Footnotes

• Twitter @Joseph_GL_Lee

• Contributors Both authors conceptualised the paper. JGLL drafted the paper, and ES revised the paper. Both authors critically edited the paper and approved the final version.

• Funding Part of ES’s effort is supported by grant numbers R15ES032138 from the National Institute of Environment Health Sciences of the National Institutes of Health (NIH), R21CA239188 from the National Cancer Institute of NIH and the Center for Tobacco Products (CTP) of the U.S. Food and Drug Administration (FDA), and U54DA036105 from the National Institute on Drug Abuse of NIH and FDA.The content is solely the responsibility of the authors and does not necessarily represent the official views of NIH or the FDA.

• Competing interests ES is named on a patent for a smartphone app that that determines electronic cigarette device and liquid characteristics.

• Provenance and peer review Not commissioned; externally peer reviewed.