The rising popularity of vaping has been dramatic, especially among teenagers. According to a 2019 study, about 37% of high school seniors reported vaping in 2018, up from 28% the year before. An estimated 2.1 million middle school and high school students reported using e-cigarettes in 2017; that number jumped to 3.6 million in 2018. A more recent survey found that among high school seniors, more than 40% had tried e-cigarettes. Certainly, age restrictions — it's illegal to sell e-cigarettes to anyone under 21 (18 or 19 in some states) — aren't preventing use among teens and young adults. And more than nine million adults 18 or older use e-cigarettes, according to a 2020 survey by the CDC.
E-cigarettes use a battery-powered device that heats a liquid to form vapors — or, more accurately, aerosol — that the user can inhale (thus "vaping"). These devices heat up various flavorings, nicotine, marijuana, or other potentially harmful substances. Nicotine is addictive, of course. And while that fact is prominently displayed in advertising, we know from experience with regular cigarettes that warnings don't always work!