Ed Stephens is Senior Research Fellow in the School of Earth & Environmental Sciences at the University of St Andrews (Scotland, UK). He has held visiting positions in France (Toulouse) and Australia (ANU). His training is in geochemistry with a current interest in modelling environmental pathways of toxicants and carcinogens. This began with modelling the controls on valence speciation of metals in tobacco and more recently has focused on chemical aspects of emissions in e-cigarettes and other forms of nicotine delivery. His research has been supported by UK research councils, NIH, EU and medical charities.