How much less dangerous is breathing smoke from burning wood and coal compare to smoking tobacco?
Edit: Sorry. I should have made the question clearer.
If this were an experiment, it would be set up like this. Subject 1 is a control, so he is exposed to smoke from burning tobacco for a year. Subject 2 is exposed to smoke from burning maple leaves for a year. Subject 3 is exposed to smoke from burning pine needles for a year. The other subjects continue in this fashion, being exposed to smoke from many different sources. The rats are examined for lung cancer through this year and for the remainder of their lives. What would the expect results of this experiment be?