Traffic fumes may trigger heart attacks--study

Researchers warn that car fumes elevate the risk of a cardiac arrest for up to six hours after exposure.

According to experts, though the absolute risk of traffic provoking a heart attack directly is exceptionally low, repeated exposure can have a substantial negative impact on life expectancy.

For someone with a very low risk for a heart attack, spending time in traffic doesn't mean much, but for those with a history of angina, road pollution might be an additional stressor that could hasten the onset of an attack.

Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which co-founded the study, said, "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.

"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.

Around 80,000 cases of heart attack analyzed
In a bid to establish a link between air pollution and the onset of heart attack symptoms, the researchers conducted a study.

They analyzed data of 80,000 heart attack patients living in 15 urban regions in England and Wales between 2003 and 2006.

As a part of the study, the investigators focused on pollutant particles (PM10), ozone (O3), carbon monoxide (CO), nitrogen dioxide (NO2) and sulphur dioxide (SO2).

They also factored details of the daily temperature and relative humidity and any viral infections in circulation at the time.

In addition, lifestyle factors, age, smoking, history of heart attack were taken into account.

Revelations of the study
The analysis revealed people exposed to traffic pollutants, specifically PM10 and NO2 were more prone to experiencing a heart attack one to six hours later. However, after this time frame, the danger subsided.

The authors stated, "Higher levels of PM10 and NO2, which are typically markers of traffic related pollution, seem to be associated with transiently increased risk of myocardial infarction 1-6 hours after exposure, but later reductions in risk suggest that air pollution may be associated with bringing events forward in time rather than increasing overall risk."

Implications of the study
According to experts, pollution produced by car engines can get past the normal defense mechanisms in the lungs and penetrate deeply into the air exchange regions.

Exposure to traffic is particularly harsh on patients with a history of angina who should avoid inhaling toxic fumes. It leads to inflammation, cholesterol build-up in the arteries and stress, factors that work synergistically to raise the cardiovascular risk.

Pearson stated, "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."

The study, published in the British Medical Journal.