Metal Particles Were Found in Cannabis Vape Liquids Before the Devices Were Used

A study of 41 cannabis vape products found evidence that metal contamination can be present in the liquid before a device is ever switched on. The findings point to the vape hardware itself as a possible source of contamination and raise questions about how these products should be tested.

The research, published in ACS Omega in 2022, examined 20 legally purchased cannabis vape liquids and 21 products obtained from the illicit market. The work was conducted by researchers from Health Canada and the National Research Council of Canada. Andrew Waye of Health Canada later presented the findings at the American Chemical Society’s spring meeting in New Orleans in March 2024.

Unlike smoking, vaping heats a cannabis liquid to produce an aerosol rather than burning plant material. That process can reduce exposure to some combustion-related chemicals, but it does not make vaping risk-free. Research on vaping devices has already identified metals such as nickel, chromium and lead in some aerosols, and the U.S. Centers for Disease Control and Prevention notes that vape aerosols can contain heavy metals and particles that reach deep into the lungs.

Using mass spectrometry, the Canadian team measured 12 metals in the cannabis liquids. Arsenic, cadmium and mercury were within the generally accepted Canadian tolerance limits in the tested samples. Lead, however, exceeded the applicable limit in one legal sample and six illegal samples. In the illegal products, lead concentrations reached nearly 49 micrograms per gram—far above the 0.5-microgram-per-gram tolerance limit used for comparison.

The researchers also detected metals that are not always included in routine cannabis testing. Some samples contained elevated levels of chromium, copper, nickel and zinc, while cobalt and manganese were also measured. Several of these concentrations exceeded inhalation-related limits drawn from the European Pharmacopoeia, although those comparisons do not by themselves establish the health risk from using any particular product.

A key finding was the large variation between samples. Even two devices containing liquid from the same product lot could have substantially different metal concentrations. This inconsistency suggests that contamination may be unevenly distributed in the liquid, making a small test portion an unreliable representation of the entire cartridge.

Microscopic and elemental-imaging techniques provided further evidence that some of the metals were present as particles rather than only as dissolved contaminants. The researchers identified particles containing copper, zinc, lead and manganese, along with particles containing combinations of other elements associated with device materials. The particles were not precisely sized, but the imaging results indicated a range from hundreds of nanometers to tens of micrometers; describing all of them simply as “nanoparticles” would be misleading.

Because the cartridges had not been used, the results suggest that at least some contamination can develop while the cannabis liquid is stored in contact with metal components. Possible contributors include the composition and condition of the hardware, the acidity of the liquid, storage time and temperature, and corrosion or leaching from the device. The study did not determine how much of the detected material transfers into the aerosol during vaping or what dose a user would receive.

That distinction is important. Detecting metals in unused liquid is evidence of contamination, not proof that vaping the products causes a particular disease. The study was a laboratory analysis of a limited set of products, and it did not follow people who used them. Additional research is needed to measure metal emissions during actual use and to assess the health effects of repeated exposure.

The findings nevertheless have implications for product oversight. Health Canada’s production guidance requires testing for chemical contaminants, including heavy metals, but the researchers noted that testing cannabis liquid before it is placed into a cartridge may miss contamination introduced later by the device. Testing the finished, filled product—and developing clearer standards for the materials used in vape hardware—could provide a more complete assessment of consumer exposure.

For consumers, the results reinforce that legal status is not the same as zero risk, while unregulated products may carry additional uncertainty. The CDC advises that cannabis oils and concentrates can contain additives or other contaminants and that the health effects of these products are still being studied. Until researchers better understand how metals move from vape hardware into inhaled aerosol, avoiding unregulated cartridges is a sensible way to reduce exposure to unknown contaminants.