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The aerosol of electronic cigarettes is generated when the e-liquid reaches a temperature of roughly 100-250 °C within a chamber.^[1] The user inhales the aerosol, commonly called vapor, rather than cigarette smoke.^[2] The aerosol provides a flavor and feel similar to tobacco smoking.^[3] In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas.^[2] The aerosol is made-up of liquid sub-micron particles of condensed vapor,^[4] which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals.^[5] After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.^[2] The particle size distribution and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range (modes, ≈100–200).^[6] The particles are of the ultrafine size which can go deep in the lungs and then into the systemic circulation.^[6] These nanoparticles can deposit in the lung's alveolar sacs, potentially leading to local respiratory toxicity.^[6]

After the aerosol is inhaled, it is exhaled.^[2] Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different^[5] The particles are larger, with the mean size being 600 nm in inhaled aerosol and 300 nm in exhaled vapor.^[7] Bystanders are exposed to these particles from exhaled e-cigarette vapor.^[6] There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects.^[8]^[9]^[10] Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted.^[11] Thus, cardiocirculatory effects caused by carbon monoxide are not likely.^[11] E-cigarette use by a parent might lead to inadvertent health risks to offspring.^[12] E-cigarettes pose many safety concerns to children.^[12] For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.^[12]

E-liquid is the mixture used in vapor products such as electronic cigarettes.^[13] The main ingredients in the e-liquid usually are propylene glycol, glycerin, nicotine, and flavorings.^[14] However, there are e-liquids sold without propylene glycol, nicotine, or flavors.^[13]^[15]^[16] The liquid typically contains 95% propylene glycol and glycerin.^[17] The flavorings may be natural or artificial.^[7] About 8,000 flavors exist as of 2014.^[18] There are many e-liquids manufacturers in the USA and worldwide.^[19] While there are currently no US Food and Drug Administration (FDA) manufacturing standards for e-liquid, the FDA has proposed regulations that are expected to be finalized in late 2015.^[20] Industry standards have been created and published by the American E-liquid Manufacturing Standards Association (AEMSA).^[21]

Composition

Aerosol

The vapor usually contains nicotine, glycerin, propylene glycol, flavors and aroma transporters.^[22] The nicotine levels in the vapor varies either from puff-to-puff or among products of the same company.^[2] A 2015 report commissioned by Public Health England concluded that e-cigarettes "release negligible levels of nicotine into ambient air".^[23] E-cigarettes without nicotine are also available.^[24] The vapor may also contain tiny amounts of toxicants, carcinogens, and heavy metals.^[22]^[6] Contamination with various chemicals has been identified.^[7] E-cigarette makers do not fully disclose information on the chemicals that can be released or synthesized during use.^[2] The metals have been found in trace amounts in the vapor, some of them at higher amounts than in cigarette smoke.^[5]

E-liquid

E-liquid,^[25] e-fluid, or e-juice^[26] is the mixture used in vapor products including e-cigarettes.^[13] E-Liquids come in many variations, including different nicotine strengths and many different flavors.^[27] The main ingredients are propylene glycol, glycerin, and flavorings; and most often, nicotine in liquid form.^[14] The liquid typically contains 95% propylene glycol and glycerin, and the remaining 5% being flavorings and nicotine.^[17] E-liquid can be made with or without nicotine, with >90% of e-liquids containing some level of nicotine.^[28] The most regularly used base carrier chemical is propylene glycol with or without glycerin.^[6] E-liquid containing glycerin and water made without propylene glycol are also sold.^[13] It is uncertain whether the nicotine used in e-liquid is manufactured using a United States Pharmacopeia (USP) grade nicotine, a tobacco plant extract, tobacco dust or a synthetic nicotine.^[29] Most e-cigarette liquids contain nicotine, but the level of nicotine varies depending on user-preference and manufacturers.^[24] Although some e-juice is nicotine-free, surveys demonstrate that 97% of responders use products that contain nicotine.^[15] A 2015 review suggests that 1% of users use liquid without nicotine.^[30]

Aerosol

The primary parts that make up an e-cigarette are a mouthpiece, a cartridge (tank), a heating element/atomizer, a microprocessor, a battery, and possibly a LED light on the end.^[31] An atomizer comprises a small heating element that vaporizes e-liquid and wicking material that draws liquid onto the coil.^[32] When the user pushes a button.^[33] or inhales a pressure sensor activates the heating element that atomizes the liquid solution;^[34] The e-liquid reaches a temperature of roughly 100-250 °C within a chamber to create an aerosolized vapor.^[1] The user inhales the aerosol, commonly called vapor, rather than cigarette smoke.^[2] The aerosol provides a flavor and feel similar to tobacco smoking.ref name=Caponnetto2012>Caponnetto, Pasquale; Campagna, Davide; Papale, Gabriella; Russo, Cristina; Polosa, Riccardo (2012). "The emerging phenomenon of electronic cigarettes". Expert Review of Respiratory Medicine. 6 (1): 63–74. doi:10.1586/ers.11.92. ISSN 1747-6348. PMID 22283580.</ref> However, variable voltage devices can raise the temperature where the user adjusts the vapor.^[7] The vapor contains similar chemicals to the e-liquid which vary in composition and concentration across and within manufacturers.^[2]^[7]

First Hand

E-cigarettes produce particles, in the form of an aerosol.^[2]^[4] In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas.^[2] The aerosol is made-up of liquid sub-micron particles of condensed vapor,^[4] which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals.^[5] This aerosol that is produces resembles cigarette smoke.^[2] After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.^[2]

The particle size distribution and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range (modes, ≈100–200).^[6] A 2014 review found that 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.^[6] They found that because these things are uncertain, it is not clear whether the ultrafine particles in e-cigarette vapor have health effects similar to those produced by traditional cigarettes.^[6] A 2014 WHO report found e-cigarettes release a lower level of particles than traditional cigarettes.^[35] Comparable to a traditional cigarette, e-cigarette particles are tiny enough to enter the alveoli, enabling nicotine absorption.^[26] The particles are of the ultrafine size which can go deep in the lungs and then into the systemic circulation.^[6] These nanoparticles can deposit in the lung's alveolar sacs, potentially leading to local respiratory toxicity.^[6] E-cigarettes companies assert that the particulates produced by an e-cigarette are too tiny to be deposited in the alveoli.^[36] Exactly what comprises the vapor varies in composition and concentration across and within manufacturers.^[2] Different devices generate different particle sizes and cause different depositions in the respiratory tract, even from the same nicotine liquid.^[37] Reports in the literature have shown respiratory and cardiovascular effects by these smaller size particles, suggesting a possible health concern.^[38]

Second Hand

After the aerosol is inhaled, it is exhaled.^[2] Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different^[5] The particles are larger, with the mean size being 600 nm in inhaled aerosol and 300 nm in exhaled vapor.^[7] The exhaled aerosol particle concentration is 5 times lower from an e-cigarette than from a traditional cigarette.^[39] The density of particles in the vapor is lower than in cigarette smoke by a factor of between 6 and 880 times lower.^[5]

For particulate matter emissions, e-cigarettes slightly exceeded the WHO guidelines, but emissions were 15 times less than traditional cigarette use.^[40] In January 2014, the International Union Against Tuberculosis and Lung Disease stated "Adverse health effects for exposed third parties (second-hand exposure) cannot be excluded because the use of electronic cigarettes leads to emission of fine and ultrafine inhalable liquid particles, nicotine and cancer-causing substances into indoor air."^[41] The dense vapor consists of liquid sub-micron droplets.^[4]^{[dead link]}

Exposure

Since e-cigarettes have not been widely used long enough for evaluation, the long-term health effects from the second-hand vapor are not known.^[6] There is insufficient data to determine the impact on public health from e-cigarettes.^[42] The potential harm to bystanders from e-cigarettes is unknown.^[43] This is because no long-term data is available.^[22]

Since e-cigarettes do not burn (or contain) tobacco, no side-stream smoke or any cigarette smoke is produced.^[6] Only what is exhaled by e-cigarettes users enters the surrounding air.^[22] Exhaled vapor consists of nicotine and some other particles, primarily consisting of flavors, aroma transporters, glycerin and propylene glycol.^[22] Bystanders are exposed to these particles from exhaled e-cigarette vapor.^[6] A mixture of harmful substances, particularly nicotine, ultrafine particles, and volatile organic compounds can be exhaled into the air.^[44] The liquid particles condenses into a viewable fog.^[7] The vapor 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.^[7] This is because of fast revaporization at room temperature.^[7]

There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects.^[8]^[10] Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted.^[11] Thus, cardiocirculatory effects caused by carbon monoxide are not likely.^[11] However, in an experimental study, e-cigarettes increased levels of carcinogenic polycyclic aromatic hydrocarbons in the surrounding air.^[11]

E-cigarettes used in indoor environments can put at risk nonsmokers to elevated levels of nicotine and aerosol emissions.^[39] 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.^[6] 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.^[6] In 2015 a report commissioned by Public Health England concluded that e-cigarettes "release negligible levels of nicotine into ambient air with no identified health risks to bystanders".^[23]

A 2014 review of limited data concluded this vapor can cause indoor air pollution and is not just water vapor as is frequently stated in the advertising of e-cigarettes.^[6] A 2014 practice guideline by NPS MedicineWise states, "Although data on health effects of passive vapour are currently lacking, the risks are argued to be small, but claims that e-cigarettes emit only water vapour are nevertheless incorrect. Serum cotinine levels (a metabolite of nicotine) have been found to be similar in bystanders exposed to either e-cigarette vapour or cigarette smoke."^[45] The 2015 California Department of Public Health has reported that "Mainstream and secondhand e-cigarette aerosol has been found to contain at least ten chemicals that are on California’s Proposition 65 list of chemicals known to cause cancer, birth defects, or other reproductive harm."^[46] However, it has been demonstrated that e-cigarettes causes nonusers to be exposed to nicotine but not to tobacco-related combustion toxicants.^[8]

