I'm a fairly new vaper and have heard about these chemicals. May I ask, Is this something that is a byproduct of making e juice, or is it an actual ingredient added to it? Also Is it limited mainly to "food" and "desert" type flavors as opposed to tobacco and menthol juices? Going in, I suspected that blindly trusting juice makers (who lets face it can put just about anything they want in their juice) to be automatically safer than real cigs is a bit naive. We want to believe that ecigs are so much safer, but when something is raised about them having an even higher level of a toxin than a real cig, it might be time to take notice. There does need to be more research and safe guards. At the end of the day ecigs will probably be certified as safer than regular cigs- but maybe not by as much as some of us may think. That is only going by how I feel and any physical changes I've noticed since I started vaping and terminated smoking- which is that overall my lungs feel better. The rest of my body, particularly my GI tract and sometimes my head actually feel worse sometimes. My own theory is that vaping tricks your body into digestion mode whether there is food there or not. Also of concern- does PG kill the "good bacteria" in your body? This could seriously compromise your immune system. Does VG raise your glycemic index (A high glycemc index causes inflammation of your body, includng your brain, and also raises risk for diabeties). I cant rule out certain findings as they appear and figure they are just an attack on vaping or some sort of "scare" tactic. As much as I want to, I'm not going to assume its such a way safer thing than real smoking- as it seems to be marketed as- I think it will carry its own set of risks that will be different from those of regular smoking (ie it might significantly reduce risk of lung cancer but raise risk for diabeties and other diseases). Long term effects of vaping are unknown. In addition to toxin levels in ejuice and respitory effects, I'd like to see research focused on 100% VG juice and or food flavored juices and glycemic index, GI tract effects, and changes in "good bacteria" levels (for juices that contain PG).