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.