Not recommended as a habit. In adult smokers it has been used as an aid to quit smoking, but it is not harmless; avoid it in non-smokers and young people.
Vaping is associated with respiratory symptoms, airway inflammation and, in the case of liquids with vitamin E acetate, acute lung injury (EVALI). It is not harmless for the lungs, although its profile differs from combustible tobacco.
See the source (systematic review) →The available evidence associates vaping with adverse vascular and cardiovascular effects (arterial stiffness, endothelial function), although the level of certainty is lower than with tobacco and research is ongoing.
See the source (meta-analysis) →⏱ 3 min read
Vaping (electronic cigarettes) consists of inhaling an aerosol produced by heating a liquid that usually contains nicotine, propylene glycol, vegetable glycerin and flavorings. It does not burn tobacco, so it avoids many of the combustion products of cigarettes; for that reason it is considered less harmful than smoking, but 'less harmful' does not mean 'safe'.
The aerosol is not water vapor: it contains nicotine (highly addictive), volatile organic compounds, metals and fine particles. It is associated with cough, irritation and respiratory symptoms, airway inflammation and vascular effects. Umbrella reviews conclude that there is demonstrated harm and many unknowns because of the lack of long-term data.
In 2019-2020 there was an outbreak of severe acute lung injury (EVALI) linked mainly to black-market liquids containing vitamin E acetate, especially with THC. It illustrates that the composition of the liquid matters and that unregulated products add risk.
Nicotine creates dependence and can affect brain development in adolescents. Vaping is a gateway to nicotine use in young people who would never have smoked, which is why its use is discouraged in nonsmokers and minors.
In adult smokers, some studies suggest it may help them quit combustible tobacco, which is more harmful; but it is not harmless, and ideally vaping should be quit as well. It is not a recommended option for people who do not smoke.
Information, not medical advice. Scientific evidence reflects the quality of the studies.