Examining Metal Contents in Primary and Secondhand Aerosols Released by Electronic Cigarettes

Abstract

The usage of electronic cigarettes (ECs) has surged since their invention two decades ago. However, to date, the health effects of EC aerosol exposure are still not well understood because of insufficient data on the chemical composition of EC aerosols and the corresponding evidence of health risks upon exposure. Herein, we quantified the metals in primary and secondhand aerosols generated by three brands of ECs. By combining aerosol filter sampling and inductively coupled plasma mass spectrometry (ICP-MS), we assessed the mass of metals as a function of EC flavoring, nicotine concentration, device power, puff duration, and aging of the devices. The masses of Cr, Cu, Mn, Ni, Cu, and Zn were consistently high across all brands in the primary and secondhand aerosols, some of which were above the regulated maximum daily intake amount, especially for Cr and Ni with mass (nanograms per 10 puffs) emitted at 117 ± 54 and 50 ± 24 (JUUL), 125 ± 77 and 219 ± 203 (VOOPOO), and 33 ± 10 and 27 ± 2 (Vapor4Life). Our analysis indicates that the metals are predominantly released from the EC liquid, potentially through mechanisms such as bubble bursting or the vaporization of metal−organic compounds. High metal contents were also observed in simulated secondhand aerosols, generally 80−90% of those in primary aerosols. Our findings provide a more detailed understanding of the metal emission characteristics of EC for assessing its health effects and policymaking.

Occurrence of metals in e-cigarette liquids: Influence of coils on metal leaching and exposure assessment

“…Thus, the coils were not directly heated through an electrical current, potentially influencing the metal transfer process and therefore the metal concentrations in e-liquids. Thus, metal aerosolization directly from the coil surface would be an unlikely metal release mechanism due to the coil temperature reached compared to actual vaping devices [ 51 ] . Furthermore, other sources of potential metal transfer to e-liquids were not considered in this assay, although EC atomizers are mostly made of metal.…”

“… In the vapor phase, a fraction of metal transfer towards the aerosols is assumed, because a previous study has shown that metal concentrations are much lower in aerosols than in e-liquid tanks [ 22 ]. According to Kapiamba et al [ 51 ] metals are potentially released from e-liquids through mechanisms such as bubble bursting or vaporization of metal–organic compounds. …”

Toxicological Assessment of Particulate and Metal Hazards Associated with Vaping Frequency and Device Age

“…Our findings indicate metal compositional changes that evolve during device usage and aging of components indicating a greater risk of exposure to hazardous levels of toxic metals with continuous use of pod-type ENDS devices. Only two other studies to our knowledge have investigated the difference in aerosolized metal content between new and aged ENDS devices [ 10 , 11 ]. Other studies revealed increasing concentrations of Cr, Zn, Mn, and Ni in ENDS aerosol caused by longer puff durations, which are known to be associated with metallic component degradation during the e-liquid vaporizing process [ 42 , 47 ].…”

“…Indeed, differential vaping patterns or levels of ENDS usage can contribute to exposure variances to various organic and inorganic hazards, including heavy metals [ 7 , 8 , 9 ]. Several metals have been detected in pod-type ENDS aerosols, such as chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), manganese (Mn), and lead (Pb) [ 10 , 11 ]. The primary sources of heavy metals are the metallic components, such as filaments and coils, which can degrade when in contact with oxidized acidic e-liquids leading to additional metal exposure [ 10 ].…”

“…Several metals have been detected in pod-type ENDS aerosols, such as chromium (Cr), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), tin (Sn), manganese (Mn), and lead (Pb) [ 10 , 11 ]. The primary sources of heavy metals are the metallic components, such as filaments and coils, which can degrade when in contact with oxidized acidic e-liquids leading to additional metal exposure [ 10 ]. For instance, a recent study has reported a higher level of Ni and Cr concentration in the aerosolized format compared to the non-aerosolized e-liquid because of leaching from the heating element [ 12 ].…”