Electronic cigarette - Wikipedia, the free encyclopedia

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1 Electronic cigarette From Wikipedia, the free encyclopedia An electronic cigarette (e-cig or e-cigarette), personal vaporizer (PV) or electronic nicotine delivery system (ENDS) is a battery-powered vaporizer which produces a similar feel to tobacco smoking. [1] Electronic cigarettes produce an aerosol, commonly called vapor, rather than cigarette smoke, which the user inhales. [2] In general, e-cigarettes have a heating element that atomizes a liquid solution known as e-liquid. [3] They are available as one-time use products or as reusable products. [4] E-liquids usually contain a mixture of propylene glycol, glycerin, nicotine, and flavorings. [5] E-liquid containing glycerin and water made without propylene glycol is also available. [6] Some e-liquids lack nicotine. [7] A first generation electronic cigarette resembling a tobacco cigarette. The benefits and health risks of electronic cigarettes are uncertain. [4][8] One review found limited evidence of a benefit as a smoking cessation aid. [9] Another found no evidence that they are superior to regulated medications for quitting smoking. [8] Their usefulness in tobacco harm reduction is unclear. [10] One review approximated their safety risk to that of smokeless tobacco which has about 1% of the mortality risk of conventional cigarettes. [11] Another found that products approved by the United States Food and Drug Administration (FDA), such as nicotine inhalers, are probably safer than e-cigarettes. [10] A later-generation PV. Limited evidence suggests e-cigarettes are safer than traditional cigarettes. [12] Electronic cigarettes may carry a risk of addiction for those who do not already smoke. [13] There is no evidence they are regularly used by those who have never smoked. [14] E-cigarette use may delay or deter quitting smoking. [5] Their emissions may contain ultrafine particles, aroma transporters, propylene glycol, glycerin, nicotine, tiny amounts of carcinogens and heavy metals, and other chemicals. [5][14] E-cigarette vapor contains fewer toxic substances than cigarette smoke, [5] and is likely to be less harmful than traditional cigarettes to users and bystanders. [5][14] No serious adverse effects from e-cigarettes have been reported in trials. [9] Less serious adverse effects include throat and mouth inflammation, vomiting, nausea, and cough. [5] The long-term effects of e-cigarette use are unknown. [15][16] Use has risen, with up to 10% of American high school students having used them at least once as of 2012, and around 3.4% of American adults as of [17] In the United Kingdom the number of users has increased from 700,000 in 2012 to 2.1 million in About 60% of UK users are smokers and most of the rest are ex-smokers. [18] Most e-cigarette users still smoke traditional cigarettes. [5] Most peoples' reason for using e-cigarettes is related to quitting, with a considerable 1 of 34 27/04/15 10:55 AM

2 proportion using them recreationally. [16] The modern e-cigarette arose from a 2003 invention by Hon Lik in China [19] and as of 2014 most devices are made there. [5] E-cigarette brands have increased their advertising, using marketing techniques like those used to sell cigarettes in the 1950s and 1960s. [5] Because of the potential relationship with tobacco laws and medical drug policies, electronic cigarette legislation is being debated in many countries. [20][21] The European Parliament passed regulations in February 2014 standardizing liquids and personal vaporizers, listing ingredients, and child-proofing liquid containers. [22] The US FDA published proposed regulations in April 2014 with some similar measures. [23] Contents 1 Use 1.1 Motivation for use 2 Construction 2.1 Device generations 2.2 Atomizer 2.3 Power 2.4 E-liquid 3 Health effects 3.1 Position of medical organizations 3.2 Smoking cessation 3.3 Harm reduction 3.4 Safety 3.5 Addiction 4 History 5 Society and culture 5.1 Legal status 5.2 Economics 6 Related technologies 7 References 8 External links Use Electronic cigarette sales increased from 50,000 in 2008 to 3.5 million in [24] Electronic cigarette sales worldwide for 2014 were estimated at $7 billion. [25] Awareness and use of e-cigarettes has greatly increased over the few years before 2014, particularly among young people and women in some countries. [26] People with high-income are more likely to have herd of e-cigarettes, but 2 of 34 27/04/15 10:55 AM

