E-cigarettes may open lungs to the flu

"E-cigarette vapor alone produced mild effects on the lungs, including inflammation and protein damage," says Thomas Sussan. "However, when this exposure was followed by a bacterial or viral infection, the harmful effects of e-cigarette exposure became even more pronounced." (Credit: iStockphoto)

A study with mice suggests vapor from e-cigarettes can compromise the immune system in the lungs, leaving them more vulnerable to potentially dangerous infections like pneumonia and the flu.

E-cigarettes also generate some of the dangerous “free radicals” found in traditional tobacco cigarettes, the study shows.

“Our findings suggest that e-cigarettes are not neutral in terms of the effects on the lungs,” says senior author Shyam Biswal, professor of environmental health sciences at Johns Hopkins University Bloomberg School of Public Health.

(Credit: Vladimir Agafonkin/Flickr)

‘Vaping’ and COPD

“We have observed that they increase the susceptibility to respiratory infections in the mouse models. This warrants further study in susceptible individuals, such as COPD patients who have switched from cigarettes to e-cigarettes.”

E-cigarettes are emerging as a public health concern as “vaping” gains popularity among current and former smokers and those who have never smoked, including teens. The perception that e-cigarettes pose little health risk causes some smokers, even some with COPD, or chronic obstructive pulmonary disease, to switch to e-cigarettes.

In the study, published online by the journal PLOS ONE, Biswal and colleagues exposed mice to e-cigarette vapor for two weeks in amounts that approximated actual human e-cigarette inhalation. Other mice were exposed only to normal air.

The researchers then divided each set of mice into three subgroups. One received nasal drops containing Streptococcus pneumoniae, a bacterium responsible for human pneumonia and sinusitis, among other illnesses. A second received drops of the virus Influenza A. The third subgroup received neither.

E-cigarette risks

Mice exposed to e-cigarette vapor were significantly more likely to develop compromised immune responses to both the virus and the bacteria, which in some cases killed the mice.

“E-cigarette vapor alone produced mild effects on the lungs, including inflammation and protein damage,” says Thomas Sussan, lead author and an assistant scientist in the environmental health sciences department. “However, when this exposure was followed by a bacterial or viral infection, the harmful effects of e-cigarette exposure became even more pronounced.

“The e-cigarette exposure inhibited the ability of mice to clear the bacteria from their lungs, and the viral infection led to increased weight loss and death indicative of an impaired immune response.”

The researchers believe their study, thought to be the first to examine animal response to e-cigarette inhalation, will serve as a model for future work.

Since their introduction in the United States in 2007, e-cigarettes have prompted debate over the risk they pose. The devices, which at their simplest consist of a battery, an atomizer, and a cartridge, produce a vapor that the user inhales and then exhales.

E-cigarettes contain less additive nicotine than tobacco cigarettes, but actual nicotine intake by e-cigarette users can approximate that of tobacco smokers.


Previous analyses of e-cigarette vapor have identified chemicals that could be toxic or carcinogenic, including particulates, formaldehyde, and volatile organic compounds, but at lower levels than cigarette smoke. E-cigarettes don’t burn as cigarettes do, limiting delivery of some chemicals released in cigarette smoke.

E-cigarette vapor also contains “free radicals,” known toxins found in cigarette smoke and air pollution. Free radicals can damage DNA or other molecules, killing cells. Though e-cigarette vapor contains far fewer free radicals than cigarette smoke—1 percent as much—their presence suggests potential health risks that merit further study, the researchers say.

“We were surprised by how high that number was, considering that e-cigarettes do not produce combustion products,” Sussan says. “Granted, it’s 100 times lower than cigarette smoke, but it’s still a high number of free radicals that can potentially damage cells.”

The US Food and Drug Administration last spring announced that it will regulate e-cigarettes, which are projected to overtake cigarettes in sales in the next decade. Teen use of e-cigarettes outpaces cigarette use, according to a recent survey. According to the US Centers for Disease Control and Prevention, more than a quarter-million teenagers who don’t smoke tobacco reported using e-cigarettes in 2013.

The Flight Attendant Medical Research Institute and the National Cancer Institute funded the research.

Source: Johns Hopkins University