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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 has the feel of tobacco smoking. They produce an aerosol rather than cigarette smoke. In general a heating element vaporizes a liquid solution known as e-liquid. E-liquids are usually a mixture of propylene glycol, glycerin, nicotine, and flavorings. Others have similar ingredients but without nicotine.

The benefits and risks of electronic cigarette use are uncertain. Evidence suggests e-cigarettes may be safer than smoking tobacco products. The data is inconclusive on using e-cigarettes as a smoking cessation aid. Their role in tobacco harm reduction as a substitute for tobacco products is unclear. They may possibly be as safe as other nicotine replacement products, but there is not enough data to draw conclusions. Electronic cigarettes may carry a risk of addiction in those who do not already smoke, but there is no evidence of ongoing use among those who have never smoked. They may promote delaying or deterring to quit smoking. Emissions from e-cigarette may contain tiny particles of flavors, aroma transporters, glycerol, propylene glycol, nicotine, tiny amounts of carcinogens, heavy metals, and other chemicals. The evidence indicates the levels of contaminants do not warrant health concerns according to workplace safety standards. E-cigarette mist has fewer toxicants than cigarette smoke. They are likely to be less harmful to users and bystanders. Less serious complaints from e-cigarette users include throat and mouth inflammation, vomiting, nausea, and cough.

The frequency of use has increased with up to 10% of American high school students having ever used them as of 2012 and around 3.4% of American adults as of 2011. In the UK the number of e-cigarette users has increased from 700,000 in 2012 to 2.1 million in 2013. About 60% are smokers and most of the rest are ex-smokers. E-cigarette users most commonly continue to smoke traditional cigarettes. Current e-cigarettes arose from an invention made in China in 2003 and devices are mostly manufactured in China. E-cigarette brands have increased advertising with similar marketing to that used to sell cigarettes in the 1950s and 1960s.

Because of the possible relationship to tobacco laws and medical drug policies, electronic cigarette legislation is being debated in many countries. The European Parliament passed regulations in February 2014 requiring standardization of liquids and personal vaporizers, listing of ingredients, and child-proofing of liquid containers. The United States Food and Drug Administration published proposed regulations in April 2014 with some similar measures.

Health effects

Position of medical organizations

As of 2014 electronic cigarettes have not been approved, for helping people quit smoking, by any government.

International

In July 2014, a report published by the World Health Organization (WHO) 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. 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. A previous WHO statement from July 2013 stated that e-cigarettes have not been shown to be effective helping people quit smoking. 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. The World Lung Foundation "applauded" the 2014 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.

In October 2012, the World Medical Association released a statement which stated, "Due to the lack of rigorous chemical and animal studies, as well as clinical trials on commercially available e-cigarettes, neither their value as therapeutic aids for smoking cessation nor their safety as cigarette replacements is established. Lack of product testing does not permit the conclusion that e-cigarettes do not produce any harmful products even if they produce fewer dangerous substances than conventional cigarettes."

In January 2014, the International Union Against Tuberculosis and Lung Disease released a statement asserting that the benefits and safety of electronic cigarettes have not been scientifically proven. The statement highlighted concerns with regards to "re-normalization" of smoking behavior and exposure of third parties to possibly dangerous emissions from e-cigarettes, and strongly supported regulation of electronic cigarettes, preferably as medicines.

In August 2014, the Forum of International Respiratory Societies, which represents multiple pulmonary associated medical associations in the United States, Latin America, Africa, Europe, and Asia, released a statement in which they argued that electronic cigarettes have not been demonstrated to be safe and their benefits as a smoking cessation tool or in harm reduction has not been adequately studied. They recommended banning their use, or regulation as medicines or tobacco products if not banned, until adequate studies are performed.

