Flavored liquids for e-cigarettes at a New York smoke shop. (Mike Segar/Reuters)

Alex M. Azar is the secretary of health and human services. Scott Gottlieb is the commissioner of the Food and Drug Administration.

The e-cigarette craze among teenagers has become an epidemic. We agree with those who believe that e-cigarettes may offer a lower-risk alternative for adult smokers who still want access to nicotine. But the continued availability of this opportunity to adults is being endangered by the e-cigarette industry’s slowness to address the dangers its products pose to teens.

The 2018 National Youth Tobacco Survey showed a nearly 80 percent increase in current e-cigarette use (meaning in the previous 30 days) by high-school-age teens over the previous year. The survey also showed a nearly 50 percent increase for middle-school-age children over the same period. The combined total reflects a surge of 1.5 million young e-cigarette users, to 3.6 million. Perhaps most disturbing, the survey revealed an almost 40 percent increase in teens using e-cigarettes on 20 or more of the past 30 days.

In earlier years, e-cigarette proponents shrugged off adolescent use, arguing that it was mostly infrequent and experimental. Well, not anymore.

Under President Trump’s leadership, the Food and Drug Administration has stepped up its efforts to combat these trends. In the past year, the FDA, with the Federal Trade Commission, issued warning letters to companies blatantly marketing their e-liquid products to resemble candy, cookies and juice boxes. The agency also took the largest coordinated enforcement action in its history, resulting in almost 1,300 warning letters and fines against brick-and-mortar and online retailers who illegally sold e-cigarettes to minors.

The FDA launched a large public education campaign, one that will expand this summer, aimed at reaching at-risk teens with the warning that nicotine can rewire the brain to crave more nicotine, particularly in adolescent brains that are still developing, as the U.S. surgeon general reported in 2014.

And last week, through the FDA, the Trump administration took new steps to limit the access and appeal of these products to children by proposing to prioritize enforcement against flavored e-cigarette products that are too easily available to young people — such as when e-cigarettes are sold without heightened age verification, whether at retail shops or online.

The country is at a crossroads when it comes to these products. Though the FDA’s leadership will change at the end of the month, the agency’s focus on the dangers to young people from e-cigarettes will carry on with the same vigor.

We see the potential for e-cigarettes to help addicted cigarette smokers successfully transition to this alternative form of nicotine delivery. We’ve heard from many e-cigarette users whose personal switching stories are compelling.

But we’ve also been confronted with epidemic levels of e-cigarette use by kids in middle school and high school. One popular brand, Juul, has even become a verb, with teens “juuling” in high-school restrooms. There’s also the reality, as the National Academies of Sciences, Engineering, and Medicine reported last year, that a young person who tries an e-cigarette is more likely to try a regular tobacco cigarette.

These products are on the market today only because the FDA exercised what is called enforcement discretion, thereby allowing them to be sold without official authorization. The agency thought the potential upside of e-cigarettes for adults merited their availability to the public before receiving the required marketing authorization. But the FDA had not accurately anticipated the upsurge in e-cigarette use by the young.

While we pursue changes to regulatory policy, we call on the industry — manufacturers and retailers — to step up with meaningful measures to reduce the access and appeal of e-cigarettes to young people.

The 2019 National Youth Tobacco Survey is now underway, and we are fearful that this epidemic may continue to grow. If the surge continues, more drastic regulatory action will be considered.

We hope that, years from now, we don’t look back at this critical point in the history of e-cigarettes as a missed public-health opportunity to help health-concerned smokers addicted to cigarettes. But regulators and public health officials have no choice but to combat the youth trends forcefully and follow available science to guide policy.

Absent a reversal in the trends of youth e-cigarette use, we envision a world where the FDA will continue to narrow the off-ramp for adults seeking a less harmful alternative to combustible cigarettes, in order to close the on-ramp that has resulted in the widespread and increasingly frequent use of e-cigarettes by teens. What happens in 2019 will go a long way to determine the future availability of these products.

Read more:

The Post’s View: Keep e-cigarettes in the hands of those who need them — but out of the hands of minors

Tom Miller: Let’s not overreact about e-cigarettes

Alex M. Azar and Scott Gottlieb: We cannot let e-cigarettes become an on-ramp for teenage addiction

Letter to the Editor: E-cigarettes aren’t a safe way to smokers quit

The Post’s View: The FDA is cracking down on e-cigarettes. This is what responsive policymaking looks like.