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.^[38] They urged indoors restrictions similar to smoking bans, until research has shown the aerosol has no risk of harm.^[38] A 2014 review indicated that the levels of inhaled contaminants from the e-cigarette vapor are not of significant health concern for human exposures by the standards used in workplaces to ensure safety.^[24] The use of e-cigarettes in a smoke-free area could expose non-users to toxins.^[47] The effect on bystanders would likely be much less harmful than traditional cigarettes.^[22]

2014 WHO report stated passive exposure was as a concern, indicating that current evidence is insufficient to determine whether the levels of exhaled vapor are safe to involuntarily exposed bystanders.^[35] The report stated that "it is unknown if the increased exposure to toxicants and particles in exhaled aerosol will lead to an increased risk of disease and death among bystanders."^[35] The British Medical Association (BMA) reported in 2013 that there are "concerns that the use of e-cigarettes could threaten the norm of not smoking in public places and workplaces."^[48]

As of 2013^[update], the only clinical study currently published evaluating the respiratory effects of passive vaping found no adverse effects were detected.^[5] A 2014 review found it is safe to infer that their effects on bystanders are minimal in comparison to traditional cigarettes.^[5] A E-cigarette vapor has notably fewer toxicants than cigarette smoke and is likely to pose less harm to users or bystanders.^[6]

Third hand

E-cigarette use by a parent might lead to inadvertent health risks to offspring.^[12] E-cigarettes pose many safety concerns to children.^[12] For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.^[12] A policy statement by the American Association for Cancer Research and the American Society of Clinical Oncology has reported that "Third-hand exposure occurs when nicotine and other chemicals from second-hand aerosol deposit on surfaces, exposing people through touch, ingestion, and inhalation".^[15] Public health England, looking at the available research said the amount of nicotine deposited was low and that an infant would have to lick 30 square meters to be exposed to 1mg of nicotine.^[23] The statement noted there are no published studies of third hand exposure from e-cigarettes, however initial data suggests that nicotine from e-cigarettes may stick to surfaces and would be hard to remove.^[15] I

Eliquid

The e-liquid is sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own e-juices.^[49] Some vendors of e-liquids, offer options to change the amounts of flavorings or nicotine strengths, and build each bottle customized for the purchaser.^[50] E-liquids are made with various tobacco, fruit, and other flavors,^[6] as well as variable nicotine concentrations (including nicotine-free versions).^[14] The standard notation "mg/ml" is often used on labels to denote nicotine concentration, and is sometimes shortened to "mg".^[51] 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.^[22] A cartridge may contain 0 to 20 mg of nicotine.^[44] EU regulations cap the concentration of nicotine in e-liquid at a maximum of 20 mg/mL.^[26] A refill bottle can contain up to 1 g of nicotine.^[44] Refill liquids are often sold in the size range from 15 to 30 mL.^[52] One cartridge may typically last as long as one pack of cigarettes.^[53] Some liquids without flavoring is also sold.^[16] The flavorings may be natural or artificial.^[7] About 8,000 flavors exist as of 2014.^[18] A user does not normally consume a whole cartridge in a single session.^[54] Most e-liquids are produced by a few manufacturers in China, the US and Europe.^[22] An e-cigarette user will usually obtain 300 to 500 puffs per mL of liquid.^[52]

Manufacturing

E-liquids are manufactured by many producers, both in the US and across the world.^[19] First tier manufacturers use lab suits, gloves, hair covers, inside of certified clean rooms with air filtration similar to pharmaceutical-grade production areas.^[19]

Standards

Standards for e-liquid manufacturing have been created by American E-liquid Manufacturing Standards Association (AEMSA), which is trade association dedicated to creating responsible and sustainable standards for the safe manufacturing of e-liquids used in vapor products.^[55] AEMSA has published a comprehensive list standards and best known methods, which are openly available for use by any manufacturer of e-Liquids. The AEMSA standards cover nicotine, ingredients, sanitary manufacturing rooms, safety packaging, age restrictions, and labeling.^[21]

Regulation

There are no current governmental or US Food and Drug Administration (FDA) manufacturing standards for e-liquid.^[20] The FDA has sought to regulate e-liquid through use of the Tobacco Control Act, passed into law in 2009.^[20] In April of 2014, the FDA issued it's "Deeming" proposals for public comment, which would cover e-liquids manufacturing. The Final Rule, (in final form) giving the FDA authority to regulate e-liquids is anticipated to be released in late 2015, or early 2016.^[20]

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^ "E-liquid Mixing Guide – a Guide to DIY Mixing". Ecigarette Mag. Retrieved 10 November 2014.
^ Murray Laugesen (17 October 2007). "The Ruyan e-cigarette; Technical Information Sheet". Health New Zealand. Retrieved 31 March 2008.
^ ^a ^b Hildick-Smith, Gordon J.; Pesko, Michael F.; Shearer, Lee; Hughes, Jenna M.; Chang, Jane; Loughlin, Gerald M.; Ipp, Lisa S. (2015). "A Practitioner's Guide to Electronic Cigarettes in the Adolescent Population". Journal of Adolescent Health. doi:10.1016/j.jadohealth.2015.07.020. ISSN 1054-139X. PMID 26422289.
^ Odum, L. E.; O'Dell, K. A.; Schepers, J. S. (2012). "Electronic Cigarettes: Do They Have a Role in Smoking Cessation?". Journal of Pharmacy Practice. 25 (6): 611–614. doi:10.1177/0897190012451909. ISSN 0897-1900. PMID 22797832.
^ Pepper, J. K.; Brewer, N. T. (2013). "Electronic nicotine delivery system (electronic cigarette) awareness, use, reactions and beliefs: a systematic review". Tobacco Control. 23 (5): 375–384. doi:10.1136/tobaccocontrol-2013-051122. ISSN 0964-4563. PMID 24259045.
^ "About AEMSA". AEMSA. Retrieved 2015-11-23.

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[Cheng2014-2] ^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ Cheng, T. (2014). "Chemical evaluation of electronic cigarettes". Tobacco Control. 23 (Supplement 2): ii11–ii17. doi:10.1136/tobaccocontrol-2013-051482. ISSN 0964-4563. PMC 3995255. PMID 24732157. Cite error: The named reference "Cheng2014" was defined multiple times with different content (see the help page).

[Caponnetto2012-3] Caponnetto, Pasquale; Campagna, Davide; Papale, Gabriella; Russo, Cristina; Polosa, Riccardo (2012). "The emerging phenomenon of electronic cigarettes". Expert Review of Respiratory Medicine. 6 (1): 63–74. doi:10.1586/ers.11.92. ISSN 1747-6348. PMID 22283580.

