Public Health Consequences of E-Cigarettes (2018) / Chapter Skim
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18 Harm Reduction
18 Harm Reduction
Pages 589-630
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From page 589... ...
By contrast to these earlier chapters, this chapter examines the potential harms of e-cigarettes relative to those of combustible tobacco cigarettes. In so doing, the committee applies a harm reduction approach.
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From page 590... ...
Nevertheless, if e-cigarettes confer lower health risks compared with combustible tobacco cigarettes, encouraging use of this reduced-risk product rather than encouraging complete abstinence only could have public health benefits. As suggested by the Cochrane review's conclusions, this approach might be especially salient for combustible tobacco cigarette smokers who are unable or unwilling to quit.
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From page 591... ...
to smoking only combustible tobacco cigarettes; it would be more worrisome if e-cigarettes increased likelihood of relapse. In assessing the harm reduction potential of e-cigarettes among users, the committee therefore considered effects in two populations: smokers who switched to e-cigarette use alone and smokers who use e-cigarettes concurrently with combustible tobacco cigarettes.
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From page 592... ...
These include evidence on the exposure to toxicants present in e-cigarette aerosols compared with those in cigarette smoke; nicotine and toxicant exposures in e-cigarette users as an intermediate outcome; and comparisons of effects on any health outcome from e-cigarette use compared with combustible tobacco cigarette smoking. Because multiple studies were available comparing e-cigarettes with combustible tobacco cigarettes for each step in the causal pathway, in this section, the committee discusses evidence by establishing likely exposures from the two products and moves down the causal chain to show how these exposures might shape health effects differently.
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From page 593... ...
For studies on the effects of switching from combustible tobacco cigarettes to e-cigarettes to reduce harm from passive exposures, RCTs, and longitudinal observational studies that follow household members of combustible tobacco cigarette smokers who switch to e-cigarettes completely would provide the strongest evidence. In their absence, the committee draws inferences from studies that examine exposure to toxicants from passive exposure to e-cigarette aerosols compared with combustible tobacco smoke.
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From page 594... ...
The committee also drew on analogous data from in vivo animal and in vitro studies comparing the toxicity of e-cigarettes and combustible tobacco cigarettes. The committee limited studies to those that used the same models and experiment settings to expose cells or animals to both e-cigarette aerosols and combustible tobacco cigarette smoke.
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Although some of these toxicants are also found in combustible tobacco cigarettes, they are generally at much lower levels in e-cigarettes. Carbon monoxide (CO)
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To that end, this section reviews studies that directly compared emissions of harmful and potentially harmful chemicals from e-cigarette devices and from combustible tobacco cigarettes. Reducing the quantity of tobacco a person uses and reducing the potentially toxic substances in tobacco products (such as in pharmaceutical nicotine and in potential reduced-exposure tobacco products)
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was 85 percent lower than the nicotine yield for the combustible tobacco cigarettes. The authors also found that the mainstream combustible tobacco cigarette smoke contained approximately 1,500 times more harmful and potentially harmful constituents (HPHCs)
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Potential harm reduction will be at least partially determined by the magnitude of reduction in exposure to harmful and potentially harmful toxicants as compared with exposure from tobacco smoking. Below, the committee reviews cross-sectional and longitudinal studies that compared exposure to nicotine and toxicants in tobacco smokers who substituted e-cigarettes for their combustible tobacco cigarettes.
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There were no significant differences in saliva cotinine levels among groups either during the laboratory sessions (during which the control group was smoking combustible tobacco cigarettes exclusively) or at follow-up.