3 Common reasons people use the e-cigarette is a desire to quit smoking cigarettes, cut down on their smoking habit or for use where smoking is prohibited by law. [5] people with low-income are typically more inclined to have tried them. [17] Trying e-cigarettes was common with less educated people. [26] Whites are more likely than non-whites to use them. [17] Most users have a history of smoking normal cigarettes. [17] Some young people who have never smoked normal cigarettes have tried electronic cigarettes at least once. [17] The majority of e-cigarette users use them every day. [27] E-cigarette users mostly keep smoking traditional cigarettes. [5] Many users say e-cigarettes help them cut down or quit smoking. [14] Adults most often use e-cigarettes to replace tobacco, but not always to quit. [17] Most e-cigarette users are middle-aged males who also smoke traditional cigarettes, either to help them quit or for recreational use. [16] The percentage of the use of e-cigarettes during pregnancy is unknown, but if companies persuade women that these devices present a minor risk females of reproductive age not smoking might start using e-cigarettes and pregnant women currently smoking might shift to e-cigarettes or use these devices to reduce smoking, instead of quitting tobacco altogether. [28] Among females, e-cigarette use is rising sharply. [28] E-cigarette use is rising among females of childbearing age. [29] Although some people want to quit smoking using e-cigarettes, other reasons for using them are to circumvent smoke-free laws and policies, and to cut back on the number of traditional cigarettes smoked. [5] The extent to which traditional cigarette users use e-cigarettes to avoid smoking bans is unclear. [27] Dual use of e-cigarettes and traditional tobacco is still a definite concern. [4] Many worry that e-cigarettes may function as a "gateway" to using traditional cigarettes. [30] Ethical concerns exist about e-cigarettes use among minors and their potential to weaken efforts to reduce the use of traditional cigarettes. [30] In the United States, as of 2011, one in five adults who smoke have tried electronic cigarettes and 3.3% are currently using them. [17][31] 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 [17] 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%. [32] The frequency of use has increased with up to 10% of American high school students having ever used them as of [17] In 2013 the CDC found a threefold increase from 2011 in the number of youth who have used electronic cigarettes who have never smoked. [33] Between 2013 and 2014, use of electronic cigarettes among American teenagers tripled. [34] The limited data suggests that e-cigarette use is rapidly growing among adolescents. [35] The majority of youth who use e-cigarettes also smoke combustible cigarettes. [36] E-cigarette use among never-smoking youth in the U.S. is correlated with an elevated desire to use traditional cigarettes. [4] 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. [37] Among those who had never smoked, 1.1% said they had tried them and 0.2% continue to use them. [37] In 2013, among those under 18, 7% have used e-cigarettes at least once. [37] Among non-smokers' children, 1% reported having tried e-cigarettes "once or twice", and there was no evidence of continued use. [37] Sustained use was mostly confined to children who smoke or have smoked. [37] In 2014 child regular users was at 1.8%, 3 of 34 27/04/15 10:55 AM

4 children who have ever used e-cigarettes was at 10%, and occasional or greater use among neversmoking children was at 0.18%. [38] About 60% are smokers and most of the rest are ex-smokers. [18] A February 2014 survey in France estimated that between 7.7 and 9.2 million people have tried e-cigarettes, with between 1.1 and 1.9 million using them on a daily basis. 67% of tobacco smokers in the survey used e-cigarettes to reduce or quit tobacco smoking. 9% of those who tried e-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 e-cigarettes for stopping tobacco use. [39] Larger numbers of young people are starting to use e-cigarettes. A high number of youths who use e-cigarettes also smoking traditional cigarettes. Some youths who have tried an e-cigarette have never smoked a traditional cigarette; this indicates that they can be a starting point for nicotine use for some youths. There are high levels of dual use with e-cigarettes and traditional cigarettes. [5] E-cigarettes were not regularly associated with trying to quit tobacco among young people. [17] Motivation for use There are varied reasons for e-cigarette use. Studies suggest most users' motivation is related to quitting, but a considerable proportion of use is recreational. [16] Reasons for trying e-cigarettes are partly due to curiosity and experimentation rather than ongoing use. [40] Some vapers use e-cigarettes for the enjoyment. [27] Many users assume that e-cigarettes are healthier than traditional cigarettes for personal use or for other people. [27] Some users are concerned about the possible adverse health effects or toxicity of e-cigarettes. [27] Traditional cigarette users who have not used e-cigarettes had mixed ideas about their possible satisfaction and around one third thought that e-cigarettes might taste bad. [27] Vapers disagreed whether it was a benefit or a drawback regarding the way they feel or taste similar to traditional cigarettes. [27] Some traditional cigarette users and e-cigarette users liked that e-cigarettes resembled traditional cigarettes, whereas others thought this was a drawback. [27] E-cigarettes users' views about saving money from using e-cigarettes compared to traditional cigarettes are inconsistent. [27] The majority of committed e-cigarette users interviewed at an e-cigarette convention found them less costly compared to traditional cigarettes. [27] Some users stopped using e-cigarettes due to issues with the devices. [27] Not having odor from smoke on clothes on some occasions prompted interest in or use of e-cigarettes. [27] E-cigarette users have contradictory views about using them to get around smoking bans. [27] Some surveys found that a small percent of the users' motives was to avoid the bans but other surveys found that over 40% of users stated they used the device for this reason. [27] A 2014 review found "Health-related and lifestyle appeals may also encourage initiation among young non-smokers, as they may convey that trying e-cigarettes is less risky and more socially appealing, which may ameliorate negative beliefs or concerns about nicotine addiction." [41] Infants and toddlers could ingest the e-liquid from an e-cigarette device out of curiosity. [42] Many users might begin with using a disposable e-cigarette as a starting point. [7] E-cigarette users often begin by using an e-cigarette device resembling a cigarette and eventually most of them switched to a later-generation device. [43] Most users of later-generation e-cigarettes shifted to their present model with the intent of getting a "more satisfying hit". [43] Many users enjoy adjusting their devices to provide greater amounts of vapor for better throat hits. [44] 4 of 34 27/04/15 10:55 AM

