posted by Carl V Phillips
I have to leave my series on what constitutes useful evidence as a cliffhanger for another day or two, because people are clamoring for my comments on the latest in the series of studies about e-cigarette vapor chemistry that was recently published. (Article summary here; full version is paywalled.) The study tends to confirm what we already knew about vapor, and the fact that it does not contain important quantities of unexpected toxins. This is certainly good news for e-cigarette users (vapers) and THR advocates.
Before continuing with the study, though, it is worth tying this in to the current series I interrupted and asking, “How did we know that?” The bulk of the evidence comes not from the half-dozen or so lab studies that have been done, but from the basic chemistry and physics of the situation.
That is, how do we know that e-cigarette vapor is not similar to cigarette smoke? The same way that we know that it is not similar to monkey urine — with our scientific reasoning process that says, “Why would we ever even expect it to be similar?” Cigarette smoke is produced by burning complex plant matter which produces a lot of the many known products of combustion and a little bit of more chemicals than we could ever count. E-cigarette vapor is produced by heating a liquid of (mostly) known chemistry, very much not like plant matter, into a vapor phase with little change in the chemistry other than its physical state. The best evidence that we have that they are different is right there in that reasoning.
One of the biggest mistakes that THR advocates can make is to implicitly endorse the anti-scientific tactics of anti-THR activists, who would pretend that most of the evidence does not exist. In other words, it is a potentially fatal error to send the message, “Because of this study and the handful that came before, we know…” rather than the more accurate and useful observation, “Before the first study was ever done, we were 99% sure that…, and these studies show that, indeed, we did not overlook anything in our previous reasoning.”
If you live by the one-off little study, you will die by the one-off little study. There is an obvious response, by those who seek to prevent harm reduction, to all of the chemistry studies that have been done (including those spun by the anti-THR liars, which have actually shown the same good news as the others). They can say, “these only looked at a few samples of the product, and we do not know what might be in other or current products.” This is a reasonable response, though ultimately not true.
It would be completely true if I had phrased it differently, substituting “they do not provide observations about what might be in…” rather than “we do not know what might be in…”. “We do not know” is a lie is because of all the rest of our knowledge, apart from the handful of studies. But if we seem to be claiming the handful of studies are what really matters, we are arguing the liars’ case — after all, eventually one of these little studies will get a bad result due to lab error or real contamination.
Circling back, what is contained in the “…” a few paragraphs back? The main observation there is that e-cigarette vapor contains the same stuff as e-cigarette liquid (disbursed into air), in obvious contrast to cigarette smoke, which is obviously not just the contents of an unlit cigarette plus air.
Should we be worried about unwanted chemicals in e-cigarette vapor, then? Well, basically: garbage in, garbage out. That is, whatever is in the liquid will end up in the vapor. If the liquid is contaminated with something that should not be there, it will also be the vapor (though this creates approximately a zillion times as much concern for the vaper herself as for any bystanders for reasons elaborated upon below).
Is there some chemical activity that might depart from this observation? Not much, but perhaps some. And therein lies the very unfortunate limitation of the new study. Its value would have been dramatically increased had they analyzed the chemistry of the same liquid that was used to produce the vapor, a step that would have been quite easy and inexpensive. Any important differences would give us new (because it would be unexpected) information that might help in creating better products. If there result were the expected correspondence, however, it would help reassure us that studying only the liquid chemistry (much easier and quite practical to do for samples from every large-scale production run, and for some portion of small batches) would be roughly as useful as more complicated aerosol studies.
Of course, that tells us what the vaper is exposed to, rather than those sharing space with the vaper (who we expect will breathe some of whatever was exhaled by the vaper, just as we always breathe whatever people around us are exhaling). This is important because much of the rhetoric coming from the anti-THR liars claims that the exposure of bystanders justifies enacting bans on the use of e-cigarettes in public, and even private, places. But the exposures of bystanders are going to be attenuated compared to vapers by both dilution (a little bit of vapor in a lot of air) and absorption (most of the content stays in the user unless he is intentionally quick-puffing in order to make a cloud rather than to more effectively deliver nicotine by holding the vapor longer).
