San Francisco became the first major U.S. city to ban e-cigarette sales, putting itself at the center of a public health debate amid the rise of teenage vaping — even as the industry’s leading e-cig brand sits in its backyard.

An ordinance approved Tuesday by the Board of Supervisors and expected to be signed by the mayor prohibits the sale of e-cigarettes that have not undergone premarket review by federal regulators. None have. But the measure has been criticized by e-cigarette makers — including the San Francisco-based market leader Juul Labs — and some public health officials who question whether there’s any real benefit to banning the products while cigarettes — a top killer of adults in the United States — are still widely sold.

Health officials warn that nicotine can harm the development of teenagers’ brains, including parts that control attention, learning, mood and impulse control. Last year, the federal Centers for Disease Control and Prevention reported a 78 percent increase in vaping among high school students, and 48.5 percent for middle school students. The U.S. Food and Drug Administration has sought to reduce vaping among teens, many of whom are drawn to the products for their fruity flavors and enticing advertising.

City Attorney Dennis Herrera said the measure is a step toward preventing “another generation of San Francisco children from becoming addicted to nicotine.” The ban applies to brick-and-mortar stores as well as to online purchases shipped to a San Francisco address.

It’s unclear how the ordinance will affect operations at Juul, which quickly transitioned from start-up to the most lucrative name in e-cigarettes. In December, Altria Group — which sells Marlboro cigarettes — took a 35 percent stake in Juul, which a the time was valued at $38 billion. The company expects 2019 revenue of $3.4 billion — nearly three times what it took in last year — Bloomberg reported in February.

E-cigarettes heat liquid to produce an aerosol that typically contains nicotine, flavoring and other chemicals. Though the nicotine itself is still an addictive chemical, e-cigarettes contain far fewer toxins than conventional cigarettes.

Some experts contend that e-cigs have helped reduce cigarette use in the United States. According to a study published in January by the New England Journal of Medicine, e-cigarettes are almost twice as effective at helping smokers quit as nicotine replacement therapies, such as lozenges and patches.

The study was a controversial one; an editorial published in the same publication argued that e-cigarettes should be an option only when FDA-approved treatments do not work. Another editorial called on the FDA to ban all flavored e-cigarettes.

Juul said the ban could “create a thriving black market” instead of addressing the causes of underage access and use. “This will primarily drive adult smokers back to cigarettes, which remain untouched by this legislation, even though they kill 40,000 Californians every year,” company spokesman Ted Kwong said in a statement.

Juul said the city should consider mandatory electronic scanning of IDs to verify users’ ages, as well as apply restrictions on bulk purchases to discourage unauthorized resale or product sharing. The company said it will continue to work with policymakers to enact stronger regulation around vapor products as an alternative to blanket prohibition.

Last week, after Connecticut raised the purchasing age to 21, Juul chief executive Kevin Burns said adult smokers won’t have “a true alternative to combustible cigarettes” if youth use continues unabated. “Tobacco 21 laws fight one of the largest contributors to this problem — sharing by legal-age peers — and they have been shown to dramatically reduce youth-use rates,” he said.

Earlier this month, the FDA issued its final guidance for e-cigarette makers to submit their premarket applications for tobacco products. Companies must show their products “would be appropriate for the protection of the public health.” In May, a federal judge ordered the FDA to move faster on its review of thousands of vaping products already on the market.

In March, the FDA issued a policy that seeks to limit sales of fruity and kid-enticing vaping products to stores that don’t sell to minors or that have separate adults-only sections. Online sellers would also have to tighten age verification and curb bulk sales. Companies that violate the guidelines would be punished through FDA enforcement actions, including having products taken off the market.