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+[[File:Electronic Cigarette Smoking.jpg|thumb|[[Aerosol]] ([[vapor]]) exhaled by an e-cigarette user.]]The aerosol of electronic cigarettes is generated when the e-liquid reaches a temperature of roughly 100-250&nbsp;°C within a chamber.<ref name="Rowell2015">{{cite journal|last1=Rowell|first1=Temperance R|last2=Tarran|first2=Robert|title=Will Chronic E-Cigarette Use Cause Lung Disease?|journal=American Journal of Physiology - Lung Cellular and Molecular Physiology|year=2015|pages=ajplung.00272.2015|issn=1040-0605|doi=10.1152/ajplung.00272.2015|pmid=26408554}}</ref>
-{{merge from|E-liquid|discuss=Talk:Electronic cigarette#New article|date=November 2015}}
+ The user inhales the [[aerosol]], commonly called [[vapor]], rather than [[cigarette smoke]].<ref name="Cheng2014" /> The aerosol provides a flavor and feel similar to [[tobacco smoking]].<ref name=Caponnetto2012>{{cite journal |last1=Caponnetto |first1=Pasquale |last2=Campagna |first2=Davide |last3=Papale |first3=Gabriella |last4=Russo |first4=Cristina |last5=Polosa |first5=Riccardo |title=The emerging phenomenon of electronic cigarettes |journal=Expert Review of Respiratory Medicine |volume=6 |issue=1 |year=2012 |pages=63–74 |issn=1747-6348 |doi=10.1586/ers.11.92 |pmid=22283580}}</ref> In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas.<ref name="Cheng2014">{{cite journal|last1=Cheng|first1=T.|title=Chemical evaluation of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii11–ii17|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051482|pmc=3995255|pmid=24732157}}</ref> The aerosol is made-up of liquid sub-micron particles of condensed vapor,<ref name="Offermann2014">{{cite journal|last1=Offermann|first1=Francis|title=The Hazards of E-Cigarettes|journal=ASHRAE Journal|date=June 2014|volume=56|issue=6|url=http://www.gocolumbiamo.com/Health/Documents/Offermann-Thehazardsofe-cigarettes.pdf}}</ref> which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals.<ref name="FarsalinosPolosa2014" /> After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.<ref name="Cheng2014" /> The particle size distribution and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range (modes, ≈100–200).<ref name="Grana2014" /> The [[ultrafine particle|particles are of the ultrafine size]] which can go deep in the lungs and then into the [[systemic circulation]].<ref name="Grana2014" /> These [[nanoparticle]]s can deposit in the [[pulmonary alveoli|lung's alveolar sacs]], potentially leading to local respiratory toxicity.<ref name="Grana2014" />[[File:Various E-liquid Bottles.jpg|thumb|Various bottles of e-liquid.]]After the aerosol is inhaled, it is exhaled.<ref name="Cheng2014" /> Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different<ref name="FarsalinosPolosa2014" /> The particles are larger, with the mean size being 600&nbsp;nm in inhaled aerosol and 300&nbsp;nm in exhaled vapor.<ref name="Bertholon2013" />  Bystanders are exposed to these particles from exhaled e-cigarette vapor.<ref name="Grana2014" /> There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects.<ref name="Rom2014">{{cite journal|last1=Rom|first1=Oren|last2=Pecorelli|first2=Alessandra|last3=Valacchi|first3=Giuseppe|last4=Reznick|first4=Abraham Z.|title=Are E-cigarettes a safe and good alternative to cigarette smoking?|journal=Annals of the New York Academy of Sciences|volume=1340|issue=1|year=2014|pages=65–74|issn=00778923|doi=10.1111/nyas.12609|pmid=25557889}}</ref><ref name="Yang2014">{{cite journal|last1=Yang|first1=L.|last2=Rudy|first2=S. F.|last3=Cheng|first3=J. M.|last4=Durmowicz|first4=E. L.|title=Electronic cigarettes: incorporating human factors engineering into risk assessments|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii47–ii53|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051479|pmid=24732164}}</ref><ref name="KleinstreuerFeng2013">{{cite journal|last1=Kleinstreuer|first1=Clement|last2=Feng|first2=Yu|title=Lung Deposition Analyses of Inhaled Toxic Aerosols in Conventional and Less Harmful Cigarette Smoke: A Review|journal=International Journal of Environmental Research and Public Health|volume=10|issue=9|year=2013|pages=4454–4485|issn=1660-4601|doi=10.3390/ijerph10094454|pmid=24065038}}</ref> Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted.<ref name="Nowak2014" /> Thus, cardiocirculatory effects caused by carbon monoxide are not likely.<ref name="Nowak2014" /> E-cigarette use by a parent might lead to inadvertent health risks to offspring.<ref name=England2015>{{cite journal|last1=England|first1=Lucinda J.|last2=Bunnell|first2=Rebecca E.|last3=Pechacek|first3=Terry F.|last4=Tong|first4=Van T.|last5=McAfee|first5=Tim A.|title=Nicotine and the Developing Human|journal=American Journal of Preventive Medicine|year=2015|issn=07493797|doi=10.1016/j.amepre.2015.01.015|pmid=25794473}}</ref> E-cigarettes pose many safety concerns to children.<ref name="England2015" /> For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.<ref name="England2015" />
-The '''[[aerosol]]''' from '''[[electronic cigarette]]s''', commonly known as [[vapor]], contains various levels of [[chemical]]s.<ref name=Cheng2014/> The e-cigarette vapor simulates [[cigarette smoke]], but without tobacco combustion.<ref name=Caponnetto2012>{{cite journal|last1=Caponnetto|first1=Pasquale|last2=Campagna|first2=Davide|last3=Papale|first3=Gabriella|last4=Russo|first4=Cristina|last5=Polosa|first5=Riccardo|title=The emerging phenomenon of electronic cigarettes|journal=Expert Review of Respiratory Medicine|volume=6|issue=1|year=2012|pages=63–74|issn=1747-6348|doi=10.1586/ers.11.92|pmid=22283580}}</ref> E-cigarettes do not produce vapor between puffs.<ref>{{cite web|title=Supporting regulation of electronic cigarettes|url=http://www.apha.org/policies-and-advocacy/public-health-policy-statements/policy-database/2015/01/05/12/58/supporting-regulation-of-electronic-cigarettes|website=www.apha.org|publisher=American Public Health Association|location=US|date=18 November 2014}}</ref> The levels of [[nicotine]], [[tobacco-specific nitrosamines]] (TSNAs), [[aldehyde]]s, metals, [[volatile organic compounds]] (VOCs), [[flavor#Flavorants or flavorings|flavors]], and tobacco alkaloids in e-cigarette vapors vary greatly.<ref name=Cheng2014/> Specifically what comprises the vapor varies across and within manufacturers.<ref name=Cheng2014/>
+E-liquid is the mixture used in [[Vaporizer (inhalation device)|vapor products]] such as [[electronic cigarette]]s.<ref name=Kacker2014/> The main ingredients in the e-liquid usually are [[propylene glycol]], [[glycerol|glycerin]], [[nicotine]], and [[Flavor#Flavorants or flavorings|flavorings]].<ref name=Caponnetto2013/> However, there are e-liquids sold without propylene glycol, nicotine, or flavors.<ref name=Kacker2014/><ref name=Brandon2015/><ref name=Cochrane2014/> The liquid typically contains 95% propylene glycol and glycerin.<ref name=Ruiz2014/> The flavorings may be natural or artificial.<ref name=Bertholon2013/> About 8,000 flavors exist as of 2014.<ref name=WHO2014/> There are many e-liquids manufacturers in the USA and worldwide.<ref name=Blackwell2015/> While there are currently no US [[Food and Drug Administration]] (FDA) manufacturing standards for e-liquid, the FDA has proposed regulations that are expected to be finalized in late 2015.<ref name=FDA2015/> Industry standards have been created and published by the American E-liquid Manufacturing Standards Association (AEMSA).<ref name=AEMSA2015/>
-Once vaporized the ingredients in the e-liquid go through [[chemical reaction]]s that form new compounds not found in the initial liquid.<ref name=Cooke2015/> Many chemicals including [[carbonyl compounds]] such as [[formaldehyde]] can inadvertently be produced when the [[nichrome wire]] (heating element) that touches the e-liquid is heated and chemically reacts with the liquid.<ref name=Bekki2014/> While propylene glycol-containing liquids produced the most amounts of carbonyls in e-cigarette vapors,<ref name=Bekki2014/> many e-cigarettes companies are using water and [[glycerol|glycerin]] instead of propylene glycol for vapor production.<ref name=Kacker2014/>
+== Composition ==
-A review found propylene glycol and glycerin are [[oxidized]] to create aldehydes comparable to cigarette smoke when heated and [[aerosolized]] at a [[voltage]] higher than 3 volts.<ref name=Cheng2014/> Depending on the heating temperature, the [[carcinogenic]]s may surpass the levels of cigarette smoke.<ref name=Cooke2015/> Reduced voltage e-cigarettes generate very low levels of formaldehyde.<ref name=Bekki2014/> A [[Public Health England]] report found "At normal settings, there was no or negligible formaldehyde release."<ref name=McNeill201577/> They concluded that "There is no indication that EC users are exposed to dangerous levels of aldehydes."<ref name=McNeill201577/> A review found that "As e-cigarette manufacturing changes, the newer and "hotter" products may expose patients to higher levels of known carcinogens."<ref name=Orellana-Barrios2015/>
-==Chemicals==
+==== Aerosol ====