The recent German study — which was spun by the authors’ and others’ anti-THR lies (links above) as showing a serious risk to bystanders when it actually showed quite the opposite — looked at exhaled vapor, providing a better measure of the actual environmental exposure. The new study, unfortunately, just diluted the vapor that the vaper would inhale, a rather odd arbitrary methodology. This was apparently supposed to offer some measure of what a bystander would be exposed to, but it fails to do that. Mostly what it does is make all of the quantitative results meaningless, except in relation to each other. The arbitrariness is clearly illustrated by considering what would happen if, instead of diluting the vapor into roughly half a cubic meter of air [the rest of the paragraph is UPDATED based on first comment] and then apparently multiplying the concentrations as if this were diluted to a 40 m^3 room, they had diluted it into a different volume. In an alternative scenario, the concentrations would have all been changed by some multiplicative factor, assuming we ignore any actual effects of the room (gravity, adherence to solid surfaces). Moreover, even if they chose the “right” dilution factor (whatever that might be), this would still not mimic the exposure of a bystander (read on).
This means that only the relative results matter. The relative comparison is made is to cigarettes smoke, but we already knew that there was a big difference. The comparison does not answer the question about whether the real-world concentration of chemicals from e-cigarettes is “too much” (whatever that might be judged to be by a hypothetical rational and honest policy process). A similar observation about the sensitivity to the dilution mattering is true for any study of vapor (or smoke) also, but in this case the dilution factor was utterly arbitrary. It was far smaller than a room[‘s dilution given that that large number of puffs represents a lot of vaping time], but far larger than someone’s lungs.
I bring up lungs again because, despite how this study was spun, this was a study of “first hand vapor” not “second hand vapor”. The methodology description is a bit incomplete, but it is pretty clear that there was no attempt to simulate the process of the vaper absorbing most of the content of the vapor or a smoker absorbing the smoke to which it was being compared. Yet the press release had the very unfortunate headline, “New e-cigarette study show no risk from environmental vapor exposure”. The second-biggest flaw in this headline is the reference to environmental exposure, which was not studied. Unfortunately, two of the people quoted in the press release make the same mistake as the headline, with one of them even making the error of referring to “second hand vapor”.
Of course, if what the user is exposed to does not contain anything we should be worried about, then the much lower exposure of the bystander is even less worrisome. But, again, we know that because it is obvious for numerous reasons, not because of this study.
Finally, there is that “no risk” claim. This is another example of the overblown claims that — as I argued previously — will ultimately harm the cause, not help it. First, a chemistry study is not a health study, and does not include any measures of health outcomes. This study looked at more results than the example of overblown claims I cited in the previous post, but that other study had the advantage of measuring health outcomes. A claim like “found levels of environmental exposure that are not considered worrisome for health” would be fine, but no actual health claim can be made based on chemistry results like these.
Second, the claim “no” (as in “no effect”) is never a legitimate scientific claim. “Too small to measure” — great. “Showed no evidence of an effect” — fine. But we can never be sure there is no effect. It is generally suspected that nicotine is a little bit harmful, though the effects are too small to measure. Some people are definitely sensitive to polypropylene glycol exposure. Further similar observations can be made about the contaminants. So if someone breathes enough of the vapor (and, again, the absolute concentrations that were measured were totally arbitrary), there could well be some harm. Nothing is gained by pretending otherwise.
Finally, as a policy analyst, I have to strongly object to treating natural science results as if they provide policy analysis as was done in the press release (though not in the actual article). Do these results show that we should not ban vaping in any indoor spaces? Definitely not. Nor would have less-reassuring results shown that we should ban indoor vaping in some indoor spaces. Such claims require both a statement of the ethical basis for imposing restrictions on people’s choices and the accompanying economics (assessment of costs and benefits) which would be informed by the natural science results. That requires several more steps than are ever included in a research report.
Tobacco harm reduction, anti-THR lies, and related topics 
As clearly stated in the article: “From these results, risk analyses were conducted based on dilution into a 40 m3 room and standard toxicological data”. Not a “half a cubic meter” as claimed above.
Furthermore as a toxicological risk analysis was performed, as mentioned in the above quote from the article, this was not merely a “chemistry study”, but was indeed also a health study. Did you see the whole article Carl, and especially the supplemental tables which detailed the extensive toxicological risk analysis?
