How close are we to definitively identifying the respiratory health effects of e-cigarettes?

Introduction: Use of electronic cigarettes (e-cigarettes) is frequently promoted as a less harmful alternative to cigarette smoking. The impact of repeated inhalation of e-cigarette aerosols on respiratory health is not well understood.Areas covered: Using results from laboratory, observational, and clinical studies, we synthesize evidence relevant to potential respiratory health effects that may result from inhalation of e-cigarette...