Loose ENDs: Electronic Nicotine Delivery Systems and the FDA's Recent Enforcement Policy.

Electronic nicotine delivery systems (ENDS), including electronic cigarettes (e-cigarettes), have been commercially available since the early 2000s. Since then, their use has increased both among adults and adolescents.1 E-cigarettes consist of an electric heater that aerosolises a liquid (e-liquid), which usually contains nicotine dissolved in a liquid vehicle (propylene glycol [PG] and vegetable glycerin [VG]) and chemical flavours.2 These flavours served to mask the bitter taste of nicotine, and they also facilitate the initiation and uptake of ecigarettes by attracting youth and young adults.3 In the USA alone, there are over 1,200 different vendors and over 8,000 flavors.4 E-cigarettes have undergone a series of design evolutions and are currently sold both as tank-based devices (e.g., ‘mods’, so called because of their customisability) and as cartridge-based (JUUL-type) devices, with cartridge-based ecigarette products currently being the most popular form of e-cigarette in the USA.5,6 These products are especially popular among young adults and adolescents,7 and may facilitate nicotine addiction and dependence.8