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Confused about diacetyl? You should be

Confused about diacetyl? You should be

About the author
Oliver Kershaw

Oliver Kershaw

Founder of and co-founder of

Two prominent Vapestore businesses have recently removed from sale e-liquids they have found to contain “unacceptable levels” of diacetyl and or acetyl propionyl (DA/AP).

This really is the e-cig industry’s zombie issue. It keeps coming back year after year, but never resolved. And it’s a complex one which divides opinion. In this piece, I’m not looking to hash out the rights or wrongs of the companies involved in the latest sagas or to talk about the particulars of these cases, but to draw out some of the perspectives that mean this issue may never be fully resolved.

What are Diacetyl and Acetyl Propionyl?

DA/AP are compounds of the diketone class. DA, in particular, exists widely in nature, and is responsible for the buttery taste of many foods and beverages. It’s absolutely safe to eat or drink, but inhalation is known to be problematic. A number of cases of “Bronchiolitis Obliterans” in popcorn factory workers exposed to DA led authorities to create very strict limits to the amount of DA that workers may be exposed to. It has since been discovered in workers in other manufacturing plants. Bronchiolitis Obliterans is a condition in which irreversible scarring to the lungs is produced, in serious cases requiring lung-transplants. Ironically, the only other known causes of Bronchiolitis Obliterans is lung transplants themselves.

Acetyl Propionyl has a very similar taste profile to DA, and it appears many manufacturers may have chosen to use it in e-liquid as a replacement for Diacetyl in the mistaken belief that AP is safe or safer. There’s ample reason to assume that AP has almost exactly the same safety profile as DA

Why are DA/AP in e-liquids?

Short answer, because they taste great. In addition to being a buttery flavor, DA/AP can give fruit flavors a “ripe” characteristic and are, in a sense, the “monosodium glutamate” flavor-enhancer of vaping.

The longer answer is a bit more interesting. In 2010, the vaping community became aware that DA was present in e-liquids and that this was a problem, and the few e-liquid manufacturers who were around back then took it seriously enough to make efforts to remove it from their e-liquids. Those manufacturers requested of their flavor suppliers that the flavoring compounds they supply did not contain DA, and most thought that this was the end of the story.

Skip forward to 2014, and Dr. Konstantinos Farsalinos was conducting some tests on e-liquids from a German supplier, and he made a discovery: the e-liquid contained DA in concentrations far higher than the NIOSH occupational hazard levels, and yet the manufacturer was absolutely unaware that there was any DA, despite having previously tested for it. So what had happened?

Quite simply, there is not a one-size fits all testing approach that is appropriate to shoehorn e-liquids into (although see this document by Nicoventures/BAT). The laboratory must know what they are looking for, and they must set the correct “limits of detection” in their equipment. Standard GC/MS wasn’t picking up DA because the limit of detection was set at around 1%, which is way above the NIOSH DA limits.

Dr Farsalinos was shocked. He assumed that if this e-liquid contained DA, and the manufacturers were unaware of this, then others would have the same issue. He went to the vaping community and crowdsourced funding for a large test of popular e-liquid brands which he purchased anonymously. Again, what came back shocked him - the vast majority (74%) of the sweet flavored liquids he tested came back with DA/AP, and 47.3% of DA and 41.5% of AP-containing samples exposed consumers to levels higher than the safety limits.. Rather than publish the names of these companies, he wrote to them directly telling them the issue and urging them to remove DA/AP from their future stocks.

Clearly, with some companies at least, this has not happened.

So, are these chemicals dangerous to vapers?

This is the $64k question. Those cases in which diacetyl was seen directly to cause broncholitis obliterans were cases in which workers were exposed to an actual vapor from heated flavorings. Despite the name, vaping itself is actually not, in the main, the inhalation of a vapor, but of an aerosol. In an aerosol, the particles from the gaseous phase have condensed into larger droplets. It’s unclear whether these droplets are capable of depositing DA/AP deep within the lung.

However, there is a vapor component to the output of e-cigarettes, and this likely varies according to the composition of vape juice. For example, greater water content in e-liquid may result in a greater vapor component, and it’s possible a greater vapor component would lead to DA/AP being delivered deep into the lung tissue. The fact is we simply do not know at this stage what the dynamics are.

Fine, but where are all the dead vapers?