United Kingdom

The UK National Health Service has concluded regarding electronic cigarettes, "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." A National Institute for Health and Care Excellence (NICE) guideline recommended licensed nicotine replacement therapy as part of a program for harm reduction, but did not recommend electronic cigarettes as they are unregulated, and there are questions regarding the safety, efficacy, and quality of these products. 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. In June 2014, the Royal College of Physicians released a statement saying, "On the basis of available evidence, the Royal College of Physicians believes that e-cigarettes could lead to significant falls in the prevalence of smoking in the UK, prevent many deaths and episodes of serious illness, and help to reduce the social inequalities in health that tobacco smoking currently exacerbates." In May 2014, Cancer Research UK released a statement reading, "Electronic cigarettes (e-cigarettes) are almost certainly much safer than tobacco cigarettes and may help smokers to cut down or quit smoking. We support the use of high quality e-cigarettes because we believe that they have significant potential to help smokers who aren't otherwise ready or able to quit smoking by providing them with much safer alternatives to smoked tobacco. It is important that regulation does not stifle the development of this market nor make accessing these products by smokers more difficult. However, the current safeguards are insufficient to ensure that these products are as safe as nicotine replacement therapy and to ensure that they are not marketed to non-smokers and children."

United States

In 2014, the US Food and Drug Administration has concluded, "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." Smokefree.gov, a website run by the Tobacco Control Research Branch of the National Cancer Institute to provide information to help quit smoking, stated that e-cigarettes have not been shown to be effective in helping people quit smoking and therefore did not recommend the use of e-cigarettes. In 2010, the American Medical Association called for electronic cigarettes to be subject to the same FDA regulations as tobacco and nicotine products. The Association extended this policy in 2014, and endorsed measures aimed at preventing marketing of electronic cigarettes to minors. In August 2014, the American Heart Association released a policy statement in which they noted that "current evidence evaluating the efficacy of these products as a cessation aid is sparse, confined to 2 randomized controlled trials and 1 large cross-sectional study, anecdotal reports, and Internet-based surveys." The statement stated "there is not yet enough evidence for clinicians to counsel their patients who are using combustible tobacco products to use e-cigarettes as a primary cessation aid." Another statement released that month by the American Lung Association argued that the FDA should begin its regulatory oversight of electronic cigarettes, because otherwise, "there is no way for the public health, medical community or consumers to know what chemicals are contained in e-cigarettes or what the short and long term health implications might be." The American Cancer Society has concluded, "Because the American Cancer Society doesn’t yet know whether e-cigarettes are safe and effective, we cannot recommend them to help people quit smoking. There are proven methods available to help people quit, including pure forms of inhalable nicotine as well as nasal sprays, gums, and patches." The US National Association of County and City Health Officials has stated, "Currently, little scientific evidence exists to show that e-cigarettes are effective cessation devices" and "Further research is needed on the health risks of e-cigarettes, but available evidence suggests harmful effects." They recommend to local health departments to advocate for regulation as a tobacco product to the extent allowable by law.

Canada

Health Canada has concluded that, "To date, no electronic cigarettes with nicotine and/or health claims have been authorized by Health Canada and their safety, quality, and efficacy remain unknown" and "Health Canada advises Canadians not to purchase or use electronic cigarettes as these products may pose health risks." The Canadian Cancer Society has concluded, electronic cigarettes "have not been scientifically proven to help people quit" smoking tobacco. The Canadian Heart and Stroke Foundation has stated, "While early studies show some potential benefits, the effectiveness of e-cigarettes with nicotine as a smoking cessation device is not fully conclusive," and expressed concerns about the lack of long term studies with regard to health effects to the user as well as second hand exposure. They also note public health officials' concerns about renormalizing smoking behavior undermining current tobacco control as well as being a gateway for nicotine addiction and tobacco abuse.

