Dangerous levels of harmful chemicals in electronic cigarette (e-cigarette) aerosols were reported by several studies, but variability in e-cigarette design and use patterns, and a rapid development of new devices, such as JUUL, hamper efforts to develop standardized testing protocols and understand health risks associated with e-cigarette use. In this study, we investigated the relative importance of e-cigarette design, power output, liquid composition, puff topography on e-cigarette emissions of carbonyl compounds, carbon monoxide (CO), and nicotine. Four popular e-cigarette devices representing the most common e-cigarette types (e.g., cig-a-like, top-coil, ‘mod’, and ‘pod’) were tested. Under the tested vaping conditions, a top-coil device generated the highest amounts of formaldehyde and CO. A ‘pod’ type device (i.e., JUUL) emitted the highest amounts of nicotine, while generating the lowest levels of carbonyl and CO as compared to other tested e-cigarettes. Emissions increased nearly linearly with puff duration, while puff flow had a relatively small effect. Flavored e-liquids generated more carbonyls and CO than unflavored liquids. Carbonyl concentrations and CO in e-cigarette aerosols were found to be well correlated. While e-cigarettes emitted generally less CO and carbonyls than conventional cigarettes, daily carbonyl exposures from e-cigarette use could still exceed acute exposure limits, with the top-coil device potentially posing more harm than conventional cigarettes.

Several studies have shown the presence of aldehydes (i.e., formaldehyde, acrolein) in mainstream emissions of some e-cigarettes. For this reason, concerns have been raised regarding potential toxicity. The purpose of this research was to measure levels of carbonyls in exhaled breath of e-cigarette users during “vaping” sessions and estimate the respiratory tract (RT) uptake of specific aldehydes, including formaldehyde and acetaldehyde. We measured concentrations of 12 carbonyls in e-cigarette aerosols produced directly by e-cigarettes and in the exhaled breath of 12 participants (19 sessions). Carbonyls were sampled on 2,4-dinitrophenylhydrazine (DNPH) cartridges and analyzed with high performance liquid chromatography (HPLC) coupled with a UV/Vis photodiode detector. We found that in most cases, levels of aldehydes and methyl ethyl ketone (MEK) were significantly higher (2–125 times) in exhaled e-cigarette breaths than in pre-exposed breath. Exposure levels for the most abundant individual carbonyls in e-cigarette emissions—formaldehyde, acetaldehyde, acrolein—were between the limit of quantification (LOQ) and 24.4 μg·puff⁻¹. The mean retention of formaldehyde in the respiratory tract was 99.7 ± 0.9% for all participants, while acetaldehyde retention was 91.6 ± 9.9%. Within the limitation of a small number of participants, our results showed that there is an increase in breath carbonyls during e-cigarette use.