Chemical Profiles and Toxicity of Electronic Cigarettes: An Umbrella Review and Methodological Considerations

Abstract

Background: Electronic cigarettes (ECs) are often marketed as a safer alternative to combustible tobacco products. The global EC market has rapidly expanded since their introduction, creating an urgent need for research describing the toxicity and chemical composition of ECs. We conducted an umbrella review to summarize the evidence from existing systematic reviews (SRs). Methods: The search for SRs was conducted across four electronic databases through 25 January 2022. Methodological quality was assessed using the AMSTAR-2 quality appraisal tool. Results: Twenty-five SRs were included in our umbrella review. Chemical profiles widely varied across studies included in the reviews, which was mainly attributed to the lack of standardized protocols investigating the constituents, and differences in EC devices and e-liquids tested. Metals were more abundant in some EC aerosols than cigarettes, while carbonyls were typically found at lower levels. There was consistent evidence of in vitro toxicity from EC aerosol and e-liquid exposure. AMSTAR-2 revealed important limitations across reviews. Conclusions: While most reviews concluded that ECs were likely less harmful than cigarettes, there was hesitancy to draw clear conclusions due to variable analytical procedures and inconsistent findings among the included studies. Future SRs with improved methodology and reporting are needed to adequately inform tobacco regulatory actions.

Oral health risks in users of new generation nicotine/tobacco products (NGPs): Systematic review and qualitative meta-analyses

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E-cigarettes – their use and harmfulness. A brief summary of current scientific knowledge

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Harmful effects of electronic cigarette on oral soft tissues mediated by dysbiosis: State of the art

“…While e‐cigarettes are often perceived as a less harmful alternative to traditional cigarettes (Marques et al, 2021; Travis et al, 2023), a cautious approach is warranted when assessing the comparative harm between electronic and traditional cigarettes. The harmful effects on oral soft tissues associated with the use of e‐cigarettes discussed in this article have biological plausibility in their pathogenesis related to dysbiosis.…”