Many thanks for this comment which adds yet another aspect to the discussion of the issue of e-cigarettes. However, for the following reasons we believe that it does not have a major impact on the overall evaluation: First, not all consumed liquids contain nicotine. Second, the risk should be seen in relation to the known carcinogenic substances in cigarette smoke, especially when a smoker changes from conventional cigarettes to e-cigarettes. In addition, it is important to note that we have a very clear and comprehensive appreciation of the risks associated with carcinogenic hydrocarbons. This is not the case with nicotine. Data are mainly derived from experimental models; however, these findings are not supported by epidemiological data, e.g. by an increased cancer risk with nicotine replacement therapy. Modelling the effect of nicotine in humans is complicated by the fact that the expressed receptors are acetylcholine receptors of the nicotinic type and not nicotinic receptors as such; therefore particular care is required when choosing suitable control experiments.

In addition, the available data suggest that the route of application (subcutaneous versus inhalation) may play an important role with regard to adverse reactions. Furthermore, tumor induction and promotion of tumor progression have different implications on such risk, depending on predispositions. Thus the available data do not allow to draw clear conclusion with regard to extrapolation to humans.

Although we believe that primarily the long-term risks of e-cigarettes are not known, the overall risk associated with e-cigarettes – including the nicotine-related risk – should always be seen in relation to known potent carcinogenic substances and inflammation-inducing pollutants in cigarette smoke. From a clinical perspective, it is always beneficial to stop or at least reduce smoking, especially since there is no known other intervention that matches the effectiveness of this measure when it comes to the prevention of lung cancer and chronic obstructive pulmonary disease (COPD).

DOI: 10.3238/arztebl.2014.0682b

On behalf of the authors

Prof. Dr. med. Dennis Nowak

Institut und Poliklinik für Arbeits-, Sozial- und Umweltmedizin
Klinikum der Universität München


Conflict of interest statement

Prof. Nowak has received consultancy fees (Advisory Board) from Pfizer (a manufacturer of smoking cessation aids). He has received lecture fees from GSK. Prof. Nowak is a member of the Permanent Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe) of the German Research Foundation (DFG, Deutsche Forschungsgemeinschaft) and of the Scientific Advisory Board of the German Federal Institute for Risk Assessment (Wissenschaftlicher Beirat des Bundesinstituts für Risikobewertung).

PD Dr. Jörres has given lectures (on areas of pulmonology unrelated to tobacco cessation) for GSK, AstraZeneca, Boehringer, Novartis, and Mundipharma and has received reimbursement of travel expenses and fees in return. He is a member of the Executive Committee of Germany’s national COPD network, COSYCONET.

Dr. Rüther has received consultancy and lecture fees from Pfizer and Johnson & Johnson. Dr. Rüther is a member of the Tobacco Dependency S3 Guideline Committee of the Association of Scientific Medical Societies in Germany (AWMF, Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften). He is a principal investigator of commissioned clinical trials on drug-assisted smoking cessation for the pharmaceutical company Pfizer and Chairman of the German Addiction Medicine Society (DGS, Deutsche Gesellschaft für Suchtmedizin).

Nowak D, Jörres RA, Rüther T: E-cigarettes—prevention, pulmonary health, and addiction. Dtsch Arztebl Int 2014; 111: 349–55. VOLLTEXT
1.Nowak D, Jörres RA, Rüther T: E-cigarettes—prevention, pulmonary health, and addiction. Dtsch Arztebl Int 2014; 111: 349–55. VOLLTEXT