Scientists have discovered how air pollution triggers heart attacks, which cause thousands of deaths each year. Diesel exhaust fumes increase the stress on the heart during exercise and may account for the rise in heart deaths on days when pollution from traffic fumes is high, they say.

The World Health Organisation estimates that air pollution causes 800,000 premature deaths worldwide and a recent US study suggested long-term exposure to traffic fumes increases the risk of death from heart disease and stroke by 76 per cent.

Researchers from the University of Edinburgh found that inhaling diesel fumes caused a threefold increase in stress on the heart by altering its electrical activity. The risk of blood clots was also increased.

The scientists, working with colleagues from Umea University in Sweden, tested 20 men who were made to inhale dilute diesel exhaust while riding an exercise bike in the laboratory.

The results, published in The New England Journal of Medicine, show that air pollution reduces the amount of oxygen available to the heart during exercise.

Nicholas Mills, of Edinburgh University, who led the study, said diesel engines generated 10 to 100 times more pollutant particles than petrol engines and the number of diesel-powered cars was increasing. The findings could increase pressure for pollution filters to be fitted to diesel cars.

Professor Peter Weissberg, medical director of the British Heart Foundation, said: "We would still encourage heart patients to exercise regularly, but preferably not when there is a lot of local traffic around."
(By Jeremy Laurance, The Independent, 13/09/2007)