5 Construction E-cigarettes are generally roughly cylindrical, with many variations: pen-styles, tank-styles etc. [5] There are three main categories of e-cigarettes: cigalikes, looking like cigarettes; egos, bigger than cigalikes with refillable liquid tanks; and mods, assembled from basic parts or by altering existing products. [4] E-cigarettes are also available that resemble pens and USB memory sticks for those who may want to use the device unobtrusively. [26] First generation electronic cigarettes usually simulated smoking implements, such as cigarettes or cigars, in their use and appearance. [45] Later-generation electronic cigarettes often called mods, PVs (personal vaporizer) or APVs (advanced personal vaporizer) have an increased nicotine-dispersal performance, [45] housing higher capacity batteries, [46] and come in various form factors, including metal tubes and boxes. [46][47][48] Many electronic cigarettes are composed of standardized replaceable parts that are interchangeable from one brand to the other. [49] Common components include a liquid delivery and container system like tanks or cartomizers, an atomizer, and a power source. [50] A wide array of component combinations exist. [51] The main parts for majority of e-cigarettes include an aerosol generator, flow sensor, battery, and a liquid storage chamber. [52] They contain silver, steel, metals, ceramics, plastics, fibers, aluminum, rubber and spume, and lithium batteries. [52] Disassembled cigarette-styled electronic cigarette. A. LED light cover B. battery (also houses circuitry) C. atomizer (heating element) D. cartridge (mouthpiece) A disposable e-cigarette. E-cigarettes are available as one-time use products or as reusable products. [4] Disposable e-cigarettes are discarded once the liquid in the cartridge is used up, while rechargeable e-cigarettes may be used indefinitely. [30] Reusable e-cigarettes are refilled by hand or exchanged for pre-filled cartridges, and general cleaning is required. [15] A wide range of disposable and reusable e-cigarettes exist. [53] Disposable e-cigarettes are available for a few dollars, and higher priced reusable e-cigarettes involve an up front investment for a starter kit. [27] Once the user inhales, the airflow activates the sensor, and then the heating element atomizes the liquid solution inside the cartridge into vapor. [16] Other e-cigarettes have a manual push-button switch to turn on the device. [46] Some e-cigarettes have a light-emitting diode at the tip to resemble the glow of burning tobacco. [7] The light-emitting diode may also indicate the battery status. [1] A traditional cigarette is smooth and light, while an e-cigarette can be rigid and a bit bulky. [1] In comparison to traditional cigarettes, the general e-cigarette puff time was much longer, and e-cigarette use needed a more forceful suction. [54] Device generations First generation 5 of 34 27/04/15 10:55 AM

6 First generation e-cigarettes tend to look like tobacco cigarettes and so are called "cigalikes". [45] They may be a single unit comprising a battery, coil and filling saturated with e-juice in a single tube to be used and discarded after the battery or e-liquid is depleted. [45] They may also be a reusable device with a battery and cartridge called a cartomizer. [55] The cartomizer cartridge can be separated from the battery so the battery can be charged and the empty cartomizer replaced when the e-juice runs out. [45] The battery may contain an electronic airflow sensor triggered by drawing breath through the device. Other models use a power button that must be held during operation. [55] An LED in the Aerosol (vapor) exhaled by a first generation e-cigarette user. power button or on the end of the device may also show when the device is firing. [56] Charging is commonly accomplished with a USB charger that attaches to the batteru. [57] Some manufacturers also have a cigarette pack-shaped portable charging case (PCC), which contains a larger battery capable of recharging the individual e-cigarette batteries. [58] Reusable devices can come in a kit that contains a battery, a charger, and at least one cartridge. [58] Varying nicotine concentrations are available and nicotine delivery to the user also varies based on different cartomizers, e-juice mixtures, and power supplied by the battery. These manufacturing differences, creates differences in the way e-cigarettes convert the liquid solution to an aerosol, and thus the levels of ingredients, that are delivered to the user and the surrounding air for any given liquid. [5] Second generation Second generation devices tend to be used by more experienced users. [55] These devices are larger overall and look less like tobacco cigarettes. [55] They have larger non removable batteries with higher capacity. [45] They are charged with a USB charger that attaches to the battery with a threaded connection. Some batteries have a "passthrough" feature so they can be used even while they are charging. [59] Second generation devices are usually two part devices with a tank and a separate battery. Because the tank can be refilled and the battery recharged, the cost of operation is lower. [45] Second generation e-cigarettes commonly use a tank or a "clearomizer". [55] The clearomizer tanks are meant to be refilled with e-juice. [45] They can also be used with cartomizers which are pre-filled. [45] Some Second generation PV. cheaper batteries use a microphone that detects the vibration of the air passing through to activate the device when the user inhales. [60] Other batteries like the ego style can use a custom integrated circuit with a button for manual activation and battery status indicated on the included LED. [60] The power button can also used to turn the battery off and on so it is not activated accidentally. [61] These batteries may also have adjustable power or voltage. [55] Third generation Third generation devices include mechanical mods and variable voltage devices. The battery sections are commonly called "mods," referencing their history of user-modification. [45] These devices are 6 of 34 27/04/15 10:55 AM

