Is there a risk to non-users from electronic cigarette vapour? Although electronic cigarettes do not produce smoke, users exhale a smoke-like vapour which consists largely of propylene glycol and glycerine. The level of nicotine present in electronic cigarette vapour is about one tenth of that generated by a cigarette. Any health risks of second hand exposure to propylene glycol vapour are likely to be limited to irritation of the throat. One study exposed animals to propylene glycol for 12 to 18 months at doses 50 to 700 times the level the animal could absorb through inhalation. Compared to animals living in normal room atmosphere, no localised or generalised irritation was found and kidney, liver, spleen and bone marrow were all found to be normal.
The fact that many electronic cigarettes look similar to conventional cigarettes has been said to risk confusion as to their use in enclosed public places, such as on public transport. However, given that the most distinctive feature of cigarette smoking is the smell of the smoke, which travels rapidly, and that this is absent from electronic cigarette use, it is not clear how any such confusion would be sustained.
Furthermore, the absence of risk from “second hand” inhalation of vapour from electronic cigarettes has been described as an “often unconsidered advantage” of electronic cigarettes. As an alternative to smoking, electronic cigarettes are preferable in situations where second hand smoke poses serious health risks to others, such as in vehicles or in the home.
Since electronic cigarettes do not involve lighting tobacco, some argue, they should not be included in tobacco regulations—including smoking bans. Instead of toxic smoke, what electronic cigarettes emit is a water vapour that contains propylene glycol (PEG), the same substance used to make theatre smoke. As to whether or not there are any other trace chemicals in that vapour that will harm bystanders, no one is sure yet.