E-Liquid Ingredients Explained
Is e-liquid poison by the barrel? Should we be worried about what’s in e-liquids? Do we even know what’s in them? The treatment of vaping in the media may lead you to believe that e-liquid ingredients are a cause for concern, but in reality e-liquids are made from just a handful of ingredients: propylene glycol, vegetable glycerin, nicotine and various food-safe flavorings. Learning a little more about these ingredients – and the trace amounts of by-products from vaporization – is enough to allay in fears you may have, especially when placed into proper context alongside the 7,000-plus chemicals found in tobacco smoke.
Propylene glycol is one of the two main ingredients in e-liquid, and its use largely comes down to its ease of vaporization. Often known simply as PG (chemical name 1,2-propanediol), it’s used in a multitude of applications, including theatrical smoke machines, as a solvent in pharmaceuticals, sunscreen, shampoos, lotions, shaving cream and many other products, as an emulsifier in cosmetic creams, and as a humectant (to keep things moist), preservative and stabilizer in pet food, baked goods and food flavorings.
Its use in this wide range of consumer products comes down to the fact that it’s generally recognized as safe. Although information on inhalation is limited, irritation of the respiratory tract is a known effect, and this provides a “throat-hit” to e-liquids that enables them to mimic the sensation of inhaling smoke. Outside of vaping, there is limited evidence on human exposure by inhalation, but studies in rats, dogs and monkeys suggest that inhalation is very low in risk.
Vegetable glycerin (glycerol) is known as VG, with the chemical name 1,2,3-propanetriol, and is the other primary ingredient in e-liquid. Black Note, along with many other mixers, uses a 50/50 mixture of PG and VG. Like PG, VG has a wide range of uses, spanning pharmaceuticals (where it’s used in things like cough syrups and creams), cosmetics (as a moisture-retainer, solvent and lubricant), food (to retain moisture and sometimes as a sweetener), in tobacco (to retain moisture) and in many other applications. As with PG, VG is generally recognized as safe, but may cause respiratory irritation when inhaled. Again, VG is of low toxicity and animal experiments on inhalation have observed only minor effects.
Nicotine is the core addictive component of tobacco, and the reason most people use e-liquid. Its health risks are often overstated because it’s hard to separate nicotine’s effects from those of tobacco smoke. The evidence on nicotine when separated from tobacco smoke generally shows minimal risk, even in the primary area of concern, cardiovascular dangers (meaning risk for the heart and blood vessels). Even when larger risks due to nicotine are assumed, the benefit of switching from smoking drastically outweighs the risk from nicotine. Additionally, evidence shows that vapers consume much less nicotine than smokers, so any risk attributable to nicotine would be reduced for that reason alone.
Nicotine is indeed poisonous (although not as much as once thought), but – outside of drinking a whole bottle of strong e-liquid – serious risk from poisoning would only be a concern if you’re dealing with concentrated nicotine used for DIY mixing.
This is a big catch-all term for other flavors you may find in e-liquid. CASAA calls food flavorings “the great unknown” when it comes to e-cigarettes, and the reason is simple: we know they’re safe to eat or drink, but it’s not so certain for inhalation. A good example of this is diacetyl, a flavoring often used to impart a buttery taste, which is safe to ingest but is associated with adverse effects on lung function. However, after a study exposing the widespread use of diacetyl in e-liquid, many manufacturers have ceased including the ingredient.
A full list of common food flavorings is available (Table 2), but in many cases limited risk information is available for inhalation, and the specific chemicals used often aren’t listed by e-liquid mixers. However, flavorings such as vanillin (a vanilla flavor), linalool (gives a herbal flavor, like coriander), ethyl maltol (a sweet, bakery-like flavor), acetyl pyrazine (a graham cracker-like flavor) and malic acid (a sour, fruity flavor) are commonly used, and generally speaking most carry no known risks.
Mixers may use artificial or natural chemicals for flavoring, and in many ways the difference between the two is minimal. An artificial flavoring will be heavily based on a natural chemical, with some strategic changes possibly made along the way, so in many cases what you get is relatively similar. However, when it comes to capturing the true flavors – especially in a complex blend of tastes like tobacco – the advantage of using natural flavorings really shines through.
The simplifications made when replicating a natural flavor synthetically can rob the resulting taste of its depth and complexity. Bearing in mind that everything you taste ultimately comes down to its chemical properties, it’s obvious that messing around can have undesirable effects on the taste. This is why most tobacco e-liquids aren’t particularly realistic, and one of the reasons we believe that natural is better.
There may be trace components in some flavor concentrates, and there are also often tobacco-specific nitrosamines present in e-liquid as a result of the pharmaceutical-grade nicotine used. These nitrosamines are carcinogens, so the goal is always to minimize their content as much as possible – snus manufacturer Swedish Match has done a fantastic job of this, for example. The fact that most e-liquid mixers use pharmaceutical-grade nicotine suggests that these same chemicals would be present in nicotine patches and gums too, and that is indeed the case. The levels of nitrosamines are similar between the two, and you’re exposed to many, many times less from vaping (around 1,400 times less in some cases) than you are from smoking tobacco.
Other Chemicals in Vapor
Most of the other trace ingredients that are found in studies of e-cigarette chemistry are produced during the process of vaporization. An example is PG degrading into formaldehyde (and other carbonyls) during the process. Again, you’ll be exposed to many times more formaldehyde than you would from smoking, and the evidence to date seems to suggest the production only gets close to cigarette-like levels during a “dry puff,” where there isn’t enough e-liquid supplying the wick and thing overheat. If this happens, you’ll know about it.
You can learn more about the trace chemicals found in vapor through many different studies, but Igor Burstyn’s systematic review of the chemistry research is free and covers a lot of ground.
Knowing What’s in Your E-Liquid
This guide has given you a general indication of the sort of thing you’ll find in your e-juice, but as you can undoubtedly tell from the flavorings section, there is a lot of uncertainty involved. Here at Black Note, we don’t add any “characterizing flavors,” and aside from PG, VG and nicotine, all the flavors in your e-liquid are naturally-extracted from tobacco leaves. Additionally, our e-liquids are lab-tested, so you can see exacting what you’re getting in your juice. That said, with pretty much any e-liquid you can rest assured that any harmful components are only present in trace quantities, and vastly lower than you’d find in tobacco smoke.