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.