MMario As others have pointed out, there is a difference between avoidable risks and unavoidable risks. Yes, Oxygen is can be very dangerous, especially as Ozone, but no-one has yet learned to live without it. On passive smoking, I was brought up in a family of heavy smokers, and have never smoked, but have what sounds to people like a smokers cough - maybe from too much smoke when I was young (Who knows). A number of members of my family have died of smoking-related illnesses, including lung cancer, stroke, and heart disease, and I don't wish to do the same.