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Electronic cigarettes pose as a replacement of cigarettes. It is claimed that they help in quitting smoking. They do come in flavors, and in various levels of nicotine. But, are they less harmful? Do they have any side effects?

For example, Health Canada issued an advisory against electronic cigarettes.

Health Canada is advising Canadians not to purchase or use electronic smoking products, as these products may pose health risks and have not been fully evaluated for safety, quality and efficacy by Health Canada

In recent months, a number of electronic cigarettes, cigars and pipes as well as cartridges of nicotine solutions and related products have been marketed in Canada, and through the Internet. Most of these products are shaped and look like their conventional counterparts. They produce a vapour that resembles smoke and a glow that resembles the tip of a cigarette. They consist of a battery-powered delivery system that vapourizes and delivers a liquid chemical mixture that may be composed of various amounts of nicotine, propylene glycol, and other chemicals.

Nicotine is a highly addictive and toxic substance, and the inhalation of propylene glycol is a known irritant. Although these electronic smoking products may be marketed as a safer alternative to conventional tobacco products and, in some cases, as an aid to quitting smoking, electronic smoking products may pose risks such as nicotine poisoning and addiction.

A research study in late 2015 seems to add weight to Health Canada's claims. In the press release (which was quoted uncritically in many newspaper headlines e.g. The Guardian ) one author stated:

Based on the evidence to date, I believe they are no better than smoking regular cigarettes

So the question is, is an electronic cigarette significantly healthier than a normal cigarette? Is an electronic cigarette with non-nicotine cartridges not harmful whatsoever?

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Probably, as long as it doesn't Explode in your mouth. – Tester101 Mar 26 '12 at 18:30
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The word better sends up big red flags that the question you are asking is bad subjective. It is directly asking for opinion and so answers to those questions tend to have lower quality answers. Try to define "Better" as something for you. IE less damaging to your lungs, less addictive, less alergenic, cheaper, etc. Please choose a single quality to focus on. Preferably one with a notable claim that says it is. – Chad Mar 26 '12 at 19:24
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There are three separate questions here. (1) "Are electronic cigarettes (with nicotine) safe?" (2) "Are electronic cigarettes (without nicotine) safe?" and (3) "Are electronic cigarettes 'better' than normal ones?" Currently, you have only shown notability for the first claim. Please provide references for the other claims. Also, as Chad suggested, define what 'better' means. – Oddthinking Mar 29 '12 at 5:30
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I've been using them.now my clothes don't stink.I never cough, I'm not running out of breath when I take long walks.And I generally feel better.they are a true miracle not even caring about FDA approval.They approve alot of dangerous prescription medicines and maintain that people who smoke cannabis(I don't) should use marinol? So with that being said I trust my own judgement. – user12049 Mar 21 '13 at 23:29
    
@user12049: glad to hear you're having a good experience, but Skeptics is intended to collate evidence, not anecdote. – Paul D. Waite Sep 26 '13 at 9:58
up vote 15 down vote accepted

In 2009, the US Food and Drug Administration (FDA) did a chemical analysis of several products from two leading brands of electronic cigarette.

What they found was disturbing. Here are some excerpted points:

  • DPA's analysis of the electronic cigarette samples showed that the product contained detectable levels of known carcinogens and toxic chemicals to which users could potentially be exposed.

  • Diethylene glycol was detected in one cartridge at approximately 1%. Diethylene glycol, an ingredient used in antifreeze, is toxic to humans.

  • Certain tobacco-specific nitrosamines which are human carcinogens were detected in half of the samples tested.

  • Tobacco-specific impurities suspected of being harmful to humans—anabasine, myosmine, and β-nicotyrine—were detected in a majority of the samples tested.

  • The electronic cigarette cartridges that were labeled as containing no nicotine had low levels of nicotine present in all cartridges tested, except one.

  • One high-nicotine cartridge delivered twice as much nicotine to users when the vapor from that electronic cigarette brand was inhaled than was delivered by a sample of the nicotine inhalation product (used as a control) approved by FDA for use as a smoking cessation aid.

A more technical description of the process was also published.

These results suggest that the manufacturers claims (as of 2009) are not to be trusted, that electronic cigarettes contain a number of dangerous compounds and that they are unsuitable as a mechanism for quitting smoking.

Note: At least one manufacturer disputed these findings.