Hmmm. Re the first paragraph, it is not actually quite so clear. But I think you are probably right, that the best way to infer what they did from a couple of statements is that the absolute numbers are based on multiplying the half m^3 that was the dilution that they actually did by a factor of appx 1/80. It is kind of annoying that we have to infer simple methods points (they could have easily made that clear in the notes for Table 2 or otherwise stated it) but that does seem to be the best interpretation. It does not change anything really, but I will go update the text of the post to reflect the correction for those who do not read all the comments.
As for the second bit, I strongly disagree. I did not see the supplemental tables, but it is fairly obvious from the descriptive text about them that they compare the observed concentrations to some measure levels that are considered hazardous. That is fine — see the previous posts in this blog that did exactly the same thing. It leads to the conclusion that I suggested: that the levels of the chemicals are not worrisome. But he tables are described as toxicology analyses, and I would say this employs a oddly broad definition of the term (something like “any analysis that relates to toxins”) — they did not actually do any toxicology, as we normally think of it, any more than Elaine did here; they just compared their numbers to those already calculated from toxicology studies (or to those from epidemiology studies, in some cases). Still, with or without any toxicology, the results are only suggestive of health effects if there is no measure of health outcomes. Again, it is fine to say something like “did not find any reason to believe the exposure will cause a measurable risk of disease in bystanders”, but not (as in the press release), “toxicology analysis detected no risk (cancer or non-cancer risk) to public health”.
I agree with several of the comments made by Prof Phillips. Indeed, the study did not examine enviromental exposure, although i think since they did not find any hazardous substances in “first hand vapor” it is almost impossible to find something bad in secondhand vapor. Moreover, this was a chemical study and provides theoretical data about health hazards (or safety). Although these are also important, by definition it was not a clinical study concerning health effects.
Besides theoretical knowledge about electronic cigarettes, should we make such studies to verify the obvious? I think we should. The reasons for this are multiple. First of all, in science we should always try to prove that theory is applicable in reality. But even beyond that, electronic cigarettes have recieved such controversial “reception” that we are obliged to answer to all criticism by data and not by theory. Most scientists acknowledge that in theory electronic cigarettes are probably by far less harmful that tobacco cigarettes. Even those extreme opponents of the product know it. However, how can yopu reply to all of them sayiong that only few data are available and that we still don’t know if they are less harmful? Answering in theoretical terms (although there is a strong logical basis and background) is not enough. We are outnumbered by opponents, so we have to use other means. And my opinion is that studying the obvious is a way we should proceed.
Today i read a review on electronic cigarettes published in a greek respiratory journal. It was written by two associate professors in respiratory medicine. In general, the article was surprisingly balanced (in fact, not that balanced, but knowing the way respiratory physicians oppose electronic cigarettes i was expecting it to be more aggresive and biased). Of course they were discussing about the FDA results and conclusions, however they also cited the review by Prof Siegel stating that the amount of nitrosamines are 500-1400 less in e-cigarettes compared to tobacco cigarettes. Anyway, the last paragraph of the article was the conclusion. And i really could not believe what i was reading. They state: “Smokers who have decided to quit smoking should not exchange a carcinogenic product with another carcinogenic product…”!!! Wow. For someone who read the whole article, that conclusion was a real surprise. At first i thought i was reading a different article! This statement had nothing to do with the rest of the article. However, it was the exact statement made by the European Respiratory Society concerning e-cigarettes. And now, how can you convince people (and politicians) that a respected scientific association is having such an irrational, unsupported opinion?
Unfortunately, e-cigarettes are in a position that even the obvious should be studied and presented, otherwise we may loose the chance of providing a product that has the potential to revolutionize tobacco harm reduction…
And with regard to the data resulting from firsthand vapor, rather than exhaled vapor, that is discussed as a limitation in the paper. However, since exhaled, secondhand vapor is, as you acknowledged, clearly going to contain less of any and all substances found in firsthand vapor, the fact that the study results can only be viewed as a “worst case scenario” can also be viewed as a strength of the study.
When someone writes “limitations” caveats in a paper, they are supposed to represent claims of “we did the best we could to do this research right and report the results accurately, but this consideration might have been an issue”. That clearly does not describe the present situation. They compared highly diluted (first hand) vapor to (first hand) smoke. This was not a “limitation” of the research — it is what the research did. But then the wording of the paper, and even more so the press release, claimed that they did something else entirely. They did not accurately report “we did X” and then go on to discuss how they believe this is a rough way to extrapolate to a worst case scenario ceiling for a rather different question of interest. This is not a limitation, it is a misrepresentation of the study.
