An individual’s risk of heart attack is 62 percent greater on days with the worst air pollution, according to a study of 772 heart attack victims in Greater Boston published today in the journal of the American Hearth Association. The study by researchers at the Beth Israel Deaconess, the Harvard School of Public Health, and Massachusetts General Hospital found that the likelihood of heart attacks rose in the hours following exposure to high levels of particulate pollution. The researchers noted that Boston doesn’t have especially bad pollution, so the risk could be even worse in cities like Houston and Los Angeles.