Comparing the cancer potencies of emissions from vapourised nicotine products including e-cigarettes with those of tobacco smoke
Compose Response

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Author Information
First or given name, e.g. 'Peter'.
Your last, or family, name, e.g. 'MacMoody'.
Your email address, e.g.
Your role and/or occupation, e.g. 'Orthopedic Surgeon'.
Your organization or institution (if applicable), e.g. 'Royal Free Hospital'.
Statement of Competing Interests


  • Responses are moderated before posting and publication is at the absolute discretion of BMJ, however they are not peer-reviewed
  • Once published, you will not have the right to remove or edit your response. Removal or editing of responses is at BMJ's absolute discretion
  • If patients could recognise themselves, or anyone else could recognise a patient from your description, please obtain the patient's written consent to publication and send them to the editorial office before submitting your response [Patient consent forms]
  • By submitting this response you are agreeing to our full [Response terms and requirements]
Publication Date - String

Vertical Tabs

Other responses

Jump to comment:

  • Published on:
    Response to Bashash et al.

    I am grateful to Bashash et al. for raising some important methodological and policy-related issues. Responding to their specific points:

    (1) Very high formaldehyde concentrations may arise in aerosols when atomisers generate excessive heat[1]. Under these circumstances recommended safety limits for formaldehyde may indeed be exceeded and this compound contributes most to the cancer potency summation.

    (2) Goodson et al. [2] provide a framework for assessing whether low dose compounds that are not necessarily individual carcinogens may become involved in carcinogenesis when acting in concert. Although discussed under "Strengths and limitations" synergystic phenomena were not accommodated in the cancer potency model as it is not yet possible to predict the mechanism and magnitude of such interactions in tobacco or e-cigarette aerosols. Under the Goodson et al. model adverse effects reflect adventitious synergystic combinations. These may be statistically more likely in tobacco smoke where the number of different compounds greatly exceeds those of simpler aerosols, however this effect is expected to be minor compared with the exceptionally high carcinogenic potencies of some well-established carcinogens in tobacco smoke.

    (3) Lifetime cancer risk is linearly dependent on the daily volume of vapour inhaled (equation 7) and the effect on risk of increased consumption after switching to heat not burn (HnB) products is directly related to the chang...

    Show More
    Conflict of Interest:
    None declared.
  • Published on:
    Vapourised nicotine products: Lower concentration does not mean safe
    • Morteza Bashash, Assistant Professor Dalla Lana School of Public Health, University of Toronto
    • Other Contributors:
      • Michael Chaiton, Scientist
      • Robert Schwartz, Executive Director

    NOT PEER REVIEWED The results provided by Stephens [1] may suggest to readers that since the concentrations of carcinogens are lower in vapourised nicotine products (VNPs), the risks of cancer are smaller compared to conventional cigarettes. The article uses the linear non-threshold model for risk assessment (a uniform cancer risk per unit dose from higher to lower doses), which is also used by most regulatory agencies. This model is considered to have a high degree of uncertainty; nevertheless, it implies that any dose of carcinogens increases the risk of cancer. Accordingly, the primary conclusion of Stephens and other’s[2] findings of the presence of carcinogens, particularly in heat-not-burn cigarettes (HNB) is that HNB poses a significant risk of cancer. In addition:
    1) The article highlights a summation approach of overall cancer risk for each product, yet the individual concentrations of human carcinogens (for example, formaldehyde [3]) are still at risk level.
    2) The assessment of carcinogenesis of low-level exposure to a mixture of chemicals is challenging [4]. Stephens’s summation model assumes that the effect of chemicals is independent. Even if we assume that for an individual chemical a lower concentration lowers carcinogenicity, we cannot rule out the potential effects of interactions among chemicals.
    3) The analysis relies on holding consumption constant. However, manufacturer studies have suggested that consumption increases after a swi...

    Show More
    Conflict of Interest:
    None declared.