As for the point about it being a worst case scenario: For the comparison to (first hand) smoke, their results are definitely not necessarily worst-case. Both parts of that ratio are affected (reduced for everything or almost everything) by the user’s absorption, and the impact on the ratio could go either way. As for the absolute numbers, it does indeed seem like a safe prediction that the environmental effect of releasing the production from a quite large number of puffs into the environment is an overestimate of almost every, or perhaps every, chemical exposure that someone would really experience standing near several vapers in a small room. The same observation applies to the several studies of vapor chemistry that have come before. But again, this prediction (and the ways in which it could conceivably be wrong for some chemicals) is not a result of the lab results themselves, but an extrapolation from what was observed into what was not observed, and should be clearly stated as such.
And again, I point you back to my first substantive observation: We already were quite confident that there was no worrisome exposure to bystanders, extrapolating from previously-existing evidence. And we still are, extrapolating from all the now-existing evidence. That is good. But it is a mistake (and dishonest) to misrepresent the basis of our knowledge.
KF makes a valid argument (in previous comment) with: “Answering in theoretical terms (although there is a strong logical basis and background) is not enough. We are outnumbered by opponents, so we have to use other means. And my opinion is that studying the obvious is a way we should proceed.”
I agree that there is probably some rhetorical value in using empirical data to confirm the obvious. But we cannot surrender true scientific analysis in the process. All science is extrapolation; if we fall into the trap of not using science, then we open ourselves to the obvious criticism “well, maybe those four particular batches of e-cigarette liquid did not produce deadly vapor under those circumstances, but what about the next ones under other circumstances?” The observation “the chemicals in the vapor are the chemicals in the liquid” is not theory, it is scientific knowledge. If we fall into the black swan trap of claiming to only know what we have measured so far, we know approximately nothing. That is exactly where the anti-harm-reduction activists want us to be.
Moreover, some questions are legitimately somewhat open while others are rather settled, and we should not get tricked into chasing the latter at the expense of the former, as I allude to in the post.
But all of this deserves a post (or two) of its own, so I will come back to it at that level.
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I agree with Prof Phillips. Unfortunately however, i think that criticism against e-cigarettes will never stop, whatever studies are performed. We see some hilarious arguments by opponents. For example, they say that nicotine levels are not constant between puffs, or that liquids do not contain the exact amount of nicotine stated in the label. Of course they “forget” to mention that the same happens with regular cigarettes. And not only in cigarettes, but also in NRT (i suppose none can chew a nicotine gum in an absolutely consistent way so that each time the exact same amount of nicotine is released).
Despiter the fact that (from what we know till now) e-liquid components are far less harmful, we still see opponents reproducing the FDA report that “carcinogens and anti-freeze were found”. This is a stigma that is difficult to remove, although studies have been published on this issue. Prof Phillips has mentioned the german study in which results were misinterpreted by the researchers (although we do not know if that was the researcher’s true opinion or they were forced to express such a view by the reviewers). They still continue the scaremongering on e-cigarettes, and the general public remains confused…
In the simplest terms.. this study and its methodology have been peer reviewed by air quality researchers and it is published in one of the leading journals in that field.
Exposure determination followed standard protocol used in previous air studies in that field (as cited in the published article).
Toxicology was determined using less permissive standards that OSHA. ELCR and THI indices are more stringent and are used as a standard and were accepted by per review. The toxicology consulting firm who completed risk analysis was chosen because that is their area of expertise. Feel free to contact them for more information on their chosen method.
It was a limitation of the paper that in 2009 IRB would not approve human inhalation so that method was not an option (as stated in the article). If you do not like the methodology I am sure that now, in 2012 you could get an IRB to approve a study on exhaled vapor. You should consider doing that.
The liquid was tested by GCMS before vapor testing. That should be published in a follow up paper in a journal that is not on “inhalation toxicology”. Since we do not inhale the liquid it was not directly relevant to this particular publication..
Since you believe the research was unnecessary and pointless, would it be alright to just send legislators and scientists your email address and tell them you already know what is in the vapor so we don’t need to provide them with any studies?
