Exhaust fumes might threaten people’s hearts

Grimy diesel exhaust doesn’t just stink up highways. The nanoparticles in diesel fumes also thwart proteins that dissolve blood clots, researchers have discovered, perhaps increasing the risk of heart attacks.

Studies had already shown that diesel fumes worsen cholesterol’s ill effects (SN: 8/11/07, p. 93), and that people living in highly polluted areas are more likely to have heart attacks. David E. Newby of Edinburgh University and his colleagues decided to study the latter connection in a controlled environment: a chamber into which they could pump either filtered air or air contaminated with diesel exhaust.

“The diesel levels in the chamber are about what you’d expect at roadside in a busy city,” says Newby.

One at a time, each of 20 volunteers alternated 15-minute periods of exercise and rest in the chamber. The researchers found that blood vessels of healthy subjects exercising in diesel-filled air didn’t relax as easily as when they worked out in filtered air. When people with coronary heart disease, whose blood vessels were already too stiff to relax easily, exercised in smoggy air, their vessels released fewer clot-dissolving proteins than when they exercised in clean air.

The findings, reported in the Sept. 13 New England Journal of Medicine, suggest that people at risk for heart attacks shouldn’t exercise outside on highly polluted days, said Newby.

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