7 commonly either cylindrical or a box-shaped. [62] They can be made of wood, aluminium, stainless steel, or brass. [62] A larger "box mod" can hold larger and sometimes multiple batteries. [62] Mechanical mods and variable devices use larger batteries than those found in previous generations. [63] The battery is often replaceable. This allows the user to change to a new battery when one is depleted. Variable devices often have a USB connector for recharging and some can be used while charging which is referred to as a "passthrough" feature. [59][64] Mechanical mods do not have built in chargers because they do not contain integrated circuits, only a switch that connects the atomizer to the battery. The battery must be removed and charged with an external charger. Common battery sizes used in mechanical mods and variable wattage devices are 18350, 18490, and [65] The power section may include additional options such as screen readout, support for a wide range of internal batteries, and compatibility with different types of atomizers. [55] Third Third generation PV. generation devices commonly use rebuildable atomizers that can be utilize different wicking materials. [45][55] These rebuildable devices use handmade coils that can be installed in the atomizer to increase vapor production. [63] Hardware in this generation is sometimes modified to increase power or flavor. [66] The larger battery sections used also allow larger tanks to be attached that can hold more e-liquid. [62] A fourth generation digital e-cigarette became available in the U.S. in [7] Atomizer An atomizer comprises a small heating element that vaporizes e-liquid and a wicking material that draws liquid onto the coil. [67] Along with a battery, the atomizer is the central component of every personal vaporizer. A small length of resistance wire is coiled around the wicking material and connected to the integrated circuit, or in the case of mechanical devices, the atomizer is connected directly to the battery through a switch. When activated, the resistance wire coil heats up and vaporizes the liquid, which is then inhaled by the user. [68] The electrical resistance of the coil, the voltage output of the device, the airflow of the atomizer and the efficiency of the wick all affect the vapor coming from the atomizer. They also affect the vapor quantity or volume yielded. Atomizer resistances usually vary from 1.5Ω (ohms) to 3.0Ω, but they can go as low as 0.1Ω in the most extreme cases of DIY coil building. Coils of lower ohms have increased vapor production but could risk fire and dangerous battery failures if the user is not knowledgeable enough about electrical principles and how they relate to battery safety. [69] An e-cigarette atomizer with the coil (heating element) in view. Wicking materials vary from one atomizer to another but silica fibers are most common. "Rebuildable" or "do it yourself" atomizers can use silica, cotton, rayon, porous ceramic, hemp, bamboo yarn, oxidized stainless steel mesh and even wire rope cables as wicking materials. [70] 7 of 34 27/04/15 10:55 AM

8 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. [67] They can have up to 3 coils and each coil will increase vapor production. [67] The cartomizer 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 A 45mm length, extra-long cartomizer. flooded (gurgling) because of sedimentation of the wick. [67] Most cartomizers are refillable even if not advertised as such. [67][71] Cartomizers can be used on their own or in conjunction with a tank that allows more e-liquid capacity. [67] In this case the portmanteau word of "cartotank" 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. [67] Clearomizers Clearomizers or "clearos", not unlike cartotanks, use a clear tank in which an atomizer is inserted. [72] Unlike cartotanks, however, they do not use a poly-foam material. There are many different wicking systems employed inside of clearomizers to maintain the balance between good moistening of the wick versus too much liquid which can flood 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). [67][73] The coil and wicks are typically inside a prefabricated assembly or "head" that is replaceable by the user and can contain either single or dual coils. Present day clearomizers commonly have adjustable air flow control. They also hold up to 5ml of e-liquid. Tanks can be plastic, glass, stainless steel, or a combination of those materials. Some flavors of e-juice have been known to damage plastic clearomizer tanks. [74] 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 with off-the-shelf atomizer "heads". [45] They are ego style e-cigarette with a top-coil clearomizer. Silica fibers are hanging down freely inside of the tank, drawing e-liquid by capillary action to the coil that is located directly under the mouthpiece. generally considered advanced devices. They also allow the user to build atomizers at any desired electrical resistance. [45] These atomizers are divided into three main categories; rebuildable tank atomizers (RTAs), rebuildable dripping atomizers (RDAs), [75] and rebuildable dripping tank atomizers (RDTAs). 8 of 34 27/04/15 10:55 AM

9 Rebuildable tank atomizers (RTAs) are similar to clearomizers in that they use a tank to hold liquid that is absorbed by the wick. They usually hold significantly more e-liquid than other atomizers or clearomizers. The tank can be either plastic, glass, metal, or a combination. An early form of tank atomizers was the Genesis style atomizers. They commonly use stainless steel mesh or rope for wicking material. The steel wick must be oxidized to prevent arcing of the coil. One drawback of the Genesis style atomizers was they would often leak if they were not not always held upright. Rebuildable dripping atomizers (RDAs) are atomizers where the e-juice is dripped directly onto the coil and wick. They typically consist only of an atomizer "building deck", commonly with three posts with holes drilled in them, which can accept one or more coils. [66] A "top cap" is used to cover the coils and feature a hole at the top where a mouth piece can be attached. The wick is generally larger than those found in tank atomizers. The user needs to manually keep the atomizer wet by dripping liquid on the bare wick and coil assembly, hence their name. Modern dripping atomizers can have raised edges forming a cup or "juice well". This allows more wick to be used and helps stop leaking. Some atomizers have heat sink fins to dissipate the heat from the coil before it reaches the mouth piece or "drip tip". Rebuildable dripping tank atomizers (RDTAs) are a combination of both RTAs and RDAs. They usually consist of a RDA build deck with a tank over the deck held up by a spring. The user pushes down on the mouth piece and liquid is then dripped onto the coils and wick. This is unlike a RTA that continuously feeds liquid to the wicks via gravity or capillary action. Power Variable power and voltage devices The devices contain a rechargeable battery, which tends to be the largest component of an electronic cigarette. [76] Many devices feature variable power and/or variable voltage and contain a built-in electronic chip allowing the user to adjust the power that is applied to the heating element. [55] The devices are often rectangular in shape but can also be cylindrical. [62] They usually incorporate a screen to display information like voltage, power, and resistance of the coil. [77] Variable wattage devices allow the user to adjust the voltage applied to the coil. Variable wattage devices monitor the resistance of the coil and automatically adjust the voltage to apply the user-specified level of power to the coil. [78] Variable devices are either variable wattage, variable voltage or both. [59] To adjust the settings the user presses buttons or rotates a dial to make adjustments in power either up or down. [51] The amount of power applied to the coil has a direct relationship to the heat produced, thus changing the vapor output. [55][51] Greater heat generated by the coil increases vapor PV with variable and regulated power offering battery protection. production. [51] Some of these devices include additional settings through their menu system such as: atomizer resistance meter, remaining battery voltage, puff counter, and power-off or lock. [79] Mechanical personal vaporizers 9 of 34 27/04/15 10:55 AM

