“The effects of the various chemical components of e-cigarette vapour on lung tissue are largely unknown,” said lead author Temperance Rowell, a graduate student in the Cell Biology and Physiology Department of the University of North Carolina at Chapel Hill.
“In our study using human lung epithelial cells, a number of cell viability and toxicity parameters pointed to 5 of 13 flavours tested showing overall adverse effects to cells in a dose-dependent manner,” Rowell said.
In the study, cultured human airway epithelial cells were exposed to various doses of the 13 e-cigarette liquid flavours for 30 minutes or 24 hours.
During the 30 minute exposure test, the flavours Hot Cinnamon Candies, Banana Pudding (Southern Style), and Menthol Tobacco elicited a dose-dependent calcium response and were toxic to the cells at higher doses.
During the 24 hour exposure test, these same three flavours decreased cell proliferation and cell viability in a dose-dependent manner.
The toxic effects of these flavourings were not seen with either nicotine or the e-liquid vehicle, which consisted of propylene glycol and vegetable glycerin, researchers said.
“The specific chemical components underlying the toxic effects of these e-cigarette flavours on cell viability, proliferation, and calcium signalling in airway epithelia are undergoing further study in our lab,” said Rowell.
“Given the increasing popularity of flavoured e-cigarettes, a better understanding of their ingredients, the potential health risks of these ingredients, and the causes of these risks is urgently needed,” she said.
The research was presented at the 2015 American Thoracic Society International Conference in Colorado.