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Are E-cigarettes a safe and good alternative to cigarette smoking?
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Abstract
Electronic cigarettes (E-cigarettes) are devices that can vaporize a nicotine solution combined with liquid flavors instead of burning tobacco leaves. Since their emergence in 2004, E-cigarettes have become widely available, and their use has increased exponentially worldwide. E-cigarettes are aggressively advertised as a smoking cessation aid; as healthier, cheaper, and more socially acceptable than conventional cigarettes. In recent years, these claims have been evaluated in numerous studies. This review explores the development of the current E-cigarette and its market, prevalence of awareness, and use. The review also explores the beneficial and adverse effects of E-cigarettes in various aspects in accordance with recent research. The discussed aspects include smoking cessation or reduction and the health risks, social impact, and environmental consequences of E-cigarettes.
© 2014 New York Academy of Sciences.
© 2014 New York Academy of Sciences.
Science and Electronic Cigarettes: Current Data, Future Needs
Electronic cigarettes (ECIGs), also referred to as electronic nicotine delivery systems (ENDS) or ‘e-cigarettes’, generally consist of a power source (usually a battery) and heating element (commonly referred to as an atomizer) that vaporizes a solution (e-liquid). The user inhales the resulting vapor. ECIGs have been increasing in popularity since they were introduced into the US market in 2007. Many questions remain about these products, and limited research has been conducted. This review will describe the available research on what ECIGs are, effects of use, survey data on awareness and use, and the utility of ECIGs to help smokers quit using tobacco cigarettes. This review will also describe arguments for and against ECIGs, and concludes with steps to move research on ECIGs forward.
© 2014 New York Academy of Sciences.
© 2014 New York Academy of Sciences.
ELECTRONIC CIGARETTE VAPOR
Toxicants
ECIGs do not cause combustion when operated normally, and therefore do not produce some of the toxicants (such as carbon monoxide and polycyclic aromatic hydrocarbons) produced by tobacco cigarettes (Goniewicz et al., 2013). In fact, some research suggests ECIG vapor is considerably less toxic than cigarette smoke. In one study, the cytotoxicity of ECIG vapor generated from a “510 T” ECIG was investigated by exposing rodent fibroblasts to it (Romanga et al., 2013). The vapor from only one of the 21 ECIG solutions examined had cytotoxic effects, and all fibroblasts exposed to ECIG vapor were significantly more viable than those exposed to cigarette smoke. Fibroblast cells are critical for tissue healing and constructing the structural framework of animal tissues, and research has shown that cigarette smoke decreases the efficacy of fibroblasts, which diminishes the repair of damaged lung tissue (Carnevali et al., 1998).
However, potentially hazardous substances found in cigarette smoke have also been detected in ECIG vapor, albeit in varying and lesser amounts (McAuley et al., 2012; Schripp et al., 2012; Goniewicz et al., 2013). In one study, vapors were generated from 12 different brands of e-cigarettes and analyzed for four groups of common cigarette smoke toxicants (carbonyls, volatile organic compounds, TSNAs, and metals). All four toxicant groups were detected in ECIG vapor, but the levels of the toxicants present ranged from nine to 450 times lower than conventional cigarette smoke, and in many instances the toxicant levels from ECIG vapor were comparable with trace levels generated by the nicotine inhaler (Goniewicz et al., 2013; Table 1). Overall, the extant data support the notion that ECIG vapor contains fewer tobacco toxicants than does tobacco cigarette smoke while, at the same time, containing more tobacco toxicants than air. The extent to which chronic, long-term exposure to ECIG toxicants does or does not cause dependence, disability, disease, and death is unknown.
Toxicant levels in conventional cigarettes (Counts et al., 2005) and 12 brands of ECIGS (Goniewicz et al., 2013).
Environmental Exposure
The visible vapor produced from ECIGs raises concerns about environmental exposure. One study examined air quality after producing vapor from various ECIGs and detected traces of volatile organic compounds (VOCs), flavoring substances (diacetin), propylene glycol, glycerol, and nicotine (Scripp et al., 2012). However, the toxicant levels detected in the air after ECIG use were significantly lower than the toxicant levels after conventional cigarette use, and the different ECIGs tested produced variable toxicant levels. Other research, funded by a pro-ECIG organization, concluded that there are toxicants in ECIG vapor that are emitted into the air, but at far lower levels than conventional cigarettes (McAuley et al., 2012). In addition, ECIGs emit significantly lower amounts of particulate matter relative to tobacco cigarettes, suggesting a lower risk of environmental vapor exposure (Pellegrino et al., 2012).
