Droplet size distribution of electronic cigarette aerosols

Abstract

Electronic cigarettes (EC), also called e-cigarettes, resemble tobacco cigarettes and produce aerosol by heating and vaporizing the e-liquid with or without nicotine. Now they are marketed as general consumer products rather than regulated as medical or pharmaceutical products. However, like conventional pharmaceutical inhalation devices such as nebulizers, ECs could produce aerosols into the respiratory tract by oral inhalation. Also, ECs are portable and flexible to be pharmaceutical inhalers. These deserve more concern whether ECs could be used technically for drug pulmonary delivery. This study collected the comprehensive information of ECs, including EC development, EC design and its components, main chemical ingredient in e-liquid and their relative toxicity, generated aerosol, EC performance, EC safety and the relative regulations in countries. This study was designed to investigate ECs from the viewpoint of inhalation development for drug, comparing with a jet nebulizer. In this study, the droplet sizes were measured by the laser diffractometer as aerodynamic size by volume. The cumulative distribution (Q3), the droplet size distribution, the intercepted droplet diameter at 10% (D10), 50% (D50), and 90% (D90) of cumulative percentage of different samples were measured in ECs and nebulizers with 3s measuring time. The flow rate was set to 2.00 L/min. The results indicated ECs could be a potential alternative for pulmonary drug delivery. The droplet size distributions in ECs were between 0.5-10μm in 3s measuring time. There were statistical differences of Q3, D10, D50 and D90 between EC and nebulizers. In D10, D50 and D90, the variability of droplet size in ECs was larger than that in the nebulizers and the time to reach a stable droplet size in the ECs were much longer than in the nebulizers. The D90 with different samples in the ECs were fluctuated. Though ECs could delivery drugs to the lung, the EC performance should be improved. There were many factors may affecting the aerosol generated from EC. It is necessary to focus on the potential safer excipients, technology of the EC manufacture and the strict guidelines on the safety evaluation including the leachable and extractable.