What are in vapes?

The liquid filling for electronic cigarettes (whether nicotine-based or cannabis-based) produces a complex chemical aerosol mixture when heated, which is definitely not the "harmless steam" that merchants often claim. Its components can be mainly classified into the following categories:

Base Solvents (Carriers)
These are the main components of the e-liquid, used to dissolve other substances and produce visible "smoke":

Propylene Glycol (PG) and Vegetable Glycerin (VG): These are the bases for the majority of e-liquids. PG provides a "throat hit" similar to traditional smoking, while VG produces a denser smoke.

Water: Some products may add a small amount of distilled water to adjust the consistency.

⚡ Active Components
The core active ingredients of electronic cigarettes vary depending on the product type:

Nicotine: In nicotine-based e-cigarettes, nicotine is the main addictive substance. Its concentration range is wide, from "no nicotine" to extremely high concentrations (such as 60mg/mL nicotine salt).

Cannabinoids: In cannabis-based e-cigarettes, the active ingredients are usually Tetrahydrocannabinol (THC) or Cannabidiol (CBD). Some hemp-derived products also contain Δ8-THC and other alternative cannabinoids, with concentrations often exceeding 95%.

Flavoring Agents and Additives
Components that give e-cigarettes various flavors, but their safety under inhalation routes is questionable:

Food-grade flavoring: Although many flavoring agents are approved for use in food, their safety for inhalation has not been verified. For example, some flavoring agents contain diacetyl (Diacetyl), which is associated with the serious lung disease "popcorn lung" (obstructive bronchiolitis).

Sweeteners: Some e-liquids may contain artificial sweeteners such as sucralose (Sucralose).

Other Additives: Unregulated or unregulated products may contain various unlisted additives, such as vitamin E acetate (see below) for thickening.

Harmful By-products Generated During Heating
This is the key to the risks of electronic cigarettes. When solvents and additives are heated and vaporized, chemical decomposition occurs, generating new toxic substances:

Carcinogenic Aldehydes: Propylene Glycol and Glycerin decompose at high temperatures to produce formaldehyde (Formaldehyde) and acetaldehyde (Acetaldehyde). Additionally, acrolein (Acrolein), a stimulant also found in herbicides, may be generated.

Other Toxic Carbonyl Compounds: Studies have also detected glyoxal (Glyoxal) and 4-methylpentanal (4-Methylpentanal) substances.

☠️ Pollutants and Illegal Additives
These substances should not be present in the product, but they are frequently seen in the unregulated or illegal market:

Metal Particles: The heating coils of electronic cigarettes (usually containing metals such as nickel, chromium, and iron) may release tiny metal particles at high temperatures, which are inhaled along with the aerosol. Studies have detected chromium (Cr), nickel (Ni), iron (Fe), lead (Pb), and zinc (Zn) particles in the aerosol of electronic cigarettes. Notably, a 2025 study found that even FDA-authorized devices (such as Vuse Alto) contained these metal particles, with certain metals (such as lead) at concentrations even higher than traditional cigarette smoke.

Vitamin E Acetate (VEA): This was the culprit behind the fatal lung injury (EVALI) outbreak in the United States in 2019-2020. The investigation found that the vast majority of cases were related to the use of illegal e-cigarettes containing THC, and 64% of the involved e-liquids tested positive for VEA, which was illegally used as a thickener. Inhalation of VEA can cause severe damage to the lungs.

Pesticides and other pollutants: The testing of illegal cannabis e-cigarette cartridges also revealed pesticide residues. Unregulated products may also contain extremely dangerous substances such as synthetic opioids (such as noroxinone) and other harmful substances.

Summary
The aerosol of e-cigarettes is a complex chemical mixture composed of basic solvents, active ingredients (nicotine or cannabinoids), flavoring agents, as well as toxic by-products generated by heating decomposition and pollutants from the device or illegally added substances (such as heavy metals, vitamin E acetate). The specific components and risk levels vary greatly depending on the product type (nicotine vs. cannabis), source (legal vs. illegal), and device power.