Australia and other countries

The Therapeutic Goods Administration (TGA) of Australia has stated, "the quality and safety of electronic cigarettes is not known" due to the lack of studies, unlike conventional nicotine replacement therapies, and lists possible risks involved with buying or using electronic cigarettes. They also state, "The Australian Government is concerned about the use of electronic cigarettes in Australia. The impact of wide scale use of these devices on tobacco use is not known, and the outcome in the community could be harmful." A 2014 practice guideline by NPS MedicineWise states, "While use of e-cigarettes may be safer than smoking tobacco, so far there is limited evidence to support their effectiveness as aids in smoking cessation. There are also safety issues to consider and the long-term effects are unknown." This guideline recommends physicians steer patients away from e-cigarettes to "more established" methods of smoking cessation until safety and efficacy are established. The Cancer Council Australia and Heart Foundation released a joint position statement that stated, "The limited evidence available points to a risk that widespread electronic cigarette use could undo the decades of public policy work in Australia that has reduced the appeal of cigarette use in children" and the "short and long term health effects of electronic cigarette use remain unknown." They also consider claims that electronic cigarettes can help quit smoking as "unsubstantiated" and urge "extreme caution on electronic cigarettes" while urging significant regulations of both nicotinic and non-nicotinic electronic cigarettes.

The Ministry of Health of New Zealand has stated, "There is not enough evidence to be able to recommend e-cigarettes as an aid to quit smoking" and recommends more established treatments for smoking cessation. They also point interested readers to the 2014 WHO statement for further information. The Cancer Society of New Zealand released a position statement which states, "Currently, there is limited evidence of the safety of e-cigarettes or their suitability as a smoking cessation aid" and "Before they are widely promoted, evidence is needed to ensure that e-cigarettes are a safe harm reduction alternative to tobacco smoking, that they are a safe and effective cessation aid, that they don’t undermine motivation to quit, and that they don’t act as a gateway to nicotine addiction for young people."

The Spanish Society of Pneumonology and Thoracic Surgery released a position statement which states that the substances found in aerosol from electronic cigarettes have not been demonstrated to be safe, and a number of chemicals which are carcinogens and can damage the lung have been found, though usually in concentrations smaller than conventional cigarettes. Studies done to date have been small in size and have had significant methodological flaws, making drawing any definitive conclusions about their ability to aid in smoking cessation impossible. Due to concerns about "indiscriminate use" which can be a public health risk and may encourage young people to start smoking, they advocate regulation of electronic cigarettes as a medicine and encourage smoking cessation through other more established means.

The Food and Drug Administration of the Philippines released a statement saying that there has been little evidence published about the health effects of electronic cigarettes, including whether they help quit smoking. The statement concluded that the available evidence does not support those who advocate for their use either as tools to help quit smoking or for harm reduction. The Philippine Medical Association has also taken a strong position against the use of electronic cigarettes, citing safety concerns.

Smoking cessation

As of 2014, research on the safety and efficacy of e-cigarette use is limited, therefore, their possibility for smoking cessation has not been convincingly demonstrated, and the benefit with respect to helping people quit smoking is uncertain.

A 2014 review found no evidence confirming e-cigarettes as a more effective aid than existing FDA-compliant nicotine replacement treatments for smoking cessation. The same review found that to encourage e-cigarette use as a cessation aid in cigarette users is premature. A 2013 randomized controlled trial found higher smoking cessation rates associated with e-cigarettes with nicotine than e-cigarettes without nicotine or traditional NRT patches, however the study was too small to make these results statistically significant. 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.

Harm reduction

Tobacco harm reduction has been a controversial area of tobacco control. The health community have been cautious to support the tobacco industry to bring safer products to market that will lessen the risks related with tobacco use. A 2011 review found in the fight to decrease tobacco related death and disease, e-cigarettes show great promise. A 2014 review found some evidence that e-cigarettes may lower tobacco cigarette use, however no long-term studies have been done on e-cigarettes safety. Thus their role, as a substitute for tobacco products, in tobacco harm reduction is unclear. A 2014 review found e-cigarettes may be less harmful than tobacco cigarettes to users and bystanders. The same review concluded that health professionals may consider advising smokers who are reluctant to quit by way of other methods to switch to e-cigarettes as a safer alternative to smoking. A 2014 review argued that regulations for electronic cigarettes should be similar to those for dietary supplements or cosmetic products to not limit the potential for harm reduction with electronic cigarettes replacing tobacco. 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.

