The researchers from the University of Duisburg-Essen say that long-term exposure to air pollution from a nearby freeway or busy road can raise the risk of hardening of the arteries, which in turn can lead to heart disease and stroke.

Dr. Barbara Hoffmann, the lead author, says the study is the first to actually show a relationship between long-term traffic exposure and coronary atherosclerosis.

Dr. Hoffmann says that living close to busy traffic which is a major source of urban air pollution, is linked to atherosclerosis in the coronary arteries, the blood vessels that supply the heart.

For the study the researchers examined 4,494 adults, aged 45 to 74, in three large cities in the industrialized Ruhr area of Germany as part of the Heinz Nixdorf Recall Study.

The participants home address was used to estimate each person's exposure to urban air pollution and they were also interviewed about other risk factors such as diabetes and smoking.

The study group also underwent extensive clinical examinations, and had their coronary artery calcification (CAC) measured by electron-beam computed tomography (EBCT).

Other studies have also linked elevated levels of air pollution to an increased risk of heart problems, but this is the first to demonstrate that living near high traffic is associated with coronary atherosclerosis.

The researchers found that the closer the participant lived to heavy traffic, the higher the CAC and that compared with people who lived more than 200 meters from major traffic, the chance of high coronary artery calcification was 63 percent greater for those living within 50 meters.

For people within 51 meters to 100 meters the chance was 34 percent higher and was 8 percent higher for those within 100 meters to 200 meters of heavy traffic.

A five-year follow up study will be completed next year and the research team say politicians, regulators and doctors need to be aware that living close to heavy traffic may pose an increased risk of harm to the heart.

The researchers say their results support those from a recent study conducted in Los Angeles, which showed an association between long-term air pollution and atherosclerosis.

They suggest the potential harm to the population as a result of living close to heavy traffic should be considered when planning new buildings and when assessing patients with coronary artery disease.

The study is published in the current issue of Circulation, an American Heart Association journal.