There’s an old saying among people who work in public health: Tobacco is the only legal product that, when used as intended, will kill you. Decades of research have thoroughly documented the health problems that result from inhaling tobacco smoke – more than a dozen different types of cancer, heart disease, stroke, emphysema and other respiratory diseases, among others. Are these risks an inevitable part of smoking? Or is there a way of creating safe cigarettes without any of these hazards?

“I think it’s very unlikely,” says Stephen Hecht from the University of Minnesota Cancer Center, who studies tobacco carcinogens – substances that cause cancer. Tobacco smoke is a complex cocktail of at least 4,000 chemicals including