US Study: September 21, 2007
CHICAGO - Tiny particles of air pollution -- less than one tenth the width of a human hair -- can trigger clotting in the blood, US researchers said on Thursday in a finding that helps explain how air pollution causes heart attacks and strokes.
Large population studies have shown pollution from the exhaust of trucks, buses and coal-burning factories increases the risk of fatal heart attacks and strokes.
But researchers have not understood how these microscopic particles actually kill people.
CHICAGO - Tiny particles of air pollution -- less than one tenth the width of a human hair -- can trigger clotting in the blood, US researchers said on Thursday in a finding that helps explain how air pollution causes heart attacks and strokes.
Large population studies have shown pollution from the exhaust of trucks, buses and coal-burning factories increases the risk of fatal heart attacks and strokes.
But researchers have not understood how these microscopic particles actually kill people.
"We now know how the inflammation in the lungs caused by air pollutants leads to death from cardiovascular disease," said Dr. Gokhan Mutlu of Northwestern University in Chicago, who studied the effects of air pollution in mice.
Lungs inflamed by pollution secrete interleukin-6, an immune system compound that sparks inflammation and has been shown to make blood more likely to clot.
The research appears in the Journal of Clinical Investigation. It follows a study last week in the New England Journal of Medicine that found breathing diesel fumes interfered with heart attack survivors' ability to break down blood clots.
Mutlu got a clue about the clotting issue two years ago when he was studying the effects of air pollution on heart failure in mice. Mice who had been exposed to pollution bled significantly less.
"They were forming blood clots," he said in a telephone interview.
In the latest study, he and colleagues exposed mice to particles of air pollution collected by the US Environmental Protection Agency. These were mixed with a saline solution and injected into the lungs of mice.
Mice exposed to pollution showed a 15-fold increase in interleukin-6 just 24 hours later. That time frame is important because some studies have shown a spike in air pollution can boost heart attacks with 24 hours. "This suggested that interleukin-6 was the driving force," Mutlu said.
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