Electronic cigarettes have boomed into a $2 billion per year industry since 2007, with claims that they are a safer alternative to traditional smoking. That may be so, in the same way that getting hit in the head with a baseball bat is safer than getting thrown off of a building, but it doesn’t mean that e-cigs are inherently safe. In fact, a new paper published in PLOS ONE by lead author Thomas Sussan from Johns Hopkins Bloomberg School of Public Health has found that mice who were exposed to e-cig vapor had weaker immune systems than those who did not.

"Our findings suggest that e-cigarettes are not neutral in terms of the effects on the lungs,” senior author Shyam Biswal said in a press release. "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 [chronic obstructive pulmonary disease] patients who have switched from cigarettes to e-cigarettes or to new users of e-cigarettes who may have never used cigarettes.”

The study sorted mice into two groups: one was exposed to vapor from Njoy electronic cigarettes for two weeks, and the other breathed only fresh air. The mice didn’t only breathe vapor for two weeks; the exposure was adjusted to mimic the dose that a human would receive by vaping during that timespan. Next, subgroups were created within the vapor and fresh air groups. The first group was exposed to Influenza A, the next was exposed to the pneumonia-causing bacteria Streptococcus pneumoniae, and the third group was not given any illness-causing microbes.

The mice that had been exposed to e-cig vapor had infections that were much more severe than their fresh air-breathing counterparts, indicating a weakened immune response. For some of the mice, these infections were lethal. Further investigation into the mice revealed physiological changes that had occurred in the models.

"E-cigarette vapor alone produced mild effects on the lungs, including inflammation and protein damage," Sussan explained. "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.”

Traditional cigarette smoke contains over 400 toxins, over 60 of which are known carcinogens. Instead of burning tobacco and inhaling toxins through smoke like ordinary cigarettes, an electronic cigarette produces a nicotine aerosol vapor for users to inhale. Though the lack of burning prevents some chemicals from being released, there are still a number of free radicals introduced into the body that can alter DNA and have cancer-causing effects.

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

More study is needed on this subject to fully understand the effect of e-cigarettes on the body, and how it could contribute to disease. E-cigarettes really hit the market about seven years ago, and quickly fell into favor with former smokers of tobacco cigarettes. In 2013, it was reported that more teenagers had tried e-cigarettes than had tried traditional cigarettes, which makes it incredibly important to know what the real risks to these kids will be.

Image: Jonny Williams via flickr, www.ecigclick.co.uk CC BY-SA 2.0