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An electronic cigarette (e-cig or e-cigarette), personal vaporizer (PV) or electronic nicotine delivery system (ENDS) is a battery-powered vaporizer which simulates tobacco smoking by producing an aerosol that resembles smoke. It generally uses a heating element known as an atomizer, that vaporizes a liquid solution known as e-liquid. E-liquids usually contain a mixture of propylene glycol, vegetable glycerin, nicotine, and flavorings, while others release a flavored vapor without nicotine. Currently marketed e-cigarette devices arose from an invention made in China in 2003. The e-cigarette market has been rapidly expanding.

The benefits and risks of e-cigarette usage are currently uncertain and the matter of some debate among the scientific community. Evidence suggests e-cigarettes are safer than smoking tobacco products, and possibly as safe as other nicotine replacement products but there is insufficient data to draw conclusions about long-term use. Their use has become more frequent in both the US and the UK. Approximately 60% of users are current smokers and the majority of the remainder are ex smokers. Electronic cigarette legislation and public health investigations are currently pending and are being debated in many countries. The European Commission adopted a proposal to revise the European Union Tobacco Products Directive 2001/37/EC requiring standardization of liquids and personal vaporizers, disclosure of ingredients, and child- and tamper-proofing of liquid containers; the US Food and Drug Administration published proposed regulations in April 2014 along similar lines.

Health effects

Smoking cessation

In July 2014, a report developed by the World Health Organization (WHO) for consideration by the signatories of its Framework Convention on Tobacco Control found insufficient evidence to determine an effect of electronic cigarettes on the ability to quit smoking. This report found electronic cigarettes have not been approved for smoking cessation by any government, and current smokers should be encouraged to use approved methods for smoking cessation.

The report did find some expert opinion in the scientific literature that suggested electronic cigarette may have a role for those who have not had success quitting smoking with other methods. A statement previously published by the WHO on July 2013 stated that the effectiveness of electronic cigarettes in aiding smoking cessation had not been demonstrated and recommend that "consumers should be strongly advised not to use" electronic cigarettes unless a reputable national regulatory body has found them safe and effective. The US Government smoking cessation site, smokefree.gov, stated that the efficacy of electronic cigarettes in aiding smoking cessation has not been demonstrated and did not recommend them.

The concept of harm reduction has largely been controversial in the public health approach of tobacco control. A 2011 review article states how electronic cigarettes may aid in smoking cessation and may likely be more effective than traditional pharmacotherapy, as the physical stimuli of holding and puffing on the electronic cigarette may better reduce short-term cravings. The review found no studies that directly measured the effectiveness of electronic cigarettes in smoking cessation, and examined two published studies that indirectly consider the issue by measuring the effect of the product on cravings and other short-term indicators. A 2014 review asserted how electronic cigarettes may be a reasonable substitute for cigarette smoking. The review also states that even individuals that did not intend to quit smoking before being introduced to e-cigarettes may subsequently do so. Another 2014 review concluded that the benefit with respect to helping people quit smoking was uncertain.

The American Association of Public Health Physicians (AAPHP) suggests those who are unwilling to quit tobacco smoking or unable to quit with medical advice and pharmaceutical methods should consider other nicotine containing products such as electronic cigarettes and chewing tobacco for long term use instead of smoking.

The British Medical Association (BMA) reported in 2013 that there was a possibility for smoking cessation benefits, but had concerns that e-cigarettes are less regulated than nicotine replacement therapy (NRT), and that there was no peer reviewed evidence concerning their safety or efficacy. Recommendations point to a "strong regulatory framework" for e-cigarette distribution in order to ensure the safety, quality, and that 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 using such methods, health professionals may present e-cigarettes as a lower-risk option than tobacco smoking.

A report commissioned by Public Health England concluded that there is large potential for health benefits when switching from tobacco use to other nicotine delivery devices such as electronic cigarettes, but realizing the full potential requires regulation and monitoring to minimize possible risks.

A 2012 review found electronic systems appear to generally deliver less nicotine than smoking, raising the question of whether they can effectively substitute for tobacco smoking over a long-term period.

