In the past decade, e-cigarettes have emerged as a popular alternative to traditional cigarettes. E-cigarettes are widely perceived by the public as less harmful, with some health specialists even pointing to their potential value in helping people quit smoking. This idea has contributed, at least in part, to the drastic increase in the number of people vaping worldwide, up from seven million in 2011 to 41 million in 2018.

There is still a vast knowledge gap when it comes to the safety of e-cigarettes.

However, the use and safety of e-cigarettes is highly controversial. Many health specialists argue that e-cigarettes actually undermine efforts to quit smoking, as seen in the increasing vaping rates among young people who have never smoked. This controversy makes it clear that though the dangers of smoking traditional cigarettes are well-documented, there is still a vast knowledge gap when it comes to the safety of e-cigarettes.

In a study recently published in Respiratory Research, Deirdre Gilpin and her colleagues looked to close this gap by examining what happened to key lung bacteria when exposed to electronic cigarette vapour (ECV), compared to cigarette smoke extract (CSE).

Reaction of lung bacteria to ECV and CSE

The goal of the study was to determine whether exposure to ECV or CSE resulted in changes in bacterial ‘virulence,’ i.e. the bacteria’s potential to cause harm. Bacteria, particularly Haemophilus influenzaeStreptococcus pneumoniae, Staphylococcus aureus and Pseudomonas aeruginosa, have been implicated in the development of smoking- related chronic lung diseases, like Chronic Obstructive Pulmonary Disease (COPD), by either direct infection or bacteria-mediated inflammation.

ECV vs CSE lung
Researchers examined the effects of ECV and CSE on lung bacteria.
© Liliia Lysenko

In chronic infections, bacteria are often found in large aggregates, called biofilms. Biofilms represent a real challenge when attempting to rid the body of infection. Not only are they physically hard to remove, they are also more resistant to antibiotics and harder for the body’s immune system to tackle than traditional bacteria.

The researchers observed increased biofilm growth in all CSE-exposed bacteria compared to non-exposed controls, with particularly significant increases for S. pneumoniae and P. aeruginosa. Interestingly, exposure of bacteria to ECV also resulted in similar, or in the case of S.aureus, greater, levels of biofilm formation, compared to CSE-exposed bacteria. This suggests that, compared to smoking, vaping could actually make it more likely for bacteria to establish long term infections that are more difficult to fight.

However, did the bacterial exposure to ECV and CSE actually change how the lung cells responded to the infection?

Exposure to ECV and CSE significantly boosted the bacteria’s inflammatory tendencies.

Even without outside influence, the bacteria are capable of causing significant inflammation of the lung cells. However, when the bacteria were exposed to ECV and CSE, it resulted in the increased production of cell-signalling proteins called Interleukin-8 (IL-8) and Tumour Necrosis Factor alpha (TNF-α) from A549 lung cells. Both IL-8 and TNF-α function to signal an inflammatory response. In other words, the exposure to smoke and vape significantly boosted the bacteria’s inflammatory tendencies.

Looking ahead

Overall, the results of this study illustrate that, just like smoking, vaping has the potential to make already dangerous bacteria more harmful. However, the study has its limitations, as it is difficult to recreate real-life situations in the lab, like the differences in how people vape and smoke. For example, vaping requires a deeper inhalation, and people tend to vape for a longer periods of time. It could therefore be speculated that the effects observed with ECV may be greater in real life.

The evidence demonstrates that just like smoking, vaping has the potential to make already dangerous bacteria more harmful.

Even though the researchers did not examine the effect of repeated exposure of lung bacteria to vape or smoke or investigate the effect of any of the e-cigarette flavourings, this should be a point of focus for future research, especially as there are concerns about the potential toxicity of a number of common e-cig flavourings.

Unfortunately, much of what is known about the effect of e-cigarettes is based on opinion rather than evidence. Since it seems intuitive, the general public is firmly holds the belief that vaping must be less harmful than smoking. However, it is important to understand that ‘less harmful’ is not the same as ‘safe.’ The focus going forward will be to concretely establish the risks associated with vaping in order to provide policy makers with rigorous scientific evidence, and ultimately help the public make informed choices.