10 Mechanical PVs or mechanical "mods", often called "mechs", are devices without integrated circuits, electronic battery protection, or voltage regulation. Because there is neither protection nor regulation, they will work regardless of the the battery's orientation. They are activated by spring loaded or opposing magnetic mechanical switches, hence their name. They rely on the natural voltage output of the battery and the metal that the mod is made of often is used as part of the circuit itself. [80] The term "mod" was originally used instead of "modification". [45] Users would modify existing hardware to get better performance, and as an alternative to the e-cigarettes that looked like traditional cigarettes. [51] Users would also modify other unrelated items like flashlights as battery compartments to power atomizers. [62][51] Today the word mod is used to describe most personal vaporizers either bought in a store or created by the user. Mechanical PV with a rebuildable atomizer. Because mechanical PVs have no power regulation and are unprotected, they require special attention from the user beyond what is required with other regulated and protected PVs do not require. Ensuring that the battery does not over-discharge and that the resistance of the atomizer requires an amperage within the safety limits of the battery is the responsibility of the user. [80] E-liquid E-liquid, e-juice or simply "juice", is the liquid that vaporizes when heated. There is a vast array of e-liquids available. [81] The main ingredients are propylene glycol, glycerin, water, nicotine, and flavorings; and optionally, tobacco-derived nicotine. [11] The liquid typically contains 95% propylene glycol and glycerin. [82] E-liquid containing glycerin and water made without propylene glycol is also available. [6] The nicotine in e-liquid may be prepared using a United States Pharmacopeia-grade nicotine, a tobacco plant extract, tobacco dust or a synthetic nicotine. [83] Most e-cigarette liquids contain nicotine, but the level of nicotine varies depending on user-preference and manufacturers. [84] E-liquid without nicotine is also available. [84] Although some e-juice is nicotine-free, surveys demonstrate that 97% of e-cigarette users use products that contain nicotine. [7] The solution is often sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own e-juices. Components are also available to modify or boost their flavor or nicotine strength. [85] Pre-made e-liquids are made with various tobacco, fruit, and other flavors, [5] as well as variable nicotine concentrations (including nicotine-free versions). The standard notation "mg/ml" is often used on labels to denote nicotine concentration, and is sometimes shortened to "mg". [86] In surveys of regular e-cigarette users, the most popular e-liquids have a nicotine content of 18 mg/ml, and the preferred flavors were largely tobacco, mint and fruit. [14] A cartridge may contain 0 to 20 mg of nicotine. [87] A refill bottle can contain up to 1 g of nicotine. [87] The flavorings may be natural or artificial. [88] Some liquids without flavoring is also available. [89] A person does not normally use an entire cartridge of one e-cigarette in a single session. [27] Health effects 10 of 34 27/04/15 10:55 AM

