A report published in the British Medical Journal found you have an increased risk of suffering a heart attack during the six hours directly after being exposed to high levels of pollution.
The researchers believe traffic fumes probably don’t cause heart attacks directly, although they agree repeated periods of exposure have a substantial negative effect on life expectancy.
British Heart Foundation associate medical director, Prof Jeremy Pearson, said the medical records of almost 80,000 heart attack patients were studied and cross-referenced with air pollution data (measuring CO, NO2
, PM10 and ozone) to see if there was a link with the onset of heart attack symptoms.
"This large-scale study shows conclusively that your risk of having a heart attack goes up temporarily, for around six hours, after breathing in higher levels of vehicle exhaust,” Prof Pearson said."We know that pollution can have a major effect on your heart health, possibly because it can 'thicken' the blood to make it more likely to clot, putting you at higher risk of a heart attack."Our advice to patients remains the same - if you've been diagnosed with heart disease, try to avoid spending long periods outside in areas where there are likely to be high traffic pollution levels, such as on or near busy roads."
Lead researcher from the London School of Hygiene and Tropical Medicine, Krishnan Bhaskaran, said one-off exposure to fumes was unlikely to cause a heart attack.
“If anything, it looks like it brings heart attack forward by a few hours,” he said. “These are cardiac events that probably would have happened anyway."
Both researchers agreed smoking and unhealthy diets were much larger heart attack risk factors than car fumes.