+The vapor usually contains [[nicotine]], [[glycerol|glycerin]], [[propylene glycol]], [[flavor#Flavorants or flavorings|flavors]] and aroma transporters.<ref name="Hajek2014">{{cite journal|last1=Hajek|first1=P|last2=Etter|first2=JF|last3=Benowitz|first3=N|last4=Eissenberg|first4=T|last5=McRobbie|first5=H|title=Electronic cigarettes: review of use, content, safety, effects on smokers and potential for harm and benefit.|url=http://tobonline.com/Media/Default/Article/Addiction-%20Hajek%2014.pdf|journal=Addiction (Abingdon, England)|date=31 July 2014|pmid=25078252|doi=10.1111/add.12659|volume=109|issue=11|pages=1801–10}}</ref> The nicotine levels in the vapor varies either from puff-to-puff or among products of the same company.<ref name="Cheng2014" /> A 2015 report commissioned by [[Public Health England]] concluded that e-cigarettes "release negligible levels of nicotine into ambient air".<ref name="McNeill201565">{{cite web|last1=McNeill|first1=A, SC|title=E - cigarettes: an evidence update A report commissioned by Public Health England|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/454516/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England.pdf|website=www.gov.uk|publisher=Public Health England|page=65|accessdate=20 August 2015|location=UK|date=2015}}</ref> E-cigarettes without nicotine are also available.<ref name="Bur2014">{{cite journal|last1=Burstyn|first1=I|title=Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks.|journal=BMC Public Health|date=9 January 2014|volume=14|pages=18|doi=10.1186/1471-2458-14-18|pmc=3937158|pmid=24406205}}</ref> The vapor may also contain tiny amounts of [[toxicant]]s, [[carcinogen]]s, and [[heavy metals]].<ref name="Hajek2014" /><ref name="Grana2014">{{cite journal|last=Grana|first=R|author2=Benowitz, N |author3=Glantz, SA |title=E-cigarettes: a scientific review.|journal=Circulation|date=13 May 2014|volume=129|issue=19|pages=1972–86|doi=10.1161/circulationaha.114.007667|pmc=4018182|pmid=24821826}}</ref> Contamination with various chemicals has been identified.<ref name="Bertholon2013">{{cite journal|last1=Bertholon|first1=J.F.|last2=Becquemin|first2=M.H.|last3=Annesi-Maesano|first3=I.|last4=Dautzenberg|first4=B.|title=Electronic Cigarettes: A Short Review|journal=Respiration|year=2013|issn=1423-0356|volume=86|pages=433–8|doi=10.1159/000353253|pmid=24080743}}</ref>  E-cigarette makers do not fully disclose information on the chemicals that can be released or synthesized during use.<ref name="Cheng2014" /> The metals have been found in trace amounts in the vapor, some of them at higher amounts than in [[cigarette smoke]].<ref name="FarsalinosPolosa2014">{{cite journal|last1 = Farsalinos|first1 = K. E.|last2 = Polosa|first2 = R.|title = Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review|journal = Therapeutic Advances in Drug Safety|volume = 5|issue = 2|year = 2014|pages = 67–86|issn = 2042-0986|doi = 10.1177/2042098614524430|pmc = 4110871|pmid = 25083263}}</ref>
+==== E-liquid ====
-[[File:Electronic Cigarette Smoking.jpg|thumb|[[Aerosol]] ([[vapor]]) exhaled by an e-cigarette user.]]
+E-liquid,<ref name="Weaver2014">{{cite journal|last1=Weaver|first1=Michael|last2=Breland|first2=Alison|last3=Spindle|first3=Tory|last4=Eissenberg|first4=Thomas|title=Electronic cigarettes: a review of safety and clinical issues|journal=Journal of Addiction Medicine|volume=8|issue=4|year=2014|pages=234–240|issn=1932-0620|doi=10.1097/ADM.0000000000000043|pmid=25089953}}</ref> e-fluid, or e-juice<ref name="EbbertAgunwamba2015">{{cite journal|last1=Ebbert|first1=Jon O.|last2=Agunwamba|first2=Amenah A.|last3=Rutten|first3=Lila J.|title=Counseling Patients on the Use of Electronic Cigarettes|journal=Mayo Clinic Proceedings|volume=90|issue=1|year=2015|pages=128–134|issn=00256196|doi=10.1016/j.mayocp.2014.11.004|pmid=25572196}}</ref> is the mixture used in vapor products including e-cigarettes.<ref name="Kacker2014" /> E-Liquids come in many variations, including different nicotine strengths and many different flavors.<ref name="Bekki2014">{{cite journal|last1=Bekki|first1=Kanae|last2=Uchiyama|first2=Shigehisa|last3=Ohta|first3=Kazushi|last4=Inaba|first4=Yohei|last5=Nakagome|first5=Hideki|last6=Kunugita|first6=Naoki|title=Carbonyl Compounds Generated from Electronic Cigarettes|journal=International Journal of Environmental Research and Public Health|volume=11|issue=11|year=2014|pages=11192–11200|issn=1660-4601|doi=10.3390/ijerph111111192|pmid=25353061}}</ref> The main ingredients are [[propylene glycol]], [[glycerol|glycerin]], and [[Flavor#Flavorants or flavorings|flavorings]]; and most often, [[nicotine]] in liquid form.<ref name="Caponnetto2013">{{cite journal|title=Electronic cigarette: a possible substitute for cigarette dependence.|journal=Monaldi archives for chest disease|date=Mar 2013|author1=Caponnetto P|author2=Russo C|author3=Bruno CM|author4=Alamo A|author5=Amaradio MD|author6=Polosa R.|volume=79|issue=1|pages=12–19|pmid=23741941}}</ref> The liquid typically contains 95% propylene glycol and glycerin, and the remaining 5% being flavorings and nicotine.<ref name="Ruiz2014">{{cite journal|last1=Jimenez Ruiz|first1=CA|last2=Solano Reina|first2=S|last3=de Granda Orive|first3=JI|last4=Signes-Costa Minaya|first4=J|last5=de Higes Martinez|first5=E|last6=Riesco Miranda|first6=JA|last7=Altet Gómez|first7=N|last8=Lorza Blasco|first8=JJ|last9=Barrueco Ferrero|first9=M|last10=de Lucas Ramos|first10=P|title=The electronic cigarette. Official statement of the Spanish Society of Pneumology and Thoracic Surgery (SEPAR) on the efficacy, safety and regulation of electronic cigarettes.|journal=Archivos de bronconeumologia|date=August 2014|volume=50|issue=8|pages=362–7|pmid=24684764|doi=10.1016/j.arbr.2014.06.007}}</ref> E-liquid can be made with or without nicotine, with >90% of e-liquids containing some level of nicotine.<ref>{{Cite web|url = http://roar.uel.ac.uk/1875/1/2013_Dawkins_e-cig_survey.pdf|title = Vaping’ profiles and preferences: an online survey of electronic cigarette users|date = |accessdate = |website = |publisher = School of Psychology-University of East London|last = Lynne Dawkins, John Turner, Amanda Roberts and Kirstie Soar|first = }}</ref> The most regularly used base carrier chemical is propylene glycol with or without glycerin.<ref name="Grana2014">{{cite journal|last=Grana|first=R|author2=Benowitz, N |author3=Glantz, SA |title=E-cigarettes: a scientific review.|journal=Circulation|date=13 May 2014|volume=129|issue=19|pages=1972–86|doi=10.1161/circulationaha.114.007667|pmc=4018182|pmid=24821826}}</ref> E-liquid containing glycerin and water made without propylene glycol are also sold.<ref name="Kacker2014">{{cite journal|last1=Oh|first1=Anne Y.|last2=Kacker|first2=Ashutosh|title=Do electronic cigarettes impart a lower potential disease burden than conventional tobacco cigarettes?: Review on e-cigarette vapor versus tobacco smoke|journal=The Laryngoscope|date=December 2014|volume=124|issue=12|pages=2702–2706|doi=10.1002/lary.24750|pmid=25302452}}</ref> It is uncertain whether the nicotine used in e-liquid is manufactured using a [[United States Pharmacopeia]] (USP) grade nicotine, a tobacco plant extract, tobacco dust or a synthetic nicotine.<ref name="Chang2014">{{cite journal|last1=Chang|first1=H.|title=Research gaps related to the environmental impacts of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii54–ii58|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051480|pmc=3995274|pmid=24732165}}</ref> Most e-cigarette liquids contain nicotine, but the level of nicotine varies depending on user-preference and manufacturers.<ref name="Bur2014">{{cite journal|last1 = Burstyn|first1 = I|title = Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks.|journal = BMC Public Health|date = 9 January 2014|volume = 14|pages = 18|doi = 10.1186/1471-2458-14-18|pmc = 3937158|pmid = 24406205}}</ref> Although some e-juice is nicotine-free, surveys demonstrate that 97% of responders use products that contain nicotine.<ref name="Brandon2015">{{cite journal|last1=Brandon|first1=T. H.|last2=Goniewicz|first2=M. L.|last3=Hanna|first3=N. H.|last4=Hatsukami|first4=D. K.|last5=Herbst|first5=R. S.|last6=Hobin|first6=J. A.|last7=Ostroff|first7=J. S.|last8=Shields|first8=P. G.|last9=Toll|first9=B. A.|last10=Tyne|first10=C. A.|last11=Viswanath|first11=K.|last12=Warren|first12=G. W.|title=Electronic Nicotine Delivery Systems: A Policy Statement from the American Association for Cancer Research and the American Society of Clinical Oncology|journal=Clinical Cancer Research|url=http://clincancerres.aacrjournals.org/content/early/2015/01/08/1078-0432.CCR-14-2544.full.pdf+html|year=2015|volume=21|pages=514–525|issn=1078-0432|doi=10.1158/1078-0432.CCR-14-2544|pmid=25557889}}</ref> A 2015 review suggests that 1% of users use liquid without nicotine.<ref name="Born2015">{{cite journal|last1=Born|first1=H.|last2=Persky|first2=M.|last3=Kraus|first3=D. H.|last4=Peng|first4=R.|last5=Amin|first5=M. R.|last6=Branski|first6=R. C.|title=Electronic Cigarettes: A Primer for Clinicians|journal=Otolaryngology -- Head and Neck Surgery|year=2015|issn=0194-5998|doi=10.1177/0194599815585752|pmid=26002957}}</ref>
-[[File:NNK chemical structure.png|thumb|The [[NNK|nicotine-derived nitrosamine ketone]] (NNK) [[molecule]].]]
-The liquid within the chamber of [[electronic cigarette|e-cigarettes]] is heated to roughly 100-250&nbsp;°C to create an [[aerosolized]] vapor.<ref name=Rowell2015>{{cite journal|last1=Rowell|first1=Temperance R|last2=Tarran|first2=Robert|title=Will Chronic E-Cigarette Use Cause Lung Disease?|journal=American Journal of Physiology - Lung Cellular and Molecular Physiology|year=2015|pages=ajplung.00272.2015|issn=1040-0605|doi=10.1152/ajplung.00272.2015|pmid=26408554}}</ref> However, variable voltage devices can raise the temperature where the user adjusts the vapor.<ref name=Bertholon2013/> The vapor contains similar chemicals to the e-liquid which vary in composition and concentration across and within manufacturers.<ref name=Cheng2014/><ref name=Bertholon2013/> One review found that the vapor usually contains [[nicotine]], [[glycerol|glycerin]], [[propylene glycol]], [[flavor#Flavorants or flavorings|flavors]] and aroma transporters.<ref name=Hajek2014>{{cite journal|last1=Hajek|first1=P|last2=Etter|first2=JF|last3=Benowitz|first3=N|last4=Eissenberg|first4=T|last5=McRobbie|first5=H|title=Electronic cigarettes: review of use, content, safety, effects on smokers and potential for harm and benefit.|url=http://tobonline.com/Media/Default/Article/Addiction-%20Hajek%2014.pdf|journal=Addiction (Abingdon, England)|date=31 July 2014|pmid=25078252|doi=10.1111/add.12659|volume=109|issue=11|pages=1801–10}}</ref> The review also concluded that the nicotine levels in the vapor varies either from puff-to-puff or among products of the same company.<ref name=Cheng2014/> A 2015 report commissioned by [[Public Health England]] concluded that e-cigarettes "release negligible levels of nicotine into ambient air".<ref name=McNeill201565>{{cite web|last1=McNeill|first1=A, SC|title=E - cigarettes: an evidence update A report commissioned by Public Health England|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/454516/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England.pdf|website=www.gov.uk|publisher=Public Health England|page=65|accessdate=20 August 2015|location=UK|date=2015}}</ref>
