Table 2.

Unique and shared constituents of mainstream cigarette smoke (MCS) and electronic cigarette (e-cig) aerosol

Mixture	Constituent	Reference(s)
MCS	Formaldehyde	Kaden et al. [62], Baker [63]
	Acetaldehyde	WHO [64]
	Crotonaldehyde	van Andel et al. [65]
	Acrolein	Alwis et al. [66]
	Nicotine	US FDA [2]
	Metals	US FDA [2]
	PM	UD FDA [2]
E-cig aerosol	Formaldehyde	Conklin et al. [37], Ogunwale et al. [41••], Rubinstein et al. [67]
	Acetaldehyde	Conklin et al. [37], Ogunwale et al. [41••], Rubinstein et al. [67]
	Acrolein	Conklin et al. [37], Ogunwale et al. [41••], Rubinstein et al. [67], Goniewicz et al. [68]
	Nicotine	Conklin et al. [37], Hutzler et al. [38], Goniewicz et al. [39], Mobarrez et al. [69]
	Metals	Hess et al. [70], Olmedo et al. [71], National Academies [47••]
	PM	Lee et al. [72], National Academies [47••]
	PG:VG	Conklin et al. [37], Bertholon et al. [40]
	Flavorings	Bertholon et al. [40], Ogunwale et al. [41••]

E-cig electronic cigarette, MCS mainstream cigarette smoke, PG:VG propylene glycol:vegetable glycerin, PM particulate matter, US FDA US Food and Drug Administration, WHO World Health Organization