What are in e cigarettes?

The aerosol produced by e-cigarettes (commonly known as "smoke") is not harmless water vapor. Its composition is far more complex than imagined. Although it avoids some harmful substances produced by traditional tobacco combustion, the e-cigarette liquid (vape oil) and its heating products still contain various substances.
The main components of e-cigarette liquid
E-cigarette liquid is usually composed of the following core substances:
Propylene Glycol (PG) and Vegetable Glycerin (VG): As the base solvent and carrier of the e-liquid, they usually make up the majority of the solution. PG serves as the carrier for the fragrance, while Vegetable Glycerin is responsible for generating a large amount of vapor.
Nicotine (Nicotine): This is the main addictive substance in electronic cigarettes and is present in almost all products. Even products labeled as "nicallyotine-free" may sometimes be detected to contain trace amounts of nicotine.
Flavorings: Used to create various flavors such as fruits and candies. The safety of many flavorings after being heated and inhaled is unknown. Some may even produce toxic substances after heating.
Furthermore, some of the tobacco liquids may also contain water, flavor enhancers, and other ingredients.
⚠️ Other harmful substances generated after heating
When the smoke liquid is heated and atomized, in addition to the aforementioned components, a series of new harmful or potentially harmful substances will also be produced:
Carbonyl compounds: such as formaldehyde, acetaldehyde, propionaldehyde, etc. Some of them are known or suspected carcinogens. Some studies suggest that the formaldehyde content produced by e-cigarettes may be higher than that of traditional cigarettes.
Volatile Organic Compounds (VOCs): such as toluene, etc.
Tobacco-specific nitrosamines (TSNAs): Known potent carcinogens.
Heavy metals: such as lead and cadmium, may come from the heating elements of the equipment.
Other substances: include polycyclic aromatic hydrocarbons (PAHs), phenolic compounds, etc.
⚠️ Materials to be cautious of
Some substances that are known to pose health risks have been used in e-cigarettes, and they require special vigilance:
Diacetyl: A flavoring agent used to create the buttery flavor, and it is associated with the serious lung disease "obstructive bronchiolitis" (popcorn lung).
Vitamin E Acetate: It was once used as a thickening agent in certain illegal THC (tetrahydrocannabinol) e-cigarettes and was the main culprit behind the 2019 EVALI (E-cigarette-Related Lung Injury) outbreak in the United States.
Possible illegal additives
In addition to the regular ingredients, some illegal e-cigarettes may also contain:
Cannabinoids: such as THC (tetrahydrocannabinol), CBD (cannabidiol), etc.
Other drugs: such as synthetic cannabinoids, etomidate, etc. Their use poses extremely serious risks.
Summary
E-cigarette liquid is mainly composed of propylene glycol, vegetable glycerin, nicotine and flavoring agents. However, when these components are heated, various harmful substances such as formaldehyde and heavy metals are produced.
Regarding the specific components and potential risks of e-cigarettes, it is recommended to refer to the latest information released by authoritative public health institutions such as the World Health Organization (WHO) and the Centers for Disease Control and Prevention of the United States (CDC).