Between vapour and smoke? Prooxidant activity of electronic cigarette emissions
Electronic cigarettes (e-cigs) are considered among the most promising tools designed for the reduction of a potential harm derived from smoking. Nevertheless, debates exist over the scientific evidence for claims that e-cigs have no health-related ramifications. In this context, the purity of constituents of e-liquids, which are the solutions that are heated up and converted to an aerosol and inhaled by e-cig users, are in the spotlight. But more important are possible chemical changes of the e-liquid components in the e-cig atomiser and the formation of species potentially active towards biomolecules. The objective of this study was to examine such a possibility. In the present pilot work, we investigated the generation of prooxidants in emissions derived from e-cigs available on the local market (Russian Federation) through harnessing the redox-sensitive chemiluminescence probes. Delivering the nicotine vapour while using e-cigs proceeds without combustion products responsible for most of the damaging impacts in a human organism; however, heating the e-liquids may account for the generation of reactive oxygen species (ROS) and other prooxidants, which may trigger certain oxidative developments in vivo. Our study has revealed that heating the aerated mixtures of propylene glycol, glycerin and nicotine in e-cigs atomisers with coils from various metals indeed causes activation of molecules with the subsequent formation of reaction products, which exhibit prooxidant activity as manifested by the chemiluminescence derived from model oxidation processes. The plausible mechanisms of the formation of such reactants, as well as the possibility of the oxidative stress developments in e-cigs users are discussed. The results of this work should be of interest for improving the design of e-cigs and optimising their functioning.