I sometimes wonder what actually causes the cancer... could it be smoking toxic chemicals that cause cancer or merely sniffing/injesting any kind  smoke regularly/occasionally into your internal body  especially the lungs. Our great grand parents cooked alot with firewood , sniffed in alot of smokes from the fire,yet they lived long.So, maybe it's toxic chemicals/substance (especially the man-made ones) inside the things they smoke that cause problem like cancer.  .. I would avoid cigarettes because of possiblity of them having toxic chemicals/substances.   


I regards to whether i smoke or not, i actually don't and I wouldn't encourage you to stop those who the smoke don't harm. The risk has to be zero-nothing for the smoker,and the smoke should be beneficial to them.