Vaping may be just as likely to cause bronchitis and emphysema as smoking cigarettes, a study suggests.
E-cigarette vapor containing nicotine made bacteria found in the lungs to become more harmful, similar to cigarette smoke.
Researchers warn users of the devices may even be at higher risk because they take deeper and longer puffs than traditional smokers.
The three-year study compared the effect of cigarette smoke and e-cigarette vapour on levels of bugs linked to chronic obstructive pulmonary disease (COPD).
COPD is a group of lung conditions including emphysema and chronic bronchitis.
It found changes in bacteria exposed to e-cigarette vapour were similar, and in some cases more severe, than in bugs exposed to cigarette smoke.
The study adds to growing fears over the health risks of vaping after 52 people in the US have been killed by illnesses linked to the devices.
Public Health England stands by its claims they are ’95 per cent safer than traditional tobacco’ and encourages smokers to switch to vaping.
But the latest study suggests the devices are just as harmful to the lungs as tobacco smoke.
Researchers from Queen’s University Belfast grew three different samples of common lung bacteria in a laboratory.
The microorganisms were exposed to either cigarette smoke, e-cigarette vapour or nothing at all.
Harmful biofilms of began growing in the bacteria exposed to the chemicals, an effect not observed in the control. The researchers say biofilms increase the chance of persistent infections occurring.
To investigate how harmful these bugs were, the team infected larvae of the moth G. mellonella with the strains of bacteria grown in the lab.
Insects, which typically have a 10-day lifespan, infected with bacterial strains exposed to cigarette smoke or vapour died much sooner than those that were implanted with non-exposed bacteria.
Lead author Dr Deirdre Gilpin, a lecturer in material and advanced technologies for healthcare at Queen’s, said: ‘A recurring theme of this study is the similarity in the effect of exposure to cigarette smoke compared to e-cigarette vapour on how bacteria behave and how harmful they are.
‘The findings indicate that the effects of vaping on common lung pathogens may be similar to those of smoking.’
The authors caution that the study may underestimate the harmfulness of vaping, due to the differences in smoking behaviour.
Dr Gilpin added: ‘E-cigarette users take larger and longer puffs, compared to conventional cigarette users, which may increase nicotine delivery.
‘Our model may therefore underestimate the exposure of respiratory pathogens to nicotine contained in e-cigarette vapor.’
It comes amid an e-cigarette epidemic in the US which is killing more people every week.
The spate of illnesses and deaths is thought to be caused by illicit vaping products containing marijuana components.
Fears of their safety has also spread to the UK, after the first British death linked to them was reported in October.