e-Cigarettes, Heated Tobacco Products Linked to Lung Damage

Despite marketing to the contrary by the tobacco industry, electronic cigarettes (e-cigarettes) and heated tobacco products (HTPs) come with significant risks, according to a new study.

A literature review by researchers in Mexico, published by the International Journal of Environmental Research and Public Health, indicated e-cigarettes and HTPs produced lung disease in ways similar to conventional cigarettes, as well as from new mechanisms particular to these devices.

“The evidence available so far is significant enough for physicians, researchers, and public health policymakers to address these devices as an emerging public health problem that needs regulation,” the researchers said.

The tobacco industry created e-cigarettes, technically known as electronic nicotine delivery systems, as an alternative for those concerned about tobacco. They consist of a mouthpiece, a refillable cartridge for heating a liquid matrix or e-liquid (with or without nicotine), a lithium battery, and a heating atomizer. The first commercially successful e-cigarette was created in 2003. In 2014, HTPs were unveiled, which heat tobacco and glycerin sticks with low temperatures (below 350°F) and absent tobacco combustion.

The World Health Organization (WHO) has stated e-cigarettes are harmful to users’ health and are a gateway for nonsmokers, especially young individuals. In 2019, the CDC reported hospitalizations resulting from an e-cigarette or vaping-associated injury. As of January 2020, 37% of these patients were aged 18 and 24 years. The WHO statement on HTP devices is the same as for e-cigarettes.

Evaluation of the studies on e-cigarettes and HTPs show they share pathways of damage and impairment with conventional cigarettes, the authors said. They also present newer damage mechanisms related to the additives, flavors, and metal nanoparticles. In particular, the devices should not be used for nicotine replacement therapy in patients with chronic obstructive pulmonary disease and asthma, because underlying immune conditions could become complicated and disease could progress as a result.

The Flavor and Extract Manufacturers Association has identified over 1000 flavorings commonly used in e-liquids that may pose a respiratory hazard due to possible volatility and irritant properties. Several studies have been conducted on the products. Most in vitro studies use immortal cell lines from different parts of the lung, the authors said, and they have identified that aliphatic aldehydes (in fruity flavors), aromatic aldehydes (in sweet and spicy flavors), and nonphenolic terpenes (in floral and citric flavors) generate more lung damage.

Studies also have found a cytotoxic effect independent of formula, brand, or nicotine presence, the authors wrote. E-liquids that are sweet, fruity, and citrus flavored generate more reactive oxygen species. The result can be pathological processes, oxidative stress, and damage of biomolecules and proinflammatory responses, the authors said, as assessed by the presence of lactic acid dehydrogenase.

Also, several lung cell lines exposed to e-cigarettes and HTPs produced increased levels of proinflammatory interleukin-8 (IL-8) and IL-16. Inhalation from the products also increases airway bacterial infection risk. Exposure to e-cigarette vapor extract was associated with increased virulence and inflammatory potential of common pathogens in respiratory infections.

Although there is clear evidence of the association between conventional cigarette smoking and lung diseases, few studies in animal models evaluate the risk, the authors said, and the study of damage in humans is even more complicated. Still, inflammation biomarkers in plasma samples of e-cigarette users had high levels of IL-6 and IL-8.

“We found that the damage produced by using these devices is involved in pathways related to pulmonary diseases,” the authors concluded, “involving mechanisms previously reported in conventional cigarettes as well as new mechanisms particular to these devices, which challenges that the tobacco industry’s claims.”

Reference

Bravo-Gutiérrez OA, Falfán-Valencia R, Ramírez-Venegas A, Sansores RH, Ponciano-Rodríguez G, Pérez-Rubio G. Lung damage caused by heated tobacco products and electronic nicotine delivery systems: a systematic review. Int J Environ Res Public Health. 2021;18(8):4079. doi:10.3390/ijerph18084079