Electronic cigarettes are battery-powered vaporizers that simulate the feeling of smoking, but without tobacco. Their use is commonly called "vaping". Instead of cigarette smoke, the user inhales an aerosol, commonly called vapor, typically released by a heating element that atomizes a liquid solution known as e-liquid. The user activates the e-cigarette by taking a puff or pressing a button. Some look like traditional cigarettes, but they come in many variations. Most are reusable but there are also disposable versions called first-generation cigalikes; there are also second, third, and fourth-generation devices. E-liquids usually contain propylene glycol, glycerin, nicotine, and flavorings. Some e-liquids contain ingredients such as cannabis, tobacco extract, or other additives.
The benefits and the health risks of e-cigarettes are uncertain. There is tentative evidence that they can help people quit smoking, but they have not been proven better than regulated medication. Their usefulness in tobacco harm reduction is unclear, but they could form part of future strategies to decrease tobacco related death and disease. Their safety risk to users is similar to that of smokeless tobacco. Regulated nicotine replacement products are safer than e-cigarettes, but e-cigarettes are probably safer than smoking.
Nicotine is associated with a range of harmful effects. Non-smokers who use e-cigarettes risk nicotine addiction and their use may delay or deter quitting smoking. E-cigarettes create vapor consisting of ultrafine particles. The vapor contains similar chemicals to the e-liquid, together with tiny amounts of toxicants and heavy metals. The composition of the vapor varies across and within manufacturers. E-cigarette vapor can contain harmful chemicals not found in tobacco smoke. Later-generation e-cigarettes may generate more formaldehyde than tobacco does, but reduced voltage e-cigarettes produce very low levels of formaldehyde. E-cigarette vapor contains fewer toxic substances than cigarette smoke. It also has lower concentrations of potential toxic substances than cigarette smoke, and is probably less harmful to users and bystanders. No serious adverse effects from e-cigarettes have been reported in trials. Less serious adverse effects include throat and mouth inflammation, vomiting, nausea, and cough. The long-term effects of e-cigarette use are unknown.
The modern e-cigarette arose from a 2003 invention by Hon Lik in China and as of 2015 most devices are made there. Since their introduction to the market in 2004, global usage has risen exponentially. As of 2014, about 13% of American high school students have used them at least once in the last month. As of mid-2015 around 10% of American adults are current users of e-cigarettes. In the UK user numbers have increased from 700,000 in 2012 to 2.6 million in 2015. Most US e-cigarette users still smoke traditional cigarettes. About 60% of UK users are smokers and about 40% are ex-smokers, while use among never-smokers remains "negligible". Most people's reason for using e-cigarettes is related to quitting, but a considerable proportion use them recreationally. Because of the potential relationship with tobacco laws and medical drug policies, e-cigarette legislation is being debated in many countries. The European Parliament passed regulations in February 2014, to come into effect by 2016, standardizing liquids and personal vaporizers, listing ingredients, and child-proofing liquid containers. The US FDA published proposed regulations in April 2014 with some similar measures. As of 2014, there were 466 brands with sales of around $7 billion.