An electronic cigarette (e-cig or e-cigarette), personal vaporizer (PV) or electronic nicotine delivery system (ENDS) is a battery-powered vaporizer which simulates the feeling of smoking, but without tobacco combustion. Their use is commonly called "vaping". The user automatically activates the e-cigarette by taking a puff; other devices turn on by pressing a button manually. They are often cylindrical, but come in many variations. Some e-cigarettes look like traditional cigarettes, but others do not. There are disposable "cigalikes" which are known as first generation cigalikes and there are reusable versions. Instead of cigarette smoke, the user inhales an aerosol, commonly called vapor. E-cigarettes typically have a heating element that atomizes a liquid solution known as e-liquid. E-liquids usually contain propylene glycol, glycerin, water, nicotine, and flavorings. E-liquids are also sold without propylene glycol, without nicotine, or without flavors.
The benefits to users and the health risks of e-cigarettes are uncertain. There is no evidence they are better than regulated medication for quitting smoking, but there is tentative evidence of benefit as a smoking cessation aid. Their usefulness in tobacco harm reduction is unclear, but in an effort to decrease tobacco related death and disease, they have a potential to be part of the strategy. Their safety risk to users is like that of smokeless tobacco. US Food and Drug Administration (FDA)-approved products, such as nicotine inhalers, are probably safer than e-cigarettes. E-cigarettes are probably safer than smoking. While later-generation and "hotter" e-cigarettes (e.g. 5.0 volts) may generate equal or higher levels of formaldehyde than smoking, reduced voltage e-cigarettes generate very low levels of formaldehyde. Nicotine is associated with cardiovascular disease, potential birth defects, and poisoning. There is inadequate research to demonstrate that nicotine is associated with cancer in humans.
Non-smokers who use them risk nicotine addiction. There is no evidence e-cigarettes are regularly used by those who have never smoked. E-cigarette use may delay or deter quitting smoking. E-cigarettes create vapor that consists of ultrafine particles. The vapor contains similar chemicals to the e-liquid, together with tiny amounts of toxicants and heavy metals. Exactly what comprises the vapor varies across and within manufacturers. E-cigarettes contain possibly harmful chemicals that are not found in tobacco. 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.
Since their introduction to the market in 2004, global usage has risen. As of 2012, up to 10% of American high school students had used them at least once, and around 3.4% of American adults as of 2011. In the UK user numbers have increased from 700,000 in 2012 to 2.1 million in 2013. About 60% of UK users are smokers and most others are ex-smokers. Most e-cigarette users still smoke traditional cigarettes. Most peoples' reason for using e-cigarettes is related to quitting, but a considerable proportion use them recreationally. The modern e-cigarette arose from a 2003 invention by Hon Lik in China and as of 2015 most devices are made there. Because of the potential relationship with tobacco laws and medical drug policies, electronic 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. Manufacturers have increased advertising, using marketing techniques like those used to sell cigarettes in the 1950s and 1960s. As of 2014, there were 466 brands with sale of around $7 billion.