FDA Publication on Elemental Impurities in Cannabis following Vaporization

Following the previously issued article on microbial contamination, authors from the FDA recently published an article on elemental impurities in cannabis following vaporization. The experimental study evaluated a single vaporizer and three cannabis plant materials suggesting a transfer of heavy metals from cannabis material to cannabis vapor may not occur during the vaporization process under the applied study conditions.


The use of vaporizers to inhale cannabis is a technique that has risen in popularity and there is a general perception that vaporizers are “safer” when compared to more traditional cannabis smoking via combustion (i.e., cigarettes). Regarding elemental impurities, pharmacopoeial monographs on herbal drugs (e.g. the new Ph. Eur. Cannabis flower monograph) usually focus on the four heavy metals Pb, As, Cd, and Hg, because these four elements have a potential risk on public health. Therefore, the aim of this study was to investigate the potential transfer of those metallic elements from cannabis material to cannabis vapor through the vaporization process.


In this study a single commercial vaporizer, Volcano Digit (Storz & Bickel GmbH & Company, Tuttlingen, Germany) was used. All three cannabis materials (placebo, low potency, and high potency) were exposed to four heat treatments including a case that simulates a clinical scenario of vaporizing cannabis using a tabletop vaporizer with attached bag. However, in this study, the vapors collected in the bag during the simulation were not able to be analyzed. The quantification of elemental impurities was conducted for the cannabis materials in all four heat treatments both prior and post heating treatments. Based on the differences between the prior and post heating treatment sample analysis, the amount of elemental impurities that might transfer into the vapor phase of the bag could be calculated accordingly.


The results obtained in this study revealed that the four metallic analytes Pb, As, Cd, and Hg (plus additional elements like Mg, Al, Zn, etc.) were present in all three types of cannabis material and the concentrations of each element were similar across the three tested cannabis materials. However, Mg was observed as the element with the highest concentration in all cannabis samples. No significant concentration differences were observed for each element before and after vaporization. This potentially indicates that all the quantified elements remained in the samples. Therefore, it appears almost no elemental impurities could be transferred into the cannabis vapor phase from the raw material through the vaporization process under the four heating treatments evaluated. However, the elemental impurities might be detected in the cannabis vapor phase during the heating process with a much higher temperature (> 190 °C) and/or longer heating period (> 70 s). To evaluate this, additional investigations might be needed, the authors conclude.

More information is available in the article Analysis of elemental impurities in cannabis following vaporization published in Talanta Open.

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