E‐cigarettes need to be tested for safety under realistic conditions

In our view, Pankow et al. have not addressed adequately the key criticism of their report: that they used results from laboratory tests of e-cigarettes under conditions that rarely occur in practice to calculate a human cancer risk. Pankow et al. did not counter the point that their experiment created the well-recognized, and very unpleasant, ‘dry puff’ phenomenon, when the power input and atomizer combination causes high temperatures that create a very unpleasant taste so that users avoid this combination 1-3. Farsalinos et al. 4 have confirmed that aldehydes are contained in the aerosol at high levels only under these ‘dry-puff’ conditions. The point is that users limit their exposure to dry puff conditions by adjusting the power input, puff depth and frequency and liquid flow to ensure that they avoid this unpleasant experience, whatever the combination of battery and atomizer used. An experiment that overlooks this human control feedback cannot provide reliable data on human exposures. Pankow et al. argue that flavours would mask the acrid taste of the dry puff; but this is speculation, and contradicted by the fact that the phenomenon is reported by e-cigarette users who are using flavoured e-liquid. Moreover, flavours in e-cigarettes are not added to mask any harsh and unpleasant taste but because flavourless e-liquids are bland and boring. The authors’ conclusions, together with a press release from the New England Journal of Medicine, predictably created a misleading impression of the harmfulness of e-cigarettes. For the future, we recommend that tests of the safety of e-cigarettes in laboratory conditions be accompanied by user tests to assess how likely it is that those conditions would arise in practice, and that researchers exercise appropriate caution when generalizing their findings. K.F. reports that some of his studies on electronic cigarettes were performed with unrestricted funds provided to the Onassis Cardiac Surgery Center by FlavourArt and Nobacco. K.F. publishes a blog commenting on research on e-cigarettes and its implications at www.ecigarette-research.org/. C.B. is a long-standing and continuing advocate of ‘harm reduction’ in tobacco and other public health policies and has written extensively on e-cigarettes at www.clivebates.com.