THURSDAY, Jan. 8, 2015 (HealthDay News) -- Vapor from electronic cigarettes may increase young people's risk of respiratory infections, whether or not it contains nicotine, a new laboratory study has found.

Lung tissue samples from deceased children appeared to suffer damage when exposed to e-cigarette vapor in the laboratory, researchers reported in a recent issue of the journal PLOS One.

The vapor triggered a strong immune response in epithelial cells, which are cells that line the inside of the lung and protect the organ from harm, said lead author Dr. Qun Wu, a lung disease researcher at National Jewish Health in Denver.

Once exposed to e-cigarette vapor, these cells also became more susceptible to infection by rhinovirus, the virus that's the predominant cause of the common cold, the researchers found.

"Epithelial cells are the first line of defense in our airways," Wu said. "They protect our bodies from anything dangerous we might inhale. Even without nicotine, this liquid can hurt your epithelial defense system and you will be more likely to get sick."

The new report comes amid a surge in the popularity of e-cigarettes, which are being promoted by manufacturers as a safer alternative to traditional tobacco cigarettes and a possible smoking-cessation aid.

Nearly 1.8 million children and teens in the United States had tried e-cigarettes by 2012, the study authors said in background information. Less than 2 percent of American adults had tried e-cigarettes in 2010, but by last year the number had topped 40 million, an increase of 620 percent.

For the study, researchers obtained respiratory system tissue from children aged 8 to 10 who had passed away and donated their organs to medical science. Researchers specifically looked for tissue from young donors because they wanted to focus on the effects of e-cigarettes on kids, Wu said.

The human cells were placed in a sterile container at one end of a machine, with an e-cigarette at the other end. The machine applied suction to the e-cigarette to simulate the act of using the device, with the vapors produced by that suction traveling through tubes to the container holding the human cells.