People are using the vape system to smoke weed now too. Those flavorings cover the smell of the pungent weed for the most part.
Vaping is more harmful than originally thought and does cause lung cancer. e-Cigs also typically contain the chemical that's found in so called "non-toxic" antifreeze,
propylene glycol. It's in the same chemical family as alcohol.
That's the stuff you hear about in those investigative reports where a spouse is found to have murdered their significant other using the stuff. It's sweet to the taste but on autopsy its found to leave tiny crystals in the kidneys and elsewhere. Unless a coroner is looking for it it is easy to miss. Which is why those black widows can get away with murder entirely or for years until the case is re-opened.
"SO WHAT HAPPENS AFTER PROLONGED USE OF E-CIGARETTES?
Scientists are still studying these effects, and even though in America the Food and Drug Administration (FDA) has given the seal of approval, much is still unknown.
E-liquid can also differ greatly between manufacturers with barely any regulation for additives. Some have been found to contain diaceftyl, a chemical that is known to give butter its “buttery” taste. Inhalation of this chemical can lead to scarring in the lungs known as “popcorn lung,” named after hundreds of workers who inhaled the chemical in a microwaveable popcorn factory and suffered irreversible lung damage. This is an example of how the lack of quality control in e-cigarettes should be a significant concern.
But, current evidence does indicate that vaporizers administer nicotine with far less adverse effects due to decreased carcinogenic products and smoke inhalation. But less harmful does not mean safe. E-cigarettes with added flavouring (such as blueberry or grape) have been found to contain other harmful chemicals....."
Smoking Vs. Vaping http://www.asapscience.com/blog/2018/5/1/smoking-vs-vaping-which-is-better