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People living in big cities are “breathing in an oil spill” every day because of air pollution that can have significant effects on cardiovascular health, scientists said today.

Fine particles and chemicals created by traffic exhausts can trigger heart attacks, abnormal heartbeats and hardening of the arteries, according to several new studies that suggest tougher emissions standards may be needed to improve environmental health.

One research project has found that fumes from petrol and diesel engines can activate biochemical pathways that are known to cause heart attacks, while another has shown that a class of exhaust chemicals called polycyclic aromatic hydrocarbons (PAHs) can lead to heart arrhythmia.

Two further studies presented to the American Association for the Advancement of Science (AAAS) conference in Boston have linked air pollution at levels measured in the cities of New York and Los Angeles to increased hardening of the arteries, one of the biggest risk factors for heart disease and heart attacks.

Adverse effects are particularly pronounced among people who already have coronary artery disease, or raised blood levels of LDL cholesterol, the “bad” version of the fat linked to heart disease.

John Incardona, of the US National Oceanic and Atmospheric Administration, has studied the hearts of zebrafish — a standard laboratory model for the human heart — to show a link between PAHs and abnormal heartbeats. He said the findings suggest that the pollutants' effects are comparable to those of an oil slick on aquatic life — PAHs are produced by burning oil and its derivatives.

“When we first started studying the effects of oil on fish embryos I really never thought it would be applicable to human health,” he said. “This is because one doesn't normally think about people being exposed to oil in the same way that a fish embryo is after an oil spill.

“Yet the distribution of airborne PAHs really mirrors what is in oil and its refined products. So in essence we are breathing aerosolised oil spill in our big cities. The available data suggest that these PAHs are present in burning oil in levels high enough to result in pharmacologically active levels in the human blood stream.”

The emerging understanding of how air pollution affects the cardiovascular system means that air quality standards should be revisited. “A physician who knowingly gave an aerosolised particle toxin to a patient with coronary artery disease or congestive heart failure would probably be sued for malpractice,” Dr Incardona said. “But the air in our cities is doing just that to millions every day, unknowingly.

“This is a very simple hypothesis and I think these compounds need to be looked at as a source of cardiovascular impacts of air pollution.”

A study led by Matt Campen and Amie Lund, of the Lovelace Respiratory Research Institute in New Mexico, used mice with high cholesterol to study the effects of vehicle exhausts. They found that the fumes could activate molecules called matrix metalloproteinases, which are known to cause heart attacks in people.

“While cardiovascular disease is known to be influenced by genetics and lifestyle, recent evidence shows a strong and consistent relationship with exposure to air pollution, even at levels deemed ‘acceptable' by the regulatory authorities,” Dr Campen said.

“In the past five years, it has become apparent that air pollution can both chronically increase the risk of cardiovascular disease, as well as acutely induce heart attacks.”

A paper from Lung Chi Chen, of New York University School of Medicine, has suggested that air pollution at levels measured in New York could have as great an impact on cardiovascular health as passive smoking. Dr Chen found that mice exposed to fine particulate matter for six hours a day and five days a week over six months suffered as much arterial damage as mice exposed to second-hand smoke for the same period.

Similar findings have emerged from research led by Jesus Araujo, of the David Geffen School of Medicine at the University of California, Los Angeles. He found that air pollution at levels measured in Los Angeles increased the formation of fatty plaques in the arteries of mice.

Peter Weissberg, Medical Director of the British Heart Foundation, said of Dr Incardona's study: “We do not see a lot of spontaneous, unexplained heart disease and arrhythmia in adults. It is a long way to extrapolate from something shown in the development of zebrafish to something that would affect healthy adult human beings.

“It is, however, an interesting study. It suggests that these chemicals clearly have an important effect on these developmental chemical interactions in the heart. So if adults were exposed to doses of these chemicals as large as the fish were, maybe we might see an effect.”

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