A new study suggests that the flavorings in e-cigarettes are associated with damage at the cellular level. Researchers from Roswell Park Cancer Institute in Buffalo, New York published findings online in the BMJ journal Tobacco Control showing that some flavors were more harmful than others. The study also found that increased battery voltage was linked to greater toxicity, a finding that echoes previous studies. Authors looked at a total of five flavors.
In this study, bronchial cells (cells that are in the respiratory tract) exhibited the most toxicity when exposed to strawberry flavoring. Significant cell toxicity was observed with menthol, coffee and strawberry while piña colada and tobacco flavors were linked to less cytotoxicity. Researchers did not analyze the chemical composition of the flavoring compounds.
“Our data indicate that combinations of product, voltages, and flavorings exist that are cytotoxic to airway epithelial cells,” the authors said. “Since our study focused on the acute effects of flavored electronic nicotine delivery systems (ENDS) products, our observations require verification in chronic exposure models, more relevant to regular use of ENDS products.”
Study author Maciej L. Goniewicz, PhD, PharmD, says more testing needs to be done to get a better understanding of the chemicals in e-cigarette flavorings. “Many of these flavorings have been widely used in foods and cosmetics, but they have never been tested when inhaled. With the rise of e-cigarette popularity, we need to be cautious and develop accurate and fast screening methods for inhalation effects of such flavorings.” she told MedPage Today.
The researchers utilized a unique testing method to conduct their study. They directly exposed bronchial cells to e-cigarette aerosol using air-liquid interface culture (ALI) with a smoking machine. They exposed cells to different ENDS products or a tank system pre-filled with liquids of different flavors and nicotine concentrations. The battery voltage was also varied. Researchers used ALI to expose bronchial epithelial cells to ENDS aerosol, tobacco smoke and air (as a control). Six different ENDS products were used in the study.
Compared to controls (cells exposed to air), cells exposed to ENDS aerosol had reduced metabolic activity and increased released of several interleukins and chemokines, molecules that play an important role in immune response. Tobacco smoke was more damaging than most e-cigarette products. The study also found that toxicity varied significantly depending in the type of e-cigarette product, battery output voltage and flavor.
“Interestingly, it was not nicotine or nicotine solvents, but other additives in e-cigarettes that affected respiratory cells used in our study,” said Goniewicz.
The authors stated “Further studies are needed to investigate the cytotoxic effect of single flavoring chemicals in ENDS liquids, combinations of these ingredients, and the effects of alternate ENDS liquid products with the same flavor name. Our study indicates that testing toxicity of ENDS products should not be limited to individual flavoring chemicals, since the ENDS liquids are complex mixtures, and other product features (e.g., voltage) contribute to overall toxicity of ENDS aerosol.”