The great many downsides of smoking are certainly well-documented by now (to say the least), but something I've struggled to find an answer to is the following:
When looking at health risks of smoking, what's caused by the substance in question being absorbed and interacting negatively with the body, and what's caused simply by the act of inhaling smoke?
My assumption would be that most of the damage is caused by the inhalation of the smoke itself, especially any damage to the mouth, oesophagus, and lungs, smoke (any kind) simply being dangerously irritating to these parts of the body. Then, damage to the brain and/or other parts of the body are mostly caused by the specific substance being smoked... How much of this assumption is correct?
Perhaps it's misleading to try and separate the smoke from what's causing the smoke at all, as what's creating the smoke dictates how bad it is. However, if that's the case, doesn't that imply that some products for smoking, while still bad, may create smoke which is "less damaging" than others?
For ease of answering, feel free to just concentrate on tobacco products (possibly including any additional chemicals added to the final product) if you feel it's necessary to keep your answer from not being too long.