Many vapers make the following points in defence of DA/AP: Firstly, that in over 7 years of popular usage of e-cigarettes no-one has suffered Broncholitis Obliterans, and secondly that smoked tobacco typically contains more diacetyl than those e-liquids in which it is found.

However, this line of reasoning falls down. While it is true that DA has not caused fatal Bronchiolitis Obliterans in vapers, there is great uncertainty about its contribution to disease amongst smokers. Firstly, COPD and emphysema are conditions whose causes are not fully understood; it’s likely that DA has at least some contributing factor to both (As stated by Farsalinos at GFN). Secondly, it’s likely that Bronchiolitis Obliterans is actually underdiagnosed. A positive diagnosis requires invasive biopsies, and so most smoking related respiratory conditions are diagnosed as COPD or emphysema.

Regardless, DA/AP do not need to be in e-liquid, and so their inclusion can be thought of as an “avoidable risk”. After all, you can vape e-liquid with no flavors at all.

This, though, leads neatly to a very interesting divergence of opinion, and a debate that seems unlikely to be resolved any time soon….

So, should all DA and AP be removed?

It may be the case that DA and AP do impact on lung health in both smoking and vaping (although see Dr Polosa on emerging evidence regarding lung health in vapers), so it should clearly be removed, correct? Well, the notion that e-cigarettes need to be 100% safe is actually something that seriously divides opinion amongst high profile commentators, scientists and, of course, vapers.

The core debate is between “harm reduction” and “absolute safety” advocates. And this is where things get really complex!

On the one hand, there’s what I’ll refer to as the “Clive Bates” position: Anything that’s safer and causes smokers to stop smoking should be encouraged, even if it entails a risk that is greater, or much greater than 0, but also much less than smoking. In particular, if a flavoring compound creates additional risk but it also appeals strongly to many smokers, at the population level this will cause a reduction in overall harm because more smokers will transition.

Then on the other, there’s the two “Farsalinos positions” (the hard and the soft versions): In the hard version, anything that’s an identifiable risk should be eliminated. This is a technology - not a burning material - and anything which can be done to reduce risk should be done, and anything harmful in the e-liquid (excluding nicotine) can be and should be removed.

The soft version: If an e-liquid is produced which contains ingredients that are known hazards this should be made clear to the consumer such that they can make an informed choice as to whether or not to consume such products.

Actually, and without speaking to or for Clive, I would suggest that his position and Dr. Farsalinos’ (soft) position can be reconciled. That is to say, I don’t think Clive would necessarily consider it problematic that consumers be informed about risks with certain ingredients, so that they can make an informed decision.

That said!!!…

How do you communicate risk to consumers, especially when there’s really no data or evidence available to consumers as to what that risk might be? It’s hard enough to explain risk about hazards that are well understood by experts; smokeless versus smoked tobacco, for instance (although bureaucratic inertia and ideology play a big part in that specific example). How do you communicate risk in a way that does not interfere with consumers choosing a much safer alternative? If you say: contains DA/AP, a substance known to be associated with lung conditions, do you put smokers off vaping entirely? Do you put them off choosing a DA/AP containing liquid that would have otherwise helped them to stop smoking? What is the effect in overall population terms? And how truthfully are you actually communicating? After all, the current body of science suggests what you’re really saying is this: “contains DA/AP - substances known in other scenarios to cause irreversible lung damage, but whose safety in e-cigarette products is currently completely unknown” - and how is any consumer able to make a rational choice from that?

But what about the manufacturers? What is their perspective?

I would suggest that this debate is playing out in the wider industry, albeit in less explicit terms. On the one side you have those who wish to create products that are highly appealing to consumers, and aren’t concerned about making them as safe a s possible. On the other you have those that maintain that vaping should always be as safe as possible and who take great effort to ensure risk factors are not present in their products.

Sadly, once again, the consumer is the one who’s left confused and under informed.

That’s me! I’m so totally confused. What should I do?

Please don’t panic. The main thing is to always think about the relative risk. Even with e-liquids that contain diacetyl, it’s still massively safer than smoking. There’s no question, the absolute worst thing you could do is to throw out all your vape juice and go back to smoking.

Instead, you should think about whether the pleasure you gain from using a DA/AP liquid is such that you need it to remain smokefree long term, and perhaps consider phasing out using DA/AP liquids over time.

Once again, the absolute worst thing vapers can do is panic and feed more panic: this will just lead to more smoking.

What should the industry be doing?

