Well. I would like to start by saying that the alkaloids in weed actually slow down the growth of certain types of lung cancer and kill the cells of others while leaving the healthy cells intact. The amount of tobacco in the blunt wrap is no more than you would find in a CIG ( minus the additives )
You are straight either way you go about it. If you are already smoking weed in amounts that large when you smoke you are already getting enough carcinogens to equal a pack of CIGS. Vaporize.