Cigarettes are a public health nightmare: both highly addictive and highly dangerous. By the middle of the 20th century, nearly half of Americans were smokers, putting themselves at risk of lung cancer, emphysema, and other chronic and deadly health problems. And while smoking rates have fallen significantly over the decades, 29 million people in the US continue to light up because once you start, it can be hard to stop.

Despite decades of aggressive anti-smoking measures, the toll from tobacco continues. Each year, approximately 225,000 people in the US are diagnosed with lung cancer (for which smoking remains the primary risk factor), while 125,000 Americans die from the disease. Add the deaths from heart disease and the other negative effects of regularly inhaling smoke, and the number of annual deaths related to smoking climbs to nearly 500,000, making it the leading cause of preventable death in the US.

This public health crisis is precisely the problem that e-cigarettes were designed to address: delivering nicotine to people with a dependency on it, minus the dangerous chemicals produced by regular cigarettes.

It’s been more than 20 years since their invention, and in that time e-cigarettes do appear to have had real public health benefits for smokers. At the population level, lung cancer rates have declined by about 20 percent over the past five years. While most of that progress is likely attributable to the continued drop in combustible smoking, most experts believe that e-cigarettes are helping pull that number downward. One 2016 projection estimated that by 2100, vaping could reduce deaths from tobacco use by as much as 25 percent compared to what might have happened in the absence of e-cigarettes.

Public health experts have no doubt that e-cigarettes pose less of a health risk than smoking tobacco, so for the millions of smokers who want to quit but struggle against the pull of nicotine, e-cigarettes could be a literal lifesaver. But at the same time, it is increasingly clear that they present a new kind of health risk to the people who have never picked up a pack of Camels — and might never have had e-cigarettes not been introduced.

That’s most obvious among young people who grew up in the years when smoking was sharply declining. By 2019, even as overall smoking rates had fallen to 14 percent, nearly one in three high schoolers said that they had vaped nicotine in the past 30 days. And notably, the percentage of US high school students who were vaping in 2019 was higher than the combined percentage of teens just five years earlier who had used any tobacco product. That means that the rapid rise of vaping almost certainly led to more young people consuming nicotine overall.

Today, fewer than 2 percent of teens smoke traditional cigarettes or cigars, according to the Centers for Disease Control and Prevention, the lowest levels ever recorded. But four times as many vape. The CDC recently reported 15 percent of adults ages 21 to 24 in the US — the generation who came of age during the e-cigarette boom — still use e-cigarettes, as do 10 percent of those ages 18 to 20, while only 5 percent of adults ages 18 to 24 smoke regular cigarettes.

Tobacco companies contributed to and profited from that surge. Juul, the brand most associated with the e-cig craze, was valued at nearly $40 billion in 2018 when the United States’ largest tobacco company, Altria, bought a stake in it. Juul would later pay a billion-dollar settlement for specifically targeting teens — even buying space on youth-based websites — with ads that featured young people vaping.

Before vaping took off, traditional cigarette smoking was already declining; fewer than 20 percent of

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