Recent research on vaping e-cigarette flavors from the source
Recent research reveals that certain e-cigarette flavors could pose risks to people who vape. But with so much sensational coverage in the media, it’s hard to know what the research really says, and how it affects people who vape.
VV corresponded with Yale researcher Hanno Erythropel, a chemical engineer and one of the researchers, to determine what the research means for people who vape.
Additives entering the body via the lungs
First, I noted that the focus of this study is aldehyde flavorants specifically, and how those react when used in the vaping liquids. In other words, this is not a study focusing on all vaping or all e cigarettes.
“Correct,” confirms Dr. Hanno. “This study was specifically on flavor aldehydes (there are 5 listed, but there are more out there). So correct, the results do not concern all e-liquids, but all that would contain such flavor aldehydes.”
The main thrust of the work was in part the intuitive study of how any sort of additive reacts in the body, but the other component is how the act of vaping as a routes of exposure impacts its delivery and effects.
“For example, food additives would get to the body through the stomach and colon, while e-liquid vapor reaches the lungs first,” clarifies Dr. Hanno. “Since compounds can have different effects depending on where they enter the body, things get more complicated. The question is not only what are we exposed to, but also through which route?”
Safe to eat—safe to vape?
Part of the issue here is that these compounds are “Generally Recognized As Safe” or GRAS—but only when eaten.
“By definition, GRAS status only refers to ingestion and application to the skin,” remarks Dr. Hanno. “GRAS does not cover inhalation toxicity.”
And while some consumers believe that “natural” flavors such as vanilla or cinnamon can’t be harmful in the body, this simply isn’t true.
“Think about this: the most poisonous compound known to humans is botox (botulinum toxin A), produced by a bacterium, and therefore a ‘natural compound,’” comments Dr. Hanno. “Unfortunately, the distinction between ‘natural compounds’ and ‘chemicals’ does not really work that well. All natural compounds are also ‘chemicals.’ Just because a compound is produced by an animal, plant, or bacterium does not mean it has to be safe for humans.”
Of course, humans have smelled vanilla and cinnamon for millennia without harm, so their ingredients are clearly not acutely toxic to humans.
“However, smelling a meal that has vanilla or cinnamon is different from actively inhaling it as part of an e-liquid deep into the lungs,” explains Dr. Hanno. “Plus, as we showed, there is actually a chemical transformation of these flavor aldehydes (such as vanillin or cinnamaldehyde) to new compounds. As a general rule, at a high enough concentration, almost all compounds can become toxic, whether ingested or inhaled. This is what Paracelsus meant with ‘the dose makes the poison’. But just to be clear: we are not suggesting that e-liquids with flavor aldehydes are poisonous per se. All we are saying here is that we don’t know what are ‘safe’ levels for inhalation.”
What’s in that pod?
In the research, the team aimed to show, “that acetals can form during regular storage conditions, that they can reach the e-cigarette user through the aerosol, that the acetals don’t break down to the flavor aldehyde and PG/VG upon contact to the water present in human cells, and that some of them are actually more irritating than their parent compounds (e.g., vanillin PG acetal was more irritating than vanillin in both assays),” states Dr. Hanno.
In the study, the researchers cited other work in the literature that found the presence of acetals in e-liquids that appear to be the result of mixing, because they were not among the original flavorants. In other words, just sitting on the shelf may be causing the ingredients of some e-cigarettes to change in unknown ways—but since this area is so under-regulated, that’s hard to determine.
“Acetals such as vanillin PG acetal have been reported previously in e-liquids, correct,” confirms Dr. Hanno. “However, since manufacturers in the US are not required to divulge their flavorant ingredients to the consumer (which you can see by common e-liquid labels: they only list PG, VG, nicotine, sometimes benzoic acid, and then ‘flavorings’), we technically don’t know if some of the acetals were added on purpose to the e-liquids.”
However, as Dr. Hanno points out, adding them would not be cost-effective. These acetals are typically more expensive than their parentcompounds and have a less intense smell. Vanillin PG acetal is more expensive to buy and smells less like vanilla than pure vanillin, for example—and that’s how we end up with e-cigarette flavors.
“And they would form inside the e-liquids anyway,” adds Dr. Hanno. “We thus concluded that the presence of acetals in e-liquids is very likely due to the reaction that is taking place between the flavor aldehydes and PG/VG rather than a deliberate addition of them by manufacturers. It is clear that these reactions can take place at room temperature, simply by mixing common e-liquid ingredients (such as the listed aldehydes, PG, and VG).”
The interaction with PG, not just the presence of the flavorant itself, is problematic for vapers.
“I would argue that it is the combination of both: the fact that they form within e-liquids, and that some of them show stronger effects than the molecules they were formed from,” Dr. Hanno says. “Basically, as the reaction takes place, the e-liquid becomes more irritating by an increase in vanillin PG acetal concentration, for example.”
Lasting in the body over time?
While the researchers did not look at persistence in the body, they did conduct tests that confirmed the acetal compounds are stable enough to cause an effect once they reach human airways.
One of the most interesting things about this research is that the real conclusion is that the risk is unknown.
“I think this is one of the things this study shows: we really don’t know much about any of this,” admits Dr. Hanno. “We’re mixing together ‘chemicals’ and inhaling them deep into our lungs without really understanding what they are, how they might interact with one another, how they might behave when they are heated up in an e-cigarette, and what their long-term effects are.”
One of the problems here is certainly time. Without long-term information about vaping these e-cigarette flavors and their effects, no one can be certain about risk, or even nail down what people should be researching. The CEO of Juul CEO has recently admitted that we don’t know the long term effects of using the company’s products—something Dr. Hanno’s work confirms.
It’s also problematic that as these liquids sit in storage, display cases, homes, or wherever else they may be, they could be changing—without any reliable way to know as a basic matter what’s in the pod over time.
“Correct, we are showing that the e-liquid composition will most likely change over time, at least in the case when flavor aldehydes are present inside the e-liquid,” states Dr. Hanno. “If one knew all ingredients to e-liquids and the containers, there might be a way to predict or actually monitor this, but currently, that is not information that is available.”
So, in addition to policing dates and watching whether you keep e-cigarette flavors around as a vaper—and engaging in the label reading we should probably all be doing anyway—it might be wise to stay wary.
“There is little knowledge about the long-term effects of regularly inhaling flavor molecules by e-cigarettes, as well as the other e-liquid constituents PG and VG,” confirms Dr. Hanno. “Also, just because e-liquids are sold commercially does not rule out the possibility that their chemical composition can change over time.”
In other words, Big Tobacco is probably still not looking out for us. And that’s another thing to remember: the risks from smoking conventional cigarettes are well-known, and far worse than those from vaping, as far as we know right now.