Effects of Switching to Electronic Cigarettes with and without Concurrent Smoking on Exposure to Nicotine, Carbon Monoxide, and Acrolein.

Concern has been raised about the presence of toxicants in electronic cigarette (EC) aerosol, particularly carbonyl compounds (e.g., acrolein) that can be produced by heating glycerol and glycols used in e-liquids. We investigated exposure to carbon monoxide (CO), nicotine (by measuring cotinine in urine), and to acrolein (by measuring its primary metabolite, S-(3-hydroxypropyl)mercapturic acid (3-HPMA) in urine) before and after 4 weeks of EC (green smoke, a "cig-a-like" EC, labeled 2.4% nicotine by volume) use, in 40 smokers. Thirty-three participants were using EC at 4 weeks after quitting, 16 (48%) were abstinent (CO-validated) from smoking during the previous week (EC only users), and 17 (52%) were "dual users." A significant reduction in CO was observed in EC-only users [-12 ppm, 95% confidence interval (CI), -16 to -7, 80% decrease) and dual users (-12 ppm, 95%CI, -19 to -6, 52% decrease). Cotinine levels also declined, but to a lesser extent (EC-only users: -184 ng/mg creatinine; 95% CI, -733 to -365, 17% decrease; and dual users: -976 ng/mg creatinine; 95%CI, -1,682 to -270, 44% decrease). Mean 3-HPMA levels had decreased at 4 weeks by 1,280 ng/mg creatinine (95%CI, -1,699 to -861, 79% decrease) in EC-only users and by 1,474 ng/mg creatinine (95%CI, -2,101 to -847, 60% decrease) in dual users. In dual users, EC use significantly reduced exposure to CO and acrolein because of a reduction in smoke intake. EC may reduce harm even in smokers who continue to smoke, but long-term follow-up studies are needed to confirm this. ©2015 American Association for Cancer Research.