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, evaluated the effects of switching from combustible tobacco cigarettes to e-cigarettes on nicotine delivery and exposure to selected carcinogens and toxicants. The authors measured metabolites of nicotine and major carcinogens and toxicants present in combustible tobacco smoke and combustible tobacco smoke exposure bio arkers m (including NNK, 1,3-butadiene, crotonaldehyde, acrolein, benzene, a crylamide, acrylonitrile, ethylene oxide, propylene oxide, naphthalene, fluorene, phenanthrene, and pyrene)
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Hecht and colleagues (2015) analyzed urine samples from 28 e-cigarette users who had not smoked combustible tobacco cigarettes for at least 2 months for toxicant and carcinogen metabolites, including 1-hydroxy pyrene (1-HOP)
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compared biomarkers of exposure to nicotine and potentially toxic and carcinogenic chemicals among exclusive combustible tobacco cigarette smokers, former smokers with longterm exclusive e-cigarette use, former smokers with long-term exclusive NRT use, long-term dual users of both combustible tobacco cigarettes and e-cigarettes, and long-term users of both combustible tobacco cigarettes and NRT (n = 36 or 37 per group; total n = 181)
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were significantly lower among exclusive e-cigarette and exclusive NRT users than for exclusive combustible tobacco cigarette smokers, dual combustible tobacco cigarette–e-cigarette users, and dual combustible tobacco cigarette–NRT users. The e-cigarette–only users had significantly lower NNAL levels than all other groups.
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From page 604... ...
For example, EGR1 was functionally associated with decreased expression of 18 target genes in e-cigarette users compared with only 5 target genes in combustible tobacco cigarette smokers. Synthesis Several cross-sectional and longitudinal studies compared exposure to nicotine and toxicants in smokers who substituted e-cigarettes for their combustible tobacco cigarettes.
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, who were randomized to three e-cigarette–only groups, three dual-use groups, and a control group (cessation from nicotine and tobacco for 8 weeks, followed by switching to the same type of e-cigarettes as the e-cigarette groups) , the authors also assessed benefits of and complaints about using e-cigarettes and smoking combustible tobacco cigarettes.
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Participants were classified as quitters (those who completely switched from combustible tobacco cigarettes to e-cigarettes) , reducers (those who substituted some of their smoking with e-cigarettes and reduced their combustible tobacco cigarette consumption)
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The authors also investigated the acute effects of e-cigarettes on blood pressure and heart rate compared with the effects of combustible tobacco cigarette smoking (Yan and D'Ruiz, 2015)
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The authors found that CBC indexes remained unchanged during the control session and the e-cigarette exposure sessions (p > 0.05) , whereas combustible tobacco cigarette smoke exposure increased white blood cell, lymphocyte, and granulocyte counts for at least 1 hour (p < 0.05)
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. Overall spirometry data, asthma control, and AHR improved significantly among both exclusive combustible tobacco cigarette smokers and dual users at baseline (Polosa et al., 2014a)
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No significant changes were observed in the control group. Figure 18-4 illustrates the changes in diastolic blood pressure among e-cigarette users and controls (combustible tobacco cigarette smokers)
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who smoked five or more combustible tobacco cigarettes per day for at least 2 years. The authors measured arterial stiffness (stiffness index and reflection index)
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among 20 established smokers who substituted e-cigarettes for smoking combustible tobacco cigarettes for 2 weeks. The authors found a statistically significant increase in gingival inflammation after 2 weeks of using e-cigarettes instead of their usual combustible tobacco cigarettes.
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ü Aug et al., 2015 Metabolome of HBECs ü Azzopardi et al., 2016 Cytotoxicity test with H292 human bronchial epithelial cells ü Banerjee et al., 2017 Transcriptomic perturbations in lung epithelial tissue (MucilAir) ü Barber et al., 2016 Inflammatory processes, viability, density, and metabolic activity of HUVECs ü Breheny et al., 2017 Carcinogenic potential with cell transformation assays in mouse fibroblast cells (Bhas 42)
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were exposed to combustible tobacco smoke extracts and e-cigarette aerosol extracts, and changes in platelet activation, adhesion, aggregation, and inflammation were evaluated ü Leigh et al., 2016 Cell viability, metabolic activity, and release of inflammatory mediators (cytokines) in H292 human bronchial epithelial cells ü