My personal view is that unless and until the industry can show that DA/AP in e-liquid is safe for vapers, those whose liquids contain it should make it clear to consumers this is the case, either through a labelling convention or something else. This won’t solve everything, but it will at least confer some agency to the consumer to make informed decisions. I think the community really does need to push industry hard for this - even those who have no problem with consuming DA/AP should at least consider those who really do not want to, and have the right to know.

Of course, there are other dynamics at play, such as the media relentlessly causing fear and uncertainty, but I think this idea that informed vapers become more concerned over time should be taken seriously by industry players who want to remain competitive, and it serves vapers well by keeping a perpetual check on the safety of vaping products.

Finally, a video - Dr. Anne Hubbs discussing DA/AP inhalation, the history of popcorn lung, and DA/AP in e-cigarettes (h/t Russ at Click.Bang)


  • Tim Eagan

    Can those of us who cannot afford to contribute still show how long we have been without analog cigs ?

  • PSiKoTiC

    I personally think RJR is jumping on the bandwagon not so much as to 'tap into the vape market' I mean if you look at the numbers on vaping and PV's all together vs Analog sales, I'm pretty sure the analogs will be netting well more than the entire vaping market. This reminds me more of the introduction of the electric car. It's a relativley small niche market in comparison. These Ecigs are not the same product and I think they're marketing the Ecigs (Both Vuse and Mark10 from Phillip Morris) more for public image and specifically liability, I mean it's alot more difficult to implicate big tobacco in sales when even they're pushing a viable (safer?) alternative. On the other hand, depending on regulations that will presumably be passed by the FDA this also allows big tobacco a whole new market of potential next generation analog cigarette consumers. Where as I've tried myself some of the Ecigs that are popular (Njoy in this case) me, being an avid vaper using an ecig 'mod' as they call it (clunky in comparison to these disposible or cigarette sized/shaped rechargable ecigs) The vaper production is relatively low, me; being a pack and a half smoker a day, destroyed one of these Ecigs in about 2 hours. at ten bucks a pop, That doesn't work out to cheaper than buying analogs. And with new non-smokers trying out this product what are they to do when their battery dies, or their disposable dies mid shift/day? I would be so bold to suggest they would be much more inclined to try an analog (normal cigarette) vs a non smoker that has never used these smoke free products. Long of the short; there is already far superior products on the market, for significantly cheaper. Aswell you can easily make your own 'Ejuice' and are refillable. Google 'Ecig' and check out the market on these. the Ego-510 is cigarette shaped and been around for quite some time now, Long of the short they're trying to pull an al gore and 'invent' something that was already invented and claim they made it; when they've been against it the entire time (obviously).

    My concern with these products being an avid vaper myself is that they will as I mentioned with me finishing one of these Ecigs in less than 2 hours (@ 10$ each) scare people off of vaping due to the insane costs. If this Ecig was the only Ecig I ever tried, I would continue smoking analog (normal) cigarettes as the Ecigs being sold here simply cost too much and aren't as convenient, where as the e-cigarette itself is pretty good, it still died in less than 2 hours of moderate/heavy use. Ending up being less convenient and more expensive than traditional cigarettes, if history teaches us anything we will always return to the tried and true, or the most convenient, both of which the traditional cigarettes in this example are. I'm positive big tobacco is counting on it.

    As with the 'other' Ecigs I believe they're amazing, and am thankful that they are there, Do it yourself vaping is probably not going to be going main stream anytime soon, however you get the satisfaction of being able to save a 'ton' of money, and even make your own Eliquid/Ejuice if you so choose. As I have been suspicious of big tobacco with the Vuse and Mark10 they do not list ingredients in their 'Eliquid' used in the cigarettes. Making your own you can know exactly what your vaping. (Fyi: With a Ecig 'Mod' it's Propylene Glycol, Plant Based Veg. Gylcerine, Nicotine and 'professional food grade flavoring) Now why big tobacco wouldn't list these ingredients in their E Cigs if that was all they're using is beyond me.

    In conclusion;

    Ecig chemicals used:

    I would be wary of 'any' E-cigarette that isn't 100% frank and upfront with all contents being vaporized (and inhaled) and big tobacco isn't seeming to be upfront about this.


    These look kinda 'neat' but my god are they expensive, there are already far superior products out there, Google 'Ecig 510' or Ecig mod' to find any huge plethora of (Yes.. many are made right here in America) 'better' ecigs, at a much much lower price point.