I think if you reread what I wrote and the responses to other questions, and try to minimize the filter of defensiveness, you will discover that I did not suggest the study had no value and that I already responded to most of what you wrote. You have jumped into the world of science, and that requires not investing your self-identity in every research result, because there will be criticism. You mentioned peer review — this is what peer review looks like!
You bring up a few things I had not addressed before. First, however typical the methodological details might have been for some aerosol studies, they were still weird for this one. You cannot let the techs or consultants (and especially not consultant techs) decide on the methodology; they will always favor what is easiest over what is most useful, and indeed may have no idea what is most useful. You always need someone who understands the subject matter and the technology, and is interested in the results, to make sure they are doing what you need, not what they want.
Second, when the IRB would not let you use humans as part of the protocol, your choices were (a) find a new IRB, (b) abandon the project, or (c) do a different project. But in choosing (c), you needed to optimize the new project and not pretend that it was still the original plan. If you go to the refrigerator to get some beer to serve and find you are out, and so return with wine instead, you can either apologize for the substitution or spin it as if wine were the plan all along. But it is not a good move to declare that the wine really is beer, just with a few limitations. Not being able to do the study you wanted was a setback, but not an error; misrepresenting what you did as being the study you wanted was an error. There was no reason to do that.
Third, it is good to hear that you have analyses of the liquids. But it is very unfortunate that you did not publish it in the same paper, structuring the analysis around the comparison. I find it impossible to believe that the journal did not want this additional value as part of the same article. As it is, when those results are published separately, any issues with the comparison itself are going to be compounded by the various issues critics are going to level at the recent paper (I am not referring to the concerns I have raised about the spin, but issues about the results themselves that I have not mentioned), plus any issues with the new paper, plus the challenge of cross-reading them. That is going to dramatically lower the value of the eventual comparison, and that comparison represented the vast majority of the potential value-added for this study.
All of this is quite unfortunate, because many problems could have been avoided if you had circulated the plans and a working draft of the results to people who could have offered some advice and some easy fixes for every issue that has been mentioned here, other than the IRB rejection.
As for giving interested policy makers and scientists my email, I am all for it. I would be happy to help try to educate them.
Carl – I think you make some critical points in this commentary. First, the conclusion that electronic cigarettes are much safer than regular cigarettes is hardly based on the results of a single study. It can pretty much be inferred from the fact that electronic cigarette cartridges contain no tobacco and there is no combustion process involved. Multiple analyses of the liquid in e-cigarette cartridges have been conducted and we know the ingredients. Basic chemistry tells us what to expect in the vapor. In many of my commentaries, I have written that “it doesn’t take a rocket scientist” to figure out that vaping is going to be much safer than smoking. Essentially, what I am saying is exactly what you argue in the first part of your commentary.
Second, I agree that the study does not prove that there is “no” risk associated with vaping or “secondhand” vapor exposure. In my commentary on this paper (http://tobaccoanalysis.blogspot.com/2012/10/new-study-provides-more-evidence-that.html), I point out three reasons why this is the case: (1) the presence of nicotine; (2) the respiratory irritant effects of propylene glycol inhalation; and (3) the presence of a carcinogen – formaldehyde – in the vapor. Of course, the issue is not whether vaping involves “no” risks but whether it greatly reduces the risks associated with smoking.
Third, you make an important point by noting that the study does not involve measuring levels of constituents after absorption by the vaper. Thus, estimates in this study of the risk are going to be over-estimated, as many of the constituents are highly absorbed in the lungs of the vaper.
Fourth, you rightly point out that the study measures levels in an experimental chamber and does not simulate real-life conditions.
These last three points are ones that I make in my commentary.
The only question I have about your piece is that you seem to argue that we cannot draw any conclusions from this study about potential risks associated with exposure to secondhand vapor. Would you agree, though, that we can draw some conclusions about the “worst-case scenario” or “upper-bound” levels of exposure? In other words, the study doesn’t account for absorption by the vaper or for dilution in the air. But doesn’t it at least provide some sense of the maximum possible exposure? Can’t we conclude that actual exposure is going to be less than the levels observed in this study? And doesn’t it at least provide information about what chemicals are, or are not present in the vapor? I think the fact that the vapor is devoid of tens of thousands of chemicals and more than 60 identified carcinogens in tobacco smoke does tell us that exposure to the secondhand vapor is much, much less hazardous than exposure to tobacco smoke, even though – as you point out – the paper does not allow any realistic assessment of actual risk..
