Air Pollution Is Serious Cardiovascular Risk

American Heart Association
Tuesday, 1 June 2004

Exposure to air pollution contributes to the development of cardiovascular diseases, according to a new American Heart Association scientific statement published in today's print issue of Circulation: Journal of the American Heart Association.

"The increase in relative risk for heart disease due to air pollution for an individual is small compared with the impact of the established cardiovascular risk factors such as high blood pressure or high cholesterol. However, this is a serious public health problem due to the enormous number of people affected and because exposure to air pollution occurs over an entire lifetime," said Robert D. Brook, M.D., lead author of the statement and an assistant professor of medicine in the Division of Cardiovascular Medicine at the University of Michigan in Ann Arbor.

Until now, the American Heart Association had not drawn firm conclusions about the long-term effects of chronic exposure to different pollutants on heart disease and stroke because of flaws in research design and methodology of many pollution studies.

The association's experts conducted a comprehensive review of the literature on air pollution and cardiovascular disease. This scientific statement focuses on particulate matter pollution and reaffirms the dangers of environmental tobacco smoke called secondhand smoke as an air pollutant. Particulate matter (PM), also known as particle pollution, is composed of solid and liquid particles within the air.

They referenced several significant studies.

"A recent report from the American Cancer Society study cohort found that long-term exposure to fine particulate air pollution at levels that occur in North America increased the risk for cardiovascular mortality. The risk increased by 12 percent for every 10-micrograms-per-1-cubic-meter-of-air elevation in fine particle concentration," Brook said.

He said long-term differences in fine particulate matter levels between North American cities can vary by as much as 30-40 ug/m3.

"The largest portion of this increased mortality rate was accounted for by ischemic heart diseases (e.g., coronary attacks), however other causes were also increased, such as heart failure and fatal arrhythmias," he said.

In addition, they cited another study that suggested a person's exposure to the harmful components of air pollution may vary as much within a single city as across different cities. After studying 5,000 adults for eight years, the researchers also found that exposure to traffic-related air pollutants was more highly related to mortality than were city-wide background levels. For example, those who lived near a major road were more likely to die of a cardiovascular event.

The panel drew several conclusions about pollution:

  1. Prolonged exposure to elevated levels of particle pollution is a factor in reducing overall life expectancy by a few years.

  2. Short-term exposure to elevated levels of particle pollution is associated with the increased risk of death due to a cardiovascular event.

  3. Hospital admissions for several cardiovascular and pulmonary diseases are increased in response to higher concentrations of particle pollution.

The panel recommends that people with heart disease or cardiovascular risk factors, diabetes or pulmonary disease limit outdoor activities when pollution is high, per Environmental Protection Agency Air Quality Index recommendations.

During the last decade, epidemiological studies conducted worldwide have shown that elderly patients, people with underlying heart or lung disease, lower socioeconomic populations and people with diabetes may be at particularly increased risk of cardiovascular disease from air pollution.

All Americans should be aware of potentially hazardous cardiovascular health effects of air pollution, according to the scientific statement. The EPA provides daily information about ozone and particulate matter levels for more than 150 cities at www.epa.gov/airnow.

"Healthcare providers and at-risk patients should be educated about the health risks related to air pollution and about the availability of the daily air pollution updates," Brook said.

The panel encourages the American Heart Association to actively work to educate the public and public policy-makers about the effects of air pollution on cardiovascular disease by featured presentations at its annual meeting, association-sponsored public education activities, and through advocacy.

Air pollution is composed of many environmental factors, such as carbon monoxide, nitrates, sulfur dioxide, ozone, lead, secondhand tobacco smoke and particulate matter. Particulate matter can be generated from vehicle emissions, tire fragmentation and road dust, power generation and industrial combustion, smelting and other metal processing, construction and demolition activities, residential wood burning, windblown soil, pollens, molds, forest fires, volcanic emissions and sea spray.

Secondhand smoke is the single largest contributor to indoor air pollution when a smoker is present according to the statement. Studies of secondhand smoke indicate that air pollution in general can affect the heart and circulatory system. Previous research has established that exposure to the secondhand smoke of just one cigarette per day accelerates the progression of atherosclerosis, (hardening of the arteries) so "it is plausible that even low doses of air pollution could have negative effects on coronary" functions, according to the panel.

"Protecting individuals from secondhand smoke is critical, and fortunately, an area where communities and states are already making a big difference," said M. Cass Wheeler, CEO for the American Heart Association. "Comprehensive smoking bans are in place in eight states already, and in hundreds of communities around the country. Eliminating secondhand smoke in workplaces, restaurants and bars should be a priority for every state and community."

The American Heart Association statement noted that more research is needed to determine the underlying biological mechanisms and pathophysiological pathways that may contribute to the development of cardiovascular disease and to identify the toxicities of various air pollutants. The statement details several areas for future research.

"In addition, we hope that these conclusions will provide further support to the importance of the present-day air quality standards," Brook said.

Other panel members include Barry Franklin, Ph.D.; Wayne Cascio, M.D.; Yuling Hong, M.D., Ph.D.; George Howard, Ph.D.; Michael Lipsett, M.D.; Russell Luepker, M.D.; Murray Mittleman, M.D., ScD; Jonathan Samet, M.D.; Sidney C. Smith, Jr., M.D.; and Ira Tager, M.D.

For more information, or to contact American Heart Association, see their website at: www.americanheart.org

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