A 2013 randomized controlled trial found no difference in smoking cessation rates between e-cigarettes with nicotine, e-cigarettes without nicotine and traditional NRT patches. There are some non-controlled studies which have reported possible benefit.

Electronic cigarettes were not regularly associated with trying to quit tobacco among young people. Adults most often used electronic cigarettes as a replacement for tobacco, although not invariably to quit. The majority of e-cigarette users continue to smoke traditional cigarettes. The majority of youth using e-cigarettes are dual users, though some youth who used an e-cigarette have never tried a traditional cigarette. Although some people have a desire to quit smoking by using e-cigarettes, other common explanations for the use of these products are to reduce harm from smoking, and to cut back on traditional cigarettes, which may reinforce delaying or deterring to quit smoking.

Safety

The risks of electronic cigarette use are uncertain. This is due to there being little data regarding their health effects and to the variability of vaporizers and variability in liquid ingredients and in their concentration and quality, and thus variability of the contents of aerosol delivered to the user. However, some evidence suggests e-cigarettes may be safer than smoking tobacco products, and possibly as safe as other nicotine replacement products but there is insufficient data to draw conclusions. Switching from smoking tobacco to using e-cigarettes may result in reduced exposure to nicotine and reduced potential risk of disease from smoking.

A preliminary analysis of e-cigarette cartridges by the US Food and Drug Administration (FDA) in 2009 identified that some contain tobacco-specific nitrosamines (TSNAs), known cancer-causing agents. The amounts of TSNAs present were on par with existing NRT products like nicotine gum and inhalers. The FDA's analysis also detected diethylene glycol, a poisonous and hygroscopic liquid, in a single cartridge manufactured by Smoking Everywhere and nicotine in one cartridge claimed to be nicotine-free. Diethylene glycol was found in a cartridge tested in 2009 by the FDA, but in 2011 researchers reviewed the data and noted that 15 other studies had failed to find any evidence of this chemical in e-cigarettes. 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 β-nicotyrine – were detected in a majority of the samples tested." 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. While propylene glycol and other chemicals commonly used as solvents or carrier compounds in e-cigarettes liquids are generally recognized as safe, they have not been used before in vaporized form over long periods of time. The risks, especially to the lungs, are not fully understood and are of concern to public health authorities and some reviewers. Some reviewers have noted that while there is variability in the ingredients and concentrations of ingredients in e-cigarette liquids, tobacco smoke contains thousands of chemicals, most of which are not understood and many of which are known to be harmful.

A report by WHO from August 2014 cautioned about potential risks of using electronic cigarettes. Passive exposure was also mentioned as a concern with the report, indicating that current evidence is insufficient to determine whether the levels of exhaled aerosol are safe to involuntarily exposed bystanders. Rare major injuries have occurred from battery malfunctions such as explosions and fires. Less serious adverse events of e-cigarette use included throat and mouth inflammation, cough, nausea, and vomiting. Liquids used with e-cigarettes also pose a risk if they are ingested or if the skin is exposed to them, especially for children. In the US, the number of calls to poison control centers associated with e-cigarette liquid rose from one per month in September 2010 to 215 per month in February 2014; the proportion related to e-cigarettes jumped from 0.3 percent in September 2010 to 41.7 percent in February 2014. More than half (51.1 percent) of the calls to poison centers due to e-cigarettes involved children under 5 years old.

Second hand vapor

Generally e-cigarette aerosol has notably fewer toxicants than cigarette smoke (other than particulates) and is likely to pose less harm to others. Studies found e-cigarettes emissions put into the air known carcinogens, ultrafine particles, and heavy metals. Studies funded by the e-cigarette industry and e-cigarette proponents have concluded the levels are not of significant health concern for human exposures.

Addiction

It is not clear whether using e-cigarettes will decrease or increase overall nicotine addiction. A number of organizations have concerns that e-cigarettes might increase addiction to and use of nicotine and tobacco products in children. This including: the Centers for Disease Control and Prevention, the International Union Against Tuberculosis and Lung Disease, the American Academy of Pediatrics and the Food and Drug Administration. The World Health Organization raised concern of addiction for nonsmokers from their use in July 2013. There is currently no evidence that they are used regularly by those who have never smoked.

