New Systematic Review Investigates the Potential For Harm and Benefit For E-Cigs

By Lindsay Fox Posted November 4, 2014

E-Cigs Harm and Benefit Potential

Regulators’ decisions need to be based on sound science rather than unsupported assertions and media-driven hysteria, but we increasingly see more weight given to the latter when it comes to e-cigs. The FDA’s regulations contain an atrocious assessment of the current state of research on e-cigarettes, yet when actual scientists and researchers do the same thing, the result is consistently positive. A new systematic review adds to this by summarizing the evidence into the usage, content, safety and potential for helping smokers quit, aiming to determine whether e-cigarettes are likely to do more benefit or harm and inform regulatory decision-making.


For those who follow the research on e-cigarettes, much of the content will be well-known to you (spoiler alert: e-cigarettes are very likely to be tons safer than combusted cigarettes and effective for reducing and quitting smoking), but regulators apparently incapable of objectively evaluating the state of scientific knowledge on the issue could learn a lot from a quarter of an hour spent reading through this paper. The review comes from Peter Hajek, Jean-François Etter, Neal Benowitz, Thomas Eissenberg and Hayden McRobbie, and has been published online ahead of appearing in the journal Addiction. The full text is available for free.




  • Surveys of vapers, non-smokers and teens provide evidence that e-cigarette use is growing among smokers, but use is very rare among non-smokers.
  • Among enthusiastic vapers (recruited from dedicated online forums but not representative of the general population), quit rates of between 42 and 99 percent have been reported in surveys.
  • Research into the chemical composition of e-liquid aerosol (commonly called vapor) shows that e-cigarettes are likely to pose a considerably lower risk (if any at all) than cigarettes to both direct users and bystanders.
  • PG is generally considered safe for inhalation due to results of animal testing, with only one study suggesting a decline in lung function for people regularly exposed to PG-containing smoke machines.
  • VG can lead to acrolein production, but vapers are exposed to 80 percent less of it than smokers.
  • The most common adverse effects reported during e-cigarette use are throat and mouth irritation, which is common across user surveys and clinical research. There are minor effects on airway resistance, but they aren’t considered clinically significant.
  • The evidence to date supports the notion that e-cigarettes help smokers quit, but they also contribute to big reductions in the number of cigarettes per day smoked, often in people who never intended to quit.
  • The researchers argue that regulators should base decisions on rational analyses and sound science rather than unsupported media-driven allegations.


Surveys of Vapers: Are E-Cigarettes Attracting Non-Smokers and Teens?


The first section of the review investigates the evidence from surveys of vapers and groups like non-smokers and children who may start vaping. As most people know, e-cigarette use is becoming more and more common, with use rising from 0.6 percent of the general US population in 2009 to 6.2 percent in 2011 and similar trends in the UK. According to survey data, around a third of ever-users had vaped within the past month, and around 12 to 14 percent of smokers who try e-cigarettes end up as daily users.


There is also data from surveys given to users of dedicated e-cigarette websites which provides evidence from enthusiastic vapers but needs to be interpreted with caution. For example, although the fact that between 42 and 99 percent of respondents in these surveys say e-cigarettes helped them to quit smoking is proof that e-cigarettes do work for some people, it’s unlikely that such high rates would be seen in the general population of smokers.


The biggest concern addressed in this section is the whole “gateway” argument: the idea that non-smokers (especially kids) will start vaping and then progress to smoking. Research conducted into this area suggests that between 0.1 and 3.8 percent (with a median value of 0.5 percent) of never-smokers had tried e-cigarettes at least once before and between 0 and 2.2 percent (with a median of 0.3 percent) had done so in the last 30 days. The authors also address the CDC survey, which made headlines despite finding that only 0.5 percent of middle school students and 0.7 percent of high school students were non-smokers who’d tried an e-cigarette. Further evidence shows that current use of e-cigarettes (only defined as use within the last 30 days) among non-smokers is reported by just 0.04 percent, and another study found that among children current use is only observed in those who’ve already tried smoking.


There is no gateway. And to put things into perspective, the authors point out that 39.5 percent of twelfth graders had tried cigarettes in 2011. Additionally, half of all children who try cigarettes progress to regular use.


