New York, (IANS) A team of US researchers has found that e-cigarettes are toxic and can directly attack lung cells, weakening the immune system and boosting bacterial virulence. "The study shows that e-cigarette vapour is not benign -- at high doses it can directly kill lung cells which is frightening," said senior author Laura E. Crotty Alexander, staff physician at the Veterans Affairs San Diego Healthcare System and assistant clinical professor at University of California's (UC) San Diego School of Medicine. "We already knew that inhaling heated chemicals, including the e-liquid ingredients nicotine and propylene glycol, could not possibly be good for you. This work confirms that inhalation of e-cigarette vapour daily leads to changes in the inflammatory milieu inside the airways," Alexander added in a paper published in the Journal of Molecular Medicine.