A new paper successfully replicates three key studies comparing the toxicity of cigarette smoke and e-cigarette vapour on lung tissues.
Its findings provide further evidence that e-cigarettes are significantly safer than cigarettes and establishes key procedures for conducting similar research in the future. Its researchers say it is the first independent study to confirm similar prior conclusions drawn from tobacco industry studies.
In the research, authors exposed human bronchial cells – the cells that form the barrier between the outside air we breathe and the internal part of the respiratory system – to cigarette smoke and aerosol from electronic nicotine delivery systems (ENDS) or e-cigarettes.
They then conducted three separate experiments that measured these cells’ responses to this exposure, paying close attention to factors such ascytokine levels (signalling proteins) which indicate cell damage. The experiments were not simply performed in one setting by a single researcher, but rather by multiple labs that were provided with training and support on how to conduct high-quality research on smoke and aerosol exposure. The researchers hope this will lead to further replicable research both independently and collaboratively in the future.
E-cig vapour causes ‘minimal damage’ to lung lining
The researchers found that e-cigarettes possess “substantially reduced toxicity” when compared with cigarette smoke. In fact, in most of the experiments conducted, e-cigarettes were shown to exert no toxicity. They also confirmed that it is mostly the volatile compounds in cigarette smoke rather than nicotine that make it dangerous to the lung epithelium, or lining of the lung.
The research provided evidence that the vapour from e-cigarettes enacts minimal, if any, damage to the lung epithelium when viewed in relation to the harm caused by cigarettes, which were shown to cause that sort of damage. Because the lung epithelium serves as a key point of defence, filtering out potentially harmful compounds, destruction to this area can increase the chances of more serious lung damage which may lead to cancer and other illnesses.
The researchers said this was an independent confirmation of studies previously conducted by the tobacco industry. The previous tobacco industry study did differ in methodology in that the original studies used diluted samples – smoke/vapour mixed with air – whereas these new experiments used undiluted samples of smoke/vapour.
They added that while this may mark a deviation from more realistic conditions, the difference is likely to represent a more extreme case and thus may increase the impact of the findings rather than jeopardise them.
They further said that research conducted in a lab under specified controlled conditions is unlikely to represent e-cigarette use in the real world as full imitation is nearly impossible under formalised study conditions. The variability in e-cigarette use among vapers alongside the complex array of variables means head-to-head evidence like this represents some of the strongest indications available on the relative safety of e-cigarettes.
Because of this, it is difficult to claim causality in vaping-related matters, which is why there has been a struggle to pinpoint a specific cause in vaping-related illnesses such as EVALI. This also relates to one of the potential missing elements from the study.
An ‘important contribution’
Researchers could have provided a more detailed exploration of what exactly is being “inhaled”. While the study notes the nicotine levels of the e-liquid used (18 mg/ml), it omits additional information on its specific components. Given the focus on the role of solvents and other additive compounds in vaping products by regulators following the outbreak of EVALI, this information might have been valuable in clarifying the safety of commercially available e-liquid for e-cigarettes.
Overall, however, the study should be judged an important contribution to current knowledge on the safety of e-cigarettes because it operated a comparison between vaping and smoking instead of vaping and air exposure. Using air as a control against which the effects of vaping can be measures is popular as air has very few potential confounders.
However as the real world parallel is simply breathing, it also is potentially misleading. A comparison between vaping and air exposure shifts the comparison from showing the relative harm of a reduced-risk product for smokers to showing the harm compared with using nothing.
Thus, the real impact of this paper, which compares vaping to smoking and establishes procedures for others to do so too, is likely to have little to do with its findings and more with how it shapes e- cigarette research going forward through the replicable methods as well as training and support developed as part of the experimental design process.
What This Means: Comparing e-cigarettes to air by itself without clear consideration of the product’s intent to be a reduced-risk product for smokers creates an impossible situation where the devices must meet an unnecessary level of safety with data that cannot be obtained.
Sadly, much of the essential e-cigarette research emerges in this silo, absent of reference to how certain findings on e-cigarettes relate to corollary harms pose by smoking. While the reasons for this pattern in the research are complex, it stems in part from the lack of good quality research that aim to fundamentally make direct comparisons to smoking.
Hopefully the procedures, methods, and networks established by this paper will gave way to a flurry of high-quality studies that compare e-cigarette and smoke exposure directly.
– Clayton Hale ECigIntelligence contributing writer