Vapes contain more than most people realize. Beyond nicotine or cannabis, the liquid inside an e-cigarette is a mix of carrier solvents, flavoring chemicals, and, depending on the product, metals leached from the heating coil and toxic byproducts created by heat itself. Illicit or unregulated products can contain far more dangerous substances, including synthetic drugs and cutting agents linked to fatal lung injuries.
Nicotine: The Primary Drug in Most Vapes
Nicotine is the active drug in the vast majority of commercially sold vapes. It comes in two forms. Freebase nicotine is the older formulation, typically found in larger, refillable devices at concentrations around 3 to 20 mg/mL. Nicotine salt, popularized by pod-style devices, uses a modified form of nicotine that feels smoother at higher concentrations, commonly 20 to 50 mg/mL. A 40 mg/mL nicotine salt formulation delivers nicotine to the bloodstream at levels comparable to a traditional cigarette.
Despite those high concentrations, vapes deliver nicotine differently than cigarettes. In a head-to-head comparison, a single vaping session produced peak blood nicotine levels of about 6 ng/mL, compared to roughly 20 ng/mL from one cigarette. The nicotine also takes longer to hit: about 6.5 minutes to peak from a vape versus 2.7 minutes from a cigarette. This slower delivery is one reason many vapers take more frequent puffs, which can increase total exposure over time.
THC, CBD, and Cannabis Extracts
Cannabis vape cartridges contain concentrated THC oil, CBD oil, or a blend of both. Legal dispensary cartridges typically list THC potency between 70% and 90%, though actual concentrations vary by brand and batch. CBD vape liquids are sold more widely, but testing reveals serious inconsistencies: labeled CBD amounts frequently don’t match what’s actually inside, with some products off by more than 200%. Many CBD e-liquids also contain detectable levels of THC, even when not listed on the label.
The bigger concern with cannabis vapes is what’s added to the oil. During the 2019 EVALI outbreak (a wave of severe lung injuries tied to vaping), vitamin E acetate emerged as a key culprit. This oily additive was used as a cheap thickener in illicit THC cartridges. Testing of products submitted by lung injury patients in Minnesota found vitamin E acetate in cartridges from 11 of 12 affected users. Products seized by law enforcement in 2018, before the outbreak, contained no vitamin E acetate. By 2019, every seized THC product tested positive for it, suggesting it was introduced as a filler to stretch product volume and increase profit.
Carrier Solvents: PG and VG
Every nicotine or flavored e-liquid uses a base of two carrier liquids: propylene glycol (PG) and vegetable glycerin (VG). These are the substances that actually produce the visible vapor. PG is thinner and produces a stronger throat sensation. VG is thicker and creates denser clouds. Common ratios range from 70/30 PG/VG to 100% VG, with 50/50 being a popular middle ground. Higher PG concentrations also appear to increase how much nicotine reaches your bloodstream per puff.
Both PG and VG are considered safe to eat, which is why they’re approved food additives. Inhaling them repeatedly is a different question, and one without a clear long-term answer yet. What is clear is that heating these solvents creates toxic byproducts, which brings us to a category of chemicals most vapers never think about.
Toxic Byproducts From Heating
When PG and VG are heated by the coil inside a vape, they break down into smaller, harmful compounds. The temperature of the coil determines which ones form and how much. Formaldehyde and acetaldehyde, both known carcinogens, begin appearing at coil temperatures around 215°C (419°F). At 270°C (518°F), a third compound called acrolein, a potent lung irritant, starts forming from VG.
The amounts increase steeply with temperature. Formaldehyde production at 318°C was roughly 70 times higher than at 215°C. This matters because high-wattage devices and dry coils (when the wick runs low on liquid) can easily push temperatures into that range. Taking long, deep draws on a device running hot significantly increases exposure to these compounds.
Flavoring Chemicals
Flavored vapes get their taste from food-grade flavoring compounds, but “food-grade” refers to eating, not inhaling. In a study of 51 flavored e-cigarettes, a chemical called diacetyl was detected in 39 of them. Diacetyl is the same compound that caused “popcorn lung” (bronchiolitis obliterans) in factory workers who inhaled butter-flavoring fumes in the early 2000s. That condition involves irreversible scarring of the smallest airways in the lungs, and in severe cases the only option is a transplant.
Two related chemicals, 2,3-pentanedione (a diacetyl substitute) and acetoin, were also found in 23 and 46 of the 51 products, respectively. These compounds aren’t limited to buttery or caramel flavors. They were present across fruit, candy, and cocktail-flavored products, many of which appeal to younger users. While the doses per puff are smaller than what factory workers inhaled, the long-term effects of daily low-level inhalation remain a serious concern.
Heavy Metals From Heating Coils
The metal coil that heats the liquid also contaminates it. As e-liquid passes over the coil, it picks up trace metals that then get carried into the aerosol you inhale. Testing of vape aerosols found measurable levels of chromium, nickel, lead, manganese, and zinc. The concentrations aren’t trivial: close to half or more of the aerosol samples for chromium, manganese, nickel, and lead exceeded established health-based exposure limits.
The source is clearly the coil itself. Liquid tested straight from the manufacturer’s bottle had minimal metal content. Liquid that had sat in the device’s tank, in contact with the coil, showed dramatically higher levels. For lead, median concentrations jumped from 0.5 µg/kg in fresh liquid to over 40 µg/kg in the tank. Nickel went from about 2 µg/kg to 233 µg/kg. These metals accumulate in the body over time, and chronic exposure to lead and nickel is linked to cardiovascular damage, kidney problems, and cancer.
Illicit and Counterfeit Vape Additives
Unregulated vapes, purchased from informal sellers, social media, or the black market, can contain substances far beyond nicotine or cannabis. DEA investigators documented a fatal overdose case in San Diego where a single vape pen contained fentanyl, carfentanil (a fentanyl analog roughly 100 times more potent), two other fentanyl-related compounds, a sedative, and a synthetic cannabinoid called XLR-11. It was the first case of its kind flagged by the San Diego County Medical Examiner.
Synthetic cannabinoids (sometimes called “spice” or “K2”) have also been found in vape cartridges sold as regular THC or even nicotine products. These lab-made compounds bind to the same brain receptors as THC but with unpredictable and sometimes dangerous intensity, causing seizures, psychosis, and cardiac events. The risk is almost entirely concentrated in products bought outside legal, regulated channels.
What’s Actually Regulated
As of late 2025, only 39 e-cigarette products have received marketing authorization from the FDA. These are the only vape products that can legally be sold in the United States. Every authorized product is tobacco-flavored; no fruit, candy, mint, or menthol-flavored vapes have received FDA approval. The vast number of flavored products still being sold exist in a regulatory gray zone, with many operating without authorization while enforcement efforts continue.
This gap between what’s legal and what’s available means that most vapes on the market have not undergone the FDA’s full review of their ingredients, emissions, or health impact. The 39 authorized products represent a tiny fraction of the thousands of e-liquids and devices currently in circulation.