I wrote a column titled “What’s In Your Vape Cartridge?” for Cannabis Business Times' February 2019 issue. Later that year, there was an alarming number of lung injuries and deaths associated with the use of vaping products with, at first, no indication of what caused the illness.
There was a lot of speculation as to why people were getting sick from vaping, and products from both the illicit and legal market were considered. Theories ranged from problematic cartridges being those mixing nicotine with THC to those filled with propylene glycol or vegetable glycerin, which are mixed with oil to get a desired viscosity in cartridges, as well as speculating that THC or other cannabis derivatives were to blame. Both cannabis-derived compounds and non-cannabis fillers were named as possible culprits.
In the end it was determined that vitamin E acetate—used both as a cutting agent and a viscosity adjuster—was responsible for the illnesses, and it was dubbed “E-cigarette or Vaping Use-Associated Lung Injury” or EVALI by the Centers for Disease Control. In the end, the CDC indicated that more than 2,800 cases were reported and 68 people died. The agency pointed out that the outbreak was not caused by legal, regulated cannabis or tobacco products, but rather illegal products from illicit-market manufacturers were primarily to blame. However, the crisis damaged sales of safe, legal and legitimate vape products, resulting in millions in lost sales.
After the responsible chemical was identified and some illicit producers were arrested, the epidemic faded as quickly as it began, and another health crisis—the COVID-19 pandemic—dominated headlines.
Problems in Pennsylvania
That said, there are still products in the legal market facing scrutiny. In February 2022, Pennsylvania’s health department recalled more than 600 vape cartridges from small and large operators alike because some of the ingredients in the products have not been deemed safe for inhalation by the FDA. The state department published a list “of known additives contained in one or more products on the withdrawal list,” some of which are deemed “food safe,” but not for inhalation. The list includes compounds such as almond oil bitter, roman chamomile flower oil, cinnamon bark oil, eucalyptus oil, fir needle oil, ginger root oil, juniperberry oil, lavender oil, pepper oil, peppermint oil, as well as other terpene additives.
What remains unknown is what is the safe threshold of each of these chemicals to inhale when heated? And what is the FDA-safe threshold to inhale all of them combined?
Vape Cartridges Today
Despite large recalls and the EVALI crisis, the legal vaping cartridge market has rebounded and remains a very robust segment of the cannabis industry today. According to the cannabis research firm Headset, vape cartridge market share has steadily increased. “In the U.S., market share has increased from 18.9% in April 2021 to 22.1% in April 2022,” which represents the second largest category behind the always-dominant flower, according to Headset. While the ramifications of the Pennsylvania recall remain to be seen, there are still questions surrounding what is in vape cartridges now?
The answer is not straightforward, and there are myriad cannabis oil extraction methods and associated extraction equipment.
Propylene glycol and vegetable glycerin are still utilized in both tobacco cartridges as well as a small segment of the cannabis cartridges available today, but that market is slowly dwindling because of a proliferation of products that only contain cannabis derivatives. Glycerin and glycol are sometimes utilized to dilute the viscosity of a cannabis distillate, which needs to be thinned to be able to be wicked into the heating element of a vape cartridge. Because distillation can remove delicate aromatic terpenes, some operators also utilize both cannabis- and non-cannabis derived terpenes or essential oils to their distillate to add back flavor.
Non-cannabis derived terpenes and/or essential oils are distilled or sourced from fruits and plants. They are typically steam distilled. Many of these terpenes and or essential oils are available for sale as additives to a cannabis or cannabinoid distillate and are utilized to attempt to mimic the flavor and odor of cannabis (a tall order considering it contains approximately 150 identified terpenes). Cannabis-derived terpenes are sourced via multiple methods in multiple forms, yet they are all derived from the cannabis plant only.
So how are THC and other cannabinoid and terpene vape cartridge ingredients manufactured and what equipment or method of extraction yields exactly what? Here is a breakdown of the most common extraction methods used in products on the market today:
- Hydrocarbon extraction: Utilizing solvents like butane and propane, hydrocarbon extraction can yield extracts ideal for producing specialized cannabis products like shatter, budder, wax or sauce, in addition to live resin cartridges. Starting with fresh, undried, frozen cannabis flower results in elevated terpene preservation.
