Table 3.

Characteristics of systematic reviews on carcinogenic risks of e-cigarettes.

					Acute	Chronic
Pisinger & Dossing, 2014 [21]	Authors report no conflict of interest.	(1) Systematic and critical review of the existing literature on the health consequences of ECs and discuss the implications of our findings for public health. (2) To investigate how many of the published articles have a conflict of interest.	Through 24 August 2014	Human	Potentially carcinogenic product in human biological samples,	N/A	Experimental	Most studies included smokers,	One	N/A	N/A
Bozier et al., 2020 [18]	None declared	(1) To provide a comprehensive update of data on the potential health effects of ECs since the NASEM report. (2) To provide a focused discussion of the scientific literature that will help inform the general public, health-care practitioners, and policy makers of the effects of EC use on health.	February 2017 through May 2019	Human	Potentially carcinogenic compounds breath and in respiratory tract retention.	Potentially carcinogenic compounds in urine.	Experimental, observational, and case reports.	EC users. Non-smoking chronic users.	Two	Short-term use (no data on the duration) and long-term use (≥6 months).	N/A
Harrell et al., 2014 [19]	The authors report no conflicts of interests. One co-author reports to be receiving research support from a pharmaceutical company, which is also a manufacturer of a stop smoking medication.	To have a summary of the current, relevant literature on EC safety and efficacy.	Through November 2013	In vitro	Gene mutations (not specified whether acute or long-term).		Preclinical	Bronchial epithelial cells.	One	Exposure to EC vapor (no data on the duration).	N/A
NASEM, 2018 [16]	N/A	To evaluate the available evidence of the health effects related to the use of electronic nicotine delivery systems (ENDS) and identify future federally funded research needs.	Between 1 February 2017, and 31 August 2017	Human, animal, and in vitro	DNA damage, intermediate cancer endpoints (biomarkers).	N/A	Preclinical, observational, case reports.		Four humans, three in vitro studies.	Acute (minutes to hours) EC use or vapor exposure.	N/A
Ioakeimidis et al., 2016 [20]	N/A	To highlight the efficacy for smoking cessation and the potential hazards of EC use.	Through June 2015	In vitro	Changes in gene expression.	N/A	Not specified. Original studies as well as review articles and statements are included.	Bronchial cells	20 original studies and eight review articles and statements.	EC use (no data on the duration).	N/A

COI = conflict of interest; EC = electronic cigarettes; TC = traditional cigarettes; and N/A = not available.