Vaping, often perceived as a safer alternative to smoking, involves inhaling an aerosol created by heating a liquid, commonly known as e-liquid or vape juice. While this aerosol is not the same as tobacco smoke, it is far from being just “water vapor.” A complex mixture of chemicals, some with known health risks, are present in both the e-liquid and the aerosol that is inhaled.
The Foundation: Base Liquids and Nicotine
The majority of e-liquids are composed of two primary base liquids:
- Propylene Glycol (PG): A synthetic organic compound that is colorless and odorless. It is used in a variety of applications, including as a food additive and in theatrical smoke machines. In vapes, it is effective at carrying flavor and providing a “throat hit” similar to that of smoking.
- Vegetable Glycerin (VG): A thick, sweet-tasting liquid derived from vegetable oils. It is responsible for producing the dense vapor clouds associated with vaping.
While both PG and VG are generally recognized as safe for ingestion by the U.S. Food and Drug Administration (FDA), the long-term effects of inhaling them are not as well understood.
Most vape products also contain nicotine , the highly addictive substance found in tobacco. The concentration of nicotine can vary widely between products, and some “nicotine-free” e-liquids have been found to contain trace amounts.
The Flavor Factor: A Myriad of Chemicals
A significant draw of vaping is the vast array of available flavors, from fruity to dessert-like.11 These flavors are created using a wide range of chemical additives. While many of these flavoring chemicals are considered safe for consumption in food, their effects when heated and inhaled can be different and are a subject of ongoing research.
One notable example is diacetyl, a chemical that has been linked to a serious lung disease called bronchiolitis obliterans, also known as “popcorn lung.” Although it is now less common in e-liquids, its presence in some products in the past has raised concerns about the safety of inhaled flavorings.
The Transformation: Chemicals in the Aerosol
The heating process, which turns the e-liquid into an inhalable aerosol, can lead to the formation of new and potentially harmful chemicals. These include:
- Carcinogens: The high temperatures can cause the breakdown of PG, VG, and flavorings into carcinogenic compounds such as formaldehyde , acetaldehyde , and acrolein . Formaldehyde is a known human carcinogen, and acrolein can cause irreversible lung damage.
- Volatile Organic Compounds (VOCs): These are chemicals that can have various adverse health effects. Benzene, a VOC found in car exhaust and a known carcinogen, has been detected in vape aerosol.
- Heavy Metals: Trace amounts of heavy metals, including lead , nickel , tin , and chromium , can leach from the heating coil and other components of the vaping device into the aerosol. These metals can be toxic to the body.
- Ultrafine Particles: The aerosol itself consists of tiny particles that can be inhaled deep into the lungs, potentially causing respiratory irritation and other health problems.
It is important to note that the specific chemicals and their concentrations can vary significantly depending on the vaping device, the e-liquid formulation, and the user’s vaping habits, such as the temperature and puffing duration. The lack of comprehensive regulation and standardized manufacturing processes for all vaping products further contributes to the variability in their chemical composition.