Federal Investigators Think Black Market Vaping Products, Not Legal E Cigarettes, Are to Blame for Respiratory Illnesses Citric Acid Produces Respiratory Sensitizers in E Cigarette Vapor Addressing the challenges of E cigarette safety profiling by assessment of pulmonary toxicological response in bronchial and alveolar mucosa models Scientific Reports Second hand e cigarette vapour increases risk of poor respiratory health, study finds Nursing in Practice E cigarette user found to have rare form of lung scarring typically found in metal workers European Respiratory Society warns against vaping for smoking cessation