Examining the Oxidation State of the Metals in the Aerosols and Vape Liquid of Electronic Cigarettes

KAPIAMBA KASHALA FABRICE, Stephen Adom, Yue-Wern Huang, Yang Wang, Missouri University of Science and Technology

     Abstract Number: 234
     Working Group: Health-Related Aerosols

Abstract
Since their invention, electronic cigarettes (ECs) have been promoted as safer alternative means of quitting smoking and avoiding inhaling toxic substances. However, several studies have confirmed the presence and, in some instances, high levels of similar toxic substances found in EC aerosols. Specifically, though several toxic substances have been associated with ECs usage, heavy metal poisoning is of concern due to their potent toxicity at low concentrations, even at nanograms scale per puff (Kapiamba et al., 2022). Nevertheless, knowing that some metals in certain oxidation states are known to be safe depending on the exposure route, there is a need to study the oxidation states of these metals.

In this study, using X-ray photoelectron spectroscopy (XPS), we examined the oxidation state of metals collected in the aerosols generated from ECs and contained in the vape liquid. The XPS survey spectrum of filters film the presence of metals previously characterized using ICP-MS, namely Cr, Cu, Ni, Pb, and Zn. The corresponding high-resolution spectra of Cr 4f, Cr 3d, Cu 2p, Ni 2p, Pb 4f, and 5d, Zn 2p were studied and revealed metal oxidation states. For instance, Zn 2p showed two spin-orbit components, 2p_3/2 and 2p_5/2; the 3d and 4f of Cr were also observed, referring to the least toxic Cr(III) species, unlike the carcinogenic Cr(VI). Furthermore, increased ECs power settings changed proportions between peaks of different binding energies, while nicotine concentration in vape liquids did not affect metal oxidation states. Moreover, metal oxidation states do not vary while transferred from the liquids to the aerosols. This study provides information regarding the potential toxicological effects of metals emitted from ECs.

Kapiamba et al., accepted. doi.org/10.1021/acs.chemrestox.1c00411