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8  
The question asks for comparison to regular cigarettes, though... – Ilari Kajaste Mar 29 '12 at 5:06
    
Good point, @Ilari. I think that is a poor aspect of the question, and I will address it with the OP. – Oddthinking Mar 29 '12 at 5:26
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I'm deeply suspicious of most of these "numbers". I would like to see comparisons not only to regular cigarettes, but also to drinking straws and other "perfectly safe" items that go through a normal manufacturing process. I'm particularly suspicious that someone is attempting to hoodwink me whenever I see "XYZ, and ingrediant used in ABC", as that's a trick of demagoguery and not science. – user73917 May 9 '12 at 19:02
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That bad things were found is, probably, unsurprising. It is also irrelevant. The only fact that matters here is the relative amounts compared to those inhaled when smoking a normal cigarette. Does anyone claim electronic cigarettes are worse? Regulators and health departments are somewhat prone to make knee-jerk reactions to anything related to smoking without making sensible judgements about harm reduction. – matt_black May 10 '12 at 23:26
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@matt_black: That depends whether they are being advertised (and perceived) as "safe" or "safer", and a short-term quitting tool or a long-term replacement. There is an obvious safe alternative to smoking (abstention) which the health advocates need to promote over electronic cigarettes. – Oddthinking May 10 '12 at 23:58

Depends on what you mean by "better", and what you mean by electronic cigarette.

The FDA report that Oddthinking links to addresses the question of whether e-cigarrettes are useful as an aid to kicking nicotine, and I think that the fair answer to that is probably not: e-cig marketing doesn't seem to focus on ceasing to inhale nicotine into your lungs, it focuses on ceasing to inhale smoke into your lungs. These are products marketed towards addicts, and the manufacturers have every reason to want their customers to remain addicts. 

But what the FDA report does not address at all is a comparison between the long term health effects of smoking vs. vaping, for the very simple reason that there isn't any data on that. So if by "better" you mean "has fewer long term health effects" the answer is "insufficient data."

If you mean better for your health in the short term than the answer seems to be yes, although the media claims that studies differ. In the article linked, we see references to two studies, one of which found that lung irritation occurs and remains for ten minutes after five minutes of e-cig use. That study did not compare air flow impedance from cigarettes with e-cigs, though, so from the point of view of "better" it contains no information at all. In a study that compared the effects of smoking conventional versus electrically heated tobacco (not e-cigs), smoking had more adverse effects on lung capacity. The study on e-cigs saw indications of lung irritation, but not decreased lung capacity. They also didn't analyze the ingredients of the e-cigs they studied or compare more than one type. They do mention that the e-cigs they used contained propylene glycol, a known lung irritant, which they mention may have been responsible for the lung irritation. So in terms of pulmonary function the indication is that short term, e-cigs are not harmless but are "better". The second study compared cardiac effects of cigs and e-cigs, and found that e-cigs are definitely "better" in regards to cardiac health.

Another key point is that not all e-cigs are equal. Some e-cigs are sold with sealed cartridges, others are refillable. A consumer using a refillable cartridge has more control over what goes in the e-cig, and can opt not to use propylene glycol, and substitute vegetable glycerin, ethyl alcohol, or even water. No studies have been done to compare the short term effects of various ingredients in an e-cig, though.

But the PG is what gives an e-cig "throat hit", that is, the subjective experience of vaping is different without PG than it is with it, so if "better" includes the visceral pleasure of feeling like you are smoking, this may be less satisfying and therefore not better.

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Electronic cigarettes may not be harmless but they are clearly much less harmful than cigarettes

Public Health England (PHE) produced a review of e-cigs in the middle of 2015 which came to this conclusion:

The role and impact of electronic cigarettes has been one of the great debates in public health in recent years and we commissioned this independent review of the latest evidence to ensure that practitioners, policy makers and, most importantly of all, the public have the best evidence available.

Many people think the risks of e-cigarettes are the same as smoking tobacco and this report clarifies the truth of this.

In a nutshell, best estimates show e-cigarettes are 95% less harmful to your health than normal cigarettes, and when supported by a smoking cessation service, help most smokers to quit tobacco altogether.

From a public health perspective where the goal is minimising harm, this is a major and significant conclusion. E-cigs help people quit real cigarettes and they are inherently safer (though whether you should take the back-of-an-envelope 95% number seriously is a subject of much contention.)

This is unsurprising from a chemical point of view. Nicotine is the active ingredient of cigarettes, it provides the key physiological effect, and it is somewhat addictive. But it isn't what causes the harm: that would be the thousands of other chemicals associated with it when tobacco is burned. This include polycyclic aromatic compounds and tars which are both known to be potent carcinogens. This is well known, Wikipedia-level knowledge. E-cigs don't contain most of those harmful ingredients and the mechanism of inhalation doesn't create them (some are produced by burning).

Some would argue that nicotine itself is a poison. After all plants produce it to deter animals and insects from eating them. But then, so is caffeine.

So it looks as though chemical intuition would support the PHE conclusion.

But a recent study (mentioned in the question) suggests e-cigs are carcinogenic. This headline-friendly study was rebutted in The Guardian by Linda Bauld, a professor of health policy (my emphasis):

...the key issue for this current study of e-cigarettes is not whether extensive and prolonged exposure to e-liquid vapour (of a duration and intensity that wouldn’t occur in human use) changes human cells, but rather what the e-liquid was compared to, and what this can tell us about the relative harm of tobacco smoking compared with e-cigarette use. The authors claim their study shows that e-cigarettes are no safer than tobacco, and experienced science editors in newspapers were quick to reproduce these claims without careful scrutiny of the original article.

