Vapour from the devices directly kills airway cells, boosts superbug bacteria and weakens the immune system, researchers found E-cigarette vapour makes users more vulnerable to superbugs , a new study claims.The substance directly kills airway cells and weakens the immune system, researchers found.When inhaled regularly, it also causes inflammation of the body while boosting bacterial virulence.The study, which used mice exposed to e-cigarette vapor, was published in the Journal of Molecular Medicine.Campaigners estimate that 2.6 million adults in Britain use e-cigarettes - often in a bid to try to cut down on smoking . That figure is roughly equivalent to 17.6 per cent of all smokers.But the study shows vaping it is 'not benign' and can 'directly kill lung cells'.Inflammatory markers in the mice - who inhaled the vapour for an hour a day, five days a week for four weeks - were elevated 10 per cent compared to unexposed mice.Doctor Laura Crotty Alexander, staff physician at the Veterans Affairs San Diego Healthcare System in the US, said: "This study shows that e-cigarette vapour is not benign - at high doses it can directly kill lung cells, which is frightening."We already knew that inhaling heated chemicals, including the e-liquid ingredients nicotine and propylene glycol, couldn't possibly be good for you.Read more: Cervical cancer survivor feared her partner would leave her when the disease left her infertile - but he proposed instead"This work confirms that inhalation of e-cigarette vapor daily leads to changes in the inflammatory milieu inside the airways."She added: "We don't know specifically which lung and systemic diseases will be caused by the inflammatory changes induced by e-cigarette vapour inhalation, but based on clinical reports of acute toxicities and what we have found in the lab, we believe that they will cause disease in the end."Some of the changes we have found in mice are also found in the airways and blood of conventional cigarette smokers, while others are found in humans with cancer or inflammatory lung diseases."Meanwhile, bacterial pathogens exposed to e-cigarette vapour benefited.Staphylococcus aureus bacteria were better able to form biofilms, adhere to and invade airway cells and resist human antimicrobial peptides after exposure to.The results were consistent with e-liquids from seven different manufacturers, demonstrating that the findings are not limited to one formula or brand.