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).

An update on controversies in e-cigarettes

“…122 liquids studied contained substances having some level of hazard/risk of danger according to the globally harmonised classification system for respiratory irritants [25] , in flagrant breech of European Union regulations. With some devices there is variability in the temperature that heats the liquid, which can reach 250 °C to create the aerosol [40] . It is unsurprising that burn and blast injuries have resulted from malfunctioning of these devices [41] , [42] .…”

“…occupational asthma due to inhaled flour in bakers (who are mostly able to eat bread without problems) [44] ; asthma caused by Thiamine when inhaled (in the production of breakfast cereals) [44] . Long-term exposure to PG has been found to induce and exacerbate multiple allergic symptoms in children [127] Acrolein (a suspected carcinogen) is generated from vaporising the humectant glycerine [2] Ethylene glycol (EG), toluene, and 1,3-Propanediol, polyethylene glycol 400 (PEG 400), medium chain triglycerides (MCT) [40] . Traces Commonly added to cannabis-based vaping products [40] EG is an odourless, clear, and viscous liquid commonly used as an industrial solvent and as an antifreeze The health consequences of long-term exposure to EG and other residual solvents from e-cigarettes have not been investigated.…”

“… Long-term exposure to PG has been found to induce and exacerbate multiple allergic symptoms in children [127] Acrolein (a suspected carcinogen) is generated from vaporising the humectant glycerine [2] Ethylene glycol (EG), toluene, and 1,3-Propanediol, polyethylene glycol 400 (PEG 400), medium chain triglycerides (MCT) [40] . Traces Commonly added to cannabis-based vaping products [40] EG is an odourless, clear, and viscous liquid commonly used as an industrial solvent and as an antifreeze The health consequences of long-term exposure to EG and other residual solvents from e-cigarettes have not been investigated. EG is a respiratory irritant and may be associated with greater toxicity compared with conventionally used VG and PG Flavourings ( The concept of GRAS when eaten but not inhaled also applies to flavourings).…”

“…The increase is accelerating; double flavour labels available on websites rose from 7764 in 2013–2014 to 15586 in 2016–2017 [129] . Also many e-cigarette products contain more than one flavourant (average is approximately 6), and those with sweet flavours contain more chemicals compared with tobacco and menthol flavoured liquids [40] . Diacetyl ((2,3-butanedione) (DA) Acetyl propionyl (AP) 2,3-pentanedione Cinnamaldehyde (cinnamon) Benzaldhyde (cherry) DA and AP are present in 74.2% of the samples out of 159 tested “sweet” e-liquids and aerosols from 36 manufacturers and retailers from 7 countries [130] DA occurs naturally in, for example, butter and beer Classified by the FDA as GRAS as a food additive Concentrations released into the air are highly dependent on temperature Overwhelming evidence of inhalational toxicity DA was the major volatile compound present in the plant where bronchiolitis obliterans was first described in microwave popcorn workers [131] .…”

Spontaneous Pneumothorax - Therapeutic Attitude - Brief Review

“…Some specialists consider that the main risk factor is smoking tutu cigarettes [5]. The literature mentions the occurrence of pneumothorax in patients who smoked tobacco associated with cannabis [3,6], e-cigarette smokers [7], air pollution in major cities [8], and other toxic factors [9]. Smoking acts on the extracellular pulmonary matrix through several mechanisms, but the release of oxidizing free radicals inhibits alpha-1-antitrypsin and alters the alveolar membrane [2].…”