In reality this study tells us little or nothing about the safety of e-cigarettes compared to smoking...

In only one small part of the article, not covered in the press release and not picked up by the media, do the authors mention that they also exposed some cells to tobacco smoke... Yet the authors could not directly compare the cigarette and e-cigarette treated cells, because the cigarette treated samples all died within 24 hours. Cigarette smoke was so toxic that the cells did not survive beyond this short period, whereas the e-cigarette cell lines were topped up with e-liquid every three days, and the testing continued for several weeks.

...Indeed an alternative headline for the press release, as a colleague from a cancer charity has already pointed out, could have been ‘cells can survive for 8 weeks in e-cig liquid but only 24 hours in cigarette extract’. In other words, if we compare e-cigarette vapour with fresh air we find the presence of some toxicants, as previous research has done. But it seems from the results of this study that if we compare e-cigarettes with tobacco smoke, e-cigarettes are safer.

Conclusion

If we look at the comparisons actually being done in tests, even the ones that are used as evidence to cast doubt on the safety of e-cigs, the actual conclusion we reach is that they are much safer than real cigarettes.


Supplement: why there is a controversy

But not everyone agrees. The PHE report was heavily criticised and understanding the debate provides useful insight into why there is a great deal of fear, uncertainty and doubt around its conclusion but also why it looks like a good judgement call on the current science.

The response to the PHE report was led by this article in the BMJ. Its key criticisms were:

  • Public Health England’s endorsement of the safety and efficacy of e-cigarettes is based on uncertain evidence

  • The quality of evidence that e-cigarettes help smokers to quit is weak

  • Recent evidence questions the conclusion that e-cigarettes are not a gateway to smoking

  • Until better evidence is available public health strategies should follow the precautionary principle

The tone of the article, especially that last point, suggests that the right standard is not harm reduction but absolute proof that e-cigs are completely safe. The critique also made the strong claim that some of the evidence relied on by PHE was based on studies containing serious conflicts of interest (CoI). In responding to this critique, David Nutt, a renowned expert on harms for legal and illegal drugs said (my emphasis):

The justification both commentaries use for this claim is not the data we reported but the fact that a few of the experts in our group of twelve had declared potential conflicts of interests (CoIs) in relation to tobacco harm reduction products. Also it was implied that the funder of the MCDA project, EuroSwiss Health, was paid by the tobacco industry. These claims were publicly refuted by those named straight after the Lancet editorial [where the results were previously discussed], so why did the BMJ article continue in the same vein?

We suggest that in repeating these allegations the BMJ authors were following a sadly all-to-common path for those who disagree with research conclusions to use CoI claims to undermine confidence in the findings rather than to critically analyse the data. A charitable view could be that they in fact can find no fault with the data (other than they dislike the conclusions), so have no alternative but to attack the scientists who generated it.

Another response pointed out that the critique of the PHE report was ideological:

McKee seems to start with the view (in not just this piece but in many others) that we must crusade against anything associated with the evil tobacco industry. If the industry likes it, we should oppose it. Other players in the debate (including that of Public Health England) adopt a more pragmatic position that the focus of tobacco policy should be harm reduction.

You don't actually need to look at the quality of evidence to know how it will be interpreted, you just need to know which camp the author is in.

The ideological position of fighting a crusade seems to lead to position where every weakness in a piece of evidence is interpreted as industry spin, conflict of interest or a damning fundamental flaw. All things not proved to be harmless should be opposed even if they clearly reduce harm dramatically compared to the alternative. The slightest hint of e-cigs being a gateway to tobacco use is proof that they are even if the clear weight of evidence suggest this effect is insignificant.

But ideology does not make a good basis for rational policy assessment. And it encourages exactly the same unscientific tactics as the evil tobacco industry adopted to try to deflect the evidence of harm when it first appeared. McKee et. al. demand absolute proof of safety and seek every possible piece of uncertainty and doubt on the existing studies. But their standard is a poor basis for health policy (harm reduction not absolute harmlessness is surely a better position) and exacerbating every flaw in studies is exactly how the evil industry tried to minimise the evidence of harm. Just because you are on the side of the angels doesn't mean this tactic is a sensible scientific way to build public health policy.

These two responses do a good job of summarising the debate. A key point is the issue that absolute safety is a distraction and better safety than cigarettes is more reasonable (the evidence is pretty clear on this point: e-cigs are much safer).

Critics are not showing that e-cigs are as bad as cigarettes; they are arguing that they are not absolutely safe. This alone explains why there is so much FUD on the topic.

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