Electronic cigarette nicotine flux, nicotine yield, and particulate matter emissions: impact of device and liquid heterogeneity.

INTRODUCTION: Electronic cigarettes (ECIGs) heat a nicotine-containing liquid to produce an inhalable aerosol. ECIG power (wattage) and liquid nicotine concentration are two factors that predict nicotine emission rate ("flux"). These factors can vary greatly across devices and users. The purpose of this study was to examine ECIG device and liquid heterogeneity in "real world" settings and the association with predicted nicotine flux, nicotine yield, and total particulate matter (TPM) emissions.

METHODS: Past 30-day ECIG users (n=84; mean age=23.8 years [SD=9.6]) reported device and liquid characteristics. Device power was measured via multimeter, device display screens, or obtained via labeling. Liquid nicotine concentration was obtained via labeling or through chemical analysis. Predicted nicotine flux, nicotine yield, and TPM associated with 10 four-second puffs were calculated for participants' primary devices.

RESULTS: Participants' primary devices were box mods (42.9%), disposable vapes (20.2%), and pod mods (36.9%). Most participants (65.5%) reported not knowing their primary device wattage. Rebuildable/box mods had the greatest power range (11.1-120.0 watts); pod mod power also varied considerably (4.1-21.7 watts). Unlike device wattage, most participants (95.2%) reported knowing their liquid nicotine concentration, which ranged from 3.0-86.9 mg/ml (M=36.0, SD=29.3). Predicted nicotine flux varied greatly across products (range=12.0-160.1 μg/sec, M=85.6 μg/sec, SD=34.3). Box mods had the greatest variability in wattage and predicted nicotine flux, nicotine yield, and TPM yield.

CONCLUSIONS: ECIG device and liquid heterogeneity influences nicotine and other toxicant emissions. Better measurement of ECIG device and liquid characteristics is needed to understand nicotine and toxicant emissions and to inform regulatory policy.

IMPLICATIONS: Electronic cigarette device and liquid heterogeneity causes great variability in nicotine flux and toxicants emitted. These data demonstrate the need to examine device and liquid characteristics to develop empirically-informed, health-promoting regulatory policies. Policies may include setting product standards such that electronic cigarette products cannot 1) have nicotine fluxes much greater than that of a cigarette to decrease risk of dependence, 2) have nicotine fluxes that are very low and thus would have minimal appeal to cigarette smokers and may serve as starter products for youth or non-tobacco users, and 3) emit large amounts of particulate matter and other toxicants.