I'm really concerned about this product. I started with Safe Cig roughly 5 years ago. Then V2. Slowly, V2's became less available in the convenience stores near me. I switched to VUSE. WOW! Heavy stuff! Of course, I'm sucking down 2 of them a day, and finally am worried about what possible side effects could be [beyond a rapid heart rate, etc]. I've had coughing fits that I can't stop. My lungs feel wheezy, at times, and I'm a little concerned about the e-cigs, but too darn hooked to quit! While doing a personal search on benefits and risks to e-cigs, I learned about the Popcorn Lung study. Researchers from Harvard found that the flavoring chemical, diacetyl, when inhaled, was linked to irreversible scarring to their lungs. VUSE lists their ingredients, including "natural and artificial flavors." What are the artificial flavors? I called them directly, and a man named Chris, put me on hold to ask his supervisor. He came back to me and stammered "they are pro..pro...uh, I can't say it." He started to spell "proprietary." Oh! So, they're a secret for only Big Tobacco to know, right??? I asked for his supervisor. He put me on hold, again (1-2 minutes). He then told me I had to give them all of my information (DOB, full name, address) BEFORE transferring me to a supervisor. It made me feel uncomfortable. Once John, the supervisor, answered the phone, he said he could not tell me the proprietary ingredients, but that he would forward the request to the appropriate parties. I also asked him to tell me how much nicotine was in each cartridge. He had to put me on hold again, and finally responded "4.8%." That's 48mg of nicotine per cartridge. I'm sharing my experience with others to see if anyone else has the same side effects (occasional uncontrollable coughing, wheezing) from using VUSE. Please share! And as they refused to tell me the "artificial" flavorings, I must go back to V2's. If they're still around. I'd love to quit, so...maybe this is a good time to start. I don't trust R.J. Reynolds. I'm tempted to send my cartridges to a lab to have them tested.