U.S. e cigarette use stalls as health concerns grow: Reuters Ipsos poll Reuters E cigarettes more effective than patches, gum at helping people quit smoking, study finds MinnPost San Francisco becomes first US city to ban e cigarettes Transport and Mitigation of Exhaled Electronic Cigarette Aerosols in a Multizone Indoor Environment Aerosol and Air Quality Research Cancer causing Chemical Formed in E cigarette Users School of Public Health University of Minnesota Environmental impact of cigarettes Wikipedia