Americans inhale more cancer-causing agents with their cigarettes, probably because of the tobacco blend, while smokers in Canada, Britain and Australia get less, U.S. researchers reported in the June issue of Cancer Epidemiology, Biomarkers & Prevention.

Their unique study also demonstrated that the amounts of these carcinogens in a smoker’s cigarette butts directly correlated with tell-tale compounds in the smoker’s urine. Read about the study.