When someone vapes, a battery heats a liquid (often called e-liquid or "juice") into an aerosol that is inhaled. Marketing frequently describes this as harmless vapour, but laboratory analyses show the aerosol commonly contains nicotine, ultrafine particles, flavoring compounds, and byproducts created by heating. Below is an overview of the body systems researchers are most concerned about.
In brief: Vaping is generally considered less harmful than smoking combustible cigarettes for adults who already smoke — but "less harmful" is not the same as "safe," and the long-term picture is still being studied.
1. The lungs and airways
The respiratory system has the most direct contact with vaping aerosol. Reported and studied effects include:
- Irritation and inflammation: Coughing, wheezing, chest tightness, and throat irritation are commonly reported by users.
- EVALI: In 2019–2020, health authorities documented an outbreak of "e-cigarette or vaping product use-associated lung injury." Many cases were linked to products containing THC and the additive vitamin E acetate, though investigations continued across product types.
- Reduced lung function: Some studies associate vaping with changes in airway function and increased respiratory symptoms.
2. The heart and blood vessels
Nicotine is a stimulant that raises heart rate and blood pressure. Researchers are examining how repeated exposure may affect cardiovascular health over time. Areas of active study include effects on blood vessel function and the potential for increased cardiovascular strain, particularly in people with existing heart conditions.
Nicotine matters here. Because most e-cigarettes deliver nicotine, the cardiovascular questions overlap heavily with what is already known about nicotine as a stimulant. Learn more on our nicotine & addiction page.
3. The brain — especially for young people
The human brain continues developing into the mid-twenties. Nicotine exposure during adolescence can affect areas that control attention, learning, mood, and impulse control, and can prime the brain for dependence. This is a central reason public-health agencies emphasize preventing youth vaping. See our dedicated youth & vaping guide.
4. What's actually in the aerosol?
Contents vary widely by product and brand, but analyses have reported the presence of substances such as:
| Component | Why it raises concern |
|---|---|
| Nicotine | Highly addictive; affects the cardiovascular system and the developing brain. |
| Ultrafine particles | Can be inhaled deep into the lungs. |
| Flavoring chemicals | Some flavorings considered safe to eat may not be safe to inhale. |
| Volatile organic compounds & metals | Trace amounts of certain chemicals and metals (e.g., from heating coils) have been detected in some studies. |
The specific mix depends on the device, the e-liquid, temperature, and how the product is used. Unregulated or illicit products carry additional, unpredictable risks.
5. Pregnancy
Health authorities advise that no amount of nicotine is known to be safe during pregnancy. Nicotine can affect fetal development, which is why pregnant people are urged to avoid vaping and to seek support from a healthcare provider.
6. The long-term unknowns
Combustible cigarettes have been studied for many decades; e-cigarettes have not. Because widespread use is relatively recent, scientists cannot yet describe the full range of effects that may appear after 20 or 30 years of use. This uncertainty is itself a reason for caution.