11 Position of medical organizations As of 2014 electronic cigarettes had not been approved as a smoking cessation device by any government. [90] In July 2014, a report produced by the World Health Organization (WHO) for the WHO Framework Convention on Tobacco Control, found there was not enough evidence to determine if electronic cigarettes can help people quit smoking. It suggested that smokers should be encouraged to use approved methods for help with quitting. [90] But the same report also mentioned expert opinions in scientific papers that suggested e-cigarettes may have a role helping people quit who have failed using other methods. [90] A previous WHO statement from July 2013 stated that e-cigarettes have not been shown to be effective helping people quit smoking. [13] It also recommended that "consumers should be strongly advised not to use" e-cigarettes unless a reputable national regulatory body has found them safe and effective. [13] The World Lung Foundation applauded the WHO report's recommendation for tighter regulation of e-cigarettes due to concerns about the safety of e-cigarettes and the possible increased nicotine or tobacco addiction among youth. [91] The UK National Health Service concluded that "While e-cigarettes may be safer than conventional cigarettes, we don't yet know the long-term effects of vaping on the body. There are clinical trials in progress to test the quality, safety and effectiveness of e-cigarettes, but until these are complete, the government can't give any advice on them or recommend their use." [92] In 2014, the US Food and Drug Administration (FDA) stated, "E-cigarettes have not been fully studied, so consumers currently don't know: the potential risks of e-cigarettes when used as intended, how much nicotine or other potentially harmful chemicals are being inhaled during use, or whether there are any benefits associated with using these products. Additionally, it is not known whether e-cigarettes may lead young people to try other tobacco products, including conventional cigarettes, which are known to cause disease and lead to premature death." [93] Smoking cessation As of 2014, research on the safety and efficacy of e-cigarette use for smoking cessation is limited. [30][94] They are unproven as quit-smoking aids. [28] Their benefit for quitting smoking is uncertain. [8] The evidence suggests that e-cigarettes can supply nicotine at concentrations that are, at least partially, enough to substitute for traditional cigarettes. [95] While there are some reports of improved smoking cessation, especially with intensive e-cigarette users, there are also several studies showing a decline in cessation in dual users. [15] A 2014 Cochrane review found limited evidence of a benefit as a smoking cessation aid from a small number of studies. [9] A 2015 review concluded that while they may have a benefit for decreasing cigarette use in smokers, they have a limited benefit in quitting smoking. [96] A 2014 review found e-cigarettes may have some potential for reducing smoking. [16] A 2015 review found variable quality evidence that e-cigarette users had higher cessation rates than users of nicotine replacement products. [97] A 2014 review found limited quality evidence that e-cigarettes do not seem to improve cessation rates compared to regulated FDA nicotine replacement products. [94] Two 2014 reviews found no evidence that e-cigarettes are more effective than existing nicotine replacement products for smoking cessation. [9][10] They may be as effective, but not more, compared to nicotine patches for short-term smoking cessation. [17] However, a randomized trial 11 of 34 27/04/15 10:55 AM

12 found 29% of e-cigarette users maintained e-cigarette use at 6 months while 8% for patch users, indicating the use of e-cigarettes could continue after other quit methods. [17] Studies have not shown that e-cigarettes are superior to regulated medications for smoking cessation. [8] A 2014 review found four experimental studies and six cohort studies that indicated that electronic cigarettes reduced the desire to smoke and withdrawal symptoms. [98] This review also noted that two cohort studies found that electronic cigarettes led to a reduction in the number of cigarettes smoked per day. [98] Nicotinecontaining e-cigarettes were associated with greater effectiveness for quitting smoking than e-cigarettes without nicotine. [97] A 2014 review concluded that the adverse public health effects resulting from the widespread use of e-cigarettes could be significant, in part due to the possibility that they could undermine smoking cessation. [99] This review therefore called for their use to be limited to smokers who are unwilling or unable to quit. [99] A 2014 review found that the research suggested that personal e-cigarette use may reduce overall health risk in comparison to traditional cigarettes. [76] However, e-cigarettes could have a broad adverse effect for a population by expanding initiation and lowering cessation of smoking. [76] A 2014 review found that the evidence suggests that "e-cigarettes are not associated with successful quitting in general population-based samples of smokers." [5] Harm reduction Tobacco harm reduction has been a controversial area of tobacco control. [100] The health community has not been willing to endorse e-cigarettes as a tobacco harm reduction strategy, in part in response to tobacco industry deception. [100] A 2014 review concluded promotion of e-cigarettes as a harm reduction aid is premature. [10] Another review found e-cigarettes would likely be less harmful to users and bystanders. [14] The authors warned against the potential harm of excessive regulation and advised that health professionals may consider advising smokers who are reluctant to quit by other methods to switch to e-cigarettes as a safer alternative to smoking. [14] A 2014 review argued that regulations for electronic cigarettes should be similar to those for dietary supplements or cosmetic products to not limit their potential for harm reduction. [20] E-cigarettes may have potential in harm reduction compared to using other tobacco products. [3] When used to quit smoking, they could reduce harm even more if the tobacco user quits but e-cigarettes are not harmless because nicotine has long-term adverse effects, may contain impurities, and nicotine is addictive, which may have serious side effects, particularly if users use unconventional ways to increase the doses of nicotine exposure. [3] 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. [12] A 2012 review found e-cigarettes could considerably reduce traditional cigarettes use and they likely could be used as a lower risk replacement for traditional cigarettes, but there is not enough data on the safety and efficacy to draw definite conclusions. [1] E-cigarette use for risk reduction in high-risk groups such as people with mental disorders is unavailable. [101] Smoke from traditional tobacco products has 40 known carcinogens among the 10,000 chemicals it contains, none of which has been found in more than trace quantities in the cartridges or aerosol of e-cigarettes. [100] A 2011 review stated that while e-cigarettes can not be considered "safe" because there is no safe level for carcinogens, they are doubtless safer compared to tobacco cigarettes. [100] Any residual risk of e-cigarette use should be weighed relative to the risk of continuing or returning to smoking, taking account of the low success rate of currently-approved smoking cessation medications. [102] Adults most frequently use electronic cigarettes as a replacement for tobacco, but 12 of 34 27/04/15 10:55 AM

