Exposure to Toxicologically Relevant Inorganic Elements and Nicotine Content Variability in Electronic Nicotine Delivery System (ENDS) E‑Liquids

Abstract

In recent years, electronic nicotine delivery systems (ENDS) have gained prominence as alternatives to conventional cigarettes, raising concerns due to the increasing number of lung injury cases associated with their use. These devices rely on e-liquids composed primarily of propylene glycol, glycerin, flavorings, and nicotine, which are heated to produce inhalable aerosols. In this context, the present study aimed to quantify nicotine concentrations and assess the presence of toxicologically relevant inorganic elements in e-liquids to evaluate potential inhalation-related risks. Nicotine was quantified using high-performance liquid chromatography with diode-array detection (HPLC–DAD), whereas inorganic contaminants were determined using inductively coupled plasma–mass spectrometry (ICP–MS). Nicotine concentrations ranged from nondetectable to 33.4 mg·mL–1, and significant discrepancies were identified in the labeling information. Arsenic (As), lead (Pb), nickel (Ni), chromium (Cr), and mercury (Hg) were detected at variable concentrations; notably, the estimated daily exposures for Cr and Hg exceeded the permitted daily exposure (PDE) limits established by the International Council for Harmonization (ICH). Overall, these findings indicate that ENDS may be a significant source of toxic metal exposure, posing potential risks to human health.