April 15, 2015

expert reaction to paper on flavour chemicals in e-cigarettes

In a study published in the journal Tobacco Control, researchers in the USA have analysed the fluid flavourings used in e-cigarettes reporting the presence of some chemicals which are known to be irritants.

Prof. Alan Boobis, Professor of Biochemical Pharmacology, Imperial College London, said:

“This paper provides useful information on the contents of some of the chemicals present in e-liquids, about which there is currently only very limited data (there is a wealth of data on these chemicals in relation to tobacco products but there is limited data in relation to e-cigarettes). The study was based on 30 samples from two brands of products available in the USA.  It is questionable as to how representative these data are of the overall market or the situation in the UK and elsewhere in Europe. The ‘vaping’ fluid was analysed for a variety of chemicals and based on the concentrations found conclusions were made regarding potential toxicity and regulatory needs. However, users of these products will not be exposed to chemicals in the liquid as such, but to their presence in the volatilized product, when used as intended. This will impact on the nature and extent of exposure, and as a consequence the risk. Clearly, better estimates of actual in-use exposure would be of value, i.e. concentration, amount and duration of exposure.

“These studies do highlight the variation that can be found in e-cigarettes, a reflection of the largely unregulated market that currently exists. The need to limit the levels of potential toxic substances and nicotine in such products has been recognized in Europe, and the Tobacco Products Directive already makes provision for ingredient, emission, safety, quality and adverse effect notification of e-cigarettes and refill containers to relevant authorities, limiting levels of some individual flavours and limiting total levels of flavours and some chemicals with toxicological, attractive or addictive properties. However, there is concern about the proposal to list levels of specific flavour chemicals on e-cigarette products, as consumers might use such numerical descriptors as a relative risk tool.”

Prof. Tony Dayan, Emeritus Toxicologist, said:

“The work by Dr Tierney and colleagues confirms previous analyses of e-cigarette fluids in the USA showing the presence of many flavouring agents widely used in foods and sometimes in fragrances. They suggest the concentrations of at least two of the chemicals, benzaldehyde and vanillin, are sufficiently high that they might cause irritation of the respiratory system in users of e-cigarettes. They have not analysed either the vapour generated in e-cigarettes or what is actually breathed by a user so their conclusions are not based on strong evidence but only on unproven suppositions. The results do not provide a firm basis for the proposed regulatory limitation of flavouring agents in e-cigarette fluids.”

‘Flavour chemicals in electronic cigarette fluids’ by Tierney et al. published in Tobacco Control on Wednesday 15th April. 

All our previous output on this subject can be seen at this weblink: http://www.sciencemediacentre.org/tag/e-cigarettes/

Declared interests

Prof. Alan Boobis: I receive financial support in the form of a contract from the Department of Health to provide scientific advice on issues relating to tobacco products, including electronic cigarettes.   I am a member of a number of expert advisory committees that on occasion address toxicological issues related to tobacco products (e.g. Committee on Toxicity, WHO Study Group on Tobacco Product Regulation, ISO/TC126/Working Group 10: “Intense Smoking Regime”.  I have no other relevant interests.

Prof Tony Dayan: I have consulted in the past for chemical companies but have never had any professional association with the tobacco industry in any form.