Researchers examined the effects of e-cigarette flavoring agents on human epithelium and found two common flavorings can have damaging effects on the functioning of cilia that line the human airway; cilia are found on 50-75% of airway epithelial cells and play key roles in sweeping out dust, mucus, and other particles from the airways.
Cilia keep the air entering the lungs clean and free of irritants for proper breathing, when not working well lung function deteriorates; chemical flavoring agents used in e-cigarettes were found to affect expression of genes encoding ciliary production and function.
Over 90% of the examined e-cigs contained diacetyl and 2,3-pentanedione flavorants and lesser amounts of other chemicals according to earlier research conducted by Joseph Allen. Diacetyl is a common flavoring agent that has not been linked to harmful effect through consumption, however inhalation is a different process.
Inhaling diacetyl has been indicated in available research to harm the lungs, causing bronchiolitis obliterans which is a severe lung condition first seen in workers who inhaled diacetyl while manufacturing microwave popcorn.
A few facilities substituted 2,3-pentanedione for diacetyl after danger of inhalation was reported, effects of inhaling these chemical have not been studied so far. Newer techniques were used in this study to examine how these chemicals affected epithelial cells arranged to simulate living human airway tissue.
After exposing human bronchial epithelium to theses chemicals for 24 hours a significant effect on gene expression was observed that resulted in poor ciliary synthesis and impaired function; effects were seen at low levels of inhalation which brings to question current safety limits for workers exposed to them. Currently there are no safety standards for e-cigarettes and users are not warned about the dangers of inhaling these chemicals.
