What chemicals are in vape?

The components of e-cigarette liquid are not simple; they form a complex mixture. The basic formula usually consists of four core substances, but during heating and usage, various other chemical substances may be produced or introduced.
Four Basic Components
Almost all e-cigarette cartridges contain the following four basic components:
Propylene Glycol (PG): A common food and drug additive, colorless and odorless, with a slightly sweet taste. In e-liquid, it mainly serves as the carrier for flavoring agents. When heated, it can produce a small amount of smoke and bring about a certain "throat irritation" sensation.
Vegetable Glycerin (VG): It is also widely used in food and cosmetics. It is a thick, sweet liquid. Its main function is to produce a large amount of smoke, which is the key to achieving the visual effect of "vaping".
Nicotine: A natural alkaloid found in tobacco, it is the main addictive substance in electronic cigarettes. It provides the "kick" and satisfies the physiological needs of smokers. It should be noted that nicotine is toxic.
Flavorings: The key factor in determining the taste of the e-liquid. Through the complex combination of various flavors, thousands of different tastes can be simulated, such as fruits, mint, candies, etc.
➕ Other common additives
In addition to the basic ingredients, some e-liquids may also contain:

Water: Used to adjust the viscosity of the e-liquid.
Sweeteners, acids, and throat soothers: Used to enhance taste and the inhalation experience.
Other active ingredients: Some products may contain cannabinoids such as tetrahydrocannabinol (THC) or cannabidiol (CBD).
⚠️ Hazardous and Suspect Chemical Substances
Various chemical substances that may be harmful to health have been detected in e-cigarette liquid. Some of these substances exist as impurities or by-products of reactions.
Category Specific Substance 潜在 Risks and Explanations
Carcinogens Formaldehyde, Acetaldehyde, Benzene, Toluene These are known or potentially carcinogenic substances.
Lung irritants Acetylbutyryl, Benzaldehyde Acetylbutyryl is associated with a severe lung disease called "popcorn lung". Benzaldehyde irritates the respiratory tract.
Heavy metals Lead, Chromium, Copper, Antimony, Nickel, etc. These may come from heating elements inside devices, which are released into the smoke during the heating process.
Volatile Organic Compounds Various volatile organic compounds These are a class of chemicals that readily volatilize at room temperature and are partially harmful to the human body.
Others Tobacco-specific nitrosamines (TSNAs) These are known strong carcinogens and are harmful components in tobacco products.
It should be noted that some substances (such as vitamin E acetate) are related to "EVALI" (E-cigarette-related lung injury), but they mainly occur in illegal THC products and are not within the scope of discussion for regular nicotine e-liquids.
Summary
The main components of e-cigarette liquid are propylene glycol, vegetable glycerin, nicotine and flavoring. However, this is not all. After heating, the e-cigarette liquid releases or generates various harmful or potentially harmful substances including formaldehyde, acetaldehyde, heavy metals, etc. Therefore, the chemical composition of e-cigarette liquid is far more complex than "water vapor".