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 mist of e-cigarettes. 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. 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. Adults most frequently use electronic cigarettes as a replacement for tobacco, but not always to quit. 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.

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. 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. 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. 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. 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."

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 mist 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. A July 2014 WHO report cautioned about potential risks of using electronic cigarettes. A 2014 systematic review concluded that the risks of e-cigarettes have been exaggerated by health authorities and stated that it is apparent that there may be some remaining risk accompanied with e-cigarette use, though the risk of e-cigarette use is likely small compared to smoking tobacco. No long-term studies have shown that e-cigarettes are a "healthier alternative."

Toxicology

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 tobacco specific impurities suspected of being harmful to humans were anabasine, myosmine, and β-nicotyrine, they were detected in a majority of the samples. The amounts of TSNAs present were on par with a nicotine inhaler. The FDA's analysis also detected diethylene glycol, which is poisonous, in a single cartridge manufactured by Smoking Everywhere and nicotine in one cartridge claimed to be nicotine-free. This prompted the FDA to warn that e-cigarettes may present a health risk. While diethylene glycol was found in a cartridge tested in 2009 by the FDA, in 2011 researchers reviewed the data and noted that 15 other studies had failed to find any evidence of this chemical in e-cigarettes. 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. Further concerns were raised over inconsistent amounts of nicotine delivered when drawing on the device. A 2014 review found that the "Levels of carcinogens and toxins in e-cigarettes typically exceeded those measured in an FDA-approved nicotine inhaler, suggesting that FDA-approved devices may be a safer method of nicotine delivery."

The composition of inhaled levels of nicotine is not clear. There were inconsistency labeling of the actual nicotine content on e-liquid cartridges from some brands. Some nicotine have been found in ‘no nicotine' liquids. Due to nicotine content inconstancy, it is recommended that e-cigarette companies develop quality standards in respect to nicotine content. There are safety issues with the nicotine exposure from e-cigarettes, which has the possibility of causing addiction and other adverse effects. The risk is probably low from the inhalation of propylene glycol and glycerol. The essential propylene glycol and/or glycerol mixture may consist of natural or artificial substances to provide it flavor. Some of these substances are regarded as toxic and a number of them resemble known carcinogens. Although the majority of aromatic substances that mimic tobacco and others using generally inaccurate terms such as ‘vegetable flavoring' are approved for human use, there are no studies in respect to the short- and long-term effects of the inhalation of these substances. The toxicity of e-cigarettes and e-liquid can vary greatly, as there is potential differences in construction and materials in the delivery device, kind and origin of ingredients in the e-liquid, and the use or non-use of good manufacturing practices and quality control approaches. 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. The levels of chemical constituents in the mist were found to be 1 to 2 orders of magnitude smaller than in cigarette smoke but greater compared to a nicotine inhaler. The Centers for Disease Control and Prevention (CDC) stated the possible negative impact between nicotine and brain development in youth is a concern. A serious concern is the outcome of nicotine on the growing adolescent brain. There is no long-term research concerning the cancer risk related to the small level of exposure to the identified carcinogens. The short-term toxicity of e-cigarettes use appears to be low. The long-term health impacts of e-cigarettes use are unknown. There is limited peer-reviewed data in relation to the toxicity of e-cigarettes to allow a complete toxicological evaluation.

