The last few months have brought a tremendous amount of controversy when it comes to what ingredients are used in vaping. This was brought on in part by a period during which, after years of nicotine vaping products being on the market with few reported problems, new cases of lung illness spiked in a group of patients who said they’d been vaping.
That crisis has largely passed, and it turns out that it likely wasn’t related to nicotine e-liquids in the first place. We’ll get into that, but first let’s review exactly what does go into the liquid used to fill an e-cigarette.
First, let’s start with that term, “e-liquid.” It’s what most experienced vapers prefer to call the fluid used to fill their vapes, or electronic cigarettes. As vaping has advanced many have chosen to move away from the “e-cigarette” terminology, primarily because longtime vapers feel it’s important to recognize that there’s a significant difference between vaping and cigarette smoking. Because they’re using electronic devices the term e-liquid has stuck around, however.
You may also hear nicotine replacement vaping liquids referred to as “e-juice” or “vape juice.” Although these terms are popular, they’re problematic in that anti-vaping activists have argued that the term “juice” implies a risk-free product and that juice appeals primarily to children and not adults. For that reason, we’re going to refer mostly to e-liquid going forward.
There are a handful of vaped substances that e-liquid is not, however. Terms like dabs, wax, oil, dab carts, and other variants like this do not refer to e-liquid vapor products. These instead reference oil-based products that contain concentrated marijuana, which is never present in traditional vapor products. Inhaling oil may pose a serious risk, and reputable nicotine e-liquids do not contain oil.
PG and VG: A Base
Okay, so what is e-liquid? You may have heard people describe their clouds as “just water vapor,” but that’s not exactly true. The majority of any e-liquid will consist of propylene glycol (PG) and vegetable glycerin (VG), the “base” ingredients.
PG is a thin, odorless, colorless organic compound. It’s used in foods and other household products including coffee drinks, ice cream, and sodas, along with medical inhalers distributed by the pharmaceutical industry. It’s a humectant, meaning it quickly absorbs moisture, and along with nicotine is responsible for creating the “throat hit” effect with which cigarette smokers will be familiar.
If you’ve ever heard the argument that “vape juice is made of antifreeze,” it’s PG that’s to blame. Because of its non-toxic nature, PG is often added to automotive coolant to decrease its toxicity and lessen the risk to animals that might drink from a puddle under a car with a leaky radiator.
VG is thicker and slightly sweet in taste. Food-grade VG is typically derived from palm or soy oil using a process that splits the sugar alcohols of the plant and extracts the fatty oils. Along with e-liquid, VG is found in foods where it acts as both a sweetener and a moisture preservative, acting to prevent ice crystals from forming in frozen yogurt or toothpaste from drying out in its tube, for example. VG is also a component of pharmaceuticals like heart medications and cough suppressants.
For vaping purposes, VG is responsible for creating the visible “clouds” of vapor exhaled by a vaper. Most open system devices will use liquids with a high VG concentration, while closed-system devices like those that use disposable pods will have a higher PG percentage due to the thickness of VG inhibiting it from penetrating the tiny, low-powered coils these devices employ.
Flavor and Nicotine
While the PG/VG base will typically comprise 80-90 percent of an e-liquid, the remainder of the product consists largely of food-grade artificial flavoring also known as vape juice flavors.
Most of these flavors are suspended in a PG base of their own, though some VG-based variations exist.
When we say “food-grade” flavoring, it’s important to keep in mind that these products are safe to eat. That’s not necessarily a guarantee that they’re safe to heat into a fine mist and inhale into the lungs. Research into the various flavor extracts used in e-liquids has only been underway for a handful of years, but as the vaping community learns more about the chemical reactions these flavors undergo when vaped, recipes for e-liquid are evolving.
One of the first troubling chemicals to emerge from vaping research was diacetyl, a substance that creates a buttery flavor and was once popular in bakery-inspired vapes. Diacetyl is used as a foodstuff for creating the fake “butter” flavor added to microwave popcorn, and has been linked to a lung illness known as “popcorn lung,” though only one person in the US has so far been diagnosed with this disease who didn’t work in a factory processing massive quantities of the substance. Diacetyl is also found in cigarette smoke at considerably higher levels than in vapor products, but nonetheless responsible e-liquid manufacturers have largely moved away from it as an ingredient in recent years.
Concerns have also emerged surrounding some of the ingredients that go into creating cinnamon, vanilla, and menthol flavors, though these findings are more recent and alternative extracts are still being explored. Vapers concerned about problem flavors may want to limit their exposure to liquids with heavy doses of these flavors.
The final ingredient in e-liquid is nicotine extract. Not all e-liquid contains nicotine – many ex-smokers gradually reduce their nicotine consumption until it reaches zero, though some choose to continue vaping for relaxation as a hobby. The majority of e-liquids sold, however, will have at least some concentration of nicotine.
There are two forms of nicotine extract: nicotine salts and traditional, or “freebase” nicotine. Salt-based nicotine is a relatively recent innovation and has both a much smoother feel in the throat and quicker uptake rate by the body. For this reason, nicotine salt users can consume much more nicotine than traditional users. Concentrations in open system devices generally top out around 18 mg/ml, though 3-6 mg is a much more common dose. Salt-based pod systems, meanwhile, can have as much as 50 mg of nicotine in a single ml of liquid.
What E-Liquid Isn’t
Okay, we’ve covered what e-liquid is: organic PG and VG base liquids, food-grade flavoring, and often (but not always) nicotine extract. But it’s just as important to know what e-liquid is not.
E-liquids used for personal vaporizers, most importantly, do not contain oil. Oils contain fatty particles known as lipids, these can seriously damage lungs when heated and inhaled, which is why e-liquids designed for nicotine vaping will not use oils as a base liquid or flavoring. This sets up an important distinction between nicotine and other types of vaping.
As laws across the country have relaxed as relates to the consumption of cannabis, more and more people are turning to vaping liquid marijuana products. But because cannabinoids, the essential compounds found in the cannabis plant, are oil-soluble, they must be suspended in an oil solution rather than in water-soluble bases.
Why is this important? In nearly every incidence of the once-mysterious cases of vaping-related lung illnesses that swept the country over the summer, victims admitted to having used marijuana vapor products, either alone or in conjunction with nicotine vapes. The connection to “vape lung” and marijuana is so strong that the federal Centers for Disease Control and Prevention say they’ve identified vitamin E oil as the likely culprit. The oil was used as a filler in a host of black-market cannabis vapes and, unsurprisingly to a nicotine vaping community well-versed in the dangers of inhaling oil, sickened thousands of people.
So, what’s the takeaway here? We’re still learning about the science of vaping, and thousands of e-liquid manufacturers are working with scientists across the globe to make vaping as safe as possible. Quality nicotine liquids don’t contain the oils that health officials have tied to last year’s lung infection outbreak. Still, remember that while we believe vaping is a much-preferred alternative to smoking, it’s absolutely not a risk-free activity. If you have concerns about what’s in your e-liquid, ask what goes into your favorite flavor – if you want to avoid certain ingredients, you have plenty of other choices. At least for now.