E‑Liquid and Aerosol Characterization of Popular Disposable E‑Cigarettes

Disposable electronic cigarettes are one of the most popular forms of nicotine consumption among both adults and adolescents. Yet, e-liquid composition and the inhaled aerosol emissions from these devices are under-characterized. This work investigated 25 disposable e-cigarettes of various flavors from four popular brands (Flum Pebble, Elf Bar, Esco Bars, and Geek Bar) using a combination of gas chromatography, mass spectrometry, and liquid chromatography, accurate mass spectrometry. We quantified (1) e-liquid composition, including concentration and identity of added organic acids, concentration and R/S enantiomeric identity of nicotine, and the flavor and coolant content, and (2) aerosol mass formation and aerosolized carbonyl species formed in the vaping process. Of the 25 devices tested, 10 (40%) had significantly lower nicotine concentration compared to their labeled nicotine concentration. All studied devices contained the natural (S)-(-)-nicotine enantiomer. Benzoic acid was the major organic acid in all products; however, seven products across all brands also contained notable concentrations of levulinic acid. The benzoic acid to nicotine molar ratios varied greatly (range of 0.4-4) with no clear correlation to the brand or flavor profile. All products examined featured high concentrations of the synthetic coolant WS-23, comprising between 1% and 7% of the e-liquid. The flavor chemicals vanillin, ethyl maltol, triacetin, and (3Z)-3-hexen-1-ol were found in most devices. Concentrations of six additives (WS-23, WS-3, vanillin, ethyl maltol, menthol, and limonene) exceeded the threshold for toxic effects. Both the e-cigarette design and e-liquid formulation affected carbonyl yields in the aerosol. Interestingly, aerosol mass production was inversely correlated with carbonyl yields. Carbonyl yields were not found to correlate to the flavor additive or nicotine concentration in the tested devices. The Esco Bar brand produced the greatest yield of harmful or potentially harmful carbonyls in the aerosol, while Flum Pebble produced the least, often with high variability both between and within brands.