What people call “vape smoke” is technically an aerosol, not smoke. Unlike cigarette smoke, which comes from burning tobacco at temperatures above 600°C, a vape heats a liquid at lower temperatures to produce a cloud of tiny suspended particles and droplets. That distinction matters because the chemical makeup of the two is quite different, but “not smoke” does not mean harmless. The aerosol contains nicotine, cancer-causing chemicals, heavy metals, and ultrafine particles that reach deep into the lungs.
How Vape Aerosol Differs From Smoke
Traditional cigarette smoke is a product of combustion. Burning tobacco generates thousands of chemicals, including tar, carbon monoxide, and dozens of known carcinogens. A vape skips combustion entirely. Instead, a battery-powered heating coil warms a liquid (called e-liquid or vape juice) until it turns into an inhalable mist of fine droplets.
Because there’s no burning, vape aerosol doesn’t contain tar or carbon monoxide. That’s the basis for claims that vaping is “safer” than smoking. But heating still triggers chemical reactions that create harmful byproducts, and the aerosol carries substances that cigarettes don’t, including certain metals and flavoring chemicals. The cloud you see isn’t water vapor. It’s a suspension of liquid particles containing the same base ingredients as the e-liquid, plus new compounds formed by heat.
What’s Actually in the Cloud
The base of most e-liquids is vegetable glycerin and propylene glycol, two compounds generally recognized as safe for ingestion but far less studied for inhalation. When heated, these carrier liquids form the visible cloud. Mixed into them are nicotine (in most products), flavorings, and various additives.
Heating transforms some of those ingredients into more dangerous compounds. Formaldehyde and acetaldehyde, both classified as carcinogens, are generated when the liquid reaches higher temperatures. Acrolein, a chemical also used as a weed killer, forms as well and can cause irreversible lung damage. These aren’t trace curiosities. They’re consistently detected across a wide range of devices and e-liquid formulations.
Heavy Metals From Heating Coils
One hazard unique to vaping comes from the device itself. The metal heating coil that vaporizes the liquid leaches metals directly into the aerosol you inhale. A study from Johns Hopkins found that lead, chromium, nickel, and manganese were all present at concerning levels in aerosol samples. The median lead concentration in the aerosol was more than 25 times greater than in the liquid before it was heated, and almost 50 percent of aerosol samples had lead concentrations above limits set by the Environmental Protection Agency. Nickel, chromium, and manganese concentrations approached or exceeded safe limits as well.
The coils are typically made from nickel and chromium alloys, making them the obvious source of contamination. Arsenic was also detected in samples from about 1 in 5 of the vapers studied. Every time you take a puff, liquid passes over that coil, picks up metal particles, and carries them into your lungs.
Flavoring Chemicals and Heat
Flavored vapes introduce another layer of concern. Diacetyl, a buttery-tasting compound linked to a serious condition called “popcorn lung” (bronchiolitis obliterans), can be present as an added flavoring ingredient. But even when it’s not deliberately added, it can be created by the heating process itself.
The base liquids, vegetable glycerin and propylene glycol, generate measurable diacetyl when coil temperatures exceed roughly 300°C. Sugars added to sweeten e-liquids also produce diacetyl when heated, with emissions climbing alongside both sugar concentration and device power. Certain fruity and caramel-type flavor compounds with a specific chemical ring structure break down into diacetyl at temperatures as low as 250°C. In short, even a “diacetyl-free” e-liquid can produce the chemical once heat enters the equation.
Nicotine Levels Can Be Extreme
Most vape liquids contain nicotine, and the concentrations have escalated dramatically. A decade ago, a typical vape cartridge contained roughly the same amount of nicotine as one pack of cigarettes (20 cigarettes). Today, popular disposable vapes can contain the nicotine equivalent of three cartons, or about 600 cigarettes, in a single device. A standard 5% nicotine pod delivers approximately 50 milligrams of nicotine per milliliter of liquid.
This matters because nicotine is powerfully addictive and poses specific risks for younger users, interfering with brain development that continues into the mid-20s. The high concentrations in modern devices make it easy to consume far more nicotine per session than a cigarette would deliver, often without realizing it.
What the Aerosol Does Inside Your Lungs
Your lungs are lined with a thin layer of fluid called surfactant that keeps the air sacs open and flexible. Research from the American Physiological Society has shown that e-cigarette aerosol impairs surfactant function, specifically by interacting with certain fats in the surfactant layer and making it less effective at keeping air sacs from collapsing. Over time, this could contribute to breathing difficulties and reduced lung function.
The ultrafine particles in vape aerosol are small enough to penetrate the deepest regions of the lungs, where gas exchange happens. Once there, they deposit metals, flavorings, and other chemicals directly onto delicate tissue. This is part of why vaping has been associated with EVALI (e-cigarette or vaping product use-associated lung injury), a condition that caused over 2,800 hospitalizations and 68 deaths in the United States by early 2020. EVALI can cause symptoms resembling pneumonia: coughing, chest pain, shortness of breath, and fever.
Secondhand Exposure
The aerosol you see drifting from a vape doesn’t vanish. It deposits nicotine, ultrafine particles, and volatile organic compounds onto surfaces and into the air. Bystanders in the same room are exposed to measurable levels of these substances. The particle concentrations are generally lower than those from secondhand cigarette smoke, but they’re not zero, and the long-term effects of chronic low-level exposure to aerosolized metals and flavorings remain poorly understood.
Indoor vaping leaves nicotine residue on furniture, walls, and fabrics, similar to thirdhand smoke from cigarettes. In enclosed spaces like cars or small rooms, aerosol concentrations rise quickly.