Vaping Q&A: Johns Hopkins Expert on E Cigarettes and Tobacco Alternatives Johns Hopkins Bloomberg School of Public Health Johns Hopkins Bloomberg School of Public Health Epidemiology Department Baltimore MD PDF) Metal Concentrations in e Cigarette Liquid and Aerosol Samples: The Contribution of Metallic Coils Invited Commentary: Attendance and Absence as Markers of Health StatusThe Example of Active and Passive Cigarette Smoking