Vaping delivers nicotine through a heated aerosol that contains far more than flavored water vapor. It raises your heart rate by about 5 beats per minute within minutes, stiffens your arteries, triggers inflammation in your lungs, and floods a developing brain with enough nicotine to reshape its reward circuitry. About 7% of U.S. adults vaped in 2024, with the highest rate (nearly 15%) among 18- to 24-year-olds.
What You’re Actually Inhaling
E-cigarettes heat a liquid made of propylene glycol, vegetable glycerin, nicotine, and flavorings. The heating process doesn’t just vaporize these ingredients. It transforms them. When propylene glycol and glycerin hit the coil (which can reach over 300°C), they break down into toxic byproducts: formaldehyde, acetaldehyde, and acrolein. Over 150 puffs, a single e-cigarette can release up to 56 milligrams of formaldehyde and nearly 42 milligrams of acrolein. For comparison, acrolein levels in e-cigarette aerosol range from 0.17 to 3.70 micrograms per session, while a traditional cigarette produces 4.5 to 8.3 micrograms. Lower than cigarettes, but not zero, and not harmless.
The metal heating coil itself is another source of contamination. As it heats and cools thousands of times, it leaches aluminum, lead, chromium, and nickel into the aerosol. Higher-resistance coils (above-ohm devices) tend to produce finer particles with higher concentrations of these heavy metals. You inhale those metal particles directly into your lungs, where they generate oxidative stress in the cells lining your airways.
What Happens Inside Your Lungs
Your lungs are lined with delicate cells designed to exchange oxygen and carbon dioxide across a thin membrane. Vaping damages both sides of that membrane: the cells facing the air and the blood vessel cells behind them. When both layers are compromised, fluid leaks into the air sacs, immune cells rush in, and the lungs release a cascade of inflammatory and cell-killing signals. This is the basic mechanism behind acute lung injury from vaping.
Even the base ingredients, propylene glycol and glycerin, appear to alter how your lung immune cells behave. One theory is that chronic exposure to these substances puts immune cells in a heightened state, so that when any additional irritant enters the lungs, the immune response overreacts and triggers massive inflammation. This helps explain why some vapers develop serious lung problems seemingly out of proportion to what they inhaled.
Certain flavorings carry their own risks. Diacetyl, added to some e-liquids for a buttery taste, directly damages the lining of the small airways and triggers disorganized scar tissue formation. This condition, called bronchiolitis obliterans (sometimes known as “popcorn lung”), permanently narrows the airways and makes it harder to breathe.
EVALI: The Severe Form
In 2019, a wave of severe vaping-related lung injuries drew national attention. The CDC linked the outbreak to vitamin E acetate, an oily additive found in some THC-containing vape products. Vitamin E acetate is safe to swallow as a supplement or rub on your skin, but when inhaled, it interferes with normal lung function. Testing of fluid washed from the lungs of 51 patients with this condition found vitamin E acetate in 48 of them, and in none of the healthy comparison group. The mechanism likely involves either direct toxicity to lung cells or an inability of immune cells to break down the large molecule, leading to cell death and runaway inflammation.
How Vaping Affects Your Heart and Blood Vessels
A 2024 meta-analysis in the European Heart Journal Open measured what happens to your cardiovascular system during and after a vaping session. Compared to inhaling nicotine-free vapor, nicotine-containing e-cigarettes immediately increased arterial stiffness (measured by pulse wave velocity), raised diastolic blood pressure by nearly 5 points, and boosted heart rate by about 5 beats per minute. Thirty minutes later, blood pressure returned closer to baseline, but heart rate remained elevated, still running about 7 beats per minute higher.
Arterial stiffness is a particularly telling marker. Stiff arteries force the heart to work harder and are a well-established predictor of cardiovascular disease over time. The fact that a single vaping session measurably stiffens arteries suggests that repeated daily use keeps blood vessels under chronic mechanical stress.
Effects on the Adolescent Brain
Nicotine is the primary addictive substance in most vapes, and modern devices deliver it efficiently. The adolescent brain is uniquely vulnerable because it’s still wiring itself, particularly in the regions responsible for decision-making, attention, and impulse control. Nicotine hijacks this process in several specific ways.
In adolescents, nicotine triggers a larger release of dopamine in the brain’s reward center than it does in adults. The dopamine-producing neurons are also more susceptible to nicotine-driven rewiring during this period. This creates a stronger, faster path to addiction. But the effects go beyond craving. Nicotine exposure during adolescence actually activates the brain’s immune cells in a way it doesn’t in adults. These activated immune cells then prune connections between neurons in the reward and emotional processing areas of the brain, which in animal studies led to increased vulnerability to other addictive substances later in life.
The cognitive toll is measurable. Animal studies show that nicotine exposure during adolescence increases impulsive behavior and decreases attention in adulthood, effects that don’t appear when the same exposure happens in adult animals. Teen smokers show reduced working memory and attentional performance during withdrawal. At the cellular level, adolescent nicotine exposure weakens the brain’s ability to filter out irrelevant signals by disrupting communication between neurons in the prefrontal cortex. These changes persist into adulthood even after nicotine use stops.
What Bystanders Are Exposed To
Exhaled vape aerosol does release nicotine into the surrounding air, though at much lower levels than cigarette smoke. Measured air concentrations of nicotine from e-cigarettes ranged from 0.82 to 6.23 micrograms per cubic meter in controlled studies, roughly one-tenth the concentration produced by tobacco cigarettes (about 31.6 micrograms per cubic meter). The aerosol also contains trace amounts of carbonyl compounds, nitrosamines, and heavy metal particles, though specific air concentrations of metals haven’t been well quantified.
This means secondhand vape exposure is not equivalent to secondhand cigarette smoke, but it isn’t clean air either. In enclosed spaces with poor ventilation, nicotine and fine particulate matter accumulate and are breathed in by everyone present.
Vaping Compared to Smoking
Vaping generally produces lower levels of the toxic compounds found in cigarette smoke. Acrolein levels, for example, can be 2 to 50 times lower in e-cigarette aerosol than in cigarette smoke, depending on the device and how it’s used. The absence of combustion means vapers aren’t inhaling tar or carbon monoxide, two of the most damaging components of cigarette smoke.
But “less toxic than cigarettes” is a low bar, and it doesn’t mean safe. Vaping introduces its own set of exposures: ultrafine metal particles from heating coils, flavoring chemicals never tested for inhalation safety, and thermal breakdown products from propylene glycol and glycerin that vary wildly depending on coil temperature, wattage, and puffing patterns. A vaper using a high-powered device at high temperatures can generate formaldehyde levels that approach or even exceed those in cigarette smoke. The risks are not fixed; they shift with how the device is used.