Air pollution may be causing far more deaths from heart attacks than has been recognised - at least in women.
One of the largest studies of its kind has found that women breathing polluted city air were at increased risk of heart attacks and strokes. The study involved almost 66,000 women aged between 50 and 79 who were monitored for nine years as part of the Women's Health Initiative, a major US investigation into the causes of heart disease in women.
The results, in The New England Journal of Medicine, suggest that - for older women at least - fine particulates are far more hazardous than was thought.
Pollution was assessed by the average number of particulates, which ranged from four to almost 20 micrograms per cubic metre of air. The risk increased by 76 per cent with each 10 microgram step up. For women living in cities, however, the risk more than doubled (128 per cent) with each step up in pollution level.
A previous investigation by the American Cancer Study found a 12 per cent increased risk of cardiovascular heart disease with each 10 microgram rise. That study was conducted among men and women across a range of ages. An unanswered question posed by the new study is whether women in general, or this particular group of women, are unusually susceptible.
An editorial in the journal says women have less heart disease than men, but those who do are more vulnerable to heart attacks because their coronary arteries are smaller and more prone to be "dysfunctional". Air pollution could trigger a fatal attack.
Professor Jeremy Pearson, associate medical director of the British Heart Foundation, said: "This robust new research follows other large-scale studies which have linked long-term exposure to air pollution to an increased risk of death from heart disease and stroke, and suggests the increased risk is greater than we previously thought. This adds to the mounting evidence that air pollution should be taken seriously as a risk factor for cardiovascular disease."
The study is the second in a week to highlight the hazards of air pollution. Last Friday, a report in The Lancet presented evidence that traffic fumes could seriously impair the lung development of children.