Levels of saliva cotinine in electronic cigarette users.

AIMS: To assess saliva cotinine levels in experienced users of e-cigarettes ('vapers').

DESIGN, SETTING AND PARTICIPANTS: An internet survey in 2011 and 2012, with collection of saliva vials by mail. Participants were 71 users of e-cigarettes enrolled mainly on websites and online forums dedicated to e-cigarettes.

MEASUREMENTS: Use of e-cigarettes, tobacco and nicotine medications. Collection of saliva by mail and analysis of cotinine by liquid chromatography-mass spectrometry.

FINDINGS: Most participants (89%) were former smokers, most (92%) were using e-cigarettes daily, had been using e-cigarettes for 12 months on average and puffed a median of 150 times per day on their e-cigarettes [mean = 220 puffs/day, 95% confidence interval (CI) = 169-271]. The median concentration of nicotine in refill liquids was 16 mg/ml (mean = 16.4, 95% CI = 14.5-18.3). In the 62 e-cigarette users who, in the past 5 days, had not used any tobacco or nicotine medications, the median cotinine level was 353 ng/ml (mean = 374, 95% CI = 318-429), the correlation between cotinine and nicotine concentration in e-liquids was r = 0.33 (P = 0.013), and the correlation between cotinine and the number of cigarettes smoked per day before quitting smoking was r = 0.48 (P < 0.001).

CONCLUSIONS: At least some experienced users of electronic cigarettes appear to be able to gain as much nicotine from those products as do cigarette smokers.