Construction

Most electronic cigarettes take an overall cylindrical shape although a wide array of shapes can be found: box, pipe styles etc. First generation electronic cigarettes were usually designed to simulate smoking implements, such as cigarettes or cigars, in their use and appearance. New generation electronic cigarettes often called mods, PV's (personal vaporizer) or APV's (advanced personal vaporizer) have an increased nicotine-dispersal performance, housing higher capacity batteries, and come in various form factors, including metal tubes and boxes. Many electronic cigarettes are composed of standardized replaceable parts that are interchangeable from one brand to the other, while disposable devices combine all components into a single part that is discarded when its liquid is depleted. Common components include a liquid delivery and container system like tanks or cartomizers, an atomizer, and a power source.

Atomizer

An atomizer generally consists of a small heating element responsible for vaporizing e-liquid, as well as a wicking material that draws liquid in. Along with a battery, the atomizer is the central component of every personal vaporizer. Differences between atomizers cause differences in the ingredients and their concentrations delivered to users, even when the same liquid is used.

A small length of resistance wire is coiled around the wicking material and then connected to the positive and negative poles of the device. When activated the resistance wire (or coil) quickly heats up thus turning the liquid into a vapor, which is then inhaled by the user.

The electrical resistance of the coil, the voltage output of the device, the airflow of the atomizer and the efficiency of the wick play important roles in the perceived quality of the aerosol that is produced by an atomizer. They also greatly affect the quantity or volume of aerosol that will be produced by the atomizer.

Atomizer resistances usually vary from 1.5Ω (ohms) to 3.0Ω from one atomizer to the next but can go as low as 0.1Ω in the most extreme cases of DIY coil building which produce large amounts of vapor but could present a fire hazard and other dangerous battery failures if the user is not knowledgeable enough about basic electrical principles and how they relate to battery safety.

Wicking materials vary greatly from one atomizer to another but silica fibers are the most commonly used in manufactured atomizers. "Rebuildable" or "do it yourself" atomizers can use silica, cotton, porous ceramic, hemp, bamboo yarn, oxidized stainless steel mesh and even wire rope cables as wicking materials.

A wide array of atomizers and e-liquid container combinations are available:

Cartomizers

A "cartomizer" (a portmanteau of cartridge and atomizer) or "carto" consists of an atomizer surrounded by a liquid-soaked poly-foam that acts as an e-liquid holder. It is usually disposed of once the e-liquid acquires a burnt taste, which is usually due to an activation when the coil is dry or when the cartomizer gets consistently flooded (gurgling) because of sedimentation of the wick. Most cartomizers are refillable even if not advertised as such.

Cartomizers can be used on their own or in conjunction with a tank that allows more e-liquid capacity. In this case the portmanteau word of "carto-tank" has been coined. When used in a tank, the cartomizer is inserted in a plastic, glass or metal tube and holes or slots have to be punched on the sides of the cartomizer to allow liquid to reach the coil.

Clearomizers

Clearomizers or "clearos", not unlike cartotanks, use a clear tank in which an atomizer is inserted. Unlike cartotanks, however, no poly-foam material can be found in them. There are a lot of different wicking systems employed inside of clearomizers to ensure good moistening of the wick without flooding the coil. Some rely on gravity to bring the e-liquid to the wick and coil assembly (bottom coil clearomizers for example) whereas others rely on capillary action and to some degree the user agitating the e-liquid while handling the clearomizer (top coil clearomizers).

Rebuildable atomizers

A rebuildable atomizer or an RBA is an atomizer that allows the user to assemble or "build" the wick and coil themselves instead of replacing them by an off-the-shelf atomizer "head". They also allow the user to build atomizers at any desired electrical resistance. The materials needed to "rebuild" the atomizers are usually much cheaper than the usual prefabricated replaceable wick and coil assemblies destined to clearomizers.

These atomizers are divided into two main categories; rebuildable tank atomizers (RTA's) and rebuildable dripping atomizers (RDA's).

