Introduction: The long-term health impacts of e-cigarettes, colloquially known as vapes, are unknown. The inhalation of harmful chemicals and heavy metals via the lungs has been linked to serious adverse health consequences, much the same as tobacco. The rapid worldwide increase in e-cigarette users, the availability of ubiquitous cheap delivery devices, ingredients manufactured from unknown sources, poor quality control, and limited regulation or oversight necessitate the exploration of how these products influence respiratory health [1-3]. Studies have primarily focussed on nicotine and a limited set of organic compounds, leaving trace-level elemental composition largely unexamined. Little is known about the long-term accumulation of harmful substances in tissues and their potential to cause diseases, such as Chronic Obstructive Pulmonary Disease (COPD), neurodegenerative disorders, and cardiovascular conditions [2-4].

Method: We employed a comprehensive approach to determine the elemental profiles of a commercial e-cigarette liquid (18mg/mL nicotine, tobacco flavour, 50% Propylene Glycol (PG)/50%Vegetable Glycerin (VG), Vaper Empire, VIC) and vapours using a combination of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Thermal Desorption Gas Chromatography ICP-MS (TD-GC-ICP-MS) for elemental speciation. Elemental bioaccumulation in lung tissues of mice exposed for 3 days was assessed using Laser Ablation ICP-MS (LA-ICP-MS). This approach was designed to simulate human exposure to e-cigarette vapour and quantify metal deposition in lung tissues.

Results: Our analysis detected high concentrations of metals in e-cigarette liquids, including zinc (Zn, 48.01 µg/g), nickel (Ni, 36.06 µg/g), copper (Cu, 29.26 µg/g), aluminium (Al, 8.53 µg/g), iron (Fe, 8.06 µg/g), arsenic (As, 0.63 µg/g), tin (Sn, 5.01 µg/g), mercury (Hg, 1.08 µg/g), chromium (Cr, 3.79 ug/g) and lead (Pb, 7.37 µg/g). Except for Fe, these concentrations exceed those typically found in tobacco products. Additionally, organometallic compounds of As, Hg, Sn, Cu, Cr, and Fe were detected in the e-cigarette vapours via TD-GC-ICP-MS, confirming the presence of reactive and bioavailable metal species. LA-ICP-MS analyses of murine lung tissues exposed to e-cigarettes showed significant bioaccumulation of Sn, Ni, Pb, Fe, Cu and Cr throughout the lung sections. The detection of these toxic organometallic species in vapour and their accumulation in lung tissues raises concerns about their potential for systemic metal accumulation, triggering inflammatory response, oxidative stress, and cellular damage. These effects may contribute to the increased risk of chronic respiratory conditions, neurodegenerative diseases, cardiovascular disorders, and potentially cancer in e-cigarette users. Our findings suggest that even short-term exposure to e-cigarette vapour may lead to harmful bioaccumulation and a heightened risk of chronic disease.

Figure 1. Elemental bioimage of tin (Sn) in murine lung tissue after one week of e-cigarette vapour exposure demonstrating potential for exogenous metal bioaccumulation from e-cigarette use.

References

[1] World Health Organisation WHO report on the global tobacco epidemic., 2023, p. 216.

[2] J Birdsey, M Cornelius, A Jamal, et al. Tobacco Product Use Among U.S. Middle and High School Students, 2023, CDC National Youth Tobacco Survey

[3] Action on Smoking and Health (ASH). Use of e-cigarettes (vapes) among young people in Great Britain. 2024.

[4] Olmedo, P et al. Metal exposure and biomarker levels among e-cigarette users in Spain. 2021, Environmental Research, 202, 111667.