Footnotes

• Contributors ES, AT and NP developed the survey and conducted the cognitive interviews to test the survey. ES conducted the data analysis and wrote the first draft of the manuscript. SS, JP, AT and NP provided critical review of the manuscript and all authors approved the final version.

• Funding This research was supported by the National Institute of Environmental Health Sciences (grant number R15ES032138) of the National Institutes of Health (NIH). ES’s effort is also supported by the National Institute on Minority Health and Health Disparities (grant number P50MD017319) and by the National Institute on Drug Abuse of the National Institutes of Health and the Center for Tobacco Products (grant number U54DA036105) of the US Food and Drug Administration (FDA).

• Disclaimer The content is solely the responsibility of the authors and does not necessarily represent the views of the NIH or the FDA.

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

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

• Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.