Statistical considerations The primary exposure variable will be e-cigarette exposure; the primary outcome variable will be plasma and BAL biomarkers of injury and inflammation. Given that early studies of electronic cigarettes suggest that they may be associated with inflammation, we have used BAL absolute neutrophil count, a key marker of inflammation, to inform our sample size. Based on data from controls in our prior study, a cohort of 10 e-cigarette users and 10 controls should be able to detect a minimal difference of 7.09 x 105 cells in the BAL after LPS inhalation between groups with 80% power using Wilcoxon Rank Sum testing. Of note, this is similar to the difference we observed between smokers and non-smokers after LPS in our prior study [7]. Additionally, we will compare biomarkers of inflammation and injury in electronic cigarette users to those from conventional cigarette smokers using Wilcoxon Rank Sum testing. All data will be analysed using STATA 13.1 (StataCorp LP, College Station, TX).