Vape Metal Risks May Begin Before the Heating Coil

Concerns about metals in vaping products usually begin with the device. Heating coils, solder joints and other metallic components can release material into the liquid and aerosol, particularly as a cartridge ages. New research suggests that this explanation may capture only part of the problem.

An exploratory study published in Global Transitions¹ detected cadmium, chromium, cobalt, manganese, nickel and lead in every unused nicotine refill liquid it tested. Because the researchers analyzed the liquids before they entered a consumer device, the metals could not have originated from the users’ heating coils. Some contamination was already present upstream.

The study did not test cannabis oils, so its measurements cannot be applied directly to cannabis cartridges. Its central lesson is nevertheless highly relevant to the cannabis industry: testing the finished aerosol or blaming the cartridge alone may overlook contamination introduced through ingredients, manufacturing equipment, filling systems, packaging or storage.

What Researchers Found in Unused Vape Liquids

The researchers analyzed 19 unused refill liquids from products labelled as originating in the United Kingdom, Malaysia and the United States. Four products from one brand did not identify a country of origin. The sample included different flavours, nicotine concentrations and nicotine formulations, but it was intentionally selected for variety rather than designed to represent the entire market.

All six metals under investigation appeared in all 19 samples. Manganese had the highest mean concentration at 11.74 milligrams per kilogram, followed by cobalt at 7.35 milligrams per kilogram. The presence of multiple metals across every product is more important than any one concentration because it indicates that pre-device contamination was not confined to a single isolated sample.

No statistically significant differences in metal concentrations were found among the labelled countries of origin. That does not prove geography is irrelevant. With only 19 products, unequal country groups and incomplete origin information, the study was not equipped to rank national markets or manufacturing systems.

Why Detection Does Not Equal Inhaled Dose

The most dramatic numbers in the paper come from a screening-level risk assessment, but these require careful interpretation. The researchers did not aerosolize the tested liquids, measure how much metal reached a user’s lungs or track health outcomes. Instead, they modelled different percentages of each metal transferring from liquid into aerosol.

Even at an assumed transfer efficiency of 1%, the combined non-cancer hazard index remained above the benchmark value of one. Modelled cancer risk also exceeded the study’s selected benchmarks. However, the calculation treated all measured chromium as hexavalent chromium, or Cr(VI), because the experiment did not determine its chemical form. That conservative assumption drove approximately 96% of the modelled cancer risk and could substantially overstate it if much of the chromium was present in less hazardous forms.

The results therefore identify a reason for further testing, not a forecast of disease. Actual exposure would depend on the metal’s chemical form, its transfer into aerosol, the device, temperature, user behaviour, respiratory deposition, absorption and elimination. The correct conclusion is that unused liquid can be a source of metals available for transfer, not that every detected amount reaches the consumer.

How Metals Could Enter Before the Cartridge

The study did not isolate the origin of the contamination, but it outlines several plausible routes. Raw ingredients may arrive with trace impurities. Liquids may contact metal-bearing machinery during mixing or filling. Containers, dispensers and storage equipment may contribute additional material. Formulation acidity could also affect how readily some metals move from a surface into a liquid, although this study did not establish that mechanism.

For cannabis manufacturers, the potential routes are even more varied because the plant itself can accumulate metals from soil. Extraction, refinement, terpene blending, storage and cartridge filling then create additional control points. The practical response is a supply-chain strategy rather than a single end-of-line test:

• Qualify ingredient and hardware suppliers.
• Test oils before and after filling.
• Audit product-contact equipment and containers.
• Retain batch records that support traceability.

This approach resembles the broader shift toward more capable cannabis testing laboratories, where automation and improved analytical workflows are being used to identify contaminants more consistently.

Why Cannabis Vapes Need Their Own Evidence

Nicotine refill liquids and cannabis extracts are not chemically interchangeable. Conventional e-liquids commonly rely on propylene glycol and vegetable glycerin, while cannabis cartridges generally contain concentrated cannabinoids with terpenes or other formulation components. Differences in viscosity, acidity and composition can change how metals move through the liquid and aerosol.

That is why the new paper should guide questions about cannabis products rather than provide cannabis-specific answers. Fortunately, direct evidence is beginning to develop. A 2025 study tracking metals in regulated and illicit cannabis vaping products found that contamination patterns can reflect both the liquid and cartridge hardware. MyCannabis previously examined those results in Are Cannabis Vapes Leaching Toxic Metals?, which highlighted wide variation among products and the difficulty of catching a contaminated unit through limited sampling.

The underlying cannabis vaping product research also reinforces a crucial distinction: finding a metal in liquid does not establish how much will be inhaled. Particle size, metal species and device performance all influence exposure. Still, results from cannabis and nicotine products now point toward the same broader idea. The liquid and the device should be treated as interacting parts of one exposure system.

Testing Should Follow the Product Through Production

Most compliance programs rely on testing a sample at a defined stage. That can confirm whether the sampled material met a standard at that moment, but it may miss contamination introduced later or variation among individual cartridges. A clean bulk extract could contact a problematic filling line or cartridge. Conversely, a well-designed cartridge cannot remove metals already present in the oil.

A stronger framework would compare the product at multiple stages: incoming ingredients, formulated bulk liquid, filled cartridge and generated aerosol. This would help manufacturers locate where concentrations change and distinguish agricultural contamination from processing or hardware contributions. It would also make corrective action more precise. Replacing cartridge hardware will accomplish little if the source is a botanical ingredient, while changing an extraction process will not solve leaching from a metal component.

Batch averages deserve scrutiny as well. If contamination is unevenly distributed, one composite sample may conceal high readings in a small number of units. Risk-based sampling should account for different hardware lots, filling runs, storage periods and formulations rather than assuming that every cartridge from a production batch behaves identically.

Regulation Must Address Both Oil and Hardware

Health Canada’s vaping guidance already recognizes that heavy metals may leach into cannabis concentrates and be inhaled. The new nicotine-liquid study extends the regulatory question upstream: what if some metals are present before the liquid ever reaches the consumer-facing device?

Regulators consequently need standards that clarify which metals must be measured, at what production stage and using which exposure assumptions. Limits designed for swallowed products may not adequately represent inhalation. Rules also need to address chromium and nickel alongside the metals already common in cannabis contaminant panels, while recognizing that total concentration alone cannot always reveal toxicity without speciation and aerosol-transfer data.

Manufacturers should not wait for every uncertainty to disappear. Supplier audits, validated cleaning procedures, inert product-contact surfaces, batch-level testing and stronger traceability are established quality controls. Applying them across the complete vape supply chain could reduce contamination while producing the data needed for better regulation.

A Broader View of Cannabis Vape Safety

The study’s most useful contribution is not its modelled risk figure. It is the demonstration that contamination can precede the heating coil. That finding changes where investigators should look and prevents cartridge hardware from becoming the automatic explanation for every metal detected in an aerosol.

For cannabis vaping, safety should be understood as a chain extending from cultivation and ingredient sourcing through extraction, formulation, filling, hardware selection and actual use. Testing only one link can leave another unexamined. The evidence does not show that all cannabis vapes contain dangerous metal concentrations, but it does support a more complete question: not only what does the device release, but what was already in the oil before heating began?

References:

¹ Wilson, K., Burfoot, S., Belyamani, I., Kumbhar, P., & Alrumaithi, M. A. M. B. (2026). Toxic metals in unused vape refill liquids from multiple markets: An exploratory screening-level risk assessment. Global Transitions. https://doi.org/10.1016/j.glt.2026.09.006