Despite mass-media coverage implying that e-cigs might directly harm the lungs, this was the principal finding of recent research at Johns Hopkins University in Baltimore, Maryland, studying the effects of e-cigarette vapour on mice.
Over two weeks, mice were exposed to vapour for 90 minutes twice a day, in quantities which the research team led by Shyam Biswai and Thomas Sussan said were similar to those received by human vapers. A modified cigarette-smoking machine “puffed” menthol and standard-flavour e-cigs from NJOY, a major manufacturer, with a nicotine concentration of 18mg/ml.
After their period of exposure to the vapour, the mice were then infected with either pneumonia bacteria or a form of the H1N1 flu virus. A control group also received the bacteria or virus without having experienced the vapour.
“Our main interest was to determine whether e-cig exposure has any impact on pulmonary immune defenses against bacteria or viruses that are commonly associated with acute exacerbations of COPD,” the researchers wrote. COPD is chronic obstructive pulmonary disease, a lung condition characterised by shortness of breath and coughing, and usually caused by tobacco smoking.
The research was therefore intended to look at the impact on pulmonary health of vaping, rather than passive or secondhand exposure to e-cigarette vapour.
They found that “e-cig exposure resulted in significant increases in pulmonary bacterial burden” and “resulted in impaired anti-bacterial defenses”, also concluding that “e-cig exposure reduces anti-viral defenses and increases virus-induced morbidity and mortality”.
In everyday language, “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 was quoted as saying. Two of the ten mice exposed to both the vapour and the flu virus died.
“Although it is possible that e-cig exposure is less harmful to the lungs than cigarette smoke, it is clear that e-cig vapor elicits a pulmonary response,” the researchers concluded. “This study raises a concern that COPD patients who switch from cigarettes to e-cigs may not observe substantial improvement in their disease progression.”
They also raised the question of whether nicotine might be implicated in their results.
“It is possible that the impaired antibacterial and antiviral responses observed in e-cig exposed mice are partially mediated by nicotine”, which “has many immunosuppressive effects, including impaired antibacterial defenses”, they observed, although they added that “other components of e-cig vapor may also contribute to altered pulmonary responses”, including propylene glycol and glycerin.
Their paper, “Exposure to electronic cigarettes impairs pulmonary anti-bacterial and anti-viral defenses in a mouse model”, is published in the online journal PLOS ONE.
What This Means: Predictably, much media coverage of this study – headlined by words like “danger” and “harmful” – has insinuated that e-cigs are inherently damaging to the lungs, whereas what the study actually showed was that they increase vulnerability to unconnected ailments. Of course that in itself is not good news for vapers either, but the Johns Hopkins findings are hardly apocalyptic.
News coverage has also repeatedly picked up on the results, mentioned almost incidentally in the paper, that “e-cigarette vapour contained free radical toxins similar to those found in cigarette smoke and air pollution”. But these were present at only 1% of their level in tobacco smoke.
It’s all rather reminiscent of the recent e-cig formaldehyde scares, which boiled down to a letter in the New England Journal of Medicine from a researcher who was heating e-liquid far beyond the levels that real vapers ever would, and an apparently outlying result from just one brand found by Naoki Kunugita at Japan’s National Institute for Public Health.
Moreover, while this doesn’t at all invalidate the Johns Hopkins results, it is worth noting that the online journal where they published comes in for some criticism for the standard of its peer review.
Our health correspondent is planning to look at e-cig scares in detail soon. For the meantime, the bottom line is that the negative influence of media coverage on consumers and policy-makers is likely to be a bigger problem for the e-cig industry than anything lurking in the vapour.
– Barnaby Page ECigIntelligence staff
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