HUMAN LABORATORY STUDIES
Studies involving human participants allow for another level of understanding of ECIGs, in terms of physiological effects on the user, tobacco abstinence symptom suppression, smoking behavior (puff topography), cognitive effects, and abuse liability.
Physiological Effects
Pulmonary Function
The long term effects of ECIG use on lung function remain unclear, but some research with a few ECIG models suggests that ECIGs produce short-term adverse effects on pulmonary function similar to acute adverse effects observed from cigarette smoking. For example,Vardavas et al. (2012) found that after five minutes of using a Nobacco “black line” ECIG with 11 mg/ml nicotine solution, users exhibited decreases in exhaled nitric oxide (FENO) and increases in total respiratory resistance, total respiratory impedance, and peripheral airway resistance; all of these outcomes are common acute effects associated with cigarette smoking. Conversely,Flouris et al. (2013) concluded that the ECIGs used in their study did not impair lung function acutely after active or passive use (second-hand exposure). Another study similarly concluded that active ECIG use of one particular brand produced no acute lung deficiencies (Chorti et al., 2012). The variety of devices and e-liquids available make generalizations difficult. Different product combinations may induce greater or lesser acute and long-term effects.
Nicotine Delivery
Inhaled nicotine produces similar acute physiological effects on the user (increases heart rate and blood pressure), whether it is delivered from an ECIG (Vansickel et al., 2013) or a tobacco cigarette (Rhee et al., 2007). However, ECIGs do not always deliver nicotine to the user with the same efficacy. Research using inexperienced ECIG users has shown that some ECIGs do not deliver nicotine in measurable amounts (Vansickel et al., 2010). Alternatively, at least some brands of ECIGs can deliver nicotine to experienced users under certain conditions (Dawkins and Cocoran, 2013; Vansickel and Eissenberg, 2013; Farsalinos, Spyrou, Tsimopoulou, Stefapoulos, Romanga, & Voudris, 2014). In some cases, the amount of nicotine delivered to the experienced ECIG user can reach plasma concentrations that approximate those seen after cigarette use (Vansickel and Eissenberg, 2013; see Figure 2).
Plasma nicotine concentrations in ECIG users. Top panel shows the mean plasma nicotine concentration before and after thirteen experience ECIG users took 10 puffs (30 second interpuff interval) from their preferred device using a cartomizer loaded with ...
These discrepancies associated with ECIG nicotine delivery could be explained by the apparent learning curve associated with ECIG users’ puff topography. Puff topography commonly is used to assess nicotine self-administration in cigarette smokers, and involves measuring variables such as puff volume, duration, number, and interpuff interval (Puustinen et al., 1987; Breland et al., 2002; Blank et al., 2009). Specifically, the few studies that have addressed this topic suggest that experienced ECIG users take longer puffs (about 4 seconds) whereas ECIG-naïve cigarette smokers tend to take shorter puffs (about 2 seconds), similar to tobacco cigarette puff durations (Hua et al., 2011; Farsalinos et al., 2013). In addition, ECIGs require stronger vacuums (suction from the user) relative to conventional cigarettes (Trtchounian et al., 2010). ECIG use behavior may depend on a variety of factors, including nicotine product design features, in a manner akin to how smoking behavior can depend on cigarette design features (e.g., compensatory behaviors observed when smokers of cigarettes with unventilated filters switch to those that have ventilated filters; Benowitz, 2001). More research on this topic is needed to understand how user behavior and device operating characteristics interact to influence delivery of nicotine and other toxicants.
Experienced ECIG users also vary considerably in their ability to obtain nicotine from ECIGs (Dawkins and Corcoran, 2013; Vansickel and Eissenberg, 2013). Individual differences in nicotine yield may be due to nicotine being converted to vapor with differing consistencies and efficacies across brands and models (Westenberger, 2009; Goniewicz et al., 2012). Individual differences in nicotine plasma concentrations may also be due to differences in experienced users’ puff topography. Some experienced users may never learn to increase their puff durations and/or lower their puffing flow rates to obtain nicotine reliably, suggesting there may be some behavioral components that are relevant (see Figure 2).
