All you really need to know is that with life comes with risk. Nothing good is going to happen to your body when you suck a bunch of poisons into your mouth and then blow it out again (you don't need data to figure that out). The soft moist tissues are going to take some of those poisons into your system. Enough to cause permanent damage or lead to sickness? That depends on your immune system and genes.
I choose to joust with death a bit and smoke. I also drive a vehicle, take pictures of bears in the wild, fly, and do other things which come with a bit of risk. No agency, scientist, or study can give to you an absolute.
So you can either suck it up (pun intended) while accepting the risks, or not add to the stresses of everyday living your body is already coping with by not smoking. If you come down with a disease which takes time to kill you will have plenty of time to rue some of the decisions you made. If it's a heart attack or gunshot to the head, well . . . no regrets. Well, possibly a quick nod to that burrito you just wolfed down. Or, a fleeting thought that you should have believed her when she told you she thought her husband was home.