Song MA, Reisinger SA, Freudenheim JL, et al. - Researchers performed this pilot study to determine how electronic cigarettes (e-cigs) without nicotine or flavors influence the human lung. Among 30 never-smokers, who were randomly assigned to a 4-week intervention with the use of e-cigs consisting of only 50% propylene glycol (PG) and 50% vegetable glycerine or to a no-use control group, serial bronchoscopies were performed over 4 weeks. Comparison between control and e-cig groups revealed no significant variations in alterations of bronchoalveolar lavage inflammatory cell counts or cytokines between baseline and follow-up. A significant correlation of change in urinary PG as a marker of e-cig use and inhalation, with change in cell counts (cell concentrations, macrophages, and lymphocytes) and cytokines (IL8, IL13, and TNFα), was seen in the intervention but not the control group, though the absolute magnitude of changes was small. Findings revealed no significant alterations in mRNA or miRNA gene expression. This study represents the first experimental demonstration of the influence of e-cig use on inflammation in the human lung among never-smokers.