E cigarettes are independent risk factor for respiratory disease, study finds The BMJ Vaping increases risk for asthma, COPD, other lung diseases UPI.com CQ Researcher Acetal Formation of Flavoring Agents with Propylene Glycol in E Cigarettes: Impacts on Indoor Partitioning and Thirdhand Exposure Environmental Science & Technology Vaping increases the risk of lung disease by a third: U.S. study Reuters