A 2013 review found after using a single e-cigarette there was an instant increase in airways resistance and concluded that they can do harm to the respiratory system. The risks, especially to the lungs, are not fully understood and are of concern to public health authorities. The particles are of the ultrafine size similar to that of traditional cigarettes, and can go deep in the lungs and then into the systemic circulation. Reports in the literature have shown respiratory and cardiovascular effects by these smaller size particles, suggesting a possible health concern. A 2014 review found e-cigarettes emissions contain the heavy metals nickel, tin, and chromium. These nanoparticles can deposit in the lung's alveolar sacs, potentially leading to local respiratory toxicity and entering the bloodstream. A 2014 review found it can be concluded that there is no evidence of contamination of the aerosol with metals that justifies a health concern. Another 2014 review found that the levels of metals were 10-50 times less than the point where they do harm. A 2014 review found that e-cigarettes used in the short-term on specified cardiovascular and respiratory functional results have demonstrated that even though some minor harmful effects of vaping are documented, these are appreciably milder in comparison to traditional cigarettes. The limited evidence suggests that e-cigarettes produce less short-term effects on lung function than traditional cigarettes. Like cancer risk, there is no literature outlining the long-term lung function or cardiovascular consequences.

Ultrafine particles

E-cigarettes produce particles, in the form of an aerosol. The aerosol produced from an e-cigarette is frequently but inaccurately called vapor. Technically, a vapor is a substance in the gas phase whereas an aerosol (mist) is a suspension of tiny particles of liquid, solid or both within a gas. The word "vaping" is not technically accurate when applied to e-cigarettes. The aerosol is made-up of liquid sub-micron particles of condensed vapor; thus, the users of these devices are rather "aerosolizing." The e-cigarette mist resembles cigarette smoke. A 2014 review found "Following a puff, the aerosol is delivered into the user's mouth and lungs by inhalation, after which the remaining aerosol is exhaled into the environment." E-cigarettes provide nicotine by creating liquid particles, a mist. E-cigarette mist mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and chemicals.

Fine particles can be chemically intricate and not uniform, and what a particle is made of, the exact harmful elements, and the importance of the size of the particle is mostly unknown. Because these things are uncertain, it is not clear whether the particles in e-cigarette mist have health effects similar to those produced by traditional cigarettes. The nature and chemical composition of particles in e-cigarette mist is entirely distinct from those in cigarette smoke. Though, the particle size composition and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range (modes, ≈100–200 nm).

Adverse effects

E-cigarettes use lithium batteries most of the time, improper use may result in accidents. Rare major injuries have occurred from battery malfunctions such as explosions and fires. The explosions resulted either by extended charging and use of unsuitable chargers or by design flaws have occurred. It is recommended manufacturing quality standards be employed in order to prevent such accidents. Complaints of less serious adverse effects of throat and mouth inflammation, vomiting, nausea, and cough have resulted from e-cigarette use. In youth, e-cigarette use risks involve accidental nicotine exposure and are possible choking dangers in youth. In pediatric patients, accidental exposures include ingesting of e-liquids and inhaling of e-cigarette mists. The US Food and Drug Administration Center for Tobacco Products reported between 2008 and the beginning of 2012, 47 cases of adverse effects associated with e-cigarettes, and eight were considered serious. A causal relationship between e-cigarettes and the reported adverse effects was not established with the exception of two severe outcomes in the United States: a death when an infant choked on the cartridges and burns when one blew up.

In the United States the number of calls to poison control centers related to electronic cigarettes have increased between 2010 and 2014 such that they now represent 42% of reported cases due to either cigarettes and e-cigarettes up from 0.3%. These calls were in connection to both adults and children. E-cigarettes were associated with fewer adverse effects than nicotine patches. Calls to U.S. poison control centers related to e-cigarette exposures were inhalations, eye exposures, skin exposures, and ingestion, which included adults and young children. The California Poison Control System reported from 2010 to 2012, 35 cases of e-cigarette contact. 14 were from children and 25 were from accidental contact. The majority of adverse effects reported were nausea, vomiting, dizziness and oral irritation.

