The researchers studied twenty men with and without prior myocardial infarction (commonly called a heart attack). They were exposed to either air diluted with diesel exhaust (at levels similar to a roadside in a busy city) or filtered air for one hour during alternative 15-minute periods of rest and moderate exercise in a controlled laboratory facility. They were monitored during two sessions over six hours that the tests were performed.

Led by David E. Newby, of Edinburgh University in England, the researchers found that the blood vessels of the healthy subjects did not relax as easily when they worked out in the diesel fume contained atmosphere as when they worked out in the clear atmosphere.

The subjects with prior heart disease problems had blood vessels that were already too stiff to easily relax in any type of atmosphere. Their vessels released fewer proteins that dissolve clots in blood when they exercised in dirty air than when they exercised in clean air.

Newby’s team concludes that people with heart problems should not exercise outside in polluted air. Their study and previous studies conclude that small particles in diesel fumes damage proteins in the body that dissolve blood clots, thus, increasing the chances of heart attacks. Such studies suggest that people living in highly polluted area are more likely to have heart attacks.

The article based on Newby team’s work is published in the September 13, 2007 issue of The New England Journal of Medicine. The title of the article is “Ischemic and Thrombotic Effects of Dilute Diesel-Exhaust Inhalation in Men with Coronary Heart Disease." Newby’s team consists of: Nicholas L. Mills, Håkan Törnqvist, Manuel C. Gonzalez, Elen Vink, Simon D. Robinson, Stefan Söderberg, Nicholas A. Boon, Ken Donaldson, Thomas Sandström, and Anders Blomberg.

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