Unlike conventional tobacco products, e-cigarette use (i.e. vaping) does not involve tobacco combustion, suggesting that the potential for harm may be reduced. E-cigarette liquids contain a propylene glycol/vegetable glycerin (PG/VG) base, nicotine and flavorings. However, the long-term health effects of exposing human lungs to vaped e-liquids are largely unknown. We performed research bronchoscopies on healthy non-smokers, smokers and vapers to obtain bronchial epithelia and bronchoalveolar lavage (BAL) under UNC ethics board-approved conditions. We also exposed primary bronchial epithelial cultures and immune cells to e-cigarette components in vitro. Bronchoscopy revealed visually abnormal airways in chronic vapers and we identified ~300 proteins that were differentially expressed in smokers and vapers, with only 79 proteins being commonly altered in both groups. The mucin MUC5AC, and VAMP8, which facilitates mucin secretion, were upregulated in both vapers and smokers. Exposure of epithelia to aerosolized PG/VG, but not nicotine, was sufficient to increase MUC5AC abundance in vitro. Excessive proteolysis occurs with chronic tobacco use and is causative for bronchiectasis and emphysema. Neutrophil elastase, MMP-2 and MMP-9 activities and protein levels were equally elevated in both vapers and smokers BAL relative to non-smokers. We also found that exposure of neutrophils and macrophages to nicotine ex vivo caused dose-dependent increases in protease release. We conclude that vaping induces nicotine-dependent and independent effects on the lung, alters both epithelia and immune cells and disrupts the protease-antiprotease balance, which may place vapers at risk of developing chronic lung disease. These data indicate that vaping may not be safer than tobacco smoking.