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Common e-cigarette chemicals: Are they safe?

e-cigarette chemical safety

With the increased use of e-cigarettes and/or vapes by high school students, authorities are trying to determine what if any safety these devices contain. In addition, the FDA is addressing the need for stricter regulation of who is allowed to purchase both devices.


A growing body of research indicates that flavors play a critical role in attracting and retaining smokers into the e-cigarette category. The market for e-cigarettes is expanding rapidly, thus responsible selection and inclusion levels of flavorings in e-liquids must be guided by toxicological principles. Just because a flavoring is admissible for consumption doesn’t mean it is okay to be inhaled as part of e-liquid. Future study should concentrate on the potential damage certain flavorings could cause once they are heated and inhaled.

Broader assessments of these substances are needed to keep up with the rapidly expanding market (Stevenson et al, 2019). Aldehydes in cigarette smoke impair mitochondrial function and reduce ciliary frequency leading to reduced mucus clearance.

This study found that vaped aerosols and e-cigarette liquids impaired mitochondrial respiration. It was felt from this study that e-cigarette users could be at increased risk of respiratory infections. This conclusion comes because normal ciliary motility and mucus clearance are both essential defenses for the respiratory system. And both of these functions are impacted adversely by e-cigarette or vape use (Clapp, et al. (2019).

What is the big deal?
In your lungs, there are little antennae-like protuberances called cilia. They are present on 50-75% of the cells that line the human airways. They may play a key role in keeping the airways clear of mucous and dirt and allows people to breath easy without irritation. Impaired function of cilia has been linked with lung diseases such as asthma and COPD. Chemicals used to flavor e-cigarettes are frequently used by little study has been done to track the impact of these same chemicals have on the human body.

This study was the first to look at the impact of flavorings have on epithelial cells in the lungs. The recent rise of use among school-age children has led to the US Surgeon General to label youth use of e-cigarettes as an epidemic.

Scientific studies have been done on potential health effects of e-cigarettes and the many chemicals associated with their use have not kept pace with the rise in use. One such flavoring, diacetyl, is commonly used to give butter flavoring in microwave popcorn but is dangerous when inhaled. It has been linked with a disorder called bronchiolitis obliterans-a lung disease dubbed ‘popcorn lung’ because it first appeared in workers who inhaled the artificial butter flavor in the processing plants of microwave popcorn. Once this was identified a new chemical was substituted. New research, however, has found that both substances cause changes in the cilia and impair their function after even just 24-hour exposure (Park et al, 2019).

Tobacco versus e-cigarettes

Tobacco smoking is the most preventable cause of morbidity and mortality. For many, the inhaled aerosols of e-cigarettes are thought to be much safer. In truth, they contain numerous potential toxicities, some that are dangerous to health with long-term use. E-cigarettes may be safer than tobacco products, but repeated and prolonged exposure to their aerosols had its own considerable potential risk. In the US the incident of e-cigarette consumption has increased dramatically and health concerns are focused especially on young people.

Originally e-cigarettes were devised to look much like tobacco cigarettes but they have since been altered to improve rechargeable batteries and deliver more nicotine. Inhaled vapors can contain chemicals that while they have been approved for consumption (like vanilla or cinnamon), there has been little research done to see how they react when inhaled. In addition to chemicals, some e-cigarettes have been known to release cadmium, nickel, chromium or tin from the atomizers in the vapors. Newer e-cigarettes are often now made using stainless steel to minimize this exposure.

Many high school students who use e-cigarettes inhale less controlled high-dose nicotine quantities by dripping refill liquid directly onto the atomizer. Vapes, another form of the e-cigarette, can be adjusted so nicotine level can be set by the user at whatever level they choose. E-cigarettes have an impact on public health that is presently uncertain. The FDA is presently drawing a closer look at e-cigarettes. Just because on the surface they are safer than tobacco that doesn’t mean they are any less dangerous (Tegin et al, 2018).

The damage done to the body

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Alveolar macrophages are the most abundant immune cells in the lungs. They are located on the luminal surface of the alveolar space. They are first line to attach incoming pathogens and pollutants. They also play a role in regulating inflammatory reactions in the lung. And they are important dead cells like neutrophils from the lungs. Vaping may increase the cytotoxic effects of e-cigarette liquid or increase the toxic effects on the cells in the lungs.

Electronic nicotine delivery systems were introduced a decade ago and since then inhalation of e-cigarette vapor or vaping has risen in both smokers and ex-smokers. While they may be a useful tool to reduce traditional tobacco smoking for many they are simply replacing tobacco nicotine for e-cigarette nicotine. Recent studies have predominantly focused on the effects on the lungs. These studies have shown chronic exposure to unvaped fluid increased airway reaction and caused lung tissue degradation.

The study also found that continued exposure to e-cigarette vapor condensate led to an increase in cell death and necrosis when compared to the controls. This study validated the studies that show human alveolar macrophage responses to e-cigarette vapor condensate and identifies dose-dependent toxicity on the cells of the lungs. In addition, they found that after exposure to e-cigarette liquid, response to bacteria in the lungs was seen in both liquids with nicotine and liquid without nicotine.

They do acknowledge that because their study used unflavored liquids, these additives could exponentially increase the detrimental effects of e-cigarettes and their liquids (Scott et al, 2018).

In general, e-cigarettes often contain things such as propylene glycol and glycerol mixed with concentrated flavors and optionally a variable amount of nicotine. In a study done in 2016, 113 chemicals in 50 brands of liquids were identified. Even more compounds were observed in the aerosol because some chemicals are generated during the vaporization process. Various chemical substances and ultrafine particles are known to be toxic, carcinogenic and/or to cause respiratory and cardiac disease have been identified in e-cigarette aerosols, cartridges, refill liquids and environmental emissions. Once such chemical is propylene glycol and while this has been approved as a substance used to suspend some oral medications, does not mean it was meant to be inhaled.

It is well absorbed orally and can be absorbed through the skin or mucous membranes. After it has been absorbed the kidneys eliminate 45% of propylene glycol and the liver metabolizes the remainder into lactic acid, pyruvic acid or acetone. Clearly better studies and more research is needed to affirm the safety or detriment of e-cigarettes and/or vapes (Stratton et al, 2018).

Work Cited
Clapp, P.W. et al. (2019). Cinnamaldehyde in flavored e-cigarette liquids temporarily suppress bronchial epithelial cell ciliary motility by dysregulation of mitochondrial function. American Journal of Physiology-Lung Cellular and Molecular Physiology.

Park,H. R. et al. (2019). Common e-cigarette chemical flavorings may impair lung function. Harvard T.H. Chan School of Public Health.

Scott, A. et al. (2018). Pro-inflammatory effects of e-cigarette vapor condensate on human alveolar macrophages. Thorax,73(12).

Stevenson, M. et al. (2019). The use of genomic allergen rapid detection assays to predict the respiratory and skin sensitizing potential of e-liquids. Regulatory Toxicology and Pharmacology,103(2019).

Stratton,K. et al. (2018). Public health consequences of e-cigarettes. National Academies Press. National Academies of Science, Engineering and Medicine-Toxicology of E-cigarette Constituents

Tegin, G. et al. (2018). E-cigarette toxicity. Southern Medical Journal, 111(1).