E-cigarettes are now a multi-billion dollar industry as smokers around the world give up tobacco to vape. Some of the most popular e-cigarette brands are owned by Big Tobacco. Dr Tanusree Jain is Assistant Professor of Ethical Business at Trinity College Dublin. She's conducted a global survey of e-cigarette users, looking at what and why they vape. She says global regulation of the e-cigarette industry is almost inevitable.