Cytotoxicity of E-Cigarette Liquids and Aerosols

The use of electronic nicotine dispensing systems (ENDS) – also known as e-cigarettes or vapes – has exploded in recent years. They are devices that create an aerosol by heating a liquid that contains chemicals such as nicotine, flavourings, and additives in a cartridge or tank. The resulting vapor is inhaled through the mouthpiece and the user has the sensation of smoking a conventional cigarette. E-cigarettes are sold in a variety of shapes, sizes and colours and are powered by rechargeable batteries. They are commonly used as an aid in quitting traditional cigarette smoking and the emergence of a variety of “nicotine salts” that deliver higher levels of nicotine have driven their growth in the market.

While a growing number of adults have adopted e-cigarettes, there is a large and increasing prevalence of youth use of these devices. The US Food and Drug Administration (FDA) monitors national usage rates and has seen a huge increase in youth use of e-cigarette products, particularly in those who are dual users of both tobacco and e-cigarettes. A growing body of evidence is suggesting that e-cigarette use harms lung health and increases the likelihood of contracting COVID-19.

Despite the increased popularity of these products among young people, the underlying chemical composition of e-cigarette fluids and aerosols remains unknown. In order to assess the potential cytotoxicity of these solutions, this study compared the effects of a range of commercially available e-liquids and their associated aerosols on human airway epithelial cells.

The cytotoxicity of the studied e-liquids was found to vary significantly and a number of them induced toxic effects at very low concentrations. Moreover, most of the tested concentrations were lower than those that have been shown to be cytotoxic for conventional cigarettes. The highest toxicity was observed for the e-liquids with a Freedom Smoke Menthol Arctic and Global Smoke Caramel flavouring, while Cinnamon Ceylon and Bubblegum were the least cytotoxic.

In addition, the toxicity of several of the tested solutions was influenced by the method of manufacture, the temperature at which the solution was heated and the pH. This demonstrates that many factors can affect the toxicity of these compounds and a greater understanding of the factors involved is required.

The e-cigarette industry is currently dominated by a handful of manufacturers with their own reusable and disposable devices that are sold in prefilled pods. The most popular, JUUL, was introduced in 2015 and now has the largest share of both reusable and disposable e-cigarettes. Its success has led to numerous “copycat” products that offer similar high-nicotine, nicotine salt e-liquid formulations and sleek, high-tech designs. JUUL also has the highest share of e-cigarette usage in high school students, with the most recent data indicating that it has more than doubled its market penetration from 2019 to 2020. These trends are worrying, given that some studies have suggested that young adult e-cigarette users report a lower success rate in quitting conventional cigarettes when they switch to e-cigarettes. 電子煙