Inhalation Toxicology of Vaping Products and Implications for Pulmonary Health

Abstract

E-cigarettes have a liquid that may contain flavors, solvents, and nicotine. Heating this liquid generates an aerosol that is inhaled into the lungs in a process commonly referred to as vaping. E-cigarette devices can also contain cannabis-based products including tetrahydrocannabinol (THC), the psychoactive component of cannabis (marijuana). E-cigarette use has rapidly increased among current and former smokers as well as youth who have never smoked. The long-term health effects are unknown, and emerging preclinical and clinical studies suggest that e-cigarettes may not be harmless and can cause cellular alterations analogous to traditional tobacco smoke. Here, we review the historical context and the components of e-cigarettes and discuss toxicological similarities and differences between cigarette smoke and e-cigarette aerosol, with specific reference to adverse respiratory outcomes. Finally, we outline possible clinical disorders associated with vaping on pulmonary health and the recent escalation of acute lung injuries, which led to the declaration of the vaping product use-associated lung injury (EVALI) outbreak. It is clear there is much about vaping that is not understood. Consequently, until more is known about the health effects of vaping, individual factors that need to be taken into consideration include age, current and prior use of combustible tobacco products, and whether the user has preexisting lung conditions such as asthma and chronic obstructive pulmonary disease (COPD).

Keywords: EVALI; cannabinoid; cannabis; e-cigarettes; inflammation; lipoid pneumonia; lung injury; respiratory; vaping; vitamin E acetate.

Figure 1

The known and unknown health effects of vaping in comparison to cigarette smoke. The major toxic effects of compounds found in cigarette smoke (Right lung) and in vaping aerosols (Left lung) are lunginflammation, oxidative stress, cell death, impaired immune response, DNA damage and epigeneticmodifications. The respiratory diseases caused by cigarette smoke (lung cancer, COPD [emphysema and/orobstruction of airways]) are not yet established to be caused by vaping (represented by question marks in theleft lung). The presence of lipid-laden macrophages is a feature predominantly associated with vaping products containing THC and has been a feature of EVALI.