Despite the rapid evolution and wide variety of ENDS products, the basic operation of these devices remains the same.² Typically, when a user inhales from the device, air flow is detected by a sensor. This sensor contains a microprocessor that activates a heating element or atomizer. The atomizer heats and vaporizes the e-liquid stored in the cartridge, which the user inhales. The vaporized e-liquid then cools down and condenses to form a cloud of e-liquid aerosols. The cartridge also contains the mouthpiece for the device.

The aerosols that ENDS users breathe, and non-users are exposed to second hand, may also contain metal contaminants derived from components of the heating element as well as other volatile organic compounds (VOCs), and ultrafine particles. In fact, it is often difficult for consumers to know exactly what specific chemicals ENDS products do contain. For example, e-cigarettes marketed as containing no nicotine have been found to contain nicotine upon analysis.⁵ This is concerning since nicotine is a highly addictive substance that is toxic to developing fetuses and can harm brain development, which continues past the teen years into the mid-20s.⁶ ENDS use can increase the risk of heart disease,⁷ a myriad of lung disorders and lung damage,⁸ high blood sugar (prediabetes),⁹ and has been shown to negatively impact oral health.¹⁰

When ENDS products first appeared on the market in the 1990s and early 2000s¹¹, many viewed them as a potential aid for smoking cessation. In fact, some studies have found that using e-cigarettes with nicotine can help smokers stop smoking as compared to the use of placebo e-cigarettes. However, more recent studies show that among adult smokers who try ENDS to stop smoking, most do not ultimately stop using traditional cigarettes but rather continue to use both products. Among adult e-cigarette users aged 45 years and older, about 30% were either current or former regular cigarette smokers, and only 11% had never been cigarette smokers.²