In highly polluted areas like the capital experts say exercise that make the lungs work harder will narrow the blood vessels, making heart failure more likely.
Exercising in clean air is just as important as controlling high cholesterol in reducing the chance of cardiovascular disease, new research suggests.
In a study experts from Brussels University Hospital examined the effect that air pollution had on a group of test subjects.
Lead author cardiologist Dr Jean-Francois Argacha said: “This is the first human study to report an influence of air pollution on pulmonary vascular function.
“This is a major public health issue for people living in polluted urban areas where exercise could damage the lungs and potentially lead to decompensated heart failure.”
Between 2009 and 2013 Dr Argacha and his team conducted pulmonary pressure tests on a population of 16,295 individuals and compared them with the average air pollution in Brussels on the same day and the last five and ten days.
The team also subjected ten healthy men to ambient air and diluted diesel exhaust fumes in a chamber over a two hour period before conducting a cardiac stress test to stimulate the heart.
They found that air pollution makes it more difficult for the blood to flow into the lungs, specifically impairing the right ventricles.
Air pollution is measured in particulate matter (PM) - coarse dust particles which get into the lungs.
In London more than 3,000 deaths a year are attributed to particulate matter in the air and earlier this week it was revealed that three of the wealthiest boroughs had the highest rates of death caused by dirty air.
Despite a World Health Organisation recommendation that air pollution levels should not exceed a particulate matter rating of 2.5 micrometers at a maximal daily mean, cities worldwide regularly exceed the rating.
It was also found that patients with obstructive sleep apnoea - where the walls of the throat narrow during sleep - are most at risk.
The chamber study of the ten individuals showed that diesel fumes did not affect pulmonary circulation, but did have a harmful effect when the heart was stimulated during exercise.
Dr Argacha said: “This suggests that pollution is more harmful to the lung circulation during exercise.
“Such studies are important because if air pollution causes narrowing of the blood vessels in the lungs (vasoconstriction), this combined with the systemic effects of pollution could cause decompensated heart failure.
“Air pollution was associated with increased pulmonary vascular tone which makes it more difficult for blood to flow to the lungs.
“Longer exposure to air pollution exposure seems necessary to impair right ventricular systolic function.
“Patients with obstructive sleep apnoea were at greater risk.
“Our dual approach provides original data on the impact of air pollution on the pulmonary circulation.
“The individual study strengthens the plausible link emerging from the epidemiological research.”
Dr Argacha, who presented the findings before the European Society of Cardiology, suggests that in areas of heavy air pollution people should limit physical activities and the duration one exercises.
Even though diesel emissions have been associated with healthy outcomes, legislation to prevent air pollution is weak.
The expert added: “Our main advice is to limit physical activities during heavy air pollution.
“More studies are needed before specific recommendations on intensity and duration of exercise can be given.
“Emission controls such as particulate filters have reduced tailpipe emissions, but other sources such as engine crankcases, tyres and brake wear are becoming important.
“No strong evidence exists on effectiveness of face masks to eliminate or reduce particle exposure.”
The research was funded by Zeneca and Biotronik.