E-Cigarette Chemistry and Content


The next section of the paper discusses the evidence into the chemical composition of e-cigarette aerosol (although we call it vapor, it technically isn’t), and repeats many of the things most vapers already know. Any impurities and toxic components which have been detected in e-cigarette aerosol have been present in much lower levels than in cigarette smoke or even approved medical treatments, and there is evidence that e-cigarette aerosol is not toxic to cells. Thanks to this evidence, as well as the fact that e-cigarettes don’t emit “sidestream” vapor (the smoke that rises from the tip of cigarettes and is the main factor in second-hand smoke production), the researchers argue that e-cigarettes are likely to pose a much lower risk, if any at all, to bystanders than cigarettes.


The researchers also bring up some more general evidence into the safety of propylene glycol (PG) and vegetable glycerin (VG), the two key ingredients in e-liquid and vapor. They point to extensive animal testing conducted on PG, showing it to be safe for inhalation by humans, but regular exposure of children suffering from asthma, rhinitis, eczema or allergies may exacerbate symptoms (or potentially induce the problem).


There is also a a piece of research indicating reduced lung function in people chronically exposed to theatrical fog containing PG, which is mentioned by the authors but left unexamined. This is curious, because although the core components are the same, it’s reasonable to expect some differences between theatrical fog and e-liquid. The study also looked at mineral-oil containing fog mixtures, and the reduced lung functioning was only observed for those working closest to the machine, so while this may indicate some long-term risk, it’s far from clear if it translates to vaping.


They also point out that while VG is non-toxic, it can produce acrolein at higher temperatures, a toxic chemical that’s been detected in e-cigarette chemistry studies. However, this is present in much smaller quantities than in cigarettes, and the researchers point to evidence that smokers reduce their acrolein intake by 80 percent if they switched to vaping VG-based liquids. If they just reduced their smoking through vaping VG-based liquids, their intake was reduced by 60 percent.


Finally, they address the concerns relating to inaccurate labeling and nicotine being present in reportedly nicotine-free liquids. There have been many reports of this occurring, but it’s been only in trace levels (that are unlikely to produce any effects) apart from in one instance where a manufacturer put the same nicotine level in all cartridges tested regardless of the labeled nicotine content. In the major e-liquid brands that have been tested, the nicotine content has been consistently accurate.


The Safety of E-Cigarettes


The section on the safety of e-cigarettes begins by considering the adverse events which have been reported by users. These are ordinarily things like mouth and throat irritation, and no serious adverse events have been reported in experimental or follow-up studies to date. These also appear to be the most common side effects as reported on user forums, accounting for around 50 percent of all reports in a dedicated subsection. This data also suggests that 2 percent of vapers experienced an increase in blood pressure.


The researchers offer evidence showing that short-term usage doesn’t negatively affect blood chemistry or cardiovascular function in users (smokers or ex-smokers), but the nicotine present does increase your heart-rate during your first vape of the day. In one study, minor effects on airway resistance and markers of lung inflammation were observed, but these weren’t considered clinically significant. Another study confirmed a significant negative effect on lung functioning following smoking a cigarette but no change after vaping.


The paper also addresses concerns about e-cigarette explosions and e-liquid poisonings, rightfully pointing out both are very uncommon yet are enthusiastically reported in the media. Reported poisonings, for example, are rare and ordinarily do no serious harm. The authors put forward one news report of an accidental fatal poisoning, but point out that there have also been intentional suicide attempts. Although one of these was successful, others involved adults drinking up to 1,500 mg of nicotine (even higher than the new revised estimate for nicotine toxicity), but still recovering after a few hours.


Do E-Cigarettes Help Smokers Quit?


The final area of research included in the review is the effect of e-cigarettes on smokers, looking at their effect on blood nicotine levels and smoking cessation. The biggest issue is vaping’s effectiveness for quitting smoking, and the authors present evidence that both nicotine and non-nicotine e-cigarettes can reduce smoking cravings. Research conducted into their effects when given to smokers with no intention of quitting or reducing smoking shows that around 28 percent of them will have reduced the amount they smoke by at least half, with around 13 percent having quit after two years. Similarly positive findings have also been found in smokers suffering from schizophrenia. For “dual users” (those who smoke and vape) across clinical trials and surveys, the evidence shows that they reduce their smoking significantly when they start to vape, and one study suggests that up to 46 percent quit entirely after a year.


Whether or not e-cigarettes help smokers quit is one of the main focuses of the research to date. Firstly, it mentions the fact that there are case reports suggesting that e-cigarettes are often effective for people who couldn’t quit smoking using other methods, and that while absolute quit rates are often fairly modest, much more e-cigarette users reduce their cigarette consumption than smokers trying to quit using other methods.


