Living near high-traffic roads may be hazardous to your health

American Heart Association rapid access journal report

DALLAS, July 17 — Long-term exposure to air pollution from a nearby freeway or heavily trafficked streets is associated with a hardening of the arteries that could raise the risk of heart disease and stroke, German researchers reported in Circulation: Journal of the American Heart Association.

“The most important finding of our study is that living close to high traffic, a major source of urban air pollution, is associated with atherosclerosis in the coronary arteries — the blood vessels that supply the heart,” said study lead author Barbara Hoffmann, M.D., M.P.H., from the Institute for Medical Informatics, Biometry and Epidemiology, University of Duisburg-Essen, Germany. “People who live close to a big, heavily traveled road have more coronary atherosclerosis than those who live far away.”

While previous studies linked elevated levels of particulate matter air pollution to an increased risk of fatal or non-fatal cardiovascular events, this is the first study to demonstrate that living near high traffic is associated with coronary atherosclerosis. Traffic sources of air pollution are the major source of difference in pollution exposure within a metropolitan region.

“This is the first study to actually show a relationship between long-term traffic exposure and coronary atherosclerosis, one potential mechanism by which air pollution could lead to an increased risk of death from heart disease,” Hoffmann said.

The study of 4,494 adults, age 45 to 74 years, is part of the Heinz Nixdorf Recall Study that is being conducted in three large, adjacent cities in the industrialized Ruhr area of Germany. Home address was used to estimate each person’s exposure to urban air pollution. Participants answered questionnaires and were interviewed for personal risk factors such as diabetes, smoking and passive smoking and underwent laboratory tests and extensive clinical examinations. Participants then were tested with electron-beam computed tomography (EBCT) for coronary artery calcification.

Compared to participants living more than 200 meters (642 feet) from major traffic, the chance of high coronary artery calcification (top quarter of calcification levels) for those living

• within 50 meters (160 feet) of heavy traffic was 63 percent higher.

• between 51 – 100 meters (164 to 328 feet) was 34 percent higher.

• between 100 and 200 meters (328 to 642 feet) was 8 percent higher.

These percentages were calculated after adjusting for known risk factors such as age, gender, high blood pressure, smoking, cholesterol level and diabetes.

Coronary artery calcification (CAC) occurs when fatty plaques forming in the artery walls become calcified. Researchers used electron-beam computed tomography (EBCT) to measure the calcium deposits in the arteries, which is an accurate measure for coronary atherosclerosis. According to researchers, participants with more “calcification” in these arteries, such as the top quarter of CAC levels (75th percentile or higher) are considered at increased risk for heart attack.

Researchers found that the closer the participant lived to heavy traffic, the higher the CAC.  If the distance between the residence and a major road was reduced by half, CAC was 7 percent higher even after adjusting for cardiovascular risk factors.

“People who live near a German freeway or federal highway, which can be traveled by 10,000 to 130,000 cars daily, have more atherosclerosis the closer they live to the road,” Hoffmann said. “If you live at a distance of, for example, 100 meters (321 feet) from the freeway of highway, then on average you have seven percent more calcification in your coronary arteries than a person with the same cardiovascular risk profile who lives 200 meters (642 feet) away.”

A five-year follow-up study is expected to be completed next year, which should shed more light on whether high traffic exposure causes the artery changes to get worse, Hoffmann said.

“Until then,” she said “politicians, regulators and physicians need to be aware that living close to heavy traffic may pose an increased risk of harm to the heart.  Potential harm due to proximity to heavy traffic should be considered when planning new buildings and roads. And, clinicians and cardiologists need to be aware that a patient’s proximity to heavy traffic may be a factor that should be considered when assessing patients with coronary artery disease.”

In May 2004, American Heart Association experts conducted a comprehensive review of the literature on air pollution and cardiovascular disease. The 2004 scientific statement focused on particulate matter pollution and reaffirmed the dangers of environmental tobacco smoke — called secondhand smoke — as an air pollutant. Particulate matter, also known as particle pollution, is composed of solid and liquid particles within the air. The panel recommended 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.

The study was conducted within the frame of the Heinz Nixdorf Recall Study (Principal Investigators R. Erbel and K. H. Jöckel) and was funded by the Heinz Nixdorf Foundation.

Co-authors are: S. Moebus, Ph.D., M.P.H.; S. Möhlenkamp, M.D.; A. Stang, M.D., M.P.H.; N. Lehmann, Ph.D.; N. Dragano, Ph.D.; A. Schmermund, M.D.; M. Memmesheimer, Ph.D.; K. Mann, M.D.; R. Erbel, M.D. and K.H. Jöckel, Ph.D.

Statements and conclusions of study authors that are published in the American Heart Association scientific journals are solely those of the study authors and do not necessarily reflect association policy or position.  The American Heart Association makes no representation or warranty as to their accuracy or reliability.

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