Smouldering ashes: burning questions after the outbreak of electronic cigarette or vaping-associated lung injury (EVALI).

In the summer of 2019, the Center for Disease Control and Prevention (CDC) declared an emergency of electronic cigarettes and/or vaping (vaping)-associated lung injury (EVALI) in the USA. The outbreak abated by January 2020, which the CDC attributed to heightened public awareness, 'user actions to reduce risk' and potentially the removal of vitamin E acetate (VEA) from vaping products (VEA is an oily chemical cutting agent, strongly associated with the disease). Even though the EVALI outbreak appears to be over, numerous epidemiological and medical questions are left still open. First, why were there practically no cases outside the USA, which represents nearly a quarter of the global vaping market? Comparative studies to map the differences in device/fluids/user habits between countries might be needed urgently. Second, what is the pathomechanism that sickens vapers irrespective of VEA exposure? VEA was only confirmed in about half of the cases and the presumed toxicity is yet to be determined. Aetiology/epidemiology focused research is needed to investigate/interpret the broader context to explain the outbreak. Third, could any socioeconomic/environmental factors have influenced the course of the outbreak? Finally, what should we expect in the years to come? Was EVALI a serious but reversible emergency medicine condition or is vaping as detrimental to long-term health as smoking? Besides the complex legislative, regulatory, ethical aspects of EVALI, biomedical research is also difficult: in-vitro experiments have limited inferential value to real real-life vaping due to its complexity; user habits are self-reported and under-researched; there is an active black market pouring unknown quality counterfeit products and, in the USA, federal restrictions limit cannabis research. Vaping is a toxicological, multidimensional conundrum; therefore, stringent quality control, transparent legal/ethical boundaries, meticulous international research and user education are paramount to prevent potential future outbreaks and determine the parameters safe vaping (if these exist).