If something is a natural act or not has little bearing on it being harmful or not.
Oh but it does matter … If a person is stupid enough to perform a natural act of eating poisonous berries then they will perform the natural act of dying ….
The "natural act" as I refer to is physiological …. It is a well known fact from about the kindergarten years that you cannot live without breathing.... Don't believe me then dive into a swimming pool and stay under water for 10 minutes without coming to the surface.... So, it is quite obvious that the human body requires air/oxygen to live and survive... Since the air you breath comes into your body and into your lungs, then it is obvious that your lungs/body are meant to breath the atmosphere (not vaper, tobacco smoke, pollutants from factories etc..) In other words, the natural order is for your lungs to breath in natural air/atmosphere... To breath in anything else is not exactly what nature intended. When the body violates the natural laws that created it, and sustains it, then it usually results in bad things occurring with health...
Everything gets back to "common sense" that I mentioned earlier..... Eating is a "natural act" but if you are a glutton and always eat too much then it will eventually kill you..... We have to have a balance at all things we do in this life. Also, you need food to live and survive, but you certainly do not need vapor being pumped into your lungs to make you survive. You can live without vape but you can't live without nutrients/food..You can live without smoking tobacco.... You can live without recreational drugs.... In other words, common sense. People can try to justify their drug addiction, alcohol abuse, tobacco addiction, gluttony, vaping, and a whole host of other things that are none too natural for the body but what always happens is that the natural laws prevail and the person suffers the consequences.
I am an avid believer in vaping, simply in the fact that it helps many people to get away from those nasty tobacco products, which are PROVEN killers and health destroyers... On the other hand, I in no way think vaping is TOTALLY safe due to the fact that our bodies are made to breath in natural atmosphere free of vape, pollutions/toxins, tobacco smoke or anything else man-made..... Human bodies are resilient to a certain point.. You can breath in toxins from time to time or smoke from time to time and nothing will probably ever happen negatively to your health. But on a continual basis of inhaling foreign substances that nature did not intend then chances are quite good that the outcome may be negative.
Another thing that I notice that many people here fixate on is the organ known as the lungs …. But what about the other organs of the body? Your pancreas and liver work together to filter foreign substances from the body..... They have to filter out all of the substances you vape so what will happen to those organs in 40 years? What about the brain? The stuff you vape gets to your brain before the liver can filter it out and so in 40 years will it effect the brain in some unknown way? The simple truth is that vaping is young and there is much to be learned about long-term effects in ALL parts of the body. I am 100% for vaping especially compared to smoking but a person who is not addicted to tobacco should think carefully before they start vaping.