Vaping cartridges are self-contained reservoirs filled with a liquid concentrate designed for inhalation using a battery-powered device. These products heat the liquid to create an aerosol, delivering active compounds to the user without combustion. The contents are complex, involving active plant extracts, intentional thickening or thinning agents, and sometimes accidental contaminants. Understanding the precise chemical makeup of this liquid is paramount for consumers seeking transparency and insight into product safety.
The Primary Cannabinoids
The primary goal of most cannabis vape cartridges is to deliver a high concentration of specific cannabinoids, the active chemical compounds found in the cannabis plant. Tetrahydrocannabinol (THC) and Cannabidiol (CBD) are the two most common cannabinoids present, with THC being responsible for the intoxicating effects users seek. THC concentrations in vape oils are often highly refined, frequently reaching levels of 80% or more in products known as distillates.
Distillate is an extract that undergoes extensive purification, stripping away most other plant material to isolate a single cannabinoid, resulting in a clear, potent liquid. Conversely, extracts labeled as “live resin” or “full-spectrum” aim to preserve a wider array of the plant’s original chemical profile. This method involves flash-freezing the cannabis plant before extraction, which helps retain volatile compounds like terpenes and minor cannabinoids.
Beyond THC and CBD, modern formulations often include minor cannabinoids such as Cannabinol (CBN) and Cannabigerol (CBG). CBN forms as THC degrades over time and is associated with sedative qualities. CBG acts as a precursor from which other major cannabinoids are synthesized. The inclusion of these minor compounds is intended to create an “entourage effect,” where the combined action of multiple cannabis compounds enhances the overall experience.
Carrier Agents and Viscosity Modifiers
Because raw cannabis oil is extremely thick, manufacturers often add substances to dilute the extract, improve its flow, or stabilize its consistency for vaporization. These intentional additives, sometimes called cutting agents or diluents, play a significant role in the physical properties of the final liquid. Propylene Glycol (PG) and Vegetable Glycerin (VG) are two common agents borrowed from the traditional nicotine e-liquid market. PG is a thin liquid known for carrying flavor efficiently, while VG is a thicker liquid that produces dense plumes of vapor.
Medium-Chain Triglycerides (MCT) oil, typically derived from coconut oil, was also historically used to thin concentrated oils because it flows easily and has a similar boiling point to THC distillate. However, the use of MCT oil has been associated with potential health concerns, as inhaling lipid-based oils may pose a risk of lipid pneumonia. Many reputable brands have moved away from these agents, favoring natural terpenes to adjust viscosity.
Terpenes are aromatic compounds naturally present in cannabis that contribute to the plant’s flavor and scent profile. When reintroduced to highly purified distillates, these compounds can reduce the oil’s viscosity and improve vaporization efficiency. The most notorious intentional additive was Vitamin E Acetate (VEA), a thickening agent used prominently in illicit market THC carts in 2019. VEA, a viscous lipid oil, was directly implicated as a likely cause of the severe respiratory illness known as E-cigarette or Vaping Product Use-Associated Lung Injury (EVALI). When inhaled, VEA disrupts pulmonary surfactants, leading to acute respiratory distress.
Accidental Toxins and Contaminants
In addition to intentional additives, vape cart contents can be compromised by substances that enter the liquid unintentionally due to poor manufacturing practices or material leaching. One significant concern is the presence of heavy metals, which can migrate into the oil from the heating element and cartridge components. Metals such as lead, nickel, chromium, and copper are often found in the heating coils, solder, and internal metal parts of the cartridge.
This leaching is exacerbated by high operating temperatures or when the cannabis oil has a naturally acidic composition. Studies have shown that these metals can accumulate in the liquid over time, even during storage, and are subsequently aerosolized and inhaled by the user. The presence of these elements is concerning as exposure to metals like lead and nickel is associated with various adverse health outcomes.
Another source of contamination is residual chemicals left over from the cultivation and extraction process, primarily pesticides. Pesticides, fungicides, and other agricultural chemicals used on the cannabis crop can become highly concentrated during the oil extraction process. A small amount of residue in the raw flower can become a significant health hazard in the final concentrated oil product.
Solvents like butane, propane, or ethanol are used to strip cannabinoids from the plant material during extraction. If the post-extraction purging process is incomplete, trace amounts of these residual solvents can remain in the final vape oil, posing a risk to the consumer.
Chemical Changes During Vaporization
The process of vaporization itself, which involves heating the liquid to a high temperature, can trigger chemical reactions that create new, potentially hazardous compounds. This thermal degradation occurs when the ingredients in the liquid are heated past their thermal stability points. For example, common diluents like Propylene Glycol and Vegetable Glycerin can break down under the high heat of the heating coil.
When PG and VG are heated above 200°C, they can produce carbonyl compounds, including formaldehyde, acetaldehyde, and acrolein. Formaldehyde and acetaldehyde are known carcinogens, while acrolein is a severe respiratory irritant. The production of these toxic byproducts is directly affected by the coil temperature and the device’s power settings.
Even the intentional compounds can be chemically altered during heating. Certain pesticides, such as the fungicide myclobutanil, can transform into the highly toxic gas hydrogen cyanide when heated. Similarly, the thermal breakdown of Vitamin E Acetate is thought to generate toxic ketenes, which are highly reactive chemical species. The risk profile is based on both the raw ingredients and the byproducts created under intense heat.