Table 2.

Comparison of toxin levels in conventional and electronic cigarettes

Toxin	Conventional cigarette (μg/cigarette in mainstream smoke)	Electronic cigarette (μg per 15 puffs)	Average ratio (conventional:electronic)
Carbonyl compounds
formaldehyde	1.6–52	0.20–5.61	9
acetaldehyde	52–140	0.11–1.36	450
acrolein	2.4–62	0.07–4.19	15
Toluene	8.3–70	0.02–0.63	120
Nitrosamines
N′-nitrosonornicotine	0.005–0.19	0.00008–0.00043	380
NNK	0.012–0.11	0.00011–0.00283	40

Definition of abbreviation: NNK = 4-(methylnitrosoamino)-1-(3-pyridyl)-1-butanone.

Adapted by permission from Reference 40.