Rebuildable tank atomizers or RTA's are similar to clearomizers in that they use a tank or container to hold and bring liquid to the coil. They usually hold a lot more e-liquid than their RDA counterparts.

Rebuildable dripping atomizers or RDA's on the other hand lack the container section and hold very little liquid compared to RTA's but are usually a lot smaller. They usually consist only of an atomizer "building deck" which can accept one or more coils and a "top cap" to cover the coils where a mouth piece can be attached. The user needs to manually keep the atomizer wet by dripping liquid on the bare wick and coil assembly, hence their name.

Power

Most portable devices contain a rechargeable battery, which tends to be the largest component of an electronic cigarette. The battery may contain an electronic airflow sensor whereby activation is triggered simply by drawing breath through the device, while other models employ a power button that must be held during operation. An LED to indicate activation may also be employed. Some manufacturers also offer a cigarette pack-shaped portable charging case (PCC), which contains a larger battery capable of charging e-cigarettes. Devices aimed at more experienced users may sport additional features, such as variable power output and support of a wide range of internal batteries and atomizer configurations and tend to stray away from the cigarette form factor. Some cheaper recent devices use an electret microphone with a custom IC to detect airflow and indicate battery status on the included blue LED.

Variable power and voltage devices

Variable voltage or power personal vaporizers are devices that contain a built in electronic chip that allows the user to adjust the power that goes through the heating element. They usually incorporate a LED screen to display various information. Variable PV's eliminate the need of having to replace an atomizer with another one of lower or higher electrical resistance to change the intensity of the vapor. They also feature voltage regulation and some battery protection.

Some of these devices offer additional features through their menu system such as: atomizer resistance checker, remaining battery voltage, puff counter, activation cut-off etc.

Mechanical personal vaporizers

Mechanical PVs or mechanical "mods", often called "mechs" are devices without electronic components and battery protection (apart from vent holes drilled in some mechanical devices) or voltage regulation. Because there is neither protection nor regulation, they will work either way the battery is inserted. They are activated by spring loaded or opposing magnetic mechanical switches, hence their name. They rely entirely on the natural voltage output of a battery.

They are commonly used with "low resistance" (1.0Ω ~ 0.2Ω) rebuildable atomizers. Seeing that most e-cigarettes containing electronic battery protection will interpret sub ohm resistance coils as a short circuit, thus prohibiting the device from being activated, mechanical mods are among the only devices that will accept such atomizer resistances although more recent (2013) electronic devices offers this possibility as well

Since mechanical PVs are unregulated and unprotected, they require special attention on the user's part that other regulated and protected PVs do not need. Making sure that the battery does not over-discharge and that the atomizer will not require more amperage than what the battery can safely allow are the user's responsibilities.

E-liquid

E-liquid, e-juice or simply "juice", refers to a liquid solution that produces an aerosol when heated by an atomizer. The main ingredients of e-liquids are usually a mix of propylene glycol (PG), vegetable glycerin (VG), and/or polyethylene glycol 400 (PEG400), sometimes with differing levels of alcohol mixed with concentrated or extracted flavorings; and optionally, a variable concentration of tobacco-derived nicotine. There is variability in the purity, kinds and concentrations of chemicals used in liquids, and significant variability between labeled content and concentration and actual content and concentration.

The solution is often sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own eJuices. Components are also available individually and consumers may choose to modify or boost their flavor, nicotine strength, or concentration with various offerings. Pre-made e-liquids are manufactured with various tobacco, fruit, and other flavors, as well as variable nicotine concentrations (including nicotine-free versions). The standard notation "mg/ml" is often used in labeling for denoting nicotine concentration, and is sometimes shortened to a simple "mg".

Usage

Electronic cigarette sales increased from 50,000 in 2008 to 3.5 million in 2012. Most people who use electronic cigarettes have a history of smoking cigarettes while some young people who have never smoked cigarettes have tried electronic cigarettes at least once. The majority of e-cigarette users continue to smoke traditional cigarettes.

