Electronic cigarettes: overview of chemical composition and exposure estimation

Abstract

BackgroundElectronic cigarettes (e-cigarettes) are advertised to tobacco users as a tool to decrease cigarette consumption and to reduce toxic exposure associated with conventional tobacco smoking. Little is known about the compounds contained in such products, their exposure and long-term health effects.MethodsNMR spectroscopy was used to ascertain the content of several constituents of e-cigarette liquids including nicotine, solvents and some bioactive flavour compounds. Risk assessment was based on probabilistic exposure estimation and comparison with toxicological thresholds using the margin of exposure (MOE) approach.ResultsIn 54 samples of e-cigarette liquids, the average nicotine content was 11 mg/ml. Only 18 from 23 samples were confirmed as nicotine-free samples and in one e-cigarette liquid nicotine was not detected while being declared on the labelling. Major compounds of e-cigarette liquids include glycerol (average 37 g/100 g), propylene glycol (average 57 g/100 g) and ethylene glycol (average 10 g/100 g). Furthermore, 1,3-propanediol, thujone and ethyl vanillin were detected in some samples. The average exposure for daily users was estimated as 0.38 mg/kg bw/day for nicotine, 8.9 mg/kg bw/day for glycerol, 14.5 mg/kg bw/day for 1,2-propanediol, 2.1 mg/kg bw/day for ethylene glycol, and below 0.2 mg/kg bw/day for the other compounds. The MOE was below 0.1 for nicotine, but all other compounds did not reach MOE values below 100 except ethylene glycol and 1,2-propanediol.ConclusionsNMR spectroscopy is a useful and rapid method to simultaneously detect several ingredients in e-cigarette liquids. From all compounds tested, only nicotine may reach exposures that fall into a high risk category with MOE <1. Therefore, e-cigarette liquid products should be subjected to regulatory control to ensure consistent nicotine delivery. Solvents with more favourable toxicological profiles should be used instead of ethylene glycol and 1,2-propanediol, which may fall into a risk category with MOE < 100.

Trace Metals Derived from Electronic Cigarette (ECIG) Generated Aerosol: Potential Problem of ECIG Devices That Contain Nickel

“…While comparing vaping to smoking might seem incommensurable, a reasonable attempt at comparison must be made in order to gauge the degree of safety of one inhalation behavior over the other, especially since vaping is deemed by many to be a safer alternative to smoking, despite the fact that nicotine is internalized in both behaviors. To illustrate this point, a recent study by Hahn et al (2014), found nicotine, in a number of E-liquids, to be the only constituent of major concern.…”

Will chronic e-cigarette use cause lung disease?

“…Additionally, tobacco smoke, as well as aldehydes, cadmium, and oxidative stress, also affect plasma membrane proteins such as the cystic fibrosis transmembrane conductance regulator (CFTR) (25,33,70,137), which is required for fluid secretion in the lung (35,60). In contrast, e-liquids (the flavored liquids that are heated to form the E-Cig vapor) are thought to be much simpler and ostensibly contain nicotine (ϳ6 -18 mg/ml) in a liquid vehicle (typically propylene glycol and/or glycerin), along with sweeteners and flavorings (65).…”

A decade of e-cigarettes: Limited research & unresolved safety concerns

“…Chemical analyses of the e-liquids and popular e-cigarettes brands revealed high variability in the nicotine content (between refills) and nicotine delivery efficiency (between nominally identical e-cigarette models). Significant inconsistencies between the nominal (labeled) and the actual nicotine content of the e-liquids have been reported by a host of investigators (Etter et al, 2013; Famele et al, 2015; Goniewicz et al, 2015; Goniewicz et al, 2014a; Hahn et al, 2014; Lisko et al, 2015) These also include the presence of nicotine in “nicotine-free e-liquids” as well as variations (up to 12%) in nicotine concentration (Goniewicz et al, 2014a) and pH (Lisko et al, 2015) within the same batch of e-liquids. In addition to nicotine and flavoring agents the presence of other toxic compounds (especially carcinogens) have been recently reported.…”