13 not always to quit. [17] Although some people have a desire to quit smoking by using e-cigarettes, another common explanation for the use of these products is to cut back on traditional cigarettes. [5] In 2014 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 their full potential requires regulation and monitoring to minimize possible risks. [103] They found that the evidence suggests that a considerable number of smokers want to reduce harm from smoking by using these products. [103] The British Medical Association 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. [104] 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 smokeless tobacco for long term use instead of smoking. [105] In an interview, the director of the Office on Smoking and Health for the U.S. federal agency Centers for Disease Control and Prevention (CDC) believes that there is enough evidence to say that using e-cigarettes is likely less harmful than smoking a pack of conventional cigarettes. However, due to the lack of regulation of the contents of the numerous different brands of electronic cigarettes and the presence of nicotine, which is not a benign substance, the CDC has issued warnings. [106] A 2014 WHO report concluded that some smokers will switch completely to e-cigarettes from traditional tobacco but a "sizeable" number will use both tobacco cigarettes and electronic cigarettes. This report found that such "dual use" of e-cigarettes and tobacco "will have much smaller beneficial effects on overall survival compared with quitting smoking completely." [90] Safety The risks of electronic cigarette use are uncertain. [4][8] There is little data about their health effects, [107] and considerable variability between vaporizers and the contents of the aerosol delivered to the user. [5][12][108] The limited evidence suggests that e-cigarettes are probably safer than traditional cigarettes. [12] One review found, from limited data, that they are similar in safety to smokeless tobacco. [11] Another concluded that regulated FDA products such as a nicotine inhaler are probably a safer way to supply nicotine than e-cigarettes. [10] Various methodological issues, conflicts of interest, and inconsistent research has been identified in the research regarding e-cigarettes. [99] However, e-cigarettes cannot be regarded as simply harmless. [99] As well as toxicity there are also risks from misuse or accidents (e.g., accidental fires caused by vaporizer malfunction, other vaporizer design issues, or accidental contact with liquid nicotine). [5][102][109] A July 2014 WHO report cautioned about potential risks of using e-cigarettes. The report concluded that "the existing evidence shows that ENDS aerosol is not merely "water vapour" as is often claimed in the marketing for these products. ENDS use poses serious threats to adolescents and fetuses." [90] A 2014 systematic review concluded that the risks of e-cigarettes have been exaggerated by health authorities and stated that there may be some remaining risk, though the risk of e-cigarette use is likely small compared to smoking tobacco. [102] A 2014 Cochrane review found no serious adverse effects reported in trials. [9] Less serious adverse effects from e-cigarette use can include throat and mouth inflammation, vomiting, nausea, and cough. [5] The long-term effects of e-cigarette use are unknown. [15][16] The risk is probably low from the inhalation of propylene glycol and glycerin. [14] 13 of 34 27/04/15 10:55 AM

14 E-cigarette users are exposed to potentially harmful nicotine. [2] A 2014 review recommended that e-cigarettes should be regulated for consumer safety. [20] Addiction A number of organizations have concerns that e-cigarettes might increase addiction to and use of nicotine and tobacco products in the young. [110][111][112] These include 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. [106][113][114][115] The World Health Organization raised concern of addiction for nonsmokers from their use in July [13] The National Institute on Drug Abuse stated that there is a possibility that they could promote continuation of addiction to nicotine in those who are attempting to quit. [111] It is not clear whether using e-cigarettes will decrease or increase overall nicotine addiction. [107] The information concerning the drug action of the nicotine in e-cigarettes is limited. [95] The evidence suggests that the nicotine in e-cigarettes is adequate to sustain nicotine dependence. [95] The limited data suggests that the likelihood of abuse from e-cigarettes could be smaller than traditional cigarettes. [54] A 2014 systematic review found that the concerns that e-cigarettes could cause non-smokers to begin smoking are unsubstantiated. [102] A 2014 review found no evidence that they are used regularly by those who have never smoked, [14] The nicotine molecule. while another 2014 review has found that in some populations nearly up to a third of youth who have ever used electronic cigarettes have never smoked traditional cigarettes. [5] No long-term studies have been done on the effectiveness of e-cigarettes in treating tobacco addiction. [10] The degree to which teens are using e-cigarettes in ways it is not intended to be used, such as increasing the nicotine delivery, is unknown. [109] The extent to which e-cigarette use will lead to abuse in youth is unknown. [109] The impact of e-cigarette use by children in respect to substance dependence is unknown. [109] Some evidence suggests that dual use of e-cigarettes and traditional cigarettes may be associated with greater nicotine dependence. [15] 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. [116][117] Hon Lik, a Chinese pharmacist and inventor, who worked as a research pharmacist for a company producing ginseng products, is credited with the invention of the modern electronic cigarette. [19][118] Hon quit smoking after his father, also a heavy smoker, died of lung cancer. In 2003, [119] he came up with the idea of using a piezoelectric ultrasound-emitting element to vaporize a pressurized jet of liquid containing nicotine diluted in a propylene glycol solution. [120] This design produces a smoke-like vapor that can be inhaled and provides a vehicle for nicotine delivery into the 14 of 34 27/04/15 10:55 AM

