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expert reaction to study comparing heat-not-burn, vaping and smoking

Reactions to a study published in ERJ Open Research which claims that heat-not-burn eCig devices can alter lung function and may not be a safer option than cigarette or cCig vaping.

Dr Ed Stephens, Senior Research Fellow, University of St Andrews, said: 

“This Research Letter to ERJ Open Research is a puzzling contribution to the debate on e-cigarette safety. It presents new data that purport to show, among other things, that emissions from e-cigarettes are about as harmful to respiratory health as smoking combustible cigarettes. E-cigarettes are certainly not harmless but the authors’ conclusion is inconsistent with most published research which indicates that vaping is significantly less hazardous than smoking.

“There is a plausible explanation for their findings, namely that the e-cigarette vapour generated for their experiments with living cells was laden with toxic carbonyls, which can easily happen when the e-cigarette device is run at moderately high power and wicking does not adequately keep up with re-supplying e-liquid to the heating coil, a phenomenon known as a “dry puff”. The sensory experience of dry puffs is so unpleasant due to high levels of formaldehyde that vapers avoid them by modifying their vaping behaviour or adjusting the settings on their devices.

“It is disappointing that the Letter contains none of the details required to assess whether the vapour to which the cells were exposed might include the toxic products of dry puffs. I suggest that the authors’ conclusions be treated with considerable caution until we have this information and it can be demonstrated that their experiments adequately represented vaping in the real world outside the lab.”

Dr Lion Shahab, Senior Lecturer in Epidemiology & Public Health at UCL, said:

“This laboratory study of human lung cells exposed to cigarette smoke, e-cigarette and heat-not-burn aerosol shows detrimental effects for a number of markers of cell function and viability, and while the results may be quite startling, there are a number of issues when it comes to the analysis and interpretation of results.

“These studies are problematic because they use isolated cells which differ greatly from actual cells in a living organism. Whether or not these results would be replicated in animal studies is therefore unclear.

“These type of studies (whether in cells or animals) also have problems for different reasons which are key when trying to make more general inferences. For instance, exposing cells to smoke or vapour continuously for 3 days, as was done here, does not reflect realistic use conditions. This also applies to the concentrations of smoke used in the experiment which is not what humans inhale. It is also difficult to interpret how the changes observed relate to actual health outcomes, as there are many steps that need to take place between changes at cellular level and disease development.

“The claim that e-cigarettes (and heat-not-burn devices) are as toxic as cigarettes was not, in fact, tested in the analysis and is misleading. Not only was cigarette smoke applied to cells at concentrations below the levels inhaled by smokers (because, as acknowledged by the authors, cigarette smoke is so toxic), but also no direct comparison was made between functioning of cells exposed to the same concentration of cigarette smoke and e-cigarette or heat-not-burn vapour. The comparisons were only made with untreated control cells.

“While results from this study confirm detrimental changes in the functioning of isolated cells after exposure to vapour and cigarette smoke, it is far from clear that the effect of vapour is similar to that of cigarette smoke as seen in humans and whether these changes have meaningful health consequences. Further studies, using animal models and realistic conditions in addition to monitoring of actual health outcomes in users of these devices, are needed to evaluate the potential harm of e-cigarettes and heat-not-burn products for lung health.

‘IQOS exposure impairs human airway cell homeostasis: direct comparison with traditional cigarette and e-cigarette’ by SS Sohal et al. was published in ERJ Open Research at 00:01 hrs UK time Monday 11 February 2019.

Declared interests

Dr Stephens: I have no conflicts of interest or any connection with the tobacco or e-cigarette industries, nor indeed with any commercial interest.

Dr Shahab is a HEFCE funded member of staff at University College London. He has received honoraria for talks, an unrestricted research grant and travel expenses to attend meetings and workshops from Pfizer and an honorarium to sit on advisory panel from Johnson&Johnson, both pharmaceutical companies that make smoking cessation products. He has acted as paid reviewer for grant awarding bodies and as a paid consultant for health care companies. Other research has been funded by the government, a community-interested company (National Centre for Smoking Cessation) and charitable sources. He has never received personal fees or research funding of any kind from alcohol, electronic cigarette or tobacco companies.

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