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ü Rubenstein et al., 2015 Kupffer cell complement receptor expression, oxidative stress production, cytokine release and viability, and density ü Scheffler et al., 2015 Cell viability and histology of immortalized normal human bronchial epithelial cell (NHBE48) ü Shen et al., 2016 Transcriptomes of differentiated human bronchial epithelial cells ü Taylor et al., 2016 Oxidative stress, apoptotic and necrotic responses in human bronchial epithelial cells ü Teasdale et al., 2016 Stress response in human coronary artery endothelial cells ü Thorne et al., 2016 Mutagenicity test with Salmonella typhimurium strains TA98 and TA100 ü Thorne et al., 2017 Induction of double-strand DNA damage in vitro using human lung epithelial cells (BEAS-2Bs)
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TABLE 18-3 Comparison of Animal Studies That Compared Toxicity of E-Cigarettes and Combustible 616 Tobacco Cigarettes Harmful Effects of E-Cigarettes Versus Combustible Tobacco Cigarettes Favors Combustible Favors Tobacco E-Cigarettes as Similar Cigarettes as Reference Study Measures and Outcomes Less Harmful Harm Less Harmful Larcombe et al., 2017 Pulmonary inflammation, lung volume, lung ü mechanics, and responsiveness to methacholine were measured in female BALB/c mice exposed for 8 weeks to tobacco smoke or one of four types of e-cigarette aerosol Palpant et al., 2015 Developmental effects in vivo with zebrafish (Danio ü rerio) and cardiac differentiation of human embryonic stem cells Parker et al., 2017 Developmental toxicities using the FETAX ü Ponzoni et al., 2015 Body weight, food intake, and the signs of ü mecamylamine-precipitated and spontaneous withdrawal episodic memory and emotional responses in male BALB/c mice Rau et al., 2017 Skin flap survival (microcirculation and perfusion)
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Although in vitro and animal studies that compared acute effects of exposure to e-cigarette aerosols with effects caused by combustible tobacco smoke provided mixed results, the majority of studies favored e-cigarettes as less harmful products than combustible tobacco cigarettes. Moreover, although some studies found similar harm from e-cigarettes, no studies found that e-cigarettes were more harmful than combustible tobacco cigarettes among combustible tobacco cigarette smokers who switched to exclusive e-cigarette use.
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Most dual users at baseline abandoned e-cigarettes and continued to smoke tobacco. At 12 months, 21.9 percent of dual users quit combustible tobacco smoking while 20.5 percent of those who only smoked combustible tobacco cigarettes quit smoking.
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. Harm Reduction from Passive Exposure to E-Cigarette Aerosol Compared with Combustible Tobacco Cigarette Smoke Among Non-Users As described in the committee's discussion of secondhand exposures to e-cigarette aerosol compared with ambient air (see Chapter 3)
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conducted an observational study to characterize passive exposure to nicotine from e-cigarettes and combustible tobacco cigarettes among non-smokers (n = 54) from home settings with different tobacco use conditions.
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Results showed that e-cigarettes are a source of secondhand exposure to nicotine, but not CO, and VOCs. The average concentration of airborne nicotine over 1 hour from smoking combustible tobacco cigarettes was 10 times higher than from e-cigarettes (31.60 ± 6.91 versus 3.32 ± 2.49 µg/m3, respectively; p = 0.0081; see Figure 18-6)
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From page 622... ...
The committee did not identify any long-term studies comparing health effects resulting from passive exposure to secondhand aerosol from e-cigarettes with effects in non-smokers passively exposed to tobacco smoke. In general, the studies reviewed show that using an e-cigarette in indoor environments may involuntarily expose non-users to nicotine and particulates, but at lower levels compared with exposure to secondhand tobacco smoke from combustible tobacco cigarettes.
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There is moderate evidence that secondhand expo sure to nicotine and particulates is lower from e-cigarettes compared with combustible tobacco cigarettes. REFERENCES Adriaens, K., D
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2013. Comparison of the cytotoxic potential of cigarette smoke and electronic cigarette vapour extract on cultured myocardial cells.
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2017. Exposure to nicotine and selected toxicants in cigarette smokers who switched to electronic cigarettes: A longitudinal within-subjects observational study.
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2014. Comparative in vitro toxicity profile of electronic and tobacco cigarettes, smokeless tobacco and nicotine replacement therapy products: E-liquids, extracts and collected aerosols.
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2017. Electronic cigarettes are as toxic to skin flap survival as tobacco cigarettes.
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2013. Carboxyhaemoglobin levels, health and lifestyle perceptions in smokers converting from tobacco cigarettes to electronic cigarettes.
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2009. The strategic dialogue on tobacco harm reduction: A vision and blueprint for action in the US.
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