Mike, Thanks for the feedback. Responding to the question: I think we can conclude that with some confidence, certainly, as I mentioned in the post. But — to expand upon my point — it is via the same reasoning that says we should only need to analyze the liquid: Our knowledge of how we get from liquid to vapor says that we can analyze the liquid to be pretty sure what is in the vapor. Next, our knowledge of what happens in the airway says that we can be pretty sure that whatever is in the vapor, there is less of it in the room after someone vapes. So it is basically the same logic that would say (a) because of this study we can conclude that “second hand vapor” does not contain worrisome concentrations of chemicals and (b) we already knew that without the study.
In both cases, though, there is a chance we are wrong because something very unexpected is happening during the physical step that does not seem like it should be changing much. I am comfortable with the extrapolations involved, but we need to recognize them as such. So that is part of the problem — what was a reasonable extrapolation (from a result that, after all, we could have extrapolated the basics of based on what we knew) was presented as the actual result of the study. It would have been so easy to avoid that mistake (and thus target).
As for it being a “worst case” type measure, I believe that seems to be the case, but it is difficult to be sure. The methodology description is difficult to make sense of. It sounds like the quantities measured were based on what would be a very high level of vaping for a given volume of air, but I am not entirely sure. Using the vaper’s exposure as an overestimate of the bystander’s only works if you get the quantity right. If the authors had explicitly presented their extrapolation, and in so doing had clearly communicated something like “this would be like being with someone who exhaled exactly what he inhaled, who was constantly vaping for a half hour…etc.”, it would have been possible to be more confident of the unequivocal overestimate.
One other point I forgot to make. I think there is value to this line of research because the constituents of the vapor may be different than what is in the liquid. For example, formaldehyde and acrolein have been detected in the vapor but they are not detected in the liquid. Possibly, these chemicals result from the heating of propylene glycol. At very least, studies like this give us a picture of the complete range of chemical exposures that we need to be concerned about. Of course, finding a chemical doesn’t mean it creates a significant hazard, but at least we know the “upper-bound” of the range of potential hazardous exposures that warrant further investigation. At the same time, we know the large number of chemicals and carcinogens in tobacco smoke that are not detected in the vapor, which also gives us important documentation to support our previous “common-sense” conclusion that vaping is much safer than smoking.
I totally agree with that first bit, which is why we would get much more value from studies of “what is in the liquid”-vs-“what is in the vapor produced from that liquid” than from studies of what happens to be in the vapor from some sample of liquids. There would still be the limitation that the results for a different atomizing system might be different, but we would know a lot more. It would be one test of the hypothesis you propose.
I am not so confident of the “complete range” observation — there is still that “garbage in, garbage out” problem. All of the published labs to date have tested a total of, what?, 20 samples of e-cigarette liquid. How many total batches have been produced during that time? A million? The conversion of liquid to vapor is a useful enduring observation. And the consistent bits of the results can give us a good idea of what to expect from a high-quality batch. But when it comes to contaminants, the test of a particular sample is just about that sample. As I suggested above, this really has me wanting to see a world in which we have several tests that map liquid chemistry -> vapor chemistry with great certainty, and then we do *lots* of liquid chemistry analyses — they are not very expensive.
On the last point, yes, I agree with you and Dr. Farsalinos that being able to make simple rhetorical points matters. So there is value in for that in each new study. But I think both the rhetoric and useful knowledge would be better served if we had a better research agenda worked out.
I heard they found DEG in phase 1 but not phase 2. How is this possible if they tested the same liquids in both phases? This is a real concern of mine about our e-liquids. Especially for us older vapers that may have compromised lung functioning from having smoked traditional cigarettes for many many years.
Yeah, that opens a whole other line of questions that I just skipped over in what I wrote. There are several points in the specific reporting (both methods and results) that create more questions than answers. I was actually waiting to see what someone else would say about that before deciding whether to offer any analysis.
First of all i should make clear that by making comments on the study i have no intention to underestimate its purpose or value. I suppose the same applies to both Prof Phillips and Prof Siegel.