+==Aerosol==
-E-cigarettes without nicotine are also available.<ref name=Bur2014>{{cite journal|last1=Burstyn|first1=I|title=Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks.|journal=BMC Public Health|date=9 January 2014|volume=14|pages=18|doi=10.1186/1471-2458-14-18|pmc=3937158|pmid=24406205}}</ref> The vapor may also contain tiny amounts of [[toxicant]]s, [[carcinogen]]s, and [[heavy metals]].<ref name=Hajek2014/><ref name=Grana2014>{{cite journal|last=Grana|first=R|author2=Benowitz, N |author3=Glantz, SA |title=E-cigarettes: a scientific review.|journal=Circulation|date=13 May 2014|volume=129|issue=19|pages=1972–86|doi=10.1161/circulationaha.114.007667|pmc=4018182|pmid=24821826}}</ref> Contamination with various chemicals has been identified.<ref name=Bertholon2013>{{cite journal|last1=Bertholon|first1=J.F.|last2=Becquemin|first2=M.H.|last3=Annesi-Maesano|first3=I.|last4=Dautzenberg|first4=B.|title=Electronic Cigarettes: A Short Review|journal=Respiration|year=2013|issn=1423-0356|volume=86|pages=433–8|doi=10.1159/000353253|pmid=24080743}}</ref> Some products contained trace amounts of the drugs [[tadalafil]] and [[rimonabant]].<ref name=Bertholon2013/> E-cigarette makers do not fully disclose information on the chemicals that can be released or synthesized during use.<ref name=Cheng2014/>
+The primary parts that make up an e-cigarette are a mouthpiece, a cartridge (tank), a heating element/atomizer, a microprocessor, a battery, and possibly a LED light on the end.<ref name="USFA2014">{{cite web |title=Electronic Cigarette Fires and Explosions |publisher=U.S. Fire Administration |year=2014|pages=1–11|url=https://www.usfa.fema.gov/downloads/pdf/publications/electronic_cigarettes.pdf}}</ref> An atomizer comprises a small heating element that vaporizes e-liquid and [[wicking]] material that draws liquid onto the coil.<ref name="SpinfuelGlossaryP1">{{cite news |url=http://spinfuel.com/vapers-glossary/|title=Vaper Talk – The Vaper's Glossary|publisher=Spinfuel eMagazine|date=5 July 2013|accessdate=18 November 2014}}</ref> When the user pushes a button.<ref name="Orellana-Barrios2015">{{cite journal |last1 = Orellana-Barrios |first1 = Menfil A. |last2 = Payne |first2 = Drew |last3 = Mulkey |first3 = Zachary |last4 = Nugent |first4 = Kenneth |title = Electronic cigarettes-a narrative review for clinicians |journal = The American Journal of Medicine |year = 2015 |issn = 00029343 |doi = 10.1016/j.amjmed.2015.01.033 |pmid = 25731134}}</ref> or inhales a [[pressure sensor]] activates the [[heating element]] that atomizes the [[solution#Liquid solutions|liquid solution]];<ref name=Rahman2014>{{cite journal |authors=Rahman MA, Hann N, Wilson A, Worrall-Carter L |title=Electronic cigarettes: patterns of use, health effects, use in smoking cessation and regulatory issues |journal=Tob Induc Dis |volume=12 |issue=1 |pages=21 |year=2014 |doi=10.1186/1617-9625-12-21 |pmc=4350653 |pmid=25745382}}</ref> The e-liquid reaches a temperature of roughly 100-250&nbsp;°C within a chamber to create an [[aerosolized]] vapor.<ref name="Rowell2015" /> The user inhales the [[aerosol]], commonly called [[vapor]], rather than [[cigarette smoke]].<ref name="Cheng2014" /> The aerosol provides a flavor and feel similar to [[tobacco smoking]].ref name=Caponnetto2012>{{cite journal |last1=Caponnetto |first1=Pasquale |last2=Campagna |first2=Davide |last3=Papale |first3=Gabriella |last4=Russo |first4=Cristina |last5=Polosa |first5=Riccardo |title=The emerging phenomenon of electronic cigarettes |journal=Expert Review of Respiratory Medicine |volume=6 |issue=1 |year=2012 |pages=63–74 |issn=1747-6348 |doi=10.1586/ers.11.92 |pmid=22283580}}</ref> However, variable voltage devices can raise the temperature where the user adjusts the vapor.<ref name="Bertholon2013" /> The vapor contains similar chemicals to the e-liquid which vary in composition and concentration across and within manufacturers.<ref name="Cheng2014">{{cite journal|last1 = Cheng|first1 = T.|title = Chemical evaluation of electronic cigarettes|journal = Tobacco Control|volume = 23|issue = Supplement 2|year = 2014|pages = ii11–ii17|issn = 0964-4563|doi = 10.1136/tobaccocontrol-2013-051482|pmc = 3995255|pmid = 24732157}}</ref><ref name="Bertholon2013" />
+=== First Hand ===
-A few metal parts in e-cigarettes contact the e-liquid and may contaminate it with metals.<ref name=FarsalinosPolosa2014>{{cite journal|last1=Farsalinos|first1=K. E.|last2=Polosa|first2=R.|title=Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review|journal=Therapeutic Advances in Drug Safety|volume=5|issue=2|year=2014|pages=67–86|issn=2042-0986|doi=10.1177/2042098614524430|pmc=4110871|pmid=25083263}}</ref> Tin, cadmium, nickel, lead,<ref name=Rom2014>{{cite journal|last1=Rom|first1=Oren|last2=Pecorelli|first2=Alessandra|last3=Valacchi|first3=Giuseppe|last4=Reznick|first4=Abraham Z.|title=Are E-cigarettes a safe and good alternative to cigarette smoking?|journal=Annals of the New York Academy of Sciences|volume=1340|issue=1|year=2014|pages=65–74|issn=00778923|doi=10.1111/nyas.12609|pmid=25557889}}</ref> aluminum,<ref name=Grana2014/> copper,<ref name=FarsalinosPolosa2014/> silver,<ref name=FarsalinosPolosa2014/> iron,<ref name=FarsalinosPolosa2014/> mercury,<ref>{{cite journal|last1=Dagaonkar RS|first1=R.S.|last2=Udwadi|first2=Z.F.|title=Water pipes and E-cigarettes: new faces of an ancient enemy|journal=Journal of the Association of Physicians of India|volume=62|issue=4|year=2014|pages=324–328|url=http://www.japi.org/april_2014/05_ra_water_pipes.pdf|pmid=25327035}}</ref> and chromium have been found in the vapor.<ref name=Cheng2014/> The tin may originate from the e-cigarette [[solder]] joints.<ref name=Grana2014/> The nickel and chromium [[nanoparticle]]s in the vapor may have came from the e-cigarette [[heating element]].<ref name=Grana2014/> The metals in the vapor have been found at concentrations far below levels permitted in inhaled medicines.<ref name=Hajek2014/> The metals have been found in trace amounts in the vapor, although some of them at higher amounts than in [[cigarette smoke]].<ref name=FarsalinosPolosa2014/> Lead and cadmium have been found in the vapor at 2–3 times greater levels than with a [[nicotine inhaler]].<ref name=FarsalinosPolosa2014/> One study stated the levels of nickel have been found to be 100 times higher than in cigarette smoke.<ref name=Orellana-Barrios2015>{{cite journal|last1=Orellana-Barrios|first1=Menfil A.|last2=Payne|first2=Drew|last3=Mulkey|first3=Zachary|last4=Nugent|first4=Kenneth|title=Electronic cigarettes-a narrative review for clinicians|journal=The American Journal of Medicine|year=2015|issn=00029343|doi=10.1016/j.amjmed.2015.01.033|pmid=25731134}}</ref> The amounts and kinds of metals or other materials found in the vapor is based on the material and other manufacturing designs of the heating element.<ref name=Bhatnagar2014/> Materials in e-cigarettes might include ceramics, plastics, rubber, filament fibers, and foams.<ref name=Bhatnagar2014/> Some of these materials could be found in the vapor.<ref name=Bhatnagar2014>{{cite journal|last1=Bhatnagar|first1=A.|last2=Whitsel|first2=L. P.|last3=Ribisl|first3=K.  M.|last4=Bullen|first4=C.|last5=Chaloupka|first5=F.|last6=Piano|first6=M. R.|last7=Robertson|first7=R. M.|last8=McAuley|first8=T.|last9=Goff|first9=D.|last10=Benowitz|first10=N.|title=Electronic Cigarettes: A Policy Statement From the American Heart Association|journal=Circulation|date=24 August 2014|volume=130|issue=16|pages=1418–1436|url=http://circ.ahajournals.org/content/130/16/1418.full|doi=10.1161/CIR.0000000000000107|pmid=25156991}}</ref> Silicate particles have been found in the vapor.<ref name=FarsalinosPolosa2014/>
+E-cigarettes produce particles, in the form of an [[aerosol]].<ref name="Cheng2014" /><ref name="Offermann2014" />  In physics, a vapor is a substance in the gas phase whereas an aerosol is a suspension of tiny particles of liquid, solid or both within a gas.<ref name="Cheng2014">{{cite journal|last1=Cheng|first1=T.|title=Chemical evaluation of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii11–ii17|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051482|pmc=3995255|pmid=24732157}}</ref> The aerosol is made-up of liquid sub-micron particles of condensed vapor,<ref name="Offermann2014">{{cite journal|last1=Offermann|first1=Francis|title=The Hazards of E-Cigarettes|journal=ASHRAE Journal|date=June 2014|volume=56|issue=6|url=http://www.gocolumbiamo.com/Health/Documents/Offermann-Thehazardsofe-cigarettes.pdf}}</ref> which mostly consist of propylene glycol, glycerol, water, flavorings, nicotine, and other chemicals.<ref name="FarsalinosPolosa2014" /> This aerosol that is produces resembles cigarette smoke.<ref name="Cheng2014" /> After a puff, inhalation of the aerosol travels from the device into the mouth and lungs.<ref name="Cheng2014" />
