THURSDAY, Sept. 20 (HealthDay News) -- Microscopic pollution particles spewed by diesel engines and coal-burning plants may spur blood clots that can trigger heart attacks and strokes, U.S. scientists say.

Researchers at Northwestern University in Chicago found that these tiny particles -- which are less than one-tenth the diameter of a human hair and too small to be filtered by the nose or mouth -- caused hyperclotting of the blood in animals.

The particles trigger inflammation in the lungs, which then secrete a substance called interleukin-6 that promotes blood clotting. This results in an increased risk of heart attack or stroke in people with heart disease or a previous history of stroke.

While previous epidemiological studies have identified a link between air pollution and cardiovascular disease and death, this is the first study to demonstrate how pollution may actually trigger heart attacks and strokes, according to the researchers.

"This is a critical missing piece of the puzzle that has eluded scientists for decades," study lead author Dr. Gokhan Mutlu, assistant professor of pulmonary and critical care medicine, said in a prepared statement. "Now we know how the inflammation in the lungs caused by air pollutants leads to death from cardiovascular disease."

"Using low-dose aspirin to keep their blood thin may help protect people at risk," Mutlu suggested.

The study was published online Thursday in the Journal of Clinical Investigation and was expected to be in the Oct. 1 print issue.

More information

The American Academy of Family Physicians has more about the health effects of air pollution.