Top 5 favorite pro vaping pro harm reduction studies. There are tens of thousands of them, but there are my five favorite most compelling studies done on the topic of nicotine vaping for tobacco COPD Patients Who Switch From Smoking to Vaping See Long Term Benefits Frontiers More to Explore: Further Definition of Risk Factors for COPD Differential Gender Difference, Modest Elevation in PM2.5, and e Cigarette Use Secondhand Exposure to E Cigarettes Puts COPD Patients At Risk Respiratory Therapy Comparative study of lung toxicity of E cigarette ingredients to investigate E cigarette or vaping product associated lung injury ScienceDirect