Study: E-Cigarettes Impair Pulmonary Immune System

Despite the increasing popularity of e-cigarettes and the growing perception that they are a safe alternative to traditional cigarettes, researchers have now found that they produce some of the same potentially dangerous chemicals as nicotine cigarettes and also compromise the immune system of the lungs.

“Chronic exposure to e-cigarettes is not neutral in terms of their effect on the lungs in an experimental mouse model,” say senior author Shyam Biswal, PhD, a professor in the Department of Environmental Health Sciences at the Bloomberg School, and lead author Thomas Sussan, PhD, assistant scientist in the same department. “We found that exposure to e-cigarettes compromises the lung defenses against bacteria and virus in the mice.”

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“Furthermore, we found free radicals in the e-cigarette vapors, which are also a concern for lung health,” they say. Each puff of cigarette smoke contains 1,014 free radicals, highly reactive agents that can damage DNA or other molecules within cells, resulting in cell death. While the researchers found e-cigarette vapor contains only about 1% as many, their presence is still a concern.

The findings appear in a recent issue of the journal PLOS ONE.

Biswal, Sussan, and colleagues studied two groups of mice—a control group exposed only to air and an experimental group exposed to e-cigarette vapor in an inhalation chamber in amounts similar to actual human e-cigarette inhalation for 2 weeks.

Each group was divided into three subgroups:

• One received nasal drops containing Streptococcus pneumoniae.

• A second received nasal drops of the virus Influenza A.

• The third did not receive either virus or bacteria.

Repeated exposure to e-cigarette vapor for 2 weeks had a significant impact on the immune systems of the mice, leading to enhanced susceptibility to respiratory infections. This group was significantly more likely to develop compromised immune responses to both the virus and the bacteria, which killed the mice in some cases.

These experiments have not yet been validated in human e-cigarette users so the researchers are planning to follow e-cigarette users to assess their susceptibility to respiratory infection.

They emphasize that more studies are needed to determine any deleterious effects and health risks in users. “E-cigarettes are very diverse in chemical composition, shape, size, etc, and it will be important for science to keep pace with the evolving and expanding market,” Biswal and Sussan say.  

They also suggest that future studies will need to determine if there are risks due to chronic e-cigarette use, especially in light of the many toxicants that have been detected in e-cigs.

“There is a tremendous need to investigate the effects of chronic exposures and examine other potential effects of e-cigarette exposure,” Biswal and Sussan say. “We will continue our research in experimental models, and we will also follow e-cigarette users to validate these experimental findings.”

­­—Colleen Mullarkey


Sussan TE, Gajghate S, Thimmulappa RK, Ma J, Kim J, Sudini K, et al. Exposure to electronic cigarettes impairs pulmonary anti-bacterial and anti-viral defenses in a mouse model. PLOS One. 4 February 2015. [Epub ahead of print].