I'm a little late to this thread and against my better judgement am still going to post this. I do not give permission whoever may decide to cut and paste words together from it rather than refer to it in whole.
There are multiple combustion products released from tobacco that can cause a variety of medical problems. These range from CO, a byproduct of combustion that can decrease the oxygen carrying capacity of red blood cells. There are VOCs of different sorts including the familiar formaldehyde which is a known, albeit low grade, carcinogen. There are a variety of nitrosamines produced which are carcinogenic. There is production of microparticles that can penetrate into the alveoli of the lungs where they can contribute to a chronic inflammatory response that can lead to damage, scarring, and decreased function if those teeny tiny air sacs. And there are toxic metals in the brew as well. Not nice stuff.
Vaping on contemporary, or third generation ENDS products is associated with the production of some of the above mentioned toxic crap. There is nicotine, not terribly toxic in itself but still does cause arterial constriction which is generally not a problem unless you have a compromised circulatory system or a rare but serious "sensitivuty" to nicotine from any source which results in dramatic vasoconstriction ultimately leading to amputation of limbs from the loss of blood flow. These are folks who can't even use a nicotine patch or gum as they have the same reaction. Interestingly they are also typically profoundly addicted to nicotine and will seek it out despite the pretty obvious loss of fingers, toes, feet, and so on. Compulsive use of a drug/chemical in the face of obvious physical and psychological damage, and it's hard not to notice missing fingers, is a hallmark (not the only one) of addiction.
Excessive temperature will result in the production of VOCs from vape juice. However under normal vape conditions the amounts produced are far less than in cigarette smoke. There are microparticles and even some metals present in vapor but are orders of magnitude lower than in cigarette smoke. There are no nitrosamines. Published data in legit medical journals ( not some website that also discusses how aliens must have built the pyramids) demonstrated that in actual live humans, not an animal or cell culture experiment, VOCs in vapers was dramatically lower than in smokers and nitrosamine products were undetectable. I have to put out there in fairness that dual users of vaping and tobacco showed no reduction in the tested for toxins over smokers alone. No, I can't link the citation as I have a cold, am doing this from bed on my phone, and am in no mood to play the let's search the literature game (I do have the pdf saved somewhere on my computer but I'm not getting out of bed to find it).
Another good medical study on real live people, not cell cultures or rodents, showed that among people with COPD, a common chronic lung disease associated with long term smoking that over a three year period vapers had far fewer acute exacerbations of their illness versus those who continued to smoke.
Is vaping safe? No. However, based on all current known toxicity studies, both in controlled lab experiments and in humans, vaping and any byproducts produced are far less toxic than the smoke from combustible tobacco. That's why vaping is regarded as a harm reduction strategy in reducing smoking, not a healthy lifestyle choice that's better than eating only hormone free, free range chicken.
So to say vaping is as unhealthy as smoking is to ignore a plethora of data available that contradicts that statement. The extent of risk reduction remains to be established. Current views suggest a dramatic reduction of 95% compared to smoking (the whole Royal College of Physicians consensus publication). Is it really that dramatic? We don't know yet. Will it pan out to be that high? My gut probably not, but even a 50% reduction (and I fully expect it to be better than that, just using a worse case scenario) will reduce tobacco related deaths by over three million people over the next twenty years. That's still really good from my perspective.
My personal opinion? If you don't smoke don't vape. If you do smoke and vaping is the only method successful for you to stop smoking (true of many here including myself) vaping wins. I will add a caveat that if I were 30 years old and stopped smoking with vaping I'd be looking for some sort of off ramp from vaping at some point in the future as 30 years of vaping from a young age is probably not the smartest choice, unless it's vape or smoke. At my age I have no interest in stopping vaping. I enjoy it. I've not had a cigarette in almost four years, and if there is done long term grow a second head on my shoulder 30 years from now I'll be too old to worry about it.
tl;dr. Vaping is not as unhealthy as smoking and there is zero scientific evidence to support that position. The scientific evidence to date shows the opposite, vaping is less harmful than smoking.
End of rant.
(I take no credit for all the typos and errors. You can thank my autocorrect for all that stuff. I'm not nearly as creative as autocorrect can be)
