E-cigarette Vapors with Common Ingredients Cause Lung Irritation and Mucus

David Palenski
24th January, 2024

E-cigarette Vapors with Common Ingredients Cause Lung Irritation and Mucus

Figure from study characterizing e-cigarette aerosols reveals that the common base liquid propylene glycol (PG) forms smaller particles than vegetable glycerin (VG) or a PG/VG blend, affecting how the aerosol deposits in an experimental airway model.

Image adapted from: Kim et al. / CC BY (Source)
E-cigarettes have become increasingly popular, particularly among young people, despite ongoing concerns about their health effects. While much attention has focused on nicotine and flavorings, the safety of the base liquids used in e-cigarettes – propylene glycol (PG) and vegetable glycerin (VG) – has remained less clear. These liquids are aerosolized and inhaled, and their impact on the airways wasn’t fully understood. A recent study from the University of Kansas Medical Center[1] investigated whether PG/VG, even without nicotine, can cause harm to the respiratory system. The study addressed a gap in knowledge regarding the potential dangers of e-cigarette ingredients beyond nicotine. Previous research has highlighted the rising rates of e-cigarette use, especially among adolescents, and the associated risks of respiratory problems like bronchitis and asthma[2][3]. However, it was unclear whether these effects were solely due to nicotine or also caused by the PG/VG base liquids themselves. The research aimed to determine if PG/VG could directly induce inflammation and impair the normal functioning of the airways. Researchers at the University of Kansas Medical Center used two models to investigate this: human bronchial epithelial cells (HBEC) grown in a laboratory setting, and live sheep. HBEC are the cells that line the airways and are directly exposed to inhaled substances. These cells were exposed to aerosols containing only PG/VG. In the sheep model, animals were exposed to the same aerosols, allowing researchers to observe effects in a living respiratory system. The study found that exposure to PG/VG aerosols significantly disrupted several key functions in the airways. In the HBEC, the activity of ion channels – tiny pores in cell membranes crucial for regulating fluid balance and mucus hydration – was reduced. Specifically, the function of CFTR and BK channels was impaired. These channels are vital for keeping the mucus lining of the airways properly hydrated, allowing it to effectively trap and clear out irritants and pathogens. The researchers also observed increased levels of inflammatory markers, such as interleukin-6 (IL6) and IL8, indicating an inflammatory response in the airways. Furthermore, the expression of MUC5AC, a gene responsible for producing a specific type of mucus, was increased, while the expression of MUC5B, another mucus-producing gene, was decreased. This imbalance can lead to changes in mucus consistency and impair its ability to clear the airways. The study also revealed that PG/VG exposure reduced the number of cells responsible for maintaining the airway lining and its ability to move mucus (cilia). In the sheep model, exposure to PG/VG aerosols led to increased levels of an enzyme called MMP-9, which breaks down proteins in the airway, and a thickening of the mucus. These findings build upon earlier observations that e-cigarette use is associated with respiratory symptoms[4][5]. The current study goes further by identifying PG/VG as a potential direct cause of these effects, even in the absence of nicotine. This suggests that the base liquids themselves contribute to airway inflammation and dysfunction. The increased mucus production and altered mucus composition observed in the study could explain some of the respiratory symptoms reported by e-cigarette users, such as coughing and shortness of breath. The study also supports the idea that e-cigarettes may not be a harmless alternative to traditional cigarettes, as the PG/VG component can independently cause respiratory harm.

MedicineHealthBiotech

References

Main Study

1) The combination of propylene glycol and vegetable glycerin e-cigarette aerosols induces airway inflammation and mucus hyperconcentration.

Published 23rd January, 2024

https://doi.org/10.1038/s41598-024-52317-8

Related Studies

2) Youth vaping: a review and update on global epidemiology, physical and behavioral health risks, and clinical considerations.

https://doi.org/10.1007/s00431-021-04220-x

3) Global youth vaping and respiratory health: epidemiology, interventions, and policies.

https://doi.org/10.1038/s41533-022-00277-9

4) Electronic Cigarette Use and Respiratory Symptoms in Adolescents.

https://doi.org/10.1164/rccm.201604-0804OC

5) E-cigarette use and adverse respiratory symptoms among adolescents and Young adults in the United States.

https://doi.org/10.1016/j.ypmed.2021.106766


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