[ News >Yale Medicine We also left out propylene glycol, a petroleum byproduct often used as a flavor enhancer. This stuff isn't considered toxic, but it adds a harsh edge to your inhale, and we wanted to stick to strictly plant-based components. I understand that for a few moments during your meal you may have a sniff of my vape that you don’t care for, but I’m sure that it isn’t as horrible as you make it sound in your rant. Life is full of mild unpleasantries that we all must deal with on a daily basis, but we can choose to deal with them or let them torment us. Cigarette smoking is still the No. 1 cause of preventable death in this country, killing nearly five hundred thousand people each year. (According to some studies, more than half of longtime smokers will die from smoking-related complications.) It’s incredibly hard to stop smoking