Presence of heavy metals in e-liquids of pre-filled electronic cigarettes

A study conducted in four countries indicates the presence of heavy metals in e-liquids for closed-system electronic cigarettes (pods).[1], puffs[2]); such results were not observed in this study for open system e-cigarettes (e-liquid refill), whereas they were in other studies.

The presence of heavy metals (chromium, nickel, lead, etc.) in e-liquids for electronic cigarettes has already been pointedIt would be produced by the release of the elements composing the electronic device or their contamination of the e-liquid. A study which compared several types of devices pointed out the presence of these heavy metals in pre-filled electronic devices.

Closed-system devices sold in the United States have the highest concentrations of heavy metals.

The researchers tested 116 open-system devices and 120 closed-system products, purchased in the United States, Canada, England, and Australia in 2017 and 2018, and subjected them to electrothermal atomic absorption spectrography.[3]. Different types of e-liquid flavors were also tested.

The presence of lead, chromium, and nickel was only found in the e-liquids of closed-system e-cigarettes, at worrying levels and with significant variations depending on the model and country. Closed-system e-cigarettes sold in the United States contained more heavy metals than those sold in England or Canada. Some closed-system products containing fruity or menthol flavors showed higher concentrations of heavy metals than those containing tobacco flavors, with a few notable exceptions.

Many possible sources within the products

The authors believe that this presence of heavy metals could be explained by infiltration from the electronic device. The highest concentration in closed-system devices would result from prolonged contact between the e-liquid, the wick, and the coil. The high concentrations in fruity e-liquids could stem from the acidity of certain fruits and its effect on metals, raising questions about the pH of e-liquid ingredients. Many product characteristics can also affect the release of these elements and could explain the large variations in metal levels observed.

Additionally, e-liquids were only tested before use, but other studies have shown that aerosols produced by open-system types of e-cigarettes may also contain heavy metals.[4]The large differences in the concentration of heavy metals in open systems could be explained in particular by the high variability of these systems, particularly when they are modifiable.

The presence of heavy metals is worrisome not only because these elements are carcinogenic, but also because they can disrupt the central nervous system, the endocrine system, and reproductive functions. They can affect certain organs, such as the lungs, liver, or kidneys. The authors recommend significantly strengthening the regulatory arsenal to prevent heavy metal contamination of these e-cigarettes. The significant differences in regulations between countries would also require harmonization at the international level.

Keywords: electronic cigarettes, e-liquids, heavy metals, flavors.

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[1] Electronic cigarettes with cartridges.

[2] Disposable electronic cigarettes.

[3] Block AC, Schneller LM, Leigh NJ, et al. Heavy metals in ENDS: a comparison of open versus closed systems purchased from the USA, England, Canada and Australia, Tobacco Control, Published Online First: 12 July 2023. doi: 10.1136/tc-2023-057932

[4] Zhao D, Navas-Acien A, Ilievski V, et al. Metal concentrations in electronic cigarette aerosol: effect of open-system and closed-system devices and power settings. Environ Res 2019;174:125–34.

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