-Once vaporized the ingredients in the e-liquid go through [[chemical reaction]]s that form new compounds not found in the initial liquid.<ref name=Cooke2015>{{cite journal|last1=Cooke|first1=Andrew|last2=Fergeson|first2=Jennifer|last3=Bulkhi|first3=Adeeb|last4=Casale|first4=Thomas B.|title=The Electronic Cigarette: The Good, the Bad, and the Ugly|journal=The Journal of Allergy and Clinical Immunology: In Practice|volume=3|issue=4|year=2015|pages=498–505|issn=22132198|doi=10.1016/j.jaip.2015.05.022|pmid=26164573}}</ref> Many chemicals including [[carbonyl compounds]] such as [[formaldehyde]], [[acetaldehyde]], [[acrolein]], and [[glyoxal]] can inadvertently be produced when the [[nichrome wire]] (heating element) that touches the e-liquid is heated and chemically reacts with the liquid.<ref name=Bekki2014>{{cite journal|last1=Bekki|first1=Kanae|last2=Uchiyama|first2=Shigehisa|last3=Ohta|first3=Kazushi|last4=Inaba|first4=Yohei|last5=Nakagome|first5=Hideki|last6=Kunugita|first6=Naoki|title=Carbonyl Compounds Generated from Electronic Cigarettes|journal=International Journal of Environmental Research and Public Health|volume=11|issue=11|year=2014|pages=11192–11200|issn=1660-4601|doi=10.3390/ijerph111111192|pmid=25353061}}</ref> The propylene glycol-containing liquids produced the most amounts of carbonyls in e-cigarette aerosols.<ref name=Bekki2014/> Propylene glycol could produce [[propylene oxide]] when heated and aerosolized.<ref name=Grana2014/><ref name=Bhatnagar2014/> Glycerin may generate acrolein when heated at hotter temperatures.<ref name=Hajek2014/> Some e-cigarette products had acrolein identified in the vapor, at greatly reduced amounts than in cigarette smoke.<ref name=Hajek2014/> Many e-cigarettes companies are using water and glycerin instead of propylene glycol for vapor production.<ref name=Kacker2014>{{cite journal|last1=Oh|first1=Anne Y.|last2=Kacker|first2=Ashutosh|title=Do electronic cigarettes impart a lower potential disease burden than conventional tobacco cigarettes?: Review on e-cigarette vapor versus tobacco smoke|journal=The Laryngoscope|date=December 2014|volume=124|issue=12|pages=2702–2706|doi=10.1002/lary.24750|pmid=25302452}}</ref> Glyoxal and methylglyoxal have been found in the vapor.<ref name=Bekki2014/> The amount of carbonyls vary greatly among different companies and within various samples of the same e-cigarettes.<ref name=Bekki2014/>
+The particle size distribution and sum of particles emitted by e-cigarettes are like traditional cigarettes, with the majority of particles in the ultrafine range (modes, ≈100–200).<ref name="Grana2014" /> A 2014 review found that 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.<ref name=Grana2014/> They found that because these things are uncertain, it is not clear whether the ultrafine particles in e-cigarette vapor have health effects similar to those produced by traditional cigarettes.<ref name="Grana2014" /> A 2014 WHO report found e-cigarettes release a lower level of particles than traditional cigarettes.<ref name=WHOPosition2014>{{cite web |last1=WHO |title=Electronic nicotine delivery systems |url=http://apps.who.int/gb/fctc/PDF/cop6/FCTC_COP6_10-en.pdf |pages=1–13 |accessdate=28 August 2014}}</ref> Comparable to a traditional cigarette, e-cigarette particles are tiny enough to enter the alveoli, enabling nicotine absorption.<ref name="EbbertAgunwamba2015" /> The [[ultrafine particle|particles are of the ultrafine size]] which can go deep in the lungs and then into the [[systemic circulation]].<ref name="Grana2014" /> These [[nanoparticle]]s can deposit in the [[pulmonary alveoli|lung's alveolar sacs]], potentially leading to local respiratory toxicity.<ref name="Grana2014" /> E-cigarettes companies assert that the particulates produced by an e-cigarette are too tiny to be deposited in the [[alveoli]].<ref name="Dagaonkar2014">{{cite journal|last1=Dagaonkar RS|first1=R.S.|last2=Udwadi|first2=Z.F.|title=Water pipes and E-cigarettes: new faces of an ancient enemy|journal=Journal of the Association of Physicians of India|volume=62|issue=4|year=2014|pages=324–328|url=http://www.japi.org/april_2014/05_ra_water_pipes.pdf|pmid=25327035}}</ref>  Exactly what [[electronic cigarette aerosol|comprises the vapor]] varies in composition and concentration across and within manufacturers.<ref name="Cheng2014" /> Different devices generate different particle sizes and cause different depositions in the [[respiratory tract]], even from the same nicotine liquid.<ref name="Collaco2015">{{cite journal|last1=Collaco|first1=Joseph M.|title=Electronic Use and Exposure in the Pediatric Population|journal=JAMA Pediatrics|volume=169|issue=2|year=2015|pages=177–182|doi=10.1001/jamapediatrics.2014.2898|pmid=25546699}}</ref> Reports in the literature have shown respiratory and cardiovascular effects by these smaller size particles, suggesting a possible health concern.<ref name="AIHA2014" />
-[[Tobacco-specific nitrosamines]] (TSNAs) such as [[NNK]] and [[N-Nitrosonornicotine]] and tobacco-specific impurities have been found in the vapor at very low levels,<ref name=Rom2014/> comparable to amounts found in [[nicotine replacement products]].<ref name=FarsalinosPolosa2014/> N-Nitrosoanabasine and N-Nitrosoanatabine have been found in the vapor at reduced levels compared to cigarette smoke.<ref>{{cite journal |authors=Sanford Z, Goebel L |title=E-cigarettes: an up to date review and discussion of the controversy |journal=W V Med J |volume=110 |issue=4 |pages=10–5 |year=2014 |pmid=25322582}}</ref> Trace amounts of [[toluene]],<ref name=Rom2014/> [[xylene]],<ref name=FarsalinosPolosa2014/> [[polycyclic aromatic hydrocarbon]]s,<ref name=FarsalinosPolosa2014/> [[aldehyde]]s, [[volatile organic compound]]s (VOCs), [[phenols|phenolic compounds]], flavors, tobacco alkaloids, ''o''-Methyl benzaldehyde, and [[cresol]] have been found in the vapor.<ref name=Cheng2014>{{cite journal|last1=Cheng|first1=T.|title=Chemical evaluation of electronic cigarettes|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii11–ii17|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051482|pmc=3995255|pmid=24732157}}</ref> Low levels of isoprene, acetic acid, 2-butanodione, acetone, propanol, and diacetin, and traces of apple oil (3-methylbutyl-3-methylbutanoate) have been found in the vapor.<ref name=Grana2014/> [[Benzene]] and [[butadiene]] have been found in the vapor at many-fold lower than in cigarette smoke.<ref name=Bhatnagar2014/>
+=== Second Hand ===
-[[construction of electronic cigarettes|Later-generation e-cigarette devices]] can create greater amounts of carcinogens.<ref name=Orellana-Barrios2015>{{cite journal|last1=Orellana-Barrios|first1=Menfil A.|last2=Payne|first2=Drew|last3=Mulkey|first3=Zachary|last4=Nugent|first4=Kenneth|title=Electronic cigarettes-a narrative review for clinicians|journal=The American Journal of Medicine|year=2015|issn=00029343|doi=10.1016/j.amjmed.2015.01.033|pmid=25731134}}</ref> Depending on the heating temperature, the compounds may surpass the levels of cigarette smoke.<ref name=Cooke2015/> E-cigarettes devices using higher [[voltage]] [[battery (electricity)|batteries]] can produce carcinogens including formaldehyde at levels found in cigarette smoke.<ref name=Collaco2015>{{cite journal|last1=Collaco|first1=Joseph M.|title=Electronic Use and Exposure in the Pediatric Population|journal=JAMA Pediatrics|volume=169|issue=2|year=2015|pages=177–182|doi=10.1001/jamapediatrics.2014.2898|pmid=25546699}}</ref> The newer "tank-style" devices with higher voltages (''e.g.'' 5.0 volts<ref name=Cooke2015/>) could create formaldehyde at comparable or greater levels than in cigarette smoke.<ref name=Orellana-Barrios2015/> One study using a "puffing machine" showed that a third generation e-cigarette turned on to the maximum setting could create levels of formaldehyde between five and 15 times greater than in cigarette smoke.<ref name=McNeill201577/> Follow-up studies showed that this only occurred in overheated "dry-puffing", which according to the 2015 Public Health England report "poses no danger to either experienced or novice vapers, because dry puffs are aversive and are avoided rather than inhaled", and "At normal settings, there was no or negligible formaldehyde release."<ref name=McNeill201577/> They concluded that "There is no indication that EC users are exposed to dangerous levels of aldehydes."<ref name=McNeill201577>{{cite web|last1=McNeill|first1=A, SC|title=E - cigarettes: an evidence update A report commissioned by Public Health England|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/454516/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England.pdf|website=www.gov.uk|publisher=Public Health England|pages=77-78|location=UK|date=2015}}</ref> High-voltage e-cigarettes are capable of producing large amounts of carbonyls.<ref name=Bekki2014/> Reduced voltage e-cigarettes had e-cigarette aerosol levels of formaldehyde and acetaldehyde roughly 13 and 807-fold less than indicated in cigarette smoke.<ref name=Bekki2014/>
+After the aerosol is inhaled, it is exhaled.<ref name="Cheng2014" /> Emissions from electronic cigarettes are not comparable to environmental pollution or cigarette smoke as their nature and chemical composition are completely different<ref name=FarsalinosPolosa2014/> The particles are larger, with the mean size being 600&nbsp;nm in inhaled aerosol and 300&nbsp;nm in exhaled vapor.<ref name=Bertholon2013/>  The exhaled aerosol particle concentration is 5 times lower from an e-cigarette than from a traditional cigarette.<ref name="Drummond2014">{{cite journal|last1 = Drummond|first1 = MB|last2 = Upson|first2 = D|title = Electronic cigarettes. Potential harms and benefits.|journal = Annals of the American Thoracic Society|date = February 2014|volume = 11|issue = 2|pages = 236–42|pmid = 24575993|doi = 10.1513/annalsats.201311-391fr}}</ref>  The density of particles in the vapor is lower than in cigarette smoke by a factor of between 6 and 880 times lower.<ref name=FarsalinosPolosa2014/>
-== Comparison of levels of toxicants in e-cigarette aerosol ==
