Based on our experience testing compliance samples, engaging with local and state officials on regulations, and working directly with manufacturers and clients, we have identified four major factors related to the production of vape cartridges that warrant additional attention: cutting agents, temperature, flavoring, and hardware and heavy metals.
The role cutting agents play in the dilution of cannabis oil and the deception to the consumer is harmful enough. Yet, even more sinister is what the chemicals added to vape cartridges turn into upon heating. A study (5) of four different cutting agents (propylene glycol [PG], vegetable glycerin [VG], polyethylene glycol 400 [PEG 400], and MCT) found that all four produced measurable amounts of acetaldehyde, acrolein, and formaldehyde when heated to 230 °C (446 °F). Thus, the uncertainty around the content of a vape cartridge is only increased when the unknown material is heated to produce the vapor inhaled by the user.
A quick internet search produces a great deal of information and recommendations about the best temperature for vaping cannabis (6–10). But there’s a disconnect for many consumers who find themselves reliant on vape pens and batteries that express levels of heating intensity not in degrees Celsius (°C) or Fahrenheit (°F), but in units of electric potential (volts) and resistance (ohms). Ohm’s Law (11) dictates the relationship (V = IR) between voltage (V), current (I), and resistance (R) but does not help in directly calculating the resulting temperature from a given voltage or resistance (in fact, Ohm’s Law assumes constant temperature). This is a problem common with all cannabis vape products and not just cartridges and pens purchased illicitly. Across all 14 cartridges used in this study, no cartridge listed the recommended temperature of vaporization. We have seen legal manufactures have physical or visual indicators to control temperature, but consumers don’t always use the battery intended by the manufacturer nor understand how important it is to do so. Only one legal cartridge (Legal Cart A) provided recommended settings of any kind, listing a “recommended voltage” of 3.5 V on the packaging. Based on our review of various sources, this seems to match general industry-wide recommendations of ~3 V.
The key to connecting voltage and resistance to temperature is that the current through the heating coil of a vape pen acts as a proxy for temperature. By Ohm’s Law, at constant resistance, more voltage means more current. More current means more electron activity in the heating coil, causing it to heat more and reach a higher temperature. If a vape pen only has a single voltage option, more volts can be assumed to produce more current and a higher temperature. In practice, it is not possible for the average consumer to get a reliable estimate of the temperature at which their vape pen is operating given the standard specifications of commodity hardware.
Consumers who are able to spend more money on their vape hardware can benefit from engineered solutions that allow for direct control over temperature (12). For those who are unable to afford a temperature controlled vape device, a better unit of measurement than voltage or resistance alone is power (expressed in “W” for watts). Power in watts is the product of the voltage (V) multiplied by the current (in “A” amps). Unlike ratings of voltage or resistance alone, power incorporates a measurement related to time (because current expresses a measurement of electrons flowing per second) that allows for, at least in theory, a representation of the amount of energy being delivered to the vape cartridge per second.
In conclusion, there needs to be more transparency into the hardware’s vaporizing temperature. For this study, we compared voltage settings of 3.5 V versus 5.8 V. We found that even the oil in legal cartridges broke down into unfavorable chemicals when vaporized at higher voltage settings.
Using Gastec gas detector tubes to measure vapors at the higher voltage setting, formaldehyde, carbon monoxide, and hydrogen cyanide were found in the illicit Cartridge A (>50 ppm), illicit cartridge D (>50 ppm), and illicit cartridge F (5 ppm) cartridges. Harmful and potentially harmful constituents (HPHCs) were found at inconclusive levels in both illicit and legal carts (13). This may be due to inconsistent temperature from the battery heating the cartridge oil and the instability of the compounds generated in the vapor.
Cannabis naturally produces flavoring compounds with the most predominant being terpenes. Terpenes represent a wide variety of organic compounds that are produced by many plants. Their commonality between plants is reflected in their nomenclature: pinene, for example, is present in “pine” resin (along with other plants both coniferous and otherwise). The concentration and types of terpenes varies greatly between cannabis varieties.
To make it into vape cartridges, cannabis terpenes can be extracted from the plant, concentrated, and added to the tetrahydrocannabinol (THC) or cannabidiol (CBD) oil in the amount desired by the manufacturer. There are many different extraction methods, with the most common being butane extraction and supercritical CO2 extraction (14). In these two cases, an organic solvent is used to “strip” the terpenes from cannabis and the terpenes are then purified to create a solvent-free concentrated form that can be added to cannabis products.
