The World Health Organization states that as of July 2013, no rigorous studies have been conducted showing that electronic cigarettes are safe or that they are effective as nicotine replacement therapy.
The British Medical Association states that there is emerging evidence of potential smoking cessation benefits to e-cigarettes, but has concerns that they are subject to inferior regulation versus conventional nicotine replacement methods, and that there is no peer-reviewed evidence of their safety or efficacy. They recommend a "strong regulatory framework" for e-cigarette distribution in order to ensure their safety, quality, and that their marketing and sales are restricted to adults. The BMA encourages health professionals to recommend conventional nicotine replacement therapies, but for patients unwilling to use or continue those methods, they say health professionals may present e-cigarettes as a lower-risk option than tobacco smoking.
A 2011 review published in the Journal of Public Health Policy states that electronic cigarettes may aid in smoking cessation and are likely to be more effective at this than traditional pharmacotherapy. TheAmerican Association of Public Health Physicians (AAPHP) view electronic cigarettes as similar to other nicotine replacement therapy and recommend them as a harm reduction method for those who have failed to quit by other means.
The electronic systems appear to usually deliver less nicotine than smoking.
A preliminary analysis of e-cigarette cartridges by the FDA identified that some contain tobacco-specific nitrosamines (TSNAs), known cancer-causing agents.
The FDA's analysis also detected diethylene glycol, a poisonous and hygroscopic liquid, in one of the cartridges manufactured by Smoking Everywhere and nicotine in some cartridges claimed to be nicotine-free. Further concerns were raised over inconsistent amounts of nicotine delivered when drawing on the device. In some e-cigarettes, "Tobacco-specific impurities suspected of being harmful to humans –anabasine, myosmine, and ß-nicotyrine – were detected in a majority of the samples tested." It is not clear if these chemicals were detectable in exhaled vapour.
The UK National Health Service noted that the toxic chemicals found by the FDA were at levels one thousandth that of cigarette smoke, and that while there is no certainty that these small traces are harmless initial test results are reassuring.
A 2013 UK survey commissioned by Action on Smoking and Health (ASH) found that among non-smokers under 18, 1% reported having tried e-cigarettes "once or twice," 0% reported continuing use, and 0% intended to try them in the future. ASH concluded that among children who have heard of e-cigarettes, sustained use is rare and confined to children who smoke or have smoked