Over the past five years, the e-cigarette market has grown from nearly zero to over $1.7 billion in sales, driven in no small part by the perception that e-cigs are a safer alternative to tobacco. That perception, however, took a serious blow in 2015 as a result of new research from scientists at the Johns Hopkins Bloomberg School of Public Health.
In a study that involved exposing mice to e-cigarette “vapor” at levels approximating what a human would inhale over a two-week period, researchers from the Department of Environmental Health Sciences discovered that the mice exposed to e-cigarette vapor were significantly more likely to develop compromised immune systems which made them more susceptible to both bacterial and viral infections.
“Our findings suggest that e-cigarettes are not neutral in terms of the effects on the lungs.”
Shyam Biswal, PhD, MS, Professor, Department of Environmental Health Sciences
Johns Hopkins Bloomberg School of Public Health
“Our findings suggest that e-cigarettes are not neutral in terms of the effects on the lungs,” notes senior author Shyam Biswal, PhD, MS, a professor in the Department of Environmental Health Sciences at the Bloomberg School. “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 disorder) patients who have switched from cigarettes to e-cigarettes or to new users of e-cigarettes who may have never used cigarettes.”
The research team believes that one of the potential reasons for the immunosuppressive effect of e-cigarette vapor is that mice exposed to it developed lung damage which limited their ability to clear pathogens from their lungs.
“E-cigarette vapor alone produced mild effects on the lungs, including inflammation and protein damage,” says Thomas Sussan, PhD, lead author and an assistant scientist in the Department of Environmental Health Sciences at the Bloomberg School. “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.”
Researchers were also surprised to discover that e-cigarette vapor contains free radicals, highly reactive atoms and molecules that can damage cells and the DNA inside the cells, killing the cell or, in some cases, causing it to become cancerous. Though e-cigarette vapor contains only one percent as many free radicals as cigarette smoke does, the finding was a surprise, as the mechanism producing them in e-cigarettes is currently unknown. Because free radicals in cigarettes are created as part of the burning process, researchers were troubled that any free radicals were found in e-cigarette vapor.
“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 study was published in February 2015 in the journal PLOS ONE, a multidisciplinary online journal.