A disposable vape contains a small lithium battery, a heating coil, a cotton wick, and a reservoir of e-liquid. The e-liquid itself is a mixture of propylene glycol, vegetable glycerin, nicotine (usually in salt form), flavoring chemicals, and often synthetic cooling agents. But that’s just what goes in by design. When the liquid is heated, additional compounds form in the aerosol you actually inhale, including trace metals from the coil and reactive chemicals created by heat.
The Liquid Base: Propylene Glycol and Vegetable Glycerin
Every e-liquid starts with two carrier solvents: propylene glycol (PG) and vegetable glycerin (VG). These make up the bulk of what’s in the reservoir. PG is a thin, odorless liquid used widely in food and pharmaceuticals. VG is thicker and slightly sweet, derived from plant oils. Together, they dissolve the nicotine and flavorings and produce the visible vapor cloud when heated.
The ratio of PG to VG affects the experience. Higher PG concentrations deliver a stronger “throat hit,” that sharp sensation at the back of the throat that mimics smoking. Higher VG produces a smoother, denser cloud. Common commercial ratios range from 70/30 PG/VG down to pure VG. Most disposable vapes lean toward higher VG or balanced blends, since they’re designed for smoother draws at high nicotine levels.
Nicotine Salts vs. Freebase Nicotine
Nearly all disposable vapes use nicotine salts rather than traditional freebase nicotine. The difference matters. Freebase nicotine is alkaline, which makes it harsh on the throat at high concentrations. That’s why freebase e-liquids typically top out around 3 to 12 mg/mL. Nicotine salts solve this by combining nicotine with an organic acid, most commonly benzoic acid. This lowers the pH of the liquid, producing a much smoother inhale even at 25 or 50 mg/mL.
That smoothness is part of what makes disposable vapes so efficient at delivering nicotine. A single disposable can contain as much nicotine as one to two packs of cigarettes, depending on the device’s liquid volume and concentration. The salt formulation lets users inhale high doses comfortably, which also makes these devices more habit-forming than many people expect. In the United States, there is currently no federal cap on the nicotine concentration allowed in e-liquids.
Flavoring Chemicals
The flavors in disposable vapes come from a complex mix of food-grade flavoring compounds. These are chemicals originally developed for use in food products, where they’re ingested and processed by the digestive system. Inhaling them into the lungs is a fundamentally different exposure route, and the long-term effects of breathing many of these compounds are not well understood.
Dozens of individual flavoring chemicals may appear in a single e-liquid. These vary widely by flavor profile. Fruit flavors rely on different chemical combinations than dessert or tobacco flavors. Some compounds that have raised concern over the years include diacetyl (linked to serious lung disease in factory workers who inhaled it), acetoin, and acetyl propionyl. While some manufacturers have moved away from diacetyl specifically, the sheer number of flavoring agents in use makes comprehensive safety testing difficult.
Synthetic Cooling Agents
If you’ve ever used a vape labeled “ice” or “menthol blast,” you’ve inhaled synthetic cooling agents. The most common are compounds known as WS-23 and WS-3, which trigger cold-sensing receptors in the mouth and throat without any actual menthol taste. E-cigarette manufacturers use these to create intense cooling sensations. Research on the effects of repeatedly inhaling these chemicals is still limited, though early cell studies have found they can increase oxidative stress in lung tissue.
What the Heating Process Creates
The e-liquid ingredients are only part of the picture. When propylene glycol and vegetable glycerin are heated to the temperatures typical of vaping devices (roughly 150°C to 350°C), they break down and form new compounds that weren’t in the original liquid. The most concerning of these are a group of reactive chemicals called carbonyl compounds: formaldehyde, acetaldehyde, and acrolein.
Formaldehyde is a known carcinogen. Acetaldehyde is classified as a probable carcinogen. Acrolein is a potent irritant that damages lung tissue. All three have been detected in e-cigarette aerosol at levels that have raised concern about long-term health effects. The amounts produced depend heavily on temperature. Glycerin, in particular, begins generating significant formaldehyde at temperatures above 215°C and produces acrolein above 270°C. At 318°C, one milligram of glycerin generates roughly 21 micrograms of formaldehyde, about ten times more than propylene glycol at the same temperature.
These byproducts form in greater quantities when the coil runs hotter or the wick dries out, a situation called a “dry hit.” Disposable vapes offer no temperature control, so users have little ability to minimize this exposure.
Metals in the Aerosol
The heating coil inside a disposable vape is typically made of stainless steel, nickel, or a mesh alloy, wrapped around a small cotton wick. As the coil heats up repeatedly, tiny amounts of metal leach into the aerosol. CDC-funded research on pod-type e-cigarettes detected lead, nickel, chromium, copper, zinc, and tin in the aerosol, with lead reaching up to 463 nanograms per 10 puffs and nickel up to 373 nanograms per 10 puffs.
These are small amounts per puff, but they accumulate with frequent use. There is no safe threshold for lead inhalation, and chronic low-level exposure to nickel and chromium is associated with respiratory damage. Disposable vapes, which are manufactured cheaply and lack quality control compared to reusable devices, may have inconsistent coil quality that worsens metal leaching.
Microplastics From the Device Itself
A less obvious contaminant comes from the plastic body of the device. Research published in the Journal of Hazardous Materials found microplastics in e-liquids at counts of 4 to 14 particles per 10 mL. The most common polymer detected was polypropylene, making up 40 to 70 percent of all particles, which pointed directly to the plastic components of the device (mouthpieces, reservoirs, and cartridges) as the source.
Heat, friction, and prolonged contact between the liquid and plastic housing can cause degradation, releasing tiny plastic fragments into the liquid. These microplastics can then be carried into the lungs during inhalation. The health consequences of inhaling microplastics are an active area of concern, but the presence of plastic particles in what users assume is a clean vapor is notable on its own.
The Hardware Inside
Physically, a disposable vape is a simple device. A small lithium-ion battery (typically 400 to 750 mAh) powers a heating coil. The coil sits inside a reservoir holding anywhere from 2 to 15 mL of e-liquid depending on the device. A cotton wick draws liquid from the reservoir to the coil. An airflow sensor or a simple button activates the battery when you inhale. The whole assembly is sealed in a plastic casing with a plastic mouthpiece.
Because these devices are designed for single use, none of these components are meant to be serviced, replaced, or recycled by the consumer. The EPA classifies e-cigarettes as hazardous waste due to both the lithium battery and the residual nicotine inside. Lithium batteries that end up in regular trash can be crushed during compaction and cause fires at waste facilities. Residual nicotine is toxic to aquatic organisms and can be absorbed through skin, posing a poisoning risk to sanitation workers. The recommended disposal method is to bring used devices to a household hazardous waste collection site rather than tossing them in the trash or recycling bin.