Circulation: Journal of the American Heart Association, June 1, 2004: pp 2655-2671.