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2022 Study: Metal Particles in Cannabis Vape Liquids

Updated: Feb 7, 2023

This article was the discussion topic of No. 22 of the Cannabis Commerce + Chemistry Podcast. Listen now.


Welcome to Cannabis Conclusions, a unique educational series from Higher Learning LV that is targeted at hemp and cannabis industry professionals. This series provides readers with the conclusion section from important modern peer-reviewed research studies.

A November 2022 study entitled "Evidence that Metal Particles in Cannabis Vape Liquids Limit Measurement Reproducibility" that was published in the journal ACS Omega employed "scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) and laser ablation inductively coupled plasma mass spectrometry" to investigate "the metal content in cannabis vape liquids from 20 legal and 21 illegal electronic vaping devices."

The study's authors reported that "legal cannabis vape products do not typically provide any information on their packaging about the type of heating element and metal parts used, and illegal products may not even have outer packaging, making it extremely difficult to identify the composition of metal components of the device without additional analysis."

They noted that many other studies have published "detailed lists of identified parts after the scrupulous dismantling of different vape devices," but that the significant number of new designs on the market makes it "difficult to keep up with component changes."

Vape Temperature Matters

In an article entitled "Cold Start Dabbing: Q&A with John Bailey," subject matter expert John Bailey from The Cannabis Commerce + Chemistry Podcast explained the importance of temperature in the process of the vaporization of cannabis and the role of combustion and resulting carcinogens.

"Contamination of vape liquids occurs when the coil is heated to 302-482° F. A recent study showed that, in vaping pens with variable temperature and voltage setting, coils can reach 1,112° F when the tank is filled."

Reported this study, "previous studies showed that significant contamination of nicotine vape liquids occurs when the coil is heated to temperatures between 302-482° F (150-250° C) under normal operating conditions." The research explained that the vaporization of "cannabis vape liquids" (distillates and oils) requires "a slightly higher temperature range 392-662° F (200–350° C). However, a recent study showed that in vaping pens with variable temperature and voltage setting, coils can reach a temperature above 1,112° F (600° C) when the tank is sufficiently filled.

The study observed that "under standard operating conditions, the vaping devices can (i) induce volatilization of dissolved metals and/or fine metallic particles and (ii) compromise the durability of metal components, which are not designed to be exposed to such high temperatures."

Study Conclusions

"While it is true that compared to smoking, vaping reduces the exposure of the user to several toxicants and carcinogens such as polycyclic aromatic hydrocarbons, volatiles, and nitrosamines, there is ample evidence of exposure to metals in vape aerosols. The presented data from legally purchased and illegal cannabis vape devices showed mass fractions of Pb above the currently established tolerance limits in several of the vape liquids analyzed, particularly in the illegal samples where Pb concentrations were up to 100 times higher than the limit.

"Additionally, the measured mass fractions of toxic metals such as Cr, Cu, Ni, and Co, as well as the essential metals Zn and Mn that have known inhalation toxicity, add to the existing evidence that long-term vaping may carry risks to health. More importantly, the use of imaging techniques SEM/EDS and LA-ICP-MS confirmed the presence of metal particles in studied samples. Previous studies suggested that metal particles may be released from the metal coils during the heating cycles to generate aerosols; however, our data showed that metal particles are present in the cannabis vape liquids at the point of purchase, before their actual use. The origin of these particles is unknown.

"Studies suggested that metal particles may be released from the metal coils during the heating cycles."

"Further research studies of vape devices are necessary to better understand the composition of the metal parts of the devices as well as other factors that promote leaching of metals into the liquids (e.g., storage temperature, pH). Given the analytical challenges encountered in the present study, further method development is needed for particle detection by SEM-EDS and LA-ICP-MS. While these techniques provided pertinent information about the identification and distribution of metal particles, their full potential could not be utilized due to the physical properties of cannabis vape liquids.

"Making more information about the metal components of vape device available along with the filling date of the vape device can help support and inform additional research studies and risk assessments. Development of standards for vaping device construction and the materials used could also be considered by standard development organizations to reduce the risks of metals leaching into the vaping liquids."

View the original study.

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