- CO2 extraction: Subcritical and supercritical CO2 extraction utilizes pressurized CO2 gas to extract crude oil from dried cannabis, which typically requires further refinement via winterization and/or distillation. CO2 extracts can be produced relatively inexpensively and are the main ingredient in many cartridges available today.
- Ethanol extraction: Utilizes ethanol alcohol as a solvent to produce a crude oil from cannabis, which requires further refinement, typically via winterization and distillation. Ethanol extracts, like CO2 extracts, are used in many vape cartridges available today. The lighter, delicate aromatics, such as monoterpenes and sulfur-based thiols, can be lost in the resulting distillate.
- Rosin extraction: Rosin is a solventless extraction method using pressure and heat to release a combination of cannabinoids and terpenes to produce more concentrated, specialized products. It is typically produced using dried plant material or resin glands/trichomes from fresh, frozen undried plant material that are separated via dry sieve methods, or with water to separate the glands (i.e., water hash). The plant material is placed in a mesh bag and is then pressed using a rosin press, which applies a specific pressure for a specific duration at a specific temperature (preferably as low of a temperature as possible—guideline vary). The material is filtered through the mesh bags so that the desired active ingredients (cannabinoids and terpenes) are separated from the undesired plant material or resin gland debris and stocks. The resulting isolate is called rosin and can be made into many concentrated forms, including sauce, from which THCA diamonds/crystals are made. These can be separated from the other viscous cannabinoids and terpenes, or can be utilized to flavor a distillate.
Terpenes are essential oils that, when combined with sulfur-based thiols and other chemicals, are responsible for the aroma and flavor of cannabis. There are many classes of terpenes, the primary three being monoterpenes, diterpenes, and sesquiterpenes. Combined with other aromatic compounds, they create the plethora of aromatically diversified cultivars of cannabis.
As with cannabinoids, there are multiple methods of producing/ extracting cannabis terpenes:
- Hydrocarbon extraction: Butane/propane solvents are utilized to extract cannabinoids and terpenes mixed together from fresh undried or cured cannabis. The resulting terpenes can be utilized by themselves in a cartridge or to adjust the viscosity of a distillate as well as add aroma and flavor.
- CO2 extraction: CO2 extraction utilizes pressurized CO2 gas to extract terpenes.
- Ethanol extraction: Ethanol is utilized to essentially dissolve the resin glands/trichomes and release the active ingredients into the alcohol/solvent. The alcohol also releases unwanted compounds, as well, which require further refinement via distillation and winterization to separate the desirable and the undesirable.
- Rosin extraction: After pressing the rosin into a jar or sealable glass container, the rosin is subjected to elevated temperatures under vacuum, which encourages cannabinoids to sink to the bottom of a jar. The lighter terpenes to rise to the top of the extract, resulting in an isolate that has a distinct separation of cannabinoids in crystallized form, and a cannabinoid terpene sauce that can be utilized by itself to fill a vape cartridge or to add flavor to a flavorless distillate.
- Microwave extraction: Utilizes microwave technology to extract terpenes from fresh, fresh-frozen or dried and cured flower without the use of solvents.
- Low-temperature vacuum distillation: Utilizes low temperature vacuum distillation to isolate and capture terpenes.
Depending on the extraction method, the final vape cartridges can include these primary ingredients:
- Distillate: Sourced from CO2 and ethanol extraction, distillate can be mixed with viscosity adjusters and both cannabis-derived and non-cannabis derived terpenes. Sometimes a distillate is mixed with a flavorful live resin hydrocarbon extract or rosin. The distillate is typically a product of CO2 or ethanol extraction that has been further refined via distillation.
- Live resin hydrocarbon extracts: May be mixed with a distillate, but also can be the sole ingredient in a cartridge.
- Rosin: Yields terpene isolates that can be utilized by themselves in a vape cartridge but may also be mixed with a distillate.
As I wrote in 2019, as we develop new products and formulations within this space, we will also have to wrestle with health and safety concerns. A lot of unknowns exist with cannabis. We still don’t know the acceptable thresholds for heated inhalation of single or combinations of concentrated terpenes, for example. Legal producers are doing their best with the information they have. What are acceptable levels for inhalation of these essential oils at an elevated temperature? I don’t suspect there will ever be an answer.