電子煙為非燃燒性的裝置，可製造吸入性煙霧。主要的成分含有尼古丁、丙二醇、植物甘油、調味劑及其他多種物質。電子煙的使用近年來在全球急遽上升。然而，關於此種新興電子裝置在長期使用上的安全性正熱烈探討中。橫斷面研究發現電子煙的使用的確與慢性肺部阻塞、氣喘及呼吸道症狀，具有關聯性。有研究發現使用電子煙會增加肺部的發炎，以及影響肺功能。在電子煙上市之後，個案報告陸續發表，試圖指出電子煙的使用與這些呼吸道疾病的連結。已被發表相關疾病，包含脂質性肺炎、急性嗜伊紅性肺炎、急性過敏性肺炎、瀰漫性肺泡出血、器質化肺炎、呼吸道細支氣管炎間質性肺病。在2019年，關於不明原因的肺部疾病個案系列研究被發表，電子煙的使用可能有關。由於電子煙的液體與煙霧含有許多不同的化學物質，在經過加熱效應分解以及被加熱的金屬線圈，都有機會產生更多新的物質。目前並無單一產品或單一物質，為這次肺部疾病事件的單一主因，美國疾病管制與預防中心將本疾病命名為「電子煙產品使用相關肺部傷害」(electronic cigarette or vaping product use associated lung injury, EVALI)。目前美國疾病管制與預防中心對於電子煙使用的指引為，不建議使用電子煙作為戒菸工具，且在調查結果明朗之前，呼籲全面禁止使用電子煙。且電子煙作為戒菸工具的使用，並無足夠的證據支持。醫療專業人員，需特別注意電子煙在長期使用，對於呼吸道健康可能造成的影響。

Electronic cigarettes (e-cigarettes) are non-combustible devices that generate inhalable aerosols with major ingredients including: nicotine, propylene glycol, vegetable glycine, flavors, and various other substances. The global usage of e-cigarette has risen exponentially in recent years. Long-term safety of this electronic device has remained under-studied. Only a few crosssectional population-based studies have observed links between e-cigarette with increased risk of COPD, asthma, and respiratory symptoms, while other studies have found increased pulmonary inflammation and impaired lung function related to electronic cigarette use. After the debut of electronic cigarettes in the market, several case reports were published, attempting to establish the association of electronic cigarettes and respiratory illnesses covering lipoid pneumonia, acute eosinophilic pneumonia, acute hypersensitivity pneumonitis, diffuse alveolar hemorrhage, organizing pneumonia, and respiratory bronchiolitis interstitial lung disease. Most recently, a case series published in 2019 has reported a large cluster of unknown pulmonary illnesses that may be associated with e-cigarette use. Liquids and aerosols in e-cigarettes contain a great variety of chemical constituents. Moreover, thermal decomposition and heating coils could produce new compounds in vaporizing aerosols. As noted above, no single product or material was identified as a major cause. Naming vaping lung injury EVALI (electronic cigarette or vaping product use associated lung injury), the US Centers for Diseases Control and Prevention does not recommend the use of e-cigarette for smoking cessation as there is no sufficient evidence indicating its effectiveness. Instead, CDC urges people to refrain from using e-cigarette before its health concerns are clarified through full-scale investigations. Medical professionals should be concerned about the impacts of e-cigarette on respiratory health.