+For [[particulate matter]] emissions, e-cigarettes slightly exceeded the WHO guidelines, but emissions were 15 times less than traditional cigarette use.<ref name="Biyani2015">{{cite journal|last1=Biyani|first1=S|last2=Derkay|first2=CS|title=E-cigarettes: Considerations for the otolaryngologist.|journal=International journal of pediatric otorhinolaryngology|date=28 April 2015|doi=10.1016/j.ijporl.2015.04.032|pmid=25998217}}</ref> In January 2014, the [[International Union Against Tuberculosis and Lung Disease]] stated "Adverse health effects for exposed third parties (second-hand exposure) cannot be excluded because the use of electronic cigarettes leads to emission of fine and ultrafine inhalable liquid particles, nicotine and cancer-causing substances into indoor air."<ref>{{cite journal|last1=Bam|first1=T. S.|last2=Bellew|first2=W.|last3=Berezhnova|first3=I.|last4=Jackson-Morris|first4=A.|last5=Jones|first5=A.|last6=Latif|first6=E.|last7=Molinari|first7=M. A.|last8=Quan|first8=G.|last9=Singh|first9=R. J.|last10=Wisotzky|first10=M.|title=Position statement on electronic cigarettes or electronic nicotine delivery systems [Official statement]|journal=The International Journal of Tuberculosis and Lung Disease|date=1 January 2014|volume=18|issue=1|pages=5–7|doi=10.5588/ijtld.13.0815|pmid=24365545}}</ref> The dense vapor consists of liquid sub-micron [[Drop (liquid)|droplets]].<ref name="Offermann2014" />{{dl|date=December 2015}}
-{|class="wikitable" style="margin-left:0.4em;"
-|+Amounts of toxicants in e-cigarette aerosol compared with nicotine inhaler and cigarette smoke<ref name=Cooke2015/>
-!Toxicant
-!Range of content in nicotine inhaler mist (15 puffs∗)
-!Content in aerosol from 12 e-cigarettes (15 puffs∗)
-!Content in traditional cigarette micrograms (μg) in smoke from one cigarette
-|-
-|Formaldehyde (μg)
-|0.2
-|0.2-5.61
-|1.6-52
-|-
-|Acetaldehyde (μg)
-|0.11
-|0.11-1.36
-|52-140
-|-
-|Acrolein (μg)
-|ND
-|0.07-4.19
-|2.4-62
-|-
-|''o''-Methylbenzaldehyde (μg)
-|0.07
-|0.13-0.71
-|—
-|-
-|Toluene (μg)
-|ND
-|ND-0.63
-|8.3-70
-|-
-|p- and m-Xylene (μg)
-|ND
-|ND-0.2
-|—
-|-
-|NNN (ng)
-|ND
-|ND-0.00043
-|0.0005-0.19
-|-
-|Cadmium (ng)
-|0.003
-|ND-0.022
-|—
-|-
-|Nickel (ng)
-|0.019
-|0.011-0.029
-|—
-|-
-|Lead (ng)
-|0.004
-|0.003-0.057
-|—
-|-
-|}
+==== Exposure ====
-''μg'', microgram; ''ng'', nanogram; ND, not detected<ref name=Cooke2015/>
+<!-- {{main|Passive vaping}} -->
-<br>
+Since e-cigarettes have not been widely used long enough for evaluation, the long-term health effects from the second-hand vapor are not known.<ref name="Grana2014" /> There is insufficient data to determine the impact on [[public health]] from e-cigarettes.<ref name="Callahan2014">{{cite journal|last1=Callahan-Lyon|first1=P.|title=Electronic cigarettes: human health effects|journal=Tobacco Control|volume=23|issue=Supplement 2|year=2014|pages=ii36–ii40|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051470|pmid=24732161}}</ref> The potential harm to bystanders from e-cigarettes is unknown.<ref>{{cite web | url=http://www.lung.org/stop-smoking/tobacco-control-advocacy/federal/e-cigarettes.html | title=American Lung Association Statement on E-Cigarettes | publisher=American Lung Association | date=25 August 2014}}</ref> This is because no long-term data is available.<ref name="Hajek2014" />
-∗Fifteen puffs were chosen to estimate the nicotine delivery of one traditional cigarette.<ref name=Cooke2015/>
+Since e-cigarettes do not burn (or contain) tobacco, no [[side-stream smoke]] or any cigarette smoke is produced.<ref name="Grana2014" /> Only what is exhaled by e-cigarettes users enters the surrounding air.<ref name="Hajek2014" />  Exhaled vapor consists of nicotine and some other particles, primarily consisting of flavors, aroma transporters, glycerin and propylene glycol.<ref name="Hajek2014" /> Bystanders are exposed to these particles from exhaled e-cigarette vapor.<ref name="Grana2014" /> A mixture of harmful substances, particularly nicotine, ultrafine particles, and volatile organic compounds can be exhaled into the air.<ref name="Cervellin2013" />  The liquid particles condenses into a viewable fog.<ref name="Bertholon2013" /> The vapor 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.<ref name="Bertholon2013" /> This is because of fast revaporization at room temperature.<ref name="Bertholon2013" />
+There is a concern that some of the mainstream vapor exhaled by e-cigarette users can be inhaled by bystanders, particularly indoors, and have significant adverse effects.<ref name="Rom2014" /><ref name="KleinstreuerFeng2013">{{cite journal|last1=Kleinstreuer|first1=Clement|last2=Feng|first2=Yu|title=Lung Deposition Analyses of Inhaled Toxic Aerosols in Conventional and Less Harmful Cigarette Smoke: A Review|journal=International Journal of Environmental Research and Public Health|volume=10|issue=9|year=2013|pages=4454–4485|issn=1660-4601|doi=10.3390/ijerph10094454|pmid=24065038}}</ref>  Since e-cigarettes involve an aerosolization process, it is suggested that no meaningful amounts of carbon monoxide are emitted.<ref name="Nowak2014" /> Thus, cardiocirculatory effects caused by carbon monoxide are not likely.<ref name="Nowak2014" /> However, in an experimental study, e-cigarettes increased levels of carcinogenic polycyclic aromatic hydrocarbons in the surrounding air.<ref name="Nowak2014">{{cite journal |authors=Nowak D, Jörres RA, Rüther T |title=E-cigarettes--prevention, pulmonary health, and addiction |journal=Dtsch Arztebl Int |volume=111 |issue=20 |pages=349–55 |year=2014 |doi=10.3238/arztebl.2014.0349 |url=http://www.aerzteblatt.de/int/archive/article?id=159697 |pmc=4047602 |pmid=24882626}}</ref>
+E-cigarettes used in indoor environments can put at risk nonsmokers to elevated levels of nicotine and aerosol emissions.<ref name="Drummond2014" /> 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.<ref name=Grana2014/> 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.<ref name="Grana2014" /> In 2015 a report commissioned by Public Health England concluded that e-cigarettes "release negligible levels of nicotine into ambient air with no identified health risks to bystanders".<ref name="McNeill201565">{{cite web|last1=McNeill|first1=A, SC|title=E - cigarettes: an evidence update A report commissioned by Public Health England|url=https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/454516/Ecigarettes_an_evidence_update_A_report_commissioned_by_Public_Health_England.pdf|website=www.gov.uk|publisher=Public Health England|p=65|accessdate=20 August 2015|location=UK|date=2015}}</ref>
+A 2014 review of limited data concluded this vapor can cause [[indoor air pollution]] and is not just water vapor as is frequently stated in the advertising of e-cigarettes.<ref name="Grana2014" /> A 2014 practice guideline by [[NPS MedicineWise]] states, "Although data on health effects of passive vapour are currently lacking, the risks are argued to be small, but claims that e-cigarettes emit only water vapour are nevertheless incorrect. Serum cotinine levels (a metabolite of nicotine) have been found to be similar in bystanders exposed to either e-cigarette vapour or cigarette smoke."<ref>{{cite web|title=e-Cigarettes: a safe way to quit?|url=http://www.nps.org.au/publications/health-professional/health-news-evidence/2014/e-cigarettes|publisher=NPS MedicineWise}}</ref> The 2015 [[California Department of Public Health]] has reported that "Mainstream and secondhand e-cigarette aerosol has been found to contain at least ten chemicals that are on [[California Proposition 65 (1986)|California’s Proposition 65]] list of chemicals known to cause cancer, birth defects, or other reproductive harm."<ref name="Chapman2015">{{cite web | url=http://cdph.ca.gov/programs/tobacco/Documents/Media/State%20Health-e-cig%20report.pdf | title=State Health Officer’s Report on E-Cigarettes: A Community Health Threat | publisher=California Department of Public Health, California Tobacco Control Program | date=January 2015}}</ref> However, it has been demonstrated that e-cigarettes causes nonusers to be exposed to nicotine but not to tobacco-related combustion toxicants.<ref name="Rom2014" />
+[[File:No Vaping Sign (18562436519).jpg|right|thumb|A no smoking or vaping sign from the US.]]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.<ref name="AIHA2014" /> They urged indoors restrictions similar to smoking bans, until research has shown the aerosol has no risk of harm.<ref name="AIHA2014">{{cite web|title=White Paper: Electronic Cigarettes in the Indoor Environment|url=http://tobacco.ucsf.edu/sites/tobacco.ucsf.edu/files/u9/AIHA-Electronc%20Cig%20Document_Final.pdf|publisher=American Industrial Hygiene Association|date=October 19, 2014}}</ref> A 2014 review indicated that the levels of inhaled contaminants from the e-cigarette vapor are not of significant health concern for human exposures by the standards used in workplaces to ensure safety.<ref name="Bur2014">{{cite journal|last1=Burstyn|first1=I|title=Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks.|journal=BMC Public Health|date=9 January 2014|volume=14|pages=18|pmid=24406205|doi=10.1186/1471-2458-14-18|pmc=3937158}}</ref> The use of e-cigarettes in a smoke-free area could expose non-users to toxins.<ref>{{cite journal |authors=Grana RA, Ling PM |title="Smoking revolution": a content analysis of electronic cigarette retail websites |journal=Am J Prev Med |volume=46 |issue=4 |pages=395–403 |year=2014 |doi=10.1016/j.amepre.2013.12.010 |pmid=24650842}}</ref> The effect on bystanders would likely be much less harmful than traditional cigarettes.<ref name="Hajek2014" />
