WASHINGTON, Nov. 6 (Xinhua) -- Increased roadway pollution produced by diesel fuel in vehicles is leading to a cascade of conditions that could result in heart attack or stroke, researchers reported Tuesday at the American Heart Association's Scientific Sessions 2007.

    United Kingdom and Swedish researchers found that diesel exhaust increased clot formation and blood platelet activity in healthy volunteers -- which could lead to heart attack and stroke.

    "The study results are closely tied with previous observational and epidemiological studies showing that shortly after exposure to traffic air pollution, individuals are more likely to suffer a heart attack," said Andrew Lucking, lead author of the study. "This study shows that when a person is exposed to relatively high levels of diesel exhaust for a short time, the blood is more likely to clot. This could lead to a blocked vessel resulting in heart attack or stroke."

    The double-blind, randomized study included 20 healthy men, 21 to 44 years old. They were separately exposed to filtered air (serving as a control) and to diluted diesel exhaust at 300 micrograms per meter cubed (mcg/m3), a level comparable to curbside exposure on a busy street.

    To measure clot formation, researchers used low and high shear rates, recreating flow conditions inside the body's blood vessels. Compared to filtered air, breathing air with diluted diesel exhaust increased clot formation in the low shear chamber by 24.2 percent and the high shear chamber by 19.1 percent. The researchers also found an increase in platelet activation, which plays a central role in blood clotting.

    It's unclear whether these findings would apply to gasoline-powered engines, Lucking said. Diesel engines generate many times more fine pollutant particles than comparable-sized gasoline engines.