I've noticed this weird trend of weightlifters smoking. The excuse is that since they are anaerobic athletes, they don't have to worry about the damage to their aerobic capacity. Trust me, there are plenty of other reasons not to smoke, and I'm going to tell you a few of them here.
Epoxides and DNA Adducts
An epoxide is an incredibly unstable three atom ring, consisting of two carbons and one oxygen. This formation is created by any combustion of organic matter, and this includes cigarettes and automobile exhaust. With cigarettes you are inhaling this molecule directly into your lungs.
As I've said, this a highly unstable molecule, and it reacts with molecules in the cells of your entire respiratory tract. Esophagus, bronchi, aveoli, it is going to react with proteins and DNA. And when it reacts with DNA, creating adducts onto the nucleic acids, you can get copy errors during replication for cell division.
Now sure, there are only a handful of genes where these copy errors are going to cause major issues, but is that a lottery you want to play?
Tar Blockage and Cilia Death
We all know that there is tar in cigarettes. I have no idea why it's there, what goes on in the production process that creates this. But you get that crap into your lungs, and effectively close off small sections of your lungs, filling up aveoli and coating the lungs.
Plus the noxious chemicals kill off the little hairs, called cilia, in your lungs. These hairs help move blockages out of the lungs, such as mucus when you're sick. Kill these off, and you can no longer clear out physical blockages. That tar is going to just sit there.
COPD and Emphysema
These are illnesses that have been introduced recently and could largely be eliminated if people just stopped smoking. How many are looking forward to rolling an oxygen tank around with them when they are 60?
Social Stigma (my opinion)
Okay, this one is my opinion, so you can stop reading here if you want.
When I see someone light up, I automatically lose some respect for them. Thing is, no one starts smoking because they think it's good for them. No one starts because they are trying to better themselves. I've heard it's a "stress reliever". So are a lot of things that are far less detrimental.
People do it because they see some one else do it, some group they are in or want to be a part of does it, or they are trying to not be something (rebel, if you will). In other words, peer pressure. A lack of character strength. That's what I see when a person lights up: weakness.