While naturally present in cannabis flower, terpenes can also be synthesized in a laboratory. Synthesis of terpenes can be accomplished using methods standard to organic and analytical chemistry and synthetic terpenes are a common additive to processed foods (15).
The addition of concentrated terpenes and other flavoring to cannabis vape cartridges is important to consider for two main reasons. First, as with cigarettes and e-cigarettes (16), flavoring in cannabis cartridges can be used to entice consumers, particularly underage users, prone to addiction. Second, as with cutting agents, the chemicals used for flavoring create an unknown element in the resulting vapor because of the heat applied by the vape pen. The resulting aerosols produced by flavoring products have been shown to have widespread effects on various molecular pathways related to lung function (17,18). In the context of illicit vape cartridges, added flavoring is cause for concern because of the sporadic by-products involved with the resulting aerosols present in the consumed vapor as well as the possibility that the flavoring can be used to camouflage the presence of cutting agents and other additives. One can assume that the large amount of unknown compounds found in the illicit carts are additives, which warrant further investigation to identify and quantify.
Among the analytes tested for in this study, flavoring compounds proved the hardest to find and measure. Current regulations do not specify requirements related to flavoring, so standard methods applied to cannabis are not readily available. This is why we determined the unknowns in the illicit carts we tested, that is, the illicit CBD oil cartridge, to be flavorings. While the product’s label claimed a concentration of 10% CBD, testing showed just 0.42%. It also tested at 0% for terpenes, 0% for vitamin E acetate, had no pesticides, and contained no other cannabinoids other than CBD. The only thing outside of CBD that even registered from the standard testing panel run for the sample (replicated to match standard Bureau of Cannabis Control [BCC] compliance guidelines) was a trace amount of ethanol and a level of lead (8.640 µg/g) 17-times greater than the allowed amount.
We can organoleptically assume that vanillin is the primary flavor additive in the illicit CBD cartridge (that is, the cartridge smelled like vanilla). This was supported in the vapor analysis, where this cartridge was the only one that had a positive hit for a flavoring agent (vanillin). Based on our scan data from the sample, vanillin had one of the highest peaks, meaning that the flavoring is a major component of the vape (Figure 2).
- CDC "Morbidity and Mortality Weekly Report (MMWR)"; posted online October 11, 2019 https://www.cdc.gov/mmwr/volumes/68/wr/mm6841e3.htm.
- CDC "Outbreak of Lung Injury Associated with the Use of E-Cigarette, or Vaping, Products"; posted online October 29, 2019, updated October 31, 2019 https://www.cdc.gov/tobacco/basic_information/e-cigarettes/severe-lung-disease.html.
- Bureau of Cannabis Control Text of Regulations, https://bcc.ca.gov/law_regs/cannabis_order_of_adoption.pdf.
- W.D. Troutt and M.D. DiDonato, The Journal of Alternative and Complementary Medicine 23(11), online (2017), http://doi.org/10.1089/acm.2016.0337.
- “Temperature Control Mods” https://www.rockbottomvapes.com/mods-apvs/temperature-control-mods/.
- “What Parents Need to Know about Vaping and JUULing,” https://5210.psu.edu/what-parents-need-to-know-vaping-juuling/.
- “Adding Flavors to E-Cigarette Liquids Changes Chemistry, Creates Irritants” https://corporate.dukehealth.org/news-listing/adding-flavors-e-cigarette-liquids-changes-chemistry-creates-irritants%C2%A0.
- H. Park, M. O’Sullivan, J. Vallarino, et al. Sci. Rep. 9, 1400 (2019) doi:10.1038/s41598-018-37913-9 https://www.nature.com/articles/s41598-018-37913-9.
- RoHS 3 (EU 2015/863) https://www.rohsguide.com/rohs3.htm.
About the Authors
Maha Haq is the Education Administrator at CannaSafe Analytics in Van Nuys, California.
Ini Afia is the Scientific and Technical Director of CannaSafe.
Neya Jourabchian is the Analytical Lab Manager of CannaSafe Analytics overseeing the chemistry and microbial departments.
Direct correspondence to: [email protected]
How to Cite This Article
M. Haq, I. Afia, and N. Jourabchian, Cannabis Science and Technology 3(1), 44-51 (2020).