PHE is obliged to challenge false risk perceptions created by poor science and sensationalist communication
The rapid response from Strongin, Peyton and Pankow of Portland State University  adds a note of irony and pathos to this discussion. Public Health England and many others have been increasingly concerned that public perceptions of the relative risk of smoking and vaping are wildly out of line with the best available evidence. There is now a great deal showing vaping to be much less risky than smoking . If smokers believe that switching to vaping offers little or no risk reduction, then they may prefer to stay with the devil they know, or even to relapse back to it. But how do smokers acquire the perception that there is little or no reduction in risk? One likely explanation is the work of scientists like Strongin and colleagues, who published a research letter summarising measurements of formaldehyde hemiacetal emissions from e-cigarettes  claiming that:
"...long-term vaping is associated with an incremental lifetime cancer risk of 4.2×10−3. This risk is 5 times as high (...), or even 15 times as high (...) as the risk associated with long-term smoking".
Unsurprisingly this claim of elevated cancer-risk created a world-wide media storm and will have implanted the idea that e-cigarette use can have serious cancer risks - possibly more so than smoking. The only trouble is that the measurements were made in completely unrealistic conditions that no human subject would experience for more than an unpleasant instant, let alone the whole lifetime on which these cancer risk calculations were based. I and others have detailed the failings in this methodology and called for the paper to be retracted , making criticisms to which the authors have been unable to respond. Strongin et al’s swipe at Farsalinos et al (their reference 3) suggests they still have not assimilated the lessons of this episode. However, the damage is done, the media storm has blown through and public perceptions have been adversely altered to be further from the underlying reality. The Portland study is merely the worst of many examples of studies with flawed methodologies or misleading presentation of risk that have entered the public consciousness, originating in universities hungry for publicity and grants and then popularised and embellished in the news media hungry for sensation and internet clicks.
A responsible public health agency like Public Health England is professionally obliged to provide a counterweight to this malign dynamic. Its aim should be to ensure that public perceptions of risk and uncertainty are as closely aligned as possible to the what the science is really showing and what genuine experts assess the risks to be. In this way, it respectfully assists the public in making informed choices about their risky behaviours. This is exactly what they have done in commissioning two leading scientists in the field to provide an evidence assessment and by communicating that vaping is likely to be about 95% lower risk than smoking. If there is a legitimate criticism of the PHE’s risk communication, it is that it probably overstates the residual risks and includes a large margin for unknown future effects. Based on what is known of vapour constituents compared to cigarette smoke, it is likely that vaping is at least 95% safer than smoking and it is possible that it will have no mortal risks at all. So PHE is taking both a cautious and responsible approach, and not leaving it to the public to form their perceptions from media spin and hype.
Strongin et al incorrectly suggest that I might be in “fear of regulation" (their reference 4). I am opposed to excessive regulation or regulating these products as medicines. The simple reason for this is that piling pointless costs, burdens and restrictions onto the vaping industry simply creates regulatory barriers that protect the cigarette trade and keep smokers smoking, while shaping the regulatory regime for nicotine products to suit the business model of Big Tobacco to the exclusion of everyone else. I favour moderate regulation that improves health and safety, builds consumer confidence and removes any rogue traders or products from the market. I fear that many well-meaning public health activists do not really understand how regulation and markets interact, and that getting tough on harm reduction is little different to promoting harm.
 Strongin R, Peyton D, Pankow J. Harm Reduction is Not Well-Served by Bias, Rapid Response BMJ 2015;351:h4863 http://www.bmj.com/content/351/bmj.h4863/rr-18
 Burstyn I. Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks. BMC Public Health 2014;14:18. doi:10.1186/1471-2458-14-18 http://www.biomedcentral.com/1471-2458/14/18
 Farsalinos KE, Polosa R. Safety evaluation and risk assessment of electronic cigarettes as tobacco cigarette substitutes: a systematic review. Ther Adv Drug Saf 2014;5:67–86. doi:10.1177/2042098614524430 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4110871/
 Jensen RP, Luo W, Pankow JF, et al. Hidden formaldehyde in e-cigarette aerosols. N Engl J Med 2015;372:392–4. doi:10.1056/NEJMc1413069 http://www.nejm.org/doi/full/10.1056/NEJMc1413069
 Bates CD, Farsalinos KE. Research letter on e-cigarette cancer risk was so misleading it should be retracted. Addiction 2015;110:1686–7. doi:10.1111/add.13018 http://onlinelibrary.wiley.com/doi/10.1111/add.13018/full
Competing interests: Non-financial: Clive Bates is a long-standing advocate of ‘tobacco harm reduction’ as a public health strategy and has written extensively on e-cigarettes at www.clivebates.com. He was Director of the UK campaigning charity Action on Smoking and Health from 1997-2003. He receives no funding from tobacco, e-cigarette or pharmaceutical industries.