    Some 'rough' numbers in my experience for a small 510 format (Cigarette looking Ecigarette) is about 37.50$ USD. Which includes 2 rechargeable batteries, and battery recharger with it.

    The Eliquid you pour into it costs about 20$ per bottle (30ml) me being a pack+ a day smoker a bottle lasts me roughly 2-3 weeks.

    (Where as I 'used up' one of these Ecigs big tobacco is selling in less than 2 hours)

    What I'm pressing is there is alot better stuff... made right here in America already for alot cheaper, where you can see all the ingredients put into the Eliquid

    Happy Vaping,

  • Sergio Luna

    is there a specific way to charge these or can i just use a cell phone usb charger?

  • Jim Pearce

    Let's not kid ourselves. It's only a matter of time until our bought legislators outlaw our products. Let's enjoy this while we can. It's as if we are living in the days prior to the Harrison Act. Eventually our trade will bedriven underground and into a black market. Prices will skyrocket, jails will continue to fill, and violence will be part of the biz, just like any other dope ''crimes''.

  • Kevin barreto

    I am currently reviewing this product for C & C marketing. In all honesty it doesn't compare to other ecigs currently on the market. The flavor I have(original) is very strong has a very bad after taste. The reviews I give this product will not be good. Not to mention it only lasted about 4 hours. A pack last me about a week so saying this is equivalent is incorrect.

  • Brooke Youngberg

    I got a mailer from them, free solo and free set of carts. I'm a sucker for a coupon so I do plan to get it since it's free. I have no plan for this to replace my current e-cig as I have tried cart based e-cigs and my current self fill system is leaps and bounds beyond it. This will probably be a back-up for when mine is charging. As for those that asked what they are going to do with all the carts, their info they sent to me says they have a recycle program and you sign up online and they send you a prepaid mailer to send yours back.

  • disqus_6rDEDMBkFC

    sorry, i'm arriving late to the party as usual. i've used the vuse consistently for a few days now; and that's only because i'm waiting for a larger check to arrive so that i can purchase a mechanical pv. hence, the reason that anyone should use a vuze. while vapor production and throat hit are fairly decent, it's regular flavored tip tastes like s*** and menthol has some sort of aftertaste that, again, came out of the hind-end of something that i think walked on four legs. the worst of it is that i defended the vuse a couple of days ago, and i still would IF the tips either lasted longer than they do or if they were refillable. so, i can't defend the vuse because it's too expensive to run, it's tips don't last all day and neither does the battery. all said, it would cost me about $4/day, and that's a price that i cannot rationalize, the product is not worth it. so, in my mind here is what RJR may be thinking: sell the tips for $3 per, fill them with a higher dose of nic (48 mg) and target people who don't know squat about pv's. just another serving of crap from the evil empire.

  • nancy

    I heard that i can get a coupon to help me get this to stop smocking and i will like to kmow how do i get the coupon thank u

  • blackHoleOblivion

    Whatever you do, DO NOT plug the USB charger into a high-current adapter, such as the 2-4 amp ones out these days. I suspect it killed the battery somehow (on both of mine, one new and one a couple months old). I'm guessing 1 amp is the highest it can handle (for whatever reason). They should really put a warning on the box about it.

  • Fred Saj

    Wow that was amazing :) I think vaping is much better than smoking :) Thanks for sharing :) I really appreciate :)

  • Fred Saj @VapeCrepe

    Thanks :) I was really looking for different flavors :) I really appreciate :) Keep on sharing such Articles :)

  • Fred Saj

    You totally solved my confusion, I as looking for the same answer, well I think vape couldn't harm that much as there are different flavors used it wouldn't harm as much as smoking does, well keep on sharing such Articles which makes others aware or new things I really appreciate

  • Jason Kubb

    Nice Article. I am always trying to find more information on this STILL hot topic.

  • Ruth Taylor

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  • xooxu

    Are there certain flavors that are less or more likely to contain DA/AP? I'd imagine any popcorn/caramel flavors would most likely have it, but the article also said that it's added to fruity flavors. If manufacturers don't have to list ingredients, is there anyway for the consumer to phase it out of their vaping with any certainty? Would flavorless be the only riskless option?

  • JostechVape

    Should be careful about these chemicals. There should be some good regulation to ban imports and manufacturing of e liquids that contain such chemicals.