In the United States, as of 2011, one in five adults who smoke have tried electronic cigarettes and 3.3% are currently using them. Among grade 6 to 12 students in the United States, those who have at least once used the product increased from 3.3% in 2011 to 6.8% in 2012. and those currently using electronic cigarettes increased from 0.6% to 1.1%. Over the same period the percentage of grade 6 to 12 students who regularly smoke tobacco cigarettes fell from 7.5% to 6.7%. The frequency of use has increased with up to 10% of American high school students having ever used them as of 2012. In 2013 the CDC found a three fold increase from 2011 in the number of youth who have used electronic cigarettes who have never smoked.

In the UK in 2014, 18% of regular smokers identified themselves as using electronic cigarettes and 51% stated that they had used them in the past. Among those who had never smoked, 1.1% said they had tried them and 0.2% continue to use them. In 2013, among those under 18, 7% have used e-cigarettes at least once. Among non-smokers children, 1% reported having tried e-cigarettes "once or twice," and there was no evidence of continued use. Sustained was mostly confined to children who smoke or have smoked. In 2014 child regular users was at 1.8%, children who have ever used e-cigarettes was at 10%, and occasional or greater use among never smoking children was at 0.18%.

A February 2014 survey estimated that between 7.7 and 9.2 million individuals have experimented with using electronic cigarettes, with between 1.1 and 1.9 million using on a daily basis. 67% of tobacco smokers in the survey used electronic cigarettes to reduce or quit tobacco smoking. 9% of those who experimented with electronic cigarettes had never smoked tobacco. Of the 1.2% that had recently stopped tobacco smoking at the time of the survey, 84% (or 1% of the population surveyed) credited electronic cigarettes for stopping tobacco use.

History

The earliest electronic cigarette can be traced to Herbert A. Gilbert, who in 1963 patented a device described as "a smokeless non-tobacco cigarette" that involved "replacing burning tobacco and paper with heated, moist, flavored air". This device heated the nicotine solution and produced steam. It was never commercialized.

Hon Lik, a Chinese pharmacist, is credited with the invention of the electronic cigarette. In 2003, he came up with the idea of using a piezoelectric ultrasound-emitting element to vaporise a pressurized jet of liquid containing nicotine diluted in a propylene glycol solution. This design produces a smoke-like vapour that can be inhaled and provides a vehicle for nicotine delivery into the bloodstream via the lungs. He also proposed using propylene glycol to dilute nicotine and placing it in a disposable plastic cartridge which serves as a liquid reservoir and mouthpiece.

Electronic cigarettes using a different design were first introduced to the Chinese domestic market in May 2004 as an aid for smoking cessation and replacement. The company that Hon Lik worked for, Golden Dragon Holdings, changed its name to Ruyan (如烟, literally "Resembling smoking"), and started exporting its products in 2005–2006 before receiving its first international patent in 2007. E-cigarette devices are predominately manufactured in China. The e-cigarette brands have been rapidly expanding using aggressive marketing campaigns similar to those used to popularize cigarettes in the 1950s and 1960s. Long banned comparative advertising for cigarettes and other tobacco products, e-cigarette advertising on television and radio in a number of countries may be indirectly advocating traditional cigarette smoking.

The electronic cigarette continued to evolve from the first generation three-part device. In 2006 the "cartomizer" was invented by British entrepreneurs Umer and Tariq Sheikh of XL Distributors. This is a mechanism which integrates the heating coil into the liquid chamber. The new device was launched in the UK in 2007 in their Gamucci brand and is now widely adopted by the majority of 'cigalike' brands. The grant of the UK patent for the "cartomizer" was made to XL Distributors in February 2013 and published by the UK Intellectual Property Office.

The international tobacco companies, recognising the development of a potential new market sector that could render traditional tobacco products obsolete, are increasingly involved in the production and marketing of their own brands of e-cigarettes and in acquiring existing e-cigarette companies. Blu, a prominent US e-cigarette producer, was acquired by Lorillard Inc. in 2012. British American Tobacco launched Vype in 2013, while Imperial Tobacco's Fontem Ventures acquired the intellectual property owned by Hon Lik through Dragonite for $US 75 million in 2013 and launched Puritane in partnership with Boots UK. On October 1, 2013 Lorillard Inc. acquired another e-cigarette company, this time a UK based company SKYCIG. On 3 February 2014, Altria Group, Inc. acquired popular electronic cigarette brand Green Smoke for $110 million. The deal was finalized in April 2014 for $110 million and $20 million in incentive payments. Altria also markets its own e-cigarette, the MarkTen, while Reynolds American has entered the sector with its Vuse product.

