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. 2023 Jan 20;20(3):1908.
doi: 10.3390/ijerph20031908.

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

Nargiz Travis  1 , Marie Knoll  1 , Steven Cook  2 , Hayoung Oh  1 , Christopher J Cadham  3 , Luz María Sánchez-Romero  1 , David T Levy  1
Affiliations

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

Nargiz Travis et al. Int J Environ Res Public Health. .

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.

Keywords: chemical profiles; constituents; electronic cigarettes; toxicity; umbrella review; vaping.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
PRISMA flow diagram of the study selection process for the umbrella review.
See this image and copyright information in PMC

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