Psychological Effects
Subjective Effects
ECIGs can reduce tobacco abstinence symptoms in cigarette smokers (e.g., Bullen et al., 2010; Vansickel et al., 2010; Dawkins et al., 2013), but the extent to which this abstinence symptoms suppression is explained by nicotine delivery and/or explained by the behavioral stimuli that accompany ECIG use remains unclear. For example, some ECIGs have been shown to decrease tobacco abstinence symptoms significantly without actually delivering nicotine to the user (Vansickel et al., 2010). Likewise, ECIGs with and without nicotine did not differ in their ability to reduce the desire to smoke in women, though in men nicotine-containing ECIGs were more effective at reducing the desire to smoke (Dawkins et al., 2012).
Commonly reported negative effects of ECIGs include throat and mouth irritation, and dry cough (Bullen et al., 2010; Caponetto et al., 2013; Chen, 2013; Polosa et al., 2013). Other less frequently reported side effects include nausea, dry mouth, headaches, and dizziness. Reports of more serious adverse effects commonly associated with tobacco cessation such as depression, insomnia, and anxiety thus far have been rare (Polosa et al., 2013). In one study, serious adverse events in ECIG users included hypotension, seizure, chest pain, rapid heartbeat, disorientation, and congestive heart failure but the extent to which these effects were attributable to ECIG use was unclear. Less severe adverse events included sore throat, abdominal pain, headache, blurry vision, cough, and nausea/vomiting (Chen, 2013).
Cognitive Effects
Deficits observed in cognition and concentration in smokers as a result of acute smoking cessation can be improved via nicotine administration (Heishman et al., 2010). To date, only two ECIG studies have used cognitive outcome measures. In the first study, “White Super” “cig-alikes” containing 18 mg/ml of nicotine improved working memory relative to placebo ECIGs of the same brand in nicotine-dependent abstinent smokers (Dawkins et al., 2012). In another study (Dawkins et al., 2013), abstinent cigarette smokers using 18 mg/ml “Tornado” ECIGs (which were not “cig-alikes”) showed significant improvement in prospective memory relative to those using placebo. However, nicotine ECIGs only improved time-based and not event-based prospective memory. More work is needed to understand the effects of ECIGs on the cognitive function of all those who may use them.
Abuse liability
The potential for ECIG abuse has been examined behaviorally in humans in one study that combined subjective effects assessment with a behavioral task known as the multiple choice procedure (Vansickel et al., 2012). In one study session, cigarette smokers sampled a “Vapor King” “cig-alike” containing 18 mg/ml of nicotine solution, and then chose between taking 10 puffs of an ECIG and varying amounts of money. In a second session, participants choose between 10 puffs of their own brand of cigarette and varying amounts of money. The abuse potential of the product (i.e. ECIGs or tobacco cigarettes) was assessed by observing the maximum value of money at which the product was chosen over money (i.e., the cross-over value). The average crossover value for ECIGs was $1.06 as opposed to $1.50 for own brand cigarettes, suggesting that for these smokers, their own brand of cigarettes was more reinforcing (and had more abuse potential) relative to the particular brand/strength of ECIG tested (Vansickel et al., 2012). This single study of the abuse liability of one ECIG brand is hardly sufficient to address the issue. A comprehensive approach to determining ECIG abuse liability would include a variety of assessment methods across many populations of interest with varying experience with nicotine delivering products and the full range of ECIG devices/liquids on the market. Thus, a program of research addressing this issue is needed now.
In addition, other methods for misusing ECIGs as nicotine delivery devices may arise, and learning about them will be critical for monitoring the likely individual and public health effects of ECIGs. In terms of using ECIGs to deliver drugs other than nicotine, there have been reports in the media regarding this phenomenon, there are sections of the internet devoted to the topic, and a recent press release suggests that at least on ECIG vendor is developing a product with this goal in mind (e.g., VaporBrands International, 2014). At this writing there are no empirical investigations of this behavior.
alcuni modelli
sigaretta elettronica tradizionale
heat not burn device
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