Traffic fumes trigger more than eight times as many heart attacks as snorting cocaine, according to a new study.

If an individual with heart disease takes cocaine, their chance of having a heart attack increases 26-fold. If a person with heart disease is exposed to heavy traffic fumes, their chance of having one increases by five per cent, the journal Lancet reports.

But because the number of people being exposed to traffic fumes is more than cocaine users, on a population-wide basis, traffic pollution triggers more heart attacks, scientists say.

Applied to U.K., where there are around 124,000 heart attacks each year, traffic fumes could trigger 9,200 heart attacks, and cocaine around 1,100, according to the Telegraph.

Scientists at Hasselt University and the Catholic University of Leuven, both in Belgium, came to their conclusions after reviewing 36 studies.

These looked at heart attack risk factors in people with heart disease, such as taking physical exertion, having sex, eating a large meal, drinking alcohol or coffee, smoking marijuana and snorting cocaine.

These studies looked at how much taking part in such activity raised the risk of heart attack in an individual.