A study at Sweden's Umea University found that exposure to diesel exhaust causes a rapid deterioration of the function of blood vessels, as long as 24 hours after exposure.

As reported in www.sciencedaily.com, the study, "Why Diesel Particulates Cause Cardiovascular Disease," was designed to clarify why air pollution, especially diesel particulates, can cause heart attacks and strokes.

The study used an exposure chamber where volunteers were exposed for one hour to diesel exhaust with a particulate concentration of about 300 ug/m3, and another exposure to filtered air. A group of healthy individuals was tested, as well as a group of individuals with clinically fully stable coronary artery disease.

In the healthy subjects, exposure to diesel exhaust decreased two important blood-vessel functions: the regulation of the width of the blood vessels, and the body's ability to dissolve blood clots. In addition, the study found that as much as 24 hours after their exposure to exhaust, the capacity of their blood vessels to expand was affected. There also were signs of inflammation.

In the subjects with coronary artery disease, the study also found the lowered capacity to dissolve blood clots and impaired ability of blood vessels to expand. Most important, after exposure to diesel exhaust, patients' EKGs showed signs that were consistent with a shortage of oxygen in the heart muscle - in other words, an increased risk of heart attack. This was despite the fact that the patients were fully stable in their coronary artery disease and were under optimal medical treatment.

This study follows one released last September by Umea University and the University of Edinburgh that measured the effects of diesel exhaust on heart and blood vessel function in men who had previously experienced a heart attack. The research, funded by the British Heart Foundation and published in the New England Journal of Medicine, found that inhaling diesel exhaust caused changes in the heart's electrical activity, suggesting that air pollution reduces the amount of oxygen available to the heart during exercise.

In that study, 20 men who had suffered a previous heart attack were exposed for one hour to either filtered air or dilute diesel exhaust while intermittently riding a stationary bicycle in the Umea exposure chamber. It found that the diesel exhaust caused a three-fold increase in the stress of the heart during exercise. In addition, the bodies' ability to prevent blood clots was reduced.