The practice of vaping marijuana involves heating cannabis flower or concentrated extracts to a temperature high enough to vaporize the active compounds but low enough to avoid combustion. This process creates an aerosol, often incorrectly referred to as vapor, which is then inhaled into the lungs. This method delivers psychoactive and therapeutic compounds, primarily cannabinoids and terpenes, without the harsh byproducts associated with burning plant material.
Mechanism of Vaporization
Vaporization relies on precise temperature control to convert cannabis material into an inhalable mist by reaching the boiling points of desired compounds without initiating pyrolysis. This temperature range typically falls between 315°F and 440°F (157°C and 227°C), remaining safely below the combustion point of cannabis plant matter, which is approximately 451°F (233°C).
Within this controlled heat environment, cannabinoids like delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), alongside aromatic terpenes, are released into the air as an aerosol. Devices achieve this through two main types of heating: conduction, where the material directly contacts a heated surface, or convection, which uses hot air passing over the material. Convection heating is often preferred because it promotes more even heating, reducing the risk of accidental burning and unwanted byproducts.
The resulting aerosol is a mixture of fine particulate matter, cannabinoids, and terpenes, which is chemically distinct from smoke. This process efficiently delivers the active compounds to the lungs for rapid absorption into the bloodstream.
Components and Contaminants in Vape Products
The aerosol’s composition is determined by the cannabis extract and non-cannabinoid substances in the cartridge. Since concentrated cannabis oils are highly viscous, thinning agents are often added to ensure they flow correctly through the heating element. Common diluents include propylene glycol (PG), vegetable glycerin (VG), and medium-chain triglycerides (MCT oil).
When heated, these thinning agents can chemically degrade into toxic carbonyl compounds, such as formaldehyde and acetaldehyde. Inhaling MCT oil has also been associated with the risk of lipoid pneumonia, a condition where fat particles build up in the lungs.
A particularly harmful additive identified during the 2019 outbreak of e-cigarette or vaping product use-associated lung injury (EVALI) was Vitamin E Acetate (VEA). This compound was illegally used to thicken or dilute illicit THC vape liquids, and its presence was confirmed in the lung fluid of EVALI patients. When heated, VEA can generate highly reactive byproducts that contribute to severe oxidative lung damage.
Beyond the liquid composition, the devices themselves can introduce heavy metal contaminants into the aerosol. The metal heating coils and internal components, often made of alloys containing nickel, chromium, and manganese, can leach into the cannabis oil. Poorly manufactured cartridges have shown measurable levels of these metals, including lead, which is a significant concern for inhalation toxicity.
Acute Physiological Effects
Inhaling vaporized cannabis leads to a rapid onset of effects due to the high bioavailability of cannabinoids through the lungs. Rapid absorption allows active compounds to enter the bloodstream almost immediately, resulting in peak blood concentrations of THC within minutes. This efficiency means an equivalent dose of vaporized cannabis can produce more pronounced drug effects and higher circulating levels of THC compared to smoked cannabis.
The cardiovascular system experiences an immediate response following the inhalation of THC-dominant vapor, typically including an increase in heart rate (tachycardia) and elevated blood pressure. Studies have also observed an acute increase in arterial stiffness, a measure of cardiovascular function, which occurs regardless of whether the cannabis is smoked or vaporized.
The respiratory system is exposed to fine particulate matter (PM2.5) and chemical irritants present in the aerosol, which can cause direct pulmonary effects. While vaporization reduces many combustion-related toxins, the inhalation of the aerosol can still lead to respiratory symptoms and, in severe cases linked to specific contaminants like Vitamin E Acetate, acute lung injury.
Vaping vs. Smoking: Differences in Inhaled Byproducts
The primary difference between vaping and smoking cannabis lies in the temperature reached and the resultant chemical processes. Smoking involves combustion, which occurs above 451°F (233°C), generating a complex mixture of smoke. This combustion creates hundreds of thermal degradation products, including known toxins like carbon monoxide, tar, and polycyclic aromatic hydrocarbons (PAHs).
Vaporization, by operating below this combustion point, substantially reduces the formation of these harmful byproducts. The aerosol produced largely consists of the desired cannabinoids and terpenes, with drastically lower concentrations of the carcinogenic compounds found in smoke. For instance, the levels of carbon monoxide exposure are significantly reduced when switching from smoking to a vaporizer.
However, the vapor is not entirely benign, as the heating of certain thinning agents can still produce thermal degradation products like formaldehyde. Even with this potential for contaminant formation, research indicates that vaporization is associated with far fewer hazardous substances compared to the combustion products inherent in cannabis smoke.