Although i agree that liquid is the easiest to examine, let us not forget that we do not use the liquids in liquid format. Probably liquid form is the only way that electronic cigarettes will be repeatedly tested in the future (as part of regulations imposed by public health authorities) but from a research point of view i believe that vapor analysis is the way to go.
The study by Bahl et al (Reprod Toxicol. 2012;34:529-537) tested the cytotoxicity of liquids in cultured cells. They used the liquid in its original form, not transformed into vapor. And of course, they did not test cytotoxicity of cigarette smoke as a comparative measure. Interestingly however, they found that cytotoxicity was directly related to number of flavorings present in the liquid (they used HPLC spikes number as a measure of flavorings, they did not specifically test for the flavoring substances quality and quantity). This study is almost useless from one point, but useful from another. Testing the liquid in liquid form seriously undermines any value of the study in real life and real situations. We do not know if vapor could have more (for examlpe, as Prof Siegel said, formaldehyde) or less substances (for example, a significant part of flavorings may not be evaporated and may just impregnate the wick causing that its discoloration that we all see). In an air quality study like the one discussed above, none will ever look at the flavorings. Let’s remember that flavorings are tested and approved for ingestion, not for inhalation. And we already have bad experience with diacetyl; it is approved for food industry but it causes a rare but serious and irreversible lung disease when inhaled.
Moreover, we should not forget that the way electronic cigarettes are used has significant implications on the chemicals produced. For example, dry burning may lead to production of formaldehyde or acrolein in significant amounts due to high temperature. This is extremely important, researchers should be very familiar with the device when testing it because they can easily produce results not applicable in reality (dry burn is almost immediately detected by the user and he knows he should refill the cartridge with liquid).
Elelctronic cigarettes are very complicated. That is why every stuidy is useful but no study by itself is able to answer to all questions and give us final conclusions. Research should be intensified and rewarded. Any commentary or criticism should not be taken as underestimation of the value or the knowledge it offers.
One of the most useful things about this study (other than confirming things we already ‘knew’) is that it helps identify things that need looking at more. Acrolein is an expected byproduct of the thermal decomposition of glycerol, but there seems to be much less information on what happens to PG – is formaldehyde an expected decomposition product of PG?
Is the presence of these indicative of the heating coil becoming too dry, or is this result representative of vaping in practice? More research could (and should) answer these questions.
That is a part of the value that would be much greater if more information had been reported. Previous studies, going back to the original Laugesen found formaldehyde; I would have to check to remind myself what they reported for acrolein. But in any case, we cannot distinguish, based on the new study, whether these were contaminants in the liquid or largely a creation of vaporization. Moreover, if we assume the latter, we do not know anything that would help us figure out what about the process creates more or less (i.e., we do not know about the specs of the atomizers and such).
This helps further clarify a research agenda. One-off analyses of what happened to be found in a particular sample of vapor are of value only for discovering properties that were so incommensurate with our understanding that they cause use to revise it. But the details are of little value — e.g., the products obtained three years ago for this study are likely no longer available, or have at least been re-engineered, probably more than once. What has some lasting value — and also allows for those possible surprising discoveries — is find the relationship of liquid chemistry and vapor chemistry (as I already noted) and also figuring out what variables (of the atomizer, etc.) affect that relationship. Offering some information about those is what will make a vapor study useful.
As I mentioned to Mike Siegel a few months ago after he wrote a blog about this… If you look at the supplemental tables for the study discussed you will note that the samples with higher measured PG levels have LOWER levels of formaldehyde. Maybe it is a formation from the Glycerine?
Also worth noting… we had 5 users puff the same model cartomizer we used for the study and count the puffs before we started. It was somewhere around 180-200 puffs if I remember correctly. We did only 50 puffs per cartomizer since the machine was not able to detect the “burnt taste” that meant it was empty… we didn’t even let it get close to empty.
We also repeated the same testing with flavorless liquid to try to measure what was coming from flavoring and tested the flavorless liquid on a tank instead of a cartomizer to see what comes from the stuffing.
Hopefully after our next fundraiser we will have enough to afford to have someone analyze that data as well and we can get the comparisons published also.
This is a very important issue. It is good to clarify that you did not use all available liquid in the cartomiser. It is very easy to alter the results by bad methodology, especially if someone is not familiar with the use of electronic cigarettes.
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