The perception that e-cigarettes pose little health risk is so entrenched that some smokers, including those with chronic obstructive pulmonary disease (COPD), are switching from cigarettes to e-cigarettes, researchers said.
“Our findings suggest that e-cigarettes are not neutral in terms of the effects on the lungs,” said senior author Shyam Biswal, a professor in the Department of Environmental Health Sciences at the Johns Hopkins Bloomberg School of Public Health.
“We have observed that they increase the susceptibility to respiratory infections in the mouse models,” Biswal said.
For their study, researchers divided the mice into two groups: one was exposed to e-cigarette vapour in an inhalation chamber in amounts that approximated actual human e-cigarette inhalation for two weeks, while the other group was just exposed to air.
The researchers then divided each group into three subgroups. One received nasal drops containing Streptococcus pneumoniae, a bacteria responsible for pneumonia and sinusitis, among other illnesses, in humans.
A second received nasal drops of the virus Influenza A, and the third subgroup did not receive either virus or bacteria.
The mice exposed to e-cigarette vapour were significantly more likely to develop compromised immune responses to both the virus and the bacteria, which in some cases killed the mice, the researchers found.
“E-cigarette vapour alone produced mild effects on the lungs, including inflammation and protein damage,” said Thomas Sussan, 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,” Sussan said.
The researchers also determined that e-cigarette vapour contains “free radicals,” known toxins found in cigarette smoke and air pollution.
Though e-cigarette vapour contains far fewer free radicals than cigarette smoke their presence in e-cigarettes still suggests potential health risks that merit further study, the researchers said.
The findings are published in the journal PLOS ONE.
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