15 bloodstream via the lungs. He also proposed using propylene glycol to dilute nicotine and utilizing a disposable plastic cartridge to serve as a liquid reservoir and mouthpiece. Hon patented the modern e-cigarette design in [1] Electronic cigarettes using a different designs were first introduced to the Chinese domestic market in May 2004 as an aid for smoking cessation and replacement. Many versions made their way to the U.S., sold mostly over the Internet by small marketing firms. [19] The company that Hon Lik worked for, Golden Dragon Holdings, changed its name to Ruyan (, literally "Resembling smoking"), and started exporting its products in [19] before receiving its first international patent in [121] 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. [122] This is a mechanism which integrates the heating coil into the liquid chamber. The new device was launched in the UK in 2007 under their Gamucci brand and the design 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. [123] Since 2007, e-cigarette use in the US has risen. [41] International tobacco companies, recognizing the development of a potential new market sector that could render traditional tobacco products obsolete, [124] are increasingly involved in the production and marketing of their own brands of e-cigarettes and in acquiring existing e-cigarette companies. [125] Blu, a prominent US e-cigarette manufacturer, was acquired by Lorillard Inc. in [126] 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. [127][128] On 1 October 2013 Lorillard Inc. acquired another e-cigarette company, this time the UK based company SKYCIG. [129] 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 with $20 million in incentive payments. [130] Altria also markets its own e-cigarette, the MarkTen, while Reynolds American has entered the sector with its Vuse product. [125] Society and culture Consumers of electronic cigarettes, sometimes referred to as "vapers", have shown evident and passionate support for the product that other nicotine replacement therapy did not receive. [51][103] This suggests that electronic cigarettes have the potential mass appeal that could challenge the preeminence of combustible tobacco as the object of choice for nicotine users. [103] As the electronic cigarette industry grows, a subculture has emerged which calls itself "the vaping community". [51][131] The online forum E-Cig-Reviews.com was one of the first major communities. [62] Another online forum known as UKVaper.org was the origin of the hobby of modding. [62] There are also groups on Facebook and Reddit. [66] Members of this emerging subculture often view electronic cigarettes as a safer alternative to smoking [14] and some even view it as a hobby. [132] These groups tend to use highly customized devices that do not resemble the earlier "cig-a-likes", the electronic cigarettes that resemble real cigarettes. [133] Online forums based around modding have grown in the vaping community. [134] A 2014 Postgraduate Medical Journal 15 of 34 27/04/15 10:55 AM

16 editorial stated that e-cigarette companies have a substantial online presence, as well as many individual vapers who spend time blogging and tweeting about e-cigarette related products. [135] The editorial stated that a few vapers "engage in grossly offensive online attacks on anyone who has the temerity to suggest that ENDS are anything other than an innovation that can save thousands of lives with no risks". [135] A 2014 review stated that tobacco and e-cigarette companies interact with consumers for their policy agenda. The companies use websites, social media, and marketing to get consumers involved in opposing bills that include e-cigarettes in smoke-free laws. This is similar to tobacco industry activity going back to the 1980s. It was concluded that these approaches were used in Europe to minimize the EU Tobacco Product Directive in October [5] Large gatherings of vapers, called vape meets, are happening around the United States. They focus on e-cig devices, accessories, and the lifestyle that accompanies them. [51] Vapefest, which started in 2010, is an annual show hosted by different cities. [66] 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. [51] These products are mostly available online or in dedicated "vape" storefronts where mainstream e-cigarettes brands from the tobacco industry and larger e-cig manufacturers are not as popular. [136] As of 2014, availability of e-cigarettes is increasing in retail stores in the U.S., especially in places with low taxed and smoking ban regulations. [137] A growing subclass of vapers called "cloud-chasers" assemble their atomizers in such a way that can produce extremely large amounts of vapor by using heating coils with a resistance of less than 1 ohm. [138] This practice is known as "cloud-chasing". By using a coil with very low resistance,the batteries used are stressed beyond the margins of what could be considered safe use. This could represent a risk of dangerous battery failures. [63] 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. [139] The Oxford Dictionaries' word of the year for 2014 is 'vape'. [140] Legal status Because of the novelty of the technology and the possible relationship to tobacco laws and medical drug policies, electronic cigarette legislation is currently pending in many countries. [21] As of 2015, around two thirds of major nations have regulated e-cigarettes in some way. [141] Current regulations vary widely, from regions with no regulations to others banning the devices entirely. [21] For example, some countries such as Brazil, Singapore, the Seychelles, and Uruguay have banned e-cigarettes. [5] In Canada, they are legal to sell, however nicotine-containing e-fluid is not approved by Health Canada - making it technically illegal, although widely unenforced and commonly available for sale. [142] As of 2015, e-cigarettes are legal for minors to buy in a few states in the U.S. [28] and since they do not contain tobacco, television advertising is not restricted. [143] As of 2014, a small number of states in the U.S. had imposed regulations that allow e-cigarettes to be taxed as tobacco products. [144] As of 2014, a small number of state and regional governments in the U.S. had applied indoor smoking bans to e-cigarettes. [144] In August 2014, attorneys general from over two dozen states recommended to the FDA to enact restrictions on e-cigarettes, including banning flavors. [145] E-cigarettes have been classified as "drug delivery devices" in several countries because they can contain nicotine, and their advertising has been restricted until safety and efficacy trials are conclusive. [87] A 2014 review stated that the regulation of these products should be examined in 16 of 34 27/04/15 10:55 AM