Video: Josh Jason on the pleasures of vaping. Pulmonologist Avrum Spira on how what we don’t know could hurt us. Public Health Professor Michael Siegel on the lesser of two evils.

With the public health community sharply divided over the potential benefit and harm of the popular device—and with conclusive scientific evidence in short supply—the World Health Organization (WHO) released a report in August 2014 that raised serious questions about the health impact of e-cigarettes and called for a ban on indoor use and sales to minors. The report expressed “grave concern” over the growing role of multinational tobacco companies, warning that they could turn e-cigarettes into a gateway for a new generation of smokers at a time when a decades-long public health campaign has successfully reduced smoking rates in the US and other developed countries.

“In theory—and how they’re marketed—e-cigarettes are a safer product because they don’t have tobacco, which has known carcinogens,” Spira says. “The question is: does safer mean safe?”

Also in August 2014, the Centers for Disease Control (CDC) reported that more than a quarter million youth who had never smoked a cigarette used e-cigarettes in 2013, three times the number of users since 2011. The Food and Drug Administration (FDA) proposed bringing e-cigarettes under its control alongside tobacco in the spring of 2014, but that proposal is enmeshed in debate and lawsuits. Dozens of states and cities across the country, including Boston, have already banned the use of e-cigarettes indoors.

At Boston University, Avrum Spira (ENG’02), a pulmonary care physician and School of Medicine professor of medicine and pathology and bioinformatics who studies genomics and lung cancer, was one of the first scientists to receive funding from the FDA to investigate the health effects of e-cigarettes. “In theory—and how they’re marketed—e-cigarettes are a safer product because they don’t have tobacco, which has known carcinogens,” Spira says. “The question is: does safer mean safe?”

Across BU’s Medical Campus from Spira, Michael Siegel, a physician and professor of community health sciences at the School of Public Health, has emerged as perhaps the country’s most high-profile public health advocate for e-cigarettes. Siegel, who is not currently researching e-cigarettes, says he believes that the device could potentially help large numbers of smokers quit, or drastically decrease, a habit that is the leading cause of preventable deaths in the US. He points out that despite all the existing smoking cessation products on the market, only a small fraction of cigarette smokers manage to quit. Only 4 to 7 percent break the habit without some nicotine replacement or medication, according to the American Cancer Society. At the same time, Siegel says, more research is needed on the health effects of e-cigarettes as well as their effectiveness in helping people quit smoking.