Society and culture

Consumers of electronic cigarettes or "vapers" as some call them have shown evident and passionate support for the product that other nicotine replacement therapy did not receive, suggesting that these products have the potential mass appeal that could challenge the preeminence of combustible tobacco as the object of choice for nicotine users.

As the electronic cigarette industry grows, a subculture has emerged which calls itself "the vaping community". Members of this emerging subculture often view electronic cigarettes as a safer alternative to smoking and some even view it as a hobby. They tend to use highly customized devices that do not resemble what are known, by some, as "cig-a-likes," or electronic cigarettes that resemble real cigarettes.

Large gatherings of vapers are happening around the United States which focus around e-cig devices, accessories, and the life style that accompanies it. People attending these meetings are usually enthusiasts that use specialized, community-made products that are not found in typical places like convenience stores or gas stations. These products are mostly available online or in dedicated "vape" storefronts where mainstream e-cigarettes brands from the tobacco industry and larger e-cig manufacturer are not available.

A growing subclass of vapers assemble their atomizers in such a way that can produce extremely large amounts of vapor, this practice is known as "cloud-chasing" and individuals who engages in this activity are referred to as "cloud-chasers". This practice stresses the batteries of PV's considerably more than what could be considered regular use and could represent a risk of dangerous battery failures. As vaping comes under more and more scrutiny, some members of the vaping community have voiced their concerns about cloud-chasing claiming the practice gives vapers a bad reputation when doing it in public.

Legal status

The emerging phenomenon of electronic cigarettes has raised concerns among the health community, pharmaceutical industry, health regulators and state governments. Some jurisdictions are now prohibiting or regulating the use of e-cigarettes in public spaces.

Because of the relative novelty of the technology and the possible relationship to tobacco laws and medical drug policies, electronic cigarette legislation and public health investigations are currently pending in many countries. Current regulations vary widely, from regions with no regulations to others banning the devices entirely.

In February 2014 the European Parliament passed regulations requiring standardization and quality control for liquids and vaporizers, disclosure of ingredients in liquids, and child-proofing and tamper-proofing for liquid packaging. In April 2014 the US FDA published proposed regulations for e-cigarettes along similar lines.

In March 2014 Western Australia banned sale of electronics cigarettes.

Economics

According to Nielsen Holdings, convenience store e-cigarette sales went down for the first time during the four-week period ending on 10 May 2014. This decline is attributed by Wells Fargo analyst Bonnie Herzog to a shift in consumers behavior, buying more specialized devices or what she refers to as "vapor/tank/mods (VTM's)" that are not tracked by Neilsen. According to Herzog these products, produced and sold by stand alone makers are now (2014) growing 2 times faster than traditional electronic cigarettes marketed by the major players (Lorillard, Logic Technology, NJOY etc...) and account for a third of the 2.2 billion dollar market for vapor products.

Related technologies

There are other technologies currently under development that seek to deliver nicotine for oral inhalation in an effort to mimic both the ritualistic and behavioural aspects of traditional cigarettes.

• British American Tobacco, through their subsidiary Nicoventures Limited, licensed a nicotine delivery system based on existing asthma inhaler technology from UK-based healthcare company Kind Consumer Limited. In September 2014 a product based on this - named Voke - obtained approval from the United Kingdom's Medicines and Healthcare Products Regulatory Agency.
• Philip Morris International bought the rights to a nicotine pyruvate technology developed by Jed Rose at Duke University. The technology is based on the chemical reaction between nicotine acid and a base, which produces an inhalable nicotine pyruvate vapour.
• Heatsticks which heats tobacco.

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External links

• Media related to Electronic cigarettes at Wikimedia Commons
• "Smokefree Lists, Maps, and Data", Americans for Nonsmokers' Rights

• 2003 introductions
• Chinese inventions
• Smoking cessation
• Technology