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expert reaction to study on ecig vapour and cancer in mice

Research, published in PNAS, reports that e-cigarette vapour may be carcinogenic in the lungs of mice. 

A Before the Headlines accompanies this Roundup of comments.  


Prof John Britton, Director of the UK Centre for Tobacco & Alcohol Studies and Consultant in Respiratory Medicine, University of Nottingham, said:

“This study explores the effect of exposure to nicotine ecig vapour on mice. It shows that exposure to ecig vapour with nicotine causes more cancers than fresh air, but no more than you might reasonably expect by chance.

“It also shows that e-cig vapour without nicotine causes fewer cancers than fresh air.

“The findings are based on very small numbers and need to be interpreted with extreme caution.

“The comparison between mice breathing vapour and mice breathing air is not statistically significant.  There is no sample size justification and no power calculation.  There is no message to the public here – I suspect these results are just noise.”


Prof Peter Hajek, Director of the Tobacco Dependence Research Unit, Queen Mary University of London (QMUL), said:

“The study has unclear relevance for human vapers.

“Rodents were exposed to what are for them huge concentrations of chemicals that bear no resemblance to human exposure from vaping. Several animals in fact died during these exposures.

“The authors assigned the effects they observed to a carcinogen NNK – but NNK has been measured before in human vapers, and it is known that exposure from vaping is either negligible or none.”


‘Electronic-cigarette smoke induces lung adenocarcinoma and bladder urothelial hyperplasia in mice’ by v et al. was published in PNAS at 8pm UK time on Monday 7 October. 

DOI: 10.1073/pnas.1911321116


Declared interests

None to declare. 

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