+WHO report stated passive exposure was as a concern, indicating that current evidence is insufficient to determine whether the levels of exhaled vapor are safe to involuntarily exposed bystanders.<ref name="WHOPosition2014" /> The report stated that "it is unknown if the increased exposure to toxicants and particles in exhaled aerosol will lead to an increased risk of disease and death among bystanders."<ref name="WHOPosition2014" /> The [[British Medical Association]] (BMA) reported in 2013 that there are "concerns that the use of e-cigarettes could threaten the norm of not smoking in public places and workplaces."<ref>{{cite web | url=http://bma.org.uk/news-views-analysis/news/2013/january/ecigarettes-not-proven-quitting-aid-says-bma | title=E-cigarettes not proven quitting aid, says BMA | work=British Medical Association | date=30 January 2013}}</ref>
+{{Asof|2013}}, the only clinical study currently published evaluating the respiratory effects of passive vaping found no adverse effects were detected.<ref name=FarsalinosPolosa2014/> A 2014 review found it is safe to infer that their effects on bystanders are minimal in comparison to traditional cigarettes.<ref name=FarsalinosPolosa2014/> A E-cigarette vapor has notably fewer toxicants than cigarette smoke and is likely to pose less harm to users or bystanders.<ref name=Grana2014/>
+=== Third hand ===
+E-cigarette use by a parent might lead to inadvertent health risks to offspring.<ref name="England2015" /> E-cigarettes pose many safety concerns to children.<ref name=England2015/> For example, indoor surfaces can accumulate nicotine where e-cigarettes were used, which may be inhaled by children, particularly youngsters, long after they were used.<ref name=England2015/> A policy statement by the American Association for Cancer Research and the American Society of Clinical Oncology has reported that "Third-hand exposure occurs when nicotine and other chemicals from second-hand aerosol deposit on surfaces, exposing people through touch, ingestion, and inhalation".<ref name=Brandon2015/> Public health England, looking at the available research said the amount of nicotine deposited was low and that an infant would have to lick 30 square meters to be exposed to 1mg of nicotine.<ref name="McNeill201565" /> The statement noted there are no published studies of third hand exposure from e-cigarettes, however initial data suggests that nicotine from e-cigarettes may stick to surfaces and would be hard to remove.<ref name=Brandon2015/> I
+==Eliquid==
+=== Contents ===
+The e-liquid is sold in bottles or pre-filled disposable cartridges, or as a kit for consumers to make their own e-juices.<ref name="DiyLiquid2">{{cite web|url = http://www.ecigarettemag.com/e-liquid-mixing/|publisher = Ecigarette Mag|title = E-liquid Mixing Guide – a Guide to DIY Mixing|accessdate = 10 November 2014}}</ref>  Some vendors of e-liquids, offer options to change the amounts of flavorings or nicotine strengths, and build each bottle customized for the purchaser.<ref name="DiyLiquid">{{cite web|url=http://www.ecigarettemag.com/e-liquid-mixing/|publisher=Ecigarette Mag|title=E-liquid Mixing Guide – a Guide to DIY Mixing|accessdate=10 November 2014}}</ref> E-liquids are made with various tobacco, fruit, and other flavors,<ref name="Grana2014" /> as well as variable nicotine concentrations (including nicotine-free versions).<ref name="Caponnetto2013" /> The standard notation "mg/ml" is often used on labels to denote nicotine concentration, and is sometimes shortened to "mg".<ref name="Laugesen2007">{{cite web|url=http://www.healthnz.co.nz/Ruyan_ecigarette.htm |author=Murray Laugesen|title=The Ruyan e-cigarette; Technical Information Sheet|publisher=Health New Zealand|date=17 October 2007|accessdate=31 March 2008}}</ref> In surveys of regular e-cigarette users, the most popular e-liquids have a nicotine content of 18&nbsp;mg/ml, and the preferred flavors were largely tobacco, mint and fruit.<ref name="Hajek2014">{{cite journal|last1=Hajek|first1=P|last2=Etter|first2=JF|last3=Benowitz|first3=N|last4=Eissenberg|first4=T|last5=McRobbie|first5=H|title=Electronic cigarettes: review of use, content, safety, effects on smokers and potential for harm and benefit.|url=http://tobonline.com/Media/Default/Article/Addiction-%20Hajek%2014.pdf|journal=Addiction (Abingdon, England)|date=31 July 2014|volume=109|issue=11|pages=1801–10|doi=10.1111/add.12659|pmid=25078252}}</ref> A cartridge may contain 0 to 20&nbsp;mg of nicotine.<ref name="Cervellin2013" /> EU regulations cap the concentration of nicotine in e-liquid at a maximum of 20&nbsp;mg/mL.<ref name="EbbertAgunwamba2015" /> A refill bottle can contain up to 1 g of nicotine.<ref name="Cervellin2013">{{cite journal|last1=Cervellin|first1=Gianfranco|last2=Borghi|first2=Loris|last3=Mattiuzzi|first3=Camilla|last4=Meschi|first4=Tiziana|last5=Favaloro|first5=Emmanuel|last6=Lippi|first6=Giuseppe|title=E-Cigarettes and Cardiovascular Risk: Beyond Science and Mysticism|journal=Seminars in Thrombosis and Hemostasis|volume=40|issue=01|year=2013|pages=060–065|issn=0094-6176|doi=10.1055/s-0033-1363468|pmid=24343348}}</ref> Refill liquids are often sold in the size range from 15 to 30 mL.<ref name="Hildick-SmithPesko2015">{{cite journal|last1=Hildick-Smith|first1=Gordon J.|last2=Pesko|first2=Michael F.|last3=Shearer|first3=Lee|last4=Hughes|first4=Jenna M.|last5=Chang|first5=Jane|last6=Loughlin|first6=Gerald M.|last7=Ipp|first7=Lisa S.|title=A Practitioner's Guide to Electronic Cigarettes in the Adolescent Population|journal=Journal of Adolescent Health|year=2015|issn=1054139X|doi=10.1016/j.jadohealth.2015.07.020|pmid=26422289}}</ref> One cartridge may typically last as long as one pack of cigarettes.<ref name="Odum2012">{{cite journal|last1=Odum|first1=L. E.|last2=O'Dell|first2=K. A.|last3=Schepers|first3=J. S.|title=Electronic Cigarettes: Do They Have a Role in Smoking Cessation?|journal=Journal of Pharmacy Practice|volume=25|issue=6|year=2012|pages=611–614|issn=0897-1900|doi=10.1177/0897190012451909|pmid=22797832}}</ref> Some liquids without flavoring is also sold.<ref name="Cochrane2014">{{cite journal|last1=McRobbie|first1=Hayden|last2=Bullen|first2=Chris|last3=Hartmann-Boyce|first3=Jamie|last4=Hajek|first4=Peter|last5=McRobbie|first5=Hayden|title=Electronic cigarettes for smoking cessation and reduction|journal=The Cochrane Library|year=2014|volume=12|pages=CD010216|doi=10.1002/14651858.CD010216.pub2|pmid=25515689}}</ref> The flavorings may be natural or artificial.<ref name="Bertholon2013">{{cite journal|last1=Bertholon|first1=J.F.|last2=Becquemin|first2=M.H.|last3=Annesi-Maesano|first3=I.|last4=Dautzenberg|first4=B.|title=Electronic Cigarettes: A Short Review|journal=Respiration|year=2013|issn=1423-0356|volume=86|pages=433–8|doi=10.1159/000353253|pmid=24080743}}</ref> About 8,000 flavors exist as of 2014.<ref name="WHO2014">{{cite web|title=Backgrounder on WHO report on regulation of e-cigarettes and similar products|url=http://www.who.int/nmh/events/2014/backgrounder-e-cigarettes/en/|accessdate=2 June 2015|date=26 August 2014}}</ref> A user does not normally consume a whole cartridge in a single session.<ref name="Pepper2013">{{cite journal|last1=Pepper|first1=J. K.|last2=Brewer|first2=N. T.|title=Electronic nicotine delivery system (electronic cigarette) awareness, use, reactions and beliefs: a systematic review|journal=Tobacco Control|volume=23|issue=5|year=2013|pages=375–384|issn=0964-4563|doi=10.1136/tobaccocontrol-2013-051122|pmid=24259045}}</ref> Most e-liquids are produced by a few manufacturers in China, the US and Europe.<ref name="Hajek2014" /> An e-cigarette user will usually obtain 300 to 500 puffs per mL of liquid.<ref name="Hildick-SmithPesko2015" />
+=== Manufacturing ===
+E-liquids are manufactured by many producers, both in the US and across the world.<ref name=Blackwell2015/> First tier manufacturers use lab suits, gloves, hair covers, inside of certified clean rooms with air filtration similar to pharmaceutical-grade production areas.<ref name=Blackwell2015>{{Cite web|title=Avail Vapor offers glimpse into the 'art and science' of e-liquids|url=http://www.richmond.com/business/local/article_9f65201a-94c0-51b1-9663-f9fbb5c522af.html|author=John Reid Blackwell|website=Richmond Times-Dispatch|accessdate=2015-11-23}}</ref>
+==== Standards ====
+Standards for e-liquid manufacturing have been created by American E-liquid Manufacturing Standards Association (AEMSA), which is trade association dedicated to creating responsible and sustainable standards for the safe manufacturing of e-liquids used in vapor products.<ref>{{Cite web|title = About AEMSA|url = http://www.aemsa.org/welcome-to-the-aemsa/|website = AEMSA|accessdate = 2015-11-23}}</ref> AEMSA has published a comprehensive list standards and best known methods, which are openly available for use by any manufacturer of e-Liquids. The AEMSA standards cover nicotine, ingredients, sanitary manufacturing rooms, safety packaging, age restrictions, and labeling.<ref name=AEMSA2015>{{Cite book|title=E-Liquid Manufacturing Standards|url=http://www.aemsa.org/wp-content/uploads/2015/09/AEMSA-Standards-v2.3.pdf|publisher=AMERICAN E-LIQUID MANUFACTURING STANDARDS ASSOCIATION (AEMSA)|year=2015|location=US|pages=1-13}}</ref>
+=== Regulation ===
+There are no current governmental or US [[Food and Drug Administration]] (FDA) manufacturing standards for e-liquid.<ref name=FDA2015/> The FDA has sought to regulate e-liquid through use of the [[Tobacco Control Act]], passed into law in 2009.<ref name=FDA2015/> In April of 2014, the FDA issued it's "Deeming" proposals for public comment, which would cover e-liquids manufacturing. The Final Rule, (in final form) giving the FDA authority to regulate e-liquids is anticipated to be released in late 2015, or early 2016.<ref name=FDA2015>{{Cite web|title = Products, Guidance & Regulations - Deeming – Extending Authorities to Additional Tobacco Products|url = http://www.fda.gov/TobaccoProducts/Labeling/ucm388395.htm|website = www.fda.gov|accessdate = 2015-11-23|language = en|first = Center for Tobacco|last = Products}}</ref>
 == See also ==