Mist

Since e-cigarettes do not burn (or contain) tobacco, no side-stream smoke or any cigarette smoke is produced. Only what is exhaled by electronic cigarettes users enters the surrounding air. Exhaled mist consists of nicotine and some other particles, primarily consisting of flavors, aroma transporters, glycerol and propylene glycol. Bystanders are exposed to these particles from exhaled e-cigarette mist. A 2014 review of limited data concluded this mist can cause indoor air pollution and is not just "harmless water vapor". The dense mist consists of liquid sub-micron droplets. The liquid particles condenses into a viewable fog. The mist is in the air for a short time, with a half-life of about 10 seconds; traditional cigarette smoke is in the air 100 times longer. This is because of fast revaporization at room temperature. Some of the few studies examining the effects on health shown that being exposed to e-cigarette mist may produce biological effects. Since e-cigarettes have not been widely used long enough for evaluation, the long-term health effects from the second-hand mist are not known.

As of 2013, the only clinical study currently published evaluating the respiratory effects of passive vaping found no adverse effects were detected. A 2014 review found it is safe to infer that their effects on bystanders are minimal in comparison to traditional cigarettes. A 2014 WHO report stated passive exposure was as a concern, indicating that current evidence is insufficient to determine whether the levels of exhaled mist are safe to involuntarily exposed bystanders. The report concluded that the aerosol emissions are likely to increase the risk of disease to nearby bystanders, especially from those e-cigarettes which produce toxicant levels close to those emitted by certain cigarettes. E-cigarette mist has notably fewer toxicants than cigarette smoke (other than particulates) and is likely to pose less harm to users or bystanders.

Nonsmokers exposed to e-cigarette aerosol produced by a machine and pumped into a room were found to have detectable levels of the nicotine metabolite cotinine in their blood. The same study stated that 80% of nicotine is normally absorbed by the user, so these results may be higher than in actual second hand exposure. A 2014 review stated there are concerns about pregnant women exposure to e-cigarette mist through direct use or via exhaled mist. As of 2014, there is no conclusions on the possible hazards of pregnant women using e-cigarettes, and there is a developing research on the negative effects of nicotine on prenatal brain development. A 2014 review concluded no amount of nicotine is safe for pregnant women. As of 2014, the long-term issues of e-cigarettes on both mother and unborn baby are unknown. There are concerns about the health impacts of pediatric exposure to second-hand and third-hand e-cigarette mists.

A white paper published in 2014 by the American Industrial Hygiene Association concluded e-cigarettes emit airborne contaminants that may be inhaled by the user and those nearby. Due to this possible risk, they urged restriction of their use indoors, similar to smoking bans, until research has shown the aerosol does not significantly harm others in the area. A 2014 review indicated that the levels of inhaled contaminants from the e-cigarette mist are not of significant health concern for human exposures by the standards used in workplaces to ensure safety.

Addiction

It is not clear whether using e-cigarettes will decrease or increase overall nicotine addiction. 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. A number of organizations have concerns that e-cigarettes might increase addiction to and use of nicotine and tobacco products in the young. 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. A 2014 systematic review found these concerns that e-cigarettes could cause non-smokers to begin smoking are unsubstantiated. A 2014 review found no evidence that they are used regularly by those who have never smoked, while a 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. No long-term studies have been done on the effectiveness of e-cigarettes in treating tobacco addiction. 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. The extent to which e-cigarette use will lead to abuse in youth is unknown. The impact of e-cigarette use by children in respect to substance dependence is unknown.

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, PVs (personal vaporizer) or APVs (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 creating a mist from the liquid, 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 mist coming from the atomizer. They also greatly affect the mist quantity or volume 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. Coils of lower ohms have increased mist production 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, rayon, 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 "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.

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). The coil and wicks are typically inside a prefabricated assembly or "head" that is replaceable by the user and can contain either single or duel coils.

Present day clearomizers commonly have adjustable air flow control. They also hold up to 5ml of e-liquid. Tanks can be either plastic or glass. Some flavours of e-juice have been known to crack plastic clearomizer tanks.

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 used in clearomizers.

