Any burnt leaf produces carcinogens even marijuana.
Personally i think that people have been smoking weed and tobacco for a very very long time,suddenly everyone has cancer.
Woohoo scapegoat time,it obviously has nothing to do with car,bus,train,plane,boat,factory,nuclear power stations,high energy masts,nuclear warhead testing,dodgy chemical dumping,oil refinement,microwave ovens,holes in the ozone layer,electrical equipment,wireless masts,methane gases and any other general pollution that you can think of.
Its all tobaccos and weeds fault
Now i am not saying smoking wont make you worse but theres also a lot of speculation that the main cause of cancer from tobacco is the highly toxic feeds they use to get some serious growth from the plants in as little time as possible.
Why does my tobacco have a health warning on it when 8 out of 10 people can smoke their whole life's and never get cancer yet if anyone breathes in a cars fumes in a confined space for about an hour they will be dead
Think about it