Also this week, on Friday, the agency’s new nicotine steering committee will hold a public hearing on over-the-counter therapeutic products, among them gums, patches and lozenges, designed to help smokers quit.

[READ: The health effects of e-cigarettes]

Cessation was one area where the committee’s report did give the booming e-cigarette industry some good news. It pointed out the benefits for smokers trying to quit. But people who continue to smoke cigarettes, alternating with e-cigarettes, do not gain the same health benefits, the committee said. That’s especially important given that most adults who vape also still smoke or use other tobacco products. The report also said the evidence was limited on whether e-cigarettes were effective for quitting smoking.

While there is no evidence at this time that e-cigarettes or their components cause cancer, the committee recommended more long-term research. Some e-cigarettes contain chemicals and metals whose long-term effects — including on pregnancy — also need further study, the committee said.

Smoking rates among adults and teenagers have declined significantly over the last few decades. In 2015, the last year for which the Centers for Disease Control and Prevention has statistics, about 37 million Americans, 15 percent of adults aged 18 and older, smoked cigarettes. The number has declined from nearly 21 percent of every 100 adults in 2005; and 42 percent in 1965.

With that decline, the e-cigarette industry has emerged as a potential substitute and Big Tobacco has been among the device developers enjoying new profits from the tobacco alternatives. Bonnie Herzog, a Wells Fargo tobacco analyst, predicted the industry will grow about 15 percent to $5.1 billion in retail sales in the United States, in 2018.

The vaping industry, as well as traditional tobacco companies, are gearing up for a lengthy fight with the F.D.A. over the campaign by the agency’s commissioner, Dr. Scott Gottlieb, to slash levels of nicotine in traditional cigarettes to nonaddictive or minimally addictive levels.

Dr. Gottlieb is expected to issue an initial proposal, calling for public comment on lower nicotine levels, in the near future.