These atomizers are divided into three main categories; rebuildable tank atomizers (RTAs), rebuildable dripping atomizers (RDAs), and rebuildable dripping tank atomizers (RDTAs).

Rebuildable tank atomizers (RTAs) are similar to clearomizers in that they use a tank or container to hold and bring liquid to the coil. They usually hold significantly more e-liquid than their RDA counterparts. The tank can be either plastic, glass, or metal. An early form of tank atomizers was the Genesis style atomizers. They commonly use stainless steel mesh or rope for wicking material. The drawbacks of Genesis style atomizers include leaking if they are not not kept upright.

Rebuildable dripping atomizers (RDAs) on the other hand lack the container section and hold very little liquid compared to RTAs, but are usually a lot smaller. 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. A "top cap" to cover the coils with airflow holes and a hole at the top where a mouth piece can be attached. The wick is generally larger than 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 help 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.

Power

Most portable devices contain a rechargeable battery, which tends to be the largest component of an electronic cigarette.

First generation devices

First generation e-cigarettes commonly look like tobacco cigarettes and are thus called "cigalikes". 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 in the button or on the end may also be employed to indicate activation . Some manufacturers also have a cigarette pack-shaped portable charging case, which contains a larger battery capable of charging e-cigarettes.

Second generation devices

Aimed at more experienced users, these devices tend to look less like tobacco cigarettes. Some cheaper devices use a microphone to activate them. Other batteries, like Ego type batteries, can use a custom integrated circuit to indicate battery status on the included LCD and a button for activation.

Third generation devices

These are aimed at advanced users. This group includes mechanical mods and variable voltage devices and may include additional options, such as displays and support of a wide range of internal batteries and atomizer configurations.

Variable power and voltage devices

Variable power and or voltage are personal vaporizer devices that contain a built-in electronic chip allowing the user to adjust the power that goes through the heating element. They are often rectangular in shape but can also be cylindrical. They usually incorporate an LED screen to display information.The user presses buttons or rotates a dial to make adjustments in power either up or down. The amount of power has a direct relationship to the heat produced by the coil, thus changing the vapor output. Greater heat generated by the coil increases vapor production. Some of these devices include additional settings through their menu system such as: atomizer resistance checker, remaining battery voltage, puff counter, activation cut-off etc.

On September 2, 2014 E-Cig Advanced reported that Evolv Vapor had received a patent on variable wattage. Evolve was the company that introduced variable wattage to the industry. The technology goes all the way back to the Darwin, the companies first variable wattage device.

The DNA 40 is a control board can be used in devices that control variable wattage and voltage was released in October 2014. The DNA 40 is the first control board to monitor and control the temperature of the heating coil. Controlling temperature is important to limit charring of the wicking material and reduce the breakdown of flavoring and base liquid ingredients.

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 on the natural voltage output of a battery and the material that the mod is made of.

The term "mod" was originally used instead of "modification". Users would modify existing hardware to get better performance, and as an alternative to the e-cigarettes that looked like traditional cigarettes. Users would also modify other items like flashlights as battery compartments to power atomizers. Today the word mod is used to describe most personal vaporizers either bought in a store or created by the user.

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 have this possibility as well.

Since mechanical PVs have no power regulation and are 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 when heated by an atomizer produces mist. The main ingredients of e-liquids are usually a mix of propylene glycol (PG), glycerin (G), and/or polyethylene glycol 400 (PEG400), sometimes with differing levels of alcohol mixed with concentrated or extracted flavourings; and optionally, a variable concentration of tobacco-derived nicotine. Most e-cigarette liquids contain nicotine, but the level of nicotine is chosen by the consumer. E-liquid that does not contain nicotine is also available.

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 to modify or boost their flavour, nicotine strength, or concentration of e-liquid. 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 labelling for denoting nicotine concentration, and is sometimes shortened to a simple "mg". In surveys of regular e-cigarette users the most liked e-liquids had a nicotine content of 18 mg/ml, and largely the favorite flavors were tobacco, mint and fruit.

