Particulate Matter from Electronic Cigarettes and Conventional Cigarettes: a Systematic Review and Observational Study.

OBJECTIVES: The aim of this study is to review the literature on the composition of aerosols from electronic cigarettes (e-cigarettes) originated by human vaping and to describe the emission of particulate matter ≤ 2.5 μm in diameter (PM(2.5)) from conventional and e-cigarettes at home in real-use conditions.

METHODS: We conducted a systematic literature search in PubMed and Web of Science. We measured PM(2.5) in four different homes: one from a conventional cigarette smoker, one from an e-cigarette user, and two from non-smokers.

RESULTS: The review identified eight previous investigations on the composition of aerosols from e-cigarettes originated by human vaping and indicated that emissions from e-cigarettes can contain potential toxic compounds such as nicotine, carbonyls, metals, and organic volatile compounds, besides particulate matter. In the observational study, the PM(2.5) median concentration was 9.88 μg/m³ in the e-cigarette user home and 9.53 and 9.36 μg/m³ in the smoke-free homes, with PM(2.5) peaks concurrent with the e-cigarette puffs.

CONCLUSION: Both the literature review and the observational study indicate that e-cigarettes used under real-conditions emit toxicants, including PM(2.5). Further research is needed to characterize the chemicals emitted by different types of e-cigarettes and to assess secondhand exposure to e-cigarette aerosol using biological markers.