A clinical trial investigating whether e-cigarettes were more effective for quitting smoking than nicotine patches is used as evidence by the researchers, who point out that the device used is now known to deliver less nicotine than modern devices. The study found that a higher proportion of e-cigarette users than patch users (7.3 percent to 5.8 percent) had quit smoking after six months, but this difference didn’t reach statistical significance. Another trial used an inferior, often malfunctioning e-cig and found that 11 percent of those randomly assigned to nicotine cartridges had quit after a year compared to 4 percent of those using non-nicotine e-cigs.


Some detailed e-cig usage data available for England provides a final point for the researchers, because it shows a decrease in smoking as e-cigarettes became more popular, as well as an increase in quitting rates. It seems that most of the evidence (aside from purposefully misleading studies which are addressed in the review, much of it associated with Stanton Glantz) suggests e-cigarettes really do help people quit.


Ecigs Harmful Or Good


So What Does it Mean for Vapers and Regulators?


After presenting their evidence, the researchers address some common media-fed concerns about e-cigarettes followed by an appraisal of the claim based on current knowledge. In response to the claims that studies into the chemistry of e-cigs show a potential for significant risk, they argue that although long-term effects are still ultimately (and quite obviously) unknown, based on this evidence vaping is likely to be much less harmful than cigarettes for both users and bystanders, if it is even harmful at all.


Based on abundant evidence of a very limited appeal to non-smokers, whether adult or children, the researchers argue that there is no support for “gateway” claims. They point out that the emergence of e-cigarettes has been associated with a reduction in youth smoking, not an increase, and that no non-smoker has ever been found to go from vaping to smoking, in the rare cases they even try it. Finally, e-cigarette use seems to have negatively affected the sale of cigarettes, so fears of “renormalizing” smoking also appear unfounded.


The alternative is that e-cigarettes reduce harm for individuals and reduce smoking rates at the population-level, improving health overall. If this is true, which the evidence presented in the paper suggests it is, the ideal scenario is as many smokers switching to vaping as possible, with the technology hopefully replacing smoking altogether in the future. To date, the researchers argue that the evidence supports the notion e-cigarettes reduce smoking and thereby promote individual health, but not enough people use them to establish their impact at population-level.


The authors explain that regulations that serve to stifle the development of new products and make vaping more expensive will likely drive the industry into the hands of Big Tobacco, but some countries opt for even stricter rules based on hypothetical and seemingly unlikely risks. They comment that, “Regulatory decisions will provide the greatest public health benefit when they are proportional, based on evidence and incorporate a rational appraisal of likely risks and benefits.”


Conclusion – Good News for Vapers, Something to Ignore for the FDA


ecigs objective analysis

This is all great news for vapers, but regulators considering overly restrictive rules are the ones we really need to pay attention. The FDA’s proposal would effectively kill the industry with paperwork, but the most disturbing thing is the apparent ignorance displayed with regards to research into e-cigs. The review summarizes much of this evidence, but by its nature this is not new, in fact, it was obtained by the authors by spending time searching online libraries of academic journals with a couple of simple keywords. The FDA is undoubtedly well-aware of these things (and now has a mountain of comments on their proposal providing such evidence) but they still suggested their industry-crushing regulation anyway. In a sane world, findings like this stressing the huge potential for public health benefit from e-cigs and the utter implausibility of many of the touted “risks” would be enough to make the people tasked with protecting the health of the nation reconsider their actions. But we’re not living in a sane world.


  • janet

    will e cig help memory problems?

    • ITSa341

      nicotine has been tested as a treatment for ulzheimers and other cognitive and nerve damaging diseases and problems including parkinsons and others. The results I saw were promising but were very preliminary and not to be taken as proof of effectiveness as a treatment. I don’t know if this research is ongoing or not but would love to see any information. If you know of other studies or information please let me know. My mother suffers from parkinson’s disease so I am very interested.

  • Though it have some irritation, but it is quite good than the traditional cigarettes.

  • Guest

    I was a regular smoker and used to smoke around 10 cigarettes a day. It turned out to be hazardous very costly too, until I heard about the benefits of e-cigs and started vaping. Now, I feel better with e-cigarettes as they have reduced both my addiction levels as well as my expenses.

  • f.virtue

    I smoked for 40 years and I find i am vaping my estick a lot less than smoking . Sometimes I only take 5 puffs a day. I honestly have lost all cravings for tobacco.