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. E-cigarette users most commonly continue to smoke traditional cigarettes. Many users report that electronic cigarettes help them either quit smoking or reduce the number of cigarettes smoked. Adults most frequently use electronic cigarettes as a replacement for tobacco, but not always to quit. Although some people have a desire to quit smoking by using e-cigarettes, other common explanations for the use of these products are to circumvent smoke-free laws, to reduce harm from smoking and to cut back on traditional cigarettes. Many have conveyed concern about the possibility that e-cigarettes may function as a "gateway" to using traditional cigarettes. Ethical concerns exist from e-cigarettes use among minors and their possibility to weaken efforts to reduce traditional cigarette use.

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 threefold increase from 2011 in the number of youth who have used electronic cigarettes who have never smoked. The majority of youth who use e-cigarettes also smoke combustible cigarettes.

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%. About 60% are smokers and most of the rest are ex-smokers.

A February 2014 survey in France 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.

Larger numbers of young people are starting to use e-cigarettes. There is a high number of youth who use e-cigarettes also smoking traditional cigarettes. Some youth who have tried an e-cigarette have never smoked a traditional cigarette, this shows that they can be a starting point for nicotine use for some youth and nicotine is an addictive drug. There is a high levels of use of both e-cigarettes and traditional cigarettes, no proven help with stopping smoking.

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. E-cigarette brands have been increasing advertising at a fast rate, the aggressive marketing used is similar to that used to sell cigarettes in the 1950s and 1960s. While advertising of tobacco products was banned long ago, television and radio e-cigarette advertising in a number of countries may be indirectly creating a desire for 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. 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.

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, called vape meets, are happening around the United States which focus around e-cig devices, accessories, and the life style that accompanies them. 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 manufacturers are not available.

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 of less than 1 ohm. This practice is known as "cloud-chasing". By using a coil at less that 1 ohm the batteries of PVs are stressed 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.

In November 2014 the Advertising Standards Authority changed regulations for electronic cigarettes in the UK. KiK Electronic Cigarettes aired the first commercial showing exhalation of mist from an e-cigarette on 10 November as new regulations were enforced.

Economics

Tobacco manufacturers initially dismissed electronic cigarettes as a fad; however, the purchase of blu by Lorillard for $135 million in April 2012 signalled their entry into the market. A national advertising campaign starred Steven Dorff exhaling a "thick flume" of what the ad describes as 'vapor, not tobacco smoke', exhorting smokers with the message "We are all adults here, it's time to take our freedom back." Jason Healy, founder of blu, called the product "a lifestyle brand for smokers." The ads, occurring against the backdrop of longstanding prohibition of tobacco advertising on television, were criticized by organizations such as Campaign for Tobacco-Free Kids as undermining anti-tobacco efforts. Cynthia Hallett of Americans for Non-Smokers' Rights described the advertising campaign as attempting to "re-establish a norm that smoking is okay, that smoking is glamorous and acceptable." University of Pennsylvania communications professor Joseph Cappella suggested that the sight of Dorff's exhaled smoke would induce tobacco smokers to consume cigarettes, even as the setting of the ad near an ocean was meant to suggest an association of clean air with the nicotine product.

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 (VTMs)" 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. There is no evidence that the cigarette brands are selling e-cigarettes as part of a plan to phase out traditional cigarettes, despite some claiming to want to cooperate in "harm reduction."

There is concern with some financial analysts that the rapid growth of the e-cigarette market is accelerating the decline of $87 billion outstanding in tobacco bonds. States with large populations, such as New York and California, are affected to a greater degree than others.

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 (PMI) 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 mist.
• HeatSticks is a heated tobacco product marketed under the brand Marlboro by PMI.

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External links

• Media related to Electronic cigarettes at Wikimedia Commons

• Cigarette types
• Technology
• Chinese inventions
• Smoking cessation
• 2003 introductions