One thing I find irritating more than anything else is when people bash e-cigs with absolutely no basis. So, I compiled some very basic information that is a good reference for when you run into people like this. For this information, we're going to stay away from well known information, such as the fact that if something is safe to eat it's generally considered safe to vape. Lets start with the ingredients. Propylene Glycol - What helps turn the liquid to vapor. The acute oral toxicity of propylene glycol is very low, and large quant**ies are required to cause perceptible health damage in humans; propylene glycol is metabolized in the human body into pyruvic acid (a normal part of the glucose-metabolism process, readily converted to energy), acetic acid (handled by ethanol-metabolism), lactic acid (a normal acid generally abundant during digestion). PG is considered safe as a food additive for both humans and dogs, but not cats as it leads to a type of anemia. Hamilton, D. J. (1890). Gastric Dyspepsia . The Lancet 2: 306. Vegetable Glycerin - No explanation needed. About as harmful as eating a cuc**ber. Nicotine - This is the only component of liquid that can be considered harmful. Nicotine does exist in higher levels than cigarettes, and many try to say that it is just as harmful as cigarettes due to a misconception that all negative health impacts come from the nicotine in cigarettes. United States Department of Health and Human Services has stated that cigarettes tend to have about 600 chemicals intentionally added to cigarettes, and the process of burning causes over 4,000 chemicals to be released. Among this list is light traces of battery acid, a***nic, ammonia, sewer gasses, candle wax, and industrial solvent. Nicotine by itself is about as dangerous as caffeine. Lots can kill you, but in regular doses there are almost no negative health effects. Flavoring - Generally comes from food flavorings. No additionally carcinogenic properties come from vaporizing (burning is another story) and absorbing into the lungs. Again, about as harmful as skittles. That will cover almost anything people can criticize with e-cigs. The only other argument I've heard is that it contains a***nic. The thing is, that was one company that only sold in china that went bankrupt like 5 years ago.